Oil-immersed transformers are widely used in industrial and mining enterprises, agriculture, water conservancy, residential communities and other fields due to their small size, light weight, high efficiency, adjustable voltage, and reliable operation. According to the characteristics of oil-immersed transformers, its protection devices are mainly divided into three categories: safety protection devices, oil protection devices, and oil temperature measurement devices. Let's start with the relevant definitions of safety protection devices.

The safety protection devices of oil-immersed transformers can be divided into gas relays, pressure relief valves and valves, valves, and vent plugs.

1.Gas relay. Used for oil-immersed transformers of 800kVA and above. When the gas relay contact capacity exceeds 66VA or exceeds 15W, and the gas accumulation volume is 250~300ml or within the range set in the oil speed, the corresponding contact should be connected. The structure and installation position of the gas relay should be able to observe the amount and color of the gas, and it should be easy to take the gas. Install it with a union oil 1.5% elevated slope. The oil tank cover of the 220kV transformer should also have a rising slope of 1~1.5%.

2.Pressure relief valve. It is suitable for transformers of 800kVA and above. When the pressure in the oil tank in the safety air passage or pressure relief valve reaches 5.07×104Pa, it should be released reliably. For transformers of 120000kVA and above, two pressure relief valves should be installed.

3.Valves, valves, vent plugs. An oil sample valve should be installed at the lower part of the oil tank wall of all transformers, and an oil sample valve should be installed in the middle part of the oil tank wall of 110kV, 90000kVA and 220kV, 63000kVA and above. The bottom of the oil tank of 315kVA and above shall be equipped with an oil discharge device. There should be a large enough oil drain valve at the lower part of the transformer oil tank, and the 220kV transformer should also have an emergency oil drain valve. The transformer must release gas during oil filling and testing, so there are vent plugs on the upper part of the transformer riser, radiator, bushing, etc. to ensure the safety of the transformer.