What will the voltage be?

[electrofelon]

The reason for my, as to why we ground the electrical system. If I understand it correctly, If the system is not grounded the voltage could be any value, even though capacitive, there is a chance of getting shocked. Now, if the system is grounded the voltage value is stable at 120V and for sure one will get shocked and possibly killed.

Then why do we ground the system? what value does a grounded system offer vs a non grounded system.

They are just different electrical system topologies, and there are advantages and disadvantages to each. Basically whether a system is grounded or ungrounded determines the insulation levels of components, which system conductors get OCPD's, and how faults Are handled.

Advantages of grounded systems:
1. Automatic operation for first faults. Monitoring or knowledgeable people not required (this is probably the biggest one)
2. Solid ground reference holds voltage between components to known and stable levels, thus some circuit components can have less insulation or even be bare.
3. Typically one circuit conductor (the grounded one) does not need an OCPD.
4. Overall, just generally easier to troubleshoot test and work on because of solidly defined voltage between all components and ground.


Disadvantages of grounded systems:
1. Stray current issues
2. High and dangerous fault current levels for first faults.

Advantages of ungrounded systems:
1. Operation can continue after first fault, it just becomes grounded system.
2. No high current faults with high incident energy for first faults.
3. Less stray current issues.

Disadvantages of ungrounded systems:
1. Typically requires knowledgeable individuals and intervention after first faults.
2. Arcing type faults can result in higher than system voltage on components stressing or damaging insulation. Because of this, insulation ratings typically need to be higher than system voltage.

 

[Ponchik]

@ electronfelon

1. Automatic operation for first faults. Monitoring or knowledgeable people not required (this is probably the biggest one)

The OCPD at the service will trip if there is a ground fault down stream from the main disconnect regardless if the utility's transformer has a GEC

 

[Ponchik]

Your body becomes the bonding jumper, not totally different than a high impedance ground. Don't be doing this when another fault occurs.

Whether the utility transformer GEC is present or not, I will get shocked with the 2nd fault.

 

[electrofelon]

@ electronfelon

The OCPD at the service will trip if there is a ground fault down stream from the main disconnect regardless if the utility's transformer has a GEC

If it's an ungrounded system, then no the breaker will not trip on a first ground fault.

I don't really know what you mean by "utilities transformer has a gec", but if I had to interpret that I would say if it has a gec then it is a grounded system

 

[Ponchik]

If it's an ungrounded system, then no the breaker will not trip on a first ground fault.

I don't really know what you mean by "utilities transformer has a gec", but if I had to interpret that I would say if it has a gec then it is a grounded system

The GEC from the utility transformer that bonds the neutra point to the earth.

First, If utility GE is removed, then the system is not grounded, correct?

If the GEC is removed from the building's service then the service has no connection to the earth.
So with the GEC removed from as mentioned, why wouldn't the breaker trip if there is a ground fault down stream from it.

At the service, the neutral i sstill bonded to the case and the there is EGC installed.

 

[electrofelon]

The GEC from the utility transformer that bonds the neutra point to the earth.

First, If utility GE is removed, then the system is not grounded, correct?

If the GEC is removed from the building's service then the service has no connection to the earth.
So with the GEC removed from as mentioned, why wouldn't the breaker trip if there is a ground fault down stream from it.

At the service, the neutral i sstill bonded to the case and the there is EGC installed.

Ok....when you make a grounded system, note that it's not just connecting one of the system conductors to dirt. Much more importantly, you also connect all the metal non-current carrying parts (the equipment grounding system) to it as well (that's what your MBJ or SBJ does).

You wouldn't have a system where one conductor is connected to dirt but nothing else. Conversely, if you had a MBJ/SBJ connection, you would want to make a dirt/ground connection to reference the system to ground potential, although in practice that's going to already happen by the MBJ/SBJ (unless the EGC system truly had no connections to dirt, concrete, steel, piping systems, well casings etc, which would be highly unlikely, at least for a building electrical system.)

 

[ActionDave]

If it's an ungrounded system, then no the breaker will not trip on a first ground fault.

I don't really know what you mean by "utilities transformer has a gec", but if I had to interpret that I would say if it has a gec then it is a grounded system

I've never worked on an ungrounded system but my understanding is the difference between it and a solidly grounded system is the lack of a MBJ.

 

[electrofelon]

I've never worked on an ungrounded system but my understanding is the difference between it and a solidly grounded system is the lack of a MBJ.

