IEEE has dedicated standards in Arc-flash hazard mitigation and protection (IEEE 1584 & NFPA 70E) while IEC has integrated its arc-flash protection into the IEC 62271-200, High-voltage switchgear and controlgear - Part 200: AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV.
IEC 62271-200 recommends metal-enclosed switchgears and controlgears that satisfy the requirements of this standard to prevent the occurrence of internal faults. Proper selection shall be in accordance to the characteristics of the network, operating procedures and service conditions. The selection of a metal-enclosed switchgear and controlgear to prevent the possibility of the occurrence of internal faults should aim of providing an acceptable protection level for operators and, where applicable, for the general public.
According to IEC 62271-200, if the switchgear and controlgear is installed, operated and maintained following the instructions of the manufacturer, there should be little probability that an internal arc occurs during its entire service life, but it cannot be completely disregarded. Failure within the enclosure of metal-enclosed switchgear and controlgear due either to a defect or an exceptional service condition or mal-operation may initiate an internal arc, which constitutes a hazard, if persons are present.
Other measures may be adopted to provide the highest possible level of protection to persons in case of an internal arc. These measures are aimed to limit the external consequences of such an event.
The following are some examples of these measures.
- Rapid fault-clearance times initiated by detectors sensitive to light, pressure or heat or by a differential busbar protection.
- Application of suitable fuses in combination with switching devices to limit the let-through current and fault duration.
- Fast elimination of arc by diverting it to metallic short circuit by means of fast sensing and fast closing devices (arc eliminator).
- Remote control.
- Pressure relief device.
- Transfer of a withdrawable part to or from the service position only when the front door is closed.
As a summary for the selection of the adequate switchgear and controlgear with respect to internal arcs, the following criteria may be used:
- where the risk is considered negligible, metal-enclosed switchgear and controlgear is not necessary
- where the risk is considered to be relevant, only metal-enclosed switchgear and controtgear should be used
As arc-flash hazard protection is integrated into IEC 62271-200 which deals only with AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV, then for voltages below 1kV, arc-flash hazard protection requirements, therefore, is not mandatory.
This is in contrast with IEEE 1584 which requires arc-flash hazard analysis down to 240V.
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