Virtual instrumentation for high voltage power capacitors assessment through capacitance monitoring and acoustic partial discharge detection

This paper describes a virtual instrumentation system developed for the laboratory evaluation of high voltage power capacitor units in the end of life. The system was designed and developed to meet the demand of a large Brazilian electrical energy transmission company. As some power capacitor units in a bank of 500 kV failed, the company asked CEPEL Electrical Energy Research Center to evaluate certain units to see which would be in better conditions to continue in operation until their definitive replacement. The adopted methodology was the detection of partial discharges (PD) during a special applied voltage test with the monitoring of temperature and capacitance values. To accomplish this test, a virtual instrumentation system was developed that was cap capable of monitoring the waveforms of the applied voltage and the currents in the capacitor units with simultaneous detection of acoustic PD signals. The developed system has proven its effectiveness in diagnosis of high voltage power capacitor units. This paper presents and discusses the proposal of this unconventional evaluation system for high voltage power capacitors that was applied successfully in laboratory assessment tests.