PDC-ANALAYSER user's guide
Contents
1. time domain and the complex capacitance C C w jC and the derived tand m in the frequency domain For more information see the User s Guide of PDC Evaluation program 4 Performing a measurement To perform an accurate measurement it is important to connect the test object to be investigated as long as possible to PDC ANALYSER 1MOD before starting the measurement because both the high voltage supply and the current sense input are normally short circuited to ground Thus the capacitances of the test object are well discharged Now a 3 phase power transformer is taken as an example of a test object The transformer must be connected to the PDC ANALYSER 1MOD as a capacitor see figure 2 To obtain such an arrangement all the high voltage bushings could be connected together the high voltage windings behave as a first electrode of the capacitor under investigation The second electrode of the capacitor is formed by connecting all the low voltage bushings together The relaxation currents are sensed from the low voltage windings to ground During the measurement the tank of transformer must be grounded see figure 3 Copyright ALFF Engineering Switzerland 4 ALFF Engineering Ge E i a a rel K ei SAS Power transformer Multi layer capacitor Figure 2 How to connect a power transformer as capacitor for the dielectric investigation of the main insulation Voltage cable ilil Curren2. PDC ANALYSER 1MOD a i pin ce Ce vn Sen fo e DN Le Ka r aayy z e bak pal Ze gr Ke kb a EAE en fod e A Apr 17 pede e ei Ze A E s 7 A User s Guide ALFF Engineering Gomweg 7 CH 8915 Hausen am Albis Switzerland phone 41 44 77 66 776 fax el ae 77 6G 77 7 email info alff engineering ch web www alff engineering ch ALFF Engineering Caution The PDC ANALYSER 1MOD contains an externally accessible high voltage source producing up to 2 kV and up to 5mA internal current limit The instrument must be operated only by skilled persons The operators are responsible for protecting the test site against the hazards related to high voltages All the elements of a test setup which are connected to this high voltage source or which could be set under voltage by any insulation breakdown must be protected against being contacted by the operator or by any other person as long as the mains power is supplied to the instrument Also the PDC ANALYSER 1MOD must be stored and operated in a mechanically secured position and all the cables connected to it must be protected against making anyone fall over them or accidentally pull on them Content 1 Hardware 2 Measuring program 3 Evaluation program 4 Performing a measurement 5 Specifications Gi JA A A U La Appendix A Copyright ALFF Engineering Switzerland 2 ALFF Engineering Figure 1 The connections of the PDC ANALYSER 1MOD 1 Har
3. a number between 01 to 99 which identifies a single measurement in a measurement series with a given name prefix in this example testa This number increments automatically for each further measurement performed in this series p indicates the type of the file in this example polarisation current data file Copyright ALFF Engineering Switzerland 8
4. dware Please connect the keyboard to jack 4 before turning on the PDC ANALYSER 1MOD Use switch 3 to turn on the instrument The high voltage cable which has a SHV plug is connected to jack 1 and the current sensing cable with the BNC plug is connected to the jack 2 labelled current measurement Plug 5 is for connecting the optional PDC Phantom 1000XE voltage source see separate instruction sheet For an accurate measurement a warm up time period of 60 min is recommended 2 Measuring program To perform a measurement with the PDC ANALYSER 1MOD start PDC Measurement by double clicking on this icons on the desktop of the instrument On the first window after invoking the program the measuring parameters can be set The name of directory where the generated files will be saved The name prefix for generated files see Appendix A The temperature value important for the evaluation The test voltage The duration of an initial delay period before the measurement The duration of the polarisation The duration of the depolarisation The description of the test object only for information Copyright ALFF Engineering Switzerland 3 ALFF Engineering After the desired measuring parameters have been set the measurement can be started by clicking start measurements A new display appears and the instrument is internally initialised this takes about seven seconds Then the first delay d
5. ent one file with polarisation data one file with depolarisation data and one file with general measurement descriptions installed ready to use easy to use extensive possibilities to postprocess to display to print and to export the measured data computation of the complex capacitance in function of frequency computation of a lumped equivalent circuit of the measured insulation computation of recovery voltages and the derived polarisation spectrum computation of polarisation indexes and of insulation resistances according to all known standards and definitions quality assessment of oil paper insulation systems quantitative determination of moisture content in pressboard and of oil conductivity for power transformers 17 3 kg 90 260 V 47 63 Hz lt 160 VA 514 x 185 x 428 width x depth x height in mm 0 35 C 10 50 C 70 106 kPa 5 80 non condensing lt 2g 15m ALFF Engineering Appendix A The PDC ANALYSER 1MOD generates 3 files for each measurement These files are stored in the directory as entered during setup The polarisation current data are registered in a p dat file The depolarisation current data are registered in a d dat file Information about the measurement are registered in a c txt file The name of each generated file is composed of 3 different parts Example The name of a file could be testal4p dat testa is a name prefix which identifies a measurement series 14 is
