Primary Transformer

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coppertreeelectric

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I have a job to do where I need to run a 1000' primary's to a pad that I will be installing, Then 3 secondary's for 3 houses. Excuse my ignorance but I haven't installed many primarys. The customer would like a 3 phase transformer that will provide 3 secondarys @ 200amps x 3 = 600amps.

1- What primary wire would I use in this application for 3ph and Direct burial?

2- Is there a big price difference between direct burial and non-direct burial cable? I would call a supplier but there not open until the morning, and I am trying to figure the best way to do the job.

3- Can other conduits be ran in the same trench as the primary, e.g. Telephone, television?

Thanks for any input, Steve
 
Re: Primary Transformer

The customer would like a 3 phase transformer that will provide 3 secondarys @ 200amps x 3 = 600amps.
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What do you need the 3 phase for? Is there 3 phase load? What is the voltage? You need to caculate the load using Article 220. 600 amps
will not likely be the total caculated load.
Will the utility provide 3 phase service. Some will not.
 
Re: Primary Transformer

What do you need the 3 phase for? Is there 3 phase load? What is the voltage? You need to caculate the load using Article 220. 600 amps
will not likely be the total caculated load.
Will the utility provide 3 phase service. Some will not.
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The customer is a cook and wants 3ph 208 for mixers. I still need to talk to the utility and see what the voltage on their end will be, and yes the utility will provide 3ph service.

I just really need to know the name of the primary direct burial cable is, so when I call the supplier I know what to get a price on? and if someone could answer my question about the difference in price on burial vs non-burial.
 
Re: Primary Transformer

This is really weird, will you have the primary metered? Assuming that is true, you will have a plethora of cable to choose from. I would use #2 Al. 15 kV EPR JCN triplex cable for the primary and 300 kcmil Al. for the feeders from your separately derived service to each panelboard. I also believe that a 75 kVA transformer is the smallest oil filled transformer you will be able to find at 208Y/120 volts and I would use a dead front design. :D
 
Re: Primary Transformer

Charlie, what was the part you ref as weird? The 3ph part?

I talked to the utility and they will be providing the transformer, but I will need to lay the primary. They will have to tell me the voltage. I will also be going to the site in a few minutes to measure the secondary lengths.

I appreciate any help you guys can give along the way.


Steve
 
Re: Primary Transformer

I talked to the utility and they will be providing the transformer, but I will need to lay the primary.
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Do they want you to pedal the bicycle-generator also :D

I think Charlie means it is very unusual for the utility not to install the primary themselves.

Steve
 
Re: Primary Transformer

Its also unusual for the utility company to have EC do the service tap-on, but welcome to the world of Central Hudson Gas & Electric.

Its really not a matter of will the run the primary, its more how much will they do it for. Because the primary needs to be ran about 1000' into the customer property they don't want responsibility. If I charge $15k for the job the utility would charge about $25k.

It works for me, I enjoy the bigger jobs and bigger bucks. So you wont hear me complaining.
 
Re: Primary Transformer

What wire and pipe size would you guys recommend for a 400' 200amp 1ph secondary?

Thanks, I just keep second guessing myself on this one.

Steve
 
Re: Primary Transformer

The whole setup seems weird to me. Normally, this would be 1?, the primary, transformer, pad, and the service cable would be provided by the serving electric utility.

To answer your question, I would still use 300 kcmil Al. for the service cable. Since it is not a SDS, you are not installing feeders like I thought you were doing.

The question I have now, is this 1? or 3?? The first post says 3?, the last post is asking about 1?. :D
 
Re: Primary Transformer

I just notices you said a 400 ft secondary. I was thinking you were running 1000 ft to get close to the services and splitting them into 400 ft total. It now looks like a 400 ft service lateral. What are we really talking about? :D
 
Re: Primary Transformer

I just notices you said a 400 ft secondary. I was thinking you were running 1000 ft to get close to the services and splitting them into 400 ft total. It now looks like a 400 ft service lateral. What are we really talking about?
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LOL... Okay, This is the deal.

2 parts to this job, and I already sent over the pricing.

Part 1: 1000' Primary total. I will be installing two utility polls. One will be a street crossing utility pole, the existing pole is on the wrong side a the street. The second pole I will be installing is to extend the primary overhead 300' from the roadway to cross over a stream. At the 300' mark I will be dropping underground using #2 al triplex primary cable in 2" PVC. The underground portion will extend 700' to a transfer pad I install.

Part 2: Run a secondary service feeder to the existing house on the property. Install a 200amp service and make all necessary connections.

The utility company will be providing the transformer and a crew to make the connections at the transformer and pole, thats all they will get involved.

We decided to stay single phase due to the difference in price. The install will be 1ph 120/240.

My grand total price for both parts not including permits and inspections is $17,900.

Hope that cleared it up a bit.

The utility company in my area really leaves alot to the EC's. We pretty much do everything but work on the primary end. I enjoy the challenges and have fun doing the work.

Steve
 
Re: Primary Transformer

We pretty much do everything but work on the primary end.
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I meant to say "everything but work on the LIVE primary end. If its customer owned we do the work. Even though this is a primary run we are doing, its on the customer property. The utility company will only go 180' into the customer property. Our utility company stopped doing road crossing poles 3 months ago, now its the responsibility of the EC to get the power on the customer property.

Soon, at the rate we are going the EC will be hand cranking the turbine generator at the power plant. It may be time for me to buy a pole truck so I don't have to keep sub-contracting out my pole work.
 
Re: Primary Transformer

OK, now it make sense. Be sure they use a dead front transformer and follow the manufacturer's direction in making up the elbow terminators. If you are responsible for the maintenance of the transformer terminations, be sure to put a lightning arrestor on the feed through bushings (it just plugs into the second primary bushing).

The 300 kcmil is great for a close service but since it is 400 ft away, you need to do voltage drop calculations to size the secondary. I am guessing that 500 kcmil would not be unheard of for the distance. Look at the size of cable you can land in the meter fitting, if you max out, and the cable is not large enough, you will have to put in a junction box so you can reduce the cable for the lugs.

If at all possible, put the transformer closer to the service, everything gets simpler. :D
 
Re: Primary Transformer

If at all possible, put the transformer closer to the service, everything gets simpler.
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Charlie, I would love to move the transformer to the front porch of this house. The problem is that even though only one house currently exists, there are blueprints on two more houses to be built. The new transformer will be centrally located in the center of the triangulated layout of all three homes. I didn?t see any better way to do this.

I also plan to install a pull box half way up the 700' primary run, with a loop in the primary cable for future use if necessary; this has been Okayed by the local utility.

Steve
 
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