Actual Measuring System Development For Lightning Current Caused By Direct Lightning Strikes To Transmission Line Towers

Transmission lines in the electrical power system often suffer direct lightning strikes. The direct lightning current always discharges into ground through Transmission line towers, no matter whether the lightning strikes to the tower top or the lightning wire. Therefore, quantificationally studying the lighting current flowing through the towers is an effective way to achieve lightning current parameters, providing important raw data for anti-lightning engineering design for the electrical power system and constituting the indispensable foundation of improving anti-lightning level of Power transmission lines.Methods developed to measure the direct current lightning parameters are introduced in this paper. And then, this paper emphatically describes the design and implementation of a measuring system of lighting current caused by direct lightning strikes to Transmission line towers. The function of this system is to measure and restore the waveform of the direct lightning current which discharges into ground through Transmission line towers. This system constitutes itself with a sensing head, a data acquisition unit, a upper computer software and a solar power supply unit. Firstly, the Rogowski coil sensing head is introduced, whose measuring error is less than3%and whose measuring range is-100kA～+100kA. Secondly, the data acquisition based on FPGA is introduced, which can acquire the lightning current waveform of the starting25.6us covering the total wave front time and a part of wave tail time with bipolarity and14bits sampling size. Thirdly, the upper computer software is introduced, which contains three functions of communication, waveform display and textfilter and provides friendly man-machine interface for the system. Fourthly, the solar power supply unit based on AVR is introduced, which needs one and a half days to be charged from over-discharge to top-off, and then, can maintain its power supply for two days without illumination. Lastly, the running test of the whole system is introduced, which uses a reactor discharge circuit to generate the HF large current and uses self-developed solar battery as its power supply. The test result indicates that the system can accurately restore the waveform of the current to be measured.