What are the causes of insulation accidents in switchgear and how to monitor them?

What are the causes of insulation accidents in switchgear and how to monitor them?

Causes of insulation accidents in switchgear

1. Insufficient climbing distance and air gap

Insufficient creepage distance and air gap are the fundamental reasons for insulation damage accidents in switchgear. Especially for handcart cabinets, in order to shorten the size of the cabinet and significantly reduce the insulation distance between circuit breakers and isolation plugs installed in the cabinet, effective measures to ensure insulation strength have not been taken. 10kV high-voltage switchgear generally requires a net distance of air insulation not less than 125mm, but generally, switchgear cannot meet the countermeasures requirements and is generally solved by adding insulation sheath.

2. Poor manufacturing process and assembly quality

Poor manufacturing process and assembly quality have a significant impact on the overall withstand voltage level of the switchgear. Some components inside the switchgear can pass the withstand voltage test alone, but the overall switchgear cannot pass due to poor assembly quality. If the fastening screws are irregular, the screw will grow too many nuts after tightening; Some fastening base plates supporting ceramic columns are in a "D" shape, and special treatment is made at the supporting ceramic columns, which not only shortens the insulation distance, but also causes local electric field strength concentration, which is prone to insulation breakdown.

3. Fever caused by poor contact

When the contact capacity is insufficient or the contact is poor, the local temperature increases, and in severe cases, the current carrying components at this location are burned, causing arcing to the ground or between phases, resulting in insulation flashover. Generally, duckbill type switch contacts are prone to such faults, and the contact effect of plum blossom contacts is good. This type of fault is generally prone to occur after the switchgear is repaired and restored.

4. Deterioration of the cabinet environment causing insulator fouling and condensation

The environmental conditions under which the switchgear operates are the main cause of insulation flashover in the switchgear. Atmospheric pollution continues to intensify, gradually polluting the insulators, bushings, and busbars of power equipment. Based on the analysis of pollution flashover accidents over the years, it is concluded that there are two main reasons for pollution flashover: firstly, objectively, both pollution and moisture factors exist on the surface of insulation components, making it more likely to cause pollution flashover. The second (human factor) is that the creepage distance of the insulator string is too small to adapt to dirty and humid environments.

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