Fault Characteristic Analysis And Protection Method Research Of Small Resistance Grounding System

Small resistance grounding system has been widely used in power grid because of its obvious fault characteristics.With the increasing complexity of power grid structure,the frequency of faults in small resistance grounding system is also increasing,among which single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults occur most frequently.The existing protection devices of small resistance grounding system lack protection methods for the above faults,resulting in the system may operate with faults for a long time,resulting in major safety accidents.Therefore,the study of single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults protection scheme for small resistance grounding system has very important theoretical value and practical significance to maintain the safe and stable operation of distribution network,enhance the reliability and continuity of power supply,and improve the power quality of users.This paper first analyzes the action of zero sequence current protection and distance protection in the case of single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults of small resistance grounding system,and explores the reasons for the rejection of distance protection and zero sequence current protection.The fault characteristics of single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults are studied.The projection characteristics of the zero sequence current of each outgoing line on the zero sequence current of the neutral point after the fault of the small resistance grounding system are analyzed by using the electrical quantity projection method,and the projection eigenvalue of the zero sequence current is further defined.Then,based on the variation characteristics of electrical volume after single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults,and the projection characteristic value of zero sequence current,additional protection criteria for single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults of small resistance grounding system are constructed.At last,through the typical 10 kV small resistance grounding system simulation model to test and analyse the proposed additional protection criterion,the simulation results show that the presented single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults additional protection criterion can accurately identify and removal of the small resistance grounding system of single-phase high impedance grounding fault,single-phase disconnection fault and multiple faults,and do not need to add additional relay protection device,conducive to the promotion of application.