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2 power sources in parallel? 2

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Visitor1

Electrical
Nov 1, 2002
1
My problem is if is possible to connect 2 different power sources in parallel on the same busbar in a switchgear and wich is the requirements to do this?
One power source is an utility power feeder and the second will be an 600Kw, 480V generator.
We have some maintenance work to do at the utility feeder and our customer will not agree a shutdown.
We don't talk about UPS or ATS, just if is possible to connect the generator on the hot busbar (through a CB).
Thanks.
 
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What about a short glitch at switchover ? A few seconds
drop-out ? What is the nature of the customer's equipment ?
<nbucska@pcperipherals.com>
 
You have three options:
1-Using Automatic Transfet Switch (ATS)
2-Using Manual Transfer Switch (MTS)
3-Using Dual Breaker Service Entrance Transfer Switch

I think you are looking for option 3 above. This transfer switch is simply made of two parallel interlocked breakers.

Thomson Technolgy makes some of these types of products.


[thumbsup]
 
I forgot to mention that two separate unsynchronized sources can not be connected on the same bus.

[pipe]
 
hi..
how about the possibility of renting a &quot;static switch&quot; while you are doing the repair....sync the genset and the utility for a changeover...

i am not to sure though if there is a commercially available static switch of that size..

dydt
 
Except for possible short circuit limitations, there is no reason that the generator cannot be paralleled to the bus with the utility source. It will take synchronizing equipment to put the generator on and to resynchronize the utility source when the work is complete, but this can be accomplished although at some expense.

Short circuit levels could be a problem and should be checked. However, if the paralleling is only for a very short time during a tranfer operation, that is generally acceptable.

The only other usual problem is getting the utility's permission to do the paralleling, but it sounds like you are the utility so that shouldn't be an issue.
Make sure you do your homework and get someone to look at the details. This is not difficult, but if not done right can result in some significant equipment damage.
 
dy/dt,

I believe companies like Liebert or Cyberex make static switches up to 2000A, more than enough...


Mike
 
The cheapest option is to run up the gen and then do a fast manual transfer (break before make)of incoming supply from the utility incomer to the gen incomer. One could agree a date/time in advance with the consumer so that he will be aware of the outage for a second or two which should be acceptable noting that under normal circumstances, you could loose the utility incomer due to a upstream fault anyway as it often happens.
Static switches have a place in application but would not recommend it in your case.
Installing synchronising equipment gives more versatility and choice at a price.
 
Suggestion: Please, could you provide more information regarding:
1. Is the generator installed or will it brought in, e.g. mobile?
2. If the generator is installed, is there any need to adhere to Safety Codes, e.g. NFPA 70-2002, NFPA 110-1999 for automatic transfer to critical and/or life safety loads?
3. If 2. does not apply, then consider some of the above posting regarding synchronization, to avoid any downtime.
4. If a short downtime is tolerable, then first open or disconnect the Utility feeder, have the Utility to deenergize the feeder first to have the feeder for your work deenergized, and power the bus from the generator.
 
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