Topic '3-Phase Electric Service--Discussion' in forum 'Home Improvement' - dslreports.com http://www.dslreports.com/forum/3Phase-Electric-ServiceDiscussion-20922898 en Fri, 10 Feb 2012 18:28:39 EDT Fri, 10 Feb 2012 18:28:39 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20931106
Since even a small change in your power configuration would result in some amount of downtime I suspect that you will be on the high-leg delta for quite some time.
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I guess your notation about "note the voltages" refers to not having a 208 leg on the Delta setup? While I don't know what exactly he might have meant, that isn't it. In Wayne's diagram the 208V leg is Phase c to Neutral (which kind of implies that the diagram predates the NEC which states that the high-leg should be Phase b).

A plain, regular Delta configuration isn't grounded at all. A corner-grounded Delta has one of the phases grounded and a high-leg Delta has the center tap of the A-C transformer grounded.
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Got some spare cpu cycles ? Join Team Helix or Team Starfire!]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20931031 Sun, 10 Aug 2008 22:11:38 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20931007 said by leibold:

Scenario 1: the backup generator too is providing a high-leg delta output and his building does not perform any transformation. 120V loads are connected between phase 1 or phase 3 and neutral. 208V loads are connected between phase 2 and neutral and 240V loads (if any) are connected between any two phases. In this case any change by the utility to plain Delta or Wye distribution would require significant changes.

Scenario 1 is what we have, right on the button. As I mentioned, we need to figure out exactly what in the building complex requires each voltage, and take it from there. I do believe we are on the unbalanced side, if that is the correct term. Much more use of 120V than anything, and would *guess* that 240 is next, with the A/C system and such.

In any case, this whole event is going to make us learn a little more about the service in general, at least as it pertains to future changes.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20931007 Sun, 10 Aug 2008 22:08:15 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20930981 said by Splitpair:

Here's a couple of old (note the voltages) diagrams detailing pole pig wiring for for both Delta and Wye.

Wayne
Nice diagram Wayne. I guess your notation about "note the voltages" refers to not having a 208 leg on the Delta setup? The config here is a Delta, but it is the three-phase four-wire result like the Wye diagram. ]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20930981 Sun, 10 Aug 2008 22:03:07 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928710 said by Splitpair:

said by whizkid3:

Well, you learn something new every day. Understanding how things can be wired (or mis-) in the Midwest from many of the posts I've seen here; my guess would have to be that it started getting called the wild leg, after it went wild and blew a few things up. :)
Amongst linemen it is called the wild high or bastard leg.

Wayne

We usually call them "bastard" legs... but you just don't see them any more... ]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928710 Sun, 10 Aug 2008 12:50:01 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928277 http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928277 Sun, 10 Aug 2008 10:52:20 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928131 said by whizkid3:

Well, you learn something new every day. Understanding how things can be wired (or mis-) in the Midwest from many of the posts I've seen here; my guess would have to be that it started getting called the wild leg, after it went wild and blew a few things up. :)
Amongst linemen it is called the wild high or bastard leg.

Wayne

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If you cannot fix it with a buttset and some beanies you ain't a technician.
]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928131 Sun, 10 Aug 2008 10:08:20 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928124
Wayne
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If you cannot fix it with a buttset and some beanies you ain't a technician.
Click for full size
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]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928124 Sun, 10 Aug 2008 10:06:08 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928021 said by mattmag:

said by nunya:

We call it "wild leg" & "high leg" here.
Well there's two more of us now, I'm glad to hear! I know I haven't been dreaming that... :)Well, you learn something new every day. Understanding how things can be wired (or mis-) in the Midwest from many of the posts I've seen here; my guess would have to be that it started getting called the wild leg, after it went wild and blew a few things up. :)]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20928021 Sun, 10 Aug 2008 09:23:04 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927978
In general, your best bet would be to work with the utility to ge]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927978 Sun, 10 Aug 2008 09:03:22 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927858 said by Kearnstd:

hmm never knew that lighting had any standard voltages over 120v. does that need different switches? or the use of some sort of Contactors running with a lower voltage on the light switches?
277V lighting is being used in commercial buildings. You need to use hardware that is rated for 277v.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927858 Sun, 10 Aug 2008 07:45:06 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927629 --
[65 Arcanist]Filan(High Elf) Zone: Broadband Reports]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927629 Sun, 10 Aug 2008 02:52:45 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927452 said by whizkid3:

I'll bet you won't find it used in any literature, professional journals, or trade magazines. The terminology is simply not used in the industry any place that I'm aware of. 'High' leg is the proper term.
Looks like wiki is familiar with the term: »en.wikipedia.org/wiki/High_leg_delta

Pretty neat stuff however, no matter what it's called! Very interesting to hear about it from folks that deal with it on a daily basis.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927452 Sun, 10 Aug 2008 01:07:10 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927396 said by whizkid3:

