Transformer Temperature Rise?

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Is temperature rise important for transformers? The answer is of course, especially for power transformer manufacturers. Take a 500kva transformer as an example. The temperature rise's influence is not only in the 500kva transformer price, but also have a decisive impact on the performance of the transformer.

Next, I will introduce the cooling method of oil-immersed transformers.

According to Article 3.2 of the standard GB 1094.2-1996 "Power Transformer Part 2: Temperature Rise", the cooling method of oil-immersed transformers is indicated by a four-letter sequence.

The first letter indicates the internal cooling medium in contact with the winding:

O - mineral oil or synthetic insulating liquid with a flash point not greater than 300 degrees Celsius.

The second letter indicates the circulation method of the internal cooling medium:

N - the oil flow through the cooling device and the winding is a natural thermal convection circulation.
F - the oil flow in the cooling device is a forced circulation, and the oil flow through the winding is a thermal convection circulation.
D - The oil flow in the cooling device is a forced circulation, and the oil flow inside the main winding (at least) is a forced guided circulation.

The third letter indicates the external cooling medium:

A - air.
W - water.

The fourth letter indicates the circulation method of the external cooling medium: N - natural convection. F - forced circulation (fan, pump, etc.)

Common cooling methods include: ONAN - natural circulation of transformer oil inside the transformer, natural heat convection circulation of air in the cooling equipment.
ONAF - natural circulation of transformer oil inside the transformer, forced circulation of air in the cooling equipment.
OFAF - forced circulation of transformer oil inside the transformer, forced circulation of air in the cooling equipment.
OFWF - forced circulation of transformer oil inside the transformer, forced circulation of water in the cooling equipment.
ODAF - forced guided circulation of oil flow in the main winding, forced circulation of air in the cooling equipment.