Calculate Size of Motor-Pump
April 14, 2013 18 Comments
Calculate Motor-Pump size:
- Calculate Pump Hydraulic Power
- Calculate Motor-Pump Shaft Power
- Calculate Pump Size.
- Calculate Motor Size.
Calculate Numbers of Plate/Pipe/Strip Earthings (Part-3)
April 1, 2013 42 Comments
Calculate Min. Cross Section area of Earthing Conductor:
- Cross Section Area of Earthing Conductor As per IS 3043
-
Cross Section Area of Earthing Conductor (A) =(If x√t) / K
- Where t= Fault current Time (Second).
- K= Material Constant.
- Example:
- Calculate Cross Section Area of GI Earthing Conductor for System has 50KA Fault Current for 1 second. Corrosion will be 1.0 % Per Year and No of Year for Replacement is 20 Years.
- Cross Section Area of Earthing Conductor (A) =(If x√t) / K
- Here If=50000 Amp
- T= 1Second
- K=80 (Material Constant, For GI=80, copper K=205, Aluminium K=126).
- Cross Section Area of Earthing Conductor (A) =(50000×1)/80
- Cross Section Area of GI Earthing Conductor (A)=625 Sq.mm
- Allowance for Corrosion = 1.0 % Per Year & Number of Year before replacement say = 20 Years
- Total allowance = 20 x 1.0% = 20%
- Safety factor = 1.5
- Required Earthing Conductor size = Cross sectional area x Total allowance x Safety factor
- Required Earthing Conductor size = 1125 Sq.mm say 1200 Sq.mm
- Hence, Considered 1Nox12x100 mm GI Strip or 2Nox6 x 100 mm GI Strips
Thumb Rule for Calculate Number of Earthing Rod:
- The approximate earth resistance of the Rod/Pipe electrodes can be calculated by
-
Earth Resistance of the Rod/Pipe electrodes R= K x ρ/L
- Where ρ = Resistivity of earth in Ohm-Meter
- L= Length of the electrode in Meter.
- d= Diameter of the electrode in Meter.
- K=0.75 if 25< L/d < 100.
- K=1 if 100 < L/d < 600
- K=1.2 o/L if 600 < L/d < 300
-
Number of Electrode if find out by Equation of R(d) =(1.5/N) x R
- Where R(d) = Desired earth resistance
- R= Resistance of single electrode
- N= No. of electrodes installed in parallel at a distance of 3 to 4 Meter interval.
- Example:
- Calculate Earthing Pipe Resistance and Number of Electrode for getting Earthing Resistance of 1 Ω ,Soil Resistivity of ρ=40, Length=2.5 Meter, Diameter of Pipe= 38 mm.
- Here L/d = 2.5/0.038=65.78 so K=0.75
- The Earth Resistance of the Pipe electrodes R= K x ρ/L =0.75×65.78=12 Ω
- One electrode the earth resistance is 12 Ω.
- To get Earth resistance of 1 Ω the total Number of electrodes required =(1.5×12)/1 =18 No
Calculating Resistance & Number of Earthing Rod:
- Reference: As per EHV Transmission Line Reference Book page: 290 and Electrical Transmission & Distribution Reference Book Westinghouse Electric Corporation, Section-I Page: 570-590.
-
Earthing Resistance of Single Rods: R = ρx[ln (2L/a)-1]/(2×3.14xL)
-
Earthing Resistance of Parallel Rods: R = ρx[ln (2L/A]/ (2×3.14xL)
- Where L= length of rod in ground Meter,
- a= radius of rod Meter
- ρ = ground resistivity, ohm- Meter
- A= √(axS)
- S= Rod separation Meter
Factor affects on Ground resistance:
- The NEC code requires a minimum ground electrode length of 2.5 meters (8.0 feet) to be in contact with the soil. But, there are some factor that affect the ground resistance of a ground system:
- Length / Depth of the ground electrode: double the length, reduce ground resistance by up to 40%.
- Diameter of the ground electrode: double the diameter, lower ground resistance by only 10%.
- Number of ground electrodes: for increased effectiveness, space additional electrodes at least equal to the depth of the ground electrodes.
