How do you tell Delta vs. Wye incoming power?

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STS83

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We are sub metering a building a was asked whether the 600V 400A service was delta or wye and I have no idea... any help is appreciated!
 
Either an electrician on site or the power company (POCO) should be able to answer that question.
In the absence of other information, inspecting the service wires and checking voltages to ground may provide the answer.
 
Is there a neutral at all? If not then it is most likely delta. If there is a neutral all line to neutral voltages will be the same (or at least very close to same) if it is a wye system. If it is a 4 wire delta, one line will be significantly higher voltage to neutral.

Remember neutral and grounded conductor do have different meanings, sometimes often they are the same conductor and people throw out terms pretty loosely but sometimes they are not the same conductor and that can get those that use the terms pretty loosely into trouble.
 
Where it matters is at the incoming service transformer. If THAT transformer has a Neutral, it's a Wye secondary. But if you can get that far into it, you can likely just read the nameplate to see it anyway.

Voltage measurements are OK, but in my experience, not 100% accurate. If you DO read 277V Phase to Ground at some point down stream, that does NOT automatically mean it is Wye secondary. There are a myriad of reasons why your meter may read 277V on an ungrounded Delta system. If on the other hand you read something OTHER than 277V (nominal) phase to ground, that would indicate it is NOT a solidly grounded Wye secondary. You may still not know what it IS however, could be Delta, could be HRG Wye.
 
Jraef said:
Where it matters is at the incoming service transformer. If THAT transformer has a Neutral, it's a Wye secondary. But if you can get that far into it, you can likely just read the nameplate to see it anyway.
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Yep. Simplest way is usually the best way.
 
Let's talk lower voltage for a minute... 208V and 240V.

If you get a look at the wires and they are colored or taped black, red, blue and white, by convention (not code) that's supposed to be 208/120 wye. If there's no pattern to how the breakers in a panel are installed, then it's almost certainly that.

If you open a panel and you notice either:
- every third space is missing a breaker (unless it's got 1-pole of a three pole breaker)
- a wire taped orange instead of blue (or purple instead of blue in San Francisco)
then that is probably a high leg delta. Black and red should be ~120V to neutral, and orange (or purple) should be ~208V. That's why there's no single pole breakers in those spaces.

I've never personally seen an ungrounded or corner grounded delta, but those will not have a neutral.

Now if the voltage is 600 and you don't have much experience knowing your services then you should look for a label or ask someone else.
 
jaggedben said:
Let's talk lower voltage for a minute... 208V and 240V.

If you get a look at the wires and they are colored or taped black, red, blue and white, by convention (not code) that's supposed to be 208/120 wye. If there's no pattern to how the breakers in a panel are installed, then it's almost certainly that.

If you open a panel and you notice either:
- every third space is missing a breaker (unless it's got 1-pole of a three pole breaker)
- a wire taped orange instead of blue (or purple instead of blue in San Francisco)
then that is probably a high leg delta. Black and red should be ~120V to neutral, and orange (or purple) should be ~208V. That's why there's no single pole breakers in those spaces.

I've never personally seen an ungrounded or corner grounded delta, but those will not have a neutral.

Now if the voltage is 600 and you don't have much experience knowing your services then you should look for a label or ask someone else.
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OP is apparently in Canada - 600 volts is common there, don't know if they commonly have 600 volts from a delta secondary or not though. Wye system would be 600/347 volts. A 600 volt delta with high leg would be 300 to neutral on two lines and about 520 on the high leg.
 
STS83 said:
We are sub metering a building a was asked whether the 600V 400A service was delta or wye and I have no idea... any help is appreciated!
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ggunn said:
If it has a neutral it could be a delta/high leg system.
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Context. The likelihood of a 600V delta high leg system with a center tapped winding where the L-N is 300V... not quite even approaching a hint of being slim, to none.

600Y347 on the other hand, very common in Canada. 600V delta, never heard of it being used, but certainly possible, especially in an older manufacturing plant of some sort.
 
Jraef said:
Context. The likelihood of a 600V delta high leg system with a center tapped winding where the L-N is 300V... not quite even approaching a hint of being slim, to none.
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OK, but I was addressing what appeared to me to be a global comment that if it's three phase with a neutral it must be a wye.
 
ggunn said:
OK, but I was addressing what appeared to me to be a global comment that if it's three phase with a neutral it must be a wye.
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Point taken. I often forget that someone searching on this issue someday may end up seeing one posting without the context. I will endeavor to do better.
 
kwired said:
I've never seen any system in Canada;)
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You should go, it's pretty up there. Don't bother with Manitoba and Saskatchewan, they will look exactly like home to you, but I love Banff and Lake Louise in the Rockies. A trip on "The One" (Hwy 1) from Calgary to Vancouver in a good car is one of the all time great road trips. It's also a nice train ride.

I worked for a company servicing lumber mills all over the West, including Western Canada. I saw a lot of BC and Alberta, loved it all. Except in winter...
 
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