SYSTEM GROUNDING (UNGROUNDED AND HIGH IMPEDANCE GROUNDED SYSTEM)

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GoldDigger

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What is the purpose of EQUIPMENT GROUNDING for UNGROUNDED SYSTEM AND HIGH IMPEDANCE GROUNDED SYSTEM?
The EGC provides an assured path to ground to permit proper operation of the ground detector for a single fault. And it provides the fault clearing path in case a second fault occurs in a different location before the first fault is corrected.
 

bobby ocampo

Senior Member
The EGC provides an assured path to ground to permit proper operation of the ground detector for a single fault. And it provides the fault clearing path in case a second fault occurs in a different location before the first fault is corrected.

Other than providing for a ground path for the operation of a ground detector, what else does equipment grounding do for electrical safety of personnel on a single-line-to-ground fault?
 

iceworm

Curmudgeon still using printed IEEE Color Books
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Other than providing for a ground path for the operation of a ground detector, what else does equipment grounding do for electrical safety of personnel on a single-line-to-ground fault?

Assumption: you are discussing 480V systems as opposed to 13.8kV.

L-G faults really are Line to the equipment shell. Capacitive coupling can provide a path for a nasty shock from the equipment shell to ground.

Ungrounded systems can develop what is called an "arcing ground fault". The same capacitive coupling can cause the L-G voltage to rise to several times the normal - breaking down insulation.

HRG prevents both.

Recommend reading appropriate sections of the IEEE Green book (IEEE1100 - I think).



ice
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
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EE (Field - as little design as possible)
Other than providing for a ground path for the operation of a ground detector, what else does equipment grounding do for electrical safety of personnel on a single-line-to-ground fault?

Arggg - I didn't answer your question. You lumped HRG and ungrounded together. My response discussed the differences - which isn't what you were asking.

So, trying again:
Gold pretty well nailed it. I don't have much to add.

However, a couple of questions to nail down exactly what you are asking:
When you say "equipment ground" are you only discussing the connection from the non-current carrying conductive sheet metal parts to earth?

Are you also including the "Equipment Bonding Conductor" that connects all the non-current carrying conductive sheet metal parts?


ice
 

bobby ocampo

Senior Member
Arggg - I didn't answer your question. You lumped HRG and ungrounded together. My response discussed the differences - which isn't what you were asking.

So, trying again:
Gold pretty well nailed it. I don't have much to add.

However, a couple of questions to nail down exactly what you are asking:
When you say "equipment ground" are you only discussing the connection from the non-current carrying conductive sheet metal parts to earth?

Are you also including the "Equipment Bonding Conductor" that connects all the non-current carrying conductive sheet metal parts?


ice

What is the purpose of equipment grounding and equipment bonding in UNGROUNDED AND HIGH RESISTANCE GROUNDED SYSTEM?

Is equipment grounding and bonding for the the detection and operation ONLY of ground detectors?
 

GoldDigger

Moderator
Staff member
Location
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Occupation
Retired PV System Designer
What is the purpose of equipment grounding and equipment bonding in UNGROUNDED AND HIGH RESISTANCE GROUNDED SYSTEM?

Is equipment grounding and bonding for the the detection and operation ONLY of ground detectors?
Mainly. It also serves as a protection if the equipment becomes energized from another grounded source or from lightning induced currents.

It also will discharge static electricity.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
What is the purpose of equipment grounding and equipment bonding in UNGROUNDED AND HIGH RESISTANCE GROUNDED SYSTEM?

Is equipment grounding and bonding for the the detection and operation ONLY of ground detectors?

Q1: Other than that already mentioned, the purpose is the same as for grounded systems.

Q2: No

ice
 

bobby ocampo

Senior Member
Mainly. It also serves as a protection if the equipment becomes energized from another grounded source or from lightning induced currents.

It also will discharge static electricity.

Serves a protection for what? Will a personnel be prevented from electrocution with the equipment grounding and bonding? Does the equipment grounding and bonding ONLY serves as a path for the operation of ground fault detection?
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
Serves a protection for what? Will a personnel be prevented from electrocution with the equipment grounding and bonding? Does the equipment grounding and bonding ONLY serves as a path for the operation of ground fault detection?

bo -
These questions have already been answered.

If you have something specific in mind, or a differing opinion:
What might it/they be?
And what reasons would you have for thinking this?​

ice
 

bobby ocampo

Senior Member
Q1: Other than that already mentioned, the purpose is the same as for grounded systems.

Q2: No

ice

HRG is considered grounded system based on IEEE 142. However unlike solidly grounded there is no immediate trip and low single line to ground fault compared with a solidly grounded system.

