Of course, occasionally, a buried phone cable gets cut by someone with a backhoe and takes out phone and data service for a large number of people. And my understanding is that repairing this sort of thing takes a long time because each individual wire needs to spliced.
Increasingly, trunk routes for the phones will be on a ring so if one path gets broken the signal goes around the other side of the ring. Some systems test both paths constantly and use whichever one happens to be performing best.
Power is sometimes taken out on purpose, as parts of the grid are repaired, so you even lose power at times when your home was originally unaffected.
In the aftermath of numerous rain storms in the NE, many electric customers lost power 24-48 hours after any damage was being caused to any equipment; they lost power when crews took them off line.
Do sections of the power grid ever ‘trip’ do to surges/spikes/lightning and such? If so, there’s another vulnerability low-voltage phone lines don’'t have.
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Philster touched on one of the answers. Power lines rarely “go down” during normal storms. You see the powre lines down in hurricanes or when a tree falls on the line. What usually happens is that the line touch or a part of the grid gets struck by lightning. When that happens safety breakers, or even really big fuses, kick out to protect the grid from a voltage surge. The result of the breaker or fuse going out is that you lose power. The phone tays up because it is not connedcted to the power grid and is not subject to precautionary interruptions.
The lenght of the outage is directly proportional to the length of time it takes for the powere company to locate the tripped breaker or blown fuse and reset it (verifying, of couse, that the cause for the surge is no longer preset).
Power lines don’t just have simple breakers and fuses on them. They use what are known as automatic reclosers.
When a breaker blows in your house, you have to go down to the basement and turn it back on. When a protective device trips on a power line, it may be miles away, and it’s not so trivial for the power company to reset. Since most power faults are transitory (wind blows the lines together, or blows a tree branch onto a line, for example), the automatic recloser attempts to reconnect the line. Reclosers are programmable, so their programming varies a bit, but typically they try once or twice fairly quickly, as in within a couple of seconds, and then try again after a longer delay, typically a couple of minutes later. If the fault still persists, the recloser gives up, and then a lineman from the power company has to go figure out what is wrong.
If the power goes out for any length of time, you can bet it needs more than a breaker reset to get it going again.
Former BellSouth tech here. Unless we had a MAJOR storm hit the area, we had very few customers who lost service. Usually airal phone lines don’t go down, the individual lines running to your home are very light and even when whipped around usually won’t pull themselves out. The larger “feeder” cable is quite heavy, but rarely have I seen one down on its own. If they are down, it is usually due to a tree falling on the lines, car hitting a pole or similiar event.
The previous posters are correct that the Telco maintains an impressive backup system for power. The voltages are low in telephone usuage. Usually each slic cabnet (a place where computer cards controll the lines) or CO (central office) has its own backup. Those that don’t are suppled by mobile backup units.
As far as the insulation on telephone lines it serves three main purposes. One, to keep the individual wire seperated as if they touch you loose dial tone, no sparking or anything. Two, to minimize a condition known as crosstalk. If the integrity of the insulation is comprimised it is possible for conversations from other lines to “bleed” into your line. Lastly the insulation is there to keep out water. Water entering a cable can cause crosstalk and can cause a “grounding” of the line that will make the line noisy at best and inoperable at worst.
Most newer telephone plant (infastructure) is buried. While it costs more to do it that way, the lines are less susceptible to damage and cosmetically it is better for the community not to see wires running everywhere.
When I was a teen in the mid to late 70’s and we lived in the country, we lost our phone perhaps around once a year.
This happens on power transmission lines too. That’s why it’s the transmission “grid” versus “radial” distribution lines.
Also, for what it’s worth, there’s a huge amount of power in a power system. Like HUGE. When there’s a fault on the telephone line, it cuts that circuit, that’s it. Like turning off a light switch. But when there’s a fault on the power lines, you get thousands of amps of current. Unchecked, that power destroys transformers and melts power lines. Unquenched arcs can persist indefinitely (like a lightning bolt that doesn’t stop striking). The way the utilities deal with this is through “protective relaying” or just “protection”. There are relays everywhere. Every single breaker is controlled by a relay that senses the conditions on the line. Current goes up, the breaker trips. Too much ground current? The breaker trips. Undervoltage? Trip. The difference in current between this side and that side of the transformer is too great? Trip the breaker.
Now, they don’t use every scheme everywhere, but in general, every part of the power system has a primary and backup protection scheme, and those sections have to overlap. There is a balancing act between saving money by not cutting off service, and saving money by not letting million-dollar transformers get destroyed. Since the power and, hence potential destruction, is so much greater on the power system, the balance tips farther towards “service disruptions” than it does in the phone company.