It was probably the 'b' phase lost on the utility transformer primary. End result is you still had 120V lighting power available and didn't notice it.
That's the scenario I was guessing, but wasn't sure how those phases were set up until this thread. I'm not sure what devices in the building use 208 vs 240, but I'm going to find out. The main higher-voltage items would be the A/C units, and the elevator, which is an electric over hydraulic setup. All of the jail stuff is 120V as far as I know, as is the 9-1-1 equipment.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927396 Sun, 10 Aug 2008 00:46:18 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927388 said by nunya:

We call it "wild leg" & "high leg" here. Well there's two more of us now, I'm glad to hear! I know I haven't been dreaming that... :)

said by nunya:

Most likely you folks have your own transformer(s) on site to get a Y service, or there is a separate service for the 120V.
No separate service or transformer on site that I know of. There is only the three primary wires from the utility that feed three transformers on the pole, and that runs straight into the main disconnect in the basement where we also installed the generator transfer switch. Maybe I will get some pics posted to help show how it is set up.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20927388 Sun, 10 Aug 2008 00:42:44 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926685 We have an extra special monster called a "corner grounded" or "grounded b phase" delta system implemented in many older installations. This is not installed anymore, but many are still functional. I hate these.

Most likely you folks have your own transformer(s) on site to get a Y service, or there is a separate service for the 120V.

Delta and Wye systems are pretty much the same in efficiency. Delta systems are more common where the utility only provides "primary in". Usually heavy commercial & industrial.
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All we need now is a car that runs on milk.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926685 Sat, 09 Aug 2008 20:59:53 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926616 said by whizkid3:

As far as 'wild' leg goes, I have never heard such a thing and it amazes me that you've heard it for many years,
I've heard it called "wild leg" too. Maybe it's a Midwest thing.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926616 Sat, 09 Aug 2008 20:34:19 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926351 Most of the transmitter sites I work with have delta power.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926351 Sat, 09 Aug 2008 19:31:06 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926081 said by mattmag:

said by whizkid3:

Do you have a UPS? This would explain why it seemed no one lost power. It would be nuts to build a 911 call center, of any size, without a UPS covering all critical communications and IT functions without them off of UPS.

Yes, we have a UPS, but it is only utilized on critical loads, so nearly all of the lighting circuits are not on it.It was probably the 'b' phase lost on the utility transformer primary. End result is you still had 120V lighting power available and didn't notice it.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926081 Sat, 09 Aug 2008 18:14:14 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926033 said by leibold:

One thing that I didn't see mentioned yet is that it is perfectly fine to attach a Delta load to a Wye distribution system (In such a case the neutral wire from the Wye distribution remains disconnected from the input of the Delta load).That's done usually where power quality is a concern (most places). The delta primary is run through a delta-wye transformer, with the wye secondary. This provides great isolation between the two, and greatly mitigates harmonics and imbalances on the secondary from passing to the primary feeders. The secondary is wired in a three-wire delta configuration, although a wye service and corresponding neutral is available at the transformer secondary. From here you are typically connecting machinery or another step-down transformer (with the 208/120v 4 wire wye). The proper planning must be done to ensure that the voltages on the wye secondary are correct to provide 3-wire delta distribution.

Thanks for posting that diagram, liebold. Siemens is the one company I know of that makes panelboards for high-leg systems. They are very costly with regards to standard 3-phase panelboards. I often see standard three-phase panels used incorrectly. The Siemens panelboards prevent the connection of 120V single-pole breakers from being connected to the high-leg (which would end up giving you 208v to the neutral). The big problem with this system, is that the utility side is often inbalanced. Likewise, the transformers are often overloaded on the side with the 120V available. (The 120v windings can often only put out about 10% of the power available phase-to-phase).

As far as 'wild' leg goes, I have never heard such a thing. 'High' leg is the proper term.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20926033 Sat, 09 Aug 2008 18:01:44 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20925752 --
One man's Magic is another man's Engineering.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20925752 Sat, 09 Aug 2008 16:41:33 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20925570 Wye is way more convenient than Delta in supplying mixed loads in a building.
However the special situation of the high-leg Delta may indeed be such that it will be discontinued since it promotes unbalanced loading of distribution systems.

One thing that I didn't see mentioned yet is that it is perfectly fine to attach a Delta load to a Wye distribution system (In such a case the neutral wire from the Wye distribution remains disconnected from the input of the Delta load). However you are not allowed to connect a Wye load to a Delta distribution system (unbalanced loads would cause voltage fluctuations, never mind the safety issues surrounding the grounding of the neutral wire).

How easy or difficult a change by the utility company would be for Mattmag depends on how he currently utilizes the high-leg delta power he receives.

