This is just a preliminary study of power transformer and it's external parts

Power transformer,as it's name sounds is used for power transformation, that is either to step up or to step down power with the help of electric circuit inside the transformer.Therefore it can be defined as an electrical device that transforms electrical energy between two or more circuits through electromagnetic induction.
A change in current in one coil of a transformer produces a varying magnetic field, which in turn induces a varying electromotive force in the neighboring or close coil. Power can be transferred between the two coils through the magnetic field, without a metallic connection between the two circuits.

Below are some of the external parts of power transformer

Conservator tank

A conservator tank is a cylindrical tank mounted on supporting structure on the roof of the transformer main tank. The main function of conservator tank on the transformer is to provide adequate space for expansion of oil inside the transformer.

Function of Conservator Tank in a Transformer

Conservator tank comes into play when there is high temperature inside the transformer caused by a very high voltage input in the transformer, this increased temperature causes the volume of oil inside the transformer to rise,due to the rise, the oil tends to escape and it can do that through the conservator tank where it will be stored,then when the temperature decreases the oil then flows back into transformer.Therefore it acts as a reservoir for transformer insulating oil and also as a protective device.

Buchholz Relay

This is a safety device mounted on power transformers, The Buchholz relay is used as a protective device sensitive to the effects of dielectric failure inside a transformer. This failure might be due to continuity between the two coils caused by dielectric failure(i.e decrease in resistance or insulating effect) in the oil or sudden increase in voltage which then causes the production of fumes or gas inside the transformer.

How it operates or works

How Buchholz Relay works depends on it's design,but it is connected between the transformer tank and the conservator tank.When dielectric failure occurs it causes oil burn inside the transformer, which then produces fumes or gas,so when this happens it moves directly to the relay and it keeps on accumulating inside the relay,at a point the gas will pull a contact bar which then completes a circuit,when this happens a signal will be sent to the relay control unit for immediate action to be taken to ensure safety,but if no action is taken,it will move to the second stage in which the gas will continue to rise,at a point it will make another contact and the signal will be to automatically switch off the circuit breaker in other not to allow the transformer to be damaged.
So when this happens the accumulated gas can be removed by a process known as Bleeding.

Bleeding is the manual removal of the accumulated gas in the relay by hand pressing a button inside it,till oil starts coming out to replace the gas.

Bushing

In electric power system, a bushing is an insulating device that allows an electrical conductor to pass safely through a grounded conducting barrier such as the case of a transformer or circuit breaker.That is the transformer metallic body is discontinued from continuity from the high voltage entering the transformer thus making it possible to work or go close to the transformer or even enter the switch yard without been shocked.

Transformer cooling system

Transformer cooling system are made up of the following:

ONAN : Oil Natural, Air Natural.

ONAF: Oil Natural, Air Forced.

OFAF : Oil Natural, Air Force.

Transformer Cooling Fan

This is classified under ONAF because natural oil is inside the transformer but the air is been forced into the transformer by the action of the blowing fan.

How it works

Cooling Fan works based on how it is been programmed by the transformer manufacturer.It is been put in place to checkmate temperature level of the transformer,for instance a transformer will be designed to work under 50 degree celcius, once the temperature rises above that, two fans will start up to cool the temperature,but if the temperature persist more fans will be turned on,till the transformer cools down to normal.

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Reference :
wikipedia
krenzvent
owlcation
electrical4u

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