What are the main disadvantages of oil-immersed power transformers?

1. Fire risk

Oil-immersed transformers use oil as an insulating medium, which is the main reason for their fire risk. When faults occur inside the transformer, such as winding short circuits, core overheating, etc., these faults may cause the oil temperature to rise sharply. Once the oil temperature exceeds the flash point of the oil, it may cause a fire. In addition, if the oil level of the transformer is too low or the cooling system fails, it may also cause the oil temperature to rise abnormally, thereby increasing the risk of fire. Therefore, for oil-immersed transformers, effective fire prevention measures must be taken, such as installing a fire alarm system, setting up firewalls and fire extinguishing devices, etc., to ensure their safe operation.

2. Oil leakage

One of the main disadvantages of oil-immersed transformers is the oil leakage. Since the insulating oil plays a key role inside the transformer, once the transformer has an oil leakage problem, the oil volume will be reduced, which affects the normal operation of the transformer. Oil leakage may not only cause equipment failure, but also cause environmental pollution.

3. Poor short-circuit resistance

The short-circuit resistance of oil-immersed transformers is relatively weak. When the transformer is impacted by a short-circuit current, its windings may be subjected to severe mechanical and thermal stresses, causing the windings to deform, be damaged or burn. In addition, the short-circuit current may also cause arc discharge and local overheating inside the transformer, further aggravating its degree of damage. Therefore, for oil-immersed transformers, effective short-circuit resistance measures need to be taken, such as increasing the mechanical strength of the windings, optimizing the structure and layout of the windings, etc., to improve their short-circuit resistance.

4. Oil maintenance requirements

Oil-immersed transformers require regular inspection and maintenance of the oil condition, including oil testing, oil filtering and replacement, to ensure the normal operation of the transformer.

5. Large size and weight

Compared with other types of transformers, oil-immersed transformers are usually larger in size, occupy a large area, and are heavier, requiring additional support and equipment during installation and transportation.

6. Environmental issues

Since transformer oil is a petroleum-based liquid and there is a possibility of combustion, oil-immersed transformers have certain disadvantages in terms of environmental protection. Although transformer oil is widely used in power systems, its handling and disposal need to follow strict environmental regulations to prevent harm to the environment and human body.

In addition, there are some differences and advantages and disadvantages in the comparison between oil-immersed transformers and dry-type transformers:

‌Capacity and voltage level‌: Dry-type transformers are generally suitable for small capacity and low voltage level, while oil-immersed transformers can be suitable for various capacity and voltage levels.

‌Applicable places‌: Dry-type transformers are suitable for places that require fire and explosion protection, such as large buildings and high-rise buildings; while oil-immersed transformers are suitable for outdoor or places with sufficient space to set up accident oil pools.

‌Maintenance cost‌: The maintenance cost of dry-type transformers is usually higher because of their high structural and material costs; while the maintenance of oil-immersed transformers is relatively simple, which is mainly regular replacement and inspection of oil.

When selecting and using oil-immersed transformers, it is necessary to fully consider their advantages and disadvantages, and reasonably configure and maintain them based on actual conditions to ensure the normal operation of the equipment and stable power supply of the system.