THE DEPARTMENT of Mines and Energy’s Mines Inspectorate has issued an official warning on arcing faults causing flash burns and equipment damage.
The warning follows an incident wherein an arc fault inside a 415V electrical enclosure (motor cell) at a coal handling preparation plant caused super-heated gases to be vented from around the edge of the enclosure door, burning an electrician.
The Inspectorate is concerned over arc fault energy released from within an electrical enclosure.
The division says an investigation into the incident showed that the isolator switch handle mechanism had been replaced with a similar unit from a nearby spare cubicle. The original metal plate forming part of this mechanism had a cut-out to ensure clearances were met in relation to the adjacent fuses.
The replacement mechanism did not have this cut-out in the metal plate and clearance distances were severely compromised. When the isolator handle was turned to the “ON” position, a short circuit between one phase and the metal plate resulted in an arcing fault that spread to adjacent phases.
The authority says operators should ensure creepage and clearance distances are adequate in all electrical cubicles to ensure safe operation of energised apparatus.
Additionally, workers should ensure arc flash energy levels are calculated and appropriate measures put in place to limit the extent of arc flash events. This may include reviewing protection system types and tripping times, as well as providing special protective clothing for working in the vicinity of high fault energy apparatus.
Finally, the Inspectorate recommends that operators ensure electrical cubicles have all fasteners in place and that securing the enclosure doors is part of normal maintenance practices.
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