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Basic Guide To Oil Immersed Transformer

oil immersed transformer guide

Oil-immersed transformers, also known as oil-filled transformers, use oil as an insulating and cooling medium. Oil-immersed transformers have the characteristics of reasonable structure, excellent performance, economy and low noise. It is more suitable for urban and rural, industrial and mining enterprise power grid transformation and transformers for combined transformers and prefabricated substations.

The Daelim factory is located in Hai’an, Jiangsu, with a superior geographical location and convenient transportation. Daelim can provide customization: oil-immersed power transformers, dry-type transformers, substations, and various special-shaped transformers with customization. All the performance indicators of the products have reached the relevant national and international standards.

Pad-mounted Transformer

Single phase and three phase pad mounted transformer

Small-substastion Transformer

Rated Capacity: Up to 20MVA; Rated Voltage: Up to 44KV;

Single Phase Pole Mounted Transformer

Frequency: 50/60Hz; Rated Power Rating: 5~333kva

Oil Immersed Power Transformer

Rated voltage:Up To 400 kV Rated Power: 10MVA-300MVA

Table of Content

What is oil immersed transformer?

oil immersed transformer
oil immersed transformer

The oil-immersed transformer has three-dimensional wound iron core has no air gap in its magnetic circuit because its three core columns are three-dimensionally arranged in an equilateral triangle, and the winding is tighter, the three magnetic circuits have the same length and the shortest, and the cross-sectional area of the core leg is closer to a circle, so the performance is further improved, the loss is reduced, the noise is reduced, the three items are balanced, and the third harmonic component is reduced. But since the pressure regulating switch is inside the tank. The contacts of the switch are not visible from the outside when adjusting the pressure. There are two reaction phenomena: if the contact is not good, the circuit is broken. If the contact is not good, it is easy to burn the switch when the load is too large.

The oil-immersed transformer is an important piece of equipment in power systems, it is mainly used to change voltage and transmit electrical energy.  Oil-immersed transformers work mainly on the principle of electromagnetic induction. It is suitable for power grid transformation of urban and rural, industrial and mining enterprises, and more suitable for combined transformers and transformers for prefabricated substations.

Operating temperature of oil immersed transformer

When the oil-immersed transformer is working, it is necessary to ensure that the working temperature will not cause the transformer oil to deteriorate too quickly, thereby increasing the operating cost. When the oil at the operating temperature of the oil-immersed transformer reaches 85 degrees Celsius, it will alarm, and when the maximum temperature reaches 95 degrees Celsius, the switch of the transformer will be turned off.

Therefore, the oil temperature that specifies the operating temperature of the upper layer of the oil-immersed transformer cannot exceed 85°C. The rated capacity of the transformer refers to the maximum power allowed for long-term continuous operation when the transformer can obtain economical and reasonable efficiency and normal expected service life under the specified ambient temperature. The ambient temperature specified by the transformer is that the maximum temperature is 40°C, the maximum daily average temperature is 30°C, the maximum annual average temperature is 20°C, the minimum temperature for outdoor transformers is -25°C, and the minimum temperature for indoor transformers is -5°C.

According to operating experience and special research, when the insulation temperature of the transformer winding is in the range of 80-140 °C, the loss of insulation life will be doubled for every 6 °C increase, and the service life will be reduced by half. This is the 6 °C rule for transformer operation. The maximum allowable temperature of the transformer winding for long-term operation is the normal life temperature, and the maximum allowable value of the winding hot spot temperature is the safe temperature.

In order to make the insulating material obtain the most economical service life, it is divided into different heat-resistant grades such as Y, A, E, B, F, H, C, etc., according to its maximum allowable working temperature under normal conditions. Among them, the Y grade insulation has the highest allowable temperature The working temperature is 90°C, A grade is 105°C, E grade is 120°C, B grade is 130°C, F grade is 155°C, H grade is 180°C, and C grade is above 180°C.

Oil immersed transformer vs dry type

oil immersed transformer vs dry type
oil immersed transformer vs dry type

The oil-immersed transformer is the transformer coil and core soaking in dedicated transformer oil, the benefits of this are, namely can the cooling coil can cut off from the air to prevent moisture in the air cause corrosion to the transformer’s core, and the same time can also play a role of arcing, so early in our country, electric power transformer and the power switch is in the oil .

