Design and Manufacture of Testing Equipment for Switchgear
Contents
1. Fig 17 Test Results Database The test computer equipment is housed in a modular 19 rack mount system shown in Fig 18 null 4 e HU Fig 18 Endurance Test Panel Conclusion A number of diverse switchgear testing systems have been successfully developed and deployed locally for switchgear manufacturers and testing laboratories The test equipment design requires close collaboration between switchgear manufacturer testing laboratory and test equipment supplier The equipment requirements and standards change over time The test equipment must be designed to be flexible so as to accommodate future enhancements References 1 2 3 4 5 6 CIGRE SC13 High Voltage Circuit Breaker Reliability Data for Use in System Reliability Studies CIGRE Publication Paris France 1991 Ruben D Garzon High Voltage Circuit Breakers Design and Applications 2nd Ed Marcel Dekker Inc New York 2002 TM1800 Circuit Breaker Analyzer System User Manual GE Energy T Cousins Development of a Precision Timing System for Circuit Breaker Testing Quantum November 1999 Viv Cohen Electrical Shock And Fire Hazard Protection Conquering The Limitations Elektron September 1993 SANS 10142 1 2003 Ed 1 1 The wiring of premises Part 1 Low voltage installations Contact details For further information contact Terry Cousins Director TLC Engineering Solutions on 011 463 3860 or terry tlc co za2. Simultaneousness of contacts to part ms Time for Contacts to Part ms a Time for Contacts to Move From Part to Open ims Overtravel mm Bounce Back imm ooo Off to On average Spoed to 50 m s On 10 Of average Speed to 50 m s Test Limits Parameters OFF 10 EARTH EARTH to OFF z To Sim ultaneousness of contacts to touch ms Time for Contacts to Touch ms Time to Full Contact Closure ims Total Travel imm Simultaneousness of contacts to part ms Tin a fae antante ta Onari dun Fig 5 Open Close Speed Test Analysis Results These results can be printed and are saved to a database for future reference Short Circuit Testing Short circuit testing is one of the most essential tasks that must to be performed on equipment to verify equipment suitability It is also an essential tool from the design point of view as much design knowledge is based on experimental findings and consequently testing becomes the tool that is used for the development of circuit breakers Short circuit testing presents a challenge because what must be replicated is the interaction of a mechanical device the circuit breaker and the electric system where the switching conditions can vary quite widely depending upon the system configuration and so can the conditions which must be demonstrated by tests Another challenge has always been the development of appropriate test methods
3. breaker ELCB is primarily used for the protection of human life It has been found from numerous studies that once they have been introduced they dramatically decrease the number of fatalities from electric shock 5 The use of ELCB in buildings is required by law in South Africa SANS 10142 1 2003 Code of practice for the wiring of premises 6 The performance of the ELCB is regulated by local and international standards e g e SANS 767 1 SABS 767 1 Earth leakage protection units Part 1 Fixed earth leakage protection circuit breakers e IEC 1008 1 Residual Current Operated Circuit Breakers UL 943 Ground Fault Circuit Interrupters Manufacturers of ELCB need to provide proof of compliance by submitting circuit breakers for testing to testing laboratories An ELCB Test Unit instrumentation was developed for this compliance testing It consists of Computer based test sequencer Digitiser Variable Current Source Control Switching Tests basically require the injection of a leakage current into one of the phases A simplified ELCB test circuit is shown in Fig 12 SUPPLY ne TEST UNIT VARIABLE VOLTAGE ADJUSTABLE LEAKAGE CURRENT Fig 12 Earth Leakage Test Unit Block Diagram The user interface for the test setup is designed so that any one of the required tests can be performed All of the results are stored in a database for future reference A typical test setup screen is shown in Fig 13 The test follow
4. connecting the breaker to a known load and switching on and off at a specific point of the 50Hz ac wave This is illustrated in Fig 7 Fig 7 Precision Point on Wave Switching with Precision Timer The Precision Timer requirements were as follows e 10 microseconds accuracy in a 20 second timeframe 24 timer channels Independent pulse duration for each channel Absolute or point on wave time synchronization Graphical entry of timer parameters The actual design achieves timing accuracies around 2uS The block diagram of the Precision Timer is shown in Fig 8 Fig 8 Precision Timer Block Diagram A graphical user interface was developed to facilitate entry and display of the test sequencing times This is shown in Fig 9 NETFA PRECISION TIMER Fig 9 Precision Timer Test Sequencing The waveforms from the short circuit test were acquired by the high speed digitizer and displayed on the computer screen in the control room For some tests this had to be completed in a minimum time to ensure subsequent tests were performed according to a specific schedule A typical test waveform is shown in Fig 10 Peat 402 92 mA Rres TH 21 ow TTL Test Ra DITES DSI oe 28 Fig 10 Short Circuit Test Sample Waveform A number of automated analysis features are available by selecting an icon on the screen These include e Relative Measurements e Markers STL Peak calculation STL parameters are specified by the Shor
