It's been a number of years since I've done any GR stuff, but with a CBN, the grounding would/should be so good that the shielding is really redundant, and ethernet is isolated to at least 1500 volts? The CBN ties everything together to a common potential, where the IBN ensures that there is a possible potential difference between the various pieces, thus the 'need' for a test. The CBN is(should) be the same potential and so a test would be superfluous(sp?), expensive?? and not needed? ps. anecdotal evidence is the easiest fixes for EMI related field problems has been CBN. Make it all common and everything bounces together, no one part sees any difference from the other, no problems anymore - CBN. ie shielded cables grounded at each end are at the same potential in a CBN - surge is silly, not needed, cost and time,
- Bill Indecision may or may not be the problem. --- On Mon, 6/1/09, Joe Randolph <[email protected]> wrote: From: Joe Randolph <[email protected]> Subject: Re: GR-1089 intrabuilding surges question To: "Gelfand, David" <[email protected]>, [email protected] Date: Monday, June 1, 2009, 9:32 PM On 6/1/2009, Gelfand, David wrote: GR-1089 clause 4.6.9.2 intrabuilding surge test has an exemption for shielded cables grounded at each end. This is supported by Verizon document http://www.verizonnebs.com/TPRs/VZ-TPR-9305.pdf clause 7.2.12.1. Does this reflect current practice? Hi David: So far I have always managed to avoid using this exemption, since my gut feel is that it might create more problems than it solves. However, as the requirements state, this is an allowable option for an installation with a CBN grounding scheme. These days most central offices use a CBN grounding scheme, but there may be cases where an IBN system is still in place. Technically, the exemption can only be used in a CBN system, although this may be hard to control in practice. I don't know what sort of intrabuilding cable you are addressing, but if it is something as simple as an Ethernet cable, it should not be necessary to invoke this exemption. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com <http://www.randolph-telecom.com/> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
