SF6가스중 HVDC에서 부분방전 특성에 관한 연구

Abstract

This thesis dealt with the characteristics of partial discharge (PD) on High Voltage Direct Current(HVDC) in SF6 Gas. Electrode systems such as a protrusion on conductor(POC), a protrusion on enclosure(POE), a crack on epoxy plate and a free particle(FP) were fabricated to simulate insulation defects. Analysis system was designed with T-F(Time-Frequency)map algorithm programed by LabVIEW. This can analyze the measured signal into frequency and time domain.

A HVDC power supply is composed of a transformer(220V/50kV) and a diode(100kV), and a capacitor(50kV, 0.5μF). The gap between the electrodes is 3mm, and the gas pressure of SF6 was set at 3bar and 5bar. PD pulses were detected with a 50Ω resistor and their characteristics were analyzed by a digital storage oscilloscope(DSO) with the resolution of 2.5GS/s and a DAQ system with the resolution of 30MS/s.

PD pulses were distributed below 0.5MHz and 20∼40ns for POC, below 1.7MHz and 10∼125ns for POE, below 0.1MHz and 135∼250ns for crack, and below 1.6MHz and 260ns for FP electrode system, respectively.