street lighting, how does it work

[ross94]

hi, I am not talking about the street lights on the main road with their own sensor, I am talking about the street lights usually in housing estates (mine for example) that all come on at the same time. how do it work. I understand there is only one lamppost which has the sensor on it and is usually right next to a feeder pillar (brown box). I take it a supply cable comes out this pillar to the first lamppost then they loop to each other, like a radial circuit?. Then another cable from the pillar goes to the lamppost with the sensor. I take it this cable will send a permanent live to the sensor at the top? then when its dark and it sends a switch live? back to the pillar box? then what?

what goes on in this pillar box or control panel, what equipment or components does it have it inside?. how does it feed the other lampposts when the sensors activates. thanks

PS: just interested I like electrics.

 

[bhm1712]

If it's anything like our site lighting at work there will be a bank of contactors inside the pillar box/control panel which when the sensor is operated puts power onto the coils of all the contactors which in turn powers all the seperate lamp circuits on site so they all strike up at the same time.

 

[oceansoul]

Round our way we've had all new street lighting installed. Each one has its own sensor, but all the lights in the street "talk" together via a small aerial on the top. It requires that a number of lights (think 4 min) "think" it is dark before they will turn on. Supposed to stop the odd one coming on by itself etc

 

[Lectrician]

When copper was cheaper than electronics, they would install one timer or sensor, contactor(s) and run cable looping past all the lamp posts, typically a 10 or 16mm straight concentric. Each post would have a street light cutout with fuse. The circuit would be fused quite high, rated to the cable, not load.

With overhead, the thinner, top wire is the switched street lighting.

As copper prices increased, and electronics decreased, it became more viable to install sensors on each lamp head, and just put a live feed into the post from the closest main, possibly looping past a couple.

I don't see a problem with lamp posts coming on one at a time, it doesn't make much difference, and I don't think that's the real reason behind lamp posts talking to each other. That's a considerable cost for no gain.

 

[stuartR1963]

thanks that makes sense. so power feeds the sensor then it sends a signal back to the pillar then activates the coils on contactor bank which then supplies the rest of the street lights. I see. just one thing though forgive my ignorance, but is a contactor just like a relay but with more capacity?. cheers

 

[Dave54]

thanks that makes sense. so power feeds the sensor then it sends a signal back to the pillar then activates the coils on contactor bank which then supplies the rest of the street lights. I see. just one thing though forgive my ignorance, but is a contactor just like a relay but with more capacity?. cheers

Exactly. A big relay with heavy contacts for switching heavy loads. Often has auxilary smaller contacts for control circuits too.
The setup described above sounds exactly like the "High bay" lighting setup I've seen in factories. One sensor working contactor(s) for the lighting so it all comes on together.

 

[Lectrician]

In my experience, if there is just one sensor, it may be on one column, a cabinet, the substation etc. A large roundabout near me has it on a roadside cabinet. As kids (OK, teenagers) we would cover it.

 

[Dave54]

I'd have a guess that the street light "talking" to each other, also means that they can be controlled remotely, so you can, for instance, switch off lights in the early hours when not needed, leaving just a few on at key points. Or switch off every other light. etc. etc.

I live in the countryside, and I don't really like the proliferation of street lighting. Every village is brightly lit these days.

 

[RF Lighting]

We've got the new street lights with the little aerials on top. They come on when it gets dark, and then Leeds city council switch them off between midnight and 5am.

 

[EFLImpudence]

and then Leeds city council switch them off between midnight and 5am.

You'd think they would do it at the same time every night.
What time do they come back on?

I'll get me coat.

 

[Lectrician]

Think he means off at 12, on at 5. Oh, hang on. I'll get my specs.

There are standard NEMA based photocells which can switch off between certain night hours, they are incredibly accurate, working by "hours since dusk", and they learn. Just as a street with standard photocells sees them all ping on within a few minutes, these will turn off around midnight, very quickly in time with each other.

This aerial thing seems OTT, and is not seen around here. Perhaps they can turn them on quickly for emergencies etc? Makes you wonder how they calculate the energy usage.

 

[Dave54]

I wonder if they have somebody there saying "You've left the lights on in the High Street again. Turn 'em off! You don't pay the bill!"
I know the boys in the power generation business love street lighting, because it helps keep the generators running when there's not as much load in the early hours.

 

[333rocky333]

This aerial thing seems OTT, and is not seen around here. Perhaps they can turn them on quickly for emergencies etc?

I was once told emergency services can make traffic lights go to green when aproaching, so maybe your right.

 

[Iggifer]

I don't know how we implement it in this country, but AIUI, there's 3 ways emergency vehicles can change the traffic lights - a strobe/infrared light, acoustically and GPS/radio. It can also be done remotely, but this seems like it's not the quickest/safest way to do it

 

[Spark123]

They could use a sangamo solar time clock, these can be configured to switch on at dusk and either off at dawn or a set time (between 10pm and 1am gmt).