天山—中州特高压直流输电工程投运后河南电网主变直流偏磁分析及抑制

DC Bias Analysis and Suppression of Transformers in Henan Power Grid After Tianshan-Zhongzhou UHVDC Transmission Project Commissioning

±800 kV天山—中州(简称天中)特高压直流输电工程投运后,直流系统一旦出现单极大地或不对称运行方式,很大的入地电流就会对河南电网产生不利影响。为此,结合河南电网实际运行情况,建立了河南电网直流偏磁分析模型,分析了主变直流偏磁分布特性,并结合现场实测,制定了河南电网直流偏磁分级防护治理方案,研制了带可靠返回系统的电容型直流抑制装置并挂网运行。研究结果表明:直流偏磁电流的大小主要受地表电位分布的影响,同时还受变电站间距离及出线数量的影响,需特别关注站间距离远、出线数量少的变电站直流偏磁问题;应对直流偏磁超标的变电站进行治理,同时对受直流偏磁影响显著的变电站加强直流偏磁监测;所研制的带可靠返回系统的电容型直流抑制装置,实现了控制系统断电时旁路保护的可靠动作,有效地治理了220 kV明河变电站直流偏磁超标的问题,确保了河南电网的安全可靠运行。这些研究结果有效地解决了天中特高压直流输电工程投运对河南电网主变直流偏磁的影响。

A large DC earth current will have a negative impact on Henan power grid, when -4-800kV Tianshan-Zhongzhou （Tianzhong） UHVDC transmission project operates in ground-return mode or asymmetric operation mode. Therefore, based on the practical operation of Henan power grid, a simulation model to analyze the DC bias was established. According to the measured results on site, the DC bias classification protection of Henan power grid was made. The capacitive-type DC suppression device with reliable return system was developed and operated in Henan power grid. The results show that the magnitude of the DC bias current is mainly affected by the surface potential rising distribution, also affected by the distance between the substations and the number of outlets. Special attention should be paid to the DC bias of the station which is far away from other station and have less outlets. The principle of classified protection is that the station of which DC bias exceeds the standard needs to be suppressed, and substation with significant DC bias needs to be further monitored. The capacitive-type DC suppression device which has a bypass protection will reliably operate when the control system is de-energized. When this capacitive-type DC suppression device is adopted in the 220 kV Minghe substation, the DC bias is effectively suppressed, and the safe and reliable operation of Henan power grid is ensured. Therefore, the influence of DC bias to the transformer of Henan power grid can be effectively solved after Tianzhong UHVDC transmission project commissioning.