Research On On-line Partial Discharge Monitoring System For High Voltage Switchgear

Along with the national construction of smart grid, electrical equipment developetoward the direction of high-reliability and high intelligent. High Voltage Switchgear is oneof the most important electrical equipment of the smart grid, mainly used for control orprotection in power generation, transmission, distribution, energy conversion andconsumption. Rate of insulation accident of high-voltage switchgear is relatively high, thisaffect the safe operation of the power system seriously. The insulating state of the switchkey parts of the electrical equipment is an important indicator to measure the Gridintelligent and reliable operation, real-time monitoring of it is significative. To this end, wecarried out high voltage switchgear partial discharge monitoring system, contents are asfollows:First, the theory of partial discharge detection method, the overall design of the highvoltage switchgear partial discharge monitoring program, including leakage current onlinemonitoring, ultrasonic and UHF partial discharge online monitoring unit is introduced.Sencondly, hardware circuit of online monitoring unit of the leakage current andultrasonic discharge is designed with DSP2812as the core, also the hardware circuit ofcommunication unit is designed. Hardware anti-jamming measures is used in the systemdesign to ensure the reliability of the circuit.Next, lower machine software part of the leakage current online monitoring isdesigned, including the AD acquisition, FIR filtering, data computation, display andcommunication; joint debugging with the host computer make the online monitoring of theleakage current on the host computer come true.Then, short-time Fourier and discrimination algorithm based on the minimum distancewere achieved in Matlab environment, they were used for ultrasonic discharge recognition.this do the theory research for ultrasonic discharge pattern recognition in DSP.Finally, the quadratic Wigner-Ville distribution was used to describe the jointtime-frequency distribution characteristics of partial discharge signal; Pseudo Wigner-Villedistribution, smoothed pseudo Wigner-Ville distribution and the Cohen class spectrumrearrangement were used to do simulation study of partial discharge signal, inhibiting theinterference cross terms of Wigner-Ville distribution, made a good time-frequencyaggregation.Experiment show that the leakage current online monitoring system obtained good results, have the characteristics of fast response, real-time online, data communications andPC monitoring. The design of ultrasonic discharge detection circuit detects the dischargesignal well, laying a good foundation for the realization of online monitoring system forultrasonic discharge. Further research and discussion is needed for specific practicalengineering applications.