Application Of Bergeron Method In The Lightning Over-voltage Calculation Of 500kV Power System

500kV substations are the load-center substations in power systems that have the important status in the whole electric network. Once these load-center substations are damaged by lightning stroke, safe operation of large electric network and main electric network would not be insured. So reliable measures against lightning stroke are necessary. There are two source of lightning stroke damage in a substation: direct lightning stroke and lightning incoming surge. Because the chances of directly lightning stroke on lines are more than the chances of directly lightning stroke on substation, lightning incoming surge that intrudes the substation along the lines are one of the main minatory modes to electrical equipments of substations.According the simulation calculation of over-voltage by lightning stroke to the electrical equipment of substations, we can find out the rule of over-voltage's distribution and change so as to refer valuable consultation and optimize the projection design of substations.Firstly, the significant meaning and developing state of lightning over-voltage calculation of the power system are presented in this paper. Moreover analysis of basic theories and methods are given in this paper too. Among them, Bergeron method has the greatly significance in calculating lightning over-voltage. Based on the Bergeron method, a mathematical model for transmission line, capacitance, inductance and resistance are set up. The distributed transmission line model are represented by the parallel connection of a resistance and a isotonic current source.Two terminals' electric quantities are independent on topological structure, they are connected by the historical records of the isotonic Current source. So, it is more simplified and easy to be programmed. Based on the mathematical models above, this paper made a program synthesizing the substation and its incoming lines, and distinguishing the near lightning stroke and the far lightning stroke to calculate and analysis the lightning over-voltage of the 500kV Mojiang substation. The results could be consulted when lightning protection design of the substation is set about, and it can also be the reference in some other similar cases.