酒泉-湖南±800 kV直流线路送端交流系统直流偏磁防护

Research on DC Bias Protection of AC System of Jiuquan-Hunan±800 kV DC Transmission Lines Sending End

酒泉-湖南±800 kV直流送端侧在模拟单极-大地运行时,周边系统变压器出现了直流偏磁现象。为解决酒泉-湖南直流引起的送端系统直流偏磁防护问题,提出了采用阻容结合抑直、分步治理的思想实现送端电网防护。在此基础上,为保证抑直装置接入对系统运行影响最小,从直流防护效果、绝缘电压等级和保护影响3个方面进行分析并选取阻容参数;最后,建立交流系统等效直流模型。经计算分析,变压器的偏磁电流被控制在阈值范围内,达到了预期的防护效果。

When the Jiuquan-Hunan±800 kV DC project is operating in the simulation of muipolar-earth grounnd,the phenomenon of DC magnetic bias appeares in the transformer of the surrounding system.In order to solve the problem of DC bias protection of the system caused by Jiu-Hu DC project,the idea of using resistance-capacity combined with restraining straight and a step-by-step governance strategy is proposed to realize the protection of the power grid system.On this basis,in order to ensure that the installation of the R-C device has the least impact on the system operation.This paper analyzes from 3 aspects of the DC protection effect,insulation voltage level and the protection impact to choose the RC parameters;finally,the equivalent DC model of the AC system is established.Through calculation and analysis,the bias current of the transformer is controlled within the threshold range,which achieves the expected protective effect.