Current limiting ability and overvoltage analysis of variable impedance transformer

With the expansion of the grid scale, short-circuit current is increasing, the safety of grid is seriously impacted by the short-circuit current. Therefore, a new technique of energy-saving transformer possessing variable impedance is proposed. This transformer combines the advantages of the high impedance transformer and fault current limiter, it can reduce the impact of short-circuit current and also take the economy into account. The principle of variable impedance transformer was introduced, PSCAD simulation software was used to analyze the current limiting capacity and the distribution of overvoltage of transformer. Researches indicated that variable impedance transformer could improve the ability to withstand short circuit current impulse through the adjustment of the impedance, short circuit current could be reduced by 40.2%, and the overvoltage could be restrained by novel suppression measure.