Cause and characteristic analysis of glass insulator self-explosion

The reasons for the self-explosion of glass insulators can be divided into two categories: product quality reasons and external operating environment reasons, and actual cases often have two reasons at the same time.

① Product quality reasons

Mainly the glass insulator glass parts contain impurities particles, the common is NIS particles. The phase change state of NIS is not complete in the process of melting and annealing of glass parts. After the insulator is put into operation, it is believed that the phase change and expansion occur slowly, resulting in cracks inside the glass. When the diameter of the particle impurities is less than a certain value, it may not be able to be removed by cold and thermal shock, resulting in high self-detonation rate of the insulator in operation. When the impurity particles are located in the internal tensile stress layer of the glass, the probability of self-explosion is higher, because the glass itself is a brittle material, which is resistant to pressure but not tensile, so most of the broken glass is caused by tensile stress.

Features:

1、The self-detonation caused by internal impurity particles is higher in the first three years of operation, and will gradually decline thereafter, which is an important law for judging the cause of self-detonation.

2、The self-explosion probability of different positions of the insulator string is the same;

② External causes

Mainly pollution and temperature change. Under the simultaneous action of pollution, moisture and electric field, the leakage current on the insulator surface is too large, resulting in part of the dry belt. When the air breakdown occurs in the dry belt, the generated arc will erode the glass umbrella skirt, and when the corrosion depth is deep, it will cause self-explosion. If the insulator is struck by lightning during the above process, the probability of self-explosion of the glass insulator that has been eroded by the arc will be greatly increased. Excessive pollution is the key, which may be too high salt density, or too many metal powder particles in the pollution.

Features:

1、Self-detonation may not be obvious a few years before the operation, and it may occur at a certain time after several years of operation (major changes in local sewage sources cause excessive pollution);

2、The probability of self-explosion at the high pressure end and low pressure end of the b insulator string is greater than that in the middle (the electric field at the high pressure end and low pressure end is stronger, and local creepage occurs at the steel foot of the insulator first when the pollution is too heavy);

3、The steel foot of the non-self-detonating insulator of the same tower is damaged (local arc caused by excessive pollution causes damage to the glass near the steel foot), and there are minor cracks inside the umbrella surface;