| Our country has a vast number in territory and population which decide the transmission lines’ extensive distribution. As the main artery of the power system, transmission lines spread the huge electricity to all the users around the country. As an important part of power system, the transmission lines’ reliable running directly affects the stable operation of all the levels of the power generation, power transformation, power transmission, power distribution, and power utilization. As an important cause of transmission lines’ operation failure, lightning releases huge energy during its discharging, of which voltage can be up to a million volts and instantaneous current up to hundreds k A. The high current can cause the insulator flashover even severely damaged, which will affect the normal operation of the power system. According to statistics, in 2008 China Southern Power Grid’s 110 k V and above transmission lines total 2599 trip, 1588 times among which are lightning trip, accounting 61.1% for the total trip number. As lightning accidents’ proportion of the total power grid’s accidents is so high, and transmission lines have particular characteristics like long distance, large span, mostly laid in the field and so on, it is hard to locate the fault point quickly and accurately, all above make great difficulties to the rapid troubleshooting of the power equipment. Although the current LLS can realize monitoring of ground flash density and intensity within a certain range, but locating the accurate position of tower which occurred to by lightning fault is still a problem, human investigation within a small range is still necessary by all means. Besides, current LLS cannot accurately reflect the exact size and waveform of lightning current that flows through the insulator string when lightning strikes the transmission lines. To solve these problems, the author designs the transmission line lightning fault wave-recording and positioning system.The thesis firstly introduces the domestic and foreign research situation of transmission line lightning fault wave-recording and positioning, the basic knowledge of lightning and the historical development of LLS are also mentioned, plus the principles of LLS and methods of wave-recording and positioning. Then the design scheme of transmission line lightning fault wave-recording and positioning system is described in detail, including online monitoring terminals, the staff on duty, monitoring center and mobile phone communication network in four parts.Online monitoring terminals are installed in transmission line near to the insulator string fitting side, it uses MSP430 microcontroller as the main control chip, the power supply unit adopts the way of mutual inducted energy-extracting & lithium battery. The author designs lightning current Rogowski coil, which is installed in fittings, as current sensor to monitor the lightning current that flows through the insulator string. 3G network is used to realize the data transmission between online monitoring terminals and monitoring center. When lightning strikes the transmission line and causes the insulator’s flashover, the current sensor will capture the lightning current signal and send it to online monitoring terminals to complete AD conversion, then 3G module will be called to send the wave data of lightning current to monitoring center through 3G network, the alarm message will be sent as well, including detailed information such as line name, tower number, phase of insulator string and so on.The designed transmission line lightning fault wave-recording and positioning system has passed through the professional test of EMC, IP rank and so on. The system now has been successfully installed and run in Inner Mongolia EHV Power Supply Bureau. This system can help the power department quickly locate the fault point in transmission line when it is struck by lightning, and record the lightning current waveform for study, so this system can provide convenience for rapid repairing on transmission line. |
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