Led street lights tripping mcb

[cliffed]

Just had a quick look at a job,intermittent tripping of 10 amp mcb,retrofit led replacing discharge lighting,some time ago.
There are 7 street lights,couldn’t real do too much investigation,rain stopped play.
Did a IR test proved to be satisfactory,just wondering if any of you guys
Had any thoughts.

 

[SparkyChick]

I suspect it's in-rush current from the drivers in the LEDs. If Zs is OK, you may be able to change the MCB to a Type C which may be able to handle it.

 

[cliffed]

Yea thinking that too,not too much information on wattage,but the other lamp posts another 7 are exactly the same & pose no problems.

 

[Octopus]

Do dead tests to confirm suitability of changing the breaker .........

people don't consider this when changing to LED's

 

[SparkyChick]

The fact one breaker works fine and another doesn't, could be manufacturing tolerances, age, manufacturer... the other may even already be a Type C.

 

[cliffed]

Do dead tests to confirm suitability of changing the breaker .........

people don't consider this when changing to LED's

Agree,this problem just happening after approximately 6 months,seems a bit weird

 

[ipf]

I suspect it's in-rush current from the drivers in the LEDs. If Zs is OK, you may be able to change the MCB to a Type C which may be able to handle it.

Good chance.....but 'some time ago' may have some bearing.
Presumably it's been OK for that long.

 

[ruston]

Just had a quick look at a job,intermittent tripping of 10 amp mcb,retrofit led replacing discharge lighting,some time ago.
There are 7 street lights,couldn’t real do too much investigation,rain stopped play.
Did a IR test proved to be satisfactory,just wondering if any of you guys
Had any thoughts.

Water maybe , depending maybe if they are linked?

 

[cliffed]

Water maybe , depending maybe if they are linked?

Will check ,but IR seems ok 2.5 M ohms.

 

[Octopus]

If the MCB can be changed and the IR is good - I would do that first....

More info needed really.

 

[ruston]

Will check ,but IR seems ok 2.5 M ohms.

I have had this before when the accumulated puddle got deep enough to short it out.

 

[cliffed]

Cheers to all...thanks

 

[markc123]

Could literally be something as simple as a knackered MCB.

Any pattern to the tripping? Or just random?

Inrush, Water, MCB.

What’s the location of this? I once had a mystery street light tripping on a Caravan Park. Turned out to be Mr.Smith turning it off himself as it was disturbing his sleep been located straight outside his bedroom window.

 

[cliffed]

It’s been monitored by local council,there’s no set pattern,but once a week apparently.
Thinking in rush,but there are other lights exactly the same,these are ok.

 

[SparkyChick]

Just a couple of thoughts I've had about this...

As I understand it, in-rush is it's cycle dependent.

If by chance the lights are turned on at exactly the peak of the cycle, the in-rush current is likely to be huge due to the large potential difference, where as if the lights are turned on at the zero crossing point, the in-rush will be practically non-existent as the potential difference that drives the current will be zero.

If they are contactor controlled, could it be a result of intermittent contact bounce? If the contacts don't settle quickly you could be getting a few spikes in current consumption which may be enough to push the MCB over the edge.

 

[Marvo]

Try get more info off the customer about whether the tripping is immediate as the lights come on. It could be inrush current but usually that would be a problem from day one. I'd do all the usual dead tests and visually inspect all lights on the circuit for signs of terminations overheating/burning, also insect infestations, signs of water ingress etc before replacing the MCB with a slower curve alternative.

 

[cliffed]

Thanks everyone,off to see what I can do.

 

[DPG]

Wonder what's causing the 2.5M IR? What was that measured between?

 

[freddo]

2.5M is not a terrible reading, certainly not for a load of o/s lights. Very small amount leakage current.

 

[DPG]

2.5M is not a terrible reading, certainly not for a load of o/s lights. Very small amount leakage current.

I agree, not terrible. But also not great.

 

[cliffed]

Yea I think the IR ok.
Been back & think I’ve sorted it,Zs measures 1.37 ohms,so okay.
After testing,switching on off,the mcb tripped,tried on the other lights,which are exactly the same,this did not happen.
Swapped 10 amp for C type,that worked without tripping,monitoring over next couple of weeks.

 

[Nigel]

Posts like this besume me.

In all honesty it could be absolutely anything. There is no limit to the number of ideas that can be posted that would all be relevant.

It is impossible to fault find over the internet. You need to go back and test until you find the issue. Being intermittent it may just be a case of replacing the MCB as a start but u less you are prepared to try all the 100 possibilities floated on here it is pretty pointless asking.

 

[cliffed]

Like I’ve said,it’s an on going situation,the IR results are fine,I’ve changed the mcb,tested the system.
I’m not asking for anyone to find the fault for me,interested in what fellow electricians think.
The client been informed of all the tests,& we will see if a fault situation re occurs.

 

[Octopus]

Posts like this bemuse me.

In all honesty it could be absolutely anything. There is no limit to the number of ideas that can be posted that would all be relevant.

It is impossible to fault find over the internet. You need to go back and test until you find the issue. Being intermittent it may just be a case of replacing the MCB as a start but u less you are prepared to try all the 100 possibilities floated on here it is pretty pointless asking.

I've given you a disagree, because we all know that start up currents can be very high on LED's and as the reported IR wasn't low, swapping the MCB for a type C makes perfectly good sense

 

[cliffed]

Agree..
Hopefully it’s solved the prob.