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68 E L EC TR I C AL CONNEC T I ON
AU T UMN 20 1 7
PATCHING INTO PATCH CORDS
P
atch cords (aka balanced
cords) are proving to be the
weak point in the reliability
of networks.
Irrespective of the quality of a
structured cabling system, poorly
performing and unreliable patch cords
are having a devastating impact on
infrastructure network operations
along with the safety and security
systems that run over them.
The performance obligation for
patch cords goes well beyond just
using appropriate cabling components
to construct patch cords. For example:
>
AS/CA S008 (mandatory), AS/NZS
3080, ISO/IEC 11801 and IEC 61935-2
all have performance requirements
for balanced cords that must be
tested at the time of manufacture.
>
AS/CA S009 (mandatory Wiring
Rules) has a general requirement that
the cabling be ‘fit for purpose’.
>
Telecommunications - Types of
Cabling Work - Declaration 2013
provides an exemption for specific
balanced cords from being deemed
as ‘customer cabling’. This allows end
users to undertake patching while
not breaching any requirements of
the Telecommunication Act 1997 or its
amendments.
>
The draft international standard
ISO/IEC 11801-1 additionally includes
environmental performance
requirements that must be met.
Further, twisted cord performance
requirements currently include but are
not limited to:
>
AS/NZS 3080
>
Return Loss
>
NEXT
>
AS/CA S008
>
Insertion loss
>
Conductor identification
>
Insulation and sheath material
>
Tensile strength and elongation
>
Cord – plug anchorage
>
Flammability
>
UV resistance (if intended for use
external to a building)
>
Conductor composition
>
Electrical withstand voltage
>
Insulation resistance
>
Metallic shield (if applicable)
On-site or workshop manufactured
patch cords are highly unlikely to
meet all AS/CA S008 and regulatory
requirements.
Other factors to be considered
should include environmental
considerations and current-carrying
and heat dissipation capabilities.
(26 AWG and 28 AWG patch cords
may not be suitable to deliver power
to a 95-100W PoE device.)
Poorly constructed twisted pair
patch cords supporting electrical load
switching equipment in a data centre
have been enough to take down the
whole data centre.
Patch cords can be tested in the
field; however, it requires the use of
specialised test adaptors. Channel test
heads are unsuitable for patch cord
testing due to the difference in gating
(associated with the plugs) when
testing a channel and a cord.
So, when specifying patch cords,
the minimum specified requirement
should be based on conformance to
AS/CA S008 to ensure mandatory
compliance, and IEC 61935-2 to
ensure performance compliance and
to help to establish the cords are ‘fit
for purpose’.
> VTI Services
www.vti.net.auPATCH CORDS ARE AFFECTING
NETWORK AND SYSTEM
RELIABILITY, WRITES VTI
SERVICES TECHNICAL DIRECTOR
MURRAYTEALE
.
Poorly performing and unreliable patch cords are having a devastating impact on
infrastructure network operations as well as the systems that run over them.
NETWORKING