Analysis on Short Circuit Current Limiting Effect of Installing Small Reactance in 500kV Autotransformer’s Neutral-point

Abstract

For the condition that single-phase short circuit current exceeds three-phase short circuit current occurs on some of Shandong 500kV substations’ 220kV bus, this paper studies the principle of limiting 500kV autotransformer’s short circuit current by installing small reactance. Considering that installing small reactance at 500kV autotransformer’s neutral point influences the zero sequence circuit, this paper suggests to configure independent relay protection on small reactance which aims at supervision the short circuit current and improving reliability. Protection setting for neutral-grounding small reactance is proposed. Simulation results and protection setting software show the effect of limiting short circuit current by installing small neutral-point reactance.