Study on the DAC System for 10kV Cable Insulation Testing Based on DC-AC Technology

Traditional damped AC (DAC) technology has been widely utilized in filed partial discharge tests of power cables due to portability and effectiveness. However, space charge accumulated in the cable insulation during the DC charging stage would harm the cable health. Aiming at this problem, an AC charging DAC technology is proposed based on DC-AC convertor technology in this paper. The sinusoidal voltage with adjustable frequency and voltage is generated to quickly charge the tested cables by controlling the system to work in resonance. The operating voltage of the damped wave conversion switches is significantly reduced. Avoiding the serial use of a large number of costly high voltage semiconductor switches, this system improves the overall reliability and economy. The basic principles, design ideas and implementation process of the system were elaborated and demonstrated in detail. Partial discharge test was conducted of a 400m 8.7/10kV power cable. The results show that the proposed DC-AC charging DAC system could produce 24kV DAC voltage which can meet the requirements of the partial discharge test for 10kV power cables.