Addressing Ground Fault Issues - Page 2 - Electrician Talk - Professional Electrical Contractors Forum

aphase08 · 09-24-2008, 05:21 PM

I have a quick question? Can we install a ground wire on the exterior of a cable to create a isloated ground? We currently have romex feeding outlets but we may need to install isolated ground receptacles in order to keep electromagnetic interference in check.
Any Help?

rj_cavalier · 01-04-2009, 05:18 PM

i have a serious ground fault issue i need help with. had an electrical fire caused by a falling branch on the service of the home. power was fed through the ground wired of the home melting several, catchin the a/c on fire, and blowing out lights. if no damage seems to be apparent on some circuits, should they still be changed to prevent long term issues?

davehufsted · 01-06-2009, 02:06 PM

What a great post, very helpful infomation

shunt trip · 01-15-2009, 08:23 PM

Well written information.

perthman33 · 03-05-2009, 09:06 PM

G'day mate!

Just wanna say well done on your brilliant posting. It help clears up some misconceptions...

Cheers,

Down Under Sparky....

Veritask Electrics Pty Ltd
Perth, Australia

zappy · 03-10-2009, 12:02 AM

I had a couple of questions. 1. I noticed you said phase to phase touching is not a bolted fault? I thought that was a bolted fault? 2. I noticed on the gfpe that the dial said from .1 seconds to 1.0 seconds, why would anyone want to set it to 1.0 seconds?

brian john · 03-10-2009, 11:01 PM

Quote:

Originally Posted by zappy

1. I noticed you said phase to phase touching is not a bolted fault? I thought that was a bolted fault?

Phase's touching is not a bolted fault, a bolted fault would be two phase BOLTED together, such as parallel feeders with two conductors from different phases crossed and connected.

2. I noticed on the GFPE that the dial said from .1 seconds to 1.0 seconds, why would anyone want to set it to 1.0 seconds?[/quote]

In attempt to coordinate with downstream devices, risking additional damage to the distribution system.

zappy · 03-12-2009, 02:53 PM

Quote:

Originally Posted by brian john

Phase's touching is not a bolted fault, a bolted fault would be two phase BOLTED together, such as parallel feeders with two conductors from different phases crossed and connected.
What is it called then when two different phase's touch? Just a fault?
2. I noticed on the GFPE that the dial said from .1 seconds to 1.0 seconds, why would anyone want to set it to 1.0 seconds?

In attempt to coordinate with downstream devices, risking additional damage to the distribution system.[/quote]

What is it called when two different phases touch? Just a fault?

brian john · 03-12-2009, 03:27 PM

Quote:

Originally Posted by zappy

In attempt to coordinate with downstream devices, risking additional damage to the distribution system.

What is it called when two different phases touch? Just a fault?[/quote]

phase to phase fault.

Arcing ground faults are so devestaing due to the impednace of the arc and the voltage levels that permit the arc to maintain. These are burning arc faults and can in a split second totally fry busway, switchborads and feeders without tripping the overcurrent protection. The fault levels are in the low current range hence the NEC requirement for 1200 amp max.

lazer · 03-13-2009, 05:51 PM

in the uk we fit an earth rod with an apropriate rccd prpotection star system find more help at www.mylocalelectrician.co.uk

brian john · 03-13-2009, 06:11 PM

In the states several systems are utilized, what you described is a ground return method, we install a Current Transformer on the main neutral ground bond this system is called the ground return method. Then there is the zero sequence in which a large window current transformer encompasses all phase conductors and the neutral/grounded conductor. Lastly the residual method comprised of 4 current transformers one on each phase and the neutral/grounded conductor. This is mandated ONLY on systems 250 volts to ground and higher and above 1000 amps (typically 480/277 VAC).

Better Electrician · 04-06-2009, 08:45 PM

Very interesting, I had know idea that ground fault protection has been
around since the 70's.

Vick1311 · 04-08-2009, 10:03 PM

I'm new to this thread business and can't seem to figure out how to ask a question...perhaps because I keep alcohol in the house! I'm not an electrician by trade, however I have limited training as one. I am trying to power an antenna with an i/o box requiring 1 phase 230 v ac. I am working with 208v off of a wye configured transformer. I intend to wire this antenna with 2 hot legs from my power source and cap the third hot leg. I am wondering if this will cause any problems...antenna az/el motor performance issues. The motors on the antenna are 3 phase 220 v and are fed from the aforementioned 1 phase 230 v power box. I assume this power is rectified within the box to power the motors. This post may be vague but would appreciate any replies.

shelly50 · 05-11-2009, 08:00 PM

I have a simple question on ground rods. At work we recently had a guest instructor tell us the way to megger a ground rod was from the panel neutral to the rod. He said we should get over 400megohm reading between the 2. This does not seem correct to me. What is the correct way to megger a rod and what is the correct ohm reading.

brian john · 05-11-2009, 10:28 PM

Shelly:

Not only is he wrong he is dead wrong. I can't imagine where he read, heard or was taught this.

Read this and print a copy for him

http://www.aemc.com/techinfo/techwor...GROUND-WEB.pdf