Experimental study on the influence of series compensation platform switching on capacitor voltage transformer in ultra high voltage power system

While series compensation platform switches in ultra high voltage (UHV) system, intermittent arcs appear between the switch contacts of a series disconnector, which may lead to insulation breakdown of the capacitor voltage transformer (CVT). It is necessary to investigate the influence of series compensation platform switching on CVT. A simulation experiment was set up with actual series compensation platform, a disconnector and a CVT, which were applicable for UHV system, to determine the fast transient voltage and current on CVT while the disconnector is switching on and off. And the mechanism of CVT insulation breakdown was investigated by the fast transient current experiments on CVT capacitor units. It was found that a series resonant circuit including CVT, inductance of transmission line and capacitance of platform to earth would be established during disconnectors switching operation, and CVT would suffer from repetitious transient overvoltage and overcurrent due to the intermittent arc breakdown between the contacts of disconnector. Besides, experimental results show that the weld-joint area between CVT capacitor elements is the weakest point of insulation and the peak value of multi-impulses current that CVT can withstand is about 4.5 kA. © 2015 Chin. Soc. for Elec. Eng..