Oil Immersed Transformer

Superior Cooling Performance
One of the biggest advantages of oil-immersed transformers is their highly efficient cooling mechanism. The insulating oil absorbs the heat generated by the transformer windings and core, then circulates to dissipate it through radiators or cooling fins. This thermal management system allows the transformer to operate continuously under high load conditions without overheating.

Higher Power Capacity and Voltage Levels
Oil-immersed transformers are designed to handle higher power ratings and voltage levels compared to their dry-type counterparts. This makes them ideal for power grids, transmission networks, and industrial facilities where large amounts of energy must be managed and transferred reliably.

Long Service Life
Thanks to the oil's dual role as both coolant and insulator, oil-immersed transformers tend to have a longer service life—often exceeding 30 years when properly maintained. The oil helps reduce oxidation, protects against insulation aging, and minimizes thermal stress on critical components, ensuring long-term durability and low failure rates.

Excellent Overload Capacity
These transformers can withstand short-term overload conditions due to the thermal mass of the oil, which absorbs excess heat effectively. This overload tolerance is critical in applications where power demand can spike suddenly, such as industrial plants or utility substations.

Cost-Effective for Large-Scale Installations
Although the initial installation of oil-immersed transformers can be complex due to the need for oil containment and cooling systems, they are generally more cost-effective over the long term for high-capacity applications. Their ability to carry more load at lower operational temperatures translates to energy efficiency and fewer replacements.

Generally, the winding of oil-immersed power transformer, relative to the temperature rise of the air around the transformer, has an internal control standard of 65K, which refers to the average temperature rise of the winding, not the highest hot spot temperature rise, and is considered according to the Class A insulation grade (105 degrees). However, it is generally controlled below 65K during transformer design.

China's transformer standard stipulates that the maximum annual average temperature of ambient temperature is 20 ℃, the maximum monthly average temperature is 30 ℃, and the maximum temperature is 40 ℃.

Generally, the winding temperature cannot be detected by the user. However, the oil top temperature can be detected. Therefore, the temperature rise of the top layer of oil is specified in the transformer manufacturer, which is 55K. Of course, it will also be controlled below 55K during design and manufacturing. In this case, the winding temperature rise shall not exceed 65K.

Therefore, the operation department stipulates that the top temperature of transformer oil should not exceed 85 degrees regardless of the ambient temperature. This can ensure that the hottest point temperature of the transformer winding does not exceed 98 ℃. The average temperature of winding shall not exceed 85 ℃. In this case, the service life of the transformer is 20 years. The oil temperature of oil-immersed transformer during operation should take into account that the transformer oil will not deteriorate too quickly. When the transformer oil reaches 85 ℃, the alarm will be given, and when the maximum temperature reaches 95 ℃, the switch of the transformer will be tripped.