Six Transformers

[mickeyrench]

My company has a service almost like the one in the previous post .We have six transformers being feed from the same pole .The transformers labeled abc and abc. They are feeding the switch gear square d zone111 main breaker with 10 sub breakers with a tie panel and than an exact copy main breaker and the 10 sub breakers. One side main cb is closed with a kirk key in the lock the other side is open and no key in the lock. I don't understand why the 2 sets of transformers being feed from the same pole. What is the benifit of this setup? The only thing i see is if the transformer goes they can switch over to the other side. Can some one tell me why this is done. Also there is a bu generator for service.

 

[gobblerhuntr]

My company has a service almost like the one in the previous post .We have six transformers being feed from the same pole .The transformers labeled abc and abc. They are feeding the switch gear square d zone111 main breaker with 10 sub breakers with a tie panel and than an exact copy main breaker and the 10 sub breakers. One side main cb is closed with a kirk key in the lock the other side is open and no key in the lock. I don't understand why the 2 sets of transformers being feed from the same pole. What is the benifit of this setup? The only thing i see is if the transformer goes they can switch over to the other side. Can some one tell me why this is done. Also there is a bu generator for service.

We have several 6 six transformer set ups on our utility system. Some are because the customer added on to an existing service, others where designed that way from day one with parallel high sides. Sounds like in your case someone was looking for a redundant system. With the gen set it looks as if it would be redundant anyway, but we don't know which came first.

 

[weressl]

My company has a service almost like the one in the previous post .We have six transformers being feed from the same pole .The transformers labeled abc and abc. They are feeding the switch gear square d zone111 main breaker with 10 sub breakers with a tie panel and than an exact copy main breaker and the 10 sub breakers. One side main cb is closed with a kirk key in the lock the other side is open and no key in the lock. I don't understand why the 2 sets of transformers being feed from the same pole. What is the benifit of this setup? The only thing i see is if the transformer goes they can switch over to the other side. Can some one tell me why this is done. Also there is a bu generator for service.

So you have two sets of single phase transformers connected to form two three phase service?

Not stated, but I presume that each transformer set is connected to one of the Square D Switchegar main. I also presume that the tie 'panel' is a closed, fully rated breaker between the two switchgears. Somewhat surprised that you don't mention a key interlock at the tie. (I suspect that you may have and interloack there with a key in it. Three locks, two keys.)

Being fed from the same 'pole' does not necessarily mean the transformers are connected to the same feeder on the primary side.

The two transformers are obviously backing each other up in case of failure. If that would be the only concern, there would be only an interlocked set of secondary breakers feeding a single line-up switchgear. Since you have two independent swicthegar line-up connected with a tie breaker it is likely that each feeds equipment that are either

• duplicates of each other so if one is shut down the other one can provide continuous service,
• each switchgear feeds an independent plant, so the shutdown of one does not effect the other,

So not only your transfomrers are backed up but your switchgear and other downstream equipment.

Normally this setup would be operated with the tie-breaker open and both trasnformers on-line and a tie breaker interlock.