Transformer Load-Tap Changers: State-of-Art and Trends

Load tap changes (LTC) are a major component of many transformers. They are used to change the voltage of secondary/primary side of a transformer to compensate for voltage variations in the power systems manly caused by variable loading. The paper describes the various types of load tap changers, expecially on-load ones, and various tapping winding configurations. Besides the conventional (electro-mechanical) tap changers, the using of the power-electronic tap for mitigation of short term voltage problems, lasting for several sysles, are discussed too.