Right, pretty much exactly the same other than no MBJ. You still have everything bonding together: raceways and other non-current carrying parts, piping systems, stuff likely to become energized, the local dirt...... "Everything" just doesnt get connected to one of the system conductors .

 

[Ponchik]

The GEC from the utility transformer that bonds the neutra point to the earth.

First, If utility GE is removed, then the system is not grounded, correct?

If the GEC is removed from the building's service then the service has no connection to the earth.
So with the GEC removed from as mentioned, why wouldn't the breaker trip if there is a ground fault down stream from it.

At the service, the neutral i sstill bonded to the case and the there is EGC installed.

I totally agree.

Lets get back to question.

If the utility transformer GEC that bonds the neutral point to the ground and the GEC at the service is removed, will a person get shocked when in contact with the energized wire and the ground?

AFAIK, the current has to flow through the body and back to the source for the person to get shocked. When the GEC from the above example is missing, how the current return back to the source for the person to get shocked?

 

[electrofelon]

I totally agree.

Lets get back to question.

If the utility transformer GEC that bonds the neutral point to the ground and the GEC at the service is removed, will a person get shocked when in contact with the energized wire and the ground?

AFAIK, the current has to flow through the body and back to the source for the person to get shocked. When the GEC from the above example is missing, how the current return back to the source for the person to get shocked?

Most likely you would still get shocked. I'll bet you $10 that even with the grounding electrode conductors disconnected, the system will still be pretty well grounded. All it takes is a box tapconed into a concrete wall, not to mention all the things with egcs that are going to gas lines, water lines, well casings, etc. Now take out the main bonding jumper and we can talk.....

 

[Dsg319]

If the utility GEC from a single pot serving your house was disconnected I would think it would not make much difference at all being that the utility neutral is grounded at multiple other points so the system still remains grounded?

 

[electrofelon]

If the utility GEC from a single pot serving your house was disconnected I would think it would not make much difference at all being that the utility neutral is grounded at multiple other points so the system still remains grounded?

Well depends on a few things. First you have to assume that the primary neutral is connected to the secondary neutral (yes typical on a MGN system). Second, note that there are still many Delta distribution systems around that do not have a neutral / grounded conductor (transformers are fed L-L).

 

[Dsg319]

Well depends on a few things. First you have to assume that the primary neutral is connected to the secondary neutral (yes typical on a MGN system). Second, note that there are still many Delta distribution systems around that do not have a neutral / grounded conductor (transformers are fed L-L).

Yes assuming it is a MGN. Even if the primary neutral didn’t have another earth connection for say a couple thousand feet. I know it depends on soil conditions but I wonder if you would still have a close to 120v from hot to actual earth at the secondary of the transformer.

 

[ggunn]

I totally agree.

Lets get back to question.

If the utility transformer GEC that bonds the neutral point to the ground and the GEC at the service is removed, will a person get shocked when in contact with the energized wire and the ground?

If the neutral point of a wye transformer secondary is left floating I am pretty sure it makes the secondary the same as an ungrounded delta.

 

[electrofelon]

If the neutral point of a wye transformer secondary is left floating I am pretty sure it makes the secondary the same as an ungrounded delta.

Would there be any way to tell? As in any sort of loading or other test that would indicate the actual winding configuration?

 

[Ponchik]

Most likely you would still get shocked. I'll bet you $10 that even with the grounding electrode conductors disconnected, the system will still be pretty well grounded. All it takes is a box tapconed into a concrete wall, not to mention all the things with egcs that are going to gas lines, water lines, well casings, etc. Now take out the main bonding jumper and we can talk.....

^^^ I got a clear picture as to what you described and now I understand it. Thank you.



This is from the Soars book:

"Systems are grounded to limit the voltage to ground during normal operation"
I am assuming "limit" means 120V and 277V and without the GEC the voltage can be anything, correct?

 

[ptonsparky]

^^^ I got a clear picture as to what you described and now I understand it. Thank you.



This is from the Soars book:

"Systems are grounded to limit the voltage to ground during normal operation"
I am assuming "limit" means 120V and 277V and without the GEC the voltage can be anything, correct?

Probably more like the SBJ. I've been to multiple places with no GEC that was still a grounded system with expected voltages.

 

[electrofelon]

^^^ I got a clear picture as to what you described and now I understand it. Thank you.



This is from the Soars book:

"Systems are grounded to limit the voltage to ground during normal operation"
I am assuming "limit" means 120V and 277V and without the GEC the voltage can be anything, correct?

I don't love that wording, specifically "limit". I think they should say something like, ".....to establish consistent voltages to ground."