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dineshpandit80
Commentator

Join Date: Mar 2009
Location: delhi india
Posts: 79
Good Answers: 2

grid and pit resistence

03/21/2009 1:17 AM

Dear ALL

does any body explain grid tesistence and pit resistence calculation of earthing.Let we have following valu of earth pit resistence

  1. p-1=0.25
  2. p-2=0.35
  3. p-3=0.5
  4. p-4=0.20

What will be valu of grid resistence. What is procedure to connect pit in series & what is procedure to connect in parrell
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harry potter
Power-User

Join Date: Nov 2008
Location: India
Posts: 333
Good Answers: 6
#1

Re: grid and pit resistence

03/21/2009 7:38 AM

Dear,

By Ohms Law,

Resistances in parallel have 1/ Rt = 1/R1 + 1/R2 + .... + 1/Rn

Grid resistance 1/Rt = 1/0.25 + 1/0.35 + 1/.5 + 1/.2 = 13.857 Mhos

Grid Resistance Rt = 1/13.857 = 0.072 Ohms.

Practical measurement errors if you consider, then actual mesured value shall be within 10% of your above calculations.

Grid resistance or any individual pit resistance can be measured by 3 electrodes method, instruments called Earth testers are available for the same.

regards

__________________
 Exploring the Science of Electricity
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