Scenario 1: the backup generator too is providing a high-leg delta output and his building does not perform any transformation. 120V loads are connected between phase 1 or phase 3 and neutral. 208V loads are connected between phase 2 and neutral and 240V loads (if any) are connected between any two phases. In this case any change by the utility to plain Delta or Wye distribution would require significant changes.

Scenario 2: the backup generator provides a plain Delta or Wye 3 phase power. The output of the automatic transfer switch goes to a Delta-Wye transformer providing 208Y/120V as is typical for light commercial applications. 120V loads are connected between any phase and neutral while 208V loads are connected between any two phases. As long as the voltage itself doesn't change, it doesn't matter in this scenario whether the utility is providing a Delta or Wye 3 phase power.

Scenario 3: the backup generator is single (split) phase 240/120V. Despite the fact that the utility currently provides a high-leg delta all loads are either 120V (between phase 1 or phase 3 and neutral) or 240V between phase 1 and phase 3. This would mean that 3 phase power (while available) isn't actually being used as such and a switch to residential style single phase service would not require any changes.
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A good explanation of the high-leg delta from Siemens
]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20925570 Sat, 09 Aug 2008 15:51:27 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20925012 said by whizkid3:

The utility guy you spoke to at the truck, either knows little about distribution system design, or you misunderstood at some points, mattmag. It is a 'high' leg, not a 'wild' leg (although this could be their slang, or he has colorful vernacular).He definitely said "wild" leg, and actually that's a term I have heard around here for many years. Guessing it is one of those terms that varies by region. It is a four-wire service, and the voltages are as you noted- 208-240-120.

said by whizkid3:

Do you have a UPS? This would explain why it seemed no one lost power. It would be nuts to build a 911 call center, of any size, without a UPS covering all critical communications and IT functions without them off of UPS.

Yes, we have a UPS, but it is only utilized on critical loads, so nearly all of the lighting circuits are not on it. That's why it is usually quite apparent anytime we lose power, as the lights will go out! ;) In this case, at least in the call center, no lighting was affected by the loss of the single leg. Also, since it was after business hours for the rest of the courthouse, the remainder of the building was already unoccupied.

said by whizkid3:

Even more popular is 4 wire, 480/277 volt wye secondaries (or 460/265v in NYC). The only transformers that are needed are to provide 208/120 volt service.
That's the configuration he said is the way they like to go now. Since we already have a fairly new generator and transfer switch that is set up for the current Delta service, it isn't likely we will ever see it change. The only part I would like to change is to move the service underground, but even that carries a pretty high price tag with it.

The way it is now, the pole with the three transformers on it is just outside the door into the call center area, next to the building in the parking lot. If it ever fell over for some reason, it would land on our generator!! Talk about losing your primary AND your backup in one motion... ;)]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20925012 Sat, 09 Aug 2008 13:28:13 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924600
If the primary side cut off switch opened, you certainly lost power on your end, and the generator was doing its job. Do you have a UPS? This would explain why it seemed no one lost power. It would be nuts to build a 911 call center, of any size, without a UPS covering all critical communications and IT functions.

quote:
If you lose a Y like you did, you can halve the voltage I believe. The Y can deliver more power with less current.

If we're talking wyes and deltas with the same voltage, thats not correct. Less current per wire (one is 3w the other is 4w), but only if you had an inbalance on the neutral., which is not the way you want to go.
quote:
With a Delta you have reduced voltage but it is less catastrophic It's more fault tolerant

If the delta is non-grounded, then that's true. Its less susceptible to ground faults. The vase majority of utility primary systems are delta. To begin with, its less wire and less cost. I don't know what you're talking about, Jtmo, with regard to 'reduced voltage'.

quote:
So a 240V wye setup will also support a 120V single phase setup. This works well in businesses with very unbalanced loads on each phase. Delta is phased out because you can accomplish the same thing with a wye, but have more flexibility.

Its a simple matter to have a transformer with a delta primary and a wye secondary within the business, and every business on this utility secondary will. Otherwise there 120 volts would not be available in the building. Delta - is certainly not phased out. What would be phased out is the wimpy 240/208 volt (high leg) distribution.

