Calculate Cable Voltage Drop for Street Light Pole

Example: Calculate Voltage drop of Cable for Street Light Pole. System Voltage is 230V (P-N), Power Factor=0.75. Allowable Voltage Drop = 4% .The Detail of Pole & cable are

Pole Detail:

• Section feeder Pillar is 50 meter away from Pole-1
• Distance between each Pole is 50 Meter Distance
• Luminar of Each Pole Fitting = 2 No’s
• Luminar Watt =250 Watt

Cable Detail:

• Size of Cable= 4CX10 Sq.mm.
• First Pole is connected in R Phase Next Pole is connected in Y Phase Than Next Pole is connected in B Phase. Next Pole is connected again R Phase.
• Resistance of Cable=3.7 Ω/Km
• Reactant of Cable=0.1 Ω/Km

Calculation:

• Load of Each Pole = (Watt of Each Luminar X No of Luminar ) / Volt X P.F
• Load of Each Pole = (250X2) /(230X0.75)
• Load of Each Pole = 2.9 Amp

For Pole Pole-1:

• Pole Connected on “R” Phase
• Total Distance of Pole for “R” Phase =50 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X50 / (230x1x1000)
• % Voltage drop of Cable= 0.18% ———————————(1)

For Pole Pole-2:

• Pole Connected on “Y” Phase
• Total Distance of Pole for “Y” Phase =50+50=100 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X100 / (230x1x1000)
• % Voltage drop of Cable= 0.36% ———————————(2)

For Pole Pole-3:

• Pole Connected on “B” Phase
• Total Distance of Pole for “B” Phase =50+50+50=150 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X150 / (230x1x1000)
• % Voltage drop of Cable= 0.54% ———————————(3)

For Pole Pole-4:

• Pole Connected on “R” Phase
• Total Distance of Pole for “R” Phase =150+50=200 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X200 / (230x1x1000)
• % Voltage drop of Cable= 0.72% ———————————(4)

For Pole Pole-5:

• Pole Connected on “Y” Phase
• Total Distance of Pole for “Y” Phase =200+50=250 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X250 / (230x1x1000)
• % Voltage drop of Cable= 0.9% ———————————(5)

For Pole Pole-6:

• Pole Connected on “B” Phase
• Total Distance of Pole for “B” Phase =250+50=300 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X300 / (230x1x1000)
• % Voltage drop of Cable= 1.07% ———————————(6)

For Pole Pole-7:

• Pole Connected on “R” Phase
• Total Distance of Pole for “R” Phase =300+50=350 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X350 / (230x1x1000)
• % Voltage drop of Cable= 1.25% ———————————(7)

For Pole Pole-8:

• Pole Connected on “Y” Phase
• Total Distance of Pole for “Y” Phase =350+50=400 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X400 / (230x1x1000)
• % Voltage drop of Cable= 1.43% ———————————(8)

For Pole Pole-9:

• Pole Connected on “B” Phase
• Total Distance of Pole for “B” Phase =400+50=450 Meter ,
• % Voltage drop of Cable= (Current X (Rcosᴓ + JSinnᴓ) X Distance ) / (Volt X No of Cable X 1000)
• % Voltage drop of Cable= (2.9x(3.7×0.75+0.1×0.66)X450 / (230x1x1000)
• % Voltage drop of Cable= 1.61% ———————————(9)

Total Voltage Drop:

• Voltage Drop in “R” Phase = 0.18+0.72+1.25 =2.15 %
• Voltage Drop in “Y” Phase =0.36+0.90+1.43 =2.69 %
• Voltage Drop in “B” Phase =0.54+1.07+1.61 =3.22 %
• % Voltage drop in each Phase is Max 3.22% Which is less than 4%

Results:

 Phase No of Pole Load (Amp) Voltage Drop R 3 9 2.15 % Y 3 9 2.69 % B 3 9 3.22 % Total 9 9 2.55 %

Cable Voltage Drop for Different Size of Cables

• Calculate Voltage of Cable having Different Size
• Calculate Starting Current
• Calculate Running Current
• Calculate Starting Voltage Drop
• Calculate Running Voltage Drop