Insulator external insulation refers to the air gap insulation and the surface insulation of insulators exposed to the atmosphere. The withstanding voltage of external insulation is closely related to atmospheric conditions. Air gap breakdown and surface flashover are the manifestations of loss of insulation performance of external insulation. Generally speaking, after breakdown or flashover, the insulation performance of air can be automatically restored, which belongs to self-restoring insulation.
Insulator internal insulation refers to the insulation that does not contact with the atmosphere directly, and its withstanding voltage value has nothing to do with the atmospheric conditions. Internal insulation can be composed of solid, liquid, gas or a combination of various media. Once the internal insulation breaks down, it can not be automatically restored. It belongs to non-self-restoring insulation.
After the self-restoring insulation is damaged under the action of applied voltage, the insulation performance can automatically restore to the previous level. This kind of insulation is called self-restoring insulation. Generally speaking, external insulation belongs to self-restoring insulation, but there are also exceptions.
Non-self-restoring insulation, which is called non-self-restoring insulation, loses its insulation performance or can not completely restore to the previous insulation level after insulation breakdown under the action of applied voltage. Generally speaking, internal insulation belongs to non-self-restoring insulation, but there are also exceptions.
Breakdown of destructive discharges in solid dielectrics usually results in permanent damage to dielectric insulation.
Under the action of applied voltage, the flashover occurs between two electrodes at different potentials and along the interface between solid dielectrics and atmosphere. Sufficiently strong ionization can occur in the flashover channel to generate an arc. The standard lightning wave amplitude with 90% tolerance probability (10% discharge probability) can be obtained by applying standard lightning shock wave to self-restoring insulation at basic lightning impulse insulation level under specific conditions. The amplitude of standard operating shock wave with 90% probability of tolerance (10% probability of discharge) is obtained by applying standard operating shock wave to self-restoring insulation at basic operating shock insulation level under specific conditions.
The shortest discharge distance between the two end electrodes through the intermediate medium, or the shortest discharge distance through several intermediate electrodes. Connection length The linear distance between the conductor and the supporting structure, including the insulation distance and the length of the metal fittings at both ends.
The sum of the shortest distance measured along the insulating surface between conductive components. The protected leakage distance is the leakage distance of the insulating surface which is not directly affected by natural factors such as sunshine, wind and rain. For suspended ceramic insulators and glass insulators, the protected leakage distance refers to the leakage distance along the groove on the lower surface of insulators.
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