中压电网为了提高运行可靠性，普遍采用小电流接地系统，即中性点不接地、谐振接地和中性点经高阻接地系统。当发生单相接地故障时会在接地点产生一定的容性电流，在线路绝缘薄弱处，易产生弧光。间歇性的弧光放电会产生过电压，引起绝缘破坏，发展为相间短路甚至三相短路。因此中压配电网需要准确测量容性电流大小，合理的配置消弧线圈的容量，从而减小容性电流的危害。 文中建立了中压配电网的仿真模型，给出了电网各模块的参数值，包括三相电源、分布式线路和饱和电压互感器等，并对全网容性电流进行了工程计算。在此基础上，对目前普遍使用的测量方法，如单相金属接地法、中性点外加电容法、信号注入法进行了误差分析，并从测量原理、局限性、安全性等角度进行了比较，对从消弧线圈的PT二次侧注入的变频信号法进行了改进，通过仿真验证了改进后的测量精度有所提高。此外，结合测量方法原理给出容性电流现场测试安全注意事项、测试接线和测量步骤等。最后，选取从PT开口三角形侧注入的定频法进行研究，分析了非线性负荷引起的系统不对称和波形畸变、信号传输衰减等问题对测量结果的影响，研究表明，合理地选择注入信号强度和注入频率范围，可减小测量误差。论文的研究成果对现场测试和测试仪器的研制有一定的参考价值。

Small current neutral grounding systems, namely, isolated neutral system, resonant earthed system as well neutral grounding system via resistance, are widely used to improve the operational reliability of the medium voltage power network. When single - phase earth fault occurs, it’s prone to produce capacitive current on ground point and arc light on weak section of insulation line. The intermittent arc light can develop into overvoltage which results in insulation breakdown and causes phase fault even three phase short circuit, so the size of capacitive current needs to be measured precisely and the capacitance of extinction coil ought to be allocated rationally to cut down damages of capacitive current. In this paper, firstly, a simulation model of power supply system with 6kV is built by SIMULINK, parameter values of each module, including three-phase supply, distributed circuit, potential transformer and so on are offered to operate engineering estimating of the capacitive current for the whole power system, on the basis of which error analyses for common used measuring methods, such as single phase metal grounding method, additional capacitance method, as well signal injection method, are conducted adding to the comparison and contrast of those methods from the aspects of measuring principle, limitation, safety, etc. The innovation of this paper lines in the increase of measurement accuracy for variable frequency signal injection method which is tested and verified by simulation experiment. Secondly, connections and measurement steps of capacitive current on spot test are stated with accuracy and clearness. Thirdly, the influence of problems caused by nonlinear loads, like system asymmetry, waveform distortion, signal transmission attenuation, etc, on constant frequency signal injection method are analyzed and studied in the paper. Studies reveal that the rational selection for the injection of signal intensity and frequency range can reduce measuring errors. Findings of this paper have a promising reference value for spot tests as well development for the measuring and test instruments.