Street lighting... Help appreciated!!!

[Trulyshocking]

Evening chaps :smiley2:

I have another conundrum i'd like to share!!

I have a task to install a new supply to a set of 6 streetlight columns as the old supply is 50 year old PILC and has insulation resistance faults that are beyond all hope!! The 6 columns are already installed with 4mm SWA and have an R1 + R2 of 2.3ohms. The length of run between them is approx 200M. The new supply up to the first column which i'm considering installing is about 150M which i've worked out needs to be 16mm to account for volt drop (for lighting 3%) and the 0.9 factor for being buried some of the way, but this figure only works if the total circuit load was all at the first column... which it obviously isnt! The problem is that I'm gonna be over my max Zs by the time the circuit is installed. Theres no way to increase the conductor size on the existing part of the circuit, so the best way will be to protect the circuit by way of an RCBO. The problem is that I'm not comfortable designing a circuit that has to have an RCD because the EFLI is crap!! We have a spark on site at the moment who has been working on the county streetlight division for a number of years, who says that on the council contract, anything below a Zs of 13 Ohms is acceptable, and of course no RCD's used there!! Are there different regulations covering streetlight installations that anyone knows of?? BS7671 has rules surrounding street furniture but certainly no exemptions that I can find regards Max Zs's! Any help appreciated :cheesy:

 

[IQ Electrical]

If you're using ADS then you limit your EFLI to suit disconnection times or you achieve disconnection by using an RCD.

 

[Engineer54]

That guy you have got working on site, must be the same guy that thought 4mm was a suitable size SWA to go 200m feeding those 6 lighting columns.... lol!!

Your basically stuck with the RCBOs when using ADS as IQ stated i'm afraid!!!

 

[Trulyshocking]

Thought so!!!
Worth a try tho, haven't been able to source these mythical streetlight Regs either! Thanks anyway

 

[pjay]

trulyshocking
had a quick browse and found this. Its only applicable in cambridge but list of relevent regs might help

http://www.cambridgeshire.gov.uk/NR...936CBCD8102/0/Street_Lighting_Policy04dec.pdf


cheers

paul

 

[pjay]

section 5.5 lists general legislation and industry standards

 

[Trulyshocking]

Thanks pjay..... I guess the compliance with all those publications (especially 7671) shows it has to be up to the standards we would apply to any domestic or other circuit........ cheers for digging that out

 

[ian.settle1]

trulyshocking
had a quick browse and found this. Its only applicable in cambridge but list of relevent regs might help

http://www.cambridgeshire.gov.uk/NR...936CBCD8102/0/Street_Lighting_Policy04dec.pdf


cheers

paul

I would beware as it lists the 16th to 1992 which had 2 amendments after this date as well as the 17th so most of the other standards may have changed as well

 

[telectrix]

Thanks pjay..... I guess the compliance with all those publications (especially 7671) shows it has to be up to the standards we would apply to any domestic or other circuit........ cheers for digging that out

now it's perhaps your turn to start digging out. cable, thast is. LOL.

 

[mogga]

Most L.As have their own spec regarding cable size ( 16mm in strathclyde) dependant on run and type of fittings they also have their own spec terminations Strathclyde have 3 different types of SMK units accepted along with SMK tap offs for bollards ect this spec should be read like the bible as i you dont follow it to the letter the L>A wont adopt the lighting system and client would be left carrying the can
Also check spec for depth ect and proximity of lighting cables to BT.Gas.DNO as these are normaly in spec as well some even list how many there should be max per circuit of differing types and spacing per type of roadway/pathway ect
Sorry IQ but RCDS in street lighting cause loads of bother due to condensationj build up inside cols and inside the SMKS
DONT think you can getaway with doing what Iv seen done in the past A nice newlec metal clad FCU in a col lol didnt need a screwdriver to open the box was rusted through

 

[IQ Electrical]

Most L.As have their own spec regarding cable size ( 16mm in strathclyde) dependant on run and type of fittings they also have their own spec terminations Strathclyde have 3 different types of SMK units accepted along with SMK tap offs for bollards ect this spec should be read like the bible as i you dont follow it to the letter the L>A wont adopt the lighting system and client would be left carrying the can
Also check spec for depth ect and proximity of lighting cables to BT.Gas.DNO as these are normaly in spec as well some even list how many there should be max per circuit of differing types and spacing per type of roadway/pathway ect
Sorry IQ but RCDS in street lighting cause loads of bother due to condensationj build up inside cols and inside the SMKSDONT think you can getaway with doing what Iv seen done in the past A nice newlec metal clad FCU in a col lol didnt need a screwdriver to open the box was rusted through

I agree, I was giving the op his only available options to comply with ADS, better design always being the preferred option!

