# Street Light



## ahrambakr (Feb 1, 2009)

Please help me.

I have an RO plant. there should be 30 street poles 20 m apart around the plant. 
I want to know how to design it. 
1- Pole height 6 m
2- 20 Poles single arm with Sodium bulb @ 250 Watt , 220 Volts.
3- 10 Poles double arm with Sodium bulb @ 250 Watt , 220 Volts.

what should be the cable size? 
and should it be one line (one circuit breaker) or two (Two circuit breakers).

thanks


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## MikeFL (Apr 16, 2016)

You have not provided enough information.
Are you feeding it from the middle or from one end?
How far from the service to the first pole?
You need to draw it up and do your calculations at each point down the line.
You only have full load from the service to the first pole, and so on.


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## ahrambakr (Feb 1, 2009)

Thank you
the feeding will be from one end.
the first pole is 50 m from the control panel.


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## socket2ya (Oct 27, 2016)

That many poles with the voltage drop, I imagine you'll need more than one circuit.


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## Bird dog (Oct 27, 2015)

They may take a beating on voltage drop. Could you design it for 380v?


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## joebanana (Dec 21, 2010)

2-30A. circuits, w/#6


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## telsa (May 22, 2015)

It's not uncommon for such long runs to fed as a series circuit.

This is seen in both airport landing systems and street lighting.

The purpose is to stop variation in illumination levels.

You must look into whether this is an issue for your application.

In a series illumination circuit, the path goes out and back... looping from hot to hot across the phases.

At each point of illumination, an isolation transformer taps the passing current to energize one fixture. 

Since each transformer is identical, and sees the same amps, and voltage drop, it draws the same power level.

These transformers are mass produced to the correct specifications, and are designed to survive rough field conditions.

Being of the desert kingdom, you'll need top grade materials... no matter what you design.

BTW, in airports the voltage used often runs to 5,000 volts for the series circuit.

While this system is expensive, it does last forever, and its results are excellent.

The question you have to answer is: just how fussy is your client ?

Since KSA's nightlife is so important, I'd suspect that your client will prove to be VERY fussy.


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## joebanana (Dec 21, 2010)

telsa said:


> It's not uncommon for such long runs to fed as a series circuit.
> 
> This is seen in both airport landing systems and street lighting.
> 
> ...


I've done maintenance on that type of system. 2,300 volt, fed from a constant current xfmr. The mogul lamp sockets plug into a socket in the head, and have a shorting link, so when a lamp burns out, the link shorts to keep the string going.(and welds the socket to the receiver) Have you ever seen a 2300 volt incandescent lamp?


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