Importance and Types of Transformer Cooling Systems

May, 19 - 2009   

The load that a transformer carries without heat damage can be increased by using an adequate cooling system. This is due to the fact that a transformer's loading capacity is partly decided by its ability to dissipate heat. If the winding hot spot temperature reaches critical levels, the excess heat can cause the transformer to fail prematurely by accelerating the aging process of the transformer's insulation. A cooling system increases the load capacity of a transformer by improving its ability to dissipate the heat generated by electric current. In other words, good cooling systems allow a transformer to carry more of a load than it otherwise could without reaching critical hot spot temperatures.

One of the more common types of transformer cooling equipment is auxiliary fans. These can be used to keep the radiator tubes cool, thereby increasing the transformer's ratings. Fans should not be used constantly, but rather only when temperatures are such that extra cooling is needed. Automatic controls can be set up so that fans are turned on when the transformer's oil or winding temperature grows too high.

Maintenance of Cooling Systems

 

• Dry-Type Transformers:For dry-type transformers, the area in which the transformer is to be installed should have proper ventilation. This ventilation should be checked prior to installation to make sure it is adequate. Additionally, the transformer's radiator vents should be kept clear of obstructions that could impede heat dissipation.

   

   

• Forced Air: If the transformer's temperature is being kept at acceptable levels by forced air from a fan, the fan's motors should be checked periodically to make sure they are properly lubricated and operate well. The thermostat that ensures the motors are activated within the preset temperature ranges should be tested as well.

   

• Water cooled systems: Systems that are cooled by water should be tested periodically to make sure they operate properly and do not leak. Leaks can be checked by raising the pressure within the cooling system, which can be done in various ways. If the cooling coils can be removed from the transformer, internal pressure can be applied by adding water. Otherwise, pressure checks can also be made using air or coolant oil, if the coils need to be checked within the transformer itself.

  If the cooling coils are taken out of the transformer, the water cooling system as a whole can be tested. Here, the coils are filled up with water until the pressure reaches 80 to 100 psi, and left under that pressure for at least an hour.  Any drop in pressure could be a sign of a leak. The other equipment linked to a water-cooled system can be tested at the same time, such as the alarm system, water pump and pressure gauges. Also, the water source should be tested to make sure it has sufficient flow and pressure.

   

• Liquid coolants: When oil coolants are prepared they are dehydrated, and processed to be free of acids, alkalis, and sulfur. They should also have a low viscosity if they are to circulate easily. If a transformer is cooled by oil, the dielectric strength of the oil should always be tested before the transformer is put into service.

   

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