Oil Immersed Transformer

Core – The core forms the fundamental structure of an oil-immersed power transformer. It serves as a low-reluctance path for magnetic flux and provides mechanical support for both the primary and secondary winding systems. Constructed from high-grade, grain-oriented electrical steel, the core is built by stacking thin laminations. These laminations are insulated from one another to minimize eddy current losses.

Winding – An oil-immersed power transformer contains two separate windings: the primary and the secondary. Each winding performs a distinct function in the energy transfer process. The conductors are typically made from either copper or aluminum. Copper windings are formed from multiple turns of wire, while aluminum is used to create conductive strips or coils. The windings are meticulously insulated from each other and from the transformer’s core.

Winding configurations vary depending on the transformer’s specific design parameters, including its current rating, permissible temperature rise, and short-circuit withstand capability. The windings are categorized as High Voltage (HV) and Low Voltage (LV), based on their respective operating voltage levels.

Insulation – Insulation is a critically important component in any oil-immersed power transformer, as insulation failure can lead to severe damage. Since transformers operate with high currents that generate significant heat, maintaining perfect insulation between the windings and between the windings and the core is essential for safe and reliable operation.

Tank – The tank is a major structural component that houses and protects the transformer’s active parts. It shields the core and windings from the external environment and also acts as a sealed reservoir for the insulating oil. Furthermore, the tank serves as a mounting base for various transformer accessories.

Transformer Oil – This specialized oil is vital for the insulation and cooling of oil-immersed power transformers. It enhances the insulation between live conducting parts, such as the windings and core, and efficiently dissipates the heat they generate. Transformer oil also serves as a diagnostic medium, as its analysis can help detect incipient internal faults.

Typically, transformer oil is a highly refined mineral oil. It is composed of hydrocarbons like paraffins, naphthalenes, and olefins. With a high flash point of approximately 310°C, it is exceptionally well-suited for its insulating and cooling roles.

Oil Conservator – Mounted on top of the main tank and connected via pipes, the oil conservator is a cylindrical tank that accommodates the expansion and contraction of the transformer oil with changes in temperature. An oil level indicator is attached to the conservator to provide a clear visual indication of the oil volume inside the transformer.

Terminals and Bushings – The terminals are the external connection points for the incoming and outgoing electrical cables. They are connected to the ends of the internal windings. Each terminal is equipped with a bushing, which acts as an insulator, preventing the high-voltage terminal from making electrical contact with the grounded transformer tank. The bushing also contains the electrical field and manages heat.