500kV主变压器中性点加装小电抗器限制短路电流的研究

以东莞电网3个500kV变电站为例，分析500kV变电站220kV侧母线单相短路电流普遍超标的主要原因，提出限制单相短路电流的措施。针对自耦变压器中性点经小电抗器接地方式，阐释小电抗器的电抗值与单相短路电流的关系以及小电抗器对继电保护的影响，从节省投资、简化电路结构的角度推荐采用变压器中性点与小电抗器之间不安装隔离开关的电气主接线方案。东莞电网500kV变电站500kV自耦变压器采用中性点经小电抗器接地方式后，限制220kV侧母线单相短路电流效果明显，增强了变电站短路电流水平对电网建设的适应性。

Research on Short Circuit Current Limit by Installation of Small Reactor on Neutral Point of 500 kV Main Transformer

By taking three 500 kV substations of Dongguan power grid as examples,this paper analyzes causes for overstandard of single-phase short circuit current of bus at 220 kV side in 500 kV substations and presents measures for limiting single-phase short circuit current.In accordance that the neutral point of autotransformer is connected to the ground by small reactor,the paper expounds the relationship between reactance value of small reactor and single-phase short circuit current as well as impact of small reactor on relaying protection.The scheme that no disconnecting switch should be installed between neutral point and small reactor in consideration of investment conservation and circuit simplification is recommended.Since the neutral point of 500 kV autotransformer was connected to the ground by small reactor in 500 kV substation in Dongguan power grid,considerable effect on limiting single-phase short circuit current has been achieved and adaptability of short circuit current level in substation to grid construction is strengthened.