The power and distribution transformer in India, Rajasthan Powergen has a cooling system to dissipate the heat generated by a transformer. The more easily the heat can be dissipated the better it is for the working of the transformer. Cooling system can increase the load carried by a transformer without heat damage. When the critical limit of the temperature is reached, there are chances of failure of transformer as there is ageing of the transformer’s insulation. Thus the role of cooling system is to increase the capacity of the transformer to carry load without reaching critical hot spot temperature.
Auxiliary fans are the most common type of transformer cooling equipments. These fans keep the radiator tube cool leading to increased ratings of a transformer.
Maintenance of Cooling Systems
* Dry-Type Transformers: For the installation of dry-type transformers, ventilation is of paramount importance. Also the radiator vents of the transformer should be free of obstructions to aid heat dissipation.
* Forced Air: If forced air from a fan is used to control the temperature of a transformer, the motors of the fans should be checked at regular intervals for lubrication.
* Water cooled systems: Transformer systems using water for cooling should be checked periodically to make sure that there is no leakage. Leaks can be checked by raising the pressure within the cooling system. Other equipments related to a water-cooled system like the alarm system, water pump and pressure gauges can also be checked. Make sure to check the water source to ensure it has sufficient flow and pressure.
*Liquid coolants: When oil is used as a coolant, the dielectric strength of the oil should always be checked before putting the transformer is put into use.
Types of Cooling Systems
For oil immersed transformers, the types of cooling systems are:
* Oil Immersed Natural Cooled (ONAN): In this type the core and the windings both are kept immersed in oil. The transformer is cooled by the natural circulation of this oil.
** Oil Immersed Air Blast (ONAF): Air is circulated in this cooling system and fans are used for cooling the transformer.
* Oil Immersed Water Cooled (ONWN): An internal coil is used and water flows through it for cooling. But it is not used commonly now a days.
* Forced Oil Air Blast Cooled (OFAF): In this case, cooling is accomplished in two ways. Oil circulation is facilitated by a pump, and fans are added to the radiators to provide blasts of air.
* Forced Oil Natural Air Cooled (OFAN): For this type of cooling, a pump is included within the oil circuit to aid in oil circulation.
*Forced Oil Water Cooled (OFWF): In this a pump within the oil circuit forces the oil to circulate out through a separate heat exchanger in which water flows.
Oil-immersed naturally cooled (ONAN) is the most reliable type of cooling system, it also produces minimal noise.
Top furnace transformer manufacturer in India, Rajasthan Powergen make use of the forced cooling system for years. Using cooling system can enhance the transformer’s thermal performance and it also leads to increased shelf life of the transformer by dissipation of heat.
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