Reasons for the temperature rise in the high voltage switchgear

The components in the high-voltage switchgear will produce operating temperature during operation, which is called temperature rise. Excessive temperature rise has a greater impact on the performance of insulating parts and equipment life, and long-term temperature rise will cause insulation performance. Decrease, resulting in insulation breakdown accidents. What are the main reasons for the increase in the temperature of the high-voltage switchgear?

1. The test data is usually completed in the laboratory, the duration is not long, generally not more than 8h, does not have the cumulative effect of temperature rise, and cannot be equal to the equipment that runs for a long time and continues to generate heat.

2. Different metals have different expansion effects. The metal expansion coefficient of steel bolts is much smaller than that of copper and aluminum bus bars, especially bolt-type equipment joints. As the load current and temperature change during operation, the degree of expansion and contraction of aluminum or copper and iron will be different and creep, which is the slow plastic deformation of metal under the action of stress. The creep process also has a great relationship with the temperature at the joint.

3. Improper pressure on the fastening bolts at the connection part. Some installation or maintenance personnel think that the tightening of the connecting bolts, the better when connecting the conductors, but this is not the case. Especially the aluminum bus bar has a small elastic coefficient. When the pressure of the nut reaches a certain critical pressure value, if the strength of the material is poor, and then continue to increase the improper pressure, it will cause part of the contact surface to deform and bulge, which will reduce the contact area and increase the contact resistance, thereby affecting the conductor contact effect .

4. The conductivity of the selected conductor material does not meet the requirements, and most of the conductor materials are not pure enough.

5. Other factors on site, such as improper installation and maintenance process. For example, in the process of processing, connecting, and installing the busbar, the contact surface of the busbar is not properly treated, uneven, not smooth, and not coated with special electric grease, etc., which causes the effective contact area to decrease and the contact resistance increases and heat generation.

If the temperature in the switch cabinet is too high, it will cause the insulation breakdown accident and the life of the switch cabinet equipment. Therefore, pay special attention to the temperature changes in the switch cabinet during installation and operation.