Research On Overvoltage And Insulation Coordination Of 500kv Substation

With the development of social economy and the increase of the demands for electricity, EHV transmission has been a trend in the power grid development. The study of EHV substations overvoltage is an indispensable research to the development of the power grid, which influences the design of the insulation strength of power equipments and the reliability of the power system. Simulation, field test and calculation are three common methods of studying the EHV substations overvoltage. In this paper, ATP-EMTP is applied.The lightning overvoltages of a substation are calculated ,respectively using ATP-EMTP and field test methods. The results show that the lightning overvoltages calculated with ATP-EMTP and field test methods respectively are very close, which validate the ATP-EMTP method.The stimulation model of the lightning overvoltages are built. The magnitude and time tf of lightning invasion wave, the equivalent entrance capacitance of main power equipments, U-I characteristics of MOA, the tolerance degree of power equipments under surge voltages, and wave impedance are acquired. Based on the arrangements of main electrical connection and distribution equipments, the lightning overvoltages are calculated in five different operation modes. The results show that all the lightning overvoltages in five operation modes meet the demands for the insulation coordination of the lightning overvoltage. By changing the parameters, U-I characteristics of MOA, waveform parameters of lightning invasion wave, the entrance capacitance of power equipments, and the electrical distance between MOA and protected equipments are found to have some impacts on the lightning overvoltage of power equipments in the substation.Switching surges are calculated respectively when closing one-generator- one-transformer line with closing resistor, one-generator- one-transformer line without closing resistor and two-generator-two-transformer line and re-closing one-generator- one-transformer line. By drawing histograms, the distribution of overvoltage magnitude is acquired. The energy absorbed by MOA is calculated. The conclusion is that switching surges in four diferent modes meet the demands for the insulation coordination.