3 phase service type ID by powerline tap configuration?

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gar said:
170213-2443 EST

Clodbuster:

How did the power company save any wire? Three wires minimum are required for three phase (a delta source). A wye source with neutral would use four wires. However, I could use two hots and neutral from a wye source to create a three phase output after transformers.

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What I meant was that by the POCO choosing to use two transformers in the yard in an open wye open delta configuration they saved a conductor in at least one place. Either in the 1/4 mile drop from the lines to the yard or in the mile+ powerline run from the drop to the nearest 4-wire powerlines. When the system was installed the powerlines were 3 wire, only recently updated to 4 due to road widening.
 
As I read the original posting, he said the PoCo replaced the pole lines when the road was widened. The cost savings would have been in the original installation by only running two hots and creating open delta drops for the few customers needing 3 phase. But when they widened the road, that implies more people moved in, so to get better voltage balance on their primary system they had to add in the third phase.

That however meant nothing to the OP because his pad mounts were already set up for the open delta, so they were not about to give HIM a third transformer and switch him to a 208V wye, then suffer the complaints etc. They just reconnected him to what was already there, the third phase was added for them to help balance out the new customers.
 
Jraef said:
As I read the original posting, he said the PoCo replaced the pole lines when the road was widened. The cost savings would have been in the original installation by only running two hots and creating open delta drops for the few customers needing 3 phase. But when they widened the road, that implies more people moved in, so to get better voltage balance on their primary system they had to add in the third phase.

That however meant nothing to the OP because his pad mounts were already set up for the open delta, so they were not about to give HIM a third transformer and switch him to a 208V wye, then suffer the complaints etc. They just reconnected him to what was already there, the third phase was added for them to help balance out the new customers.
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Happens that way here a lot. Load changes dictate upgrading the line, road construction or other projects sometimes helps make that decision to upgrade, but anyone already served with open delta usually remains open delta when all is done, especially if they are a limited three phase load to begin with.
 
kwired said:
Happens that way here a lot. Load changes dictate upgrading the line, road construction or other projects sometimes helps make that decision to upgrade, but anyone already served with open delta usually remains open delta when all is done, especially if they are a limited three phase load to begin with.
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I had a rural customer who was had a single phase service off of a SWER system for years and was using VFDs to run 3 phase motors. He got all excited about getting upgraded to 3 phase when they came in to add the other lines on the poles because of a road widening project, thinking they would "give" him 3 phase now. They offered it to him, for $15k! They were still going to make him pay for the new transformers because his would still be the only 3 phase drop for miles. That 3 phase run was meant for the new Indian casino going in further up stream.
 
kwired said:
Happens that way here a lot. Load changes dictate upgrading the line, road construction or other projects sometimes helps make that decision to upgrade, but anyone already served with open delta usually remains open delta when all is done, especially if they are a limited three phase load to begin with.
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It ALMOST worked out perfect to get a free upgrade to 4-wire service: The POCO had to come out and replace the underground service to the yard from the powerlines since it failed. Also, they replaced the powerlines with 4-wire service when the road got widened.

The only problem was they happened in the wrong order! :lol:
 
170214-2339 EST

Clodbuster:

Why is a 4 wire vs 3 wire primary service of any benefit to you? Your transformers were not changed, and if they had been would you be better off?

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gar said:
170214-2339 EST

Clodbuster:

Why is a 4 wire vs 3 wire primary service of any benefit to you? Your transformers were not changed, and if they had been would you be better off?

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No benefit at all until you want to increase service capacity and POCO insists your new setup will need full delta or wye on the primary side.
 
170216-1009

Clodbuster:

In your post numbered # 22 you wrote:
What I meant was that by the POCO choosing to use two transformers in the yard in an open wye open delta configuration they saved a conductor in at least one place. Either in the 1/4 mile drop from the lines to the yard or in the mile+ powerline run from the drop to the nearest 4-wire powerlines. When the system was installed the powerlines were 3 wire, only recently updated to 4 due to road widening.
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For 3 phase output of any configuration you only need three input wires. The savings obtained by using an open delta secondary result from only requiring two transformers.

As I previously mentioned in my neighborhood our primary service is three wire delta from my perspective. There are only three insulated wires on my pole. This actually saves the power company the cost of a fourth wire. This allows me or others to have three phase service. I don't have three phase (only a single transformer). But there are a couple neighbors with three phase open delta power. One has the wild transformer a number of poles away from the single phase transformer. Note: I could have a closed delta if I wanted.

In other neighborhoods (newer ones) there is only a two wire primary supply from a wye substation source. A substation neutral and one hot wire.

At our shop the primary supply at the street is four wire wye from the substation, less than one mile away. Three wires from this distribution line at the street, one neutral and two hots, come from the street to a pole at the side of the building with two transformers and an open delta secondary configuration. If our load were to increase enough to overheat the transformers, then DTE would add a transformer.

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170216-1337 EST

With two input phases and transformers I can get more than two output phases. This can include some stranger phase angles.

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