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draft user manual jci 504 lightning warning system

1. BGI CGA BGI l EGAVGA BGI HERC BGI IBM8514 BGI PC3270 BGI TRIP CHR l BACKBUFF 00000000 CH1 00003071 CHS LOGSTART TXT JCI 504 Lightning Warning System User Manual DRAFT JCI 504 Lightning Warning System Annex 4 JCI 501 and JCI 504 User files User files can be changed by the user using the EDIT text editor within MSDOS The files reside in the resource subdirectory of the program directory Here is the typical output from the dos dir command issued from within that directory Volume in drive C is MS DOS 6 Volume Serial Number is 22D8 974E Directory of C JCI501 RESOURCE lt DIR gt 25 02 98 12 18 lt DIR gt 25 02 98 12 18 MSTRCNST TXT 20 042 20 03 98 9 20 MSTRCNST TXT SERCONST TXT 17 327 20 03 98 9 20 SERCONST TXT BASECNST TXT 4 936 23 01 98 10 23 BASECNST TXT HEADCNST TXT 6 752 19 02 98 9 34 HEADCNST TXT SERCO MAS 20 042 20 03 98 9 20 SERCO MAS SERCO SER 17 328 31 03 98 11 22 SERCO SER 97121478 BAS 4 949 23 01 98 10 24 97121478 BAS 97121479 BAS 4 949 23 01 98 10 13 97121479 BAS 98011494 BAS 4 951 23 01 98 10 13 98011494 BAS 97121462 HED 6 780 23 01 98 10 24 97121462 HED 97121463 HED 6 781 23 01 98 18 16 97121463 HED 97121464 HED 6 780 23 01 98 10 16 97121464 HED 14 file s 158 986 bytes 2 dir s 64 389 120 bytes free The txt files above are read only The mas ser bas hed files are copies of the
2. Charge sensitivity for lightning impulse observations The signal output of the radio impulse channel for a 10V peak to peak input signal coupled via a 10pF capacitor equivalent to 100pC to the antenna to be flat to 10 between 5 and 100kHz The signal output of the radio impulse channel is to have a value of 0 50 0 05V with a continuous wave test signal at a frequency of 27kHz An impulse discharge of 315pC for example a 100pF capacitor at 3 15V is expected to give an output signal of 1 6V Lightning impulse threshold setting A signal output of 1 6 0 2V corresponds to the 315pC impulse threshold setting of the Nitro Nobel system Impulse channel operational health level checking A signal output of 0 10V 0 5V will be observed during the active periods of both 27kHz and 2 200kHz operational health oscillators This will show a displayed signal with operational health checking ON in the Test Mode around 28dB A1 3 MEASUREMENTS WITH SENSOR TEST UNIT The Sensor Test Unit provides the two main test capabilities c the check the functional performance of each observations channel d to confirm each of the alarm threshold criteria For use the Sensor Test Unit STU is mounted in fair weather conditions on top of the Sensor Unit with the 3 pillars guiding and aligning the aperture in the STU base to the sensing aperture of the Sensor Unit fieldmeter There is no need to remove the operational health shield Connection must be made fro
3. The JCI 504 Lightning Warning System comprises the following items 1 Sensor Unit providing capability to measure ambient atmospheric electric field 2 20 200 amp 2000 kV m FSD radio noise signals 27Hz and lightning impulse signals 2 200kHz from an insulated 2m antenna tube mounting the Sensor Unit above ground level and suitable for mounting to base mounting and providing 3 insulated guy tie points to ensure mounting stability A conical earthed shield is mounted under the Sensor Unit 2 Fieldmeter Zero Check Chamber 3 Length of multicore cable with 19w plug connectors each end to connect Sensor Unit to Base Unit 4 Wall or bench mounted Base Unit s providing power supply to the Sensor Unit with display of electrostatic fieldmeter reading a display of system operational status and green amber and red alarm status indicator lamps 5 Microcomputer within the Base Unit Arcom SBC GX533 running MSDOS 7 1 and linked to the main circuit board in the Base Unit via RS232 communications A floppy disc drive and 40GB hard drive are involved with external connections for a LCD VGA monitor and PS2 keyboard 6 Uninterruptable Power Supply providing at least 1 hour battery back up for system operation 7 Set of software back up discs 1 44M 8 Wall mounting Remote Display Unit for remote repeating of alarm status indication with green amber and red lights 9 Sensor Test Unit providing a selectable electric fields for checking
4. 3 5 Data storage Displayed observations are held in full detail in a ring buffer memory on the hard disc This data is rewritten in compacted form according to the level of significance of observations to an archive area of the hard drive as archived data The rates of archive data storage are set by the user or at default settings and held as text type files within year month and day directories Files can be inspected by a text editor or transferred into a Spreadsheet program for analysis and graphical display on a Windows operating system computer The time between stored data records is set for each channel in relation to set signal significance levels and to set time intervals before significant levels were encountered The archive data records are kept very nearly up to date so that there is little loss of information in the event of any major failure or problem The archived records include electric field values radio noise signal level and instances of occurrences of lightning events together with clock time operational health check indicators and interpreted alarm status and information from the various settings files The alarm status includes reference to the route by which alarms were signalled Archived data files are marked with one or two asterisks according to whether files relate to data in the medium or fast rate of data storage Stored files can then be selected and recalled from archive storage for inspection by a text
5. 4 5 3 Data storage Currently relevant observations are stored in a large ring buffer about 120MB This holds the current observations in full detail for a period of about the preceding week For long term archive storage of observations the data is compacted in relation to the significance of the signals The data is compacted by averaging observations over selected periods of time according to the level of the most significant observation over that time Three levels of significance can be set for each observation channel so that low level signals with no alarm conditions are averaged over several minutes medium level signals with no alarm conditions may be averaged over a few minutes and high level signals with an alarm condition observations may be stored in full detail By setting data recording rates independent of alarm threshold levels experience can be gained which will help assessment of the suitability of the set alarm criteria Where the data is compacted a record is kept of signal maximum and minimum during each data period These figures together with average values help to indicate something of the character of the observations even when full detail is not available Archived data is stored on a 2G partitioned area of the hard disc drive Software is provided to enable archived data to be transferred to a Windows operating PC via a serial link for inspection and any processing that will be useful The batch file in the MSDO
6. John Chubb Instrumentation Ltd En dg bg Unit 30 Lansdown Industrial Estate Gloucester Road John Chubb Cheltenham GL51 8PL UK Tel 44 0 1242 573347 instrumentation Fax 44 0 1242 251388 email jchubb jci co uk USER MANUAL JCI 504 LIGHTNING WARNING SYSTEM UM 504 Issue 2 September 2008 Registered in England No 5798844 VAT GB 392 007 172 Registered Office Unit 30 Lansdown Industrial Estate Gloucester Road Cheltenham GL51 8PL UK User Manual DRAFT JCI 504 Lightning Warning System User Manual DRAFT JCI 504 Lightning Warning System USER MANUAL JCI 504 LIGHTNING WARNING SYSTEM Contents 1 GENERAL INTRODUCTION 1 1 Basic system description 1 2 Background 1 3 Warning criteria 2 INITIAL INSTALLATION 3 OPERATING INFORMATION 3 1 Start up 3 2 Operation 3 3 Shut down 3 4 Display settings 3 4 1 Current display 3 4 2 Review mode 3 4 3 Test mode 3 5 Data storage 3 6 Archive data transfer and inspection 3 7 Adjustment of settings 3 7 1 Introduction 3 7 2 Data display and storage settings 3 7 3 Instrument performance features 3 7 4 Application arrangements 3 7 5 Risk Thresholds 3 8 System and performance checking 3 8 1 Introduction 3 8 2 On line operational checking and advice 3 8 3 Performance testing 3 8 3 1 Fieldmeter zero setting 3 8 3 2 Sensor Test Unit 3 8 3 3 Base Unit Testing 3 8 3 4 Remedial actions 3 8 4 Adjustments 3 8 5 Formal calibration 4 TECHNICAL DESCRIPTION 4 1 General aspects
7. The Base Unit has the following features Connections down right hand side of Base Unit case Complete Base Computer Sensor control Unit section Base Unit section Base Unit 1 19w connector to Sensor Unit Y N Y from main circuit board 2 25w D type serial data port to N Y Y link main circuit board to the Arcom computer board 3 9w D type male connector for Y Y N serial data transfer to a PC from the Arcom computer board 4 15w D type link to Remote Y N Y Display Units from 15w connector on main board 5 VGA connector from Arcom Y Y N computer board to monitor 6 PS2 keyboard connector to Y Y N Arcom computer board 7 IEC mains input and power Y Y Y output to display monitor to switch mode PSU 8 Earthing terminal to case Y Y Y There is also a 25w D type connector on the main PCB isolated from local earth for diagnostic signals These include all the connections to the Sensor Unit as well as the signal for the processed radio noise and lightning impulse signals in dB and the 3 alarm status indication signals For transfer of archive data to a Windows operating system computer the 9w D type make connector on the computer section of the Base Unit needs to be connected to the Windows computer RS232 serial port or the USB to serial adapter using a 9w female to 9W female null modem cable Displays 3 4 digit LCD presentation of atmospheric electric field a
8. panel and press lt return gt to implement the overall selection made This menu may be exited by pressing lt esc gt 3 4 2 Review mode Real time observations are held in a ring buffer on the hard disc and are available for on line review on the monitor screen Observations of electric field radio noise lightning impulse signals operational health status indication and alarm indications may be reviewed as they were displayed at that time or with different display timebases Data review does not affect or interact with the recording of present observations or the occurrence of alarm warning at the top of the monitor screen based on observation of current conditions This mode enables previous observations to be reviewed Graphical screen displays are stored in User Manual DRAFT JCI 504 Lightning Warning System full detail for a time that depends on the display time If the display screen has a 30s time span then full displays are only available over about the previous 24 hours whereas if the screen display is say 30 minutes then displays are available over the preceding days Data review is controlled via the Review graph section of the User Menu at the bottom of the monitor screen display see Figure 7 This panel may be selected from the current graph display using the lt tab gt key to move the cursor and the pressing lt return gt The section of records to be reviewed can be defined by specifying a start date a
9. chosen to be appropriate for loading into a Spreadsheet Within a Spreadsheet the records can be scanned according to a variety of criteria and can be shown graphically 4 5 4 Monitor screen display The monitor screen of the microcomputer displays the following information Date and time of graph display top left hand corner present Alarm status middle of the top of the screen alarm criterion responsible for present alarm status middle right of alarm status panel current date and time GMT top right hand corner graphical display with time axis on left hand boundary electric field observations in left section of display 6kV m to 6kVm alarm and operational health status indications down central band and radio noise and impulse signal observations in right hand section of display 45dB to 25dB of threshold levels user menu for selecting and setting display and review of observations at the base of the display with remaining archive data storage space indication in the bottom right hand corner The date and time in the top left hand corner of the display relates to the graphical display on view This may be current observations or earlier observations being reviewed The date and time in the top right hand corner of the screen display is always the present date and time GMT This also links to the alarm status panels from the middle of the top of the screen towards the right hand side The display of fieldmeter r
10. of the 19w connector or to pin I of the 25w diagnostic socket If the diagnostic socket is used with the Base Unit case open care will be needed to protect the PCB circuits from short circuit damage In all cases it is necessary to protect personnel from risk of shock Leads should be laid over a layer of insulation and meters should be rested on insulation be battery operated and preset to the appropriate range for measurement 3 Apply a voltage of around 1000V measured with a calibrated voltmeter to the Sensor Unit Record the change of voltage at pin 5 relative to pin 4 of the 25w diagnostic connector as the test voltage is switched on and off by earthing the output At the same time note the change in the electric field reading displayed on the monitor It is expected that application of 1000V will give a voltage change at the 25w socket around 0 6V and the change in electric field reading will be about 3kV m For 100V the change in reading will be about 0 3kV m The calibration voltages should be applied in sequence of increasing voltage values to a maximum of 1000V and 10 seconds pause should be allowed at each voltage value To allow for finite ambient atmospheric electric field values it is best to switch between zero and a defined voltage or to interchange between positive and negative voltage polarity depending which is easier with the high voltage supply unit available The change in equivalent ambient electric field shown on the
11. signal processing This arrangement allows the radio signals in the 2 200kHz and 27kHz passband to be observed directly by the software 4 2 3 Performance At the 2m mounting height of the Sensor Unit the electric field sensitivities of 2 20 200 amp 2000 kV m FSD at the fieldmeter sensing aperture provide the capability to measure ambient atmospheric electric fields of 0 17 1 7 17 amp 170 kV m FSD The gain adjustments within the radio noise and lightning impulse signal processing circuits in the Sensor Unit are set so that the signals at the threshold level of the Nitro Nobel system gives an output signal about 50 of the dynamic range on the JCI 504 system It will be possible to relate the quantities of charge induced on the antenna tube to ambient values of radiation electric fields using for example modelling calculations with the programme POTENT 5 For the present the radio signal detection performance of the Sensor Unit is defined in terms of the relationship between the output signal V and the input peak charge C Lightning impulse observations The bandwidth for lightning impulse observations between 3dB points is 2 200kHz The signal output for a continuous wave test signal input of 10V p p at 27kHz via a 10p coupling capacitor equivalent to a peak to peak charge transfer of 100pC to the antenna is 0 50V The response is flat between 5 and 100kHz The output voltage signal corresponding to the 315pC threshold sett
12. Fieldmeter Advantage is also taken of the newer approach to assessing operational heath of the fieldmeter in that the electric field at the fieldmeter sensing apertures is modulated by an alternating voltage on a shield around the sensor head unit rather than by oscillating the voltage of the head unit itself This modulation is phase related to the chopping frequency to provide a more precise and faster response assessment of operational health 1 3 Warning criteria A risk of lightning strikes at a location is considered to be present a when radio noise and lightning impulse activity indicates there is already lightning activity in the vicinity which may spread to include the location and or b when the ambient electric field at ground level due to strong electrostatic charging in nearby clouds reaches such a high level that any triggering discharge within the cloud may lead to formation of a lightning channel to ground or to another cloud The JCI 504 provides 3 levels of warning according to the perceived risk of lightning activity by the following combinations of electric field radio noise 27 0 25kHz and lightning impulse signals 2 200kHz Green No risk amp system operating normally Amber Four alternative risk criteria 1 Electric field E gt 1 5 kV m amp Noise gt Noise threshold 2 Noise gt Noise threshold amp 1 lightning event 3 Electric field E gt 3 kV m 4 2 lightning events lt 100s Red Fi
13. Type Resistance 0 08 ohms per metre each core Capacitance 160pF per meter per conductor to sheath Connectors Free plug AB05 602714 19PN00 Socket ABOS 210014 195N00 Connection allocations for JCI 504 compatible with JCI 131 fieldmeter Cable feature 19w cable connector 25w D type socket Sensor amp diagnostic Cable sheath amp case A green yellow OV B black 1 12V power supply C red amp yellow blue 2 12V power supply D blue amp blue white 3 Fieldmeter 0V E green 4 analogue back Fieldmeter signal F white 5 analogue back Range bit 0 field x10 G yellow 6 digital out Range bit I field x100 H brown 7 digital out Zero adjust J violet 8 analogue out Field overrange K orange 9 Noise signal L pink 10 analogue back Noise x10 M turquoise 11 digital out Field health inhibit N grey 12 digital out Field health drive P red blue 13 analogue back Noise health frequency adjust U green red 14 analogue out Impulse signal V yellow red 15 analogue back Impulse x10 R white red 16 digital out Impulse health control S red black 17 digital out 27kHz 100kHz osc 10s on 10s off Field health signal T red brown 18 analogue back Atmospheric electric field 24 Noise signal in dB 25 Connections from case of Base Unit Local earth bonding terminal Mains power supply in IEC connector fused Mains out to LCD monitor IEC connector PS2 k
14. characteristics of individual Sensor Units and Base Units identified by serial numbers and individual application requirements are held in separate files which may be edited and copied from the resource directory into the program directory for operational use Batch BAT files are provided for easy and protected transfer of individual files into the program directory for operational use 3 7 2 Data display and storage settings Data display time span of graphical display Data storage threshold levels for alternative frequencies of data storage 3 7 3 Instrument performance features Instrument file Electric field sensitivity of fieldmeter system observations V per kV m Charge sensitivity of radio noise observations V per C charge change at antenna Charge sensitivity of lightning impulse observations V per C charge change at antenna Serial number of Sensor Unit 3 7 4 Application arrangements Application file Height of fieldmeter aperture of Sensor Unit above local ground level Diameter and length of antenna tube Grid reference of location and altitude above sea level for information Shadowing factors by local buildings and structures 3 7 5 Risk thresholds Threshold criteria file Threshold levels of atmospheric electric field and time over which level is exceeded to be considered significant Threshold level and time over which radio noise is considered significant Threshold step change level at
15. copy the files from the floppy to the C drive COPY A C There will be a prompt to overwrite the AUTOEXEC BAT and CONFIG SYS files choose yes Y for both 4 5 2 Signal interpretation and display The electrostatic fieldmeter readings are interpreted as ambient electric field values see Section 3 2 1 above and displayed on the monitor screen in blue with a linear scale graph from 6kV m to 6kV m The radio noise and lightning impulse observations are displayed in mauve and cyan on a single logarithmic scale graph as dB values relative to their individual set threshold signal levels with spans 45dB to 25dB The radio noise signal is software processed with a perfect diode to provide a display with 25ms response risetime and 100s fall time The trace hence indicates the peak levels of noise signal and an influence of the frequency of occurrence of pulses This radio noise signal is interpreted by software as dB relative to the set threshold level and displayed as such on the Base Unit LCD and on the monitor The lightning impulse signals are assessed by the amplitude of impulse signals relative to the set threshold value The impulse recognition threshold is arranged to follow the rise and fall of individual lightning impulse signals so that small pulses can be observed even if they occur in the wake of larger ones while these are still above the original set level In the absence of impulses the threshold level reverts to the set value
16. editor or on a Spreadsheet according to significance category of the observations date etc 3 6 Archive data transfer and inspection Numerical data of each channel of observation is stored to an archive area of the hard disc drive User Manual DRAFT JCI 504 Lightning Warning System Data is stored within day files within month folders within year folders The level of detail of observations stored within day files depends upon the level of significance of the peak values of signals High signal levels on any channel result in more frequent storage of average data values Selected periods of archived data can be transferred over a serial data link to a Windows operating system computer so it can be separately stored inspected and perhaps numerically processed The software for sending archived data is preinstalled in the Base Unit Arcom computer The software for operation on a Windows operating system computer JCIS04AD is supplied on a CD This may be loaded by clicking autorun on the CD drive This creates an icon which will start software operation when clicked Where the Windows computer does not have a direct RS232 serial data port then a USB to serial port adaptor needs to be used The 9w D type make connector on the computer section of the Base Unit needs to be connected to the Windows computer RS232 serial port or the USB to serial adapter using a 9w female to 9W female null modem cable The JCI 501 softwa
17. monitor display will be the voltage applied divided by the Sensor Unit height for example for a Sensor Unit at 2m height application of 1000V should show a display of 500V m Calculate and record the voltage sensitivity values in terms of the voltage change at the 25w socket and in terms of the change in electric field reading 4 For a Sensor Unit height h above fairly flat local ground and application of a voltage V the equivalent local atmospheric electric field Egg is Eq V h If simultaneous measurements of atmospheric electric fields are made with a mobile fieldmeter over a nearby flat area of ground have shown a ratio R between the above value of Eeg then the value of the electric field displayed on the monitor should reflect this same ratio If the mobile fieldmeter is for example a hand held unit held well above the head then it is necessary to establish the relationship between its readings and the ambient electric field in its open area situation This means measuring its voltage sensitivity and its height just as above A1 2 2 Fieldmeter operational health check In normal operation the heath shield around the Sensor Unit will have a sine wave alternating voltage applied whose peak voltage varies for the 4 ranges of fieldmeter sensitivity as 3V 30V 300V and 300V The frequency is about 55Hz The two output signals are nominally 1V on pin 13 for the operational health drive and nominally 1V on pin 18 for the operational heal
18. returned to JCI so they can be disposed of or recycled in an environmentally appropriate manner Signed for and on behalf of John Chubb Instrumentation Ltd ON J N Chubb 28 March 2007 User Manual DRAFT JCI 504 Lightning Warning System USER MANUAL JCI 504 LIGHTNING WARNING SYSTEM A system providing advance warning of the risk of local lightning on the basis of observations of atmospheric electric field radio noise and lightning impulse signal activity Combinations of measurements of these three parameters provide two levels of warning to enable action to be taken to protect personnel and equipment 1 GENERAL INTRODUCTION 1 1 Basic system description The JCI 504 Lightning Warning System provides warning of the risk of local lightning strikes on the basis of measurement of the local atmospheric electric field and observation of radio signal created by pre exiting lightning activity The system is basically an updated version of the Nitro Nobel Lightning Forecasting System VSL2 1 The JCI 504 system like the preceding JCI 501 system 2 comprises two main parts a Sensor Unit and a Base Unit that includes a microcomputer for analysis and display of observations and for the assessment of risk The Sensor Unit is mounted on open ground well away from nearby buildings and sources of physical pollution and electrical noise The Sensor Unit comprises an electrostatic fieldmeter suitable for continuous operation in adverse enviro
19. second unit houses the Arcom computer with opportunity for serial data fibre optic communication to the first base unit The computer unit provides the full monitor display of observations with operational and alarm status indication as well as recallable and archive storage of observations The Base Unit circuit boards are arranged so that most electrical connections are made via PCB mounted connectors This will make it easy to switch circuit boards if any supplier servicing is needed to correct faults It also makes it easy to connect test and diagnostic facilities to the board Only minor adjustment facilities are included on this circuit board so boards may be interchanged without change of system characteristics The signal processing circuit is linked from the 25w D type connector on the circuit board to the 19w Sensor Unit cable socket A second 25w D type connector is mounted on the PCB and wired with the same pin connections so this can act as a diagnostic port for all incoming signals and outgoing control functions Both 25w connectors include signals for the interpreted value of the atmospheric electric field and for the radio noise in dB Pin allocations are shown in Figure 5 The input signals are presented to differential input amplifier stages to remove any common earth shift signals The fieldmeter input stage is arranged to also provide 2 048V level shifting to match the 2V to 2V bipolar input signals to the ADC with a unipolar inpu
20. section of the mounting insulation One of these connections is the input of the radio observation circuits the other is to the operational health test oscillators Connections from the fieldmeter operational health circuitsto the operational health shield are also made via two spring loaded contacts one for the drive voltage and the other for the drive measurement circuit The electric field measuring part of the Sensor Unit is designed to look straight up to the sky In this orientation it is exposed directly to atmospheric weather conditions All insulation is designed with long tracking paths and large gaps to be immune to the incidence of rain and the unit is provided with holes for draining away rain water Operational performance will be adversely affected if debris or material is allowed to collect within the head unit see Sections 5 and 6 4 4 Base Unit The power supply data handling and signal display circuits in the Base Unit are powered from a mains supply 110 240V with an Uninterruptable Power Supply unit providing 1 hour battery User Manual DRAFT JCI 504 Lightning Warning System back up for the whole system operation The power supplies for the Sensor Unit for the signal processing and serial communications facilities are dc dc converter isolated from earth This provides lightning transient isolation It also allows a d c voltage to be applied to the Sensor Unit for in situ fieldmeter voltage sensitivity calibration
21. the performance features of the instrument sections involved in electric field radio noise and lightning impulse measurements the way measurements are interpreted for their hardware application risk assessment level values the signal levels for selection between 3 time intervals over which measurements are averaged for writing long term records Information on the performance characteristics of the system are held in a number of software files A default set is held in a master file mstrenst txt Separate default files are held for a default Sensor Unit headCnst txt for a default Base Unit baseCnst txt and for default application features serconst txt These default files are held as read only files The characteristics of individual Sensor Units and Base Units identified by serial numbers and individual application requirements are held in separate instrument files which may be edited and copied from the resource directory into the program directory for operational use The instrument files are identified by the serial number of the Sensor Unit serial number hed one for each individual Sensor Unit These are all held in the resources subdirectory The program uses one of these files which has been copied to the file headenst txt held in the program directory Batch BAT files are provided for easy and protected transfer of individual files into the program directory for operational use The fieldmeter
22. which a lightning impulse signal is identified minimum time separation for individual lightning events maximum time separation between 2 events for yellow alert and maximum time separations between any 2 of 3 consecutive events for red alert 3 8 System and performance checking 3 8 1 Introduction Operation of the JCI 504 Lightning Warning System can be tested at 3 levels a operational health monitoring during normal operation see 3 4 2 b regular fair weather performance tests using the Sensor Test Unit to apply measured signals to User Manual DRAFT JCI 504 Lightning Warning System the fieldmeter and to the antenna so that software displays can be tested and alarm criteria checked see Section 3 9 3 and Annex Al During such tests the software is normally operated in a Test mode While data records continue to be taken these are marked to indicate they relate to operation under test conditions c formal calibration using parameters whose accuracy is traceable to National Standards see 3 8 4 The relationship between the signals measured and ambient lightning related parameters ambient atmospheric electric fields in V m and noise and impulse radio signals in pC is discussed in Section 4 Testing to help identify the source of any performance deficiencies encountered and actions to correct these is described in Section 5 3 8 2 On line operational health checking and advice The system includes arran
23. 2 20 200 amp 2000 kV m electric field values at the fieldmeter sensing aperture In set up and calibration the specific values of electric field at the sensing aperture are generated according to the formal calibration procedure described in BS 7506 Part 2 1996 The sensitivity of the Sensor Unit in the JCI 504 system to the local voltage around the Sensor Unit may be calibrated in situ in fair weather conditions when the atmospheric electric field is low and steady by applying a calibration voltage to the Sensor Unit relative to earth and measuring the signal output The signal processing and serial data communication circuits in the Base Unit are opto isolated to withstand over 1000V so calibration voltages can be applied safely up to 1000V While calibrating the voltage sensitivity by applying a voltage to the Sensor Unit it is important to keep personnel away from the area for safety and to avoid perturbation of the ambient electric field environment around the Sensor Unit mounting User Manual DRAFT JCI 504 Lightning Warning System Calibration involves the following steps 1 With the system working in test mode temporarily remove the earth bonding of the Sensor Unit to its mounting base Check that the resistance to earth is high this may be done at the Sensor Unit or back at the base Unit between the 19w cable connector and the local earth 2 At the Base Unit arrange to connect a high voltage supply up to 1000V either to the case
24. 4 2 Technical design features 4 2 1 Sensor Unit Electric field measurements 4 2 2 Sensor Unit Antenna and antenna circuits 4 2 3 Performance 4 3 Sensor Unit construction 4 4 Base Unit 4 5 Software signal processing 4 5 1 General 4 5 2 Signal interpretation and display 4 5 3 Data storage 4 5 4 Monitor screen display 4 5 5 Alarm indications User Manual DRAFT JCI 504 Lightning Warning System 4 5 6 User menu 4 5 7 File information 4 6 Operational health monitoring 4 7 Remote alarm display unit 4 8 Uninterruptable power supply 5 MAINTENANCE 6 MAINTENANCE SCHEDULE References Figures 8 Annex 1 Performance testing for JCI 504 Lightning Warning System Annex 2 Comparison of threshold signal settings Annex 3 Software directory tree for JCI 504 Annex 4 JCI 504 User Files 2000 COMPLIANCE The JCI proprietary software used with the JCI 504 Lightning Warning System has been tested for 2000 compliance The software operates in true MSDOS mode and use the computer system clock to provide date and time information The software program is hence as 2000 compliant as the computer system clock RoHS and WEEE Directives JCI electrostatic measuring instruments are not required to conform to the RoHS Directive because they come within Category 9 exemption To comply with the requirements of the EC WEEE Waste Electrical amp Electronic Equipment Directive all JCI instruments at the end of their useful life should be
25. Amber alert thresholds The amber alarm threshold should be exceeded for the higher and not by the lower combinations a Electric fields 1 3 amp 1 7kV m with noise signal 1 8pC amp 2 6pC scanned over 26 0 28 0kHz b Noise signal 1 8pC amp 2 6pC scanned over 26 0 28 0kHz with single impulse signals 75kHz 230pC amp 410pC pulses with 150s separation c Electric fields 2 8 amp 3 2kV m d Impulse signals 75kHz 230pC with pulses separated by 90s 230pC then 75kHz and 410pC pulses separated by 90s Red alert thresholds The following tests are carried out by pressing the Select pushbutton The red alarm threshold should be exceeded for the higher combinations but not by the lower combinations e Electric fields 1 3 amp 1 7kV m amp noise signals 1 8pC amp 2 6pC scanned over 26 0 28 0kHz with single 75kHz pulses 230pC amp 410pC 150s separation or more User Manual DRAFT JCI 504 Lightning Warning System f Noise signals Q 1 8pC amp 2 6pC scanned over 26 0 28 0kHz with two 75kHz 230pC amp 410pC pulses Q 150s amp 90s separation f Electric fields 2 8 amp 3 2kV m with single 75kHz pulses 230pC amp 410pC 150s amp 90s separation g Three 75kHz impulse signals 230pC amp 410pC 150s amp 90s separation h Electric fields 4 2 amp 4 7kV m User Manual DRAFT JCI 504 Lightning Warning System Annex 2 COMPARISON OF THRESHOLD SIGNAL SETTINGS BETWEEN NITRO NOB
