Oil Immersed Transformer

As one of the professional oil filled transformer manufacturers, our oil immersed type transformer is specially developed and designed based on the advanced technology abroad for rough mountainous topography and transportation difficulties to meet the requirement of China oil type transformer Grid at a good oil immersed transformer price. The main characters of the oil filled transformer are low loss, low noise, and strong resistance of short circuit and free of core checking. We offer different transformer oil immersed types including 220KV Power Transformer, 110KV Power Transformer, 35 kv transformer and earthing transformer. Contact us to get more about oil immersed type now!

Oil Immersed Transformer Types

How to Choose a Transformer: Dry Type vs. Oil Cooled

There are two types of transformers in the industry: dry type power transformer and oil immersed transformer. Dry use air as the cooling medium, liquid cooling uses oil. Although the final results of both types are the same, there are still many differences between different types of power transformers, which will affect the type you choose.


Maintenance: Oil immersed type transformers require more maintenance procedures, and are more often performed than dry type power transformers. Oil sampling is required to test contaminants, while dry type transformers are very resistant to chemical contaminants.

Cost (initial and operational): Dry type transformer has higher operating losses than oil immersed one. And the advantages of dry type transformer over oil cooled transformer is that it has higher standard energy efficiency, so it has longer service life than a dry type transformer.

Noise: The operating sound pressure of oil immersed transformer is lower, so it has less noise pollution than a dry type transformer.

Recyclability: Life cycle recovery of dry type transformer is limited, while core/volume recovery of oil immersed one is easier. Our oil immersed transformer has excellent service life and maintainability, and produces less waste, and requires less replacement and labour.

Efficiency: Dry type power transformers are larger devices, but their voltage and size are limited, and they are more likely to overheat if overload happens. As a result, dry type transformers have higher power losses and cost more to keep dry power over time. Oil immersed distribution transformers are smaller and more efficient. They need less and create smaller environmental footprints.

Voltage capacity: Dry type transformer is designed to deal with medium and small MVA and rated voltage, making it an ideal choice for small applications. Oil immersed distribution transformer can bear a heavier load, so it is for higher voltage application.

Location: The location difference between oil and dry transformers will be the critical determinant of which type you need. Dry type is specified for use near buildings and buildings only because they are safer for the environment. Dry type power transformer is not flammable and has little fire hazard, which makes it very suitable for large shopping centres, hospitals, residential quarters and other commercial areas. Oil filling transformers will be used when installed outdoors, which may cause oil leakage and may cause fire, but these equipment are more environmentally friendly."


What Is the Purpose of Oil in a Transformer?

First, oil insulation is used to cover all parts that do not have solid insulation in the power transformer main body. Oil in a transformer also penetrates into the paper and fills the air gap, thus improving the quality of the paper insulation.

Another purpose of oil in a transformer is to spread heat from the core to the radiator, in which heat can be more easily distributed to the outside.


Maintenance of the Oil in a Transformer

1. Prevent impurity, damp, water and polluted air from entering into oil tank when filtering and filling insulation oil into the tank. It is prohibited to filter oil from one tank to another tank in a rainy day.

2. The oil container must be cleaned strictly and sealed completely. Or the container must be equipped with dehumidifier if the container is not sealed completely.

3. Generally please use as far as possible the insulation oil provided by manufacturer. If it’s necessary to complement other type of oil, it must comply with regulations of mixing oil, and the oil should be tested by specific department to make sure of their compatibility. If the two types of oil are not compatible, it’s prohibited to use mixed oil.

4. Transformer oil must meet the following technical specifications in Table 1.


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Oil Immersed Transformer Parts

1. Core

① The core is made of high magnetic permeability silicon steel to reduce load loss and noise of transformer.

② The multistage step lapped core shall be cut with a 45°joint seam, and pore-free binding construction, which reduces the noise as well as power consumption. The burrs are less than 0.02mm.

③ The core is rigidly clamped with insulated clamping bolt, or by other method, between the core column and winding which will retain its shape under the most severe stresses encountered during shipment and handling and under short-circuit conditions.


2. Winding

① The coils have been wound and assembled on high quality hard insulation cylinder.

All coils are strengthened with insulation strip to improve the ability of short-circuit withstanding.

② All tapping coils are arranged in that voltage between turns are distributed evenly.

All terminals are banded with shrink band to strengthen ability of short—circuit withstanding.

③ HV winding are entangled with continuous structure, in order to improve the impulse voltage and all electric field are well distributed. 

④ All insulation strip and press board are used to improve the insulation ability and reduce partial discharge.

⑤ There are oil channel in the coil to lower partial temperature rise.

⑥ The assembled core and coils is vacuum dried in constant temperature conditions. Meanwhile, the kerosene gas state drying device is used as well.


3.Tank and assembly

① The tank is in bell-shaped construction or conventional construction as required. The sealing parts of the tank is subjected to special treatment and be strengthened with steel strips. 

② Tank is thoroughly oil tight and be capable of withstanding a pressure as per standard without distortion and damage.

③ Qualified oil is filled in by vacuum.

④ All tanks are of electrically welded mild steel and oil tight.


4. Cooling plant and accessories

① Radiators are detachable. A valve at each point of connection to the tank with drain and filling plug is fitted, and can withstand the pressure conditions as requirements.

② There is a rubber bag inside of conservator. Each conservator vessel is fitted with a silica gel dehydration breather to isolate air and oil.

③ All accessories are from the best quality manufacturer in China or aboard so as to assure the quality of oil immersed power transformer.


Difference between Dry Type Transformer and Oil Immersed Type Transformer

Dry Type Transformer

For dry type power transformers, an insulation system is needed to maintain their low temperature, so these devices are larger and use larger coils than the oil immersed type transformers at the same rated voltage/capacity. In addition, dry type transformers use more materials, resulting in higher costs. In terms of performance, the power distribution unit can operate at a higher temperature because the natural cooling mechanism is not always stable and is susceptible to the surrounding environment, which leads to shorter service life.

Our dry type power transformers service life: 20 to 25 years.


Oil Immersed Type Transformer

Oil immersed transformer is cooled by combustible liquid, so it is very suitable for outdoor use. It is important to emphasize that the progress of oil immersed transformer technology from Hanzhong oil immersed power transformer manufacturer replaces fuel oil with a more stable (less flammable) oil so that the oil immersed power transformer can be used in strict environmental standards. Oil filled transformers provide a better cooling effect than dry type transformers because the oil is a more thorough medium in the cooling application. Efficient cooling mechanisms can also turn out a smaller, more compact device.

Perhaps the biggest advantage of oil immersed power transformer is that these devices can handle higher rating voltage/capacity. Dry type transformer is usually used for low rating applications.

Our oil immersed type transformers service life:30 to 35 years.