Equipment Grounding for Ungrounded System

[tryinghard]

I will conduct an experiment on a solidly grounded system but at a reduced voltage of 21voltsY/12 volts. I have already verified importance of connection to ground of the BONDED EGC in UNGROUNDED AND HRG SYSTEM.

Based on science and vector equivalent of electrical system, importance of connection to earth is very important. T

The ground connection is extremely important!

On a grounded system you will not have current (dangerous touch voltage) on the equipment grounding unless the circuit is in violation of NEC. The bonding of equipment to the transformer ensures this, a short will cause the circuit will trip or open, it will be off it?s a direct path from and to the transformer!

On an ungrounded system you will have ?ground detection? (indication/annunciation), if you don?t your circuit is in violation of NEC! According to Mike Holts ?Grounding versus Bonding? and ANSI/IEEE 142, ?One of the dangers of an ungrounded system is that system overvoltages can occur during arcing, resonant of near-resonant ground faults [1.4.2]. ?And, ?Field experience and theoretical studies have shown that arcing, restriking, or vibrating ground faults on ungrounded systems can, under certain conditions, produce surge voltages as high as six times normal.?

Again the above happens when an ungrounded circuit is misused and or in violation.

 

[don_resqcapt19]

The ground connection is extremely important!

On a grounded system you will not have current (dangerous touch voltage) on the equipment grounding unless the circuit is in violation of NEC. The bonding of equipment to the transformer ensures this, a short will cause the circuit will trip or open, it will be off it’s a direct path from and to the transformer!

That statement is not correct for fault conditions on solidly grounded systems. There will be a hazardous voltage between the faulted equipment and other bonded equipment or the earth as long as the fault exists. In theory the time this hazardous voltage is there would be short...the time it takes for the OCPD to clear the fault, but if for some reason the fault is not quickly cleared, the hazard will exist until the fault is cleared.

 

[don_resqcapt19]

The case of the ship will serve us the earth and all bonded EGC will be connected to the structure of the ship or airplane.

This is still the same as the connection to the earth. Under fault conditions on a solidly grounded system there will be a voltage from the faulted equipment to the structure. This voltage will be equal to the voltage drop on the EGC between the point of the fault and the main or system bonding jumper. The only way to get rid of this voltage is to clear the fault. Even with an EGC sized per 250.122, the voltage may be in the hazardous range.

 

[benaround]

When I was a kid I almost drown while swimming, but this thread got that beat.

 

[coulter]

bobby 0 -
As has been mentioned, it's important to distinguish between ground and bonding. IEEE and NEC don't always do a real good job at that. As you know, often one must take the section under discussion and apply the context to under which they mean.

You may have forgotten the first part sir. Please quote "a" ...

Nope I didn't forget. I read both the first and second sentence and took it in context.

... I will appreciate if you can email a copy so I can answer you or please try to quote the complete provision of that specific artilce or section in 142. ...

It's copywrited. I'll get the two sections. However, that could leave out context necessary for understanding.

2.1.2 General​

The term​

equipment grounding includes the equipment grounding conductor (EGC) and refers to the interconnection (bonding) and grounding of the nonelectrical metallic elements of a system. The term​

system grounding​

(as covered in Chapter 1) may include a grounded conductor and is part of the power distribution system. The need for an EGC exists for high-impedance, low-impedance, and effectively grounded systems as well as for ungrounded systems. Examples of components of the equipment grounding system are metallic raceways, motor frames, equipment enclosures, and a grounding conductor (wire). The requirements for equipment grounding are expressly specified in the National Electrical Code ? (NEC?) NFPA 70​

1​

​

as follows:​

a) Conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage tocground on these materials. Where the electrical system is required to be grounded, these materials shall be connected together and to the supply system grounded conductor.
b) Where the electrical system is not solidly grounded, these materials shall be connected together in a manner that establishes an effective path for fault current.
c) Electrically conductive materials that are likely to become energized shall be bonded to the supply system grounded conductor or, in the case of an ungrounded electrical system, to the electrical system grounded equipment, in a manner that establishes an effective path for fault current.
d) The earth shall not be used as the sole EGC or fault current path. The basic objectives of an equipment grounding system are the following:
1) To reduce electric shock hazard to personnel.
2) To provide adequate current-carrying capability, both in magnitude and duration, to accept the ground-fault current permitted by the overcurrent protection system without creating a fire or explosive hazard to building or contents.
3) To provide a low-impedance return path for ground-fault current necessary for the timely operation of the overcurrent protection system.​

