OT: How does power supply company locate a fault?

[Tim Streater]

And tell you how far down the cable from the measurement point the break is, or short, or anomaly.

[Brian Gaff]

Yes hence my comment about a crater. They went through an underground cable about 6 years back at the local industrial estate. the bang was extremely loud and the half of the estate at my end went dark. they ended up with armoured cables overground for some of the supplies for a couple of months. I wonder who paid for it all? Brian

[dennis]

Early ehernet transceivers had built in TDR circuits so you could find faults. I don't know when they were phased out.

[Dave Liquorice]

A chunky TDR using pulses large enough to arc over a faulty insulator, which is probably fine on simple single line. Around here the lines branch and the branches have branches, you might know how far away a non-branch anonmaly is but probably not down which branch. A skilled operator might be able make a good guess from the waveforms though. Also attaching the TDR would require all the SIDE (Switch off, Isolate, Dump, Earth) procedure to go through and getting authorisation to do the switching before that.

Pretty sure when an insulator failed here they weren't using a "thumper"/TDR to locate it. Every few minutes there would be a brief arc over that was far more powerful than the "crack" of thumpers on Youtube and it buzzed... Next time I have the chance to chat with the linesmen I'll ask how they trace a faulty insulator.

[Andy Burns]

I realise you're probably talking about thin/thick wire coax, but some of the present-day Broadcom NICs have a driver mode that can tell cable length, and a spectrum analysis of each of the four pairs.

[Tim Watts]

I thought they did now (but I don't really know). But in the old days they used a wheatstone bridge.

[The Natural Philosopher]

Fairly sure the last time I had a power cut they said they used TDR.

If it works its accurate to a meter or so I think.

[Ash Burton]

The DNO would normally charge the cost to the party who caused the damage.

[nospam]

I spent about two years trying to get my supplier to bill my business premises properly. I kept sending them readings, and they kept billing me a stupidly small amount llke £20 (for an office with about

30 staff).

I kept paying in what I estimated I should be paying, and I got letters saying I was overpaying and should pay less. I raised a complaint, and even then it wasn't sorted out.

When the excess got to about £6k, I asked for a refund, and THAT finally sorted the problem out.

This was just beaurocratic incompetence, but it also seems to indicate that there's not much of a system of checks and balances in place.

[MM]

I had another SIX outages this morning! Starting at around 04:50 a.m. the answerphone in my bedroom woke me up, as the recorded outgoing message is spoken aloud when the power comes back on.

Then another at 05:10, 05:20 and 05:55. That's when I was getting really pissed off and phoned Western Power again. I must say that the adviser was amazingly helpful! We discussed the issue for 15 minutes while she scanned the computer (she again knew exactly to the second when the power went off). Then she went off to speak to a manager, came back and said she would escalate it to the "local team".

Then the power went off again twice more until 10:15 a.m. when it went out for 35 minutes. I thought, aha, that means they've located the fault at last. Since it came back on at around 10:50 the power has been fine, but I had to spend ages reconfiguring my TP-Link plugs. They were totally screwed. I had to reset them and start from scratch.

And THEN this afternoon I received a call from a gent at Western Power to apologise for the poor service and to explain what they had found. Went over my head rather, I have to say. Except when he mentioned the geese...

Yep, the local team had found a large flock of geese in the area of the fault and everyone was wondering whether one or two had flown into the power lines.

By the way, after the fifth outage I called Western Power again (the previous adviser told me I should) and this time it was a different adviser. And this new adviser was JUST as patient and helpful as the first one! The company really does select and train its staff well, and plaudits are due, when in this day and age we so often see a shoddy, don't care attitude.

MM

[MM]

But what if the power is only out for 10 seconds?

MM

[The Natural Philosopher]

Then there is no need is there?

If a branch drops, trips , falls off, and it reconnects later, there is no fault to find...

[The Other Mike]

Pointless when you could have a repair team on their way to the location of the fault and persons to apply the isolation and earthing to all points of infeed using the data provided automatically less than a minute after it happened.

To get that info you only need the current and voltage transformers already provided for the circuit protection and pay a few extra pounds to the protection relay manufacturer to enable the built in fault locator function.

[The Other Mike]

Fault recorders have been around for a very long time but until about 25 years ago it required interpretation of printed traces to get a reasonable estimate of distance to the fault. Remote interrogation (back then with dialup modem) and PC software brought that ability to any location even the home of the on call engineer. Now you can get the distance to fault data passed over the SCADA system as soon as it is known.

[Dave Liquorice]

That's the beauty of auto re-closers, a transient fault that causes a trip only results in a second or so outage and no need to send out a man to reset the trip. A permenant fault will trip the auto-recloser when it tries to restore supply and will quickly lock out. The PITA fault is the intermittent one that occurs at a rate just outside that required for the auto-recloser to enter lock out. Had that as well,..

[Tim Watts]

What about all the non metered load - eg streetlights and traffic lights? Any assumptions made about their consumption will have a very wide margin of error (times on, lamps blown etc).

[Tim Watts]

I've got some servers that can estimate the cable length, so those transceivers have something in them - but it may be a clever trick with signal processing rather than dedicated TDR?

[MM]

You cannot be serious! Did you not get that we had TEN outages in total?

Or perhaps you think the tree branch got up from the ground, reattached itself to the tree, then promptly fell off again?

MM

[MM]

Had I not escalated this yesterday, we might still be getting these brief outages today. Now the fault has been found and fixed and the power is as stable as my digestion, thanks to CosmoCol and an apple a day.

MM

[The Natural Philosopher]

Oh sorry. I forgot it was all about YOU.

No, they tend to flap against the wires in the wind