Ground resistance of horizontal conductor encased in concrete
Ground resistance of horizontal conductor encased in concrete
(OP)
Hi!,
I am looking for calculation formula for ground resistance of horizontal conductor encased in concrete. There is a formula in Ieee80-2000 for the vertical ground rod. Appreciate if some one help me.
Thanks,
Kani
I am looking for calculation formula for ground resistance of horizontal conductor encased in concrete. There is a formula in Ieee80-2000 for the vertical ground rod. Appreciate if some one help me.
Thanks,
Kani






RE: Ground resistance of horizontal conductor encased in concrete
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Ground resistance of horizontal conductor encased in concrete
RE: Ground resistance of horizontal conductor encased in concrete
Too many variables including the moisture content of the soil and the amount of doping of the soil by the concrete.
If you do find a formula, please share it with us.
Thanks in advance.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Ground resistance of horizontal conductor encased in concrete
Re=ro/pi()/l*(ln(2*l/b)-1) from:
file:///C:/Users/user/Downloads/158_HVDC%20Ground%20Electrode%20Design.pdf
In my opinion, you may at first consider concrete res.=earth resistance.
Second you may consider the resistance of the concrete 0 and increase the conductor diameter up to diameter of concrete.
1)Let's say ro=100 ohm.m; h=2.5 ft[0.762m]; d=1/2"=0.0127m; b=sqrt(d*h)=0.0984m;length=20’=6.1m
[roconc=ro=100 ohm.m]
R1[without concrete]=100/3.1415/6.1*(ln(2*6.1/0.0984)=2.27 ohm
2) Let's say ro=100 ohm.m; h=2.5 ft[0.762m]; dc=1/2"+2*2”=4.5”=0.0635m ; bc=sqrt(d*h)=0.22m
length=6.1 m;[roconc=0]
R2=100/3.1415/6.1*ln(2*6.1/0.22)=1.99 ohm
2.27/1.99=1.14
That means only 14% error maximum and in conditions on which the resistivity measurements are it is a sufficient accuracy.
RE: Ground resistance of horizontal conductor encased in concrete
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Ground resistance of horizontal conductor encased in concrete
This could be useful for medium and high resistivity soils
I hope this help.
RE: Ground resistance of horizontal conductor encased in concrete
Second, the formula in BS7430 CH.10.3[or Annex A] Horizontal strip or round conductor electrodes is the close to EPRI EL-2020 ELECTRODE TYPES AND CONFIGURATIONS.
As per cooky2000 attachment :
R=ro/2/pi()/L*(ln(2*L^2/w/h)-1) 13.6
BS7430 ch.10.3 or Annex A:
R=ro/P/pi()/L*(ln(2*L^2/w/h)+Q)
where for linear round wire P=2 and Q=-1.3 [Table 5]
By-the-way Q=-1 it is only for strip and not for round.
EPRI EL-2020 [equation 7-9]:
Re=ro/pi()/L*(ln(2*L/sqrt(w/h)-1)
[The difference is from 0.11% for 20 ft to 0.06% for 300 ft.]
RE: Ground resistance of horizontal conductor encased in concrete
7anoter4, your reference to Table 5 for P and Q. I checked BS7430, but i couldn't find the values. Please let me know more detail of the reference table.
Thanks,
Kani
RE: Ground resistance of horizontal conductor encased in concrete
BS7430/1998 [© BSI 05-1999] page 15/16 and Annex A connected with Table 5.
In new BS7430/2011 Ch. 9.5.5 Strip or round conductor electrodes
it is shown an other formula:
Rat=ro/(2*pi()*L)*ln(L^2/1.85/h/d) [in excel format].
but it still exist in new Annex B -page 87.
Never-the-less no indication of P and Q in Table 6 as indicated here.