26. EL VSL2 SYSTEM AND JCI 504 SYSTEM A2 1 Atmospheric electric field measurement It is not clear how the NN system relates its calibration of the fieldmeter to the ambient atmospheric electric field The discussion in Section 3 above provides a clear relationship for this relationship with the JCI 504 system The electric field values used by the NN system are typical values which may be expected below a thundercloud and so are reasonable to use A2 2 Antenna signal observation circuit The antenna input of the NN system is linked in the signal processing circuit to a 22nF capacitor with 47k in parallel to earth This input capacitance will swamp capacitance loading of the antenna tube by the enclosed cable linking signals back to the base unit Spreadsheet modelling the input stage amplifier of the NN system IC2 shows the frequency response is fairly flat with increasing frequency The approach adopted in the JCI 504 of a virtual earth charge sensitive preamplifier has a similarly flat frequency response Basically the same antenna is used in the JCI 504 as for the NN system so the radio signals picked up should be similar A2 3 Radio noise signals 27kHz A test signal of 100uV 10 v p p at 27kHz to the antenna input of the NN system will correspond to a charge change on the capacitor C12 of 2 2pC The threshold level of 100uV from the connected antenna seems to relate to an output at the comparators around 7V so the overall gain thro
27. If two Remote Display Units are to be used then the 15w connector is linked to a splitter box from which separate 6 way cables are connected to each of the Remote Display Units 15w D type connector Remote Display Unit A Remote Display Unit B 2 1 Red A 9 2 Yellow A l 3 Green 10 4 Lamp sense A 3 5 Ground sense A 4 amp 11 6 Ground A 6 l Red B 13 2 Yellow B 5 3 Green B 14 4 Lamp sense B 7 5 Ground sense B 8 amp 15 6 Ground The earth isolated sections of the main and the display circuit boards are powered via a dc dc converter with good high voltage electrical isolation Signal linkage to the RS232 linkage to the local microcomputer and for remote alarm signalling is via opto isolators User Manual DRAFT JCI 504 Lightning Warning System The Base Unit can be configured into 2 separate units if it is desired to have the displays remote from the unit providing power supplies to the Sensor Unit and displaying all the status indications and basic electric field and radio noise values For this separated situation one unit houses the circuits providing power to the Sensor Unit and the circuits receiving data from the Sensor Unit and digitizing this for communication with the processing computer via a fibre optic link from the 25w serial data port connector The cover panel displays the present values of atmospheric electric field and noise and all the status an alarm indications The
28. Mount guy line support ring to antenna tube about 1 quarter of the way down tube and secure with clamping screws Attach suitably adequate lengths of polypropylene or User Manual DRAFT JCI 504 Lightning Warning System similar guy lines 7 Lay the antenna tube down with one end towards the mounting spike and position the Sensor Unit near the other end of the antenna tube Feed the earthing lead from the Sensor Unit down the antenna tube and through the insulation mount and out through the aperture in the mounting spike 8 Feed the main cable and connector up through the antenna tube to the Sensor Unit and connect to the 19w connector on back of Sensor Unit 9 Mount the Sensor Unit into the top of the antenna tube 10 Elevate the antenna tube with the Sensor Unit on top and feed excess cable back through the base support insulator so the antenna tube can be socketed it into the base insulator 11 Connect the Sensor Unit earthing cable to a terminal on the side of the spike or a nearby earthing rod 12 Drive the guy support spikes securely into the ground at suitable positions around the antenna tube and then attach guy lines and tighten to stabilize the antenna and Sensor Unit assembly against wind If the erection of the Sensor Unit and antenna is carried out by tall personnel it may prove easier to erect the antenna tube and adaptor by itself after the cable has been threaded through and then to connect the Sensor Unit and socket this on t
29. S operating system is 504send and the Windows compatible program on the PC is 504recev Data transfer will be on User Manual DRAFT JCI 504 Lightning Warning System the basis of selected months Transfer will need to take place during a pause in direct monitoring operations The handling of archive data is different from the JCI 501 system because it has not been possible to obtain the same Panasonic magnetic media disc writer unit as used on St Kilda Stored data records are marked to indicate the assessed operational health status of each signal channel and also the operational health of the cable connection between the Sensor Unit and the Base Unit and of the serial data link between the computer and the Base Unit The on line data records can be recalled via the review section of the graph menu see Figure 6 The loading and manipulating of large files may be quite slow so a useful strategy may be to call up the whole time period of interest note the times of occurrence of any events of interest and then recall those periods in good detail Archived data is stored in a form csv format which enables records to be easily inspected by a simple text editor or loaded into popular Spreadsheet software The file names include one or two asterisks to indicate the level of significance of the observations in each file and so enable files to be easily selected for inspection according to significance The size of the record files has been
30. Sensor Unit Showing Sensor Unit with fieldmeter operational health shield earthed conical shield antenna tube and insulated mounting socket User Manual DRAFT JCI 504 Lightning Warning System Figure 3 Base Unit Main Base Unit VOL 504 LIGHTNING WARNING SYSTEM Computer Base Unit with fibre optic serial data modem JCI 504 Lightning Warning System DRAFT User Manual Display of normal operation Figure 4 e ee ee i 1 JCI 504 Lightning Warning System DRAFT Radio signal strengths vs frequency Terman User Manual Figure 5 o R DO g 3 ss 23 o OG S DS E os 2 oc e oo 3 og ory A i NO e TE 23 Aes ca 3 2 LE Es 11 on 23 vr z S 3 A s dl a os Ap gt amp F E TFs 33 E Hi r t S 3 a rie G 3 E TOn 53 5 m D A NTE T Mile 34 MITT M los 3338 8 S or 3 me E o 8 G 2 a SR OE MTT Is 2 Ed 3 m UOI I MT A aS a SS e N ox on Eg a Y N o oco o BS Figure 6 User Manual DRAFT JCI 504 Lightning Warning System Figure 7 CONNECTIONS FOR SENSOR UNIT TO BASE UNIT Connections between the sealed 19w cable connectors Pattern 105 linking the Sensor Unit to the Voltage Modulator Unit and to the Base Unit and the internal 15w D plug and socket connectors to the Base Unit PCB are listed below The same cable colour coding is to be used for the interconnections within the Base Unit box Cable DEF STAN 61 12 Part 4 Screened 7 2 C
31. adio signal observations and status indicators is written down the screen to a time axis on the left hand side of the display and is then overwritten successively from the top down in reversed video Numeric values of the parameters are displayed at the top of each graph The microcomputer monitor display and the stored data include indications from the operational health monitoring tests carried out during system operation and whether the system was operating in test mode or not These indications will show whether all measurement capabilities appear fully normal appear satisfactory but degraded or non operational see Section 3 6 These indications are communicated to the Base Unit for display as operational status indicators They are logged on the data records together with any failure of the cable link to the Sensor Unit or the serial communications link to the Base Unit User Manual DRAFT JCI 504 Lightning Warning System 4 5 5 Alarm indications In the centre of the top of the screen display is an alarm status panel showing a steady green for no alarm conditions a Slow flashing amber alert panel which alternately shows the word amber in yellow on a white ground and reverses to white on an yellow ground a faster flashing red panel which alternately shows the word RED in red on a white ground and reverses to white on a red ground to indicate a Red alarm If the software recognises that connection to the S
32. ase Unit and to the microcomputer if this is separate After shut down it is recommended to release any floppy disc in its drive This is to avoid problems at restarting system operation If any access is to be made within the Base Unit or any work carried out there then be sure to pull out the mains plug to the Base Unit for safety At shutdown a menu provides options to restart the JCI501 software for entering MSDOS or for transferring archive data 3 4 Display setting When system operation is started the computer monitor display shows the current status values and the graphs running to clock on the wall time The menu bar beneath the graphical display provides three main options operation in current in test mode and for review of earlier observations 3 4 1 Current display Within the current display changes may be made to the timebase of the display The menu providing opportunity to adjust settings is entered by pressing lt return gt with the cursor on the current display panel The lt tab gt key to move the cursor to the span panel and type in a new span number Press lt return gt to confirm the choice If desired use the lt tab gt key to move to the next panel to select time units Here the up and down arrow keys provide opportunity to select between centiseconds seconds and minutes Press lt return gt to confirm the choice and then move to the confirm choice
33. asting System VSL 2 5 see also discussion in Annex 3 4 TECHNICAL DESCRIPTION 4 1 General aspects The JCI 504 system comprises a Sensor Unit mounted on clear open ground well away from other structures and cable connected to a Base Unit with power supply signal handling and serial data communication linkage to a microcomputer The general arrangement is illustrated in Figure I User Manual DRAFT JCI 504 Lightning Warning System with the Sensor Unit arrangement shown in Figure 2 The Sensor Unit uses a JCI 131 electrostatic fieldmeter for continuous monitoring of ambient atmospheric electrostatic fields with the Sensor Unit mounting tube used as an antenna for observation of radio noise and lightning impulse signals Electronic circuits within the Sensor Unit carry out all primary signal processing and conditioning so that the signals communicated to the Base Unit and to the microcomputer are quantitative values of the electric field radio noise and lightning impulse signals observed The observed radio noise and lightning impulse signals are stretched in time to have a 20ms decay time constant while retaining peak amplitude information to ensure reliable analogue conversion RS232 communication and software analysis Assessment of these signals is carried out by software Connections for the cable linking the Sensor Unit to the Base Unit are shown in Figure 7 together with connections for the 25w D diagnostic connector on the Base Unit
34. ch may be exercised by digital control signals at the Base Unit take precedence over default internal automatic control accuracy and linearity within 1 of range full scale for each sensitivity range analogue signal output 2 0V corresponding to FSD reading noise below 10 Vm zero offset stable long term within 50 V m on 2kV m range remote zero adjustment facility for zero setting adjustment when sensing aperture is known to be shielded power supply required 18 36V regulated connections to sensing head unit via shielded multicore cable see Figure 7 3 power supply lines 12V OV 12V analogue electric field signal 2V signal earth 2 analogue sensitivity control lines zero setting line the electric field measurement performance set up using calibration procedures as described in BS 7506 Part 2 1996 Annex A2 The ambient atmospheric electric field E is measured using the fieldmeter at its mounting height as a potential probe with E V h where V is the local voltage V and h the height m The sensitivity of a fieldmeter mounted well clear of nearby surfaces as a potential probe is close to V E d where E is the fieldmeter reading kV m and d the effective sensing head diameter m Hence the ambient electric field is obtained from measurement of the electric field at the fieldmeter sensing aperture as E Ed h There will be a contribution to the electric field measured dependent on the alignment
35. clean the front cover may be replaced and resecured with the 4 M2x6mm screws Instrument operation and the zero reading should now be checked before returning the instrument to normal operation 6 MAINTENANCE SCHEDULE Every 6 months 1 Clean and wash out sensing region of electrostatic fieldmeter with warm water as described in Section 5 above 2 Check antenna tube clear of corrosion and clean if necessary 3 Check connections between Sensor Unit and antenna tube to be clean and clear of debris Clean weathershield and guy line insulation 4 Check the cable connecting between the Sensor Unit and the Base Unit is free of damage along its length and is not under excess tension 5 Test all performance features and record results 6 Remove the mains supply to the Uninterruptable Power Supply unit and check the system operates for at least one hour before restoring the mains supply References 1 Nitro Nobel Lightning Forecasting System VSL 2 Service Manual 2 J N Chubb J Harbour 4 system for the advance warning of lightning Paper presented at the Electrostatics Society of America ESA 2000 meeting Niagara Falls June 18 21 2000 Abstracts for ESA2000 are available on the ESA Website www electrostatics org 3 J N Chubb Two new designs of field mill type fieldmeter not requiring earthing of rotating chopper IEEE Trans Ind Appl 26 6 Nov Dec 1990 p1178 4 J N Chubb Experience with electrostatic fieldmeter ins
36. continuous signal at 27kHz It turns out as noted in Annex A2 that the response of the 27kHz noise channel to an impulse charge transfer is essentially the same as that of the impulse observation channel The response of the 2m tall 53mm diameter antenna to radio signals will be influenced by the shadowing effects of any nearby structures In view of the long wavelengths of the signals observed it seems plausible that a similar adjustment factor might sensibly be used for the radio signals as for the electric field 4 3 Sensor unit construction The sensing head unit is 100mm diameter and 115mm long brass casing All surfaces around and within the sensing region are gold plated to avoid corrosion and risk of generation of electrochemical potential difference The Sensor Unit contains all the fieldmeter operational health radio signal processing and power supply circuits The power supply input from the Base Unit is processed by a 9 36V input dc dc converter to ensure that the power supplies within the Sensor Unit are adequately independent of resistive losses within the cable from the Base Unit The head unit is constructed to avoid problems from corrosion and to protect all electronic circuits and cable connections against moisture and corrosion The Sensor Unit is mounted on weather shielded insulation and fitted on to the top of the antenna tube Connections to the antenna tubes are made via two spring loaded contacts in the antenna tube socket
37. d by readings appearing on the Atmospheric electric field LCD The electric field display on the Base Unit is scaled to match the monitor numeric display The alarm indicators on the Base Unit should be ignored until the computer software has been operating for at least 100s to allow time constant effects to settle down The computer software will start operation as soon as the power is switched on It is designed to self load and start normal operation with presentation of observations by the Sensor Unit on the monitor display Full normal operation may take perhaps 5 minutes to be established because of some long response times built into parts of the software This time is taken up by the software tuning the radio noise operational health oscillator to match the observational filter frequency and User Manual DRAFT JCI 504 Lightning Warning System also by processing of the fieldmeter operational health signal Full normal operation is indicated by All clear in the top center panel green panels to the right and just a green band down the middle of the diagnostic trace area Once this has been achieved the system should operate unattended and with the minimum of involvement and attention of the user for extended periods Default settings will automatically be brought into use at any system restart If the date and time do not correspond to local values then exit software to return to MSDOS and refer to MSDOS User s Guide via the He
