Overvoltage Analysis Of The Ultra High Voltage Transmission Line

Ultra High Voltage power transmission has its advantages in long distance, large capacity and low loss. It is an effective approach for optimizing energy resource's distribution and has comprehensive benefit for the society and economy. At the same time, the development of UHV power grid can promote the technical upgrade of innovative electrical technology and manufacture. The construction of UHV power grid is imperative under the situationThe investigations of mechanism and restraining method of UHV power system's overvoltage have large technical benefit for the UHV's development.Frequency overvoltage, as one of inner overvoltages, plays a large role in UHV power system. It mainly includes the voltage caused by long line's capacitance effect, overvoltage caused by asymmetric fault, and overvoltage caused by shedding load. This paper discusses the frequency overvoltage and its retraining method through digital simulation based on our country's first UHV AC demonstrate project which goes from Jin Dongnan to Jingmen via Nanyang.Switching overvoltage is a main factor for determining power system's insulation level. This paper discusses several typical switching overvoltage including overvoltage caused by switching on line with no load, overvoltage caused by single phase auto-reclosing, overvoltage caused by single phase grounding fault, overvoltage caused by switching off transmission line. The factors such as operation mode, shunt reactor compensation degree, switching on resistor are analyzed. The switching on resistor's maximum thermal capacity and its distribution scheme are fixed on through calculation.There exists serious induced voltage and current on the maintenance line while the other circuit transmission line is on operation for the double circuits on the same tower. This paper elucidated the mechanism of induced voltage and current. Take Japan's UHV double circuits on the same tower as an example, it also investigate the line's length, shunt reactors, grounding switch's resistanceIn EHV and UHV power system, more than 90 percent of fault are single phase grounding fault from which nearly more than 70 percent are instantaneous. Single phase auto-reclosing is widely used in EHV and UHV power system for the sake of advancing power system's stability and reliability. Secondary arc current's extinction is a large problem in UHV power system owing to the line's long distance and high voltage. Circuit breaks will be switched on the arc ground fault resulting in the reclosing failure if the secondary arc cannot be extincted in time. This paper sums up the relative fruitful research results and gives some referential suggestions.