3-Ф Transformer construction- Outside

Outside Construction:-

Nameplate Ratings:-

Normally nameplate rating indicates some necessary information of the Tx like manufacturer name, HT-LT ratio, voltage ratings; tap changing ratings, weights, vector group, frequency, serial no. etc.

Bushing-
A bushing is a component that insulates a high voltage conductor passing through a metal enclosure. In Tx bushing used for both High Voltage (HV) and low voltage (LV) side. HV side bushing is called HV Bushing and LV side bushing is called LV Bushing. HV bushing is greater size than LV Bushing. Normally in distribution Tx HT side has 3 bushing and at the LT side there are 4 bushing.

Radiator-
Radiator is used for cooling the Tx. Transformers can be hotter by any cause, like over load, over current, unbalanced load, temperature etc. Radiator helps to keep cool the Tx and keep safe from damage.

Lightning Arrestor-
Lightning arrestor is used to protect the Tx from lightning. If lightning occur in the line, this very high voltage surge can bypass through this arrestor and normal voltage pass through the line. Two pin with a small distance is used for this purpose.

Tap changer-
A tap changer is a device used in transformers for regulation of the voltage to required levels. This is normally achieved by changing the ratios of the transformers on the system by altering the number of turns in one winding of the appropriate transformer. This tap changer used in HV side. There are 5 taps to maintain the voltage between certain limits. Each taps has certain percents of impacts on LT side. Tap change is done in off condition.
Conservator Tank-
Conservator tank is an oil tank above the transformer filled with Tx oil. The oil helps cool the transformer & it also provides part of the electrical insulation between internal live parts. Tx oil has certain dielectric constant. This tank have also oil level indicator. In some cases there is safety valve instead of a conservator tank just to release the gas if the oil gets too hot for any kind of short circuit fault. Conservator tank is not fully filled up with oil and some part of it is left empty.

Buchholz relay-
Buchholz relay stay In the middle of the connecting pipe of conservator tank and the Tx. It monitors the oil level, gas forming etc. This is slow in operation.

Breather-
Conservator tank is not fully filled up with oil and some part of it is left empty. When the oil expands because of heat then the empty part is filled with oil. The oil becomes cooler when Transformer is not at full load. Then the breather made of silica gel sucks in moister less air from outside to fill up the empty space inside the tank. So, within the breather air can come through it to maintain pressure inside the tank. But it protects moisture to come in conservator tank. Moisture can reduce the dielectric constant of the oil. In normal condition silica gel is blue coloured. But when it becomes white color that means it needs to be changed.