Metal Clad switchgear question

[dpmac]

I was asked a question today. I thought I knew the answer and replied as best I could. I wanted back up and have been looking for that back up all day. The question involves new standard 15kV Metal-Clad vacuum switchgear manufactured in the US.

"When landing properly terminated 15kV cables on bus is the installer/contractor required to insulate the connections using boots, tape or other method."

Assuming this new 15kV Metal Clad bus is insulated (sleeved, fluidized bed, shrink, etc) per ANSI and meets all the criteria pertaining to AC withstand, BIL, etc. Logic tells me un-insulated terminal connections can't possibly meet the same criteria. I just can't seem to find written documentation to back it up.

Please assume no written documentation, direction or input is available from the manufacturer.

Any insight as to where I can obtain information on this would be appreciated.

Thanks

 

[RajT]

The question appears to relate to adding of stress kits to cable terminations.
If so then it is standard universal practice to fit stress relieving kits ( hot or cold shrink) within the switchgear cable box to ensure that the small section of the cable which has had its armour stripped does not have a charge buildup over a period and thus degrade the insulation prematurely.

 

[dpmac]

Thank you for the reply RajT.

The question does not relate to the cable terminations themselves but to the point where the (properly terminated) cable is actually bolted to the switchgear load side bus.

Is taping, boots or other insulation required at the point where the cables are connected to the bus?

My thought process is that Metal Clad switchgear bus is fully insulated. Clearances between phases and phase to ground are reduced due to this bus insulation. These exact same clearances are found at the point of cable connections. If left un-insulated after the cables are connected how could the switchgear still maintain the same AC withstand, BIL, etc ratings?

 

[arcflash99]

We have both taped (insulated) and untaped (bare connections)terminations in different manufacturer's switchgear. We just installed a 15kV distribution substation earlier this year and the manufacturer's instructions were to use boots to prevent any flashover. The terminations seem closer to each other in today's switchgear than they were 25+ years ago.

Our stadard practice is tape/ boot with grounding studs with covers. That way you maintain insulation and still have a safe way to test for voltage and properly ground.

Hope this helps.

 

[RajT]

There is no requirement ( as far as standards are concerned) to insulate the said small sections of copperwork within the cable box.
However many engs specify such requirement as described by arcflesh99.A good practice as it does enhance safety.