Generator rated for 13.2KV serving 12.47KV System

[faresos]

I went to a job site and found a standby generator name plate reads 2000KW & 13200V. However, the building utility is served from 12.47KV. is it possible to adjust the voltage system on the generator to deliver 12.47KV? Is there any reason why they didn't purchase generator rated for 12.47KV to start with?

Thanks,

 

[templdl]

I went to a job site and found a standby generator name plate reads 2000KW & 13200V. However, the building utility is served from 12.47KV. is it possible to adjust the voltage system on the generator to deliver 12.47KV? Is there any reason why they didn't purchase generator rated for 12.47KV to start with?

Thanks,

Excellent question that should be directed to those who were responsible for purchasing the genset.
Is the genset feeding a step down transformer such a with a 480y/277 or 208y/120 secondary for example? If so what primary taps are available on the transformer?

 

[faresos]

The generator is feeding a substation with step down transformers (12.47KV- 480/277V) and I'm not sure what is the tapping on the transformers primary. It appears there approximately 6% voltage different between the 12.47 & 13.2KV but not sure if the manufacturer have modified the unit to produce 12.47KV but forgot to change the name plate.

 

[Bugman1400]

The generator is feeding a substation with step down transformers (12.47KV- 480/277V) and I'm not sure what is the tapping on the transformers primary. It appears there approximately 6% voltage different between the 12.47 & 13.2KV but not sure if the manufacturer have modified the unit to produce 12.47KV but forgot to change the name plate.

I believe most gens are rated higher than the operating voltage to compensate for droop under full output and load.

 

[iceworm]

I went to a job site and found a standby generator name plate reads 2000KW & 13200V. However, the building utility is served from 12.47KV. (Q1) is it possible to adjust the voltage system on the generator to deliver 12.47KV? (Q2)Is there any reason why they didn't purchase generator rated for 12.47KV to start with? ...

Q2: Generally it is about the money. And specifically it is about the money.:roll:

Look at the dates the equipment was purchased.

Modern distribution will be 13.8 KV - that matches with 480V. Older systems, say 1960s and older will be 13.2KV - that matches with 440V.

12.47 is a bit odd any more. Anecdotal information (no reference) suggests it was driven by REA. 12.46kv/7200V was compatible with the single phase rural services.

Q1: Sure. Have to watch low end leading vars, minimum excitation level, stability, power output will not make nameplate. Might take an exciter change - might not.

ice

 

[templdl]

The generator is feeding a substation with step down transformers (12.47KV- 480/277V) and I'm not sure what is the tapping on the transformers primary. It appears there approximately 6% voltage different between the 12.47 & 13.2KV but not sure if the manufacturer have modified the unit to produce 12.47KV but forgot to change the name plate.

Do you know what the name plate of tthe transformer is or better yet casn to post a picture of it? It is very likely that the transformer has +(2)2-1/5 % FCAN and either (2) or (4) -2-1/2% FCBN taps which you could use the -5% below normal tap which should bring the secondary voltage back up where it should be. If you have the -(4) you you have an additional (2) 2-1/2% taps.

 

[topgone]

Do you know what the name plate of tthe transformer is or better yet casn to post a picture of it? It is very likely that the transformer has +(2)2-1/5 % FCAN and either (2) or (4) -2-1/2% FCBN taps which you could use the -5% below normal tap which should bring the secondary voltage back up where it should be. If you have the -(4) you you have an additional (2) 2-1/2% taps.

Very good points! 13.2 kV with a -5% tap will be 12.54 kV!

 

[faresos]

Do you know what the name plate of tthe transformer is or better yet casn to post a picture of it? It is very likely that the transformer has +(2)2-1/5 % FCAN and either (2) or (4) -2-1/2% FCBN taps which you could use the -5% below normal tap which should bring the secondary voltage back up where it should be. If you have the -(4) you you have an additional (2) 2-1/2% taps.

I thought of that too but the meter voltage reading of the generator at the generator switchgear is 12.47KV which it tells me its producing this voltage.