Why insulation can be breakdown?

1. The existence of air gaps in the main insulation will cause partial discharges. Since the relative permittivity of the air gap is much smaller than that of the cable insulation, under the action of the power frequency electric field, the air gap has to withstand a large electric field intensity, and there are tens of millions of partial discharges. The discharge is gradually increased until a breakdown occurs, causing damage to the cable.
2. The presence of impurities in the main insulation causes partial discharge. The breakdown strength of impurities is much smaller than that of insulating materials. Under the action of the electric field, the impurities first discharge, carbonize and gasify, forming air gaps and causing partial discharges.
3. The tip and burr of the conductor will cause partial discharge. Because the tip will increase the electric field strength, the insulating material around the tip will discharge first, and then develop into a breakdown, which is what we often call the tip effect.
This is the basic factor of insulation breakdown of flexible cables. In the laying and use of cables, we must pay more attention. Once insulation breakdown is found, you can refer to some of the above factors to find out the problem as soon as possible.