Study On Partial Discharge Of Oscillating Wave Test System

XLPE Power cable with superior electrical properties has been used more and more in the modern power system, electrical accidents caused by power cable insulation failure are also increasing. Study shows Partial discharge(PD) is the main cause of insulation faults in cable. Therefore, detection of cable partial discharge can reflect the state of the cable insulation, find out incipient faults in time, and avoid the power cable insulation breakdown and short-circuit accidents caused by cable partial discharge, which can improve the operation reliability of power cable.In this paper, theories of power frequency withstand voltage test, 0.1Hz VLF voltage test, series resonance voltage test and oscillating wave voltage test are analyzed. Study shows :1)power frequency withstand voltage test need large capacity for testing, and the whole system has large volume and heavy weight; 2)0.1Hz VLF voltage test exists problem of frequency equivalent;3) when it work in 50 Hz, series resonance voltage test system is not feasible for the field test because of large volume. OWTS with small capacity is feasible for the field test,partial discharge(PD)detecting unit based on OWTS can achieve the PD in insulation. By using the traveling wave principle OWTS can locate PD signal location. OWTS has been widely used for the cable insulation test and mainly dependent on importation from foreign countries. As a result, OWTS and PD detecting unit are studied in this paper.According to the oscillating wave theory, the hardware used in the system is designed, including the constant current high voltage DC power source, resonant inductor, high voltage switch, capacitive resistor voltage divider and PD detecting unit. According to the current impulse method for PD detection, component parameters in RCL detecting unit is analyzed and determined. Amplifier and filter circuits that enhance the ability to distinguish and the pulses in time domain and improve the accuracy of PD detection are designed.According to the tests and simulations, the OWTS can charge the 1μF capacitor in 3s in constant current constant voltage charging mode. Through the control of the high voltage switch, the OWTS can produce OW up to 40 kV. The RLC PD detecting unit can successfully detect PD signals produced by PD simulation unit and has high resolution, which can be used in field testing.