1. Protection principle:
The pressure release valve is a device used to protect oil-immersed electrical equipment, that is, when a fault occurs inside the transformer oil tank, the oil in the oil tank is decomposed and vaporized, a large amount of gas is generated, and the pressure in the oil tank rises sharply. If the pressure is not released in time , which will cause the transformer tank to deform or even burst.
The installation of the pressure relief valve can make the transformer fail in the oil tank, and when the pressure rises to the opening pressure of the pressure relief valve, the pressure relief valve opens rapidly within 2ms, so that the pressure in the transformer oil tank is quickly reduced. When the pressure drops to the closing pressure value, the pressure relief valve will be closed reliably, keeping the positive pressure in the transformer tank forever, effectively preventing the outside air, moisture and other impurities from entering the tank, and has the advantages of no component damage after action, no need to replace, etc. , has been widely used.
2. Setting principles and operating requirements:
Since most transformer manufacturers stipulate that the contact of the pressure relief valve acts on the trip, there have been many trips and power outages caused by the reduction of the secondary circuit insulation of the pressure relief valve. For this reason, the transformer operation regulations (DL/T 572-95) stipulate that "the contact of the pressure relief valve should act on the signal". However, when the pressure relief valve is activated and the transformer does not trip, it may cause the transformer to run out of oil and cause the failure to expand. To this end, a Buchholz relay can be used to protect the transformer: when the pressure release valve acts and the oil level is too low, the lower float of the Buchholz relay sinks and conducts, sending a trip signal.
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