Oil immersed transformer oil system

(1) The oil system in the main body. The oil system that communicates with the oil around the windings is the main body system, including the oil in the cooler or radiator, the oil in the oil conservator, and the oil in the oil-filled casing of 35kV and below.

The gas vents stored in this oil system must be discharged during oil filling. In general, the above components should have their own bleed plugs. The oil in the main body mainly acts as insulation and cooling. Oil can also increase the electrical strength of insulating paper or insulating paperboard. When vacuuming, if some parts can not withstand the same vacuum strength as the main tank can withstand, apply temporary sluice isolation, such as the gate valve between the oil conservator and the main tank. The submersible pump head on the cooler should be sufficient to avoid inhaling air due to negative pressure. This oil system should have a protection system for the pressure relief device to eliminate the pressure generated when the body is faulty.

(2) The on-load tap-changer switches the oil in the switch chamber. This part of the oil has its own protection system, namely flow relay, oil storage tank, pressure relief valve. The oil in this switch chamber acts to insulate and extinguish the current. The oil will be in the oil produced when the diverter switch cuts off the load current. This oil system should have good sealing performance, and the sealing performance should be protected even if the arc pressure is generated during the switching process.

Although the oil in the switch of the on-load tap-changer is isolated from the oil in the main body, in order to avoid damage to the seal of the diverter switch chamber during vacuum injection, the oil should be vacuumed simultaneously with the oil in the main body. The system has the same degree of vacuum and, if necessary, the oil conservator of this system should be isolated during vacuuming. For structural convenience, the oil storage of the main body and the oil conservator of the switch house are designed to be isolated from each other.

(3) Fully sealed at voltage levels of 60kV and above. This oil system primarily acts as an insulator or increases the electrical strength of the insulating paper in the oil-capacitive casing. When filling the body, the end of the casing should be sealed to avoid air intake.

(4) Oil in the high-voltage outlet box or oil in the outlet box. The high-voltage outlet of the three-phase 500kV transformer is passed through a corrugated insulation isolation oil system. This oil system is mainly used for insulation.

To simplify the structure, this oil system can also be connected to the oil system in the main body through a connecting pipe or designed as a separate oil system.

(5) When performing various insulation tests on oil-immersed transformers, first deflate and release the gas that may be stored through the bleeder plug. The potential gas failure can be predicted by analyzing the gas chromatographic analysis of the oil in each system. Each oil system must meet the requirements of operation, such as the change of oil volume when absorbing oil expansion and contraction, the valve for draining oil, the venting plug, the isolation valve of the cooler and radiator and the main tank. Each oil system has good sealing performance. The oil in the switch of the on-load tap-changer should be able to be replaced separately without releasing the oil in the main body. When transporting, the oil in the main body can be discharged and filled with dry nitrogen.

Oils with different oil bases cannot be mixed even with the same oil system.

Each oil system should pay attention to the oil characteristics at negative temperature. For example, when the oil in the main body is at a negative temperature, the viscosity of the oil is large, the fluidity is poor, and the heat dissipation is poor. When the on-load tap-changer switches the indoor oil at a negative temperature, it will affect the lengthening of the switching process and increase the temperature rise of the transition resistance.

For the oil system of the main body of the ultra-high pressure Oil Immersed Distribution Transformer, attention should also be paid to the phenomenon of oil flow charging, and it is necessary to prevent the oil flow from being electrified to the oil flow discharge phenomenon. It is necessary to control the resistivity of the oil, the speed of each part of the oil, and the space for releasing the charge in the oil.