- Ground system design: single ground rod to ground plate.
The GI Earthing Conductor sizes for various Equipments:
| No | Equipments | Earth Strip Size |
|
1 |
HT switchgear, structures, cable trays & fence, rails, gate and steel column |
55 X 6 mm (GI) |
|
2 |
Lighting Arrestor |
25 X 3 mm (Copper) |
|
3 |
PLC Panel |
25 X 3 mm (Copper) |
|
4 |
DG & Transformer Neutral |
50X6 mm (Copper) |
|
5 |
Transformer Body |
50X6 mm (GI) |
|
6 |
Control & Relay Panel |
25 X 6 mm (GI) |
|
7 |
Lighting Panel & Local Panel |
25 X 6 mm (GI) |
|
8 |
Distribution Board |
25 X 6 mm (GI) |
|
9 |
Motor up to 5.5 kw |
4 mm2 (GI) |
|
10 |
Motor 5.5 kw to 55 kw |
25 X 6 mm (GI) |
|
11 |
Motor 22 kw to 55 kw |
40 X 6 mm (GI) |
|
12 |
Motor Above 55 kw |
55 X 6 mm (GI) |
Selection of Earthing System:
|
Installations/ Isc Capacity |
IR Value Required |
Soil Type/ Resistivity |
Earth System |
| House hold earthing/3kA | 8 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Single Electrode | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| Commercial premises,Office / 5kA | 2 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| Transformers, substationearthing, LT line equipment/ 15kA | less than 1 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| LA, High current Equipment./ 50kA | less than 1 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| PRS, UTS, RTUs, Data processing centre etc./5KA | less than 0.5 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes |
Size of Earthing Conductor:
- Ref IS 3043 &Handbook on BS 7671: The Lee Wiring Regulations by Trevor E. Marks.
|
Size of Earthing Conductor |
||
| Area of Phase Conductor S (mm2) | Area of Earthing conductor (mm2) When It is Same Material as Phase Conductor | Area of Earthing conductor (mm2) When It is Not Same Material as Phase Conductor |
| S < 16 mm2 | S | SX(k1/k2) |
| 16 mm2<S< 35 mm2 | 16 mm2 | 16X(k1/k2) |
| S > 35 mm2 | S/2 | SX(k1/2k2) |
| K1 is value of Phase conductor,k2 is value of earthing conductor | ||
| Value of K for GI=80, Alu=126,Cu=205 for 1 Sec | ||
Standard Earthing Strip/Plate/Pipe/wire Weight:
GI Earthing Strip:
| Size (mm2) | Weight |
| 20 x 3 | 500 gm Per meter |
| 25 x 3 | 600 gm Per meter |
| 25 x 6 | 1/200 Kg Per meter |
| 32 x 6 | 1/600 Kg Per meter |
| 40 x 6 | 2 Kg Per meter |
| 50 x 6 | 2/400 Kg Per meter |
| 65 x 10 | 5/200 Kg Per meter |
| 75 x 12 | 7/200 Kg Per meter |
GI Earthing Plate:
| Plate | Weight |
| 600 x 600 x 3 mm | 10 Kg App. |
| 600 x 600 x 4 mm | 12 Kg App. |
| 600 x 600 x 5 mm | 15 Kg App. |
| 600 x 600 x 6 mm | 18 Kg App. |
| 600 x 600 x 12 mm | 36 Kg App. |
| 1200 x 1200 x 6 mm | 70 Kg App. |
| 1200 x 1200 x 12 mm | 140 Kg App. |
GI Earthing Pipe:
| Pipe | Weight |
| 3 meter Long BISE | 5 Kg App. |
| 3 meter r Long BISE | 9 Kg App. |
| 4.5 meter (15′ Long BISE) | 5 Kg App. |
| 4.5 meter (15′ Long BISE) | 9 Kg App. |
| 4.5 meter (15′ Long BISE) | 14 Kg App |
GI Earthing Wire:
| Plate | Weight |
| 6 Swg | 5 meter in 1 Kg |
| 8 Swg | 9 meter in 1 Kg |
Calculate Numbers of Plate/Pipe/Strip Earthings (Part-3)
April 1, 2013 38 Comments
Calculate Min. Cross Section area of Earthing Conductor:
- Cross Section Area of Earthing Conductor As per IS 3043
-
Cross Section Area of Earthing Conductor (A) =(If x√t) / K
- Where t= Fault current Time (Second).
