It is a protective equipment that usually used in hermetic transformers.It is used in standard demands at 630 kVA and above, but it can also be used for all internal type transformers in the direction of customer demand. It is mounted at the top of the transformer. It measures and controls 4 parameters in the tank;

• Transformer upper oil temperature
• Pressure that generated in the transformer
• Oil level
• The amount of gas that can be generated by faults and discharges
  

Buchholz relay is a type of oil and gas actuated protection relay universally used on all oil immersed transformers having rating more than 500 kVA. Buchholz relay is not provided in relays having rating below 500 kVA from the point of view of economic considerations.

Buchholz relay is used for the protection of transformers from the faults occurring inside the transformer. Short circuit faults such as inter turn faults, incipient winding faults, and core faults may occur due to the impulse breakdown of the insulating oil or simply the transformer oil. Buchholz relay will sense such faults and closes the alarm circuit.

Thermometer

It is a protective device that usually mounted on the cover for measuring and controlling the upper oil temperature of the transformer. On the thermometer there is a resettable maxigraf that continuously displays the maximum temperature. It can be used with or without contact. Contact thermometers have 1 or 2 adjustable contacts (as a warning and trip).

Pressure Relief Valve

It is generally used in hermetic transformers. It detects sudden or wide-time pressure increases that may occur due to oil temperature expansion or failure in the transformer, evacuates the pressure. It can be used with or without contact. Contacted Pressure relief valves have 1 or 2 adjustable contacts (as warning and trip).

Oil Level Indicator

Air Dryer

It is generally used in conservator type transformer. It throws out the air that expands and shrinks with temperature changes in the transformer oil and gets back the air again. With the silica gel dehumidifier it keeps on a large part of the humidity of the passing air. Thus reducing the possibility of moisture in the insulation oil. Silica gel must be changed when the color is turned white. It is mounted at the uppermost point of the expansion tank which is not in contact with oil.

Alcohol Thermometer

In Alcoholic Thermometer it is only used to monitor the temperature of transformer oil and it is without contact.

WHEEL

By mounting the transformer in the lower transport case, the transport of the heavy goods is facilitated. Transformer wheels can move in only 4 directions with 90 degrees difference. A transformer is fitted with 4 wheels.