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Types of cooling system for transformer

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hussien 3 sba7a

on 23 February 2015

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Transcript of Types of cooling system for transformer

The main source of heat generation in transformer is its copper loss or I^2*R loss. Although there are other factors contribute heat in transformer such as hysteresis & eddy current losses.

If this heat is not dissipated properly, the temperature of the transformer will rise continually which may cause damages in paper insulation and liquid insulation medium of transformer.

In electrical power transformer we use external transformer cooling system to accelerate the dissipation rate of heat of transformer.

Different Transformer Cooling Methods:
There are three main types of cooling system depending upon their size and ratings:

1. -Oil cooling.
2. -Air cooling.
3. -Natural gas cooling.
Oil cooling
1-ONAN Cooling of Transformer:

The full form of ONAN is "Oil Natural Air Natural"Flow of hot oil is utilized for cooling.The hot oil flows to the upper portion of the transformer tank and the vacant place is occupied by cold oil.
This hot oil which comes to upper side, will dissipate heat in the atmosphere by natural conduction &radiation in air.

Dissipation of heat in air depends upon dissipating surface of the oil tank, it is essential to increase the surface area of the tank. So additional dissipating surface in the form of tubes or radiators connected to the transformer tank.

2-ONAF Cooling of Transformer:

The full form of ONAF is "Oil Natural Air Forced".Heat dissipation can obviously be increased, if dissipating surface is increased but it can be make further faster by applying forced air flow on that dissipating surface. Fans blowing air on cooling surface is employed.

As the heat dissipation rate is faster and more in ONAF transformer cooling method than ONAN cooling system.

3-OFAF Cooling of Transformer:

OFAF means "Oil Forced Air Forced" .In oil forced air natural cooling system of transformer, the heat dissipation is accelerated by using forced air on the dissipating surface.The heat dissipation rate can be still increased further if this oil circulation is accelerated by applying some force.The oil is forced to circulate within the closed loop of transformer tank by means of oil pumps.

The main advantage of this system is that it is compact system and for same cooling capacity OFAF occupies much less space than farmer two systems of transformer cooling.

4-OFWF Cooling of Transformer:
"Oil Forced Water Forced" water may be used as better heat exchanger media than air.
The hot oil is sent to water heat exchanger by means of oil pump and there the oil is cooled by applying sowers of cold water on the heat exchanger’s oil pipes.There are two types of forced directed oil cooling:

I. ODAF Cooling of Transformer :
"oil directed air forced" Here forced circulation of oil directed to flow through
predetermined paths in transformer winding.ODAF is generally used in very high rating transformer.

II. ODWF Cooling of Transformer :
"oil directed water forced" is just like ODAF only
difference is that here the hot oil is cooled in
cooler by means of forced water instead of air.

Air cooling
Cooling methods for dry Transformers: "Air Cooling systems” Dry transformers are huge transformer which are used in stepping down from a high voltage to an extreme low voltage.
1-Air Natural or Self Air Cooled Transformer:

This method of transformer cooling
is generally used in transformers
(up to 3 MVA).
In this method the transformer is
allowed to cool by natural air flow
surrounding it.
Air is directed by huge fans.
Natural gas cooling system
In specific transformers natural gases in such low pressure is used in cooling system...natural gases have emerged as a safer and more environmentally friendly replacement than oil.

The natural gases used:
Helium, sulfur hexafluoride (SF6) ...etc.
The only disadvantage for using natural gases is that
if any leakage happened it’s not easy to note...

The cooling system for such a transformer depends first upon their size and rating
There are a lot of types for cooling systems but there are 3 main types’ oil, air and natural gases cooling systems and each type has categories and internal types and each have advantages.

Types of cooling system for transformer
Presented by:

Names: ID:
1-Rana Badr Eldin Mohamed 1123130
2-Islam Fouad Abd Elhameed 1122162

2-Air Blast:

For transformers rated more than 3 MVA, cooling by natural air method is inadequate.
In this method, air is forced on the core and windings with the help of fans or blowers. The air supply must be filtered to prevent the accumulation of dust particles in ventilation ducts. This method can be used for transformers up to 15 MVA.

These fans draw cooling air up through the tube bundle to provide a more efficient distribution of airflow.
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