Lightning Overvoltage Calculation And Its Effect On Monitoring Equipments In Substation

To realize efficient allocation of energy and build reliable power transmission network, high voltage transmission will be the future of power grid. The overvoltage in the substation is not only related to the reasonable design of the electrical insulation, but also the safe and reliable operation of the power system. The overvoltage is basically divided into internal overvoltage and external overvoltage, where the external overvoltage mainly refers to the lightning overvoltage. This paper mainly focuses on the calculation of lightning overvoltage and its influence on the electrical equipment monitoring system.This paper analyzes the impact characteristic of transmission line, tower and equipment in substation and chooses appropriate simulation models and parameters. According to the rules and characteristics of lightning, the equivalent circuit and the simulation model of the lightning current can are determined, especially for the peak current and wave parameters. Analyze the various models of tower used at present, choose to use the lossy multi wave impedance model. Use different line models for incoming line, line terminal and other lines. Three kinds of insulator flashover criteria are analyzed, and the new model of Japan is adopted as the insulator flashover criterion. Use subsection index method to describe the voltammetry characteristics of MOA model. According to the simulation model and actual parameters of the equipment based on actual 500kV substation, the lightning impact model of the substation is built in the ATP-EMTP software. Come to a conclusion that the most serious operation mode is single outline,single bus and single transformer. And the lightning protection validity of the surge arrester in the middle bus bar is verified. Analyze the influence of strike point, grounding resistance of tower and distance between arrester and transformer. Come to the conclusion that reduce #2 tower grounding resistance can reduce voltage amplitude and surge arresters must set around the transformer as close as possible.Finally, the influence of the electric field and the strong magnetic field produced by the lightning strike is studied. Take the external UHF GIS PD monitoring sensor as an example, analyze the influence of electric field and magnetic field distribution of GIS tank external on PD monitoring sensor by simulation. The result shows that the electric field can’t influence the outside environment of GIS as the material of the tank is metal and properly grounded, while the magnetic field still exists in the outside space of GIS. By analyzing the equivalent circuit of UHF PD sensor and using MagNet software to simulate, the inducted voltage can reach to 323V by the magnetic field distribution of GIS tank. It will cause strong damage to the weak power system. So in order to keep safe operation of this monitoring system, it is important to take some protective measures.