The dry transformer core and the coil as a whole, are fixed, can be directly exposed to the air, and can also be placed indoors, but the temperature and humidity requirements of the environment are very high. Its characteristics can be unattended, as long as the regular check is on the line.

The cooling medium and insulating material for their windings and other components is the use of dry-type transformers. Their main purpose and general purpose are the same as that of oil-immersed transformers, which is to adjust the primary voltage of the transformer to a level commonly used in industry, households, and businesses.

Working principle of oil-immersed transformer

The oil-immersed transformer is an important power. Its main functions are becoming more and more complex, and the structure of various oil-immersed transformers is also increasing. Oil-immersed transformers can adapt to more working environments.

Oil-immersed transformers have windings, iron cores, and bushings to work together. The role of the magnetic core is to provide a path for the magnetic current. The heat of the equipment in it can be reduced. The purpose of the bushing is to connect the transformer windings to the substation.

Precautions for oil-immersed transformers

1. The building where the transformer is placed must meet the fire resistance level requirements specified in the building fire protection code;

2. In the event of a fire, measures must be taken to prevent the outflow of oil from causing the fire to spread;

3. There must be fire-extinguishing measures to extinguish oil-based fires.

Tips of oil immersed transformer

Oil-immersed transformer is one of the important electrical equipment, in various industries, it plays a more important role in the realization and operation of oil-immersed transformers, filling oil When the model of oil-immersed transformer is running, pay attention to oil filling oil , status and use related precautions are useful for the normal operation of oil-immersed transformers, otherwise the work and operation of oil-immersed transformers will be affected.

Oil immersed transformer advantages

oil immersed transformer advantages
oil immersed transformer advantages

When the oil-immersed transformer in operation needs to be supplemented with oil-immersed transformer oil, the type of oil-immersed transformer oil should be determined first, and then filled with oil-immersed transformer oil of the same grade, because different types of oil-immersed transformer oil cannot be mixed at will.

If you really can’t find the same oil-immersed transformer oil and really need to add fashion, you should first understand the oil-immersed transformer oil, the physical properties of the oil-immersed transformer oil you want to add, such as density, viscosity, freezing point, flash point It is closed, and then the stability test, two oil samples, according to the needs, the ratio of the mixture in the container for one month, observe whether there is any change, such as no deposits found in production, and meet the standard oil-immersed transformer insulating oil, you can use.

Why do we use transformer oil in the oil immersed transformers?

transformer oil
transformer oil

After adding the new oil-immersed transformer oil, it must pass a test injection. Even if the new and old oil-immersed transformer oil passes the test, it still needs to be mixed after the test. Its physical and chemical properties, brand, and origin are not limited to petroleum, or trademarks, there should be an actual mixing ratio, and mixing experiments can be used later only after qualification.

Electricity has become an indispensable energy source in people’s lives, and now overhead wires and transformers of different sizes can be seen everywhere in cities and rural areas. When electricity is transmitted over long distances, in order to reduce the losses in the line, it is necessary to use transformers in power plants to increase the voltage to thousands or even hundreds of thousands of volts.

Obviously, electricity with such a high voltage cannot be directly used for general industrial machinery and household appliances. It is necessary to reduce the voltage to 100-240 volts through a transformer, so as to ensure the safety of electricity use.

The oil-immersed transformers produced by Daelim combine advanced manufacturing technology and equipment, which can realize computer remote communication, testing, adjustment, and control. And all oil-insulated transformers are certified by the State Machinery Industry Bureau and the State Power Company.

Daelim designs and manufactures durable oil-immersed transformers for use in harsh industrial environments for long and reliable service life even in such environments. Daelim’s oil immersed medium voltage transformers are ideal for applications requiring larger and higher voltages.

Mineral oil is the standard configuration for our oil immersed transformers produced by Daelim, it can also provide environmentally friendly vegetable oil according to customer requirements.

If you would like more information on the best oil immersed transformer wholesales, you are welcome to contact DAELIM at any time you want or request a quote. In short, Daelim can carry out a series of customized services to meet the needs of customers. Welcome to discuss more opportunities to cooperate.

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About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.