What are the Factors Affecting the Operation Life of the Transformer?

20Dec

What are the Factors Affecting the Operation Life of the Transformer?

 

 

What are the Factors Affecting the Operation Life of the Transformer?

1. The thermal aging
The higher the working temperature, the faster the chemical reaction of transformer insulation materials, the faster the loss of mechanical strength and electrical strength, the greater the relative aging rate, the shorter the operation life of the transformer.
According to the research results, when the winding hot spot temperature of oil-immersed power transformer is in the range of 80 ℃ ~ 140 ℃, the relative aging rate of transformer increases by one time and the service life decreases by one and a half when the winding temperature increases by 6 ℃. Therefore, overheating is one of the main factors to shorten the life of large power transformers.

2. Electrical aging
It is generally considered that partial discharge is the main cause of transformer insulation aging. In recent years, although the level of transformer manufacturing technology has been greatly improved, but still can not avoid the transformer oil and other insulating materials in the air gap or bubbles. The dielectric constant of gas is smaller than that of transformer oil and other insulating materials. The smaller the dielectric constant is, the greater the electric field strength is, so the field strength at the air gap and bubble is stronger, and the breakdown field strength of gas is lower than that of transformer oil and insulating materials, so it is easy to start partial discharge in the bubble. There are trace moisture and impurity in transformer oil, and partial discharge is easy to occur under the action of electric field. In addition, due to the unreasonable design of the transformer, the field strength of some parts is higher than other positions, and the internal connection of the transformer is poor and other reasons will cause partial discharge. Partial discharge develops continuously, and eventually leads to insulation breakdown, which affects the transformer life.

3. The moisture
In the manufacturing process of the transformer, the manufacturer strictly controls the moisture content of the product. Generally, the transformer has to go through the coal and oil phase drying, vacuum oil injection, hot oil cycle and other water removal processes, but there will still be a certain amount of moisture. The late operation, especially the overhauling of the lifting cover, will inevitably invade part of the water, and the transformer oil will decompose water after thermal aging. The moisture in the transformer is mainly accumulated in the insulating paper board and insulating oil, which will deteriorate the electrical performance of the transformer oil and insulating paper, so that the electrical resistance is reduced, and the breakdown strength decreases sharply with the increase of water content. Moisture can also degrade with insulating materials, accelerating the aging of insulating materials. Research shows that insulating paper aged 11 times faster at 2 percent humidity than at 0.3 percent humidity.

4. Transformer oil aging
Transformer oil will gradually age under the action of electricity, heat and oxygen. After the aging of transformer oil, the inspirability of the oil is enhanced, and the degree of polymerization is also enhanced, resulting in the increase of gas in the oil and the increase of kinematic viscosity. The increase of gas will cause the breakdown voltage of oil insulation to drop, the increase of operating viscosity affects the circulation convection and heat transfer ability, and can not adapt to the operating condition of the transformer, and form a vicious cycle, seriously affect the operating life of the transformer, and even cause equipment accidents.

5. The influence of external natural forces
Wind, heavy rain, snow, hail, earthquake and other external factors will also affect the life of the transformer, should be based on the actual situation to prevent, if necessary, power outage.

What are the Factors Affecting the Operation Life of the Transformer?


1. The thermal aging

The higher the working temperature, the faster the chemical reaction of transformer insulation materials, the faster the loss of mechanical strength and electrical strength, the greater the relative aging rate, the shorter the operation life of the transformer.

According to the research results, when the winding hot spot temperature of oil-immersed power transformer is in the range of 80 ℃ ~ 140 ℃, the relative aging rate of transformer increases by one time and the service life decreases by one and a half when the winding temperature increases by 6 ℃. Therefore, overheating is one of the main factors to shorten the life of large power transformers.


2. Electrical aging

It is generally considered that partial discharge is the main cause of transformer insulation aging. In recent years, although the level of transformer manufacturing technology has been greatly improved, but still can not avoid the transformer oil and other insulating materials in the air gap or bubbles. The dielectric constant of gas is smaller than that of transformer oil and other insulating materials. The smaller the dielectric constant is, the greater the electric field strength is, so the field strength at the air gap and bubble is stronger, and the breakdown field strength of gas is lower than that of transformer oil and insulating materials, so it is easy to start partial discharge in the bubble. There are trace moisture and impurity in transformer oil, and partial discharge is easy to occur under the action of electric field. In addition, due to the unreasonable design of the transformer, the field strength of some parts is higher than other positions, and the internal connection of the transformer is poor and other reasons will cause partial discharge. Partial discharge develops continuously, and eventually leads to insulation breakdown, which affects the transformer life.


3. The moisture

In the manufacturing process of the transformer, the manufacturer strictly controls the moisture content of the product. Generally, the transformer has to go through the coal and oil phase drying, vacuum oil injection, hot oil cycle and other water removal processes, but there will still be a certain amount of moisture. The late operation, especially the overhauling of the lifting cover, will inevitably invade part of the water, and the transformer oil will decompose water after thermal aging. The moisture in the transformer is mainly accumulated in the insulating paper board and insulating oil, which will deteriorate the electrical performance of the transformer oil and insulating paper, so that the electrical resistance is reduced, and the breakdown strength decreases sharply with the increase of water content. Moisture can also degrade with insulating materials, accelerating the aging of insulating materials. Research shows that insulating paper aged 11 times faster at 2 percent humidity than at 0.3 percent humidity.


4. Transformer oil aging

Transformer oil will gradually age under the action of electricity, heat and oxygen. After the aging of transformer oil, the inspirability of the oil is enhanced, and the degree of polymerization is also enhanced, resulting in the increase of gas in the oil and the increase of kinematic viscosity. The increase of gas will cause the breakdown voltage of oil insulation to drop, the increase of operating viscosity affects the circulation convection and heat transfer ability, and can not adapt to the operating condition of the transformer, and form a vicious cycle, seriously affect the operating life of the transformer, and even cause equipment accidents.


5. The influence of external natural forces

Wind, heavy rain, snow, hail, earthquake and other external factors will also affect the life of the transformer, should be based on the actual situation to prevent, if necessary, power outage.