These days, electricity supply companies have become highly focused on the safety of their personnel who work in the vicinity of equipment whose failure can pose a safety risk. One of these requirements in the medium voltage field is protecting staff from the effects of a possible internal arc fault in switchgear. While the probability of such an event is very low, the risk is not zero and therefore occurrence of an internal arc fault has to be considered.
The main causes of internal arc include:
• operational & maintenance faults;
• intrusion by animals;
• insulating fluid leakage or loss of vacuum;
• dielectric faults of solid insulation materials (e.g. cable termination, damaged cable sheath, cracked epoxy, aged insulation);
• improper operation of the device.
The result of internal arc is release of tremendous heat and massive gas pressure inside the medium voltage cubicle.
Among the most effective solutions to avoid risk to personnel standing in front of or at the sides of cubicles is to ensure that the structure is strong enough to withhold the gas pressure. Moreover, release of the hot gas and flames should be through self-operating flaps that channel these via exhaust tunnels away from operators who must also be protected against fragmentation of the enclosure. Given the above, key features of MV switchgear that is ‘internal arc proof’ include structural strength as well as specific gas exhaust paths.
Attend the 2022 INMR WORLD CONGRESS in Berlin, where MV switchgear expert, Mayur Panchal, will give a lecture that explains the relevant testing procedure as well as all its various elements, including set-up, type of accessibility, evaluation criteria and additional requirements as per the latest edition of IEC 62271-200; Ed.3; 2021.