1.3 Purposes of system grounding
System grounding is the intentional connection to ground of a phase or neutral conductor for the purpose of:

a) Controlling the voltage with respect to earth, or ground, within predictable limits,

b) Providing for a flow of current that will allow detection of an unwanted​

connection between system conductors and ground. Such detection may then initiate operation of automatic devices to remove the source of voltage from these conductors.​

The NEC prescribes certain system grounding connections that must be made to be in compliance with the code. The control of voltage to ground limits the voltage stress on the insulation of conductors so that insulation performance can more readily be predicted. The control of voltage also allows reduction of shock hazard to persons who might come in contact with live conductors.​

...You can experiment a Bonded EGC not connected to earth in an UNGROUNDED AND HRG SYSTEM. There will be a potential equal to the line to neutral voltage of the system. Or potential will be equal to line-to-line divided by 1.732. After the experiment tell us if connection to earth is not important.

I'm usually pretty good at the physics and generally pretty good at translating discussion. But this one leaves me a bit baffled. I have no idea what a "bonded EGC not connected to earth" is.

Tell you what: I'll make another stab at this right after you answer my request for you to perform the breadbox thought experiment.

carl

 

[coulter]

Yuk - those ieee quotes were a mess to copy. Sorry for the slop.

bobby, you got to get a new copy.

carl

 

[tryinghard]

That statement is not correct for fault conditions on solidly grounded systems. There will be a hazardous voltage between the faulted equipment and other bonded equipment or the earth as long as the fault exists. In theory the time this hazardous voltage is there would be short...the time it takes for the OCPD to clear the fault, but if for some reason the fault is not quickly cleared, the hazard will exist until the fault is cleared.

If it's not extremely short its most likely not an effective ground fault path, and that will be a violation.

 

[don_resqcapt19]

If it's not extremely short its most likely not an effective ground fault path, and that will be a violation.

There could be any number of reasons including a defective OCPD, but my point is that neither grounding nor bonding will remove this voltage and it will be there until the fault is cleared.

 

[tryinghard]

There could be any number of reasons including a defective OCPD, but my point is that neither grounding nor bonding will remove this voltage and it will be there until the fault is cleared.

True.......

 

[bobby ocampo]

This is still the same as the connection to the earth. Under fault conditions on a solidly grounded system there will be a voltage from the faulted equipment to the structure. This voltage will be equal to the voltage drop on the EGC between the point of the fault and the main or system bonding jumper. The only way to get rid of this voltage is to clear the fault. Even with an EGC sized per 250.122, the voltage may be in the hazardous range.

Most ship that I have been are mostly ungrounded system or HRG.

 

[bobby ocampo]

bobby 0 -
As has been mentioned, it's important to distinguish between ground and bonding. IEEE and NEC don't always do a real good job at that. As you know, often one must take the section under discussion and apply the context to under which they mean.

Nope I didn't forget. I read both the first and second sentence and took it in context.

Sorry Sir don't understand what you mean that IEEE and NEC don't always do a real good job.

It's copywrited. I'll get the two sections. However, that could leave out context necessary for understanding.

I am waiting for my copy I bought already. I can easily answer if you can cut and paste 142 2.1.1 of the book.

I'm usually pretty good at the physics and generally pretty good at translating discussion. But this one leaves me a bit baffled. I have no idea what a "bonded EGC not connected to earth" is.

Tell you what: I'll make another stab at this right after you answer my request for you to perform the breadbox thought experiment.

carl​

Ok sir. please wait and I will email you the result.

Originally Posted by ieee142

2.1.2 General
The term equipment grounding includes the equipment grounding conductor (EGC) and refers to the interconnection (bonding) and grounding of the nonelectrical metallic elements of a system

This provisin of the IEEE/ANSI standards says that Bonding and grounding is of equal importance.

