New 4160v temporary generator

[Mila2015]

Client had asked if we could add a temporary 4160v generator to feed their 4160v lineup. This would be connected directly to the MV bus (there is no available CB for this connection). I have the following questions:

• What would be an advantage of using 480v generator Vs 4160v?
• What generator protection needed, and where can this be installed? Would that be part of generator assembly?
• What are the possible risks associated with that?

Thanks for your help!

 

[crshears]

Using a 480V generator has the disadvantage that a 480>4160 step-up trafo will be needed.

Obviously a temporary CB [and possibly a series disconnect switch] will be needed to provide a disconnection point for the generator.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

(there is no available CB for this connection)
Client had asked if we could add a temporary 4160v generator to feed their 4160v lineup.

With that constraint, the quick answer is no.
If you find a breaker you will need synchronizing gear.
You have not stated the required capacity. In the smaller sizes a 480 Volt generator will be off the shelf while a 4160 Volt generator may be a special order.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Temporary breaker electrically interlocked with normal supply so transfers are always break before make? [Presuming the customer's load can sustain a brief interruption...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Mila2015]

waross, thanks for reply. The load is around 1700 KW. The generator will connect to a dead bus, so no need to synchronize. I just learned the client wants to connect to MV bus using existing MV 400A contactor feed. Someone mentioned we can't use these contactors in reverse, is that correct? If a contactor can be used, what modifications are needed? I would assume we would need to replace the relay to generator protection.

 

[waross]

You get what you pay for. You can get a complete protection package with the generator.
Check the difference between a standby rated set and a prime power set.
A 2000 KVA standby set will be rated as an 1800 KVA prime power set.
As well as de-rating, the prime power set MAY have a larger oil sump, an oil cooler (not always supplied with smaller standby sets) and possibly other engine accessories to facilitate the much greater hours in the lifetime of a prime power set as opposed to a standby set.
A prime rated set is allowed a 10% overload for a percentage of it's running time.
A standby set does not allow any overload.
Backfeeding the breaker.- Check with the manufacturer. You may have to modify the control circuit.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

I think that the issue with using a contactor as the isolation and protection device may be that with a contactor, it usually must be coordinated with a fuse and will thereby have a disconnect, and often the disconnect will not be "load - break". The fuse then ends up on the wrong side of the contactor with respect to the generator so when running the generator, if a fuse blows, opening the disconnect will NOT kill power to the fuse holder and someone could get killed.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[catserveng]

When you say "temporary", how long are you talking about?

Are you buying equipment or looking at renting/leasing?

For the size range you're looking at a 2MW package rental set at 480 with a step up transformer and a MV fused disconnect would be what would be installed by most suppliers of temp power, such as Aggreko or CAT. Most package sets that size have an on board 480 breaker, basic paralleling controls and generator protections. Even though you plan on only connecting to a "dead" bus, you will need (and possibly be required depending on where you are) some form of protection to assure you cannot parallel to the grid, except in some cases for a closed transition transfer.

Your best bet may be to contact a company that does temporary power systems in the size range you need.

Hope that helps, MikeL.

 

[Mila2015]

Jraef, I see your point. I'm assuming in the case of needing to work on fuse, they could shutdown all bus loads, the generator, and open the contactor. This would kill power to the fuse holder....am I missing anything?

catserveng, this might be something I should consider.