电力系统中性点接地方式的选择是一个综合性问题，它与系统运行的可靠性、绝缘配合、继电保护、通讯干扰、电气安全及接地装置的选择息息相关。中压配电网的中性点普遍采用非有效接地运行方式，当中压配电网发生单相接地故障时，若故障点容性电流较大，可能会产生弧光并引起过电压，对系统的安全运行造成威胁。因此当中压配电网故障点的容性电流大于规定值时，需要在中性点安装消弧线圈，利用消弧线圈产生的感性电流对故障容性电流进行补偿从而达到灭弧的效果。所以，准确的测量中压配电网的对地容性电流对于选择中性点运行方式以及确定安装消弧线圈容量等具有重要的意义。 为了能够更好的测量中压配电网的容性电流，本文首先对三频法、扫频法、相量法、和改进注入信号法等中压配电网容性电流测量原理进行深入分析，并给出各个方法的测量精度以及适用范围。其次，由于现有测试容性电流的方法中，没有给出注入信号频率以及信号的强度的理论分析，同时，现有的方法中也忽略了反馈电压信号中含有工频以及高频等噪声信号的影响。因此，论文中对注入电流信号的强度及频率、互感器的传变特性进行了理论分析及仿真验证，根据仿真结果，得到合适的注入信号的强度及频率。最后考虑到实际配电网在运行中有各种工频、谐波、间谐波、噪声等干扰存在，而PT二次的的反馈电压信号幅值较小，容易受到影响，因此，利用相敏检波器，从干扰中对反馈电压的幅值和相位进行提取，仿真结果表明相敏检波器能够较为准确的提取信号，使得测量的结果更为准确。

The choice of power system with neutral grounding method is a comprehensive problem, it is closely linked to the operation reliability of power system, insulation coordination, relay protection, communication interference, electrical safety and the choice of grounding devices. The non-effective grounding operation mode is generally used in neutral point of the medium voltage distribution network. When the single-phase grounding fault occurs in the distribution network, it may produce arc and lead to an overvoltage, which is a threat to safety operation of the system if the capacitive current of fault point is out of limit. Therefore, when the capacitive current of fault point is greater than the specified value, we need to install arc suppression coil in neutral point, which produced inductive current to compensate the capacitive current of fault point so as to achieve the extinction of arcing. So, the accurate measurement of grounding capacitive current in medium voltage distribution network is significant to select the operation mode of the neutral point and as well as determine the installed capacity of arc suppression coil. First of all, in order to measure the capacitive current in power distribution network more accurately, this paper analysed the measuring principles deeply, such as Three Frenquency Method, Frequency Swept Method, Phasor Method and Improved Signal Injection Method etc. And then concluded the measuring accuracy and the applicable scope of each method. Secondly, due to the current measuring methods of capacitive current does not give the theoretical analysis about choices of injection signal in frequency and intensity, and also ignore the influence of feedback voltage signal which contained the noise in power frequency, therefore, this paper has carried on the theoretical analyses and simulation verification of the injection current signal intensity and frequency, and the PT's characteristics of transimission and change. According to the results of simulation, we concluded the appropriate injection signal strength and frequency. Finally, considering the actual distribution network in the operative mode, there were all kinds of power frequency, harmonic, harmonic and noise interferences existed, and the feedback of PT secondary voltage signal amplitude which was easy to be affected was small, therefore, made use of phase sensitive detector to obtain the interference voltage amplitude and phase from the feedback signal. The simulation results showed that the phase sensitive detector could be relatively accurate extraction of signal, which made the measurement become more accurate.