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

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Calculation:

Load of Each Pole

  • 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


ScreenHunter_01 Feb. 04 17.50

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

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