On-LineDigital Computer SystemforMeasurement ofPartial Discharges inInsulation Structures
Johnaustinand Ron E. James · 1976
An outline isgivenofthenature ofpartial discharges occurring ininsulation structures, inparticular inoilimpregnated configurations. Itissuggested thatconventional discharge measuring systems arenotalways abletoassess significant parameters because muchoftheavailable information isinevitably discarded during the high-voltage tests. A mobile computer-based data-acquisition system has beendeveloped forrecording andstoring, indigital form, thestatistical information present. Theequipment described iscapable ofrecording andanalyzing thesmalldisturbances produced bypartial discharges under practical conditions. Thecomputer programs enable thetimeof occurrence andthemagnitude andpolarity ofthepulses toberecorded; inaddition, digital transient-event recorders canbeprogrammed to accept slowpartial discharge shapes orultrasonic transducer outputs forstorage inthecomputer system. A widerange ofplayback programs aredescribed andpossible methods ofpresenting theresults arediscussed using examples obtained froma50-kVhigh-voltage test arrangement. Theproblems ofhardware development areoutlined, including those ofinterfacing andoperation inhostile environments. Theeconomics of suchasystem arementioned andmethods ofeffecting cost reductions aresuggested. Finally, thispapersuggests thatifon-line characterization ofpartial discharges becomes possible thentheresults ofdischarge measurements will havegreater significance thanatpresent, especially inthose border- line cases whereinterpretation ofresults isdifficult. INTRODUCT ION A S PART ofalong-term research program concerned )Axwith thelocation anddetection ofpartial discharges in transformer insulation, adigital measurement system hasbeen developed foron-line datarecording andanalysis. Theoriginal system (1), (2)wasdesigned fordetecting signals produced at theterminals ofawinding whenanindividual partial discharge occurred within thestructure athigh voltage, either ontest or inservice. Subsequently theworkhasbeenextended tostudy moreclosely someofthecharacteristics ofdischarges detected across typical two-electrode samples. Itishoped that thelatter workwill1)assist inthedevelopment ofimproved measure- mentsystems, 2)helptogive abetter understanding ofthe physical processes involved fordifferent insulation conditions andarrangements, and3)enable comparisons tobemade between existing measuring techniques, including theselection ofthemostsignificant parameters.