Research on Switching Overvoltage of No-load Transformer with Long Cable

Abstract

In order to find out the regular and influencing factors of switching overvoltage in the process of power plant grid connection, so as to provide technical basis for the operation mode of switching on no-load transformer with long cable in the later process of power transmission, firstly, the mechanism of overvoltage generated in the process of switching no-load transformer is studied, and its nonlinear working area is calculated based on the actual test data of transformer, and then the equivalent modeling of a 500kV power plant is built up on EMTP (Electro-Magnetic Transient Program), the transient characteristics of overvoltage generated by switching on no-load transformer are simulated. Finally, taking XLPE (Cross linked polyethylene) cable on the high-voltage side of transformer as variable, the influence of XLPE cable on the overvoltage generated by switching no-load transformer is studied, and suggestions for suppression are put forward. The results show that obvious overvoltage of no-load transformer will be produced in the process of power plant grid connection. Under the switching angle 00, the maximum overvoltage can reach 1.69p.u. The length of XLPE cable has no obvious effect on excitation inrush current, but has influence on overvoltage.