Understanding Dry Type Transformer Temperature Rise

What temperature does a dry transformer run at?

Dry-type transformers have the advantages of simple structure, easy maintenance, and good fire resistance. And dry-type transformers have been widely used in power systems. However, dry-type transformers generate heat during operation. If the temperature is too high, it will affect its insulation performance and service life, and even cause safety accidents. Therefore, accurately grasping the operating temperature range of dry-type transformers and taking effective temperature monitoring and control measures are of great significance to ensure the safe and stable operation of dry-type transformers.

Normal operating temperature of dry type transformer

The normal operating temperature range of dry-type transformers is usually between -40℃ and +40℃. Within this temperature range, the transformer can work normally and has stable performance. However, in actual operation, the temperature of the transformer will be affected by many factors, such as ambient temperature, load conditions, ventilation conditions, etc. Specifically:

1. Winding hot spot temperature

The winding hot spot temperature of a dry-type transformer is an important indicator for measuring its operating temperature. Generally speaking, the winding hot spot temperature of a dry-type transformer shall not exceed the allowable temperature of its insulation material. Common dry-type transformer insulation material grades are F and H. The maximum allowable temperature of F-class insulation material is 155°C, and the maximum allowable temperature of H-class insulation material is 180°C. In actual operation, in order to ensure the long-term reliable operation of the transformer, a certain margin about 10-20°C lower than the maximum allowable temperature is usually left to control the winding hot spot temperature.

2.Top oil temperature

The top oil temperature is also an important parameter reflecting the operating temperature of the dry-type transformer. Although there is a certain difference between the top oil temperature and the hot spot temperature of the winding, the operating temperature of the transformer can usually be indirectly judged by the top oil temperature. Generally speaking, the top oil temperature of the dry-type transformer should not exceed 105℃. In special circumstances, such as short-term overload operation, the top oil temperature can be appropriately increased, but it cannot exceed the temperature range allowed by the insulation material.

Monitoring and control of operating temperature of dry-type transformers

1. Temperature monitoring

In order to timely grasp the operating temperature of dry-type transformers, it is necessary to monitor their temperature. Common temperature monitoring methods include thermocouple temperature measurement and infrared temperature measurement. Thermocouple temperature measurement is to install thermocouples on the windings or cores of the transformer to directly measure its temperature; infrared temperature measurement is to use infrared thermal imagers to perform non-contact measurement of the surface temperature of the transformer. Through temperature monitoring, abnormal temperature of the transformer can be discovered in time and appropriate measures can be taken to deal with it.

2. Temperature control

When the operating temperature of the dry-type transformer exceeds the allowable range, effective temperature control measures need to be taken. Common temperature control methods include reducing the load, strengthening ventilation and heat dissipation, and installing cooling devices. During the operation of the transformer, the load should be adjusted in time according to the temperature monitoring results to avoid overload operation; at the same time, the transformer should be well ventilated, and cooling devices such as fans can be installed if necessary to enhance the heat dissipation effect.