38. d from the 2 200kHz observation channel The apparently low response is associated with the high Q filtering about 55 which dilutes the effect of a brief impulse input signal A2 4 Lightning impulse signals 2 200kHz In the NN system the lightning threshold level is set to be equivalent to an electric field change of 14 V m The lightning impulse test signal for threshold detection for the NN system is 7 5V on a 42pF capacitor This is a test charge transfer of 315pC User Manual DRAFT JCI 504 Lightning Warning System Spreadsheet modelling calculations indicate that the NN threshold field change could be provided by a 1C lightning discharge at an altitude of 5000m and at a range of 18km In the JCI 504 system the preamplifier connected to the antenna is a virtual earth charge detector with a 1 0nF feedback capacitor An input charge change of 315pC will be equivalent to a source voltage change from the preamplifier of 315mV With a total basic gain 2 200kHz of x5 as a gain sequence of x5 x0 4 x2 5 x1 preceding detection an asymmetric input charge change of 315 pC with low Q filtering 0 7 will give an output of 1 6V The JCI 504 system has an additional x10 software switchable gain available Calibration of the 2 200kHz signal channel of the JCI 504 is conveniently made using a continuous wave 10V peak to peak signal at a frequency of 27kHz input coupled via a 10pF capacitor which is 100pC peak to peak charge change A conti
39. ensor Unit fieldmeter There is no need to remove the operational health shield but care is needed to ensure that the guidance pillars DO NOT enter the fieldmeter sensing aperture Connection must be made from the radio test signal output terminal on the right hand side of the unit to a 50mm Terry clip around the antenna tube mounting the Sensor Unit The test unit is powered by two PP3 batteries in a double battery compartment near the back of the right hand side of the unit The unit is switched on by the switch near the battery compartment LEDs on the front panel indicate green for satisfactory condition of each battery red if a battery needs to be replaced Several hours of continuous operation can be expected from a new battery The parameter and signal level in use is indicated by the small red LEDs on the control and display panel As testing the alarm criteria with impulses involves times of 90 or 130s between pulses a green LED has been positioned by the 75kHz impulse channel to indicate this channel is active Functional performance Checking the performance of each of the 3 observation channels electric field radio noise and radio impulse is performed with the Base Unit software operating in Test Mode In this mode each of the observation channels can be tested individually or at the same time as the other channels Each channel can be triggered by its Step pushbutton This will cause the signals for that channel to sca
40. ensor Unit has been lost or that the there is a problem with serial data communications to the Base Unit then there is no possibility of a rational assessment of alarm status In these conditions the central alarm panel shows the type of failure identified in grey or black on a white background To the right of this alarm status panel is an alarm source panel which shows which criteria were exceeded to generate the displayed alarm status The amber alert state is maintained for 10s after reversion of the conditions to no alarm and the red alarm state is maintained for 30s after reversion of conditions to amber or green conditions Ifthe operational health of any observation channel is judged doubtful or unsatisfactory then the appropriate section of this secondary alarm source panel is arranged to flash to amber or to red The alarm status indication is communicated to the Base Unit and used to operate Green Yellow and Red LEDs on the Base Unit These indicating lamps can be mirrored at a remote location by landline linkage The remote display LEDs are connected partly in series with second local LEDs so that any interruption of the remote linkage can be recognised by a dimming of these second local LEDs The alarm status indication is displayed together with operational health status indication in a narrow section of the graph alongside electric field and radio observations This record is also displayed with the corresponding observations du
41. es testing with the Sensor Test Unit to be carried out by a single operator without need for communication or linkage back to the Base Unit Alarm criteria checking Checking correct response to the various levels and combinations of signals associated is carried out in the normal mode of software operation Each parameter channel can be set independently to provide signals just below and just above the various alarm threshold levels To ensure proper User Manual DRAFT JCI 504 Lightning Warning System response to the narrow bandwidth noise channel the noise signal is scanned fairly quickly over the range 26 0 to 28 0kHz The signal processing software will pick out the peak response from within this band The various combinations appropriate to non activation and activation of the two levels of alarm can be worked through While this may usefully be done with personal radio communication between the operator of the Sensor Test Unit and another observing the Base Unit display it can be done by just the one operator to a set pattern with the performance checked by subsequent inspection of the data records Tests involving the impulse signals will take some time because of the need to make observations with a number of impulse signals spaced 130s apart and also spaced 90s seconds apart The following procedures are suggested for testing with the Sensor Test Unit STAGE 1 AUTO TESTS Carried out in Test Mode Enter test mode of s
42. eyboard socket VGA Monitor socket outlet 15w D type connector for Remote Display Units 9w D type connector for RS232 linkage to PC for transfer of archive data 25w D type connector for RS232 linkage to remote microcomputer possibly via opto links 19w Sensor Unit connector User Manual DRAFT JCI 504 Lightning Warning System Figure 8 Menu structure User Manual DRAFT JCI 504 Lightning Warning System Annex 1 PERFORMANCE TESTING FOR JCI 504 LIGHTNING WARNING SYSTEM A1 1 INTRODUCTION The relationships between the local atmospheric electric fields associated with lightning events and the electric field at the sensing aperture of the electrostatic fieldmeter are discussed in Sections 3 1 and 3 2 The antenna signals linking into the radio noise and lightning impulse circuits are discussed in Sections 3 2 and Annex A2 The signal response characteristics for individual Sensor Units are held in a software application file The performance features of the JCI 504 system are described in the following paragraphs A1 2 A1 3 and A1 4 and in Annex A2 Performance figures may checked using the Sensor Test Unit mounted on the Sensor Unit Alternatively and more precisely measured test signals may be applied from suitable signals generators Signal voltage values may be measured at the Base Unit on the appropriate pins of the 25w diagnostic connector Figure 7 using pin 4 as common for earth then pin 5 for elec
43. f extension times for alarm conditions at end of events 11 Array of max members integer in event stack for each type that is stacked 112 Array of minimum times in the event stack real seconds 113 Array of channel allocations to the channel types 114 Array of information class allocations to the stacked types 136 Archive recording rate thresholds 137 Archive drive letter 138 Archive maximum file size Baseconst 10 File Description 141 Base parameters in form revised to suit jci calibration procedures Headcnst 10 File Description 128 Noise Attack Time Constant 129 Noise Decay Time Constant 140 Instrument parameters in form revised to suit jci calibration procedures User Manual DRAFT JCI 504 Lightning Warning System Calibration In general recalibration of a head unit will require entries in 40 above to be modified JCI will supply a modified file for the user to install Noise Receiver Fieldmeter Signal kVolts change applied to fieldmeter body Factor meters height off ground Frequency always 0 0 Result Volts change observed at fieldmeter output Health Volts change observed at fieldmeter output due to health signal Range optimally X10 Divide always false for height factor Det Gain always 1 0 Signal Volts Pk Pk applied via series capacitance Factor Farad Series Capacitance Frequency 27kHz Result Volts observed at noise receiver output Health Volts observed at noise receiver output due to health signal Ran
44. f sound as about 3s per km 2 INITIAL INSTALLATION 2 1 Introduction Figure 1 shows an overall schematic arrangement of the JCI 504 system Figure 2 shows the physical arrangement for mounting the Sensor Unit The Base Unit Figure 3 incorporates the microcomputer that runs the MSDOS software to process and to analyse observations to provide warning indications and to run the monitor display The Sensor Unit should be sited well away from buildings trees and structures preferably more than 50m It operates in all weather conditions The Base Unit should be in an area protected from the weather and needs a mains power supply This Unit is conveniently mounted in a building that may be up to 200m away from the Sensor Unit location The Base Unit will usually have a keyboard and monitor connected to the microcomputer so this needs to be located where advantage can be taken by operational personnel of the direct display presentation of observations and alarm indications Where monitoring of observations is best done remote from the position of the Base Unit then it will be appropriate to have the microcomputer mounted in a separate computer case and have an appropriate RS232 link between as shown in Figure 1 2 2 Set up Base Unit The Base Unit system comes in two configurations 1 A Base Unit that includes all the circuits and power supply for supporting operation of the Sensor Unit the microcomputer with LCD monitor and front panel displa
45. fieldmeter performance a 1 300kHz signal generator of selectable frequency and amplitude for checking lightning impulse signal response and a 27kHz signal generator of adjustable amplitude for checking radio noise signal response Signals can be combined for testing the alarm determination logic 10 User manuals Individual Sensor Units and Base Units each carry a unique serial number This number is built up as yymmnnnn in which yy shows the year mm shows the month and nnnn is a 4 digit sequence number covering all JCI instruments 4 2 Technical design features 4 2 1 Sensor Unit Electric field measurement Atmospheric electric fields are measured using a JCI 131 field mill type of electrostatic fieldmeter User Manual DRAFT JCI 504 Lightning Warning System Basic features of the JCI 131 electrostatic fieldmeter incorporated into the Sensor Unit are field mill type of electrostatic fieldmeter based on proprietary JCI design features 2 to provide continuous long term electric field monitoring capability with no earthing of the rotating chopper and an electronically commutated drive motor sensitivity ranges of 2 20 200 and 2000kV m FSD With a 2m mounting height and a 0 17m diameter operational health shield these sensitivity ranges correspond approximately to local atmospheric electric fields of 0 17 1 7 17 170 kV m sensitivity ranges set automatically or by remote analogue control Remote analogue control whi
46. ge always X10 Divide always true for series capacitance factor Det Gain always 1 0 Impulse Receiver Signal Volts Pk Pk applied via series capacitance Factor Farad Series Capacitance Frequency Of source 2 200kHz Result Volts observed at noise receiver output Health Volts observed at noise receiver output due to health signal Range always X10 Divide always true for series capacitance factor Det Gain 2 0 for continuous signal test 1 0 for capacitance discharge test
47. ge with its high d c gain the antenna is capacitively isolated from the charge amplifier input A resistor to ground between the input coupling capacitors provides some additional low frequency roll off of sensitivity Signals from the charge sensitive preamplifier stage are split into the two observation channels and amplified by pre settable gain stages The signals are then filtered to provide 2 200kHz and 27 0 25kHz bandpass characteristics After further amplification the signals are precision rectified and processed by peak detection and buffer output circuits with a sufficiently long decay N 177 User Manual DRAFT JCI 504 Lightning Warning System time 20ms to ensure that even the shortest transients will be reliably observed with the 0 01s ADC multiplexing interval of each signal channel A gain around x5 following the charge sensitive preamplifier is the largest sensible for the lightning impulse signals With the Nitro Nobel threshold level of 315pC input charge the voltage developed by the preamplifier stage will be 1 6V so the following gain needs to keep signals within the maximum linear signal handling capability of the operational amplifiers used The 2 200kHz lightning impulse signal after a x2 5 gain stage is selected by a single stage x1 4 gain 200kHz low pass active filter and a single stage x1 4 gain 2kHz high pass active filter The Q of the impulse filter circuits is kept low around 0 7 for good response to single i
48. gements for continuous testing and recording of the operational health status of measurements of electric field and the two radio signals Operational health status is displayed by LEDs on the Base Unit and by status traces in the middle section of the monitor screen display Health status details are also logged to the data records and are retrieved along with electric field and radio observations Operational checking involves as described in 4 6 application of signals which are directly equivalent to actual observations by the Sensor Unit The fieldmeter health is checked by applying a modest modulated voltage to a shield around the Sensor Unit to create a defined varying electric field component at the fieldmeter sensing aperture This is done as a phase locked sub harmonic of the chopping frequency and arranged so that there is no influence on normal fieldmeter observations The radio noise and impulse observation circuits are checked by applying modulated low level oscillator signals 10s on and 10s off to the antenna tube so these signals can be observed and assessed by the radio observation circuits as part of their normal operation The levels of the fieldmeter operational health drive and the operational health signal as well as the modulation of the radio noise and impulse signals may be observed by direct inspection of these signals at the 25w D type diagnostic connector The two radio signals shown on the monitor display have been compensa
49. ickly over the range 26 0 to 28 0kHz in 0 25kHz steps The signal processing software will pick out the peak response from within this band The various combinations appropriate to non activation and activation of the two levels of alarm can be worked through While this may usefully be done with personal radio communication between the operator of the Sensor Test Unit and another observing the Base Unit display it can be done by just the one operator to a set pattern with the performance checked by subsequent inspection of the data records Tests involving the impulse signals will take some time because of the need to make observations with a number of impulse signals spaced 130s apart and also spaced 90s seconds apart The test procedure and parameter values provided with the Sensor Test Unit is described fully in Annex 1 A1 3 3 8 3 3 Base Unit Testing Operation of the signal processing Base Unit may be tested using settable d c voltages which can be easily linked in to the 25w diagnostic connector on the circuit board of the Base Unit to check the performance of the Base Unit and its associated software without need for connection to the Sensor Unit To test the Base Unit the cable to the Sensor Unit must be disconnected so signals can be injected to the 25w diagnostic connector on the main circuit board in the Base Unit The connections for the 25w connector are listed in Figure 7 When the Sensor Unit is disconnected a head cable
50. imply to the cable at the remote location with no local earth linkage and good isolation within a plastic mounting box provides good isolation against lightning transients 4 8 Uninterruptable power supply The Uninterruptable Power Supply unit Riello UPS 650W provides regulated mains power supplies to the microcomputer and the Base Unit and from the Base Unit to the Sensor Unit This power supply includes battery back up about 100VAh to give continuing operation of the lightning warning system for about an 1 hour in the event of local mains failure Power consumption by the Base Unit Sensor Unit and LCD monitor is about 0 33A at 240V so about 80W 5 MAINTENANCE Although circuit diagrams and build and test procedure documentation is available it is recommended that for preference any damaged or inadequately performing items are returned to JCI for repair and servicing while alternative items are in use The need for any maintenance or servicing will be revealed by the operational health monitoring indications and or by testing with the Sensor Test Unit Although the fieldmeter section of the Sensor Unit is of robust construction its operation and or performance may be impaired if it suffers impact or mechanical damage or if debris enters the sensing region of the fieldmeter The following checks and cleaning may be safely undertaken by the user without adversely affecting instrument performance or sensitivity If satisfactory operation
