中性点电压偏移对外熔断器动作时机和电容器组保护顺序的影响

针对10 kV并联电容器组故障后外熔断器动作次数远低于继电保护装置的运行现状,利用Matlab软件分析了太仓地区10 kV单星形并联电容器组不同程度故障时的过流系数及外熔断器动作表现,仿真结果表明,考虑故障后电容器组中性点电压偏移因素在单台电容器内部击穿1个串联段后,其过流值不足以达到外熔断器动作值,加之工程实践中的继电保护装置灵敏系数通常远高于规程要求,继电保护将成为事实上的“第一级保护”,外熔断器因其动作条件及误差特性,反而成为一种不可靠的“后备保护”。

Effect of Neutral Point Voltage Offset on Operating Opportunity of External Fuse and Protection Sequence of Capacitor Banks

In view of the fact that the action times of external fuses of 10 kV shunt capacitor bank is much lower than that of relay protection devices,the over?current coefficient and the action performance of external fuse under different degrees of failures are analyzed by using Matlab software.It is shown by the simulation result that the over?currentof external fuse is not sufficient to meet the operating value after one internal seg?ment of a capacitor breakdown,with the neutral point voltage offset factor taking into account.In addition,the sensitivity coefficient of the relay protection device in engineering practice is usually much higher than the regulation requirements.The relay protection will become in fact the the first stage protection.The external fusebecomes an unreliable backup protection due to itsoperating conditions and error chara cteristics.