中性点非有效接地系统电压互感器故障分析与治理措施研究

The fusing of potential transformer(PT)fuse and the burning of PT(generally referred to as the PT fault)occur multi-times in non-direct grounding neutral system, which is a serious threat to the safe operation of power system. In this paper, the causes of 26 PT faults in the grid system and the present protective measures are analyzed. It is found that the fundamental cause of PT fault is PT over-excitation and over-heating damage,88% of which is caused by intermittent arc grounding overvoltage(in 10 kV grounding neutral system via arc suppression coil), and only 12% of which is caused by ferro-resonance overvoltage(in 35 kV non-grounding neutral system). The key to inhibiting PT over-excitation is to limit the arc grounding overvoltage and ferro-resonance overvoltage. The present measures are merely focused on eliminating the ferro-resonance overvoltage, while the limitation of the arc grounding overvoltage is not effective. Therefore, a new type of thermistor device with both current limiting and resonance elimination functions is highly recommended. The technique employs both current limiting and resonance elimination functions, which shows excellent adaptive feature and good effect of PT fault elimination and enjoys a promising prospect in application.