GF indicator lights for delta xfmr secondary

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dbuckley said:
I would invite the poster to place himself between a phase and ground in each of the two situations, and it will become immediately obvious there is a difference :)

Ok, placing yourself may be painful, try a wiggy.
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I have posted an IEEE reference that defines what a resistance grounded system is. Ungrounded delta "ground detector" resistors wired in a grounded wye configuration do not meet that description.
 
Ok, I'll try not to be humourous, since that didn't work, despite the fact it illustrates exactly the issue being faced.

I agree that the otherwise ungrounded system with the bulb monitoring arrangement does not meet the IEEE definition of a resistance grounded system, but, it is clear the system is is not ungrounded, as there is a measurable resistive connection between a phase line and ground. In fact, Lubich argues (link, PDF) that an ungrounded system is a "misnomer", on the basis that even if there isn't a resistive connection, then capacitance exists, and that provides enough of a current flow for reliable detection.

So what is it?

In Europe it would make the qualification of an IT system, as IT is allowed to have a "high resistance" path to ground, and more importantly, it wouldn't make the definition of a TN-something or TT, which has a direct bond to ground.
 
jim dungar said:
So, while the resistance is in parallel with the system capacitive coupling the circuit behaves more like a resistor than a capacitor.

But in an ungrounded delta system with the ground detectors in parallel with the system coupling capacitance the system the circuit still behaves more like a capacitor than a resistor. If it didn't we could mitigate the typical ungrounded overvoltage problems simply by adding resistors.
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I agree, and that is exactly why I placed the term 'resistance grounded' in sneer quotes and described the issue with capacitive overvoltage.

However, I am quite certain that if low enough value resistors were used, then they would mitigate such overvoltages. But we are not talking about small indicator lights here; we are talking resistances in the 10-100 ohm range, dissipating many kW.

-Jon
 
zog said:
Yep, thats it, because it is pretty. That must be the basis behind the ANSI/IEEE standard.
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So explain it.

Why is what I suggested unsafe?

Assume I would use proper OCP and keep in mind the avaible short circuit current will not be high in this application.

Not every industrial site is at the level you are used to dealing with.

A tank is a safer vehicle then a car to drive on the street, that does not make the car a bad choice.
 
iwire said:
So explain it.

Why is what I suggested unsafe?

Assume I would use proper OCP and keep in mind the avaible short circuit current will not be high in this application.

Not every industrial site is at the level you are used to dealing with.

A tank is a safer vehicle then a car to drive on the street, that does not make the car a bad choice.
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IEEE Red Book
 
iwire said:
Very helpful, glad to have you around. :rolleyes:
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Sure, no problem. I am simply providing a reference to the proper design of this system as it should be used on industrial power systems. You can jury rig anything you want.
 
I provided a description of a proper ground detector circuit and a schematic. What do you want me to do, post the whole red book? Why dont you just look at it. You guys are so quick to post pictures of hack jobs in homes that dont follow the NEC (Which by the way in NFPA 70, not NEC 70) but when it comes to industrial you just like making things up on the fly.

DO you even own a copy of the IEEE P141?, "Recommended Practice for Electric Power Distribution for Industrial Plants" (Or red book, as it is refer to)??? Is that the problem here? Any EC that claims to do industrial work certianly must be familiar with the red book.
 
winnie said:
I agree, and that is exactly why I placed the term 'resistance grounded' in sneer quotes and described the issue with capacitive overvoltage.

However, I am quite certain that if low enough value resistors were used, then they would mitigate such overvoltages. But we are not talking about small indicator lights here; we are talking resistances in the 10-100 ohm range, dissipating many kW.

-Jon
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Resistor banks like you describe create an artificial neutral. I have seen designs for small systems using 3.9k Ohm resistors but these were only for fault detection and troubleshooting. Often, the best way to mitigate many problems associated with an ungrounded wye is to use a zig-zag grounding transformer.

