一起35kV系统非金属性三相短路保护动作行为分析

Analysis of Protection Operation Behavior for One Nonmetallic Three-phase Short Circuit Fault in 35 kV Power System

根据某110 kV变电所35 kVⅡ段母线发生了一起B相接地造成110 kV主变35 kV后备保护越级跳闸的现象,以变电所设备参数和保护装置实际故障录波为参考,通过假设性推理和短路电流的故障反演计算分析,得到事故原因是由于B相单相接地而引起其他两相电压升高造成这两相整体绝缘下降引发了非金属性三相短路引起的,但35kV出线保护由于B相无电流互感器(TA),无法判断故障发生,从而证实了110 kV主变35 kV后备保护的动作行为是正确的,并提出相应的改进意见。

The tripping operation of the 35 kV back-up protection of the 110 kV main transformer is analyzed in the paper,which caused by the B-phase grounding in II section of 35 kV bus in 110 kV substation.Based on the substation equipment parameters and the actual fault wave in the protection,the hypothetical reasoning and inversion analysis of short-circuit fault current are carried on.The cause of the accident is that the voltages of other two phases rise,resulting in the overall insulation deterioration,which caused the nonmetallic three-phase short circuit fault at last.However,as there is no current transformers in B-phase of 35 kV system,so the B-phase grounding fault cannot be detected.Thus,the 35 kV back-up protection operation behavior in 110 kV main transformer is confirmed to be correct.Finally,suggestions for improvement are also proposed.