谐振接地配电网对地绝缘参数双端谐振测量新方法

为解决谐振接地配电网对地绝缘参数测量过程中电压互感器漏阻抗和中性点对地支路阻尼电阻导致的测量误差问题,提出了谐振接地配电网对地绝缘参数双端谐振测量新方法。采用双电压互感器,通过消弧线圈内部电压互感器或零序电压互感器向配电网注入变频恒流特征信号,并从另一电压互感器测量返回的特征频率电压信号,对含阻尼电阻的零序谐振回路进行等效变换,搜索准确的系统谐振频率,实现了系统对地电容和对地泄漏电导的精确测算。该测量方法的电流注入与电压测量单元共同直接作用于对地绝缘参数支路,从原理上消除了电压互感器漏阻抗和系统阻尼电阻的影响,大幅提升了对地绝缘参数测量精度。在PSCAD/EMTDC仿真环境及某变电站10 kV侧对提出的对地绝缘参数实时测量技术进行了仿真分析与现场实验验证。分析结果表明,该方法测量精度高,不影响配电网正常供电且参数测量过程安全快捷、操作简便。

A Novel Double-terminal Resonant Measurement Method of Insulation-to-ground Parameters for Resonant Grounding Distribution Network

In order to solve the measurement error problems of insulation-to-ground parameters for resonant grounding distribution network caused by the leakage impedance of voltage transformer and damping resistance of neutral grounding branch, a novel dual-terminal resonant measurement method of insulation-to-ground parameters for resonant grounding distribution network is proposed. This method utilizes dual voltage transformer. A characteristic constant current signal with variable frequency is injected into distribution network through either the internal voltage transformer of the arc-suppression coil or zero-sequence voltage transformer while the returned characteristic-frequency voltage signal is measured by another one. After the equivalent transformation of zero-sequence resonant circuit with damping resistance, the system capacitance to ground and leakage conductance can be accurately calculated by searching the precise resonant frequency of the system. Both the current injection and the voltage measuring unit of the proposed method directly act on the branch of insulation-to-ground parameters, which eliminates the effect of the leakage impedance of voltage transformer and damping resistance and greatly improves the measurement accuracy of insulation-to-ground parameters. The proposed real-time measurement technology of insulation-to-ground parameters is simulated, analyzed and verified in PSCAD/EMTDC simulation environment by field test in a 10 kV substation. The analysis results show that the proposed method has high measurement accuracy. The parameters measuring process has no impact on the normal power supply of distribution network, and is safe, fast and easy to operate.