Most utility delta secondary distribution I see is 480 volts, and serves buildings with higher loads - (which most have). It also provides 480 volt delta directly to large motors (think air conditioning systems). These buildings will have 480-480/277v and 480-208/120v transformers. 277 volt lighting, which most large office buildings have today. Both are more effficient and cost less to wire. Even more popular is 4 wire, 480/277 volt wye secondaries (or 460/265v in NYC). The only transformers that are needed are to provide 208/120 volt service. Buildings of the size that I picture mattmag talking about tend to have 3 phase, 4 wire wye, 208/120 volt service.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924600 Sat, 09 Aug 2008 11:53:33 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924350
Back to teh OP, i meant Delta and said Wye. but the jist of it was both configs are still very common.
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Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine!]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924350 Sat, 09 Aug 2008 10:55:13 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924321 said by sdgthy :

Here's a little bit about the differences between delta and wye
Pretty comprehensive link. I'll stop writing my descriptions now...]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924321 Sat, 09 Aug 2008 10:46:54 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924262 www.elec-toolbox.com/usefulinfo/xfmr-3ph.htm]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924262 Sat, 09 Aug 2008 10:31:46 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924047 http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20924047 Sat, 09 Aug 2008 09:31:10 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923842 http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923842 Sat, 09 Aug 2008 08:15:18 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923410 said by Jtmo:

With a Delta you have reduced voltage but it is less catastrophic It's more fault tolerant.

That seems to be the case tonight. Most stuff kept running fine, and gave no indication of the failure.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923410 Sat, 09 Aug 2008 02:05:23 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923407 said by davidg:

i have no clue why he said Wye setups are not used anymore, you use whichever one fits your needs best. BOTH are very common.

He said the Delta config is the one they don't use anymore, and that's what we have. Maybe it's just the preference they have now? Who knows. I was just interested in the way they are wired to the primaries and such. I could see that one leg of the primary fed two different transformer inputs, and one of the transformers I believe had 3 outputs while the other two had two outputs in use.

On the equipment part, we used to run all Motorola stuff, with the Centralink phone switch and Centracom II consoles. Just about a year ago we replaced it all with Zetron equipment, complete with all touch-screen controls for phones and radio. Very nice stuff.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923407 Sat, 09 Aug 2008 02:03:55 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923094
With a Delta you have reduced voltage but it is less catastrophic It's more fault tolerant.

But, that was a long, long time ago and it was a bit confusing then.]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923094 Sat, 09 Aug 2008 00:20:18 EDT Re: 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923044
i have no clue why he said Wye setups are not used anymore, you use whichever one fits your needs best. BOTH are very common. also, if you change it you may have to change other things. i know the POCO at one of our tower sites was replacing old poles and wanted to convert us from Wye to Delta or just plain single phase if possible. we only use the 120v now, but the site used to be an old ATT Longline site and was setup for Wye. the Generator, transfer switch, adn most internal wiring would require changes to make it work.

before you evne consider it, GET A PROFESSIONAL ELECTRICIAN TO VERIFY WHAT YOU NEED.

BTW, what type E-911 system you running? i maintain a couple of Plant systems and used to maintain 8 CentraLinks.
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Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine!]]> http://www.dslreports.com/forum/Re-3Phase-Electric-ServiceDiscussion-20923044 Sat, 09 Aug 2008 00:07:07 EDT 3-Phase Electric Service--Discussion http://www.dslreports.com/forum/3Phase-Electric-ServiceDiscussion-20922898 Here's one for you "high-line" kind of people out there. ;)

Tonight at our local 9-1-1 Center in the courthouse, the standby generator unit for the building fired up, for no obvious reason, or at least it seemed that way for awhile. I got a call telling me about this since I'm the Chairman of the 9-1-1 Board for the county, and also the de-facto expert on all things related to 9-1-1, whether I really know anything or not...

Anyhow, I arrived in the parking lot and yep, the generator unit is running, but we weren't aware of any failures at all. I went downstairs in the building, and checked the transfer switch equipment which was indicating no utility power on the control board. Hmmm... That's odd, since the dispatch folks didn't have an outage at all...

Went back outside, and gazed up at the overhead transformers, and saw that one of the primary leg fuses was opened, and hanging down. OK, that would do it!! Called the utility, and waited for them to arrive. When they did, they gave it all a lookover, and decided that perhaps the fuse was damaged from the storm earlier in the week, and it finally let go now. Seems logical. So, they dropped the fuse down, replaced the fuse core, and hung it back in. When they snapped in back up into place, BANG!!! along with a nice fireball from the general area. So, looks like a toasted transformer after all.

On looking closer after this brief re-power episode, you could see where one was starting to leak fluid. Bad sign. I ask the guy a little bit about the whole thing, and he mentioned that the service is setup in "Delta" configuration, which he said is no longer used for new installations, and now it is all a "Y" configuration, which he said gives better ground ability, and is more even at 208V, where the setup we have now is 208, with a 240V "wild" leg. Interesting. Of course, they can't re-config it at this point, so for now they are replacing the one transformer, which is a rather large unit that he said weighs in at about 2000 Lbs.

So, for you utility-minded guys and gals---can you explain the "Delta" vs. "Y" configurations a little? Seemed like something we could learn more about here!

-Matt]]> http://www.dslreports.com/forum/3Phase-Electric-ServiceDiscussion-20922898 Fri, 08 Aug 2008 23:38:27 EDT