Even with shielded cables a test is still required in GR-1089. It is essentially a test of how well the shielding works. The test is designed such that if the shielding is not great at least part of the surge ends up on the cable conductors.
I have found very few Ethernet ports on standard servers survive the surge with unshielded cables. Most Ethernet transceivers need to have some “above and beyond” surge protection added in order to guarantee their survival. Some customers I have dealt with do not allow the use of shielded cables on Ethernet ports. As with most things in NEBS it all comes down to the customer’s requirements. Dan From: Joe Randolph [mailto:j...@randolph-telecom.com] Sent: Monday, June 01, 2009 9:33 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] GR-1089 intrabuilding surges question 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) j...@randolph-telecom.com 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 <emc-p...@ieee.org> 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 <emcp...@ptcnh.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.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 <emc-p...@ieee.org> 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 <emcp...@ptcnh.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>
