基于无线传输相位差比较的变电站接地网地线分流向量及接地阻抗准确测量

Accurate Measurement of Ground Wires Current Division Vectors and Ground Impedance in Substation Based on Phase Comparison of Wireless Transmission

为避免运行变电站地线分流简单向量模值相加的处理方法带来的接地阻抗测试系统性误差,提出了基于相位无线传输原理的地线分流测量技术。在测量点实时采样记录异频测试电流幅值和相位作为基准波形信号,将波形向场区无线发射,同时,在出线构架各基脚处接收该信号,用柔性Rogowski线圈测量各构架基脚所流过的异频电流向量的相位差,用测试电流参考向量减去分流向量和,得到通过接地网散流的实际电流。所开发的DF9600测量系统现场比对测量结果显示提出的向量和处理方法,较之现行的简单分流向量模测量值相加的方法计算接地阻抗更为准确;无线传输技术较好地解决了相位差的测量问题,且能甄别出地线分流和构架间的环流。

Simply summing the shunt vectors modulus values of the grounding wires while measuring the grounding impedance of operating substation may cause systemic error. To avoid this error, we proposed a measuring method based on wireless transmission principle. Firstly, the amplitude and phase of the different-frequency test current were recorded at the measuring point in real time as a reference waveform signal, and the current waveform was transmitted to the field outlet structure wirelessly. These signals are collected at the structure foots, from where the phase difference of current flowing was measured using flexible Rogowski coils. Then, the shunts vector was subtracted from the tested current vector to acquire actual injecting current through grounding network. Finally, a measuring system, DF 9600, was developed, by which measurement results were more accurate than those by the method that simply sums the module value of the shunt vectors in the grounding impedance calculation. Moreover, the wireless transmission can properly solve the problems in measuring the phase differences, and can distinguish the shunt current of grounding wires from the circulated current of structures.