Insulator flash cause analysis

1. Pollution flash

Ordinary insulators attached to the insulators do not conduct electricity under dry conditions and the insulators will be washed away. However, in areas with more serious environmental pollution, near the source of pollution, chemical raw materials in the air, chemical substances diffused near the factory, such as carbon powder, cement powder, acid, alkalinity, gold properties, etc., are attached to the insulator for a long time to form caking. Strong adhesion, not easy to be cleaned by rain, residual surface, in the face of drizzle, fog, dew and other weather, the insulator surface attached to this part of the dirt will be wet, the conductivity is greatly improved, resulting in an increase in leakage current. When the electric field of the leakage current is strong enough to cause collision ionization of the surface air, a corona discharge or glow discharge immediately begins around the iron cap, resulting in a thin blue-purple line due to the large leakage current at this time. A corona or glow discharge can be easily converted into a bright channel arc. In fog and dew weather, the humidity of the dirt layer increases, the leakage current increases, and the local length can be maintained under certain electrical conditions. Once the local arc reaches a certain critical length and the arc channel temperature is high, further elongation of the arc channel no longer requires higher voltage and automatically extends through both stages, resulting in insulator discharge flashover.

2.Fog (wet) flash cause analysis

In the fog (wet) weather for a long time, the surface of the ceramic insulator gradually forms a layer of water film. Due to the loss of hydrophobic properties of composite insulators and the uneven distribution of field strength, the surface of composite insulators will also form a water film. At the same time, the surface of the insulator is covered with impurities, and the composition of the fog water is complex. Corona and partial arc discharge are formed at the end of the insulator. Due to the increase of air humidity, the field strength of air breakdown will be significantly reduced. Due to the breakdown of the arc between the porcelain skirts at the end of the insulator, once the first skirt is destroyed, the second skirt will produce a higher voltage, repeat the process just now, because when the AC voltage exceeds zero, the arc will be extinguished, so in this case, when the AC voltage exceeds zero, the arc will be extinguished. Whether the insulator flashover can be generated depends on the development of the arc and the flow of ionized air. If the fog (humidity) is relatively stable and the arc reignites, it may flash quickly, whereas if the air flows faster, the ionization channel will disappear quickly and will not evolve into a flashover.

3. Cause analysis of icing flash

It is mainly determined by meteorological conditions, and is a comprehensive physical phenomenon determined by factors such as temperature, humidity, cold and warm air convection, environment and wind speed. Small supercooled water droplets are difficult to change structure because of their small diameter and large surface tension. It is also difficult to touch the condensed dust, although the temperature is below zero degrees Celsius, but still at the rate of decline, slowly falling to the ground, forming a "freezing rain". This supercooled water is very unstable. When the droplet is in contact with a cooler object on the ground (such as an insulator), the deformation of the supercooled droplet will be caused by collision vibration, and the surface bending degree of the droplet will be reduced, and the surface tension will be correspondingly reduced. The condensation effect of the surface of the insulator is similar to that of the nodule. After deformation, the liquid supercooled water drops attach, so that the cooling water droplets condense on the surface of the insulator into a ribbed or ribbed ice sheet, so that the surface of the insulator is covered on the surface of the insulator in the form of RIM or RIM. This reduces the insulation capacity of the insulator, resulting in flashover of the insulator.