51. ing of the Nitro Nobel system is 1 6V User Manual DRAFT JCI 504 Lightning Warning System Radio noise observations The bandwidth for observations between 3dB points is 0 5kHz centred on 27 0kHz The signal output for a continuous wave test signal of 0 1V p p at the peak frequency of the 27kHz passband via a 10pF coupling capacitor is 0 250V This test signal is equivalent to a peak to peak charge transfer of 1 0pC to the antenna The output voltage signal corresponding to the threshold setting of the Nitro Nobel system is 0 55V Calibration of radio signal sensitivity from the antenna is conveniently achieved by capacitive coupling from an oscillator of measured peak to peak amplitude The charge sensitivity at any observation frequency is then the value of the coupling capacitor multiplied by the peak to peak signal applied to the capacitor from the oscillator A test procedure is described in Annex Al An alternative approach is to calibrate with an impulse charge transfer With the low Q response of the 2 200kHz impulse observation channel the response to the quantity of charge transferred is twice that for continuous wave charge transfer This is because the continuous wave signal is symmetrical from the filtering and gain circuits into the detector stage whereas an impulse remains asymmetrical For the radio noise circuits the relatively high Q about 54 means that response to a individual impulse signals is relatively poor compared to a
52. inually optimizing the 27kHz operational health signal output The response to the operational health signals can be viewed in Test Mode with Health Check ON and the desired channel selected The target performance levels during the 10s periods of operational health testing are about 28dB for the impulse channel and 20dB for the noise channel The response generated by each period of application of operational health signal is used to provide compensation to the signals observed during the next period This enables the displayed observations to be viewed without influence of the operational health tests despite any slowly varying performance changes which may be taking place Because small transient signals are generated when the operational health signals are switched on and off these may be visible on the monitor display at around the 20dB level Comparison between signal response changes and the changes expected from operational health checks are characterised at 3 levels for each of the 3 observation channels electric field radio noise and lightning impulse signals good above 50 of expected poor acceptable but justifying attention between 25 and 50 of expected bad unacceptable and requiring remedial action below 25 of expected If the changes are not as expected then appropriate indications are shown on the computer monitor screen by flashing the right hand section of the alarm status panel ambe
53. is not restored by these operations then the instrument should be returned to JCI for repair or servicing DO NOT attempt any adjustments to the circuits as such actions will most probably adversely affect instrument operation If there is any visual evidence of dirt or contamination on any of the sensing aperture or the sensing region surfaces or if the zero reading has drifted or become unstable then the first action is to remove the front cover of the instrument There are two sets of 4 M2 screws around the middle of the instrument casing Carefully remove just the four M2x6mm stainless steel screws towards the sensing aperture end of the casing and leave the other four DO NOT undo the 6 M2 screws around the front edge of the sensing aperture Carefully remove the front casing to reveal the sensing surfaces and rotating chopper assembly The sensing surfaces and rotating chopper assembly should be inspected for any signs of physical damage or contamination Any debris User Manual DRAFT JCI 504 Lightning Warning System should be removed Contamination of the surfaces should be removed by washing in warm soapy water and rising well and or by using an aerosol spray cleaner The same actions should be applied to the inside of the front casing DO NOT undo the grub screws securing the rotor assembly to the motor shaft Such actions will necessitate full resetting of instrument operation at JCI When the internal structure of the sensing region is
54. is very short compared to the wavelengths of all signals to be observed The signals generated on the antenna depend on the charge induced by the electric field component of the radio signal The direct capacitance loading of the antenna depends on the capacitance between the tube and the shielded cable within around 150 200pF This capacitance is not well defined and would vary with mounting arrangements and position of the connecting cable inside To avoid observations being affected by this capacitance loading of the antenna and associated connections the philosophy has been adopted of using a virtual earth charge sensitive preamplifier for radio observations The feedback capacitance of the charge sensing preamplifier is made as small as compatible with sufficient capacitive gain at the maximum frequencies 200kHz to dominate the likely maximum antenna capacitance loading The small capacitance 1nF keeps the charge sensitivity relatively high and helps achieve a good signal to amplifier noise ratio so small signals can be observed The capacitance is however sufficiently large to avoid saturation of the preamplifier stage with lightning impulse signals up to several times the alarm threshold level The resistor paralleling the feedback capacitor is chosen to give a roll off of gain at the lowest frequency of interest 2kHz To avoid continuous electrochemical battery voltages at the antenna tube driving the charge amplifier outside its operating ran
55. lots can pass over the screw heads and then the shield lowered down on to the antenna tube using The operational health shield needs to be replaced after testing otherwise the fiedmeter health will show bad Experience shows that the zero reading remains adequately small in comparison to the values of electric field at which alarm conditions arise so it is not likely there will be any need to make adjustment of the zero setting A record of the zero can be noted and held at a noted time in the data records made in the test mode This will enable a check to be kept on any long term zero drift occasioned perhaps by contamination of the internal surfaces of the fieldmeter If any adjustment seems to be needed then this will be accomplished by adjusting the small potentiometer on the main circuit board in the Base Unit The Zero Check Chamber must be removed after zero checking and the operational health shield replaced to restore normal monitoring operation and the Test mode section of the menu left 3 8 3 2 Sensor Test Unit The Sensor Test Unit provides the two main capabilities a the check the functional performance of each observations channel b to confirm all the alarm threshold criteria A photograph of the Sensor Test Unit is shown in Figure 7 For use the Sensor Test Unit STU is mounted on top of the Sensor Unit with the 3 pillars guiding and aligning the aperture in the STU base to the sensing aperture of the S
56. lp facility to set date and time A menu provides options to restart the JCI501 software for entering MSDOS or for transferring archive data 3 2 Normal operation The monitor display during normal non alarm operation is illustrated in Figure 5 The main features of the display are also indicated The monitor display shows numerical values of electric field radio noise signal and lightning impulse signal occurrence together with graphical presentation of the variation of these parameters with time The graphical display develops down the display in relation to the time axis on the left This time will be the present time or alternatively the time relevant to the display during review of earlier observations The bipolar section of the graph on the lefthand side shows the atmospheric electric field with the 3 threshold levels marked The section on the right shows the radio noise purple and the radio impulse blue signals together with the risk threshold level marked at 0dB The panel down the middle of the display shows records of the alarm status with tracks reporting the operational health of each observation channel and whether operation is in the normal or test mode Below the graphical display menu facilities provide opportunity to adjust the scales of the display and to review observations in full detail over an extended period In the middle of the display above the graphs is a panel reporting the present alarm status green flashi
57. m the radio test signal output socket to a 50mm Terry clip around the antenna tube mounting the Sensor Unit The unit is switched on by the switch near to the double PP3 battery compartment LEDs on the front panel indicate green for satisfactory battery conditions User Manual DRAFT JCI 504 Lightning Warning System and red if the batteries need to be replaced Active values of the parameters are indicated by red LEDs associated with parameters shown on the panel display The values of the parameters provided by the Sensor Test Unit are Electric field values as equivalent ambient atmospheric electric field values with an antenna tube mounting height of 2 0m are 1 3 1 7 3 2 3 8 4 2 4 7kV m These values are stepped through in the sequence 0 1 7 3 8 4 7 4 2 3 2 amp 1 3 kV m with a step time duration at each level of 5s Impulse test Frequencies 1 2 5 20 75 150 200 300kHz The pulse duration is 20ms duration to allow testing of 2 200kHz bandwidth Impulse test charge values 230 amp 410pC In the performance test mode these values are stepped through in the above sequence with a step time duration of 5s In the alarm criteria test mode time separations of 90s and 150s are available between pulses at 75kHz Noise test Frequencies 26 0 26 25 26 5 26 75 27 0 27 25 27 5 27 75 28 0kHz These frequencies are chosen to cover any variation of the nominal 27 0kHz centre frequency of the narrow band filter wi
58. monitor directly in kV m The radio noise and lightning impulse signals are displayed as dB values relative to the set threshold levels for these signals Software feedback to the Sensor Unit controls the sensitivity of the fieldmeter within 4 decades of operation An additional decade of gain can be introduced into the observation of the radio noise and lightning impulse signals The operational health of each observational channel of the Sensor Unit is monitored continually so early warning can be given of any loss of performance Operational health of each signal channel is assessed on the basis of low level signals created for each individual channel whose amplitude is continuously monitored and compared to expected levels 1 2 The operational health systems are arranged to have no influence on normal observations Software processing of the radio signals from the Sensor Unit involves interpreting the 2 200kHz band observation in terms of signal amplitudes of more than a set step change and outside a time separation that distinguishes lightning events of a single discharge channel event The radio noise signal is interpreted as the peak of the average over a set number of readings with this average decremented over a set time The settings of these times to match Nitro Nobel system operation are 50ms and 180s respectively Cross comparisons are made of electric field strength above set threshold levels radio noise intensity above a set th
59. mpulse events The 2 200kHz filter circuits are followed by a software switchable x1 x10 gain stage and the signal is then precision full wave rectified and processed by a fast rise 2us and relatively slow decay 20ms peak detector circuit Because of the low Q of the filter circuits the fullwave rectifier and peak detector circuit give a response to a single transient impulse to the antenna which is twice that for an equivalent peak to peak continuous wave signal The fullwave rectification makes the response equal for impulse signals of either polarity The overall gain through the 2 200kHz channel is about x2 5 x1 4 x1 4 x5 with an additional x10 option The 27kHz noise signal after a x5 gain stage is selected by a four pole Butterworth active band pass filter The overall Q of the filter circuits is about 55 to provide the required 0 5kHz bandpass characteristic between 3dB points The signal from the 27kHz filter circuit is subject to a software switchable x2 x20 gain stage followed by a set x20 gain stage With a common up front gain of x5 the overall gain through the 27kHz channel is about x5 x2 5 x2 x20 x500 with an additional x10 option For both frequency channels the signals are precision full wave rectified and processed by fast rise 2us and relatively slow decay 20ms peak detector circuits The unity gain buffered outputs are connected via 100 ohm resistors to the cable linking the Sensor Unit to the Base Unit for software
60. mstrenst txt serconst txt basecnst txt and headenst txt files respectively subsequently edited To change the constants in one of these files use EDIT to load it modify it and save it To make it take effect change to the program directory and use one of the file transfer utilities mstrname sercname basenum headnum e g the command sercname Serco copies the file serco ser to the program directory and renames it for use by the program The program looks for copies of mas ser bas and hed files in that order the mas file normally holds an entry for all the features that can be controlled by the user The ser file holds entries for serco specific features the bas and hed files hold entries for base unit and head unit specific features Any features missing from these last three remain as set by the copy of the mas file Now follows a summary of the program features as divided between the serconst basecnst and headenst files Serconst 10 file description 11 Alarm and information panel colours 12 Graphing colours 13 The alarm indicator text for various alarm states 14 Alarm flash rate control 15 Alarm panel information flash rate control User Manual DRAFT JCI 504 Lightning Warning System 16 Text in the information section of the alarm panel 17 Text appearing at the top of each channel graph 18 AlarmCriteria 19 2d array of records controlling thresholds reals and time delays reals for events 110 Array o
61. n through the listed levels in a predetermined sequence and scan rate 5s per level The values observed will be shown on the Base Unit display monitor and recorded These values enable confirmation to be made of the sensitivity of the fieldmeter over the relevant ranges of operation and the bandwidth and signal sensitivity of both the noise 27kHz and the impulse 2 200kHz radio observation channels The electric field values created are set to be equivalent to atmospheric electric fields assuming a 2m mounting height and use of the operational heath shield User Manual DRAFT JCI 504 Lightning Warning System The polarity of the electric field test levels can be changed using the rotary switch towards the back left hand corner of the underside of the unit The recording of test observations from known patterns of signal variations enables testing with the Sensor Test Unit to be carried out by a single operator without need for communication with a second operator at the Base Unit Alarm threshold testing Checking correct response to the various levels and combinations of signals associated is carried out in the normal mode of software operation Each parameter channel can be selected and set independently or in combination with others to provide signals just below and just above the various alarm threshold levels To ensure proper response to the peak of narrow bandwidth noise channel the approach taken has been to scan this signal fairly qu
62. n will be most productive when risk warnings are given and during and after local lightning activity Monitoring observations during lightning activity will allow note to be taken of the amplitudes of electric fields field steps radio noise and radio impulse signals and of the audible time delay between the occurrence of a lightning flash and the leading edge of the thunder to indicate distance of the discharge Comparison between predictions and experience will help guide development of improved threshold settings and User Manual DRAFT JCI 504 Lightning Warning System strategies for alarm warning This interaction will involve the review of data see 3 4 and possibly adjustment of operational and threshold settings 3 7 3 3 Shut down The system should be shut down by first closing software operation via the menu at the bottom of the monitor display not by just turning off the mains power supply Direct turning off of the power may cause some loss of data 1 close software operation by using the lt tab gt or lt control tab gt key to select the Program Escape panel then use the lt down arrow gt key to select enabled confirm this selection using the lt return key gt and finally pressing the lt escape gt key to exit from the running program 2 The display will show c At this point type shutdown and press return at this point turn off the power supply from the Uninterruptible Power Supply unit to the B
