The reason for the heating up of the high-voltage switchgear when it is energized

After a brief familiarity with the high-voltage switchgear, and let’s learn the reasons for the heating up of the high-voltage switchgear when it is energized, I don’t know if you will be interested in it? We are dedicated to providing you with the best quality service, let’s take a look.

(1) The expansion effect of different metals is different. The metal expansion coefficient of steel bolts is much smaller than that of copper and aluminum busbars, especially bolt-type equipment joints, with the change of load current and temperature in operation, the expansion and contraction degree of aluminum or copper and iron will be different and creep, that is, the slow plastic deformation of metal under the action of stress, and the creep process is also very related to the temperature at the joint. It has been proved in practice that when the operating temperature at the joint exceeds 80°C, the joint metal will expand due to overheating, so that the contact surface position is staggered, forming a small void and oxidizing. When the load current decreases and the temperature decreases back to the original contact position, due to the coverage of the oxide film on the contact surface, it is impossible to have direct contact between the metals during the original installation. The increase in contact resistance of each cycle of temperature change will increase the heat of the next cycle, and the increased temperature will further deteriorate the working condition of the joint, thus forming a vicious circle.

(2) The measured data of the type test is usually completed in the laboratory, and the duration is not long, usually not more than 8 hours, and it does not have the cumulative effect of temperature rise, and cannot be equated with long-term operation and continuous heating equipment.

(3) Improper pressure of fastening bolts at the connection part. Some installers or maintenance personnel think that the tighter the connecting bolts are tightened in the conductor connection, the better, but in fact, this is not the case. Especially for aluminum busbar, the elastic coefficient is small, 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 the contact surface to be partially deformed and raised, but the contact area is reduced, the contact resistance is increased, and the conductor contact effect is affected. The conductivity of the selected conductor materials does not meet the requirements, and most of them belong to the insufficient purity of the conductor raw materials.

(4) Other factors on site, such as improper installation and maintenance process, such as the bus in the process of processing, connection and installation, the contact surface of the bus bar is not in place, uneven, not smooth, and no special power grease is applied, etc., resulting in the effective contact area decreases and the contact resistance increases and heats.