What are the cooling methods for power transformers?

The cooling method of power transformers is one of the key factors to ensure their safe and stable operation. Transformers generate a lot of heat during operation. Reasonable cooling methods can not only increase their service life, but also ensure their efficient operation. The following are the main cooling methods for transformers:

1. Air cooling

a. Natural air cooling (AN)

Natural air cooling is a cooling method in which air flows naturally. The transformer dissipates heat into the environment by contacting the air and using natural convection. This method is suitable for large power transformers or transformers under low load conditions, because the cooling effect of natural air cooling is limited and is suitable for situations where the heat dissipation demand is not high.

b. Forced air cooling (AF)

Forced air cooling is to increase air flow and improve cooling efficiency by installing mechanical equipment such as fans. This method is usually used for small and medium-sized transformers, which can improve cooling effects in a smaller volume. However, the air cooling system may be affected by dust and environmental pollution and requires regular maintenance.

2.Oil cooling

a. Natural oil cooling (ON)

Natural oil cooling is to cool the insulating oil inside the transformer, and the oil flows naturally inside the transformer to take away heat. The transformer casing and oil tank structure are designed to ensure oil circulation and heat dissipation. This method is suitable for small and transformers and is common in substations and distribution systems.

b. Forced oil cooling (ONAN)

Forced oil cooling is based on natural oil cooling, with the addition of an oil pump system to make the oil flow more powerful, thereby improving the cooling effect. This method is suitable for transformers with heavy loads and can maintain the normal temperature of the transformer under high load conditions.

c. Oil-immersed air cooling (ONAF)

Oil-immersed air cooling combines oil cooling and air cooling. The insulating oil inside the transformer transfers heat to the transformer cooler through natural circulation or pumping, and the cooler dissipates the heat into the air through a fan. This method is suitable for transformers that require additional cooling capacity and can effectively cope with high load conditions.

3.Water cooling

a. Natural water cooling (ONWF)

Natural water cooling uses water as a cooling medium, and the water removes heat through natural circulation. This method is generally used for transformers, especially when a large amount of heat needs to be handled. The design of the water cooling system needs to consider the water source, the maintenance of the cooling equipment, and potential leakage problems.

b. Forced water cooling (ONWAF)

Forced water cooling adds a water pump system to natural water cooling to improve cooling efficiency. This method is suitable for large power generation transformers and transformers with extremely high loads, and can provide stable cooling effects. However, this system has high requirements for water sources and equipment maintenance.

4.Combined cooling

a. Oil-water mixed cooling

This method combines the advantages of oil cooling and water cooling, and improves cooling efficiency by combining the transformer's insulating oil and water cooling system. Oil-water mixed cooling is usually used for high-load, transformers, and can effectively meet the heat dissipation requirements under extreme working conditions.

b. Oil-gas cooling

Oil-gas cooling is a new cooling method that transfers heat through oil and gas inside the transformer. The gas is usually nitrogen or other non-flammable gases with good thermal conductivity and insulation properties. This method is suitable for high-voltage, high-power transformers and can provide excellent cooling effects.