In the wire and cable industry, we can often hear the word "insulation breakdown", and it occurs more in the use of power cable. So what does the meaning of insulation breakdown of power cable mean? The cable of the electrical complete equipment manufacturer tells you:

首先要明白，放电是发生电力电缆绝缘击穿的原因

First, it should be understood that discharge is the reason for the insulation breakdown of power cable

放电指的是在两个有电位差的导体之间，当绝缘材料性能下降，两个导体间产生了电子能量的迁移，比如高压火线与地线间的打火就是放电，完全的放电是放电的瞬时有两个电极间形成了完整的电弧通道。

Discharge refers to the transfer of electronic energy between two conductors when the performance of insulation materials decreases. For example, the ignition between high voltage wire and ground wire is discharge. Complete discharge means that the complete arc channel is formed between two electrodes in the instantaneous discharge.

除了以上所说的放电情况外，还有放电的特殊情况——局部放电

In addition to the above mentioned discharge, there are also special discharge cases - partial discharge

局部放电主要有两种情况

There are two main cases of partial discharge

1.在两个导体之间有绝缘，当绝缘材料内部有缺陷，如杂质、空隙、导体的尖 端等，会成绝缘内部电场歧变，引起在绝缘内部产生脉冲放电。

1. there is insulation between two conductors. When there is defect in the insulation material, such as impurities, voids, tip of conductor, etc., the electric field will be differentiated inside the insulation, which will cause pulse discharge in the insulation.

2.外部放电产生电晕也是局部放电的一种，在高电位与接地之间有空气绝缘，当导体周围的电场在某一点特别集中时，如导线毛刺，引起在空气中产生脉冲放电，且没有形成对地短路，形成电晕。

2. corona generated by external discharge is also a kind of partial discharge. Air insulation is provided between high potential and grounding. When the electric field around the conductor is specially concentrated at a certain point, such as the burr of the conductor, pulse discharge is generated in the air, and no short circuit to ground is formed to form corona.

局部放电的特征

Characteristics of partial discharge

局部放电也具有放电的基本特征，即有电子能量的迁移，由于放电能量较小，又有绝缘材料的阻挡，在两个电极间不一定形成完整的电弧通道，此类通道一旦出现就会加剧局部放电，直到形成两极绝贯通，就会发生短路放电故障。

Partial discharge also has the basic characteristics of discharge, that is, the transfer of electronic energy. Because of the small discharge energy and the barrier of insulating materials, there is no complete arc channel between the two electrodes. Once such channels appear, the partial discharge will be intensified, and the short circuit discharge fault will occur until the two poles are completely connected.

局部放电形成的原因

The cause of partial discharge

主绝缘内存在气隙会引起局部放电。由于气隙的相对介电常数远小于电缆绝缘，在工频电场作用下，气隙要承受较大的电场强度，千万局部放电，随着气隙的多次放电，气隙通路不断扩大，放电量逐渐增加，直至发生击穿，造成电缆损坏。

The air gap in the main insulation will cause partial discharge. Because the relative dielectric constant of air gap is far less than cable insulation, under the action of power frequency electric field, the air gap should bear a large electric field intensity. Tens of millions of partial discharge, with the multiple discharge of air gap, the air gap path is expanding, and the discharge amount gradually increases until breakdown occurs, which causes cable damage.

主绝缘内存在杂质引起局部放电。杂质的击穿强度比绝缘材料小的多，在电场作用下，杂质首先发生放电、炭化和气化，生成气隙，引起局部放电。

The impurity in the main insulation causes partial discharge. The breakdown strength of impurities is much smaller than that of insulating materials. Under the action of electric field, the impurities first discharge, carbonize and gasify, and generate air gap, which leads to partial discharge.

导体的尖 端、毛刺会引起局部放电。由于尖 端会使电场强度增加，尖 端周围的绝缘材料先发生放电，进而发展成击穿，这就是我们常说的尖 端效应。

The tip and burr of conductor can cause partial discharge. Because the tip increases the electric field strength, the insulation around the tip first discharges and then develops into breakdown, which is what we often call the tip effect.

以上就是引起电力电缆绝缘击穿的一些因素，在电缆的敷设使用中，一定要多加注意，一旦发现绝缘击穿，可以参考以上的一些因素尽早找出问题所在。

Above are some factors that cause insulation breakdown of power cable. In the laying and use of cables, more attention should be paid to. If insulation breakdown is found, we can refer to the above factors to find out the problem as soon as possible.