基于抑制短路电流的500 kV变压器中性点经小电抗接地的电抗选值研究  

Study on reactance selection of 500 kV transformer with neutral point grounded by small reactance based on restraining short-circuit current

作　　者：徐瑶台 黄云辉[1] 潘小军 XU Yaotai;HUANG Yunhui;PAN Xiaojun(School of Automation,Wuhan University of Technology,Wuhan 430070,China;Wuhan Power Supply Company,Wuhan 430040,China)

机构地区：[1]武汉理工大学自动化学院,湖北武汉430070 [2]国网武汉供电公司,湖北武汉430040

出　　处：《电气应用》2019年第5期10-15,共6页Electrotechnical Application

摘　　要：近些年来,我国电网规模日益扩大,网架结构不断加强。由于成本相对较低,500kV变电站大都采用自耦变压器,且中性点直接接地运行。然而,在中性点直接接地的运行方式下,部分500kV变电站220kV侧单相短路电流过高,甚至高于三相短路电流,对电网的安全稳定造成威胁。文章主要研究500kV自耦变压器中性点由直接接地改为串接小电抗器接地后220kV侧单相短路电流水平。构建了双电源模型对电力系统进行等效,阐述了500kV自耦变压器中性点串接小电抗限制220kV侧单相短路电流的原理。并研究了不同站点变压器中性点加装小电抗对不同短路位置短路电流的影响能力。研究结果表明,当电抗值选在10~25Ω之间时,限流效果最为明显。In recent years, the scale of China's power grid is expanding day by day, and the grid structure is constantly strengthened. Due to the relatively low cost, the 500 kV substation mostly adopts autotransformer, and the neutral point is directly grounded. However, when the neutral point is directly grounded, at parts of the 500kV substations, 220 kV single-phase short-circuit current is too high, even higher than the three-phase shortcircuit current, which is a threat to the security and stability of power grid. This paper mainly study the current level of single-phase short-circuit on the 220 kV side of the 500 kV autotransformer, which is changed from the direct grounding to the series reactor. The dual power model is built as an equivalent power system, explaining the principle of 500 kV autotransformer with neutral point grounded through small reactance that can limit 220 kV single-phase short-circuit current. And the influence of the small reactance at the transformer of different stations on the short circuit current at different short circuit positions. The results show that when the reactance value is between 10~25 Q, the current limiting effect is the mostly obvious.

关 键 词：单相短路电流 三相短路电流 自耦变压器 小电抗 

分 类 号：TM862[电气工程—高电压与绝缘技术]