Originally Posted by ieee142
The basic objectives of an equipment grounding system are the following:
1) To reduce electric shock hazard to personnel.
2) To provide adequate current-carrying capability, both in magnitude and duration, to accept the ground-fault current permitted by the overcurrent protection system without creating a fire or explosive hazard to building or contents.
3) To provide a low-impedance return path for ground-fault current necessary for the timely operation of the overcurrent protection system.

First objective is to reduce electric shock to pesonnel and this can be done through the connection of the bonded EGC to the ground or earth. This is true with HRG which is a grounded system, Ungrounded system and surely with solidly grounded system too.​

 

[iwire]

First objective is to reduce electric shock to pesonnel and this can be done through the connection of the bonded EGC to the ground or earth.

Try Carl's experiment.

Bonding an electrical system to a giant resistor (the earth) has little effect unless your standing on the earth very close to that connection to earth.

 

[tryinghard]

...First objective is to reduce electric shock to pesonnel and this can be done through the connection of the bonded EGC to the ground or earth...

Exactly how so?

 

[don_resqcapt19]

First objective is to reduce electric shock to pesonnel and this can be done through the connection of the bonded EGC to the ground or earth. This is true with HRG which is a grounded system, Ungrounded system and surely with solidly grounded system too.

How does a connection to earth reduce the shock hazard when you have a fault in a solidly grounded system?

 

[don_resqcapt19]

Sorry Sir don't understand what you mean that IEEE and NEC don't always do a real good job.

There is a huge amount of confusion in the industry about bonding and grounding and what each actually does and what each actually is. The NEC has taken a baby step to correct this, but it still has a long way to go as does the IEEE Green Book and most other sources of information on grounding and bonding. At this point the Soare's book on grounding along with Mike Holt's book are probably the best there are.
The confusion on what grounding does has resulted in a number of deaths in the recent past. Often because of energized light poles or manhole covers. In these cases there was only an connection to earth, not the required EGC. These installations are made because there are many who believe that a connection to earth on a solidly grounded system will eliminate the shock hazard.

 

[bobby ocampo]

The confusion on what grounding does has resulted in a number of deaths in the recent past. Often because of energized light poles or manhole covers. In these cases there was only an connection to earth, not the required EGC. These installations are made because there are many who believe that a connection to earth on a solidly grounded system will eliminate the shock hazard.

Again, Both should be done. Both connection to earth and bonding EGC. If there are many incidents of people grounded in poles and manholes a grounding mat bonded and connected to earth should be installed.

Another solution to reduce arc flash hazard is using High Resistance Grounded but use line-to-line voltage not line-to-neutral voltage. There is NO arc flash hazard in a High Resistance Grounded system on a single-line-to-ground fault. Electic shock hazard is also reduced if EGC is bonded and connected to earth. Both are important.

The IEEE 142 said to reduce shock hazards not eliminate.

 

[bobby ocampo]

At this point the Soare's book on grounding

What is the complete name of Soare's book on grounding?

 

[roger]

What is the complete name of Soare's book on grounding?

You can buy it HERE

Roger

 

[bobby ocampo]

Try Carl's experiment.

Bonding an electrical system to a giant resistor (the earth) has little effect unless your standing on the earth very close to that connection to earth.

If by standing near to the connection to the ground may reduce the electric shock hazard then it means that connection to the earth is also as important as compared if it is not connected to the earth. However It is also as important to bond the EGC to trip the OCPD in a solidly grounded system and Low resistance grounded system due to arc flash hazard if one of the current carrying conductor will accidentaly or intentionaly touch a non conducting metal part due to a single line to ground fault. Bonding EGC is also important to have equipotential to all the bonded metal piece in the system and the ground.

Again BOTH should be important. Bonding and and connection to ground. Saying that they have relative importance is hazardous.

 

[Buck Parrish]

What is the complete name of Soare's book on grounding?

2008 Soare's Book on Grounding and Bonding 10th addition.


Have you ever installed an electric fence for animals?
You have to put two ground rods in at every thirteen hundred feet with the grd. wire attached. It's amazing that the electrons will travel through the animal back to the source.
It is reccomended if the soil is real dry. To moisten the soil.