 

[pjay]

trulyshocking, Dont know whether youve considered it yet but you could always run your 16mm to a power cabinet 150 meters out then from there with a smaller csa cable. Hard to say without knowing the layout but if your going to run 150meteres to first post then it could be and option.would save a few quid on cable.
Also would have thought youd struggle terminating two 16mm cables into a post. Would have to be into a knockout box then flex out to cutout.
All the ones we have on our site are fed off 6mm 4 core and that can be a pain to terminate at times. Specially if theres 3 or 4 of them.

 

[Guest123]

I have scans of the relevant highway furniture regs somewhere....I'll dig em out and post them when I find them.

There are a number of additional 'requirements' set out in these regs and they do get quite picky about it all.

Are these columns to be adopted by your local authority upon completion.

 

[Engineer54]

Most L.As have their own spec regarding cable size ( 16mm in strathclyde) dependant on run and type of fittings they also have their own spec terminations Strathclyde have 3 different types of SMK units accepted along with SMK tap offs for bollards ect this spec should be read like the bible as i you dont follow it to the letter the L>A wont adopt the lighting system and client would be left carrying the can
Also check spec for depth ect and proximity of lighting cables to BT.Gas.DNO as these are normaly in spec as well some even list how many there should be max per circuit of differing types and spacing per type of roadway/pathway ect
Sorry IQ but RCDS in street lighting cause loads of bother due to condensationj build up inside cols and inside the SMKS
DONT think you can getaway with doing what Iv seen done in the past A nice newlec metal clad FCU in a col lol didnt need a screwdriver to open the box was rusted through

That makes a hell of a lot of sense Mogga, didn't give condensation a thought. Haven't done much in the way general highway/street lighting in the UK... Have done quite a bit overseas, but then all of that, was new build, and in some areas of the world where condensation wouldn't be that much of a problem as it is in the UK.

This is where a working ''Experience'' in such installations really shows... Thanks!!!

 

[Guest123]

The code of parctice is published by the ILP, struggling to find a link to it at the mo.

If the OP can provide a bit more info on his situation I'll do my best to help re the regulations.:aureola:

 

[Trulyshocking]

Hi chaps.... sorry, been busy digging

@ Mogga :- Yes, condensation is one of the reasons I'm reluctant to use the RCD, during early spring the inside of these columns becomes a wadi!! My current plan is to go for as highly rated an RCD as I can get away with.

@ Pjay :- Unfortunately, dont think this will be of any benefit in this situation..... The installation is pretty much a straight line, with the first post being just less than half way along it!

I should probably put the situation into context more for all you helpful chaps
The streetlighting installation is on an MOD airbase and is about 40 - 50 years old. It was originally wired in 16mm ish PILC which as mentioned is in death throws!! 16 years ago, contractors were asked to add another 16 posts to the circuits totaling about 25 in all. This circuit is fed from a feeder piller (32A BS88), through a contactor (which is part of the site blackout system for aircraft, which is operated remotely) and then out on 3 core SWA (2 live conductors (both same phase) and 1 Neutral, with sheath as cpc). This links up with the PILC at some point underground and feeds the 25 odd columns (12 to the west of the origin and 13 to the east, covering about 1/3 mile in each direction (yeah I know!!). The entire circuit looks a bit like an H with the origin in the middle. I have the test sheets from 16 years ago when the extra columns were added (on a minor works cert!) which show a Zs of nearly 40 ohms!!!!! Apparently this was acceptable?!?!?! I've spent an age trying to trace this cable with a Cat & Genny (no records/plans available!!) but due to the cable being run close to data, drainage and foul water, LV and mostly HV cabling, the first 4 exploratory digs have proved fruitless (or my cat and genny work is REALLY bad!!) Fridays dig has turned up the first underground T joint (to a post). I'm going to split this and test the main each side to see whats usable and whats not. Im not expecting any of it to be, and the digging is mainly to appease the bean counters who want me to use as much of the PILC as possible to keep costs down.
The part of the circuit I'm installing the new supply to, consists of 6 columns which were added beyond the extremity of the original circuit. I think it would seem obvious to most of us that it needs to be started from scratch, but the bean counters obviously want this done on the cheap (which is why we're in this trouble to begin with!!).

Hopefully this has put it into context a bit more, but basically I'm expecting to run supplies out from the contactor to power up various parts of the circuit, with lots of SWA run along walls and the minimum of trenches All I can do is make the best of yet another MOD 'bad job'!!

Cheers for the help so far.... TS

 

[Trulyshocking]

I have scans of the relevant highway furniture regs somewhere....I'll dig em out and post them when I find them.

There are a number of additional 'requirements' set out in these regs and they do get quite picky about it all.

Are these columns to be adopted by your local authority upon completion.

Would be very grateful! No, its private network so additional council requirements shouldnt be a problem.... was looking for something to show a lesser requirement for loop readings.... the council seem to think anything below 13 ohms is fine!?!?