>From http://www.verizonnebs.com/TPRs/VZ-TPR-9305.pdf
7.2.12.1.
"Verizon has revised its long-standing installation practices and now allows
shielded cables to be grounded at both ends when in the common bonding
network. Therefore, the GR-1089 Intra-building Lightning Surge Tests
(Telecommunications Port) statement that "these tests do not apply if
intrabuilding wiring (cabling) is shielded and the manufacturer's
documentation states that both ends of the shield must be grounded" is now
applicable for equipment that will be installed in the CBN."
David
________________________________
De : [email protected] [mailto:[email protected]] De la part de Dan
Roman
Envoyé : Tuesday, June 02, 2009 9:42 AM
À : Joe Randolph; [email protected]
Objet : RE: [PSES] GR-1089 intrabuilding surges question
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:[email protected]]
Sent: Monday, June 01, 2009 9:33 PM
To: [email protected]
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)
[email protected]
http://www.randolph-telecom.com <http://www.randolph-telecom.com/>
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