Abstract：This paper carefully analyzes the cause of protected trip through a obstacle of a 110kV incoming system, according to accident processing and action on the protection, and found wrong secondary wiring of B bus GPT are the cause of the accident. When three - phase and four - wire system has asymmetrical load, the concept and formula about the deviation of voltage at neutral point are given, the revelation from the accident are put forward.
2013, Vol. 14 
