A Novel Damped AC Generator Used for Off-Line Partial Discharge Testing of Power Cables

Abstract

Damped AC (DAC) testing is a widely utilized method for detecting partial discharge (PD) signals in power cables. However, the conventional approach is detrimental to the cable's insulation due to the accumulation of space charge during the DC charging process. To address this issue, this paper proposes a novel DAC generator topology. Compared with the conventional DAC generator, a storage capacitor and a switch are added. In the proposed DAC generator, by conducting switches at different moments, the voltage across the cable oscillates from near zero instead of starting from a high DC voltage, thus preventing the injection of space charge into the cable's insulation layer. To verify the effectiveness of the proposed DAC generator, an experimental platform was established. The results demonstrate that the DAC generator operates normally and successfully initiates PD signals at cable defect sites. The comparative experiments reveal that the total PD quantity under the novel DAC voltage is lower than that under the conventional DAC voltage for two types of defects, which suggests no space charge is injected in the novel DAC approach.