Research On No-Load Switching Overvoltage Of1000kV Ultra High Voltage

UHV transmission lines because of its parameters, system capacity or other.features make the overvoltage more serious than EHV Transmission Line. In addition, the insulator of it can withstand overvoltage level is low, it is easy to cause the insulator breakdown or equipment damage, cause huge economic loss, so conduct the research for overvoltage and take effective measures to reduce the overvoltage level is one of the important topics of UHV grid.In this paper, Taking China’s first UHV AC transmission lines as the background, analyzes the mechanism of no-load switching overvoltage of it, the factors influence the switching overvoltage and the limiting measures commonly used. Building the equivalent model of line and calculate the switching overvoltage by the improved Euler method; the calculation tool is Visual Basic6.0, then get the results. Finally, using the electromagnetic transient program EMTP to simulate and analysis, so that to verify the calculation is true and viable in the process of thought, derivation and solution.Results showing, the overvoltage as high as2.5times when switch close at peak voltage, it as high as2.6times when residual voltage is biggest and opposite, it more than3times when Three-phase breakers closing in different period. In addition, install the series compensation capacitor which compensation degree was about20%-40%in the middle of the line, install the shunt reactor which compensation degree more than80%on both ends of the line, install two levels parallel resistances in the breaker and install lightning arrester along the transmission line, etc. these measures all can reduce switching overvoltage and make it meet the demand of the UHV transmission linesThe paper enrich the basic theory and analysis method on switching overvoltage of UHV no-load transmission lines, it has great importance to science research and engineering design of UHV transmission technology.