5. current and adjusts the variable transformer until the test current is in the green band as displayed in Fig 16 The computer then regulates the current in a closed loop control until the test is complete The test can conclude either by successfully reaching the specified end period or one of the test devices can trip which will result in the failure of the test batch All results from the test are saved to a test database that can be used for record keeping and results analysis A sample database screen is shown in Fig 17 28a Tet how y Tasma Reads Gupta TUITID 27 CU ZT a LL 00 2 Octet tr Li St Om 2 De 7226 HALLE 1 12 00 C2 20 0 troct De den 2 21 ode De Cut 29 OPS 2m OS 016 OR Ot SE 12 59 91 ntact TITI TT a Hagana Ke 8 2S wgon emamaa ne A bor bon Meter HF 13 1429 Neher OF 14 15 22 MWe her DO Atia Pe a A fer 0S LE LE Oden 26 OT ow 00e Det 0 tres D becin 67 28 28 medeci 21 25 tbe bend ete ie fend 472 rt adada De Dec 10 OF 22 33 fee cre 2 0e Dec 10 115 M Se 61007 9 22 2 Me bec 15 29 23 54 PS fre Ceedi DEC 6100 49 22 2 CR Bde Det 19 OO Red Pht Cote die Re 61007 22 2p 4 CS te Certe EE Groa 22 2 pc 2e Dec 15 S43 Lee Cotes er orori 8 22 2 th mbt Dec 17 pods QE Pen Cetin MC oriri a 22 2h ix 1 pri ee 212 20 a8 Be Gredi TE 61000 h 22 29 z Dde 125 40 OFS te Cortication EC O10 49 22 29 DO Sete LE ee x E Mae Lies
6. MP COIL CURRENT pe dE CLOSE amp TRIP Lo COILS AZ an NUM LINEAR TEST DISPLACEMENT CONTROLLER TRANSDUCER TRAVEL TEST BREAKER Fig 3 Test Equipment for Open Close Speed Test The test system also requires a power supply to energise the close and trip coils as well as a supply for charging the mechanism The travel measurement is obtained by connecting a linear displacement transducer to the contact mechanism The output of this transducer is then calibrated to correspond with the distance moved by the contacts A typical graphic display from the test is shown in Fig 4 amp F puu Circuit Breaker Results Brodker S124 Red SA Yellow tel Glue ed 7007 01 09 0 2 0 3 Time in Seconds Fig 4 Open Close Speed Trace The upper trace is the travel The centre three traces are the continuity of the contacts This example shows severe contact bounce when the contacts close These results are then automatically analysed by the computer software and a report is produced similar to the report in Fig 5 ye 8149 ge LEFT HAND SWITCH Type Type Description LEFT HAND CENTER RIGHT HAND Test Engineer mnj Serial No 002004 Contract Dev Date 2004 Apr 15 13 03 24 Tesi R li Parameters OFF to ON ON to OFF os Resums ee Simultaneousness of contacts to touch ms Time for Contacts to Touch ms Time to Full Contact Closure ims esses Total Travel mm
7. TLC ENGINEERING SOLUTIONS PTY LD OLUTIONS SOFTWARE TECHNOLOGY Design and Manufacture of Testing Equipment for Switchgear By Terry Cousins and Luis Valentim TLC Engineering Solutions Abstract Switchgear is a key component in electrical power systems It is essential to verify performance after design manufacture or repair This paper will discuss a range of automated testing equipment that are used to test switchgear The test equipment has been designed and manufactured in South Africa in collaboration with switchgear manufacturers and testing authorities Automated analysis of the measurements as well as archiving of results for future recall and comparison will be presented Introduction The definition of switchgear includes electrical disconnects fuses and circuit breakers used to isolate electrical equipment Circuit breakers are mechanical devices connected to the electrical system where they must provide a suitable path for the flow of the electric current as well as provide protection and control of the electric circuit by either initiating or stopping the current flow Circuit breakers design and performance verification requires specific tests to be performed This paper will present a range of testing systems for circuit breakers from the instrumentation and data acquisition perspective Circuit Breaker Testing Circuit breakers are designed and manufactured to operate correctly under a range of conditions These include s
