有效掌握配电网对地电容电流的基础数据，定期开展消弧线圈装置校核，是确保配电网安全稳定运行的重要工作。根据电力部门的相关规定，对于不与发电机直接相连的6~20的系统，当其发生单相接地故障时，如果电网对地电容电流小于或等于10A，可以采用中性点不接地方式；如果电网对地电容电流大于10A，宜采用中性点经消弧线圈接地方式。所以，准确测量中压配电网对地电容电流对于合理选择中性点接地方式和正确选择消弧线圈容量具有重要的意义。

本文对信号注入法测量中压配电网对地电容电流的相关技术进行了研究。首先，对现存主要的信号注入法，如扫频法、三频法、相量法、综合法和高频法的测量原理进行了详细的阐述，并且对它们的适用范围、优势以及局限性进行了综合比较。然后，对综合评价较好的综合法进行更深入的研究，针对综合法存在中压配电网等效模型的合理性、谐振频率难以确定、谐振频率搜索时间过长，以及谐振频率过低时，受电压互感器励磁支路的影响等不足进行了合理的改进，即根据中压配电网的频率特性，改进中压配电网的等效模型；根据串联谐振的特征信息，提出变步长同相搜索法；通过在电压互感器开口三角侧串联合适的电容，把系统的谐振频率控制在合适的范围，减少电压互感器励磁支路的影响。接着，以准确性和安全性为原则，对改进的综合法的关键参数进行合理选择。最后，考虑到实际配电网中的工频信号和零序性质的谐波信号对测量结果的影响，结合注入信号的频率已知这一特点，设计了数字式互相关器消除干扰信号对测量结果的影响。通过仿真验证，改进的综合法具有操作方便、安全性好、适用范围广、测量速度快和测量准确等优点。

Effectively grasping the basic data of the capacitance current of the distribution network to ground, and regularly conducting the check of the arc suppression coil device are important tasks to ensure the safe and stable operation of the distribution network. According to the relevant regulations of the power department, for a 6~20kV system that is not directly connected to the generator, when a single-phase ground fault occurs, if the power grid to ground capacitance current is less than or equal to 10A, the neutral point ungrounded mode can be used, if the power grid to ground capacitance current is greater than 10A, the neutral point should be grounded via the arc suppression coil. Therefore, accurate measurement of the capacitance current to ground of the medium voltage distribution network is of great significance for the reasonable selection of the neutral point grounding method and the correct selection of the arc suppression coil capacity.

This paper mainly researches the related techniques of measuring the capacitance current to ground of the medium voltage distribution network by the signal injection method. Firstly, the measurement principles of the main existing signal injection methods, such as the frequency sweep method, tri-frequency method, phasor method, comprehensive method, and high frequency method are explained in detail, and their scope of application, advantages, and limitations comprehensive comparison. Then, the further study of the comprehensive method with better comprehensive evaluation is carried out. Aiming at the rationality of the existence of the equivalent model of the medium voltage distribution network in the comprehensive method, the difficulty of determining the resonance frequency, the search time of the resonance frequency being too long, and the low frequency, the insufficiency of the voltage transformer excitation branch and other deficiencies were reasonably improved, that is, the equivalent model of the medium voltage distribution network was improved based on the frequency characteristics of the medium-voltage distribution network. Based on the characteristic information of series resonance, a variable step size was proposed In-phase search method. By connecting a suitable capacitor in series with the triangular side of the opening of the voltage transformer, the resonance frequency of the system is controlled in a suitable range to reduce the influence of the excitation branch of the voltage transformer. Then, based on the principles of accuracy and safety, the key parameters of the improved comprehensive method are reasonably selected. Finally, considering the influence of the power frequency signal and the zero-sequence harmonic signals on the measurement results in the actual distribution network, combined with the characteristics of the frequency of the injected signal, a digital cross-correlator is designed to eliminate the impact on interference signal to the measurement. Through simulation verification, the improved comprehensive method has the advantages of convenient operation, good safety, wide application range, fast measurement speed and accurate measurement.