Switchgear Arc Resistant Faults

Internal arc fault test IAC AFLR 31.5kA/1s, 40kA/1s, and even 50kA/1s, although the risk of arc test is high, there are very many uncertainties, but not through any “special treatment”, through the test is not impossible to pass, the key is that the design of the product must be in full accordance with the internal arc requirements, fine-tuning every detail of the production of quality and quantity, you can ensure that each switchgear can pass the test without worrying about any random inspection. The key is that the product design must be completely in accordance with the requirements of the internal arc, refine every detail, quality and quantity production of products, you can ensure that each switchgear can pass the test, without having to worry about any sampling.

Resistant to internal arc fault design, be sure to maintain a relatively sealed, cabinet and door, cover often have gaps between these gaps may meet the IP4X, that is, not greater than 1 mm requirements, but the cover door in the internal arc fault instantaneous explosion of the shockwave impact, instantly will make the gap expand more than 10 times. This makes it easy for the flame to spray out. So try to stick flat, door cover bolt spacing should not be greater than 150mm, using internal and external overlap, labyrinth type design of the cover can be appropriately increased to 200mm.


The real realization of switchgear arc resistance, the need to close the door, door bolts tightened to play the function of anti-internal arc, and just lock one or two bolts is useless, internal arc fault occurs, the pressure reaches a few megapascals, one or two bolts instantly will be washed out. Some customers require the use of bolt locks need to be provided to ensure that all door locks must be locked design, such as the provision of micro-switch, all bolts tightened in place, the micro-switch action before the circuit breaker can be closed.

The same for the single-handle quick-open door locking mechanism, the first lock bolt design to withstand internal arc fault, the number of strength to be enough, some of the use of a simple few fine hooks hanging door, simply can not withstand the internal arc when the shockwave pressure; single-handle door locks to ensure that the shut-off in place, the locking hooks should be locked into place, if the lock is half easily flushed open, the same requirements of foreign projects door lock microswitch The door locking microswitch is also required for foreign projects, and the circuit breaker can only be closed after the door lock is locked in place to ensure safety.

Pressure can only be released as quickly as possible to minimize damage to the switchgear. Pressure release path to minimize obstruction, such as lifting the current transformer, blocking the cable room pressure relief, the current transformer is installed behind, successfully avoiding the pressure relief channel, thus ensuring rapid release.

Switchgear internal arc fault caused by the thermal effect is equally important, so the need for switchgear internal insulating parts to meet the requirements of the V0 class flame retardant, that is, after the disappearance of the ignition source, it will not continue to burn, and often the switchgear through the 1-second internal arc test continues to burn, the need for the fire department to extinguish the fire.

Some manufacturers in order to pass the test, the use of arc-inducing plate and other designs, theoretically arc-inducing plate to be consistent with the actual product, such as as the cable bracket as a fixed plate, or the reinforcement of the bulkhead, etc., this arc-inducing plate must be through the corresponding frequency, impact voltage test, that is, does not affect the normal operation of the insulation properties.

For the installation of cited arc board to do the test, really play a role in the test is very little, this is because the arc test is very complex, the arc is a very light quality plasma, the electric field situation is complex, will not be in accordance with our imagination.

Really play a role in the phase and ground insulation, through the heat shrink tubing and ground insulation partition, can quickly extinguish the arc, to prevent the arc distance to elongate, increase the energy, thereby increasing the destructive force, resulting in failure of the test.

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