The explosion-proof tube (pressure relief device) of transformer is installed on the top cover of transformer. When the temperature of transformer rises and the oil decomposes violently, a large amount of gas is produced. When the pressure in the tank rises sharply to a certain value (about 0.5 MPa), the explosion-proof film of the explosion-proof tube breaks (the pressure relief device opens), and the oil and gas in the tank are ejected to release the pressure and prevent the tank from changing. Shape or explosion.

There is also a connecting pipe between the explosion-proof pipe and the oil pillow (oil storage tank), so that the pressure and oil level are the same at both places, so as to avoid the misoperation of gas relay caused by the change of oil level. The action value of the voltage relief device can be adjusted according to the regulations. After the action, the voltage relief device can also send signals or act on each side of the transformer tripping.