Eliminating Inrush Current in Transformers using a Residual Flux Control Algorithm

Abstract

Transformers in general turned on by changing the state of the circuit breakers at several times. Usually, the circuit breakers are closed at various times to turn on the transformers. This process results in high inrush currents due to the asymmetric flux produced in the coil. In light of these facts, the purpose of this study is to provide a method for controlling the switching instant that take place during the inrush of a power transformer.The general idea is to calculate the pre-existing magnetic fluxes remaining on the base legs in terms of the three phase voltages. Then, using these data and equations, the optimal operating time is calculated to ensure that the inrush currents are reduced, and adjustment parameters are determined within the controller to obtain the least time difference between the control signals. The system was completely simulated within the MATLAB environment, and the fluxes and currents were shown without and with the controller, the results showed that the method used reduced the effect of the inrush currents with time differences of the order of milliseconds.