how to calculate the earthing conductor & no. of earth pits
required
Answers were Sorted based on User's Feedback
Answer / mrutyunjay mohanty
Dear Sir,
Greetings of the day !
Recently I have been through one answer shared by you and got your email id at AllInterview.com. Please kindly help me in my below concern :
Permissible current density equation i = (7.57*1000) / sqrt(resistivity * duration of earth fault)
Is This Answer Correct ? | 1 Yes | 0 No |
Answer / mrutyunjay
Dear Sudhakar Sir,
Greetings of the day !
Recently I have been through one answer shared by you and got your email id at AllInterview.com. Please kindly help me in my below concern :
Permissible current density equation i = (7.57*1000) / sqrt(resistivity * duration of earth fault) as per IS 3043
Is this equation to be taken for all types of electrodes ( Plate, Rod or Pipe & Strip ) ?
Because , as per IS 3043, same equation is appropriate for plate electrode
Is This Answer Correct ? | 1 Yes | 0 No |
Answer / sudhakar.g
The earth resistance of single rod or pipe electrode is calculated as per IS 3040:
R=100xρ/2×3.14xL (loge(4xL/d))
Where:
ρ = Resistivity of soil (Ω meter),
L = Length of electrode (cm),
D = Diameter of electrode (cm)
Example:
Calculate number of CI earthing pipe of 100mm diameter, 3 meter length. System has fault current 50KA for 1 sec and soil resistivity is 72.44 Ω-Meters.
Current Density At The Surface of Earth Electrode (As per IS 3043):
• Max. allowable current density I = 7.57×1000/(√ρxt) A/m2
• Max. allowable current density = 7.57×1000/(√72.44X1) = 889.419 A/m2
• Surface area of one 100mm dia. 3 meter Pipe = 2 x 3.14 x r x L = 2 x 3.14 x 0.05 x3 = 0.942 m2
• Max. current dissipated by one Earthing Pipe = Current Density x Surface area of electrode
• Max. current dissipated by one earthing pipe = 889.419x 0.942 = 837.83 A say 838 Amps
• Number of earthing pipe required = Fault Current / Max.current dissipated by one earthing pipe.
• Number of earthing pipe required = 50000/838 = 59.66 Say 60 No’s.
• Total number of earthing pipe required = 60 No’s.
• Resistance of earthing pipe (isolated) R = 100xρ/2×3.14xLx(loge (4XL/d))
• Resistance of earthing pipe (isolated) R = 100×72.44 /2×3.14x300x(loge (4X300/10)) = 7.99 Ω/Pipe
• Overall resistance of 60 no of earthing pipe = 7.99/60 = 0.133 Ω.
If you have any doubt regarding this ...pls mail me sudhakar28485@gmail.com
Is This Answer Correct ? | 4 Yes | 5 No |
how generater works
why generator and t/f ratings given in kva & motor rating is in KW?
why the transformers are rated in kv not kw?
We have isolation transformer 25kvA & ONLINE UPS 15KvA (3PHASE I/P,3PHASE O/P)where isolation should have connect,before UPS or after please brief.
WHAT IS NORMAL VECTOR GROUP USED FOR DESIGNING OF TRANSFORMERS??
In ac circuit R,L,C are connected in series what is the output the circuit? explain
What is bandpass of a transformer?
What is the difference between MCB and Earth MCB? What is the working principal of MCB?
how power trnafor from 1 point to another point in bus bar ya transmission line( voltage trnasfer from 1 point to another poin)
tell me the operation of ELCB. How it detects a fault?
what is the internal working of star delta starter
WHAT HAPPEN WHEN A DROP OF WATER MIXED UP WITH TRANSFORMER OIL ?