Design And Research Of Zero Sequence Protection Of 66 KV System In Gezhenpu Substation

Due to the widespread use of city substation power cable,system capacitive current is greater than the relevant provisions of the relevant procedures,so the system neutral point grounding way all arc suppression coil grounding mode instead.This paper expounds the positive influence of this grounding mode on the power system.At the same time,the paper also expatiates the limitation of the current detection technology,the grounding system of the arc suppression coil can not select the line accurately,and the artificial selection is time-consuming and time-consuming.However,during the failure period,the cable is prone to overvoltage and easy to develop into a multi-phase fault,so the system grounding mode still needs to be further developed,and the protection of system docking fault needs to be changed.Due to the low resistance grounding system is a system that does not allow continue operating of connected sites,so when the cable line single-phase earth fault occurs,the system will appear zero sequence current,zero sequence current protection will be selective removal of the fault line,back to the normal operation of the power system.From the perspective of development,it is a trend of the world that the neutral point of distribution network adopts low resistance grounding.This paper aims at the above problems in the actual operation of 220 kV substation,combining with the development trend of power system,the feasibility study on the commissioning of 66 kV zero sequence function in gezhenpu 220 kV substation is carried out,determine low resistance and arc suppression coil grounding method of fundamental solutions.This paper focuses on the study of the resistance and thermal stability of grounding resistance,analyzes the influence of low resistance on the stability of the system and the countermeasures,and completes the relevant simulation work at the same time.In this paper,the setting calculation of zero sequence protection of main transformer and zero sequence protection of line in the system is also carried out,and the problems under various special operation conditions are discussed.On the basis of the above theoretical research,in this paper,the specific design of zero sequence protection in gezhenpu 220 kV substation is completed,low resistance automatic switching,protection and measurement and control functions,main transformer and circuit zero sequence and zero sequence voltage and zero sequence current access,etc.At the end of the article,the case analysis of the single-phase grounding fault of the line with zero sequence function is analyzed in detail and zero sequence protection design for system development in full cable mode.Practice shows zero sequence function improved after the commissioning of the power supply reliability,save the power grid construction investment,but also solves the problems of overvoltage,difficult phase selection,difficult line selection,poor power supply reliability and the neutral point ungrounded system in single-phase grounding operation.