The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Son of Sparky
by HotLine1
Yesterday at 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
230 or 345 kV transmission lines?
by annemarie1
10/12/16 01:23 PM
Is this a fix or just a bandaid?
by gfretwell
10/10/16 06:49 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 11
renosteinke 6
HotLine1 6
ghost307 5
sparky 4
Who's Online
0 registered (), 107 Guests and 7 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#128197 - 09/16/02 08:13 PM Ground resistance - fall of potential method
Ron Offline

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
I am trying to find information about the location of reference rod placement for measuring ground resistance using the fall of potential method. Someone mentioned IEEE 81, but I do not have a copy. Does it has procedures for doing the emasurment, like NETA has for breaker and cable testing etc.

#128198 - 09/17/02 06:53 AM Re: Ground resistance - fall of potential method
JBD Offline

Registered: 07/12/01
Posts: 599
Loc: WI, USA
It appears there are no standards.

According to a technical bulletin I have from AEMC Instruments:

{First some terms, for Fall Of Potential ground resistance testing, three points are used: X is the ground electrode under test; Y is the auxiliary potential electrode (sometimes called P); and Z is the auxiliary current electrode (P).}

"The goal in precisely measuring the reistance to ground is to place the ...Z electrode far enough from the ground electrode under test so that ... Y will be outside of the effective resistance areas... The best way to find out... is to move [Y] ... and take a reading at each location... The readings taken should be relatively close to each other..."
"No definite distance between X and Y can be given, since this distance is relative to [many factors]..."

#128199 - 09/17/02 11:10 AM Re: Ground resistance - fall of potential method
Bjarney Offline

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
IEEE 81 IS the standard, in the US anyway, but it covers a lot of territory.

#128200 - 09/17/02 03:22 PM Re: Ground resistance - fall of potential method
pauluk Offline

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
You might like to follow some of the links posted in this thread as well.


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals