230V Delta?

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We have alot of this old black kinda rubbery kinda fibrous conduit run throughout the plant. I don't know what its called but its not metallic. I did discover that we have pretty heavy (like ~1000MCM) bare wires poured in the concrete of the duct banks and run from substation to substation that bonds the unitsubs together but its not run through the conduit with the other current carrying wires.
 
I'll try and grab some pictures when we deenergize and get in the manholes. I actually have a copy of american electrician's handbook! An old family friend that teaches electrical at the vo-tech recommended it to me when I was thinking about going to school for electrical stuff. I'll crack it open this weekend and see what I can find. Thanks for the idea.

The earliest parts of the mill were actually built right after the revolutionary war (late 1700s). Obviously there were no arc furnaces back then ;) but some of the buildings we still use as production areas are dated pre 1900s on the drawings. Most of the modern infrastructure, including the existing electrical systems, was installed between 1940s-1970s.
 
bigbach007 said:
I'll try and grab some pictures when we deenergize and get in the manholes. I actually have a copy of american electrician's handbook! An old family friend that teaches electrical at the vo-tech recommended it to me when I was thinking about going to school for electrical stuff. I'll crack it open this weekend and see what I can find. Thanks for the idea.

The earliest parts of the mill were actually built right after the revolutionary war (late 1700s). Obviously there were no arc furnaces back then ;) but some of the buildings we still use as production areas are dated pre 1900s on the drawings. Most of the modern infrastructure, including the existing electrical systems, was installed between 1940s-1970s.
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I believe that old stuff is called 'Orangeburg' , pictures would be interesting.

Orangeburg Conduit Duct Bank

I am currently doing the design for a new underground duct bank system,and have been requested to remove portions of the old existing concrete encased duct bank. We have found that some of these old duct banks contain Orangeburg conduit which is an asbestos fiber type conduit. Has anyone else...
forums.mikeholt.com
 
Our church, built in late 60's, had similar heating ducts buried in the floor slab. When they failed and were blocked by their own debris we had to replace the entire system with a new furnace and new ducts above the ceiling.
There was no access to ream them out and even if we could the heat loss to the concrete would have been unacceptable by current standards.
 
bigbach007 said:
I work in an old steel mill in PA and most of our substations have ungrounded delta transformers. What brought me to this thread is that I'm trying to understand what is the code on EGCs for ungrounded delta systems? We bring 46kV into the plant and distribute 6.9kV around the plant to the substations mostly via underground PILC cable. When these lead cables blow and we replace them with dry cables, we're already usually over our conduit fills because the old lead cable is a much smaller diameter. Then til you add a ground wire, the conduits are really full. We've had contractors insist on pulling a ground wire with the current carrying conductors in the past because of 250.186. In order to get everything to fit in the existing underground conduits, we usually have to reduce the cable size. Fortunately we can get away with that in some places but in others, we need to maintain that capacity of the existing PILC cable. When I read 250.186 it says, where an ac system operating at over 1000 volts is grounded at any point, a grounded conductor shall be installed and routed with the ungrounded conductors to each service disconnecting means and shall be connected to each disconnecting means grounded conductor terminal or bus. But if the system is ungrounded (and there are equipment grounds present to grounding electrodes at each substation) is the EGC needed? What purpose does it serve other than bonding unitsub to unitsub? None of the old PILC cables have a ground wire pulled with them in the conduit. If anyone has run into this and can point me to a particular NEC article I would appreciate it.
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250.4 the place to start and the wording generally reading 'equipment likely to become energized' and ' provide an effective fault clearing or fault carrying path'.

And this docoment for systems commonly installed that have been found to cause fatalaties, distributing power without also carrying an EGC or effective fault clearing path. This imo would be equally dangerous for grounded and ungrounded systems, but was common enough at one time. Called local peg grounding in the report, the remote equipment will float at the phase line voltage when it faults to ground.

MSHA - Technical Reports - MSHA METAL/NONMETAL ELECTRICAL GROUNDING REQUIREMENTS

Federal enforcement agency responsible for the health and safety of the nation's miners.
arlweb.msha.gov

First thing I would look at is the supply transformer nameplate for the secondary winding, it could be a Y secondary, even if all the loads are delta connected. And then the code references for it. A delta secondary winding could be grandfathered and compliant as a floating delta with conditions, but Y secondary could be a system required to be grounded. Over 1000 Volts systems usually have their own code references and I did not check them, just saying I would know where to start looking. You would first want to know if the secondary is delta or Y, and then if it is a system required to be grounded.

The loads are most likely delta, but that refers to the loads pre-semiconductor era, and again, MV stuff is different than 480. If it was a 480 secondary, following generations would have tried to add just about anything and everything to it, single phase lighting (with no neutral), drives, rectifier front end loads.

