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Insulation breakdown on service-drop splice (UK) #162602 04/22/07 08:48 AM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline OP
Member
We had a few minutes of excitement here last night when there was suddenly a fairly impressive fireworks display and a lot of smoke from the top of a nearby pole.

The insulation had broken down on the splice to a concentric-neutral service drop, resulting in direct phase-to-neutral arcing at the fault.

I scrounged the damaged section from the EDF lineman so that I could take some pictures. This is as it came down from the pole:

[Linked Image]

[Linked Image]

Here's where I've cut away the outer covering as much as possible to see what actually started the fault, but there's so little of the crimped joins and insulation left that it's hard to tell:

[Linked Image]

And finally, here's the pole this came from, seen here with the EDF guy crimping up the new splices. smile

[Linked Image]


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Re: Insulation breakdown on service-drop splice (UK) [Re: pauluk] #162605 04/22/07 09:58 AM
Joined: Oct 2006
Posts: 31
M
Mountain Electrician Offline
Junior Member
Is he supposed to be wearing a hardhat?

Re: Insulation breakdown on service-drop splice (UK) [Re: Mountain Electrician] #162612 04/22/07 11:15 AM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
And what purpose would a hard hat serve? He's already shaved hi head, so bird nesting is no longer a concern. laugh

Re: Insulation breakdown on service-drop splice (UK) [Re: renosteinke] #162615 04/22/07 12:11 PM
Joined: Oct 2006
Posts: 31
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Mountain Electrician Offline
Junior Member
A hard hat may save him in case the sky fell.

Re: Insulation breakdown on service-drop splice (U [Re: Mountain Electrician] #162657 04/23/07 02:22 AM
Joined: Jul 2002
Posts: 8,379
Trumpy Offline
Member
Paul,
Is this the service line you mentioned on the phone last time I was talking with you?
Surely looks like a sub-standard crimp or sealing job, as in moisture has got into the joint.
BTW, at which end of the service is the fuse?,
I expected to see one on the pole where the line-man is.
Bear in mind Mountain Electrician that these wires are insulated for Full Working Voltage, a hard hat would be a good idea, but not that necessary.
Nice to see he has the gloves and outers on though.

Note the lack of hair/grey hair with this guy, get with it if you want to be a Liney, it will take years off of your life!. laugh

Re: Insulation breakdown on service-drop splice (U [Re: Trumpy] #162714 04/24/07 10:11 AM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline OP
Member
I'm not sure what the current HSE (Health & Safety Executive -- a.k.a. the "'Elf & Safety Gestapo") rules would be regarding hats in this situation.

Originally Posted by Trumpy
Is this the service line you mentioned on the phone last time I was talking with you?


Mike,
I can't remember which lines that was we were talking about. blush It wouldn't have been to do with this though, as the fault only happened this last Saturday afternoon.

Quote
BTW, at which end of the service is the fuse?,
I expected to see one on the pole where the line-man is.


No, the LV side (240/415V wye) here has fuses at the xfmr secondary, then nothing else until the individual service fuse at each meter, which will be either inside the house on in the outside meter cabinet (i.e. at the load end of the service drop).

This is the xfmr at the sub-station about 100 yards away which actually feeds these lines:

[Linked Image]


Re: Insulation breakdown on service-drop splice (U [Re: pauluk] #162754 04/25/07 07:16 AM
Joined: Apr 2005
Posts: 48
U
uksparx Offline
Member
Mike - those lines may not necessarily be insulated, I can't quite tell from the pic. What you find here are a lot of the lines from pole to pole i.e. distribution lines are not insulated. The wires from the poles to the premises i.e. drop wires are insulated, but again usually only the live, not the neutral. Where they then meet the property they are changed to both insulated. My own house being a good example - txfmr to pole by house, both lines BARE, pole by house to house, live INSULATED, neutral BARE, then two insulated cables to meter. I'll try and take some pics to let you see. However, all the above has changed somewhat with the advent of ABC (aerial bundled conductor) cable and concentric drop wire.
Dave

Re: Insulation breakdown on service-drop splice (U [Re: uksparx] #162763 04/25/07 10:22 AM
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Posts: 7,520
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pauluk Offline OP
Member
Yep, there are many bare overhead lines on the pole-to-pole sections.

Here's a closer look at the pole, as it stands today (burn marks from Saturday's little incident quite evident!):

[Linked Image]

Click here for larger image


Quote
The wires from the poles to the premises i.e. drop wires are insulated, but again usually only the live, not the neutral


That's what I have. The two singles going off to the lower left of the picture above are actually the service drop to my house, which crosses right over my neighbor's front garden. The upper cable is the bare neutral; the lower is a fully insulated phase.

The other drops from this pole have all been replaced with concentrics, two overhead going off to the right, one which goes down the pole and then underground to my neighbor's house (installed about 6 years ago when we rewired and had the meter relocated outside).

Re: Insulation breakdown on service-drop splice (U [Re: pauluk] #162847 04/26/07 06:15 AM
Joined: Dec 2005
Posts: 860
R
RODALCO Offline
Member
Interesting that he doesn't have a hart hat on. Obviously he didn't trust the pole, and he is priveledged to use the bucket.

Here in Auckland we fix those jobs from one or two ladders.

I wouldn't always rely on the full working insulation on OH lines.

Weather may brittle the outer insulation so bare spots may be exposed.

It looks that the top and bottom wires are not pvc covered.


The product of rotation, excitation and flux produces electricty.
Re: Insulation breakdown on service-drop splice (U [Re: RODALCO] #162856 04/26/07 09:39 AM
Joined: Dec 2001
Posts: 2,492
T
Texas_Ranger Offline
Member
What kind of supply is this? I can only make out 3 feeder lines. Is that 2 phases and neutral from a 240/415 system?

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