63. nd time by a time span for the display The lt tab gt key is used to move between the setting sections If the setting requirements cannot be met for instance because too early a date or time was chosen then the lt tab gt key will not move the cursor When the settings have been selected tab to the Review control panel at the right hand end of the menu so the display can be stepped through forwards or backwards or the display can be allowed to run on Return up to the current graph display by pressing lt esc gt 3 4 3 Test mode This mode provides a more basic level of display of Sensor Unit observations It allows the radio operational health facilities to be turned off and on Test mode is entered from the current display using the tab key to move the cursor across to the test panel and then pressing lt return gt The lt tab gt key can be used to move across the menu to the item of interest The options can be selected using the up or down arrows and then the lt return gt pressed to confirm and activate the selection At the right hand end of the menu there are options on the information to be displayed in the line below the menu remaining archive space fieldmeter health radio noise channel health or radio impulse health At return to current operation by pressing lt esc gt both the operational health checking is returned and the health compensation are automatically restored to on
64. nding operational health signals serial interface circuits with opto coupling isolation of RTS CTS RX TX signals to microcomputer 3 opto coupled signal lines for alarm status indication from the serial interface platform back to the local earth section LEDs indicating system operation normal satisfactory operation of the fieldmeter satisfactory operation of the radio noise monitoring circuits satisfactory operation of the lightning impulse observation circuits satisfactory operation of the computer software communications link and if the system is under test the software controlled features in the Sensor Unit are allowed to self set to default values in the event of serial data communication or software failure The local earth referenced part of the system includes the input power supply of 16V to the local earth section of the main and display circuit boards is used directly and to create a 5V supply RS 232 line drivers which are linked to earth isolated section via opto couplers circuits to receive opto coupled alarm status signals and to provide signaling voltages for alarm status lamps locally and remotely 4 5 Software signal processing 4 5 1 General The software for signal processing in the Arcom microcomputer operates in MSDOS The software is NOT suitable for operation in conjunction with any Windows operating system The software operates in a protected mode to provide direct use of 2M RAM The comp
65. ng amber and flashing red To the right above the graphs is a panel showing the alarm status of each of the three observation channels with the relevant threshold levels These change from green to amber to red according to the alarm status created from these channels If the operational health of these channels falls below their threshold levels then these sub panels are flashed amber of red In the top right hand corner is a display of the date and present time Electric field observations are displayed as local ambient atmospheric field values kV m This takes account of the observational factors of the local voltage sensitivity of the Sensor Unit and its mounting height above ground Checking and adjustment is described in Section 3 4 4 Radio noise and lightning impulse signals are displayed in dB relative to the set threshold levels for each of these parameters The LED indicators on the Base Unit panel summarise the operational and alarm status of the system The array of LEDs shows the status of the overall system as assessed by software the health of each of the three observational channels and the health of the serial data communications link between the microcomputer and the Base Unit In the lower part of the display the alarm warning lamps show the assessed risk of local lightning activity To the right of these are LEDs to indicate correct operation of any Remote Display Units connected Inspection and interaction with system operatio
66. nk is working then lack of transfer of readings could mean there is a problem with the ADC or the ADC multiplexor Such a conclusion would indicate a need to change to an alternative Base Unit and to get this one serviced 3 8 4 Adjustments The only user adjustment that may be needed is for correct interpretation of atmospheric electric field values in terms of the local voltage sensitivity of the Sensor Unit and its mounting height above the local ground as discussed in Section 4 2 1 A potentiometer is provided on the upper surface of the main circuit board in the Base Unit to enable the electric field displayed on the LCD to match interpreted values The values used in the risk assessment and in the monitor display are adjusted as discussed in Section 3 7 and in Annex 4 3 8 5 Formal calibration Calibration of the measurement performance of the JCI 504 involves quantitative measurement of the voltage sensitivity of the fieldmeter and the response of the radio noise and lightning impulse measurement circuits to antenna signals of measured amplitude and frequency with the accuracy of these measurements traceable to National Standards Procedures for this area described in Annex I A1 2 The relationship of the parameters measured to ambient lightning related parameters is considered in the present manual The interpretation of measurements in terms of lightning risk models that is the same as that used in the Nitro Nobel Lightning Forec
67. nmental conditions a JCI 131 mounted on top of a 2m tall antenna which picks up radio noise signals at 27kHz and lightning impulse signals over the band 2 200kHz The Sensor Unit is cable connected up to 200m to the Base Unit which is mounted in a convenient nearby monitoring building The Base Unit provides power supplies for the Sensor Unit links signals to the associated microcomputer and provides a basic display of readings and system operational status The microcomputer does all the analysis display risk interpretation and recording of observations and posts alarm status indicators on the Base Unit display The overall arrangement of the JCI 504 system is shown in Figure 1 The atmospheric electric field is measured by an electrostatic fieldmeter acting as a potential probe a known height above ground level This can be directly calibrated in local voltage so with the known probe height the volts per metre of the ambient atmospheric electric field is known The advantage of this approach is simplicity of mounting the avoidance of interference by ground level dust and debris and the enhancement of the effective sensitivity of the electric field measurement capability The JCI 131 fieldmeter used for electric field measurement is based on well tried proprietary JCI design features 3 4 These provide high useable sensitivity and long operational life Physical design features large gaps and long insulation tracking paths are based on
68. nuous wave test signal is symmetrical around zero in the filtering and gain setting circuits so the output from the detection circuit is 50 of the signal which arises from an asymmetric impulse peak signal With a c w test signal the output is 0 25V As a 100pC impulse input gives an output peak of 0 5V so the threshold for 315pC impulse should be set for 1 6V User Manual DRAFT JCI 504 Lightning Warning System Annex 3 SOFTWARE DIRECTORY TREE FOR JCI 501 SOFTWARE USED ON JCI 504 SYSTEM Directory PATH listing for Volume MS DOS 6 Volume Serial Number is 2349 AF5B ce EDIT BAT COMMAND COM CONFIG SYS WINA20 386 50 BAT FILESPCE EXE AUTOEXEC BAT GO BAT CORELDRV AL7ASPI SYS UNIDRV LST l l CATALOG DOS ANSI SYS MEMMAKER STS 501ARCHV 1998 MARCH 00000184 CSV 00000185 CSV 00000186 CSV 00000187 CSV EDIT EDIT COM EDIT HLP JCI501 JCI501 EXE SETUP TXT MENUFORM TXT MSTRCNST TXT SERCONST TXT BASECNST TXT HEADCNST TXT MSTRNAME BAT SERCNAME BAT User Manual DRAFT I BASENUM BAT RTM EXE l DPMII6BILOVL JCI501 IMG 1 ARCHNUMS TXT HEADNUM BAT MENURSCE SETUP JCI MENUFORM JCI SETUP SER MENUFORM SER RESOURCE MSTRCNST TXT 1 1 SERCONST TXT 1 BASECNST TXT HEADCNST TXT l 1 SERCO MAS SERCO SER 1 97121479 BAS 98011494 BAS i 97121478 BAS 1 97121462 HED 97121464 HED 97121463 HED l
69. o the top of the tube adaptor The Sensor Unit itself is easy enough to hold in one hand with the other hand used to make the 19w and earthing cable connections This is certainly an easier way to change Sensor Units for servicing with just say 300mm of the 20w cable and earth connection cable left hung out of the top of the tube assembly The Base Unit may be linked to one or two Remote Display Units to show the alarm status shown on the Base Unit via the 15w D type connector on the right hand side of the unit The alarm status lamps on the Base Unit include indication of satisfactory connection to the remote display and any LED failures in the remote alarm display The system is now ready for checking and for performance testing in preparation for starting normal system operation Checking operation and performance of the system should be as described in Section 3 3 1 3 2 amp 3 4 and in Annex Al 3 SYSTEM OPERATION 3 1 Start up Check the system has been installed and connected as described in Section 2 with reference to the overall general arrangement of equipment as shown in Figures 1 2 and 3 Switch on the mains supply to the Base Unit primary and computer units if these are separate and to the computer monitor On the Base Unit a green LED will indicate the mains supply is on As soon as mains power is supplied the power will be provided for the Sensor Unit and this will start operation Operation of the Sensor Unit will be indicate
70. ocessing computer Linkage between the two parts over large distances will most conveniently be by use of fibre optic cables Fibre optic multiplexor units can be mounted into the 25w D type serial data connectors on the two units The Greenwish Instruments CXM units will be suitable for communications for distances up to about 8km Operation of the multiplexor units is powered by a 12V supply via pin 9 of the 25w connector on each unit The multiplexor on the power supply and signal handling unit needs to be set DTE and on the computer unit to be set DCE The Base Unit internally comprises 16V and computer power supply units an Arcom SBC GX533 single board mirocomputer running MSDOS 7 1 a main signal processing board in the body of the unit and a display board inside the cover Both the main and display circuit boards are divided into two areas a local earth referenced section and an earth isolated signal processing section that is earthed at the Sensor Unit The local earth referenced section provides opportunity to link the alarm status display to up to two Remote Display Units via a 15w D type connector The circuits to operate each of the two Remote Display Units include arrangements to detect whether the Remote LEDs are operating correctly and to only display the associated LEDs on the Base Unit cover if these are operating correctly A single Remote Display Units may be connected directly to the 15w D type connector on the Base Unit case
71. of direct visual back up in the event of computer failure Both the radio noise and the lightning impulse signals are shown on the monitor display as dB relative to the set threshold levels The noise signal is derived from software processing of noise signals and has the same 180s signal decrement time constant as applied in operation of the Nitro Nobel system The Base Unit includes LEDs to show the operational and health status of each observational channel and red yellow and green LEDs showing the assessed alarm warning status User Manual DRAFT JCI 504 Lightning Warning System 1 2 Background The JCI 504 system is designed as a replacement for the Nitro Nobel Lightning Forecasting System VSL2 1 The present system covers the same basic operational features at the Nitro Nobel system i e warning based on simultaneous observation of electrostatic field radio noise and lightning impulse signals It does this in a way that provides a better user appreciation of signal activity with recording of observations and the ability to inspect previous signal history The system provides greater operational reliability easy interchangeability of units and easy opportunity to modify and enhance warning criteria in the light of experience The JCI 504 system is an enhanced version of the JCI 501 Lightning Warning System 2 The construction of the Sensor Unit has been improved in the light of developments with the JCI 131 Adverse Conditions Electrostatic
72. of the sensing aperture relative to the ambient electric field If for example the two field components are in directions to add then the atmospheric field can be derived as E E d h 1 d h As d h is normally small the influence of this effect is small The effective diameter of the JCI 504 Sensor Unit is about 0 17m 170mm and the mounting height 2m The atmospheric electric field is hence about 0 085 E The actual local voltage sensitivity of measurement can be checked in situ by applying a calibration voltage to the whole fieldmeter assembly see Annex 1 3 The local ambient atmospheric electric field is then obtained knowing the mounting height of the sensing aperture as above Where the Sensor Unit is mounted other than above a large scale plane ground area well clear of User Manual DRAFT JCI 504 Lightning Warning System any buildings or earthy projections it will be appropriate to interpret the electric field measurements at the Sensor Unit in relation to the geometric arrangement of the surroundings This can be done with computer modelling calculations but this may be difficult and lacking conviction unless done in complex three dimensions An alternative and simpler approach is to normalise readings in relation to atmospheric electric field values measured at the same time on a nearby large flat area of ground with stable atmospheric conditions e g with a clear blue sky situation when the ambient field is steady and ty
73. oftware operation via the User Menu Check that the operational health testing is off Compensation and the time constant TC of radio noise observations will be turned off automatically Set the graph time span for 1 or 2 minutes The following automatic test sequences are initiated by pressing the auto test pushbutton The LEDs on the panel display will show the values of the test parameters as these are scanned through a Automatic scan through electric field values Field values are stepped up from zero and then back down with values 0 1 7 3 8 4 7 4 2 3 2 amp 1 3 kV m b Automatic scan through impulse test frequencies to 300kHz at the high charge level 410pC followed by a scan through frequencies 1 to 300kHz at the lower quantity of charge 230pC c Automatic scan through noise test frequencies at the high charge level 2 6pC followed by a scan through range of frequencies for the low quantity of charge 1 8pC The results of observations during the above scans can be seen directly on the monitor display and are also recorded so they can be replayed for any more detailed checking felt desirable STAGE 2 TESTS Carried out in Normal Mode during quiet atmospheric conditions The following tests are carried out by pressing the Select pushbutton During Stage 2 testing noise signals are scanned quickly over the 26 0 28 0 frequency range so that the software will find the correct peak value as the maximum over the range
74. pically around 100V m An appropriate adjustment factor can be included in the instrument application file The relation of local ambient atmospheric electric field values to the charge altitude and distance characteristics of thunderclouds may be modelled with Spreadsheet calculations treating the cloud charges and their image charges below the ground plane as dipoles 4 2 2 Sensor unit Antenna and antenna circuits Lightning discharges produce radio impulse signals whose energy is distributed throughout the radio spectrum Signal intensity is highest at the lower frequencies 4 because most of the energy is concentrated there in relation to the long channel length of lightning discharges and because low frequency radio signals propagate long distances with low attenuation Signal strengths as electric fields in uV m as a function of frequency for day and night summer and winter are illustrated in Figure 5 Radio noise and lightning impulse signals are picked up by the 2m length vertical tube mounting the Sensor Units acting as an antenna The tube encloses the multicore cable linking signals from the Sensor Unit back to the Base Unit and the lead bonding the Sensor Unit to local earth but the antenna tube itself is well insulated from earth A conical earthed shield is mounted under the Sensor Unit to minimize the coupling to the antenna from any signals arising from operation of the fieldmeter operational health system The antenna
75. previous experience of overcoming problems of operation in wet environments 2 5 Radio noise and lightning impulse signals are picked up by the electrically isolated antenna tube which also supports the Sensor Unit above ground level Radio noise signals at 27kHz and impulse signals within the 2 to 200kHz band indicate the level of lightning activity around Low frequency radio signals travel with fairly low attenuation so lightning activity can be detected at large distances These signals are fully processed by circuits mounted within the casing of the Sensor Unit that is created out of and incorporates a JCI 131 fieldmeter Observations pass through a single multicore cable down the inside of the antenna tube and to the Base Unit The signal values observed are independent of cable length User Manual DRAFT JCI 504 Lightning Warning System Measurement of the intensity and polarity of the electric field and of the amplitude of the radio noise and lightning impulse signals by the Sensor Unit are multiplexed in the Base Unit into a 12 bit ADC and communicated at up to 100 sets of readings each second to a microcomputer for analysis display and data recording Software processing of signals from the Sensor Unit interprets these as ambient atmospheric electric field values in volts per meter and as induced electrical charge change for the radio noise and lightning impulse signals Electric field values are displayed on the Base Unit and on a computer
