The Analysis And Study Of A New Protection About The Solid Ground System

In the modern power grid, with ultra-high voltage, high-capacity, long-distance transmission lines growing on the power system relay protection devices of a higher, more stringent requirements.So far 110kV and above power grids use neutral grounding system. According to statistics, ground faults comprise more than 90% of the total faults. Excluding feeder protection, the existing ground protection mainly involves zero sequence current protection and earth-fault distance protection. Zero sequence current protection has simple construction and high sensitivity, but it's highly affected by the operation mode. Although the protected region isn't affected by operation mode, distance protection has complicated construction and expensive devices. It is very worthwhile to research a protection system which not only has simple structure but also not to be effected by mode of operation.Firstly, this paper summarizes the present situation of solid ground system, and analyzes the affection of transition resistance to the distance protection. According to analysis of zero sequence current protection and distance protection, the characteristics of the two methods are obtained. This paper analyzed the new criterion which has been proposed in the article [21].The new criterion is mainly about the negative sequence and zero sequence components. We draw a conclusion through theoretical analysis and simulation. This paper analyzed the operation characteristics and the standing resistance ability of the new criterion when asymmetric fault happens both in single power supply system and dual power supply system.Theoretical analysis and simulation proves that this new criterion has prepotency. At the same time in the two-phase ground short of the circumstances that may arise beyond the setting district. The paper put forward some methods to improve the existent problems.