ELECTROMECHANICAL WORKS ELECTROMECHANICAL SCHEMATIC DESIGN REPORT
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EARTHING RESISTANCE ANALYSIS CALCULATIONS BASED ON BS 7430 : 1991 A.SELECTION OF AN EARTHING CONDUCTOR AND CONNECTION TO AN ELECTRODE 1. AVERAGE FAULT CURRENT, KA 2. FAULT CURRENT DURATION 1 or 3 SECONDS ( 1 or 3 ) 3. EARTH. CONDUCT. MATERIAL, COPPER or ALUM. or STEEL ( C or A or S ) 4. INITIAL TEMPERATURE, DEG.C 5. FINAL TEMPERATURE, DEG.C 2 6. EARTHING CONDUCTOR CROSS SECTIONAL AREA, AREA, MM 2 7. NEXT HIGHER STAND. EARTHING CONDUCTOR CROSS SEC. AREA, MM
CLEAR
30 1 C 70 250 199.70 240
CALCULATE CALCULATE - A
or
CALCULATE CALCULATE - A
FINAL TEMPERATURE, DEG.C B.VERTICAL RODS
(150,200,250,450,500 for copper) (150,200,300,500 for aluminum)
1. RESISTIVITY OF THE SOIL, OHM .METER 2. LENGTH OF ELECTRODE, METER 3. DIAMETER OF ELECTRODE , METER 4. ARRANGMENT OF ELECTRODES, LINE or SQUARE or RECTANGLE or TRIANGLE ( L or S or R or T) 5. TOTAL NO. OF ELECTRODES IN LINE or IN SQUARE or IN RECTANGLE or IN TRIANGLE
6. DISTANCE BETWEEN ADJACENT RODS, METER 7. TOTAL EARTHING RODS RESISTANCE, OHMS
100 6 0.01905 R 36 6 3.91
CALCULATE CALCULATE - B
NO. OF ELECTRODES : (2,3,4,5,6,7,8,9,10 for L) (4, 8,12.16,20, 24, 28, 32, 36, 44, 52, 60, 68, 76 for S or R) (length / width <=2 for rectangle R) (3 for triangle T)
C. HORIZONTAL ROUND ELECTRODES 1. LENGTH OF HORIZONTAL CONDUCTOR, METER 2. DEPTH OF HORIZONTAL CONDUCTOR, M ETER 3. DIAMETER OF HORIZONTAL CONDUCTOR, METER 4. HORIZONTAL CONDUCTOR ARRANGEMENT, ( ARRANGEMENT, ( 1 or 2 or 3 or 4 ) * MEANS THAT : 1= SINGLE LENGTH ( * ) 0 TWO LENGTHS AT 90 2= 0 3= THREE LENGTHS AT 120 0 4= FOUR LENGTHS AT 90 5. SPACE BETWEEN STRAIGHT HORIZONTAL CONDUCTORS IN //, METER 6. NO. OF ONLY SINGLE HORIZONTAL CONDUCTOR IN //, one or two or three or four ( * ) 7. EARTHING RESISTANCE OF HORIZONTAL CONDUCTORS, OHMS
160 0.7 0.0199 1
48 2 0.84
CALCULATE CALCULATE - C
Minim Minimum um Maxim Maximum um 3.2 48 Select space value bet. Max.
( * ) 0.02 <= ratio of spacing to length <= 0.3 shall be considered and applied only only for conductors conductors in // D. CURRENT DENSITY 1. CURRENT DENSITY, AMPERES PER SQUARE METER 2. SURFACE AREA OF VERTICAL RODS, SQUARE METER
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CALCULATE CALCULATE - D
ELECTROMECHANICAL WORKS SCHEMATIC DESIGN REPORT
3. SURFACE AREA OF HORIZONTAL ELECTRODES, SQUARE METER 4. SURFACE AREA OF VERTICLE AND HORIZONTAL ELECTRODES, SQUARE METER 5. SHORT CIRCUIT GROUND (EARTH) GRID WITHSTAND, AMPERES E. CONCLUSIONS 1. Combination of the two values estimated under items (B) and (C) shall be less than any individual values of (B) or (C) because they are naturally conneted in parallel. So, the final total earthing resistance shall be less than the smallest value of 0.84 2. If Short Circuit Current Ground Grid withstand exceeds The fault current, the Grid will be safe otherwise it will not be safe, So the grid is
ELECTROMECHANICAL WORKS SCHEMATIC DESIGN REPORT
"THE GATE" DOHA-QATAR
