IEEE Std. C62.41.1 (2002 - reaffirmed 2008) contains a mountain of
information. If you go to A.2.2.3 Voltages induced in cables adjacent to
down-conductors, it covers the induced voltage in an open-circuit loop
by a nearby lightning current. The induced voltage table gives values
ranging from 50 V to 500 V. Do the same calculation for Ethernet cables
and you end up with voltages in the kV region. The inclusion of a
voltage limiter is not covered. The poor coupling between the source and
victim means that the voltage limiter current is surprisingly small.
My previous comments are comprehended with statements like "The
resulting voltages induced in the loop by the fast-changing surge
currents flowing in the grounding system can cause a large voltage
difference between the power port and the telecommunications port".
Hence paving the way for the use of MSPDs to reduce the inter-service
voltage differences for equipment or equipment clusters.
At the time of document creation, MSPDs where not widely used and in
Annex D called "surge reference equalisers". To understand how the MSPD
transfers the surge on one service to another you need to look at more
modern documents like ITU-T recommendation K.98 (08/2014) Overvoltage
protection guide for telecommunication equipment installed in customer
premises. This Recommendation covers direct strikes to the incoming
service feed, mains configuration types of TN-S, TN-C, TN-C-S, TT and IT
together with effects of various earthing system lead lengths and earth
electrode resistances.
Time is running out for IEEE Std. C62.41.1, under new IEEE rules the
life of a standard is 10 years. If nothing is done to revise C62.41.1 it
with be withdrawn in 2018. Hopefully the IEEE PES Surge Protective
Device Committee will take up this challenge and, as part of the
revision rational, replace the 10/350 with the more realistic values
from CIGRÉ Technical Bulletin (TB) 549 (2013) Lightning Parameters for
Engineering Applications
Regards,
Mick Maytum
Safety and Telecom
Standards
[email protected]
https://ictsp-essays.info
------ Original Message ------
From: "Richard Nute" <[email protected]>
To: [email protected]
Sent: 18/09/2017 18:58:00
Subject: Re: [PSES] power strip details
Hi Ralph:
Thanks for the reference. My comments are validated by ANSI C62.41.1 .
Best regards,
Rich
-----Original Message-----
From: Ralph McDiarmid [mailto:[email protected]]
Sent: Monday, September 18, 2017 9:01 AM
To: [email protected]
Subject: Re: [PSES] power strip details
Pardon me, the correct reference is ANSI C62.41.1 (finger trouble on
keyboard)
Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric
-----Original Message-----
From: Ralph McDiarmid
Sent: Monday, September 18, 2017 8:55 AM
To: [email protected]
Subject: RE: [PSES] power strip details
While I agree that an SPD at the service entrance seems to be the way
to suppress surges resulting from direct/near/far lightning strokes,
ANSI C62.4.1 writes about switching transients on circuits which cause
oscillatory surges on the mains. SPD at service entrance might be less
effective for those. The ANSI standard seems a very good summary of
what is a complex topic.
Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric
From: Richard Nute [mailto:[email protected]]
Sent: Saturday, September 16, 2017 12:30 PM
To: [email protected]
Subject: Re: [PSES] power strip details
I believe the principal culprit is the extreme magnetic field that
surrounds the conductors when the surge protector operates rather than
the current in the PE conductor. This field can generate high voltages
in adjacent and nearby low-voltage conductors such as telephone and
data cables. Think air-core transformer.
If the surge protector is at the service entrance, then the high
current is in the electricity supplier wires, and the coupling to
telephone, cable, and data cables is reduced due to the distance
between the wires.
http://www.nemasurge.org/faqs/
Rich
From: mickm [mailto:[email protected]]
Sent: Saturday, September 16, 2017 1:40 AM
To: mailto:[email protected]
Subject: [PSES] power strip details
John,
It seems to me that TC 108 documents really devise surge protection
component tests rather that complete equipment tests and so miss some
hidden field gotchas.
I with Richards point about surge protection, for me the concern is the
surge current being diverted into the PE system creating local PE surge
differential voltage rises.
Multi-service surge protective devices (MSPDs) - all in one surge
protection (mitigation actually) - can cause problems here by
transferring a surge on one service, say AC mains, to another service
e.g. telephone service, because that service feed offers a better path
for the diverted surge current than the PE connection.
Equipment connected to the protected output of the MSPD should survive
the surge, but equipment connected on the unprotected side may suffer
due to the unexpected diverted surge. Solution, put and MSPD on every
bit of equipment. Looks like a win-win situation for MSPD
manufacturers.
Regards,
Mick Maytum
Safety and Telecom
Standards
mailto:[email protected]
Ictsp-essays.info
------ Original Message ------
From: "John Woodgate" <mailto:[email protected]>
To: mailto:[email protected]
Sent: 16/09/2017 08:04:59
Subject: Re: [PSES] power strip details
I agree, but doesn't that also apply to surge-suppression built into
equipment? Should we stop requiring surge immunity testing on
equipment?
With best wishes DESIGN IT IN! OOO – Own Opinions Only
http://www.jmwa.demon.co.uk/ J M Woodgate and Associates Rayleigh
England
UK is a sovereignty, not a Zollverein-ty
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