When the pressure reducing valve acts, it will jack up the indicator rod. When the pressure relief valve is closed, the indicator rod will not fall due to friction. When the patrol personnel patrol, they can immediately find that the pressure relief valve has acted between the two patrols.
When the transformer leaves the factory, in order to avoid the misoperation of the pressure relief valve, the indicator rod will be closed with a baffle to prevent it from rising. After installation on site, the baffle needs to be removed.
Large and medium-sized transformers use pressure relief valves instead of explosion-proof tubes, which are generally installed at the bottom of transformer oil tanks. When the transformer works normally, the pressure relief valve protects the transformer oil from outside air. Once the transformer is short-circuited, the arc and spark will be generated in the transformer winding, which will make the transformer oil produce a lot of gas instantly and increase the pressure in the oil tank. When the pressure reaches 5.4× 104Pa, the pressure relief valve is opened to relieve the pressure within 2ms; When the pressure value is 2.9× 104Pa, the pressure relief valve will automatically close. So that the transformer oil tank will not deform and explode due to excessive pressure.