Research On Switching Over-voltage Triggered By Lightning Over-voltage In 1000 KV Power Grid

The ultra-high-voltage (UHV) transmission system takes an important part in China electrical power development. The energy resources in our country is the western and north much the east and south less. The UHV transmission system has become the trend of the development of the power grid. The over-voltage of the UHV transmission lines and substations is a subject in the development of UHV power grid. The main factors of the over-voltage are the lightning impulse voltage and the switching overvoltage. In this paper, the model of the lightning invasion wave over-voltage, switching over-voltage and switching over-voltage triggered by lightning invasion wave over-voltage have been established and simplified in the UHV transmission lines based on the software of Electromagnetic Transients Program-Alternative Transients Program (ATP-EMTP).In this paper, the principles of lightning invasion wave over-voltage and switching over-voltage is introduced respectively. And then established and simplified the two models for the over-voltage in the UHV transmission lines based on ATP-EMTP. The lightning invasion wave over-voltage mainly generated from the overhead incoming line near the substation of the Nanyang UHV HGIS is researched and simulated at first. Then it analyses switching over-voltage in 1000 kV power transmission system. At last, it puts forward the switching over-voltage triggered by lightning invasion wave over-voltage. Then Propose remedial measures for over-voltage.The simulation results:(1)The lightning over-voltage has much to do with the lightning point. What’s more, when the lightning stroked the power pole tower 2, the equipments in substation would be threatened seriously. The simulations are based on the lightning stroked the power pole tower 2. (2)Reducing the surged grounding resistance of the power pole tower could bring significance to limit over-voltage degree in the equipment of the substation. The electrical distance between the power transformer and the MOA disposes within 15m, the rational entrance capacitance of substation equipment are also effective measures. (3) In the transmission lines with no-load, when cut off the switch on the unfavorable points, the arc will not renew without the reactor. While closing the switch, the over-voltage oscillate, especially the switching angle is 0 degrees, the maximum over-voltage amplitude occurs. While the switching angle is 90 degrees, the over-voltage amplitude is the smallest. Parallel compensation line can be effectively suppressed arc voltage. (4) In the switching over-voltage triggered by lightning invasion wave over-voltage simulation, when the circuit breaker disconnect instantly, transient fault phase voltage increase. The nonlinear characteristic of primary arc is very strong, with strong random characteristics. The amplitude of the secondary arc increases obviously, basic rendering such as amplitude oscillations. The potential impact of secondary arc is much more serious than that without the chain reaction.Transmission line with lightning arrester installated and circuit breaker with closing resistors mounted can effectively restrain for the switching over-voltage triggered by lightning invasion wave over-voltage.