Can a short circuit between live and ground destroy a telephone line ?

[radiolistener]

Based on the description, the most likely cause of the telephone cable damage is that during the short circuit, a large current began to flow through the telephone pair, leading to the burning out of the wire.

[SteveThackery]

IF there is a fault with the protective earth of the building, perhaps a high resistance joint, and IF there is surge suppression fitted to the phone line that is intended to discharge to earth, then would it not be possible for some of that short circuit current imparted into the protective earth cabling to be dissipated through the surge arrestor into the telephone wiring?

I've already dealt with this higher up the thread. It's better to read all the replies before adding your own.

I read your reply, I considered it, and then decided to add my own anyway.

Is there something wrong with doing so?

The idea of a conversation in a forum like this is for us all to share our ideas in such a way that collectively we home in on the correct solution. Putting aside misconceptions is how we make progress towards the truth.

What you did was reintroduce a misconception that had been dealt with much earlier in the thread, and therefore you undid a significant amount of the progress we had made. This required someone (me, in this case) to waste their time explaining again why your suggestion had already been considered and put aside as extremely unlikely.

Your post added nothing useful (because it was simply repeating someone else's post) and actually detracted from the progress of the thread by throwing in a distraction that could mislead people.

Obviously anyone can post anything anywhere (moderators permitting), and I wouldn't dream of trying to stop you. But you should expect to be challenged.

[SteveThackery]

Based on the description, the most likely cause of the telephone cable damage is that during the short circuit, a large current began to flow through the telephone pair, leading to the burning out of the wire.

At first glance, yes, obviously. But we have the challenge of working out how the mains fault could lead to a large current in the telephone wire. That's the bit that needs a credible explanation.

[floobydust]

Part of the picture is still missing.

[...] We called a technician (who wasn't briefed on the whole story) and he discovered that one pair of the phone line was dead. The other pair was working, he made the switch (it didn't cost anything) and the problem was solved. [...]

At the house you have access to the other pair but how did it get switched at the other end? My phone exchange is 2km away.

[tigrou]

Part of the picture is still missing.

At the house you have access to the other pair but how did it get switched at the other end? My phone exchange is 2km away.

The phone exchange box is 500m away from the house. Switching pairs is probably as simple as unplugging 2 wires and plugging two others into some slots.
Not sure if it anwser your question.

[floobydust]

I wondered how far the tech had to walk/drive to switch to a new pair.
If it failed due to corrosion or a loose terminal, it would have been acting up earlier possibly as slow (DSL) data, or you would hear crackling if a landline.
Over-current melting the wire (fusing) would make smoke and burn conductors adjacent to it. So that seems unlikely it was destroyed that way.

Second, so far we have no electrical path between your home's PE ground and the phone line.

[tooki]

IF there is a fault with the protective earth of the building, perhaps a high resistance joint, and IF there is surge suppression fitted to the phone line that is intended to discharge to earth, then would it not be possible for some of that short circuit current imparted into the protective earth cabling to be dissipated through the surge arrestor into the telephone wiring?

I've already dealt with this higher up the thread. It's better to read all the replies before adding your own.

I read your reply, I considered it, and then decided to add my own anyway.

Is there something wrong with doing so?

The idea of a conversation in a forum like this is for us all to share our ideas in such a way that collectively we home in on the correct solution. Putting aside misconceptions is how we make progress towards the truth.

What you did was reintroduce a misconception that had been dealt with much earlier in the thread, and therefore you undid a significant amount of the progress we had made. This required someone (me, in this case) to waste their time explaining again why your suggestion had already been considered and put aside as extremely unlikely.

Your post added nothing useful (because it was simply repeating someone else's post) and actually detracted from the progress of the thread by throwing in a distraction that could mislead people.

Obviously anyone can post anything anywhere (moderators permitting), and I wouldn't dream of trying to stop you. But you should expect to be challenged.

I feel it important to point out that you two did not discuss the exact same thing. Steve, you spoke specifically of “lightning protectors”, while SmallCog spoke of “surge protectors”. And this matters because those aren’t the same thing!

A kinder way of dealing with this might have been to say “oh, when I said ‘lightning protector’ above, I actually meant surge protectors, so we already discussed that a bit”.

And unless I am overlooking something, I don’t see the topic discussed or “dealt with” above other than saying that it’s extremely unlikely that such a device is installed. To me that doesn’t constitute a misconception, nor a resolution to one.

[SteveThackery]

I feel it important to point out that you two did not discuss the exact same thing. Steve, you spoke specifically of “lightning protectors”, while SmallCog spoke of “surge protectors”. And this matters because those aren’t the same thing!

There are no surge protectors on telephone lines, and as of several decades ago no lightning protectors either. (Actually there may be the odd one that didn't get recovered, but they didn't trigger on mains voltages anyway.)

[SteveThackery]

And unless I am overlooking something, I don’t see the topic discussed or “dealt with” above other than saying that it’s extremely unlikely that such a device is installed. To me that doesn’t constitute a misconception, nor a resolution to one.

It is resolved in as much as there is nowhere further to take it, because we cannot know for sure. What we do know for sure is that those protection devices weren't triggered by mains voltages anyway. As I say, resolved in the sense that it's a dead end.

[Gregg]

Here is a picture from a telco main office where a sparky grounded out a bus bar in a 48 volt nominal 53 volts battery float power distribution panel and blew a 600 amp fuse.