3. SURFACE AREA OF HORIZONTAL ELECTRODES, SQUARE METER 4. SURFACE AREA OF VERTICLE AND HORIZONTAL ELECTRODES, SQUARE METER 5. SHORT CIRCUIT GROUND (EARTH) GRID WITHSTAND, AMPERES E. CONCLUSIONS 1. Combination of the two values estimated under items (B) and (C) shall be less than any individual values of (B) or (C) because they are naturally conneted in parallel. So, the final total earthing resistance shall be less than the smallest value of 0.84 2. If Short Circuit Current Ground Grid withstand exceeds The fault current, the Grid will be safe otherwise it will not be safe, So the grid is
ELECTROMECHANICAL WORKS SCHEMATIC DESIGN REPORT
"THE GATE" DOHA-QATAR
GROUNDING RESISTANCE ANALYSIS CALCULATIONS BASED ON IEEE Std.80 A.SELECTION OF GROUNDING CONDUCTOR AND CONNECTION TO AN ELECTRODE
CLEAR
1. FAULT CURRENT, KA rms 2. FAULT CURRENT DURATION 1 or 3 SECONDS ( 1 or 3 ) 3. GROUND MATERIALS ( 1, 2, 3, 4, 5, 6, 7, 8, 9 see definition below )
30 1 1
CALCULATE - A
Table (2)
(1=copper annealed soft drawn, 2=copper commercial harddrawn, 3=copper commercial harddrawn, 4=copper clad steel wire, 5=copper clad steel wire, 6=copper clad steel rod, 7=steel 1020, 8=stainless clad rod, 9=stainless steel 304) 2
6. GROUNDING CONDUCTOR CROSS SECTIONAL AREA, MM 2 7. NEXT HIGHER STANDARD GROUNDING CONDUCTOR CROSS SEC. AREA, MM
106.47 120
Equation (42)
B.VERTICAL GROUND RODS AND HORIZONTAL GROUND CONDUCTORS 1. RESISTIVITY OF THE SOIL, OHM.METER 2. LENGTH OF ELECTRODE, METER 3. DIAMETER OF VERTICAL ELECTRODE , METER 4. NO. OF RODS PLACED IN AREA 5. LENGTH OF GRID, METER 6. WIDTH OF GRID, METER 7. TOTAL LENGTH OF ALL CONNECTED GRID CONDUCTORS, METER 8. DEPTH OF HORIZONTAL CONDUCTOR, METER 2
9. AREA OF GRID COVERED BY CONDUCTORS, M 10. DIAMETER OF HORIZONTAL CONDUCTOR, METER 11. FACTOR K1 12. FACTOR K2 13. GROUNDING RESISTANCE OF RODS , OHMS
100 6 0.01905 36 160 60 500 0.7 9600 0.014 1.05 4.95 0.74
CALCULATE - B,C,D
Equation (55)
ELECTROMECHANICAL WORKS SCHEMATIC DESIGN REPORT
"THE GATE" DOHA-QATAR
GROUNDING RESISTANCE ANALYSIS CALCULATIONS BASED ON IEEE Std.80 A.SELECTION OF GROUNDING CONDUCTOR AND CONNECTION TO AN ELECTRODE
CLEAR
1. FAULT CURRENT, KA rms 2. FAULT CURRENT DURATION 1 or 3 SECONDS ( 1 or 3 ) 3. GROUND MATERIALS ( 1, 2, 3, 4, 5, 6, 7, 8, 9 see definition below )
30 1 1
CALCULATE - A
Table (2)
(1=copper annealed soft drawn, 2=copper commercial harddrawn, 3=copper commercial harddrawn, 4=copper clad steel wire, 5=copper clad steel wire, 6=copper clad steel rod, 7=steel 1020, 8=stainless clad rod, 9=stainless steel 304) 2
6. GROUNDING CONDUCTOR CROSS SECTIONAL AREA, MM 2 7. NEXT HIGHER STANDARD GROUNDING CONDUCTOR CROSS SEC. AREA, MM
106.47 120
Equation (42)
B.VERTICAL GROUND RODS AND HORIZONTAL GROUND CONDUCTORS 1. RESISTIVITY OF THE SOIL, OHM.METER 2. LENGTH OF ELECTRODE, METER 3. DIAMETER OF VERTICAL ELECTRODE , METER 4. NO. OF RODS PLACED IN AREA 5. LENGTH OF GRID, METER 6. WIDTH OF GRID, METER 7. TOTAL LENGTH OF ALL CONNECTED GRID CONDUCTORS, METER 8. DEPTH OF HORIZONTAL CONDUCTOR, METER 2
100 6 0.01905 36 160 60 500 0.7
CALCULATE - B,C,D
9. AREA OF GRID COVERED BY CONDUCTORS, M 10. DIAMETER OF HORIZONTAL CONDUCTOR, METER 11. FACTOR K1 12. FACTOR K2 13. GROUNDING RESISTANCE OF RODS , OHMS 14. GROUNDING RESISTANCE OF HORIZONTAL CONDUCTORS , OHMS
9600 0.014 1.05 4.95 0.74 0.61
Equation (55) Equation (54)
C. MUTUAL GROUND RESISTANCE 1. MUTUAL GROUND RESISTANCE, OHMS
0.42
Equation (56)
D. TOTAL GROUND RESISTANCE 1. TOTAL GROUND RESISTANCE, OHMS
0.54
Equation (53)
BS 7433
IEEE std.80
BS 7433
IEEE std.80
