What are the common reasons for the high temperature of KYN28 high-voltage switchgear?

What are the common reasons for the high temperature of KYN28 high-voltage switchgear?

The actual temperature rise inside the KYN28 high-voltage switchgear, especially in the connection parts of the busbar, is usually higher than the data measured in the type test. Main reasons:

(1) The type test data is usually completed in the laboratory, and the duration is not long, usually not exceeding 8 hours. It does not have a cumulative temperature rise effect and cannot be equivalent to equipment that operates 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 busbars, especially the copper waterproof joint JG-T-M of 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 vary, resulting in creep. This is the slow plastic deformation of the metal 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 ° C, the joint metal will expand due to overheating, causing the contact surface position to be staggered, forming small voids and oxidation. 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 to have direct contact between metals during the original installation. The increased contact resistance caused by each temperature change cycle 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 cycle.

(3) Improper pressure on the fastening bolts of the connecting parts.

Some installation or maintenance personnel believe that the tighter the connecting bolts on the conductor connection, the better, but in fact, it is not.

Especially for aluminum busbars, the elastic coefficient is small. When the pressure of the nut reaches a certain critical pressure value, if the material's strength is poor and improper pressure is continued to be added, it will cause deformation and uplift of the contact surface, instead reducing the contact area and increasing the contact resistance, thereby affecting the contact effect of the conductor.

(4) The conductivity of the selected conductor material does not meet the requirements, mostly due to insufficient purity of the conductor raw materials.

(5) Other factors on site, such as improper installation and maintenance processes, such as inadequate treatment, unevenness, smoothness, and lack of dedicated power grease on the contact surface of the busbar during processing, connection, and installation, may lead to a decrease in effective contact area and an increase in contact resistance, resulting in heating.

Eight reasons for high temperature rise in transformers:

1. The primary input voltage is too high.

2. The secondary load has excessive power, which means the load current is too high.

3. The decrease in insulation performance of the silicon steel sheet of the transformer results in an increase in eddy current in the iron core.

4. Excessive harmonic current.

5. The manufacturing process is poor [such as inserting a grab piece when inserting an iron sheet]

6. Unreasonable design with insufficient primary turns.

7. There are very few short circuits in the primary or secondary coils.

8. The ambient temperature is too high.

What should the maximum temperature of the switch contacts in the high-voltage switchgear not exceed?

Temperature at the connection of the switchgear.

The switch contact is considered to be connected by pressing.

Busbars and cable joints are considered as static connections.

The maximum temperature of the dynamic connection should not exceed 70 ° C.

The maximum temperature of static connection should not exceed 75 ° C.

There are many reasons for the high temperature of high-voltage switchgear.

-The output capacity exceeds the rated capacity.

The second reason is that the installation position is not good, there is sunlight, or the air is not flowing properly, resulting in poor heat dissipation.

The third issue is that there is a malfunction, poor contact, or ignition.

Any problem must be resolved in a timely manner, otherwise it can easily lead to accidents or dangers

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