## Calculate Cable Voltage Drop for Street Light Pole

February 8, 2016 14 Comments

**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**

**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 % |

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