8. forms a protective function from the combined electrical and mechanical point of view the contact structure is probably the most essential and critical component A second and equally important component is the operating mechanism employed to produce the motion of the contacts A circuit breaker is designed to interrupt a short circuit current The fault energy is proportional to the square of the fault current times the duration of the fault The breaker should clear the fault in the minimum time to limit fault damage This requires that the breaker must operate at a speed greater than a specified minimum speed determined by the design The current must also be interrupted in such a way that the arc does not re strike The interrupting time or breaking time of a circuit breaker has a common definition according to ANSI and IEC It consists of the time from the instant the trip coil is energized to the instant of complete interruption of the current flow through the circuit breaker taking into account the maximum arcing time required for interruption Note that the contact parting time as defined by ANSI is the summation of the relay time plus the opening time These relationships are illustrated in Fig 1 below 2 Interrupting Time Fault Trip Coil Arc Initiation Energised Extinction Arc Contacts Separation Opening Time Contact Parting Time Fig 1 Interrupting Time Relationships The opening and closing velocities as well as st
9. roke or travel distance are the most important operating characteristics of a circuit breaker They are dictated primarily by the requirements imposed by the contacts Opening and closing velocities are important to the contacts in order to avoid contact erosion as well as contact welding Since contact stroke is synonymous with contact gap circuit breaker stroke is primarily related to the ability of the circuit breaker to withstand the required operating dielectric stresses The opening and closing motion curve of a circuit breaker is shown in Fig 2 3 Position Closed position Contact closure ff Arcing zone cabana speed calculation points Damping zone Open position _ Fig 2 Circuit Breaker Open and Closing Motion Open Close Speed Test This test is performed to confirm the key mechanical parameters of the switchgear This includes the open and close speeds travel distance and contact closing and parting times Equipment for performing this test consists of Computer equipment with application software for performing the test and analysing the results Displacement transducer for measuring the travel of the circuit breaker Continuity measurement for measuring the contact open and closing Control circuit and power supply for energising the trip and close coils Current clamps to measure trip and close coil currents The equipment is shown below in Fig 3 CONTACTS PLANT INTERFACE UNIT CURRENT CLA
10. s the format of the standards requirement so that all the required tests must be completed on the sample batch FEE supir te theme tet C r Fig 13 Earth Leakage Test Unit Operator Interface The equipment is housed in a 19 instrumentation panel as shown in Fig 14 Fig 14 Earth Leakage Test Unit Equipment Endurance Testing A useful test to perform on switchgear is a rated load test for an extended period This is used to determine if any equipment malfunctions and can also be used to evaluate thermal information A constant current test rig was developed for this test with the following specifications Used to test circuit breakers up to 400A Programmable constant voltage current Closed loop control to keep current at required value Detect if any devices trip Record results The testing system consists of a 3 2kW power supply and adjustable transformer which provides the test current The output is set by a computer system which ensures the output remains within set limits The computer also saves the measured value and saves the test results to a database While a temperature recording device did not form part of this test rig it could be included if required The constant current supply user interface and results are shown in Fig 15 O a Fig 15 Endurance Test Setup Screen Fig 16 Final Current Adjustment Once the test parameters have been entered the operator selects the required
11. t Circuit Testing Liaison Agreement STLA This is an Agreement Group of International Certification Bodies concerning the type testing of high voltage electrical power equipment STL RMS calculation I t Integration AC RMS calculation Removal of Mean Export to comma separated text CSV Format All the raw data and results can be stored in a database for future reference A typical three phase calibration test waveform is shown in Fig 11 MSCIL Mo HAT 2 REPORT Ho 3640865636 NAS SAMPLE Ho INESEA TEST TYPE CALIBRATION TEST DATE 1967 01 06 TEST TIME 14 57 23 DATA POINTS 730000 SAMPLE TIME 10us RECORD TIME 300 ms 657 00 div WHITE PHASE WHITE PHASE Vina 226 Ime 2501 A Ipk 3544 A pki 3540 A IPKkF me 142 O d pF 066 13 39 kA cv 21 43 mady 657 00 Vidiv RED PHASE RED PHASE Yms 202 W Imis 2666 Ipk 41134 pki 4113 A kF 154 D 63 pF 0 60 15 39 kAd 21 45 madw 657 00 Vidiv BLUE PHASE BLUE PHASE Vine 227 Y Imis 2566 Ipk S557 A Ipki 3661 A IpkF 142 O 63 pF 0 60 15 39 k 21 43 madw Fig 11 Example Three Phase Calibration Waveform In addition to the short circuit test method described above where fault currents are interrupted there are several other test methods which involve testing at a specific current to determine the current carrying capacity of the breaker Earth Leakage Circuit Breaker Testing The earth leakage circuit
