KVa?????

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Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Hello,

I am looking at a temp job and it is saying the utility is bringing in (2) 4kVa primary service feeders. I don't think the kVa is correct? It can't be volt amps..correct? Thanks.
 

mivey

Senior Member
Hello,

I am looking at a temp job and it is saying the utility is bringing in (2) 4kVa primary service feeders. I don't think the kVa is correct? It can't be volt amps..correct? Thanks.
Must be 4 kV (2.4 kV L-N, 4.16 kV L-L). I suppose they could give the line capacity, but I imagine they would give the size in cmil or AWG instead.
 

mivey

Senior Member
Thanks Miley. How many amps would that be??
There are three pieces: volts, amps, VA. You will need at least two to find the third. They have only given you either kV or kVA capacity so there is not enough information.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
Thanks Miley. How many amps would that be??

Mivey covered it: if you have a kV rating and the ampacity (conductor size) you can assign a maximum kVA value, but I've never seen that done nor do I see any point to it.
The ampacity depends on the wire size. I think 5kV conductor start somewhere around 1/0 and go all the way to 500 or 1000.
 

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Dont't know if this helps but the 4KV primary feeders are going to 500KW 277/480v transformers. I really ap[preciate the help guys. I was told to read through this and sit in and listen to them discuss this scope of work. I would like to be a little informed although I am not responsible for knowing the scope, just there to get some insight into this typoe of work.
 

mivey

Senior Member
Dont't know if this helps but the 4KV primary feeders are going to 500KW 277/480v transformers. I really ap[preciate the help guys. I was told to read through this and sit in and listen to them discuss this scope of work. I would like to be a little informed although I am not responsible for knowing the scope, just there to get some insight into this typoe of work.
You did not say how many phases. Plus, it is 500 kVA, not 500 kW.

Anyway, it is 4 kV feeders. About 69.4 amps per transformer for 3-phase primary.
 

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
You did not say how many phases. Plus, it is 500 kVA, not 500 kW.

Anyway, it is 4 kV feeders. About 69.4 amps per transformer for 3-phase primary.


Thanks again Mivey. They wrote 500KW but a mistake just like to 4KVA feeders. I'm confused..again:-?. So the feeder size from the POE to the tranformers will be one good for 69amps? Thats not big at all.
 

mivey

Senior Member
Thanks again Mivey. They wrote 500KW but a mistake just like to 4KVA feeders. I'm confused..again:-?. So the feeder size from the POE to the tranformers will be one good for 69amps? Thats not big at all.
69 amps MAX per transformer, but it depends on the load. How many transformers do you have?

Primary distribution feeders usually don't get as big as the secondary. We usually limit our 12kV feeders to between 400 and 600 amps. We used to go as small as about 100 amps but the smallest now is usually #2 ACSR at 175 amps (good for 2182 kVA 3-phase, considered ready for an upgrade at 75% of that)
 

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
69 amps MAX per transformer, but it depends on the load. How many transformers do you have?

Primary distribution feeders usually don't get as big as the secondary. We usually limit our 12kV feeders to between 400 and 600 amps. We used to go as small as about 100 amps but the smallest now is usually #2 ACSR at 175 amps (good for 2182 kVA 3-phase, considered ready for an upgrade at 75% of that)


I can't thank you enough Mivey...okay I will stop with the thank you but I do appreciate the help. So what I have(based on my paperwork) is (2) 4KV primary feeders either terminating fuse cut outs or ganged switched then running those primary feeders to the 500KVA transformers(about 1200' away) so I have to account for voltage drop I would assume. Bu the primary feeder run to the transfornmers would need to be good gor 69 amps so about a #4 wire? But like you said they secondary will be bigger because we are stepping down at the 277/480 transformer.
 
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