What are the common specifications? Gas relay (also known as gas relay) is a protective device used in transformers. It is installed in the pipeline between the oil storage tank and the oil tank of the transformer. When the internal fault of the transformer is used to decompose the oil to produce gas or cause oil flow to surge, The contact of the gas relay is activated, the designated control circuit is connected, and a signal alarm (light gas) is issued in time or the protection element is automatically switched off (heavy gas). There are three main types of gas relays on the market, which are distinguished according to their calibers: QJ-25, QJ-50, and QJ-80 users can purchase according to their needs.