直流偏磁对变压器保护的影响及直流偏磁保护改进

Influence of DC Magnetic Bias on Transformer Protection and Improvement of DC Magnetic Bias Protection

随着高压直流输电工程的建设,直流系统对周边电力设备的影响逐步受到关注。当直流系统单极大地运行或直流控制系统出现异常时,可能产生较大的直流电流注入相邻变压器。此时变压器可能产生直流偏磁。文中通过对变压器几种磁饱和特性的对比指出了直流偏磁的特殊性,结合现场波形特征分析直流偏磁及常见的偏磁抑制装置对保护设备的影响,指出现有直流偏磁保护判据存在的问题,进一步从直流偏磁出现的场景以及波形特征出发提出了对现有偏磁保护的多种改进意见。仿真及试验验证结果表明改进判据可有效提升直流偏磁保护的可靠性。

With the construction of high voltage direct current(HVDC)transmission projects,the influence of DC systems on the surrounding power equipment has been gradually concerned.When the DC system operates with monopole ground return mode or the DC control system is abnormal,arge DC current may be generated and injected into the adjacent transformers.At this time,the transformer may produce DC magnetic bias.Through the comparison of several magnetic saturation characteristics of transformer,the particularity of DC magnetic bias is pointed out.Combined with the characteristics of field waveform,the influence of DC magnetic bias and common magnetic bias suppression devices on the protection equipment is analyzed.The problems of existing DC magnetic bias protection criteria are pointed out.Based on the scenarios of DC magnetic bias and the characteristics of waveforms,several improvement suggestions on the existing magnetic bias protection are proposed.The simulation and test results show that the improved criterion can effectively improve the reliability of DC magnetic bias protection.