Analysis of the Causes of Electrical Accidents Caused by Operating Over-voltage of High Voltage Switchgear
Jungang Zhou, Xueming Fan, Ya Liu, Lei Peng · 2016
In this paper, the lightning arrester explosion accident and transformer short-circuit accident in power supply system were analyzed in detail.It was found that the operating over-voltage caused by the frequent operation of the 35kV high voltage switchgear was the main cause of the accident.It was found that the frequent operation of high voltage switchgear had caused cumulative damage to the insulation property of high voltage power equipment.When the operating over-voltage exceeded the threshold value of insulation performance of power equipment, the insulation breakdown caused accidents.According to the characteristics of the power supply system, the reasonable suggestions were put forward, which was helpful to improve the safety performance of the power supply system. IntroductionHigh voltage switchgear is widely used in power supply system.In general, high voltage switchgear doesn't need to operate frequently.In the regular routine maintenance, it needs to close and disconnect operation.In some special applications, it is necessary to carry out frequent close and disconnect operation for high voltage switchgear.High voltage switchgear is generally installed lightning arrester, to limit the over-voltage caused by close and disconnect operation of high voltage switchgear.In order to ensure the safe operation of power supply system.High voltage switchgear in the power supply system may be subjected to lightning over-voltage and operating over-voltage of two over-voltage damages.According to the measured lightning over-voltage waveform is a kind of non-periodic pulse, according to the domestic and international standards [1] :standard lightning impulse voltage test wave front time is 1.2us ± 30%, half peak time is 50us ±20%; standard operating over-voltage of the wave front time is 250us ± 30%, half peak time is 2500us ±60%.The duration of the operating over-voltage is much longer than that of the lightning impulse over-voltage, the shape is more complex, and its shape and duration vary with the specific parameters and length of the line.At present, the international trend is to represent the operating over-voltage with a long pulse of a few hundred milliseconds and a few thousands.Lightning arrester is installed in the high voltage switchgear, which is used to protect electrical equipment from the high transient over-voltage hazard and limit the time.Lighting arrester under normal operating voltage shows a high resistance state, only microampere current through.A low resistance is presented under the action of over-voltage and high current, which limits the residual pressure at both ends of the arrester.At present, the domestic and foreign related research on this direction is mainly concentrated in the lightning and the operating over-voltage identification [2,3] , over-voltage online monitoring [4,5] , the impact of operating over-voltage on electrical equipment [6-12] and other direction.For the frequent operation of high voltage switchgear in power supply system, there were less researches on the cumulative damage of the insulation performance of power supply equipment, and there was no relevant report about the accident.The power supply system in the high voltage switchgear frequent operation for the accident caused by the detailed analysis of the causes, and put forward reasonable suggestions to improve in this paper.