Study on installing small reactance in neutral point of 500kV transformer on Guangdong power grid

With the 500kV substations put into operation one after the other, the capacity and scale of 500kV autotransformer are more and more large. The single-phase short-circuit current at 220 kV buses of 500kV substations is higher than three-phase, the safe operation can´t be satisfied. It can be controlled by adding small reactance at 500kV autotransformers from the operation experience of all over the world. This paper analyzes the reason and necessity for adding small reactance at 500kV autotransformers from the level of short current on Guangdong, and studies the types of substations which are fit to installing them. It also studies the effect of the small reactance capacity on limiting short-circuit current of single phase, and proposes the installation program for Guangdong power grid.