CEDASPE ET Buchholz relay detects faults and minimize the propagation of any damage which might occur within oil-filled transformers. Short circuit faults such as inter-turn faults, incipient winding faults and core faults may occur due to overheating, bad connections and ageing.

The Buchholz relay senses such faults and closes the alarm circuit. Its function is based on the fact that an electrical fault inside the transformer tank is accompanied by the generation of gas; if the fault is severe enough, it will be accompanied by an oil surge from the tank to the conservator.