Application Of Conversion Technology In Large-scale Grounding Inpedance Measurement

With the growing maturity of China's electric power system, grounding impedance measurement has getting more and more attention and become a major issue for the safe and reliable operation of power systems. The national《power industry standard DL/T 475-2006》and《the transfer of electrical test equipment standard GB50150-2006》both require the grounding impedance measurement. China usually carry out the test as soon as possible after the completion of construction according to《earthing construction and acceptance of GB50169-2006》in order to arrange time to reconstruct it.Ground state of the device is directly related to the safe operation of power systems. It is very important to make a scientific and rational test for a variety of parameters for the grounding device and make an accurate evaluation of its condition.《power industry standard DL/T 475-2006》recommends the use of different frequency current method to test the frequency of large grounding device parameters and with more attentions from the industry, the current inverter technology at home and abroad grounding impedance measurement has been widely used and has good results. During the construction of the substation, the qualification of the laying of the ground network has something to do with the safety of the operation of the equipment and personal safety. The size of grounding impedance is the only measurement for the qualification of the grounding laying. For large grounding device for substation, the grounding impedance test is the most important work. But much interference caused by the dense and complex network structure seriously affects the accuracy of the test results.In this paper, firstly, by comparing with the traditional method of ground resistance testing, we use the grounding of a large selection of frequency 30°angle method. And then the paper describes the experimental ground impedance test procedures, after that the article focuses on the grounding impedance test procedures, equipment operation and note.At the end of the paper, it provides the experience for wide use of the ground impedance test and the several solutions to the too-large ground impedance.