Aug. 04, 2025
Oil-immersed power transformers have many benefits, particularly their efficient cooling capabilities. They are used in many industries and can be found at both electrical substations and power distribution centers. Read on to learn more about oil-filled transformers and how they may be useful to you.
Transformers change an alternating current (AC) to a higher or lower voltage. A current may need to move to a higher voltage as higher voltages are easier and faster to transport. A current may need to decrease its voltage in residential, commercial, and industrial areas.
One type of transformer is an oil-immersed transformer. Transformers often operate in high-energy, high-heat situations. An oil-filled transformer suspends the transformer of a steel tank filled with oil. The oil cools and insulates the transformer. The device uses convection to move the oil around and through the transformer, cooling it off.
To avoid oil deterioration, transformer oil must be kept at an operating temperature of less than 85°C. For the transformer to run correctly and to prevent excessive oil deterioration, the daily average operating temperature should be around 30°C.
Substations and power distribution areas use oil-immersed transformers. An oil-immersed transformer is similar in design to a regular transformer. It’s made up of three main parts: a magnetic core at the center that is surrounded by coils and bushings.
The magnetic core and windings create a magnetic field, allowing the current to pass through. Windings are insulated, with higher voltages needing thicker insulation. Bushings transmit the electricity to its next destination, typically a substation.
Oil-filled transformers change a current to a higher or lower voltage using the principle of induction. This process creates a surplus of heat. The oil helps to keep the transformer from overheating.
The windings and core are submerged in transformer oil. It acts as a cooling agent and an insulator. Convection moves the oil through the windings, coils, and core, keeping the transformer from overheating. Oil is further cooled externally at lower voltage and in an air-cooled radiator with higher voltages.
There are several types of oil-filled transformers. Here are a few of the most common below.
 
Contractors typically have to choose between oil-filled and dry-type transformers. Both have their advantages. Let’s delve into some of the reasons that an oil-filled transformer may be the right choice for you.
First, oil-filled transformers are more affordable. They are often up to half the price of a dry-type transformer with the same capacity.
Oil-immersed transformers tend to be more successful at cooling the transformer than a dry type. Oil is a better cooling medium. They also have a higher voltage capacity. Dry-type transformers operate below 35 kV, while there are no limits with oil-immersed. Oil transformers are more versatile.
Dry-type can typically go from an intermediate location to the power consumption source. Oil-immersed can function as both power and distribution transformers.
Oil-filled transformers are better for the environment, as they are much easier to recycle than dry-type. They are also smaller and work best in outdoor environments in case of an oil spill or other accident.
Oil-immersed transformers have maintenance and safety considerations. Keeping your transformer well-maintained can lengthen its lifespan and reduce the risk of safety issues.
You should perform regular visual inspections and cleanings. Check the transformer to ensure that all parts are in good condition and that there is no threat of leaks. Make sure that all fittings are tight. Clean the exterior and interior of the transformer to remove dust, dirt, and other debris.
It’s also essential to check the oil frequently. Make sure that the oil is at its proper level. You should also take samples of the oil and have it tested. You don’t want to use contaminated oil. Finally, keep an eye on the temperature and air pressure. You want to be sure that the transformer is within the suggested levels.
As with any electrical equipment, there is always a risk of fire. In the event of a fire, it’s important to ensure that the oil doesn’t leak out from the transformer. Oil can cause the fire to spread, making a hazardous situation even more dangerous.
Oil-immersed transformers provide many benefits and are often a better choice than dry-type transformers. They are efficient and affordable and can run at almost any capacity. While they do require maintenance and pose some safety risks, with the proper care and use, you’ll be able to get the most out of your equipment.
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Chint Global is dedicated to providing high-quality electrical equipment for your business needs. We offer several safe and reliable oil-immersed transformers to fit a variety of situations. Contact one of our expert representatives today to help you choose the best transformer for your needs.
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Oil transformer is a common type of power transformer. It uses insulating oil to cool and insulate the internal components of the transformer.
Oil-immersed transformers consist of two or more coils (primary and secondary windings) and an iron core. These coils and cores are soaked in insulating oil to maintain their cooling and insulating properties.
Insulating oil plays an important role in oil-immersed transformers. It not only effectively cools the internal components of the transformer, but also provides insulation protection from arcing and discharge. At the same time, insulating oil also has good electrical insulation performance and stability, and can work stably for a long time in high temperature environments.
Oil-immersed transformers are widely used in power transmission and distribution systems, industrial equipment, construction and other fields. They are often used to transform and regulate voltage to suit the needs of different power systems. The capacity of oil-immersed transformers ranges from a few kilowatts to hundreds of megawatts, and the specific specifications and models are determined according to actual needs.
The working principle of oil-immersed transformer is based on electromagnetic induction and transformer principles.
When AC current from the input power supply passes through the main winding, the resulting magnetic field creates magnetic flux in the iron core. This flux passes through the adjacent secondary winding, causing another voltage to be induced in the secondary winding.
Specifically, when the current in the main winding changes, it creates an alternating magnetic field. This alternating magnetic field causes the ferromagnetic material in the core to undergo magnetization and demagnetization processes. This process creates a potential difference in the secondary winding, causing the current in the secondary winding to change accordingly.
According to the principle of a transformer, the transformation ratio between the primary and secondary windings is determined by the turns ratio of the windings. If the number of turns of the main winding is larger than that of the auxiliary winding, the output voltage will decrease; conversely, if the number of turns of the main winding is smaller than that of the auxiliary winding, the output voltage will increase.
In oil-immersed transformers, insulating oil plays an important role. First, the insulating oil cools the internal components of the transformer and keeps its operating temperature within a safe range. Secondly, insulating oil has good insulation properties and can prevent arcs and discharges.
In summary, the working principle of an oil-immersed transformer can be attributed to converting the voltage of the input power supply into the required output voltage through electromagnetic induction between the primary and secondary windings under the cooling and insulation protection of insulating oil.
Select the rated capacity of the transformer according to the load type and load power. If the load is a peak load such as a motor or a frequency converter, a transformer with a larger overload capacity needs to be selected.
Select the corresponding transformer model according to the input voltage and output voltage requirements.
The transformer needs to be placed in a ventilated, dry, dust-free, and non-corrosive gas environment to avoid being affected by water, moisture, dust, etc. Select transformers with special requirements such as corrosion resistance, moisture-proof, and explosion-proof according to the actual situation.
Choose the appropriate product based on the service life and maintenance cost of the transformer. Generally speaking, products with high brand awareness, mature technology, and easy maintenance are more reliable.
Choose a transformer with good safety performance such as overload and short-circuit protection to ensure the safety of equipment and personnel.
Choose the right product according to your budget. Don’t just consider the price and ignore the quality and reliability of the product.
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