# Load calculations for street & road lighting



## 10492

shahsaud786 said:


> I have 200kVA, 3-phase 4 wire hermetically sealed power transformer with voltage rating of 13.8kV/400/220/110V. I want to use it in road & street lighting application.
> My load characteristics are:
> 1. total lighting poles are 255, where one pole have only one luminaire (lamp).
> 2. power rating of one pole (luminaire) is 400 watts.
> 3. so total power of full load is k-watts.
> 4. HV used in the system is 13.8kV
> 5. LV output from transformer is 400/220/110 V
> I want to calculate total (3-phase) current, current through one phase. And also want to know that how voltage drop affect my length of transmission (load) cable. I mean for how much length can i install the cable to transmit the power to the load. where the average distance between the consecutive poles is 50m.
> 
> someone please solve my problem. thanks
> engineer shah saud


If you're spacing them at 150' apart, that's 7.2 miles of wire?

Ariel or underground?


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## maddhatter

sounds like homework...


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## shahsaud786

*Load calculation for load & street lighting*



Dnkldorf said:


> If you're spacing them at 150' apart, that's 7.2 miles of wire?
> 
> Ariel or underground?


the cable is underground.
distance from pole to pole is 50m or 164'
the power rating of one pole is 400 watts & total poles are 255
so the total load power is : 255 x 400 = 102 kW approx.

transformer is 200 kVA, 3-phase 4 wire, with volt rating as 400/220/110
i want to know the method how to calculate the total current fetched by load & single phase current.

plz help me if you can.
thanks bro...


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## shahsaud786

*Load characteristics for road & street lighting*



shahsaud786 said:


> I have 200kVA, 3-phase 4 wire hermetically sealed power transformer with voltage rating of 13.8kV/400/220/110V. I want to use it in road & street lighting application.
> My load characteristics are:
> 1. total lighting poles are 255, where one pole have only one luminaire (lamp).
> 2. power rating of one pole (luminaire) is 400 watts.
> 3. so total power of full load is ( 255 x 400 = 102 kW).
> 4. HV used in the system is 13.8kV
> 5. LV output from transformer is 400/220/110 V
> I want to calculate total (3-phase) current, current through one phase. And also want to know that how voltage drop affect my length of transmission (load) cable. I mean for how much length can i install the cable to transmit the power to the load. where the average distance between the consecutive poles is 50m. where the cable is underground and its size is 3x35 mm2.
> 
> someone please solve my problem. thanks
> 
> engineer shah saud


. All cable is underground
. Require how to calculate the total current i.e 3-phase current
. and to calculate the current through single phase


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## shahsaud786

I have one solution for the problem. Want to see our opinion about it:

1.	Total power of load is 255 x 400 = 102 kW or (102 x 0.85 = kVA )
2.	Transformer rating is 200 kVA or ( 200 / 0.85 = 235 kW )
3.	So total load power doesn’t exceeds the total power rating of transformer
4.	Power factor is 0.85
5.	Using the formula to calculate 3-phase current P = √3 x V x I x P.F
6.	So 102kW = 1.732 x 400V x I x 0.85 or 102kW / 589 = I or I = 173.2 A
7.	This is 3-phase current
8.	So current through single phase is I = 173.2 / 3 or I = 58 A i.e. current through branch circuit


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## wildleg

where in pakistan is this being installed


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## shahsaud786

this is't installed in pakistan. i am working in KSA.


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## wildleg

well, then just double the size you think they need. they can afford it.


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## Speedy Petey

Duplicate


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