76. r or red relating to individual observation channels The health status indicator traces are shown in the central section of the graphical display and included in the stored current data and in the long term data archive User Manual DRAFT JCI 504 Lightning Warning System storage If the baseline level for the impulse or noise signals rises to a point where sensible assessment of operational health is not feasible this is indicated by the middle acceptable health indication and the user will be able to see that the signal levels on the monitor display are very high This condition would probable only arise in practice if the radio environment became quite inappropriate for meaningful measurements for example as a result of operation of a transmitter nearby with significant components within the 2 200kHz frequency range It may also arise during performance testing for example with the Sensor Test Unit as noted in Annex 1 4 7 Remote alarm display unit The remote alarm display unit provides a repeat of the alarm warning levels on the Base Unit with green amber and red LEDs in a wall mounted plastic box Connections are provided at a 15w D type connector on the Base Unit sufficient to operate two Remote Display Units independently The voltages across the remote LEDs are monitored at the Base Unit so failure of remote lamps or the cable connection can easily be identified at the main monitoring position Connecting the indicating lamps s
77. radio noise and lightning impulse signals are compared to set threshold levels in software in relation to the defined risk criteria to determine the alarm status level see Section 1 2 The alarm criteria settings file holds such information as the threshold values of electric field the threshold level of radio noise signal the threshold level above which a lightning impulse is considered an event the time separation between lightning events to be used for judging significance the gain settings used in the sensor unit the height of the fieldmeter sensing aperture and the fieldmeter sensitivity as a potential probe These parameters are able to be adjusted after use of an authorised password 4 6 Operational health monitoring Satisfactory operation of each observation channel of the Sensor Unit is monitored by application of modulated signals which directly check the operational health of each observation channel during normal system operation Satisfactory functioning of the fieldmeter operational health checking can be tested if the front casing of the Sensor Unit is partly or fully covered by a clean metal shield disc so that modulation of the voltage of the Sensor Unit does not produce any corresponding variation of fieldmeter signal After operating for some 10s or so poor and then bad operational health will be indicated on the monitor display Operational health of the radio noise and impulse circuits are checked by injecting
78. re must be shut down before transfer can be initiated so this needs to be at a time when no lightning risk will be relevant to operations Connect a null modem serial link cable between the 9w D type connector on the side of the JCI 504 Base Unit to either the serial port of the target computer or to a USB to serial adaptor This cable must be a null modem cable The JCI 501 software is shut down as described in Section 3 3 The JCI software 504SEND installed in the Base Unit computer needs to be started by typing lt 504send gt at the c prompt When the JCI 504 archive transfer software is started on the Windows operating the display will confirm that communications have been established and provide guidance on how to select files for transfer Before transfer can start the data transfer communications port may need to be selected If the computer has just one or two serial ports these will be identified as COM1 and or COM2 If connection is made via a USB serial adaptor then the port can be identified via Control panel Device manager Ports and may be COM4 or higher Archive data transfer to a Windows computer is controlled from the Windows end using the guidance and downloaded directories when operation of software jci504ad is started If any problems arise during data transfer it is best to just rerun the software In the Base Unit computer Arcom SBC GX533 the archive data is stored in section e of the hard drive Thi
79. reshold level and the frequency of occurrence of separate lightning events above a set threshold level to determine whether there is no significant risk an amber risk threat or a red alert threat These alarm status levels are displayed by green amber or red lights on the Base Unit and on the computer monitor display and are also available for relaying to Remote Display Units Observations are displayed on a computer monitor as graphs of ambient atmospheric electric field radio noise and lightning impulse occurrence versus time Additional traces show the operational health status of the system and the status of interpreted lightning warning risk These observations are stored to the computer hard disc and provide opportunity for direct roll back for inspection of earlier records In parallel to this observations are stored to a large capacity recording medium for long term archive back up and separate analysis Archive data storage space is minimised by averaging data over time intervals which can be set at three levels in relation to the amplitudes of signals on individual channels passing any of the set threshold levels for individual observation channels The Base Unit includes LCD presentations of the electric field and the radio noise observations The electric field presentation in kV m parallels that of the computer monitor display and is shown interpreted as values of ambient atmospheric electric field This display provides a degree
80. ring review of earlier records 4 5 6 User menu A menu at the bottom of the display provides easy guidance to access a number of functions The structure of the menu system is illustrated in Figure 7 The main features of the menu facilities are graph menu for setting the timescale of the present display and for review of earlier records by selected date and time and by paging or stepping forwards and backwards test menu for selection of test operating conditions Functions of the menu are selected using the lt tab gt or lt shift gt lt tab gt keys and then pressing the lt return gt key to implement the action The lt esc gt key is used to move back up the menu structure Where values are required for selection for example dates and times for reviewing graphs these may be typed in directly Alternative display settings can be selected during operation It will also be possible to arrange alternative data storage settings such as the frequency at which observations are stored according to set threshold levels Settings will be held in a text type file and recallable by description Appropriate standard settings are held in a default file 4 5 7 File information The settings concerning the interpretation display and storage of observations are held in separate text files to determine the following 4 classes of information User Manual DRAFT JCI 504 Lightning Warning System the way data is displayed and stored
81. rom the Sensor Unit over each 10s period This approach avoids interference from real noise signals The 20ms time constant of the peak detector circuits makes it very likely that the signal from the Sensor Unit will return to its baseline level between individual pulses of real noise If the change is not as expected then an appropriate indication is shown on the computer monitor screen The lightning impulse signal channel is checked by switching a signal at about 100kHz under software control so that a corresponding change can be looked for in the observed impulse signal The impulse channel sensitivity is much lower than that of the 27kHz channel and the 27kHz operational health signal makes little contribution to the impulse channel observations The circuits for the two operational health test oscillators are on the same PCB as the radio observation circuits They are however well segregated and shielded from the radio detection circuits to minimise cross talk It is noted that although the centre frequency of the 27 0kHz filter is very stable it is not so easy to make an oscillator with both and equally stable frequency and signal amplitude The oscillator frequency is hence dynamically controlled by software via green led illumination of a light dependent resistor in the frequency determining part of the oscillator circuit Control is exercised via a DAC voltage applied to the led to vary the illumination and the software pursues a strategy of cont
82. s 7 5V and 7 5V supplies are generated for the Sensor Unit earth linked sections of the main and display circuit boards differential input buffer amplifiers signal to signal earth for each input channel for the fieldmeter radio noise and lightning impulse signals two DVM circuits on the display board to show fieldmeter and radio noise observations on 3 digit LCDs with decimal point setting according to sensitivity range User Manual DRAFT JCI 504 Lightning Warning System software controlled multiplexor input to a 12 bit ADC to select measurement of fieldmeter signal radio noise signal and lightning impulse signals 4 software controlled DAC analogue signals One of these is used to create a signal used in the Sensor Unit to adjust the 27kHz operational health frequency to match the centre frequency of the filter is the 27kHz observation channel The second is used to create a modulation on the fieldmeter signal proportional to the strength of the fieldmeter operational health level signal This enables the JCI 501 software to match to the operational health facility provided in present JCI 131 fieldmeters 8 digital control signals are connected to the 4 data channels in pairs One pair is used to select the sensitivity range for the fieldmeter On both the radio noise and the impulse signal channels 1 digital control bit is available to provide x10 gain enhancement These bits are also used to provide x10 attenuation of the correspo
83. s derived by software from the fieldmeter reading with account of mounting height sensitivity range etc 3 digit LCD presentation of radio noise signal level in dB from software calculations green LED indication of System operation normal yellow LED indication if System isin test mode green green and yellow LED indication of fieldmeter operational health as good poor and bad green green and yellow LED indication of radio noise operational health as good poor and bad green green and yellow LED indication of impulse operational health as good poor and User Manual DRAFT JCI 504 Lightning Warning System bad green LED indication of microcomputer software operational health green LED indication of mains power supply ON OFF green amber and red LEDs indicating alarm state indicator LEDs are provided of the alarm state indication for each of the Remote Display Units These only light up if the Remote display is connected and working properly The Base Unit can be configured as a single unit or into 2 separate units for example if it is desired to have the displays remote from the unit providing power supplies to the Sensor Unit and displaying all the status indications and basic electric field and radio noise values For this separated situation one unit houses the circuits providing power to the Sensor Unit and the circuits receiving data from the Sensor Unit and digitizing this for communication with the pr
84. s may be located by the following actions after closing down the JCI 501 software to enter c For example to find the data recorded for August 2007 C EA lt return gt Ei dir lt return gt CD 2007 lt return gt 2007 DIR lt return gt CD AUGUST lt return gt DIR lt return gt 3 7 Adjustment of settings 3 7 1 Introduction Settings are held in separate text files to determine the following 4 classes of information the way data is displayed and stored the performance features of the instrument sections involved in electric field radio noise and lightning impulse measurements the way measurements are interpreted from their hardware application User Manual DRAFT JCI 504 Lightning Warning System risk assessment level It is important that care is taken in changing any entries in these files as errors will affect the interpretation of observations and the ability of the system to provide warnings as intended Read only default files are provided so these can be used as models if problems are experienced during editing of user versions of files Information on the performance characteristics of the system is held in a number of software files A default set is held in a master file mstrenst txt Separate default files are held for a default Sensor Unit headCnst txt for a default Base Unit baseCnst txt and for default application features serconst txt These default files are held as read only files The
85. s to be run out to the outside through a suitable wall opening at least 30mm clear diameter The cable needs to be connected to the 19w connector which is mounted on insulation on the top right hand side of the Base Unit Note that no connection should be made or allowed between the casing of the cable connector and the local building earth earth connection is made at the location of the Sensor Unit Outside the building the cable may be run out to the position selected for mounting the Sensor Unit Provide such mechanical protection for the cable as is appropriate along the cable length 2 3 Set up Sensor Unit The Sensor Unit assembly comprises as shown in Figure 2 Sensor Unit antenna tube earth mounting spike earthing connection cable earth bonding spike 3 insulating guy lines and ground support spikes Installation involves the following steps 1 Insert base support spike vertically into the ground at the chosen location and drive down as far as appropriate for a secure mounting Protect top edge of mounting tube during driving for example with a piece of wood 2 Insert bottom insulator into base support spike 3 Feed cable from Base Unit up through side aperture in base support spike and up through insulator 4 Attach operational health shield to base of Sensor Unit if not already in place 5 Attach earth bonding lead about 4m long to one of the M3 screws securing the 19w connector on the Sensor Unit 6
86. signals at at about 100kHz and at the peak of the 27 0kHz filter passband for periods of 10s on and 10s off The 100kHz signal frequency is chosen as sufficiently high that interference to the much more sensitive 27kHz channel will be small As the 27kHz filter is of such narrow bandwidth the centre frequency may change a little between Sensor Units and with temperature The 27kHz frequency of the noise operational health oscillator is hence adjusted under software control to hunt for and find the peak of the filter passband The operational health signals are output via capacitive coupling from the oscillators and linked to User Manual DRAFT JCI 504 Lightning Warning System the antenna via a spring loaded connection to the top of the antenna tube This link is separate and isolated from the link back into the radio observation circuits Thus the health check covers the whole functional operation of each radio observation channel from the ground leakage impedance of the antenna tube to the connection into the Sensor Unit circuits and operation of the signal processing circuits The oscillations are present while the appropriate control lines are LO The radio noise signal channel is checked by switching a 27 0kHz signal under software control so that a corresponding change can be looked for in the radio noise signal Assessment of signal levels with and without the operational health signals is based on the signal baseline level as received direct f
87. t range of 0 to 4 096V The radio noise and impulse signals from the Sensor Unit are unipolar and prospectively within a range 0 to 5V For these signals an input gain is provided close to 0 8 so the 0 5V input matches to the 0 4 096V range of the ADC The two sections of circuitry on the single Base Unit PCB are electrically well segregated and the signal processing section is isolated from the local earth to over 1kV voltage withstand The signal processing section is linked to earth only at the Sensor Unit This provides immunity to earth voltage differences over the connection distance between the Sensor Unit and the Base Unit and offers some protection against lightning impulse damage Signals are opto coupled between the locally earthed and Sensor Unit earthed section of the Base Unit PCB Any measurement equipment connected to the signal processing board during normal operation must recognise that this circuit is NOT locally earthed so no cross links to local earth are permissible The two segregated sections of circuitry are bounded by Earth and OV tracks on both sides of the PCB This also applies between the isolated sections of the opto couplers and between the winding connection points of the isolated section power transformer The electrically isolated area of the main circuit board includes the following power supplies of 12V and 12V for the Sensor Unit via a 16V input dc dc isolating converter From these supplie