6. r transformers a charging voltage amplitude of up to 500 V is recommended Used transformers are less sensitive to the non linear effects due to their high conductivity of oil So for used transformers the excitation voltage can be increased up to 1 000 V In general a polarisation duration of 5 000 to 7 000 seconds is sufficient to assess the insulation quality of a power transformer the same duration is also recommended for the depolarisation duration In general it is important to avoid non linear effects by keeping the amplitude of the applied excitation voltages as low as possible It is also recommended to keep the discharge periods between the successive dc voltage applications long enough to avoid any superposition of dielectric responses Copyright ALFF Engineering Switzerland 6 5 Specifications ALFF Engineering Electrical Insulation Diagnostic System PDC ANALYSER 1MOD Current measurement range resolution current display when measuring resolution recorded data accuracy impedance protection noise suppression filtering current display when measuring filtering recorded data Voltage source voltage range when switched on maximum current sourcing when switched on impedance when switched on impedance when switched to zero current limiting when switching cap loads Capacitance measurement 1 mA 1pA 0 1 pA 0 5 of the measured value 1 pA after 1 hour warming up 10 KQ up to 100 mA respectivel
7. t L Power transformer Figure 3 Connection of a power transformer to PDC ANALYSER 1MOD Copyright ALFF Engineering Switzerland 5 ALFF Engineering For an accurate measurement it is necessary to determine the initial condition of the test object before any application of excitation voltage The initial condition or charging state of a test object can be determined by monitoring the initial current which flows through it For visualisation of this current it is sufficient to start a current measurement with a polarisation duration of zero seconds It is important that the initial current is low and at least in a steady state In case of a high but constant amplitude of initial current this current can be considered as an offset for the evaluation it can be subtracted from the measurements Before starting the main measurement it is recommended to carry out control measurements with a short charging duration e g 5 seconds to control the whole setup Verify the amplitudes of measured currents and the value of the capacitance Such a short control measurement will not affect the main measurement because the relaxation currents induced by a short charging duration can be neglected after a few minutes of waiting time The main measurement can be performed after the control measurement by choosing adequate values for the charging voltage amplitude and for the duration of polarisation and depolarisation For new powe
8. uration is counted down and the current from the current sensing cable is displayed The measurement can be aborted anytime by pressing ALT F4 The delay duration can be prematurely cancelled by pressing jump to measurements Caution As soon as the delay duration has been counted down or brought to end by pressing jump to measurements the high voltage source is turned on Now the polarisation takes place and the polarisation duration is counted down During this period the high voltage is indicated with four red lamps around the high voltage SHV jack 1 The polarisation period can be automatically jumped over by setting the polarisation duration to zero on the setup screen The measurement program can be aborted anytime by pressing ALT F4 If the accumulated data should be stored click on save and terminate to terminate the program After the polarisation duration has been counted down the high voltage source is set to exactly zero volts and the depolarisation duration is started Still the measurement program can be aborted anytime by pressing ALT F4 but all the data will be lost If the accumulated data should be stored click on save and terminate 3 Evaluation program The measured polarisation and depolarisation currents can be evaluated with the PDC Evaluation program The basic version of this program permits the determination of the resistance polarisation index PI recovery voltage and derived polarisation spectrum in the
9. y 1kV for 50ms up to 10 uA eff at 50 60 Hz mains frequency mean value in 1 s intervals mean value in intervals increasing proportionally with the time from the voltage source switching moment 30 2000 V lt 5 mA lt 20 kQ lt 0 20 lt 100 mA for 20 ms the load capacitance is indirectly measured by computing the ratio charge to voltage when the voltage source is switched off for measuring of the depolarisation current However the current measurement is not impaired by a load capacitance depassing the range listed below accuracy maximum load capacitance Computer display processor memory hard disk standard interfaces options Software operating system measuring and control program standard evaluation software advanced evaluation software Miscellaneous weight power supply size temperature use temperature stock pressure humidity acceleration length of standard measurement cables Copyright ALFF Engineering Switzerland source voltage 2kV 1 kV 500 V 100 V 2 5 pF 2 10 pF 2 20 pF 2 100 pF 25 nF 50 nF 100 nF 500 nF 15 TFT 262 144 colours resolution 1024 x 786 pixels Intel Pentium III 1 GHz SDRAM 256 MB 40 GB DVD RW 3 Floppy 2 x PCMCIA parallel and serial ports Ethernet additional serial ports Audio in out external monitor out windows XP home SP2 installed ready to use outputs for each measurem
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