<P> In the field of electric power distribution and transmission, a Buchholz relay is a safety device mounted on some oil - filled power transformers and reactors, equipped with an external overhead oil reservoir called a "conservator". The Buchholz relay is used as a protective device sensitive to the effects of dielectric failure inside the equipment . A generic designation for this type of device is "gas detector relay". </P> <P> Buchholz relays have been applied on oil - filled power and distribution transformers at least since the 1940s . The relay is connected to the oil piping between the conservator and oil tank of a transformer . The piping between the main tank and conservator is arranged so that any gas evolved in the main tank tends to flow upward toward the conservator and gas detector relay . </P>

What is buchholz relay what is it used for