I am updating a garage submain for a customer. Its on a 35m overhead cable, supported by a broken catenary wire shared with the neighbour. My customer want's their own independent support wire. This means there will be two catenary wires running in parallel. I assume there is some risk of chafing in high winds if the wires are very close, how do I calculate a suitable separation distance. In terms of installation complexity the closer I can get them the easier it is for me.
If you work out the sag distance of your loaded wire, and estimate the sag distance of the existing neighbours' one, when it is repaired. Adding these two, plus a small margin would give a separation distance where they would never contact, even if the wind was creating a "double dutch" skipping rope effect.
I was thinking the wires could be much closer though with rods bolted between the two wires keeping them separated, like a ladder. And provide a back up to each other if either wire failed.
plus a small margin
The margin would need to consider the increase in sag as the catenaries and suspended cables age.
I was thinking the wires could be much closer though with rods bolted between the two wires keeping them separated, like a ladder. And provide a back up to each other if either wire failed.
Although depending on wind conditions, that might cause more problems than it solves as it might change the response to (and propensity for amplification of) standing waves.
But like guitar strings and fingers on them, the frequencies get higher. But I take your point, there is more room for chaos theory to rear it's head.
I don't think it's very common in the country in general, but stockbridge dampers are fitted to some pole-spanning copper telephone cables near me (on the coast in the North West).
I was surprised how slack (in comparison to copper) the overhead fibres have been strung in the area. bunches of them clatter a lot in moderately high wind, and they certainly hum and sing in high wind. I believe they are more resilient to damage than copper ...
agree too avoid any entanglement under any local reversal of gravity or other abnormal condition, the terminations must be spaced wider than the sum of the two mid point sags. However, in practice, no normal weather condition does this, and the spacing can actually be about half this.
Round here, the more exposed runs of 11kV are run one above the other rather than side by side, so that the lower one would have to actually invert to have a clash - which is pretty much unheard of.
I think its more a case that the fibres have a lower ultimate tensile strength than the hard drawn copper and you cannot pull it too tight, we have the same round our way, and even on similar spans the tensions used seem very variable, so there may be an element of speed working and paid by the job, rather than rigorous engineering to a specific tension as we have multiple pole to pole spans that are in parallel and vary from droopy to very droopy...
Mike.
so there may be an element of speed working and paid by the job, rather than rigorous engineering to a specific tension as we have multiple pole to pole spans that are in parallel and vary from droopy to very droopy...
Agreed ... the issue where I live is (as alluded to in previous e-mail with Stockbridge dampers on some main pole-to-pole distribution links)) regular high winds and damaging gusts.
However, we have the backup now of 4G/5G.
backup now of 4G/5G
Is not as good as the old hard lines and exchange batteries, a lot of the in-fill base stations don't have batteries or if they do they are comparatively a very short duration. Add to that the fact that user end of the fibre requires power all the time, not just during a call, and the emergency provision is much thinner than it once was. Its quite interesting to look at what happened with the Lancaster flood, which took out a main substation, and how quickly all sorts of plans came unstuck (like the local authority web pages for example.) It's only become more brittle since then. I do have a stock of tinned food and a camping stove...
Mike.
Is not as good as the old hard lines and exchange batteries
But the only way to keep the fibre broadband up in a power cut is to provide battery backup my end too, for at least the fibre uplink modem, and the main router that the modem's Ethernet output is connected to.
and the emergency provision is much thinner than it once was
We barely use our house telephone line for calls, so I see no point in paying for VOIP after we go all fibre next year. The reason why we have kept it, along with one hard-wired handset, is for a dire emergency.
and the emergency provision is much thinner than it once was
We barely use our house telephone line for calls, so I see no point in paying for VOIP after we go all fibre next year. The reason why we have kept it, along with one hard-wired handset, is for a dire emergency.
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