Just to refresh us what is the benefit of equipment grounding and bonding for SOLIDLY GROUNDED SYSTEM.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
HRG is considered grounded system based on IEEE 142. However unlike solidly grounded there is no immediate trip and low single line to ground fault compared with a solidly grounded system.

Just to refresh us what is the benefit of equipment grounding and bonding for SOLIDLY GROUNDED SYSTEM.

Okay - You read and do some research. That's good. Your turn. What are your thoughts? I repeat:
If you have something specific in mind, or a differing opinion:
What might it/they be?
And what reasons would you have for thinking this?​


ice
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...
Just to refresh us what is the benefit of equipment grounding and bonding for SOLIDLY GROUNDED SYSTEM.
Not really sure that there is any benefit of equipment grounding in an solidly grounded system but the equipment bonding provides a the fault clearing path and is required for safety.
 

kwired

Electron manager
Location
NE Nebraska
Bonding all non current carrying components together puts them all at same potential whether they are grounded (earthed) or not at some other point in the system.

In any system grounded, ungrounded, high impedance grounded, it is nice to not have the frame of one piece of equipment at a different voltage then the frame of a nearby piece of equipment especially if you can touch both at the same time.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
What is the purpose of EQUIPMENT GROUNDING for UNGROUNDED SYSTEM AND HIGH IMPEDANCE GROUNDED SYSTEM?


Equal potential.

What, would happen if 2 faults occurred in separate machines? Also, since the system is loosely coupled to ground via capacitance, (and a resistor in HRG) a single phase to case fault can stills hock or even kill.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
What is the purpose of equipment grounding and equipment bonding in UNGROUNDED AND HIGH RESISTANCE GROUNDED SYSTEM?

Is equipment grounding and bonding for the the detection and operation ONLY of ground detectors?


Nope, see below. A number of hazards are present without an EGC.



Remember this: all systems need an NEC (or similar standard, ie IEC, BS7671, ect) article 250 grounding and bonding system for a variety of reasons involved with human life safety and property protection. The ONLY difference between a solid ground and an ungrounded system is a bonding jumper from the transformer XO to the grounding system. An HRG is just a bonding jumper with an impedance. All else remains the same in terms of grounding and bonding.
 

bobby ocampo

Senior Member
Bonding all non current carrying components together puts them all at same potential whether they are grounded (earthed) or not at some other point in the system.

In any system grounded, ungrounded, high impedance grounded, it is nice to not have the frame of one piece of equipment at a different voltage then the frame of a nearby piece of equipment especially if you can touch both at the same time.

What will it do if all non-current carrying component are all at the same potential? Any illustration what will happen if they are not at the same potential?

In an ungrounded system, what will happen to a person touching the metal enclosure on a single line to ground fault? Does equipment grounding have to do with the safety of the personnel even if it will not operate the Over-current protective device?

What will happen to a person touching a metal enclosure on a single line to ground fault in a HRG system?Does equipment grounding have to do with the safety of the personnel even if it will not operate the Over-current protective device?
 

bobby ocampo

Senior Member
Nope, see below. A number of hazards are present without an EGC.



Remember this: all systems need an NEC (or similar standard, ie IEC, BS7671, ect) article 250 grounding and bonding system for a variety of reasons involved with human life safety and property protection. The ONLY difference between a solid ground and an ungrounded system is a bonding jumper from the transformer XO to the grounding system. An HRG is just a bonding jumper with an impedance. All else remains the same in terms of grounding and bonding.

The question is what will this bonding do for the safety of personnel if if this bonding will not operate the OCPD in an UNGROUNDED AND HRG SYSTEM on a single line to ground fault?
 

iwire

Moderator
Staff member
Location
Massachusetts
The question is what will this bonding do for the safety of personnel if if this bonding will not operate the OCPD in an UNGROUNDED AND HRG SYSTEM on a single line to ground fault?

It will maintain, or at least try maintain, zero potential between the earth and the items that are experiencing a ground fault.

It really is the same reason for grounding the neutral in the grounded system.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
The question is what will this bonding do for the safety of personnel if if this bonding will not operate the OCPD in an UNGROUNDED AND HRG SYSTEM on a single line to ground fault?

Remove voltage. An ungrounded system is coupled to earth via capacitance. There is no way to get rid of it. Yes Peterson coil systems can reduce that value as well as limited system size, but in an average system capacitive coupling will yielded several hundred milliamps if not several amps. So if a hot wire did touch the case or one was to touch a hot wire voltage and current potential would exist and it would most likely be dangerous.
 
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