15KV feeder tap in industrial plants

[rondewberry]

A 15KV switchgear breaker feeds 3 unit substations with 500MCM armored cable. I would like to add another 2500KVA unit substation to this feeder. While the 3 unit substations are in the same room, the new 2500KVA unit substation would be 300 feet away. Since this is in an industrial environment, can I use a feeder sized for the load, say 1/0AWG, without protection where the tap is made? The new 2500KVA unit substation would have a 15KV fused switch on the primary side so that the 1/0 feeder tap would not be able to be overloaded.

 

[bob]

Read 240.21.B.4 or 5. This may not be exactly your situation but you can use it as a guide.

 

[charlie]

Read 240.21.B.4 or 5. This may not be exactly your situation but you can use it as a guide.

Bob, I think you may want to use 240.100 and 240.101 since this application exceeds 600 volts.

 

[mxslick]

Ummmm...not familiar with MV switchgear work, but but my gut feeling is that the cost of any failure in the 300 foot feeder would far exceed the cost of adding some fuses or a breaker to that feeder.

Think facility damage, downtime, feeder replacement costs, etc.

Remember just because the Code allows it doesn't mean it's the absolute safest or best way..and at 15kV I would think you'd want absolute safety. :grin:

Just my honest opinion, your mileage may vary.

 

[wireguru]

Ummmm...not familiar with MV switchgear work, but but my gut feeling is that the cost of any failure in the 300 foot feeder would far exceed the cost of adding some fuses or a breaker to that feeder.

Think facility damage, downtime, feeder replacement costs, etc.

Remember just because the Code allows it doesn't mean it's the absolute safest or best way..and at 15kV I would think you'd want absolute safety. :grin:

Just my honest opinion, your mileage may vary.

yeah. remember what happened to the bellagio in vegas a few years ago?

 

[mxslick]

yeah. remember what happened to the bellagio in vegas a few years ago?

Indeed. They had, in order to save a few bucks, run both their main and backup feeders in the same duct bank, through the same vaults, with virtually no physical separation from each other.

A series of miscues caused a fault on the main feeder which destroyed several hundred feet of it. Because the backup feeder was in such close proximity, it had the be shut down during the repairs for safety.

The feeders operate at 12kv.

The total loss to the casino, not counting the repair of the damaged feeder, was in excess of $9 million in lost revenue.

I have printouts of several online reports about this incident, and I imagine one could Google "Bellagio Blackout" to find out more.