Research On Fault Protection Based On The Ratio Of Zero-Sequence Current Projection Components For Low-Resistance Grounding System

In recent years,with the increase in safety standards,low-resistance grounding systems have gradually replaced them in urban distribution networks because of the advantages of low-resistance grounding systems that can quickly isolate fault areas and low overvoltage levels.A small current grounding system in which the neutral point is grounded through the arc suppression coil.The traditional low resistance grounding system generally adopts definite time limit zero sequence overcurrent protection,which has high reliability.However,when a high-impedance ground fault occurs in existing protection devices,the zerosequence current of the fault line is often less than the starting value of the protection device,and the protection easily refuses to operate,leading to further expansion of the fault area and even the occurrence of personal injury.Therefore,line selection for high-resistance grounding faults in low-resistance grounding systems has become a key technical problem to be solved urgently.First,this paper analyzes the characteristics of single-phase grounding faults in common 10 k V low-resistance grounding systems.Respectively for the feeder and bus single-phase grounding fault network diagram,simplified into the corresponding equivalent zero sequence network diagram;for the feeder and neutral ground resistance branch in the two cases,the zero sequence current amplitude,phase and other electrical quantities The characteristics are analyzed.Second,analyze the characteristics of possible multi-line in-phase grounding faults,establish a zero-sequence equivalent network,analyze its electrical faults,and compare with single-feeder single-phase grounding faults.Third,based on the circuit analysis method,by extracting the fault characteristics of the neutral ground resistance branch zero sequence current,the fault line zero sequence current,and the sound line zero sequence current,and comparing their respective amplitude and phase information,it is proposed a fault protection based on the ratio of zero-sequence current projection components for low-resistance grounding system based on 5G technology projection differential and phase discrimination is proposed.Finally,the proposed protection scheme was simulated and verified by Matlab/Simulink,and it was verified that the scheme can reliably operate when high-resistance grounding,which effectively improves the sensitivity of the highresistance ground fault protection of the neutral point grounded distribution network through a small resistance.