Oil System Of Oil Immersed Transformer

Oil immersed transformers have several independent oil systems that are isolated from each other. During the operation of oil immersed transformers, the oil in these independent oil systems is not interconnected, and the oil quality and operating conditions are also different. Gas chromatography analysis of the oil content should be performed separately to determine the presence of potential faults.
(1) Internal oil system of the main body. The oil system that communicates with the oil around the winding is the main internal system, including the oil in the cooler or radiator, the oil in the oil storage tank, and the oil in the 35kV and below oil filled bushing.
When injecting oil, the gas vent plug stored in the oil system must be released. Generally speaking, the above components should have their own vent plugs. The oil inside the main body mainly serves as insulation and cooling. Oil can also add insulation paper or
The electrical strength of insulating cardboard. When vacuum oiling, if some components cannot withstand the same vacuum strength as the main oil tank, temporary gates should be used for isolation, such as the gate valve between the oil storage tank and the main oil tank. The head of the submersible oil pump on the cooler should be sufficient to prevent air from being sucked in due to negative pressure. This oil system needs a protection system with a pressure relief device to eliminate the pressure generated when there is a malfunction in the body.
(2) Oil inside the switch room of the on load tap changer. This part of the oil has its own protection system, which includes flow relays, oil storage tanks, and pressure relief valves. The oil in this switch room serves to insulate and extinguish the current. The oil will go into the oil generated when the switch cuts off the load current. This oil system needs to have good sealing performance, even if arc pressure is generated during the switching process, to protect the sealing performance.
Although the oil inside the on load tap changer switch room is isolated from the oil inside the main body, during vacuum oil injection, in order to avoid damaging the seal of the switch room, it should be injected with oil at the same time as the oil inside the main body. During vacuum oil injection, the two systems should have the same vacuum degree, and if necessary, the oil storage tank of this system should also be isolated during vacuum pumping. For structural convenience, the oil storage of the main body and the oil storage tank of the switch room are designed as an isolated whole.
(3) Fully sealed for voltage levels of 60kV and above. The main function of this oil system is insulation, or to increase the electrical strength of the insulation paper inside the oil capacitor sleeve. When injecting oil into the main body, the wiring terminals at the end of the sleeve should be sealed to prevent air intake.
(4) Oil inside the high-voltage outlet box or oil inside the point gas outlet box. The high-voltage outgoing line of a three-phase 500kV transformer is isolated by a corrugated insulation oil system. This oil system mainly serves as insulation.
To simplify the structure, this oil system can also be connected to the main oil system through a connecting pipe or designed as a separate oil system.
(5) When conducting various insulation tests on oil immersed transformers, the first step is to release the gas, which may have been stored, through the release plug. Potential faults can be predicted by analyzing the gas content in the oil of each system through chromatographic analysis. Every oil system must meet operational requirements, such as absorbing changes in oil volume during expansion and contraction, valves for oil discharge, vent plugs, isolation valves for coolers, radiators, and main oil tanks. Each oil system has good sealing performance, and the oil inside the on load tap changer switch room should be able to be replaced separately without releasing the oil inside the main body. During transportation, the oil inside the main body can be released and filled with dry nitrogen gas.