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 Post subject: MV Switchgear Cable Compartment
PostPosted: Fri Dec 17, 2010 3:10 pm 
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Joined: Wed Jun 04, 2008 9:17 am
Posts: 409
Location: Spartanburg, South Carolina
Should the cable termination compartment of MV metal clad switchgear be treated as switchgear or cable?

Switchgear would have a gap of 153 mm, a typical working distance of 910 mm, and a distance factor of 0.973 (in a box).

Cable would have a gap of 13 mm, a typical working distance of 455 mm, and a distance factor of 2.000 (open).

Examples:

12.47 kV, 14.125 kA bolted fault, clearing time on line side of incomer = 1.656 sec. IE as switchgear = 29.8 cal/cm┬▓. Arc flash boundary as switchgear = 973". IE as cable = 32.2 cal/cm┬▓. Arc flash boundary as switchgear = 93".

12.47 kV, 14.125 kA bolted fault, clearing time on line side of feeder = 0.694sec. IE as switchgear = 12.5 cal/cm┬▓. Arc flash boundary as switchgear = 398". IE as cable = 13.5 cal/cm┬▓. Arc flash boundary as switchgear = 60".

It seems that the shorter working distance is appropriate. If you are going to be measuring voltage on the cables, you will be closer than 910 mm. The smaller distance factor seems more appropriate though because the terminations are enclosed.

Maybe treating it as switchgear, but changing the working distance to 455 mm would be correct. This would result in an IE=58.5 for the line side of the example incomer.


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