Car Park/Street lamps

[Dave2010]

hey

5 metre 250W SON lights in a car park. Was asked today to change the lamps on 1 as not working. However was told its not been working for 4 yrs!!
Went to check the supply at bottom of the light and found non. Check previous light and found supply so there is nothing between the 2 lights

Quick CONT check (L-N) using voltage/continuity tester and tester lit up indicating CONT. However when double checking with my metrel tester I got open circuit indicating no CONT i suspect cable damage?

TBH i have never played with these before and the whole setup seemed wierd. Wired in 2 core SWA and i couldnt identify a "banjo/earthing nut" didnt have time to do any further test but will 2moro. Hopefully this pic will show all and you could advise if you think its normal.







cheers

 

[Lectrician]

Image shack is painfully slow....

There are two cables in your pic. Is the light that is working or the one that is not?

Two meters would give the same reading. I would think you are not using them correctly. Are you testing for continuity with all cores isolated?

The SWA is being used as the earth, and this is being picked up through the galv box. Not ideal, and in this situation serrated washers are usually used. Nothing fundamentally wrong with it as long as there is an effective earth though.

 

[Dave2010]

excellent thanks for that

yeah sorry the pics are of the working light. Its last light on circuit thats faulty.

So because its a galv box you dont need banjo or earthing nut? or is it just bad practice.

I identified the SWA feeding the faulty light, removed from switch and connected them both together. I went to faulty light and checked CONT from there. Ideally i would have done it at board but this just seemed quicked for now.

 

[electronicsuk]

I suspect the OP's initial check showed continuity through the impedance of the fitting/ballast, whereas the second test using the Metrel to perform a low impedance continuity check with a greater test current would provide more meaningful results.

I'm not sure why OP thinks that testing for continuity between L-N will be helpful in diagnosing a fault, unless the cores were disconnected at both ends?

EDIT:

I identified the SWA feeding the faulty light, removed from switch and connected them both together. I went to faulty light and checked CONT from there. Ideally i would have done it at board but this just seemed quicked for now.

OK, that wasn't there a minute ago. If you linked the two cores out then the Metrel should definitely have given a low resistance reading. Have you tried linking the L and N out to earth individually to find out if just a single core has been broken? And are you 100% sure you're looking at the right cable from the feed end?

 

[Spark123]

If you have power at one end of the cable and nothing at the other then it has probably been lobbed through!
What are IR results like on that length of cable?

 

[sparkwright]

Deleted.

 

[Dave2010]

lobbed through!

whats that mean mate? Cut through??
Unsure on IR as of yet, spend ages getting the cables back into the terminals on the switch so ran out of time and had to shoot off LOL. Will check 2moro

Have you tried linking the L and N out to earth individually to find out if just a single core has been broken? And are you 100% sure you're looking at the right cable from the feed end?

no tried yet. Is it best done at board or can i follow same concept i have and just exchange cables for Earth?
100% sure mate its the right cable

 

[AndyPRK]

why do people use imageshack !!!

 

[electronicsuk]

Have you tried linking the L and N out to earth individually to find out if just a single core has been broken? And are you 100% sure you're looking at the right cable from the feed end?

no tried yet. Is it best done at board or can i follow same concept i have and just exchange cables for Earth?

Either will work, although you could be measuring back through a fair length of cable if you work back to the board, and looking at the way the whole lot has been installed, there's no guarantee that the earth will even be sound throughout the entire circuit. Better to test from the most local point, i.e. the other end of the cable.

As already mentioned, IR between L/N and E would be a good idea as well as continuity. You could also check insulation resistance L - N, although I suspect it can't be too bad, as the circuit isn't tripping.

 

[streetlighter]

Those metal clad fuse spurs really need replacing with a proper streetlighting cutout. The proper cutouts have brass gland plates for earth continuity and plenty of space avalable for the connections. I would recommentd tofco or Charles en direct.

 

[Dave2010]

so once i confirm no cont and depending on IR would it be safe to say cable is damaged?
AFAIK its buried directly in car park concrete LOL and i would hate to tell the boss its balls'd and then only to discover after digging up its OK LOL.

On these circuits there is only the 2 lights each. There are 6 lights in total 2 per circuit so 3 circuits there is no RCD on these either. Nothing is tripping.

 

[Dave2010]

Those metal clad fuse spurs really need replacing with a proper streetlighting cutout. The proper cutouts have brass gland plates for earth continuity and plenty of space avalable for the connections. I would recommentd tofco or Charles en direct.

excellent i will bring that up. However I know how its going to go though LOL
"Boss we could really do with these!!!
"Why whats the problem?? Are the current ones not working???"
"Everything is working OK its just better and more up to standard"
"Err....no"
LOL

 

[Spark123]

lobbed through!

whats that mean mate? Cut through??

Yep, with a digger or similar. If you wanted to you could use a wander lead to check continuity between the ends of each conductor and armour - are you 100% sure of the cable routes?
Is there any sign of disturbance to the ground between the two posts?
Do you have access to a cable detector (CAT) and a signal generator?

 

[Dave2010]

lobbed through!

whats that mean mate? Cut through??

Yep, with a digger or similar. If you wanted to you could use a wander lead to check continuity between the ends of each conductor and armour - are you 100% sure of the cable routes?
Is there any sign of disturbance to the ground between the two posts?
Do you have access to a cable detector (CAT) and a signal generator?

wander lead is a good idea but is it any different to what i have already done??
no sign of disturbance.
apparently last year a "firm were checking drains And they had some sort of machine they ran along the ground and advised there was cabling all the way to the post and it should work"
***pls note this was before i started and i have know idea what on earth happened LOL***
No access to anything atm

and refering to the pics. Should some sort of banjo/earthing nut and fly lead to earth terminal be used to give a better earthing rather than relying on the galv box and armouring connection?

 

[RF Lighting]

Maybe get an electrician to have a look at it for you?