ABSTRACT
The tap changer changes the ratio of a transformer by adding turns to or subtracting turns from either the primary or the secondary winding. The execution of a tap-change operation with a tap changer can be done with the transformer de-energized, when tap-changing is required rare, or it can be done with the transformer energized that means on-load. For many decades, power transformers equipped with tap changers have been the main components of electrical networks and industry. De-energized tap-changing is mainly used when the variation in the nominal operating voltage which requires a tap changer operation is not expected frequently. The load tap changer (LTC) design that is normally applied to larger powers and higher voltages comprises a diverter switch (arcing switch) and a tap selector. Since the early 1970s, vacuum interrupters that fulfilled the characteristics required by reactor-type LTCs have been developed. A completely new subclause was created in the segment of intelligent controls for LTCs.
