Reason Analysis for the increase of single-phase short circuit current and its suppressing measure

Aiming at the issue that the single-phase short circuit current at the 220 kV bus of Chengdu 500kV substation exceeds the three-phase short current or even exceeds the breaking capacity of breaker, the reason is analyzed and the measure that main transformer neutral grounding by small reactance is put forward to reduce the single-phase short circuit. According to the planning power network of Sichuan, this paper analyzes the limiting effects of 500 kV autotransformer neutral grounding by small reactance on 220 kV single-phase short circuit current by simulation and calculation. This paper also analyzes the influence of neutral grounding by small reactance on insulation level of neutral point, and put forward a directive idea about small reactor's selection.