A Taking Power Method Based On High-voltage Capacitor And Research On Lightning Transient Effects

Along with the smart grid proposed, smart transmission lines is gradually entering the builders’vision as an important part of smart grid, installing various testing equipment on transmission line tower is the basis of the construction of smart transmission lines. However be restricted by geographical conditions or insulation conditions, there is very few low-voltage power supply near line towers, supplying power to detection equipment on the tower has become a big problem. This paper presents a taking power method based on high-voltage capacitor, which is suitable for line tower. The method directly takes power from high-voltage wire by using a specially designed capacitor in series with voltage transformer, insulator strings connects in parallel with high-voltage capacitor and voltage transformer as insulation support of transmission line overvoltage. The device can output stable power to tower-monitoring equipment, but it will inevitably be struck by lightning; Therefore, study on over-voltage transient characteristics under lightning and overvoltage protection technology so as to ensure the safe and reliable operation are very important.The main contents of this thesis are as follows:(1) On the basis of explaining high voltage capacitor principles, this paper designed the 110kV high-voltage capacitor and power conversion circuit. According to insulation coordination requirements, insulation tests standards for high-voltage capacitor were developed. Insulation test results show that high-voltage capacitor’s inner insulation and outer insulation meet line insulation levels; AC test results show that its capacities meet power requirements; it runs well under overvoltage state, the device can output stable power to tower-monitoring equipment; setup plan has been designed and on-site installation verify its feasibility.(2)The research object of this paper is the new development of 110kV transmission line tower capacitive power system, established lightning transient simulation model of power system, determined the level of lightning over-voltage on power system by using Alternative Transient Program ATP-EMTP software and proposed overvoltage protection measures. Simulation results show that using zinc oxide lightning arrester and pressure-sensitive resistor could be effective in limiting amplitude of lightning over-voltage, realize the over-voltage protection for power system.(3)According to the actual installation environment, this paper simulated transient characteristics under different external excitation(lightning tower, line grounding fault), the simulation results show that lightning tower is the most severe overvoltage conditions appeared to power supply device, power supply device which adds protection measures can run safely under lightning tower, single-phase grounding fault and two-phase earth fault; and further studied its actual effect on line lightning protection. power supply device has less impact on lightning withstand level of transmission line.