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#139762 - 12/27/03 12:54 AM What to do?.
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
I would like to think that I'm pretty good at repairing Undergound cable faults.
But, a local pilot rang me the other day and when I got off the phone I just wanted to leave town.
Here's why:
The guy installs his own system of runway lights on his own private runway, way out in the middle of nowhere.
The system consists of 2 runs of 6mm2 1C Neutral Screened, each 600m long, buried direct with no further protection or marker strip and there are junction boxes buried in the ground below the lights (400 of them!).
But what the problem is, is that instead of bedding the cable in sand like you are supposed to, he decided to cover the cables up with boulders and other rocks and soil over the top of that.
Now (3 months after he buried the cables), that he has got it all hooked up, he says that the MCB on the plug (10A standard)that he pluggged it into won't hold in!.
What I am meaning to say is this, how on EARTH am I going to find a cable fault like this?
Now, it's all very well to go pointing fingers at this time, but that won't get this problem solved.
I've got 1300m of cable in which to find a dead short.
I think that the guy might be getting the excavator back out there yet!.
Thank God I've never had a ride in his plane.
What would you do in a case like this?
Should I start packing my knapsack?


[This message has been edited by Trumpy (edited 12-27-2003).]
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#139763 - 12/27/03 09:02 AM Re: What to do?.
djk Offline
Member
Registered: 12/26/02
Posts: 1237
Loc: Ireland
Mmmmm I really don't think you can it sounds very much like it's going to be full of faults as time goes on.

From what I know of underground cabling near roadways, and I can only presume runways are the same, it should be layed in pretty serious ducting as the ground around it can be subjected to quite a lot of movement and compression.

Commercial or military airport cabling can take things to other extremes too as they don't like any unsheilded long runs of cable that could potentially produce RF so the whole thing would be sheilded and certified for explosions etc...
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#139764 - 12/27/03 09:26 AM Re: What to do?.
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
If it's a dead-short on the cable rather than earth leakage due to damage, how about measuring the resistance with a low-range meter and calculating the approximate distance from source?
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#139765 - 12/27/03 07:33 PM Re: What to do?.
David UK Offline
Member
Registered: 10/03/02
Posts: 134
Loc: Inverness, Scotland
What about a 'Cat & Genny' cable fault locator? That's what the utilities use in these parts for locating faulty underground cables.
I know they can be hired over here, but with your PoCo contacts you may be able to borrow one for a few hours. Good luck.
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#139766 - 12/28/03 08:42 PM Re: What to do?.
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
Quote:
Mmmmm I really don't think you can it sounds very much like it's going to be full of faults as time goes on.

Djk,
You're absolutely right mate!.
I've rung the guy back and asked that the whole run be dug up and re-laid properly.
Once he stopped abusing and swearing at me, he realised that this was the only way to go.
I also asked that his junctions be made accessible.
I offered to oversee the whole thing next weekend, just to make sure that it's done properly.
The in-rush current of this circuit will be something to see, with 400 36W Compact Fluorescent lamps on it!.
Thanks for your ideas, guys, I new I could count on you fellas to come up with a different idea to what I had.
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