Connecting to a 3-Can XFMR Bank on a Utility Pole

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gust1j

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Currently working on a job in a residential area adding some electrical sluice gate actuators to control sewage flow in the area. The gate actuators will run on any 3 phase voltage and luckily there is a utility pole with a 3-Can XFMR Bank near where we are planning to install the distribution panel. The 3-Can XFMR Bank appears to be connected to the utility pole secondary mains the same way as in the attached picture below, which from what I have researched I'm guessing the secondary is a 3Ph, 4W High Leg 120/240V Delta service because they are located in a residential area, but I'm definitely not an expert so any input is appreciated. My other question is if this is a 3Ph, 4W High Leg 120/240V Delta service is it a code violation to only connect the 3 240V phases of the secondary delta to the service entry without using the delta connected neutral? Would that change the connection to a Delta Primary - Delta Secondary 240V, 3Ph, 3W connection? I was wonder if I could eliminate the delta connected neutral because it would not connect to any of the gate actuators and the controls engineer said he was connecting all of his I/O to a 240VAC to 120VAC control transformer so the 120V neutral to phase connections would not be used either. Sorry if this is a dumb question, this is the first time I've had to connect a service to a utility pole and I'm a bit lost at the moment. Any Help is appreciated, Thank you.

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gust1j said:
Currently working on a job in a residential area adding some electrical sluice gate actuators to control sewage flow in the area. The gate actuators will run on any 3 phase voltage and luckily there is a utility pole with a 3-Can XFMR Bank near where we are planning to install the distribution panel. The 3-Can XFMR Bank appears to be connected to the utility pole secondary mains the same way as in the attached picture below, which from what I have researched I'm guessing the secondary is a 3Ph, 4W High Leg 120/240V Delta service because they are located in a residential area, but I'm definitely not an expert so any input is appreciated. My other question is if this is a 3Ph, 4W High Leg 120/240V Delta service is it a code violation to only connect the 3 240V phases of the secondary delta to the service entry without using the delta connected neutral? Would that change the connection to a Delta Primary - Delta Secondary 240V, 3Ph, 3W connection? I was wonder if I could eliminate the delta connected neutral because it would not connect to any of the gate actuators and the controls engineer said he was connecting all of his I/O to a 240VAC to 120VAC control transformer so the 120V neutral to phase connections would not be used either. Sorry if this is a dumb question, this is the first time I've had to connect a service to a utility pole and I'm a bit lost at the moment. Any Help is appreciated, Thank you.

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I’m sure others will have better input, it’s early and if I read correctly you are asking to bring in a 3phase delta (high leg) and not include the neutral.

I would say you would have to at least have the neutral to your service equipment so you have a place to bond your EGC. For I have never seen an EGC installed in a service mast or lateral.

I just don’t think you can get a ungrounded delta service from a solidly grounded secondary source.
 
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The grounded conductor, white wire, or neutral is required to be brought into your SE where it will be bonded to the GES you have developed. It then becomes the green wire, or equipment grounding conductor if you have no neutral loads.

That conductor is typically the bare conductor of the overhead ACSR.
I have supplied that cable in the past but never had to make connections directly to those transformers.
 
As others have said, you must bring the neutral conductor to the service equipment. See 250.24(C). It will be sized based on the size of the largest ungrounded service conductor and Table 250.102(C)(1).
 
Usually a quick tell-tell sign of a delta system, is one transformer of the three is larger than the other two. Not always, but very common on delta services.
 
You said the actuators will work on any voltage, so are these controlled by a frequency drive? I’ve heard on here that the tvss built into them may not like delta systems because of the higher voltage to ground on one leg. Perhaps our vfd guys will chime in?
 
hillbilly1 said:
You said the actuators will work on any voltage, so are these controlled by a frequency drive? I’ve heard on here that the tvss built into them may not like delta systems because of the higher voltage to ground on one leg. Perhaps our vfd guys will chime in?
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All of the transformers look like they are the same size, and the actuators are not controlled by a frequency drive.

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Kinda looks like a wye connection from that side, usually they jumper across from transformer to transformer to transformer with the delta, not with all leads going down.
 
gust1j said:
Currently working on a job in a residential area adding some electrical sluice gate actuators to control sewage flow in the area. The gate actuators will run on any 3 phase voltage and luckily there is a utility pole with a 3-Can XFMR Bank near where we are planning to install the distribution panel...
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That's all well and good to know for your own edification. But that's not how it's done.

It's not your job to look at utility company equipment to determine if a particular service can be supplied. Your EC needs to contact the utility with the requirements then the utility will tell you if it can be done and at what cost.

That said, it would be smart to get this done BEFORE any money was spent on design and before any equipment was ordered or purchased.

-Hal
 
LarryFine said:
No, that's definitely a high-leg delta.
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It looked like the three pots were tied together at a common point down low, but it was a shadow. Looks like they have a reduced neutral on the back pot. Our poco uses short jumpers pot to pot, not drops down to the lines. They also use a bigger pot on the single phase side, because it is usually loaded more than the other two.
 
Actually, now that I look more closely, it appears that the transformer has dual-bushing primaries, and they are wired in delta, too.
 
Amazing how things change. Our largest utility has changed to 3 phase pole mounted transformers where ever possible.
They prewire the secondary to a standard length and terminate in a "polaris" type block. It has allowed them to standardize their replacements and simplified connections. No transformer field interconnections at all. Bucket truck may not have a piece of wire on it.

Coincidentally, you can forget about 3 phase 240v services.. it takes an act of congress to get 240 vs 208;
 
augie47 said:
Amazing how things change. Our largest utility has changed to 3 phase pole mounted transformers where ever possible.
They prewire the secondary to a standard length and terminate in a "polaris" type block. It has allowed them to standardize their replacements and simplified connections. No transformer field interconnections at all. Bucket truck may not have a piece of wire on it.

Coincidentally, you can forget about 3 phase 240v services.. it takes an act of congress to get 240 vs 208;
Click to expand...
Do they hang all three at one time?
 
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