Finally, the power grid is supplied with power by synchronous generators, which are all in sync across a wide geographical area (like the entire western US). Certain situations can happen which cause power system instability, which causes voltages to swing up and down, frequencies to go out of whack, and a cascading effect of protection systems shutting down power in a race to stabilize the system. This is how entire regions lose power like in the northeast blackout of 2003. I don’t think there is any analog to this in the telephone system.
When the power went down for seven hours in all of San Diego last Thursday the power company sent an email to their customers informing us of the situation. That may seen like a dumb joke, but I got the message on my cell phone when the tv and 2/3 of the radio stations were not operating.
Your OP is confusing, since it’s not clear if you intend “go down” to mean[ul][li]cease to function as part of the system, or [/li][li]physically fall down to the ground.[/ul][/li]
For the second one, I can give some reasons:[ul]
[li]Power lines are heavier, thus fall down more easily when stressed.[/li][li]Power lines are bigger, thus accumulate more ice, which can weigh enough to bring them down.[/li][li]Power lines are harder & more expensive to bury, so they are more likely to still be aerial lines exposed to weather.[/li][/ul]
[quote=“t-bonham@scc.net, post:31, topic:596064”]
Your OP is confusing, since it’s not clear if you intend “go down” to mean[ul][li]cease to function as part of the system, or [/li][li]physically fall down to the ground.[/ul][/li][/QUOTE]
Exactly. Your electricity goes off only once for 5 seconds. You know it. Your phone goes off for 5 seconds ten times a day. You never know it.
Which wire is down more often? Only assumption (no hard facts and numbers) say which is ‘down’ more often. Casual observation (no hard facts and numbers) too often creates myths. Even the OP’s hypothesis is based in assumptions that are questionable.
So I have read through this thread and still wonder about it. A couple of years ago down the block from me a tree fell over breaking the uppermost wire, the high voltage one. The low voltage lines held it protecting the phone and cable below them.
It was back where bucket trucks don’t go. There were other near by trees. The guys with the orange trucks brought in a climber to nibble away the leaning tree. When he was done, then the electric company could repair the high voltage line.
A lot of the trees I see down take out everything. I don’t see how the phone can function, but still, quite often you can call the power company to report an outage.
My cable company has installed a bunch of neighborhood battery back ups. In many of the more recent outages, I throw the interlock, fire up the generator and go back to surfing the net.
[quote=“thelabdude, post:33, topic:596064”]
A lot of the trees I see down take out everything. I don’t see how the phone can function, but still, quite often you can call the power company to report an outage. QUOTE]
One other thing to keep in mind is that if a telephone line comes off the pole (comes down) it is still possible for phone service to work. Unlike power lines which would ground immediately, as long as the cable isn’t broken, the phone will continue to operate.
Also, for some of you discussing lines on poles vs. lines buried. The biggest reason to see poles is the fact that is incredibly more expensive to bury cable and it is much harder to repair buried cable when damage does occur (although buried cable suffers damage less often).
When a cable is buried you have to find the fault before you can repair it and at times this can be difficult because you don’t have any idea what the path of the cable is. (this is true for the cable that runs from the street to your house. The feeder cable that runs to the CO is well mapped and usually run through pipe.) The cable that runs from the street to your house must be dug up to repair and that means locating the cable in your yard. We have tools to aid in this, but they do take some experience to operate correctly. I remember once when I was a new tech trying to fix a ground fault in a lady’s yard. By the time I found the fault, her front yard looked like a gang of gofers had invaded. I located every thing in her yard (cable TV, water pipes, etc) but the telephone cable. I wonder it the grass every grew back! :smack:
No, the uppermost wire is a ground wire (no-voltage), to protect the high-voltage ones (and hopefully be the path for any lightning strikes). Below that there are usually 2 wires (or 3), and they are both equally high-voltage; opposite sides of the same circuit, in fact.
At least, that is the common design here in the US.
Not so sure about that. Looking out my window. Top wire is connected to the transformer. It was the one they disconnected and grounded before the climber climbed. It is also the only one that continues past that point.
Down a ways are 3 closely spaced wires, what my SE connects to. The top one of them is the ground. On down a ways is the cable. Phone wire is lower yet, buried. So where you just have have the ground and 2 legs of the 120 v, the top wire is ground. Add the highvoltage, and it is up where you can work on everything else without getting near it.
I leashed up the dog and went nibbing that day observing details like the hot high voltage wire being disconnected limiting the outage area. That was when I found out those new boxes that had appeared were the cable back up. When you have a Golden for people to pet, they are friendly and answer questions.
Climbers are highly skilled and methodical workers. Watching them is very interesting, but becomes tedious.
You are very correct. You have to be methodical as one mis-step and things go bad very quickly. The reason that I am a former BellSouth tech is I “cut out” (fell) while climbing a pole. I was about 20ft high at the time. The fall wasn’t too bad, but the landing that was a real biatch. Broke my back and can no longer work. Climbing is really a lot of fun, but is very dangerous and should never be attempted without proper training.