Oil immersed transformers are mainly composed of iron cores, windings, oil tanks, voltage regulating devices, radiators, oil pillows, gas relays, insulation sleeves, explosion-proof tubes, and other parts.

1. Iron core

The iron core is composed of stacked silicon steel sheets with good magnetic conductivity, forming a magnetic flux closed circuit. The primary and secondary windings of the transformer are wound around the iron core.

Transformer iron cores are divided into two types of structures: core and shell. Currently, the widely used transformers are all core structures. The heart type iron core is composed of a south iron core column and an iron yoke. The iron core of an oil immersed transformer has an oil passage for cooling the iron core, which facilitates the circulation of transformer oil and also enhances the heat dissipation effect of the equipment.

2. Winding

Winding, also known as coil, is the conductive circuit of a transformer, which is made of copper or aluminum wire wound into multiple layers of cylindrical shape. 1、 The secondary winding is concentric around the iron core column, and for insulation purposes, the low-voltage winding is usually placed inside and the high-voltage winding is placed outside. The insulation material is wrapped around the outside of the wire to ensure insulation between the wires and between the wires and the ground.

3. Fuel tank

The oil tank is the outer shell of an oil immersed transformer, which serves not only to hold oil but also to install other components.  [2]

4. Pressure regulating device

The voltage regulating device is set up to ensure the stability of the secondary voltage of the transformer. When the power supply voltage changes, use a voltage regulating device to adjust the transformer tap changer to ensure stable output voltage on the secondary side. Pressure regulating devices are divided into two types: on load regulating devices and no-load regulating devices.

5. Heat sink

The radiator is installed on the wall of the oil tank, and the upper and lower parts are connected to the oil tank through pipelines. When there is a temperature difference between the upper and lower oil temperatures of the transformer, convection of oil is formed through the radiator, and after being cooled by the radiator, it flows back to the oil tank, playing a role in reducing the temperature of the transformer oil. To improve the cooling effect, measures such as self cooling, forced air cooling, and forced water cooling can be adopted.

6. Oil pillow

Oil pillow, also known as oil tank. Transformer oil will experience thermal expansion and contraction due to temperature changes, and the oil level will also rise or fall with temperature changes. The function of the oil pillow is to provide a buffer for the thermal expansion and contraction of the oil, keeping the fuel tank always full of oil; At the same time, with the oil pillow, the contact area between oil and air is reduced, which can slow down the oxidation of oil.

7. Gas relay

Gas relay, also known as gas relay, is the main protective device for internal faults in transformers. It is installed in the middle of the connecting oil pipe between the oil tank and the oil pillow. When a serious fault occurs inside the transformer, the gas relay connects to the circuit breaker and trips in the same way; When a minor fault occurs inside the transformer, the gas relay connects the fault signal circuit.

8. Insulation sleeve

The high and low insulation sleeves are located on the top cover of the transformer oil tank. Oil immersed transformers generally use porcelain insulation sleeves. The function of the insulation sleeve is to maintain good insulation between the high and low voltage winding leads and the oil tank, and to fix the leads.

9. Explosion proof pipe

Explosion proof tube, also known as safety airway, is installed on the oil tank of the transformer, and its outlet is sealed with glass explosion-proof film. When a serious fault occurs inside the transformer and the gas relay fails, the gas inside the oil tank breaks through the glass explosion-proof film and sprays out from the safety airway to prevent the transformer from exploding.