12. that can overcome the potential lack of sufficient available power at the test facility One has to consider that the test laboratory should basically be able to supply the same short circuit capacity as that of the system for which the circuit breaker that is being tested is designed However this is not always possible especially at the upper end of the power ratings A typical test circuit is shown in Fig 6 below 2 Fig 6 Elementary Schematic of Short Circuit Test The test circuit consists of a power source G which can be either a specially designed short circuit generator or the system s electric network For the protection of the supply a high capacity back up circuit breaker BUB is used for interrupting the test current in the event that the circuit breaker being tested TB would fail to interrupt the current In series with the back up circuit breaker there is a high speed making switch MS which is normally a synchronized switch capable of independent pole operation and of precise control for closing the contacts at a specific point on the current wave Current limiting reactors L are connected in series with the make switch These are used to limit the magnitude of the test current to its required value Specially designed test transformers T are connected between the test circuit breaker and the power source These transformers are used primarily to allow for flexibility for testing at different voltage levels and in addition
13. to provide isolation between the test generator and the device that is being tested Across the test breaker terminals a bank of transient recovery voltage shaping capacitors C is connected To measure the voltages at least one set of voltage dividers V are used The short circuit current flowing through the test device is measured by means of a shunt Is Current transformers can be used especially for the current at the upstream side of the circuit breaker The test equipment instrumentation supplied for the short circuit testing consists of e High Speed Digitiser o Measures voltage and current waveforms up to 5 MS s with 12 bit resolution o Capture up to 4 million samples e Precision Timer o Used to synchronise all the test events to a precise timebase e Computer for Data Analysis and Presentation A precision timer was specially designed and engineered for this application 4 A programmable logic controller PLC is used in the test facility to provide the necessary control and safety interlocks It does not however have a sufficiently accurate timebase to provide for the synchronization of the make switch Under short circuit conditions the current flowing through the circuit breaker can exceed 100KA and equipment is highly sensitive to the time taken to clear the fault In order to test circuit breakers it is necessary to provide an exact fault current to ensure the device is not destroyed by the test The fault current is obtained by
14. witching currents up to the rated load as well as interrupting overload or fault currents several times the rated current In the event of a malfunction the circuit breaker as well as parts of the electric system may sustain severe damage It is therefore essential to have a high degree of confidence in the performance of any circuit breakers This confidence level can only be attained by years of operating experience or by extensive testing under conditions that simulate those that are encountered in the field applications Testing will usually be performed to ensure compliance with a local or international standard Special tests may also be performed by manufacturers to evaluate new designs The tests that are common to most circuit breakers include e Mechanical Operation o Performance of the mechanism to open and close contacts o Endurance of the mechanism e Electrical Operation o Ability to operate safely with rated loads o Ability to safely isolate overloads and short circuits Mechanical Testing The most basic function of any circuit breaker is to open and close the contacts on command According to a CIGRE report 1 more than 90 of circuit breaker failures are attributed to mechanical causes These findings confirm the fact that circuit breakers are primarily mechanical devices that are called upon to perform an electric function Most of the time circuit breakers remain closed and simply act as electrical conductors When the breaker per
Download Pdf Manuals
Related Search