277v pole lights

[liquidtite]

Working on a site were there's existing 277v pole lights

They ran 2/0 feeders through boxes and then taped 10awg to the lights with little fusses .

today we came to wrk and circuit was tripped .

we already replaced a lot of the lighting when the diggers hit conduits with excavator

so we thought that would be the case but no one was digging over nite .

we isolated were the short was by unplicing mid section of jbox seeing if it holds and working our way down stream .

we ended up Un splicing a phase towards end of the line and the circuit held .

luckily down stream no lights were using that phase so we just left unspliced

at that point .

all lights were on and held for hours .

at end of day the circuit tripped no diggers on site .

we set breacker again and it held .

dont understand why breacker would hold for hours then just trip .

Was thinking maybe nick in wire and water mite be messing with it.
Or bad ocp.

any thoughts on this would help

thank you

 

[George Stolz]

Use a megger and a logical approach to finding the problem.

When regaling us with the story, keep it to the point, without

odd gaps that cause the reader to forget where you started and

what we were talking about.

 

[kwired]

What current is being drawn? You need to confirm you have a short circuit/ground fault vs overload.

Moisture isn't too likley to be the issue, leakage current typically will be low enough that you don't trip overcurrent, but does dry up the moisture as time goes on and leakage eventually stops, unless the moisture has a constant source.

If you have supplemental protection at each pole then your problem (if there is a fault) is likely underground or in a pole base ahead of supplemental protection if none of the supplemental protection is blowing.

A megger could be your friend in finding this problem.

 

[liquidtite]

We check current with amp probe and it wasn't drawing more or even close to the ocp so we new it was not over load

i dont understand why it holds for a while then trips

 

[iwire]

We check current with amp probe and it wasn't drawing more or even close to the ocp so we new it was not over load

i dont understand why it holds for a while then trips

I do a lot of these calls and when it holds for a while before it trips it ends up being water in the conduit and a burned up section of wire.

 

[kwired]

I do a lot of these calls and when it holds for a while before it trips it ends up being water in the conduit and a burned up section of wire.

Megger will help find that.

 

[iwire]

Megger will help find that.

For sure it could and I have one in the truck but I usally do not it for site lights.

I do fine with my rock and club. (Divide the circuit in half, energize it, see if it holds. Repeat as needed.) I know ... I know ... I am a hack.


No matter what method you use inevitably it is making and breaking all the splices in the poles that sucks up time.

For me the supply conductors are often big enough to rule out wirenuts and many times you are breaking tapped split bolt connections.

 

[kwired]

For sure it could and I have one in the truck but I usally do not it for site lights.

I do fine with my rock and club. (Divide the circuit in half, energize it, see if it holds. Repeat as needed.) I know ... I know ... I am a hack.


No matter what method you use inevitably it is making and breaking all the splices in the poles that sucks up time.

For me the supply conductors are often big enough to rule out wirenuts and many times you are breaking tapped split bolt connections.

If it took most of day running before it tripped, it just may save some time to divide and conquer with the megger instead of waiting for it to trip again.

 

[iwire]

If it took most of day running before it tripped, it just may save some time to divide and conquer with the megger instead of waiting for it to trip again.

The problem with that is most of the time all the readings will look bad. All the conductors will be wet, old, etc.

Its not like you are going to have all infinite readings except one that is 0 ohms.

But if you or the OP want to use the mega that is fine, I will stick with my way when it works.

 

[electricalist]

Ive only had this scenario once and it was like iwire said.
Long run of pole lights ending at a sign. After reset it would hold a day or so.
I think I ran a external wire tied to the hot and connected to each wire. Nomatter which wire it was connected to all 3 had voltage.
They were bare and wet.

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