- K= Material Constant.
- Example:
- Calculate Cross Section Area of GI Earthing Conductor for System has 50KA Fault Current for 1 second. Corrosion will be 1.0 % Per Year and No of Year for Replacement is 20 Years.
- Cross Section Area of Earthing Conductor (A) =(If x√t) / K
- Here If=50000 Amp
- T= 1Second
- K=80 (Material Constant, For GI=80, copper K=205, Aluminium K=126).
- Cross Section Area of Earthing Conductor (A) =(50000×1)/80
- Cross Section Area of GI Earthing Conductor (A)=625 Sq.mm
- Allowance for Corrosion = 1.0 % Per Year & Number of Year before replacement say = 20 Years
- Total allowance = 20 x 1.0% = 20%
- Safety factor = 1.5
- Required Earthing Conductor size = Cross sectional area x Total allowance x Safety factor
- Required Earthing Conductor size = 1125 Sq.mm say 1200 Sq.mm
- Hence, Considered 1Nox12x100 mm GI Strip or 2Nox6 x 100 mm GI Strips
Thumb Rule for Calculate Number of Earthing Rod:
- The approximate earth resistance of the Rod/Pipe electrodes can be calculated by
-
Earth Resistance of the Rod/Pipe electrodes R= K x ρ/L
- Where ρ = Resistivity of earth in Ohm-Meter
- L= Length of the electrode in Meter.
- d= Diameter of the electrode in Meter.
- K=0.75 if 25< L/d < 100.
- K=1 if 100 < L/d < 600
- K=1.2 o/L if 600 < L/d < 300
-
Number of Electrode if find out by Equation of R(d) =(1.5/N) x R
- Where R(d) = Desired earth resistance
- R= Resistance of single electrode
- N= No. of electrodes installed in parallel at a distance of 3 to 4 Meter interval.
- Example:
- Calculate Earthing Pipe Resistance and Number of Electrode for getting Earthing Resistance of 1 Ω ,Soil Resistivity of ρ=40, Length=2.5 Meter, Diameter of Pipe= 38 mm.
- Here L/d = 2.5/0.038=65.78 so K=0.75
- The Earth Resistance of the Pipe electrodes R= K x ρ/L =0.75×65.78=12 Ω
- One electrode the earth resistance is 12 Ω.
- To get Earth resistance of 1 Ω the total Number of electrodes required =(1.5×12)/1 =18 No
Calculating Resistance & Number of Earthing Rod:
- Reference: As per EHV Transmission Line Reference Book page: 290 and Electrical Transmission & Distribution Reference Book Westinghouse Electric Corporation, Section-I Page: 570-590.
-
Earthing Resistance of Single Rods: R = ρx[ln (2L/a)-1]/(2×3.14xL)
-
Earthing Resistance of Parallel Rods: R = ρx[ln (2L/A]/ (2×3.14xL)
- Where L= length of rod in ground Meter,
- a= radius of rod Meter
- ρ = ground resistivity, ohm- Meter
- A= √(axS)
- S= Rod separation Meter
Factor affects on Ground resistance:
- The NEC code requires a minimum ground electrode length of 2.5 meters (8.0 feet) to be in contact with the soil. But, there are some factor that affect the ground resistance of a ground system:
- Length / Depth of the ground electrode: double the length, reduce ground resistance by up to 40%.
- Diameter of the ground electrode: double the diameter, lower ground resistance by only 10%.
- Number of ground electrodes: for increased effectiveness, space additional electrodes at least equal to the depth of the ground electrodes.
- Ground system design: single ground rod to ground plate.
