Cable Sizing Calculation

1. Project: Water Treatment Plant at Tilda, Chhattisgarh
Owner: Municipal Corporation of Tilda
Contractor: M/s. Chandra Nirman Private Limited
Site: Intake Well of Tilda WTP
Title: Cable sizing design calculation
Basic Design Parameters
Motor Name Vertical Pump
Motor Rating 75 KW
Rated Voltage 415 V
Power Factor 0.8
Frequency 50 Hz
Length of Cable 400 M
Cable Type XLPE
Laying In Tray
Ambient Temperature 50 Deg.C
No. of Rack 1
No. of Cable/Rack 9 Max.
Load Current Calculation
Load Current 130.43 A
De-rating Calculations:
Temperature Derating 0.9
Rack Derating Factor 0.73
Total Derating 0.66
Load Current after Derating 198.52
As per cable manufacturer data following cable is selected Provisionally.
Voltage Drop Calculations
Option -1
Cable Size 185 Sq.mm
Cable Ampacity 337 A
Derated Capacity 221.41 A
Short Circuit Rating 17.50 kA
Resistance of Cable 0.21 Ohm/Km
Reactance of Cable 0.0718 mho/Km
No. of Run 1
Voltage Drop 4.596023 %
Option -2
Cable Size 240 Sq.mm
Cable Ampacity 399 A
Derated Capacity 262.14 A
Short Circuit Rating 22.60 kA
Resistance of Cable 0.16 Ohm/Km
Reactance of Cable 0.071 mho/Km
No. of Run 1
Voltage Drop 3.714618 %
Conclusion:
1. Both the cable size viz., 185Sq.mm & 240 Sq.mm satisfies all the conditions as mentioned:
a. Cable derating ampere
b. Voltage drop
c. Short circuit at that point
Hence in view of present site condition / hassle free operation cable size of 240 Sq.mm is proposed.