Extraction And Simulation Analysis Of The Transient High Frequency Signal In500kV Substation

Sustained and rapid development of China’s economy, promoted the rapid development of power industry, and increased the size of the extra-high voltage power grid (500kV voltage), which has become the backbone network. The extra high voltage transmission lines are easily affected by lightning, snow and ice and other natural disasters, because the lines are long and often pass through high mountains and hills, what’s more, line tower is very high, and span is long, with some lines rod twice or even more back. The lightning current is very large, which can reach thousands of amperes, sufficient to cause the strong electromagnetic effect and thermal effects, affecting the stability of power grid, and threatening the personnel safety.500kV transmission system uses capacitor voltage transformer, while the high frequency transfer characteristic of the transformer is poor so that the capacitor voltage transformer can not transfer high frequency overvoltage signals produced by lightning line correctly, so the fault routine recorder can only record the steady and low frequency fault transient, cannot record high frequency fault transient caused by failure and lightning, thus it will not be able to achieve the analysis of high frequency signal, so it is necessary to adopt the high frequency transient signal recording and analysis devices, which can record the extra high voltage transmission line transient operating data real-time, and provide statistics and informative data for the safe operation analysis of power grid.In the second chapter, transfer characteristics of electromagnetic voltage transformer, electromagnetic current transformer and capacitor voltage transformer are analyzed, and experiments show that electromagnetic voltage transformer and current transformer, with good high frequency transfer characteristic, can transfer high frequency signal below100kHz, and the simulation of capacitor voltage transformer, shows that the high frequency transfer characteristic of capacitance voltage transformer is poor. Therefore, to collect the high frequency voltage traveling wave signal, caused by lightning500kV lines, the indirect measurement method must be adopted. The third chapter analyses and compares the two kinds of high frequency signal extraction methods. The fourth chapter of this paper makes a simulation analysis of500kV system under various conditions of lightning. The results shows that the amplitude of overvoltage is significantly reduced when the arrester is used. By using small CT socketed at the grounding line of CVT, the transient high frequency voltage signal can be indirectly measured. So the high frequency lightning overvoltage signal can also be effectively obtained.