Reasons for temperature rise during power on operation of high-voltage switchgear
2025-11-12
After familiarizing ourselves with high-voltage switchgear, let's learn together about the reasons for the heating up of high-voltage switchgear during power on operation. Would you be interested in this? We are dedicated to providing you with high-quality service. Let's take a look together.
(1) The expansion effect of different metals varies. The metal expansion coefficient of steel bolts is much smaller than that of copper and aluminum busbars, especially for bolted equipment joints. During operation, with changes in load current and temperature, the degree of expansion and contraction of aluminum or copper and iron will differ, resulting in creep. That is, the metal slowly undergoes plastic deformation under stress, and the creep process is also closely related to the temperature at the joint. Practice has proven that when the operating temperature at the joint exceeds 80 ℃, the joint metal will expand due to overheating, causing the contact surface position to shift, forming small gaps and oxidizing. When the load current decreases and the temperature drops back to the original contact position, due to the coverage of the oxide film on the contact surface, it is impossible for the metal to metal direct contact during the original installation. The increased contact resistance in each cycle of temperature change will lead to an increase in heat in the next cycle, which in turn will further deteriorate the working condition of the joint, thus forming a vicious cycle.
(2) The data obtained from type testing is usually completed in the laboratory, with a short duration, usually not exceeding 8 hours, and does not have a cumulative effect of temperature rise. It cannot be equated with equipment that operates for a long time and continues to generate heat.
(3) Improper pressure on the fastening bolts at the connection point. Some installation or maintenance personnel believe that tightening the connecting bolts on the conductor connection is better, but this is not the case. Especially for aluminum busbars, the elastic coefficient is small. When the pressure of the nut reaches a critical pressure value, if the material's strength is poor and improper pressure is further increased, it will cause deformation and bulging of the contact surface, which will reduce the contact area and increase the contact resistance, thereby affecting the contact effect of the conductor. The conductivity of the selected conductor material does not meet the requirements, mostly due to insufficient purity of the conductor raw material.
(4) Other factors on site, such as improper installation and maintenance processes, such as inadequate, uneven, and non smooth treatment of the contact surface of the busbar during processing, connection, and installation, resulting in a decrease in effective contact area, an increase in contact resistance, and heating.
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