How Much Do You Know about Vacuum Drying Of Transformer?

The transformer is a common component widely used in industrial production and daily life. However, the transformer is easily affected by the environment during installation or transportation, which causes the transformer to be damp. Transformer dampness will affect the normal operation of the transformer, and even the service life of the transformer. The safe and reliable operation of the transformer affects the normal operation of the power system.

This article will introduce the vacuuming operation of transformer by vacuum drying and vacuum oiling in detail.

Introduction to Vacuum Oil Injection

Vacuum oil injection has many advantages. There are some bubbles in the transformer oil, which will affect the normal operation of the transformer and even the operation of the entire power system. In addition to improving the insulation level of the transformer and preventing breakdown accidents, vacuum oil injection can also reduce and eliminate air bubbles in the transformer oil. Therefore, the vacuum oiling of the transformer is of great significance to improve the life of the transformer and the normal operation of the power system.

What is the Vacuum Drying Process?

A large amount of insulating materials are installed inside the transformer. The composition of transformer is mainly composed of the iron core, coil, and shell. There are many insulating materials, such as winding turn insulation, electrostatic plates, as well as an insulating cylinder, lead insulation support, etc., which are composed of fibrous materials.

Water inflow into the transformer will reduce the insulation performance of the insulating material, seriously affect the normal operation of the transformer, and even cause safety accidents. The moisture in the insulating material can not only expand the insulating material, but also affect the geometric size, and more seriously, it will affect the electrical strength of the medium and the aging of the solid insulation. Therefore, vacuum drying of transformers plays a very important role in the process of transformer manufacturing and transportation and is also an important part of maintenance after transformers are flooded.

Power equipment such as transformers requires good insulation for strong electrical performance. The vacuum drying process is to ensure proper insulation of electrical equipment to ensure that the equipment does not fail. Of course, the vacuum drying process is also required for the vacuum oiling of the transformer oil.

How to Assess if Insulation is Good?

There are three properties that we can use to assess whether insulation is good.

Resistance to Electrical Current

The higher the resistance, the better the insulation, and the lower the resistance, the worse the insulation.

Dielectric Strength of Insulators

Dielectric strength refers to a measure of the electrical strength of a material as an insulator. It is defined as the maximum voltage per unit thickness when the specimen is broken down. If the dielectric strength of this material is larger, then its quality as an insulator is better.

Dielectric Loss

The energy is dissipated per unit time by a dielectric under the action of an electric field. Commonly used dielectric loss tangent value: tan delta (dielectric loss factor) to measure the size of dielectric loss.

Whether the insulation is good can be measured by judging these three properties.

Transformer Vacuum Drying Machine

How to Carry Out the Drying Process of the Transformer?

Insulation parameters are affected by the water content in the insulating material. The lower the water content in the insulating material, the better the insulating properties can be obtained. The drying process is the process of removing moisture from the insulating material. The insulation can be dried to some extent by heating the insulation and evaporating the water in the insulation.

However, the process of drying the insulating material by heating may damage the physical and chemical properties of the insulating material. The transformer also cannot evaporate water from the insulation by heating alone. This can damage the physical properties of the transformer and can also have dangerous consequences.

Therefore we need to carry out the drying process of the transformer without heating the transformer insulating material. Drying of insulating materials in transformers can be achieved at low temperature and low voltage levels. At low pressure or vacuum, the process of water evaporation is accelerated if enough heat is supplied to the insulating material. Therefore, in a vacuum environment, we can more easily achieve drying of insulating materials.

It is a scientific and simple choice to vacuum dry or evacuate power transformers through the transformer vacuum pump system.

Transformer Vacuum Drying Machine

Transformer Vacuum Pump System Produced by YUNENG

The transformer vacuum pump system produced by YUNENG is mainly suitable for vacuum oil filling and vacuum drying of various large power transformers such as 220kV, 500kV, ±800kV, and 1000kV.

The vacuum degree of the machine’s working can reach 10Pa, and the ultimate vacuum degree can reach 1Pa. The transformer evacuation system with vacuum pump produced by YUNENG has the advantages of simple operation and stable performance, and also has the advantages of the fast startup, high pumping speed, and preventing suck back.


If you have questions about the transformer vacuum pumping system, you can contact us at any time. YUNENG can provide you with professional solutions according to your specific needs.

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