Ungrounded systems are often mis-understood (i.e. coupling capacitance and charging current) this results in confusion from people taking general electrical terms and not realizing the actual context in which they are being used.
 
zog said:
I provided a description of a proper ground detector circuit and a schematic.
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That was not my question.

I simply asked what was unsafe about a common installation.

I assumed you would be able to tell me something I did not know.


DO you even own a copy of the IEEE P141?, "Recommended Practice for Electric Power Distribution for Industrial Plants" (Or red book, as it is refer to)???
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No, I do not own it, I have not seen it.

That is probably why I asked if you could tell me what was unsafe about my suggestion.

Any EC that claims to do industrial work certianly must be familiar with the red book.
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That is a bunch of bull, there are many levels of 'industrial'.

Step off your high horse, be helpful or don't bother.
 
Be helpful? Are you kidding me? I think I am the one offering the OP the most help. I think it is absurd that you are giving advice on a system like this in an industrial power system and you have never seen the Red Book.

What would you think about someone giving advice about wiring a residential or commercial system that has never heard of or seen the NEC? It is the same thing.

I am not here to determine the safety level of your jury rigged ground detector rig, I am here to answer the OP question.
 
weressl said:
When you connect a phase to the ground via a lamp(resistor) you would call that a...............?????????
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(All in one breath) An ultra-high super duper resistance grounded arrangement in which capacitive charging current is much larger than the resistive current through the lamps...system. (big breath in) ;)

I think that zog's way of doing it is preferred, but I don't really see anything dangerous about iwire's way either. The IEEE red book is a performance standard and not a safety manual...and yes, I do own a copy.;)
 
zog said:
Be helpful? Are you kidding me? I think I am the one offering the OP the most help.
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You have offered little here in this thread, you did provide the name of a standard that is used.

You did find time to make fun of the poster.

zog said:
What is his budget, 4 bucks? Geez, we scrap PT's for the copper, they are cheap.
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I think it is absurd that you are giving advice on a system like this in an industrial power system and you have never seen the Red Book.
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Again, you seem to have just one vision of what industrial power systems are. There are many differences.

I am not here to determine the safety level of your jury rigged ground detector rig, I am here to answer the OP question.
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It is not 'my jury rigged system' it is a system that has been used longer then either of us has been alive.

If you don't like it thats fine, but if your going to put it down do so with more ammo then 'this system is better, it's in the red book'
 
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next thing I know, zog is going to have me wearing shoes and installing indoor plumbing. all those years I wasted in the paper industry without owning a "red book" .. glad my supervisors did not recognize in ineptitude :roll:
no doubt his design may be more "proper" and I know this doesn't make it "right", but there are many, many plants in this area with the old "light bulb" detection system
 
iwire said:
You have offered little here in this thread, you did provide the name of a standard that is used.
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I offered a proven system that is used all over industrial plants, a schematic, and advice on a sound safe solution, not sure what your problem is.

iwire said:
You did find time to make fun of the poster.
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Hardly, if your budget is $4 for a ground detecter system, you have problems.
 
augie47 said:
next thing I know, zog is going to have me wearing shoes and installing indoor plumbing. all those years I wasted in the paper industry without owning a "red book" .. glad my supervisors did not recognize in ineptitude :roll:
no doubt his design may be more "proper" and I know this doesn't make it "right", but there are many, many plants in this area with the old "light bulb" detection system
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You were an engineer in a paper mill and didnt own a red book?

My recomendation WAS an old light bulb method but there is more to it than just "hook up 3 light bulbs phase to ground". I have never seen a system like that in use.
 
zog said:
You were an engineer in a paper mill and didnt own a red book?

My recomendation WAS an old light bulb method but there is more to it than just "hook up 3 light bulbs phase to ground". I have never seen a system like that in use.
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yep!

drive across the State line to TN. :)
 
zog said:
YOU USE PT's!!!
...
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zog -
Just a question, not adversarial. What would be the advantage of using PT's over transformered 480V incandescant pilots? They have been suggested by several, as far back as post 7.

carl
 
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