I'm writing this while it's thundering and lightning outside. Call me wild and crazy!
I will contact LG&E this week, to see if I can get someone to come to a usergroup meeting next month or in October. Sorry, I don't remember the particulars. Harry Monday, September 1, 20037:23 PMJ. Blakejblake at win.net >Thanks, Lee, for your thorough explanation. > >Also, a few years ago, several in the group were talking about some >kind of lightening-strike protection that LG&E could install on your >house for a price. > >Does anyone know if you can still get this? And, if so.... > >1. What does it cost? > >2. How much real protection is it suppose to afford? > >3. What has been your own experience with this protection? > >TIA, > >Jane Blake > > >On Monday, September 1, 2003, at 02:29 PM, Lee Larson wrote: > >> On Monday, September 1, 2003, at 12:19 PM, Henri Yandell wrote: >> >>> However, someone has pointed out that a lightning strike will go >>> through a >>> surge protector. >>> >>> So I have the facts that: >>> >>> * Surge protectors do not protect against lightning. >>> * RJ-11/RJ-45/Cable do not 'surge' without lightning (?) >> >> I come from a family of electrical engineers, and both my brothers are >> power system engineers, so I've talked to experts about this quite a >> lot. >> >> Most of the cheap surge protectors contain cheap components called >> MOVs (metal oxide varisters). They are resistors that vary their >> resistance depending on the voltage across them. In a power strip, >> they are connected across the hot and ground wires, and when the >> voltage is increased beyond a certain threshold they decrease their >> resistance and send the current harmlessly off to the household >> ground. MOVs are sort of like a pressure valve in a plumbing system. >> >> There are a couple of problems with MOVs. >> >> First, it takes a little time for them to change their resistance. >> Power line surges are usually relatively slow, and they can react in >> time to do some good. With a lightning strike, the damage may be done >> before they can react. More expensive MOVs react faster, so you get >> what you pay for. >> >> Second, it's not too hard to burn them out when too much current >> passes through. I've opened up power strips to find the MOVs toasted >> to a crisp. They stopped that one big surge, but they weren't around >> for the next one. The more expensive surge protection power strips >> will have an LED on the outside that either lights up or fails to >> light when the MOV is cooked. Again, you get what you pay for. >> >> Better (=more expensive) surge protectors often use gas discharge >> arrestors instead of MOVs. These work under the same theory as MOVs, >> except that they consist of a glass tube containing a gas that ionizes >> when the voltage gets above a certain point. When it's ionized, it can >> conduct the current to ground. These gas discharge arrestors can react >> more quickly than an MOV, and don't burn out as easily, but they cost >> more. I guess, you get what you pay for. >> >> The surest way to protect yourself from power line surges, whether >> caused by lightning or man-made switching glitches, is with a good >> uninterruptible power supply. Many of the better UPSs have the >> computer running off the battery all the time, and the battery voltage >> is clean and constant. You plug it into the wall only to keep the >> battery charged. The charge and discharge circuits are usually >> isolated from each other. >> >> >>> so it seems that the RJ-45 etc surge protectors are a scam. >> >> I wouldn't go that far. Most of the ones I've torn apart are MOV-based >> and will work well, within the limitations of their MOVs. >> >>> Does it have to do with how close the lightning is? How does >>> lightning hit >>> an underground cable line? >> >> Lightning doesn't actually have to hit a line to generate a dangerous >> pulse. A close lightning strike will generate an electromagnetic field >> that will induce a voltage in a nearby conductor. (The conductor is >> essentially an antenna getting a very strong radio signal.) This is >> unlikely to affect a buried wire because it's surrounded by a somewhat >> conductive medium. Long above-ground runs of networking or telephone >> wires in your house can be in this EM field. >> >> A few years ago lightning hit a tree near the north end of our house. >> All the telephones were zapped and two out of the three modems were >> fried. The only one that survived was connected through the protected >> telephone jacks in a TrippLite UPS. (It also took out the >> radio-controlled garage door opener, a couple of radios and a >> television; the EM pulse probably fried their tuners through their >> antennas or the cable connection.) >> >> I keep all my computers on smart UPSs from APC, TrippLite and Belkin. >> The UPSs talk to the computers through USB or serial connections so >> the computers know to shut down when the UPS batteries are drained >> from a prolonged power outage. The power can be out for 10 or 15 >> minutes before the computer shuts itself off. (Belkin has no MAc OS X >> software for its inexpensive UPSs, but APC does.) >> >> I leave all my stuff plugged in and turned on all the time. That's >> what sleep mode is for. >> >> >> >> | The next meeting of the Louisville Computer Society will >> | be September 23. The LCS Web page is <http://www.kymac.org>. >> | This list's page is <http://erdos.math.louisville.edu/macgroup>. >> > > > >| The next meeting of the Louisville Computer Society will >| be September 23. The LCS Web page is <http://www.kymac.org>. >| This list's page is <http://erdos.math.louisville.edu/macgroup>. | The next meeting of the Louisville Computer Society will | be September 23. The LCS Web page is <http://www.kymac.org>. | This list's page is <http://erdos.math.louisville.edu/macgroup>.