88. ted to avoid showing the health modulation signals except in the test mode of operation If the amplitude of the health checking signals differs from that expected then appropriate indication is made on the monitor display to show whether operation is doubtful amber but can continue for a time with reduced confidence in performance or whether operation is unsatisfactory red and immediate remedial action is needed The signals used for health monitoring are small compared to the alarm levels and have no influence on alarm status assessment Health checks are also made and recorded on the cable link to the Sensor Unit and on the serial communications link between the computer and the Base Unit 3 8 3 Performance testing 3 8 3 1 Fieldmeter Zero Reading A basic test on the electrostatic fieldmeter section of the Sensor Unit is checking the zero reading While operating in the test mode a zero electric field environment is achieved by placing the Zero Check Chamber over the fieldmeter sensing aperture In this condition the reading of the fieldmeter as shown numerically on the monitor display is the zero reading Before User Manual DRAFT JCI 504 Lightning Warning System testing it is necessary to remove the operational health shield This can be achieved either by taking out the four M4 screws securing the shield or by slackening these screws and then rotating the shield slightly so the mounting keyhole s
89. th indicating signal It is this later signal that is used as a basis for assessing the health of the fieldmeter in the JCI 504 system User Manual DRAFT JCI 504 Lightning Warning System A1 2 3 Sensor Unit height The height of the fieldmeter sensing aperture above local ground level is measured in m This gives the height parameter for the Sensor Unit application file A1 2 4 Radio noise observations Bandpass frequency characteristics of radio noise observations The bandwidth between 3dB points is to be 0 5 0 1kHz centred on 27 0 1 0kHz Charge sensitivity for radio noise observations The signal output of the radio noise channel is to have a value of 0 250 0 05V at the peak frequency of the 27kHz passband for a 0 1V peak to peak continuous wave input signal coupled via a 10pF capacitor equivalent to 1 0pC to the antenna Radio noise threshold setting A signal output of 0 55 0 1V corresponds to the 2 2pC noise threshold setting as in the Nitro Nobel system Noise channel operational health level checking A signal output of 0 05V 0 02V will be observed during the active periods of both the 27kHz and 2 200kHz operational health oscillators This will show a displayed signal with operational health checking ON in the Test Mode around 20dB A1 2 5 Impulse signal observations Bandpass frequency characteristics of lightning impulse observations The bandpass frequencies between 3dB points are to be 2 0 5 to 200 50kHz
90. th temperature and to give adequate detail for assessment of the frequency pass band Noise test charge values 1 8 amp 2 6pC In the performance test mode these values are stepped through in the above sequence with a step time duration of 5s In the alarm criteria test mode the above frequencies are stepped through with a scan duration around Is over the 9 set frequencies for a selected level of charge transfer Performance checking The performance of each of the 3 observation channels electric field radio noise and radio impulse is checked with the Base Unit software operating in Test Mode In this mode each of the observation channels can be tested individually or at the same time as other channels Each channel can be triggered by its Step pushbutton This will cause the signals for that channel to scan through the listed levels in a predetermined sequence and scan rate 5s per level The values observed will be shown on the Base Unit display monitor and recorded These values enable confirmation to be made of the sensitivity of the fieldmeter over the relevant ranges of operation and the bandwidth and signal sensitivity of both the noise 27kHz and impulse 2 200kHz radio observation channels The electric field values created are set to be equivalent to atmospheric electric fields assuming a 2m mounting height and use of the operational heath shield The recording of test observations from known patterns of signal variations enabl
91. tric field measurements with pins 6 amp 7 for sensitivity range indication pins 10 for radio noise measurements with pin 11 for x10 gain control and pin 15 for impulse signal measurements with pin 16 for x10 gain control The performance figures can also be displayed graphically and numerically on the computer monitor while the software is operating in test mode The performance values are held in instrument files which are identified by the serial number of the Sensor Unit serial number hed one for each individual Sensor Unit These are all held in the resources subdirectory The program uses one of these files which has been copied to the file headcnst txt held in the program directory A1 2 PERFORMANCE ASSESSMENT A 1 2 1 Atmospheric electric field The atmospheric electric field is measured by the Sensor Unit fieldmeter acting as an earthed probe giving an output proportional to the local voltage in the vicinity of the fieldmeter sensing aperture The electric field at the sensing aperture is close to E V d So for a fieldmeter with an operational health shield around with a diameter of 0 17m the electric field observed at the fieldmeter will be about 6000V m per 1000V At a height above ground h this will be equivalent to an atmospheric electric field of 1000 h V m The electric field sensitivities of each of the 4 ranges of the JCI 131 fieldmeter are preset by the manufacturer to be equivalent to 2 0V output for
92. truments with no earthing of the rotating chopper Paper presented at Electrostatics 1999 Conference in Cambridge March 29 31 1999 Inst Phys Confr Series 163 p443 446 5 J N Chubb I E Pollard An instrument to measure electric fields under adverse conditions Static Electrification 1975 Inst Phys Confr Series 27 1975 p182 6 F E Terman Radio Engineering McGraw Hill 1937 7 C L Thomas POTENT A package for the numerical solution of potential problems in general two dimensional regions Proc Confr of Software for Numerical Mathematics and its Applications Loughborough University April 1973 p315 London Academic Press User Manual DRAFT JCI 504 Lightning Warning System Figure 1 Overall arrangement of JCI 504 System Sensor Unit fieldmeter operational health shield cable connector and earthing connection antenna tube antenna support insulator _ Barthing terminal cable exit ground support spike Arrangement of Sensor Unit Remote Display Remote Display Unit Unit Sensor Unit Splitter box E RS232 output for linkage to Windows computer 19w cable RS232 serial dara link main Base Unit E FEI Monitor Keyboard maine power supply Connections of Sensor Unit with main and computer Base Units Sere a User Manual DRAFT JCI 504 Lightning Warning System Figure 2
93. ugh the NN system is about 70 000 although combination of gain factors for IC10 11 13 14 amp 15 suggests an overall gain figure nearer a million It maybe that the filter circuits are well below unity gain so there is some uncertainty in gain figures In the JCI 504 system the preamplifier connected to the antenna is a virtual earth charge detector with a 1 0nF feedback capacitor An input charge change of 2 2pC will be equivalent to a source voltage change of 2 2mV With a total basic gain at 27kHz of x500 as a gain sequence of x5 x2 5 x2 x20 preceding detection an input charge change of 2 2pC will give an output of 500x0 0022V 1 1V The JCI 504 system has an additional x10 software switchable gain available Calibration of the 27kHz signal channel of the JCI 504 is by a 0 1V peak to peak signal at the centre of the bandpass frequency of the 27kHz channel Input is via a 10pF capacitor so 0 1V p p signal gives 1 0pC charge change A continuous wave test signal is symmetrical around zero in the filtering and gain circuits so the output from the detection circuit is 50 of the peak to peak signal A continuous wave test signal of 1pC p p thus gives an output of 0 25V For a 2 2pC signal the threshold voltage should be set at 0 55V If an impulse charge transfer is used for calibration then a 100pC charge transfer is observed to give an output signal of 0 5V peak on the 27kHz channel which interestingly is the same peak output as is observe
94. uter used on the present system is an Arcom Control Systems Ltd SBC GX533 single board microcomputer This is based on AMD Geode GX embedded 400MHz CPU with ports for 3xRS232 2xUSB 2 0 IDE for HDD FDD PS2 keyboard VGA monitor The operating system is MSDOS 6 22 A 1 44M floppy disc drive and a 40G HDD have been added The hard disc drive is partitioned as two 2G areas the most that could be supported by the MSDOS 7 0 software One RS232 port is used for data transfer to and from the circuits of the Base Unit interacting with the Sensor Unit A second RS232 port can be used for serial data transfer to an external PC microcomputer with a Windows operating system The following steps will configure the system for the Arcom unit preconfigured with an MSDOS 7 0 operating system and will provide the startup menu s and 504Send application for archive transfer The following files should be located in the same directory with the following notes User Manual DRAFT JCI 504 Lightning Warning System l 504Send exe the archive transfer software for use with the JCI504 Archive Downloader software 2 CONFIG SYS overwrites the default DOS Config sys to provide a menu at startup and options for the autoexec bat file 3 AUTOEXEC BAT overwrites the default DOS Autoexec bat to provide a menu after use of the 501 software and 504 archive transfer software Copy these files onto a floppy disk and insert it into the JCI504 then use the following command to
95. ve alternative risk criteria 1 Electric field E gt 1 5 kV m amp Noise gt Noise threshold amp 1 lightning event 2 Noise gt Noise threshold amp 2 lightning events lt 100s 3 Electric field E gt 3 kV m amp 1 lightning event 4 3 lightning events lt 100s between successive events 5 Electric field E gt 4 5 kV m As discussed in Annex 2 the threshold noise and lightning impulse signal levels of the above warning criteria are expressed as equivalent electrostatic charge transfer to the antenna as Noise threshold 2 2pC Impulse threshold 315pC User Manual DRAFT JCI 504 Lightning Warning System The threshold electric field values 1 5 kV m 3kV m and 4 5 kV m are the readings of the fieldmeter interpreted as the local atmospheric electric field to the ground The above threshold criteria were set to match those used in the Nitro Nobel system 1 Since the character of lightning varies around the world and may depend upon regional meteorological conditions it may be more appropriate to use different threshold levels and alternative criteria at particular installations These may be set via the software facilities Appropriate values may be judged on the basis of practical experience by comparing the occurrence of warning indications with visual and sound observations of actual lightning events The time difference between the flash and the initial sound of thunder gives the range from the speed o
96. warning appears on the monitor display Provision of a continuous signal to either the fieldmeter or the noise circuits will over ride the head cable diagnostic and allow testing with combinations of simulated signals A handheld digital multimeter may be used to check the amplitude of the test signals on the appropriate pins of the 25w diagnostic connector at the top of the left hand side of the Base Unit see Figure 3 to be measured and to provide the basis for comparison with the values displayed on the microcomputer monitor screen and on the electric field and radio noise LCDs The signal levels corresponding to ambient atmospheric electric and radio field strengths are noted in Section 3 2 1 and Section 3 2 2 3 8 3 4 Remedial actions In the event that operational health tests or regular system performance tests see Annex and Section 5 show some deficiency in performance it is appropriate to seek likely causes before replacing any units with alternatives held in reserve A necessary first step is to identify the nature and location of the problem is it a loss of capability in or at the Sensor Unit or is it a problem in the Base Unit User Manual DRAFT JCI 504 Lightning Warning System For instance loss of both radio noise and lightning impulse response capability indicated by operational health signals but not fieldmeter response might be due to short circuiting of the antenna tube to earth Appropriate first steps
97. will be a visual inspection of the Sensor Unit mounting arrangements and b a resistance measurement to earth This might be followed by lifting the Sensor Unit off the antenna tube and checking if the spring loaded contacts are making proper contact with the top edge of the top edge of the antenna tube If this appears satisfactory then it will be appropriate to try tests with the Base Unit Tester If the Base Unit tests satisfactorily then it will be appropriate to check the cable connection This may be done by bringing the Sensor Unit close to the Base Unit and interconnecting the two by a separate short length of cable In the event of loss of electric field measurement capability a first step might appropriately be visual inspection of the sensing aperture to check a if the chopper is rotating and b if there is any significant amount of dirt or debris in the sensing region A good sluice out of the fieldmeter sensing region with fresh warm water with the sensing aperture looking down may well be helpful Alternatively the front part of the Sensor Unit casing may be taken off to allow easier inspection and clearing out and washing of the fieldmeter parts see also Section 5 This will be easier with the Sensor Unit taken off the antenna tube and disconnected from the 19w and earth bonding cables A first point to check is whether the Base Unit LED indicators show the serial communication link is working satisfactorily If the communications li
98. y of operational and alarm status 2 A Base Unit comprising 2 units one that includes all the circuits and power supply for supporting operation of the Sensor Unit and front panel display of operational and alarm status and the second a separate unit linked to the first by a normal or optic fibre RS232 communication that includes the microcomputer keyboard and LCD monitor This second unit may be positioned up to a few kilometers away The Base Unit is best located at a position suitable for cable connection out to the Sensor Unit with mains power supplies available and preferably with easy viewing by the operational staff needing to take action in the event of lightning warning The unit may be desk or wall mounted wall mounting provides easier viewing of indicator LEDs If the microcomputer is used inside the Base Unit then there needs to be a suitable support surface within a meter or so for the associated keyboard and LCD display monitor For wall mounting it will be convenient to mount two horizontal battens on the wall spaced about 350mm apart near the upper and lower edges of the Base Unit box The box may then be suspended by hanging it over the heads of two screws spaced at 250mm centres with heads no loner than 10mm diameter to match the holes in the back surface of the box The battens may also usefully be used to provide support for the cables from the right hand side of the Base Unit User Manual DRAFT JCI 504 Lightning Warning S
99. ystem If the microcomputer and its display are to be used at a distance from the primary Base Unit then suitable provision needs to be made for RS232 communications between this and the Base Unit The baud rate of communications is 9 6kb so for distances more than a few tens of meters it will be necessary to use optic fibre communication Only two optic fibres are required These can be linked to the serial port on the signal processing Base Unit and to the serial port of the microcomputer using standard modem transceiver unit for example by Greenwich Instruments Power for the optic fibre units is made available via pin 9 of the 25w D type connector A 50 125 micron glass fibre optic cable is recommended for long distances For long term continuous operation it is appropriate to take the mains power supply from an Uninterruptible Power Supply Unit UPS This should be positioned close to Base Unit Where the microcomputer base unit is separated from the primary Base Unit a separate UPS should be used These UPS units may be cabled to suitable mains power supply via IEC plug and socket connectors but do not switch on yet The earth bonding point on the bottom right hand side of the Base Unit must be connected to the local building earthing point Connect the PS2 keyboard and the monitor display mains supply and VGA input to the connectors on the right hand side of the Base Unit The cable between the Base Unit and the Sensor Unit now need

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