500 kV自耦变压器中性点加装小电抗限制不对称短路电流原理

结合电网各种限制短路电流的方法,分析其中的优缺点,针对广东电网部分500 kV站点的220 kV侧母线单相接地故障电流超标问题,研究主变中性点加装小电抗限制故障电流的原理,分析表明加装小电抗是限制不对称接地故障电流的有效措施,且小电抗投资小,经济性高,运行较为可靠.通过计算500 kV加林站在规划期2015年的短路电流,对比加装0 ～40 Ω小电抗时限制电流的效果,提出合适的小电抗阻值选取范围为10 ～ 15 Ω.加装小电抗对系统正常运行无任何影响,但是会影响零序保护装置灵敏度,需要重新校验整定值,以防保护拒动.

Principle of Limiting Asymmetric Short-Circuit Current by Installing Small Reactance at 500 kV Autotransformer Neutral Point

The advantages and disadvantages of various short-circuit current limiting methods were analyzed. According to the issue that the single-phase grounding fault current of 220 kV bus exceeded the limit in part of the 500 kV substations of the Guangdong Power grid, the principle of limiting fault current by installing small reactance at 500 kV autotransformer neutral point was researched. The analysis results show that the installation of small reactance is the effective measure for limiting asymmetric ground fault current, and the small reactance has the advantages of small investment, high economy and reliable operation. Through the calculation of short-circuit current of 500 kV Jalin station in 2015, the effect of installing 0 40 reactance on limiting current was compared to suggest that the appropriate reactance resistance should be selected between 10 15 ~. The installation of a small reactor has no impact on the normal operation of the system, but affects the sensitivity of zero- sequence protection device, therefore, the setting values should be re-checked to prevent protection from refusing to operate.