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Thread ID: 26411	2002-10-26 21:10:00	Underground Phone Cables	Danger (287)	Press F1

Post ID	Timestamp	Content	User
93300	2002-10-26 21:10:00	As all the phone cables in my area are underground, is there any need to run my phone line through my surge protector? Lightning isn't going to strike the lines underground, and it slows my connection slightly.	Danger (287)
93301	2002-10-26 21:22:00	>Lightning isn't going to strike the lines underground don't be to sure of that. high voltage can be induced into the lines by a nearby strike. i've also had it where the exchange itself got it and fried a lot of pc's and phones in peoples houses.	tweak'e (174)
93302	2002-10-26 21:55:00	Ok, thanks tweak'e. I'll leave it connected then.	Danger (287)
93303	2002-10-26 21:58:00	Better to be safe than sorry, I would think. BALDY:-)	Baldy (26)
93304	2002-10-26 22:01:00	The main problem relates to EPR, or Earth Potential Rise, which can induce high voltages into underground cables. In the worst cases the communications cables can be "peppered" or suffer massive numbers of small perforations to their insulation. Localised areas of ground can be raised to quite high voltage, relative to surrounding areas by lightning strikes, or HV power cable failures. Having said that, unless you paid several hundred dollars for your surge suppressor it will only protect for the less severe cases. The chances of surges due to lightning in an urban underground area are much reduced, and I will admit to never using a suppressor and never losing any equipment to lightning surges, in the last 15 years. Tempting fate or what!	godfather (25)
93305	2002-10-26 22:39:00	a surge protector for your phone line is to protect you from exactly that. if you get a power cut and it affects your local telephone exchange and when it comes back online (so to speak) it would send large amounts of electricity down your line frying anything that it comes in touch with. It can severilly destory a modem or fax. It happened to me once that is why we got a surge protector with a line in and line out.	Beef (1415)
93306	2002-10-26 22:44:00	If you can get a cheap UPS that is much better	kiwibeat (304)
93307	2002-10-26 22:59:00	> a surge protector for your phone line is to protect > you from exactly that. > > if you get a power cut and it affects your local > telephone exchange and when it comes back online (so > to speak) it would send large amounts of electricity > down your line frying anything that it comes in touch > with. > > It can severilly destory a modem or fax. > > It happened to me once that is why we got a surge > protector with a line in and line out. The telephone exchange doesn't send "large amounts of electricity" down the line. After a power outage, the restoration of power causes "ferro-resonance" effects in the distribution transformers which give rise to strange wave-shapes and frequencies for a few milliseconds, to a few seconds. Also, depending on the cause of the outage, the EPR that resulted could easily have done localised damage, which you would not be aware of until the power came back on. Its likely this which caused your problems. If it was the exchange it would have resulted in millions of dollars worth of damage. And trust me, if "large amounts of electricity" did come down your phone line, your surge diverter would be the first casualty. In this area, the fault current on the power system can reach 25,000 amps (25 kA). At 230 volts, this has a power equal to 5.75 million watts, or 5,750 kW (Imagine the heat output of 5 million single bar heaters). Now can a small surge diverter actually absorb that, even for a fraction of a second? No. However small spikes on the supply or phone line can be absorbed non destructively, just don't assume a major fault will be diverted. I still think they are cheap insurance, and in a rural area I would definately use one.	godfather (25)
93308	2002-10-26 23:03:00	> If you can get a cheap UPS that is much better No its not actually, as a cheap UPS has you hard connected to the maiins (perhaps with some limited filtering) until the power fails, then they switch over to inverter power in a few milliseconds. By then any surge has already gone straight through. More expensive ones always run on battery inverter, and the battery is charges from the mains continuously. These are usually better.	godfather (25)
93309	2002-10-27 01:03:00	Well said God :) Very forthright, lucid and above all, accurate responses to classic misinformation. I'm glad to see that you are back to your old omnsicient self again. :D Do I smell an embryonic FAQ in there somewhere ?:| Cheers Billy 8-{) :D :D :D	Billy T (70)
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