The GI Earthing Conductor sizes for various Equipments:
| No | Equipments | Earth Strip Size |
|
1 |
HT switchgear, structures, cable trays & fence, rails, gate and steel column |
55 X 6 mm (GI) |
|
2 |
Lighting Arrestor |
25 X 3 mm (Copper) |
|
3 |
PLC Panel |
25 X 3 mm (Copper) |
|
4 |
DG & Transformer Neutral |
50X6 mm (Copper) |
|
5 |
Transformer Body |
50X6 mm (GI) |
|
6 |
Control & Relay Panel |
25 X 6 mm (GI) |
|
7 |
Lighting Panel & Local Panel |
25 X 6 mm (GI) |
|
8 |
Distribution Board |
25 X 6 mm (GI) |
|
9 |
Motor up to 5.5 kw |
4 mm2 (GI) |
|
10 |
Motor 5.5 kw to 55 kw |
25 X 6 mm (GI) |
|
11 |
Motor 22 kw to 55 kw |
40 X 6 mm (GI) |
|
12 |
Motor Above 55 kw |
55 X 6 mm (GI) |
Selection of Earthing System:
|
Installations/ Isc Capacity |
IR Value Required |
Soil Type/ Resistivity |
Earth System |
| House hold earthing/3kA | 8 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Single Electrode | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| Commercial premises,Office / 5kA | 2 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| Transformers, substationearthing, LT line equipment/ 15kA | less than 1 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| LA, High current Equipment./ 50kA | less than 1 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes | ||
| PRS, UTS, RTUs, Data processing centre etc./5KA | less than 0.5 ohm | Normal Soil/ up to 50 ohm-meter | Single Electrode |
| Sandy Soil/ between 50 to 2000 ohm- meter | Multiple Electrodes | ||
| Rocky Soil/ More than 2000 ohm- meter | Multiple Electrodes |
Size of Earthing Conductor:
- Ref IS 3043 &Handbook on BS 7671: The Lee Wiring Regulations by Trevor E. Marks.
|
Size of Earthing Conductor |
||
| Area of Phase Conductor S (mm2) | Area of Earthing conductor (mm2) When It is Same Material as Phase Conductor | Area of Earthing conductor (mm2) When It is Not Same Material as Phase Conductor |
| S < 16 mm2 | S | SX(k1/k2) |
| 16 mm2<S< 35 mm2 | 16 mm2 | 16X(k1/k2) |
| S > 35 mm2 | S/2 | SX(k1/2k2) |
| K1 is value of Phase conductor,k2 is value of earthing conductor | ||
| Value of K for GI=80, Alu=126,Cu=205 for 1 Sec | ||
Standard Earthing Strip/Plate/Pipe/wire Weight:
GI Earthing Strip:
| Size (mm2) | Weight |
| 20 x 3 | 500 gm Per meter |
| 25 x 3 | 600 gm Per meter |
| 25 x 6 | 1/200 Kg Per meter |
| 32 x 6 | 1/600 Kg Per meter |
| 40 x 6 | 2 Kg Per meter |
| 50 x 6 | 2/400 Kg Per meter |
| 65 x 10 | 5/200 Kg Per meter |
| 75 x 12 | 7/200 Kg Per meter |
GI Earthing Plate:
| Plate | Weight |
| 600 x 600 x 3 mm | 10 Kg App. |
| 600 x 600 x 4 mm | 12 Kg App. |
| 600 x 600 x 5 mm | 15 Kg App. |
| 600 x 600 x 6 mm | 18 Kg App. |
| 600 x 600 x 12 mm | 36 Kg App. |
| 1200 x 1200 x 6 mm | 70 Kg App. |
| 1200 x 1200 x 12 mm | 140 Kg App. |
GI Earthing Pipe:
| Pipe | Weight |
| 3 meter Long BISE | 5 Kg App. |
| 3 meter r Long BISE | 9 Kg App. |
| 4.5 meter (15′ Long BISE) | 5 Kg App. |
| 4.5 meter (15′ Long BISE) | 9 Kg App. |
| 4.5 meter (15′ Long BISE) | 14 Kg App |
GI Earthing Wire:
| Plate | Weight |
| 6 Swg | 5 meter in 1 Kg |
| 8 Swg | 9 meter in 1 Kg |
JIGNESH PARMAR
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