North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Sheilded Cat-5E Ground Loop - Myth or Reality?
> None of his is specific to Cat-5e installations but is common to ALL > electrical installations. This does NOT apply to telco cables run outside, often run on the same poles parallel to power wires for miles, grounded at many points in a MGN (Multi Grounded Neutral) environment where, like it or not, the earth carries considerable current. Opening a shield ground in this environment is bad. ----- Original Message ----- From: "Kevin Oberman" <[email protected]> To: "Christopher K. Neitzert" <[email protected]> Cc: <[email protected]> Sent: Wednesday, April 10, 2002 2:17 PM Subject: Re: Sheilded Cat-5E Ground Loop - Myth or Reality? > *This message was transferred with a trial version of CommuniGate(tm) Pro* > > > Date: Wed, 10 Apr 2002 17:43:50 +0000 (UTC) > > From: "Christopher K. Neitzert" <[email protected]> > > Sender: [email protected] > > > > I'm in the process of managing cabling for a large install (500-ish runs) > > and a vendor came to me with a story about the creation of ground loops in > > running sheilded+gounded cat-5e in large installations. > > > > Does anyone have any experiences they would like to share regarding this? > > Just follow standard rules for grounding. If the shield is connected > to anything, it should only be connected at one end! This is really > always true, but is especially true when there is significant physical > distance involved as this can result in current flow between the > grounds. This will almost certainly create a significant hum > field. Due to its excellent common mode rejection, this may not be a > real problem, but it always deteriorates S/N margins to some extent. > > There is also a REAL safety issue! Make sure that ground is NOT > exposed at the un-grounded end. A potential of many volts can occur, > especially in areas subject to thunder storms. > > None of his is specific to Cat-5e installations but is common to ALL > electrical installations. > > R. Kevin Oberman, Network Engineer > Energy Sciences Network (ESnet) > Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) > E-mail: [email protected] Phone: +1 510 486-8634 >
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