Abstract:

According to IEC 62271-200 or GB/T 3906 standard,two-phase fault will develop into three-phase fault in 12 kV switchgear when conducting two-phase type test of internal arc fault,which mostly occurs in the initial stage and middle stage of flow passage.This paper studies and analyzes this situation through typical test cases,and further analyzes the development of two-phase fault into three-phase fault through simulation.The analysis shows that the current will increase when two-phase fault develops into three-phase fault,and the voltage phase of the phase corresponding to the starting point of the third-phase current ignited is uncertain,which directly affects the maximum current peak of the phase.The results show that the reason of insulation failure can be analyzed by the development of two-phase fault into three-phase fault,which provides a reference for the improvement of the performance of the switchgear.

Key words: internal arc, two-phase fault, three-phase fault, phase, uncertainty, current peak