Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site aesat.UUCP Path: utzoo!aesat!rod From: rod@aesat.UUCP (Rod Gilchrist) Newsgroups: net.lan Subject: Re: inter-building ethernet grounding Message-ID: <216@aesat.UUCP> Date: Wed, 29-Aug-84 10:48:28 EDT Article-I.D.: aesat.216 Posted: Wed Aug 29 10:48:28 1984 Date-Received: Wed, 29-Aug-84 11:14:04 EDT References: <433@cornell.UUCP> Organization: AES Data Inc., Mississauga Ont., Canada Lines: 33 <> About that 1,000,000 volt transient .... There is a body of knowledge out there related to lighting strikes. In particular the problem has cropped up in both telephone and power transmision industries (ever notice that your telephone doesn't seem to have much trouble with lightning, even though the wires are unsheilded and hung up in the air?). I believe the initial telephone papers were published in the Bell Systems Technical Journal in the fifties or early sixties describing work done to measure lightning induced transients (sorry I can't be more specific, its been a while since I was involved in this). What was discovered is that although there is the occasional induced voltage that was unmeasurable because it destroyed the measuring equipment, in the very large majority of the cases the transients were less than 2000 volts. The numbers I recall are that 95% of all strike induced transients on (buried) coax cable were measured to be less than 700 volts, with a duration of in the order of 100 microseconds (they were more like 1500 volts with a shorter duration on twisted pair). One result of the work done was an IEEE standard for power system measuring equipment that requires that signal wires be capable of with standing about 50 one microsecond, 2000 volt spikes one millisecond apart. This is intended to insure that it is very unlikely that the equipment will be damaged by lighting or other transients. I'm not familiar enough with ethernet transcievers to relate the above to them, but I thought I would pass this much along. --- Rod Gilchrist @ AES Data Inc 1900 Minnesota Court Mississauga, Ontario, L5N 3C9 416-821-9190