Research of Installing Small Reactors on Neutral Points of 500 KV Autotransformers and the Analysis of Overvoltage

Because of the extensive application of autotransformer in 500 kV power grid, the value of single-phase short-circuit current is generally greater than that of three-phase short-circuit current, or even greater than the maximum rated through current of the breaker. In order to reduce single-phase short-circuit current and avoid implement of bus split, this paper proposes to install small reactors on neutral points of 500 kV autotransformers. By analyzing and calculating the effect on short-circuit current limitation, the most suitable impedance value of small reactor is proposed. In addition，the overvoltage of the neutral point and insulation coordination are particularly discussed.