GF indicator lights for delta xfmr secondary

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weressl said:
The lamps connected in such fashion make this a resistance grounded system.

Use the corner ground if you still work with a stone ax to gather your food....right after you filled out your Geico form.:D
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LOL, you're brutal
 
Up until the 2005 edition the NEC did not require ground detection/indication. So many if not most ungrounded systems were installed without this feature for almost 100 years.

Adding wye connected ground detection schemes that contain resistance does not create "resistance grounded" delta power systems as the term is normally used. At best you could say that these resistors create an artificial neutral point.
 
jim dungar said:
Up until the 2005 edition the NEC did not require ground detection/indication. So many if not most ungrounded systems were installed without this feature for almost 100 years.

Adding wye connected ground detection schemes that contain resistance does not create "resistance grounded" delta power systems as the term is normally used. At best you could say that these resistors create an artificial neutral point.
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True, but Bob asked the lamps' why point to be connected to ground which MADE it a resistance grounded system.

To split hairs even further your so called artificial neutral would not be a neutral since there is a load inserted between the voltage source and the grounding point
 
Clearly the lights are resistors and provide a connection to ground via the resistance, so the system _is_ 'resistance grounded'.

But such inadvertent resistance grounding probably has too high a resistance to provide the core benefit of an intentional resistance grounded system.

In an intentional resistance grounded system, the grounding resistance is selected to prevent capacitive charging effects from causing excessive phase to ground voltages in the event of an intermittent ground fault. In an ungrounded system, these capacitive charging effects can result in phase to ground voltages well in excess of the normal phase to phase voltage.

I do not believe than any normally sized ground fault indicator lights would pass enough current to prevent these excessive voltages.

-Jon
 
YOU USE PT's!!!

What is the big mystery here? This is common stuff for industrial plants, there is no connection to ground in the system so the resistance of the light dosent matter, the groung connection is only made in the ground detector circuit.
 
There are a number of ungrounded systems in the industrial facilites in this area and almost all have the "lamp" arrangement with "A" lamps. These are usually mounted in a conspicious place so they will draw attention to all the maintenance personnel when one phase does go to ground.
 
weressl said:
True, but Bob asked the lamps' why point to be connected to ground which MADE it a resistance grounded system.
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If the wye point is not grounded the device will not function as a ground detector.

To split hairs even further your so called artificial neutral would not be a neutral since there is a load inserted between the voltage source and the grounding point[/quote] It is called an artificial nuetral because it is not a real neutral.

Could you provide any reference that supports your claim that detectors connected in this manner change an ungrounded delta distribution system into a resistance grounded system?
 
iwire said:
That is one way to do it.

The OP is trying to meet code requirements while on a budget.
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Thats the only way to do it RIGHT. What is his budget, 4 bucks? Geez, we scrap PT's for the copper, they are cheap.
 
jim dungar said:
If the wye point is not grounded the device will not function as a ground detector.

To split hairs even further your so called artificial neutral would not be a neutral since there is a load inserted between the voltage source and the grounding point
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It is called an artificial nuetral because it is not a real neutral.

Could you provide any reference that supports your claim that detectors connected in this manner change an ungrounded delta distribution system into a resistance grounded system?[/quote]

As I said Bob called for grounding the common points of the lights to be connected to ground. When you connect a phase to the ground via a lamp(resistor) you would call that a...............?????????

IMO the a delta system ground fault indicating light WYE does not need to be connected to ground in order to function.
 
weressl said:
IMO the a delta system ground fault indicating light WYE does not need to be connected to ground in order to function.
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I agreed with your comment about the resistive ground thing, but I disagree with the above. For the wye lights to detect a ground, the center of the wye must be bonded/grounded to the noncurrent carrying metallic parts of the system.
 
weressl said:
IMO the a delta system ground fault indicating light WYE does not need to be connected to ground in order to function.
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Sure would like to see that drawn out.

I do not see it working as an indicator without a ground reference.

Sure the lights will light ..... but they will remain unchanged when a ground fault happens.
 
winnie said:
Clearly the lights are resistors and provide a connection to ground via the resistance, so the system _is_ 'resistance grounded'.
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Not according to IEEE 141-1993 (the Red Book) chapter 7.2.2.
"Resistance-grounded systems employ an intentional resistance between the electric system neutral and ground."

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.
 
zog said:
Thats the only way to do it RIGHT. What is his budget, 4 bucks? Geez, we scrap PT's for the copper, they are cheap.
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Try $400 bucks for parts only, not including labor. Is that what you consider cheap? Would you like to donate to a good cause?
 
jim dungar said:
Could you provide any reference that supports your claim that detectors connected in this manner change an ungrounded delta distribution system into a resistance grounded system?
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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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