They should. Good catch.
George Zimmerman, Ph.D.
President & Principal
CME Consulting, Inc.
Experts in Advanced PHYsical Communications
310-920-3860
From: David Brandt <00000db4f15ea161-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Monday, June 10, 2024 11:46 AM
To: STDS-802-3-SPMD@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_SPMD] EXTERNAL: [802.3_SPMD] 802.3da SPMD Isolation and Environmental Clause Proposal Reflector Discussion (Comment #260 & #261)
I am wondering if the electrical specifications should refer to TCI and MPI rather than MDI and PI?
“Any equipment that can be connected to an MPSE or MPD through a
non-MDI connector that is not isolated from the MDI leads needs to provide isolation between all accessible external conductors, including frame ground (if any), and the non-MDI connector.”
Should use “balanced pair”.
“Attachment of network segments via NIDs that have multiple instances of a
twisted-pair MDI requires electrical isolation between each segment and the protective ground of the NID.”
I think we mean “Mixing segment” or if we are talking about a bridge, then “each mixing segment or link segment and other mixing segments and link segments”.
“An Environment A multiport NID does not require electrical power isolation between
link segments.”
I’m not an expert in this topic, but this seems unusual. Where does it originate?
“An Environment A MPSE shall
switch the more negative conductor. It is allowed to switch both conductors.”
If J.1 comes from “ITU-T Recommendation K.44”, then it ought to be clarified. I.e.,:
“This electrical isolation shall meet the isolation requirements as specified in
ITU-T Recommendation K.44 J.1
FYI, ODVA references: “SELV/PELV UL/CSA/IEC/EN 61010-2-201” (Safety requirements for electrical equipment for measurement, control, and laboratory use – Part 2-201: Particular
requirements for control equipment”, which has full requirements on isolation and degrees of insulation.
- 6.2.102.2 SELV/PELV circuits
- 6.5.2.101.3 Class II equipment
- Annex BB System drawing of isolation boundaries
-----------------------------
IEEE P802.3da:
From: Jason Potterf (jpotterf) <0000142267c8912c-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Monday, June 10, 2024 10:05 AM
To: STDS-802-3-SPMD@xxxxxxxxxxxxxxxxx
Subject: EXTERNAL: [802.3_SPMD] 802.3da SPMD Isolation and Environmental Clause Proposal Reflector Discussion (Comment #260 & #261)
[Use caution with links & attachments]
The D1.2 Draft had placeholders for both the Isolation Sub-Clause (169.6.1) and the Environmental Sub-Clause (169.7). I have submitted comments #260 and #261 with suggested text to fill in these
chapters. The suggested text is attached to this email for review ahead of our meeting this week. Our meeting time is limited this week, so I have elected to not present this but instead hold a discussion on the reflector. Please respond here if you have any questions
or comments.
Executive Summary
-
Isolation sub-clause 169.6.1 proposal was adapted from 4-Pair PoE Clause "145.4.1 Electrical isolation" and PoDL "104.6.1 Isolation" sub-clauses, with the two sections merged and requirements relocated so that they apply to one
of three environments, A, B, and C.
-
MPOE Environment A and B are leveraged directly from 4-Pair PoE
-
MPOE Environment C is leveraged from PoDL and provides a lower isolation requirement for environments
"When a LAN or LAN segment, with all its associated interconnected equipment, is entirely contained within a single low-voltage power distribution system contained within a single cabinet, vehicle, machine, or other power domain where ground loops are unlikely
to occur."
-
Note: This Environment C definition text is new text proposed by me and not leveraged from existing standards.
-
Environmental sub-clause 169.7 was adapted from 4-Pair PoE "Clause 145.6 Environmental" and PoDL "104.8 Enivronmental."
-
This was mostly a straightforward merge of the requirements from these two sections.
-
The only original text proposed by me is the "169.7.7 Labeling" item
"e) Indicate any non-MDI connectors which are not isolated from the MDI leads".
-
The intent is to address field issues observed in 4-pair PoE systems where isolation is omitted, as permitted by this language:
-
"Any equipment that can be connected to an MPSE or MPD through a non-MDI connector that is not isolated from the MDI leads needs to provide isolation between all accessible external conductors, including frame ground (if any),
and the non-MDI connector."
-
PoE PDs that take advantage of this language pass the burden of isolation on to devices attached via non-MDI connectors, but often do not indicate which ports are only allowed to connect to isolated devices. Installation of these
devices that then connect to grounded equipment via this non-isolated connector results in violation of the isolation requirement and can cause significant electrical issues in buildings.
-
An example of this defect seen in the wild is a non-isolated PoE splitter in a plastic case that was used to power a non-isolated device in a metal chassis. The non-isolated device grounded one side of the splitter output circuit
to the chassis. Installation of large numbers of these splitters on the same multi-port Environment A PSE device resulted in ground loops in the building and unexpected current return paths.
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