Any load on it with a rectifier front end, it's a good bet the load has some type of front end filter network that is Y connected and grounded. This would be a fault on a floating supply. Most floating three phase power, it's a good bet the first ground fault is already present.

Contiguous bonding of all metal and the contiguous EGC is absolutely necessary. With a grounded supply, the design intent is that the breaker will trip for a fault, and take the hazard offline. For a floating supply, everyone still thinks the same thing, that the breaker will trip. But the design intent is that the breaker will not trip. That's the problem with a floating supply, no one understands it. for a floating supply, the hazard remains on with power and no clue pretty much that any hazard exists. If you have a truly floating supply, you need a ghostbuster to go with it.

If you're here asking if you needs an EGC to distribute power around your plant, you should bring in a really good specialist to go over your system several times surveying, looking for the hazards, and then advising.

Your post is missing a lot of necessary information.
 
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Just a little aside………..

The Delta 240V



This is not something come I across very often.

I’m an old fellow, a Brit, and in my mid seventies. Our usual domestic and commercial arrangement is single phase. It used to be 250V but later versions became 230Vac. Still single phase. For larger industrial systems we have 400V three phase systems with line to neutral at 230V.

But that’s it. No 240V delta. No 277V, no 208V, no 120-120. For us lighting and cooker hobs are all the same. Just simple innit?
 
Yeah, we get to deal with that stuff too, it's a world economy now. 380 to 415 thanks for the additional system and another frequency to boot.

At least the Canuck 600V system to the north retains the same 60Hz.

It's all good once you get it fingered out. You become a transformer collector over time.
 
MTW said:
Yeah, we get to deal with that stuff too, it's a world economy now. 380 to 415 thanks for the additional system and another frequency to boot.

At least the Canuck 600V system to the north retains the same 60Hz.
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415Y would greatly benefit most US buildings. Less copper, less material and no wasteful transformers humming away.
 
Besoeker3 said:
Just a little aside………..

The Delta 240V



This is not something come I across very often.

I’m an old fellow, a Brit, and in my mid seventies. Our usual domestic and commercial arrangement is single phase. It used to be 250V but later versions became 230Vac. Still single phase. For larger industrial systems we have 400V three phase systems with line to neutral at 230V.

But that’s it. No 240V delta. No 277V, no 208V, no 120-120. For us lighting and cooker hobs are all the same. Just simple innit?
Click to expand...

Bes, a personal request. I recall from several years ago you posted a great pdf of the Steinmetz method for the simple pendulum. I did not grab a copy at the time, and have not been able to find that since with Google. If you happen to have access to that pdf and repost it, it would be greatly appreciated. Thank You. I found variations of it, but not the beautiful pdf that you posted.

I tried to find it by going back through the MH old forum posts, but (I recall) the user id changed over the years and that search did not work either. Thank You.

240 Volt delta was sometimes provided as the Utility supply for machine shops of the WWII era, probably red leg delta at the Utility transformer but 3 phase 3 wire at the customer premises. There would be expected to be no 120 V available at the main switch and no neutral connected loads, for the older generation Americam manufactured machine tools, Brown and Sharpe on 240 V delta ... Later generation import motors, 208 V would be expected.
 
__dan said:
Bes, a personal request. I recall from several years ago you posted a great pdf of the Steinmetz method for the simple pendulum. I did not grab a copy at the time, and have not been able to find that since with Google. If you happen to have access to that pdf and repost it, it would be greatly appreciated. Thank You. I found variations of it, but not the beautiful pdf that you posted.

I tried to find it by going back through the MH old forum posts, but (I recall) the user id changed over the years and that search did not work either. Thank You.
Click to expand...

I recall this from the Steinmetz equivalent (electrical) circuit for induction motors but I don't recall mentioning the pendulum here. Of course I know what it is - I'll dig through my notes.
 
mbrooke said:
415Y would greatly benefit most US buildings. Less copper, less material and no wasteful transformers humming away.
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That is the result of Edison's 110V being a legacy system here when Telsa & Westinghouse introduced AC, the rest of the world was in the dark ages, so no limitations.
 
norcal said:
That is the result of Edison's 110V being a legacy system here when Telsa & Westinghouse introduced AC, the rest of the world was in the dark ages, so no limitations.
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I somewhat disagree, at one point have the world was 110-127. Most of those countries have converted out or are in the process of doing so. Once you try 230 volts you don't ever go back- you will seek more of it.
 
mbrooke said:
I somewhat disagree, at one point have the world was 110-127. Most of those countries have converted out or are in the process of doing so. Once you try 230 volts you don't ever go back- you will seek more of it.
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And SI units of course. Just Myanmar, Liberia and the good old US of A remaining.
 
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