KarlS
Member
- Location
- Houston, TX
THe NEC forum may not be the correct place for this quesition but here it goes. I have installed (3) 15KV bushings on top of a metal building. THese bushings connect to the 15KV swgr inside by (2) per phase 500MCM shielded cables (MV-105). The run is short maybe 10ft. The SWGR is new Eaton arc resistant type. My drawings instructed the shop to install a 1/4" alum plate on top of the swgr and cut holes for the (3) bushings due to the megnetic induced heat effect of installing cables AA-BB-CC. I had no room in the chase with the stress cones for ABC-ABC.
You guessed it! They did not install the alum plate as instructed. The stress cones will not allow the cables to be pulled back thru the 3" bushngs. Now for Plan B. I know you must install alum or Glastic to stop the heating of the metal swgr top cover or plan B you can cut a slice from bushing to bushing in the metal to stop the effect. The system is rated for 1200A.
Has anyone installed cables like this and if so, how wide should the gab be that I intend to cut? I am thinking 1/2" to stop the circulating currents inducted in the swgr top cover.
My experiance is based on 16yrs as a MV swgr manufacture running cables within gear for custom applications. That however was several yrs ago and wanted to see what other exterior cable installers have done.
Thanks and look forward to your responses.
You guessed it! They did not install the alum plate as instructed. The stress cones will not allow the cables to be pulled back thru the 3" bushngs. Now for Plan B. I know you must install alum or Glastic to stop the heating of the metal swgr top cover or plan B you can cut a slice from bushing to bushing in the metal to stop the effect. The system is rated for 1200A.
Has anyone installed cables like this and if so, how wide should the gab be that I intend to cut? I am thinking 1/2" to stop the circulating currents inducted in the swgr top cover.
My experiance is based on 16yrs as a MV swgr manufacture running cables within gear for custom applications. That however was several yrs ago and wanted to see what other exterior cable installers have done.
Thanks and look forward to your responses.