变电站直流系统接地故障解析及新型检测方法的研究

直流系统接地对变电站安全运行影响甚大,当前针对直流绝缘的监测方法存在不能实现故障分支定位、在特定情形下无法准确报警等诸多不足,需要加以改进。首先对直流接地成因和危害展开分析。其次,充分考量故障定位准确、检测精度提升、零漂影响规避等多重因素,在直流漏电流法中吸纳动态差值法的核心思想,以检测电阻两次投切为主要手段构建新型直流系统绝缘监测架构,并给出用于辨识绝缘优劣的相关电气量计算公式。再次,通过模拟故障检验、实际案例证明等方式,表征本文方法的可行性。实证结果是:采用所提方法,关于母线绝缘电阻和支路绝缘电阻的实时感知的相对误差分别不大于2.96%和2.49%,均大幅小于5%的国标要求。因此研究表明:借助动态差值法进行变电站直流系统绝缘的在线监测,不但对系统安全运行无影响,还消除了检测死区,克服了由于传感器零漂带来的漏报、误报可能,使直流系统运检技术迈上一个新的台阶。

Analysis of grounding fault in DC system of substation and research on new detection method

The grounding of DC system has a great impact on the safe operation of substation.Current monitoring methods for DC insulation have many shortcomings,such as failure branch location,inaccurate alarm under specific circumstances,which need to be improved.Firstly,the causes and hazards of DC grounding are analyzed.Secondly,considering the multiple factors such as accurate fault location,improved detection accuracy and zero drift influence avoidance,the core idea of dynamic difference method is absorbed in DC leakage current method,and a new insulation monitoring framework of DC system is constructed by two switching of detection resistance as the main means,and the related electrical used to identify the insulation quality is given.Quantity calculation formula.Thirdly,the feasibility of this method is demonstrated by means of simulation fault test and actual case proof.The empirical results show that the relative errors of real-time perception of bus insulation resistance and branch insulation resistance are less than 2.96%and 2.49%respectively,which are significantly less than the national standard requirements of 5%.Therefore,this research shows that the dynamic difference method not only has no influence on the safe operation of the system,but also eliminates the dead zone of detection,overcomes the possibility of missed and false alarm caused by zero drift of sensors,and makes the DC system operation and inspection technology to a new level.