Grounding electrode conductor question

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317arc

Member
Why are grounding electrode conductors used ?

a. to eliminate fault currents
b. to provide a high resistance path to ground
c. to signal a alarm
d. to operate overcurrent protection

This is a test question that I missed on a NEC practice exam and it is worded exactly this way on the practice exam.

* I thought (a) would be correct but it was not .
 

roger

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None of the choices would be a correct answer.

Roger
 

tryinghard

Senior Member
Location
California
All choices are wrong, but b. can be corrected!

b. to provide a high low resistance path to ground.

250.4(A)(1) says ?Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.? This is grounds purpose; its conductor must contribute integrally.

It is not a good route for fault current, 250.4(A)(5) ??The earth shall not be considered as an effective ground-fault path.? Therefore cannot be use as such, 250.4(A)(3).
 

raider1

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I thought grounds were used to provide a path of low resistance path to ground for fault currents.

Here is what the NEC says about the reasons for "grounding" an electrical system.

250.4 General Requirements for Grounding and Bonding.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

The earth can't be used as a ground fault current path. Take a look at 250.4(A)(5).

(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.

Chris
 

roger

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I thought grounds were used to provide a path of low resistance path to ground for fault currents.

Actually that would be the purpose of Bonding, the "Grounding Electrode Conductor" just connects the system to earth for the reason posted by Chris above.

The wording of the question would not have anything to do with "Bonding" and there is no best answer, the choices are all wrong answers.



Roger
 

220/221

Senior Member
Location
AZ
Why are grounding electrode conductors used ?


E) To connect the GE to the service.

The GE wouldn't be of any use without the GEC




It probably B)........ with a high/low typo.
 
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crossman gary

Senior Member
120 volt circuit goes to earth do you really think the OCPD will open?:-?

What size OPCD? One of those little glass fuses at 1/100 of an amp?:wink:

Of course, under 600 volts could be a corner grounded 480 volt delta. Contact of the circuit to earth could be 100 feet of copper wire buried in the same ditch as the copper waterpipe electrode.... and we just had 10" of rain in a 3 hour period and the black clay is fully saturated with water. I'm betting a 20 amp breaker would trip.

But of course, under more realistic soil and circuit conditions, the OCPD won't trip on contact with earth. But still, this black gumbo clay down here is darned conductive when wet. Never say never.

I guess some experiments are in order.
 

317arc

Member
This is an actual exam question that is on the Texas Masters !

I paid to review the exam questions and I found about 10 questions that did not have a logical answer to choose from. (typos)

I failed by 1 point and I am protesting .
 

roger

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Retired Electrician
This is an actual exam question that is on the Texas Masters !

I paid to review the exam questions and I found about 10 questions that did not have a logical answer to choose from. (typos)

I failed by 1 point and I am protesting .

You should protest, given that this is an NEC test and the correct answer (as far as the choices are concerned) can not be found in the NEC the test is bogus.

Roger
 

tryinghard

Senior Member
Location
California
This is an actual exam question that is on the Texas Masters !

I paid to review the exam questions and I found about 10 questions that did not have a logical answer to choose from. (typos)

I failed by 1 point and I am protesting .

A worthy move! This question in glaringly wrong.
 
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