On-load tap-changers current experience and future developments. Principles and resulting benefits of separate tank (external) tap-changers

This paper deals with three types of high speed resistor on-load tap-changers designed to be mounted on the side or end of power transformers. These include double compartment tap-changers with separate selector and diverter compartments, single compartment selector tap-changers and in-tank tap-changers with barrier boards. The major advantage of separate tank tap-changers is their easy access for inspection and maintenance, making them particularly suitable for the user to service