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Posted By Topic: Street lighting maintenance

slaw54
Jan 22 2020 20:41

Apologies for 2 questions in 1 day, leaving aside the network owner for discussion purposes, on part of a street lighting circuit there are 2 street lights on metal poles 30 meters apart, fed by a 16mm N/S cable as was often the case. They need to be replaced with 3 equally spaced low level aluminium Hunza led bollards. The 12V tranformers are DI, there is limited space within the bollards and the area is all pavers, is there a disceet way to turn each bollard into a compliant installation on the existing N/S cable ? So MEN, main switch, access, protection etc. This is a genuine project being considered not just theoretical but excavation would be prohibitive so would appreciate any thoughts.


   

DougP
Jan 23 2020 08:50

So you want to remove the poles and replace with the bollards?

If the lights and connection blocks etc are double insulated, then what's the problem?

Just connect them to the existing NS cable.
   

AlecK
Jan 23 2020 09:03

Assuming the cable is 1C N/S; the short answer is "no".
Using the existing cable; there's no way to have the three bollards as each being a separate installation.
To have then as separate installations, each would need its own mains from its own PoS [3.9.8.2 (a)]; as well as a main switch, and an MEN set-up including electrode.


It is possible to have appliances connected directly to works. That's how most street-lighting is set up; and may be the existing situation. But in that case the owner of the works definitely needs to be involved, because no-one can work on such fittings without authorisation.
The Wiring Rules only apply to installations, so don't cover the direct-to-works arrangements.

Or the existing may already be part of an installation; in which case - assuming the existing complied when installed - you could do a straight replacement-of-fittings without many complications. But adding the extra luminaire takes you out of "maintenance / repair" and into "installation / alteration"; which has to comply with today's rules.

The fact the drivers are DI does NOT negate 5.5.4.3; which requires a PEC at EVERY lighting point. With the bollards being metallic, you can't use Exception 2(c).

As part of an installation, you may be able to set the bollards up as a series of cascaded submains; ie have a MSB at or upstream of the first, and then each length of u/g cable as a PEN submain and each bollard as an "outbuilding". But there's a number of complications in that approach. Not the least of which is setting MEN system up (including electrode) at each bollard - each of which requires inspection.
   

Someone
Jan 27 2020 19:07

I think you mean 5.4.3, to forestall the confusion.

Feeding them with ELV could be an option. Assuming volt drop isn't an issue with 16mm cable, you could have a single driver at the source. Likely connect them in series and use a 60V max constant current driver of the required power output. No requirement for double insulation for SELV or PELV (so can use the screen as a conductor), and no need for an earth at the fitting as long as there's one at the driver location.


   

slaw54
Jan 31 2020 11:17

This is still provoking on going discussion, could somebody take a look at Auckland's code of practice for street lighting https://at.govt.nz/media/310324/ATCOP_Section_19_Street_Lighting.pdf
page 9 shows (I think) multiple installations on a N/S cable that is compliant with 3000.
If however the additional lights were considered to be works do you think the addition of an earth electrode and RCD would be worthwhile to improve electrical safety ?
Thanks
https://at.govt.nz/media/310324/ATCOP_Section_19_Street_Lighting.pdf
   

AlecK
Jan 31 2020 13:05

Interesting - and thanks for the info.

First thing to note is it's watermarked as a 'draft".

Second, the statement on p8 that each street light position is an installation as defined in AS/NZS 3000 may be true; but it's completely irrelevant.
ESR 4 requires the - rather different - definition in the Electricity Act to be used instead.

3rd; the Fig on p9 shown a number of things that don't work for what you're faced with.

The supply along the street, labelled as being "Vecor'; so presumably 'works', is 2C N/S.
the Fig show both "P" & "N" if this being connected in same crimp to the N-bar (ie a dead short on the supply.
The mcb shown could act as a main switch (which every installation requires), but the text forbids mcbs for subcircuit protection and requires HRC instead. So both a main switch and a fuse will be needed

They require same size MEC as the supply.

Electrode (they call it 'pin" on fig p9; but "rod" p10) non-compliant; connection must accessible for testing, NOT buried 300mm under ground. being Cad-welded does NOT change this, it just means you don't need a label warning not to disconnect MEC from electrode.

instruction p10 to "each luminaire along the street" to "alternate phases" not compatible with opening statement that each one is 'an installation'.
Fig 3 for streetlight supplied from traffic light controller makes the street lighting a final subcircuit - but in that case the config described / shown for each light cis non-compliant on a number of counts.

Basically what's shown / described will mostly NOT comply with ESRs as an installation, and especially not as a group of installations.

Which is what you can expect to get when people who know SFA start writing specifications.


   

pluto
Jan 31 2020 21:32

The Vector system of supply for the street lights will be TN-C for which AS/NZS 3000 does not provide the correct answers or instructions.

The draft Auckland Transport instructions are draft do not align with normal TN-C system of supply used by Lines companies.

I would suggest that the original OP contact both Vector and Auckland Transport to sort out the correct solution. But leave the as/nzs 3000 wiring rules at home they are of no use when using the TN-C system of supply and use the ESR 2010 for the requirements.
   

AlecK
Feb 01 2020 11:27

The problem is much wider than just AT & Vector; it's all around the country. Street light work is increasingly done under contract, and no longer simply undertaken by the local network by default. So TLAs draw up electrical specifications; without actually having any relevant expertise. Many TLAs have adopted the view that streetlights must be installations; and have further assumed - incorrectly - that the existing streetlighting is an installation. And they've also demanded CoCs, and inspections, all based on the false idea that it's work in an "installation".

It would be possible to come up with a solution for street lighting as an installation; but this draft certainly isn't it.
And even if done correctly, it would only be usable for new work; because almost all existing street lighting has never been "installation", but instead "equipment-supplied-direct-from works".

And there's little point asking a linesco engineer to design the new system; because - as Pluto suggests - their experience is all about TNC distribution rather than TN-C-S installations.

When it comes to refurbishing / upgrading / extending / altering existing street light systems; the only viable answer is to forget about "installation" rules and work with what's there. And for that, linesco engineers are the best people to do the design work; because most of us only know "installations"

I don't think adding N-E connections, or electrodes, is going to make streetlights safer than if correctly designed for connection direct to the (TNC) networks. By itself, it can't make the streetlights comply as installation(s). It's just adding cost.
   

pluto
Feb 01 2020 12:31

The best solution is the Lines Co must come up with the design and inspect at the completion of the work. The Lines Co will know the limitations of their network, so they should be able to easily do the design.

A contractor could be used to install any street light system.
Line cos in many areas use contractors to install substations for line cos and street lighting could be considered the same.

Double insulating the street light lighting is one approach as the street light fitting is 5 metres above the footpath, so well out of the way from touch. This is the approach used in downtown Sydney and they use metal poles (AL) which are not earthed. The street light fitting is insulated from the pole by a plastic bush on the fitting mounting spigot.

If it is proposed to introduce traffic light controllers into the street light control mix, this will require some innovative thinking on how to ensure isolation between the various devices, need more details. A radio link is likely to be the easiest.