Im in need for some professional advice. We are currently in the process of changing a existing service from 1200 amp to 2000 amp. 120/208 3phase.We have 2 existing 350 kw gen sets, we are removing the existing ATS and providing a new 2000 amp paralleling switchboard our gens have 1200 amp brks our new switchboard has 2- 1200 amp brks what would the tie breaker have to be 2500 amp or would 2000 be adequate. Our main utility switchboard is rated for 2000 amp. Thanks in advance your help is greatly appreciated.
Generator paralleling switchboard
- Thread starter butch
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- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Generator paralleling switchboard
A pair of 350KW generators will give you 1,943 amps, if your load is entirely resistive. But the generator will be rated at a power factor in the range of 0.8 to 0.9. That means the total rated current of the two machines can be as high as 2,429 amps. So the paralleling switchboard would need the 2,500 amp rating. If the only way power gets from the two DGs to the main utility switchboard is via a single tie breaker, and if you want to limit the DGs? output to around 80% of their rating, then I believe you could use a 2000 amp breaker. But that would be a waste of DG capacity. Since you are upgrading your service anyway, have you considered going to a 2,500 amp service?
A pair of 350KW generators will give you 1,943 amps, if your load is entirely resistive. But the generator will be rated at a power factor in the range of 0.8 to 0.9. That means the total rated current of the two machines can be as high as 2,429 amps. So the paralleling switchboard would need the 2,500 amp rating. If the only way power gets from the two DGs to the main utility switchboard is via a single tie breaker, and if you want to limit the DGs? output to around 80% of their rating, then I believe you could use a 2000 amp breaker. But that would be a waste of DG capacity. Since you are upgrading your service anyway, have you considered going to a 2,500 amp service?
Re: Generator paralleling switchboard
Regarding "paralleling switchboard," I trust that you have things covered in providing a means to assure that went the generators are placed in parallel that it is done so in phase with the normal source. Magical things can happen if you try to bring the sources together that are out of phase with the another. This problem also exist when applying contactor and power breaker transfer techniques with no time delay neutral during a transfer from a normal source to the emergency.
Regarding "paralleling switchboard," I trust that you have things covered in providing a means to assure that went the generators are placed in parallel that it is done so in phase with the normal source. Magical things can happen if you try to bring the sources together that are out of phase with the another. This problem also exist when applying contactor and power breaker transfer techniques with no time delay neutral during a transfer from a normal source to the emergency.
Re: Generator paralleling switchboard
Phasing is a mechanical connection procedure. The units, once in proper rotation, will remain in that state.
Paralling generators is done by syncronizing the sign wave of the incoming unit to the main buss. The time and intensity must match before closing on line.
Phasing is a mechanical connection procedure. The units, once in proper rotation, will remain in that state.
Paralling generators is done by syncronizing the sign wave of the incoming unit to the main buss. The time and intensity must match before closing on line.
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