Thanks George,
I’m trying to imagine what my thought process would have been…
The SuggestedRemedy did suggest a separate test, but just for impulse [option c)]
- If removed for impulse testing, the voltage limiter shall pass the impulse test when separately tested.
Testing must be for “at least one of” a), b), or c). MOVs are specifically designed to pass c).
The resistance after the test of 2M Ohm @ 500 Vdc says “after the test”. I now note that it does not say if this is before putting the components back in place.
- If done with removed components, then the test should pass.
- If MOVs were not removed, they are likely damaged.
I also notice one other very interesting point: "Voltage limiters intended to prevent Ethernet port insulation breakdown”. It reminds me of motor cables, where the cable length is limited to prevent transmission line effects from multiplying
the voltage due to reflection. The higher voltage can break down the winding insulation and the motor fails. I imagine the transformer insulation could break down in the same way. The MOVs can serve to protect the insulation barrier.
This article discusses system-level implications of surge protectors introducing mains surges into imperfect site grounds and then additional equipment surge protectors introducing the ground surge across cables to damage connected equipment.
(Maytum is referenced.) This reminds me of shielding, where the shield is supposed to protect the communication signals - but the termination becomes an entry point for interference. Drives are a prime example, where they create ground interference that can
come back through the shield of the attached Ethernet. Separate PE and FE is one installation remedy. Unshielded cables can prevent the coupling, but isolation needs to be adequate. Isolation is sometimes a better strategy than shunting.
Regards,
Dave
From: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
Sent: Thursday, July 18, 2024 7:16 AM
To: STDS-802-3-PDCC@xxxxxxxxxxxxxxxxx
Subject: EXTERNAL: Re: [802.3_PDCC] voltage limiter comment from Annex J SA ballot
[Use caution with links & attachments]
David – my recollection is that there were varying opinions (hence not something easily captured in a response statement), but for my part, I recall objecting to removing components without some
limitation or test on those components. Under that policy (in my opinion, to my recollection as a member of the CRG) the proposed change created a way to bypass the intention of the specification.
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: Wednesday, July 17, 2024 10:48 PM
To: STDS-802-3-PDCC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_PDCC] voltage limiter comment from Annex J SA ballot
Hi All,
I’m now on the PDCC reflector. I see one recent message relevant to my presentation.
Do we know why the CRG disagreed?
--------------------
We found the comment related to removal of voltage limiting components that was lodged during the SA ballot on Annex J by Mick Maytum (a surge protection expert,
unfortunately no longer with us).
See https://www.ieee802.org/3/cr/Comments/D3.0_Unsatisfied.pdf for
the full text of the comment and response.
The suggested remedy actually asked us to require removal of the components – the comment resolution group disagreed:
Add the following text
"Voltage limiters intended to prevent Ethernet port insulation breakdown shall be removed
for AC and DC voltage testing if their limiting voltage is less than the specified AC or DC
test voltages applied. For impulse testing, voltage limiters may be left in place to perform
their intended function. If removed for impulse testing, the voltage limiter shall pass the
impulse test when separately tested."
REJECT.
The CRG disagrees with the commenter. There was no consensus to change the text
based on the commenters suggested remedy.
George Zimmerman, Ph.D.
President & Principal
CME Consulting, Inc.
Experts in Advanced PHYsical Communications
310-920-3860
----------------------------------
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David D. Brandt Engineering Fellow |
Rockwell Automation
1201 South Second Street
Milwaukee, WI 53204-2496
P: 1.414.382.4309
ddbrandt@xxxxxxxxxxxxxxxxxxxxxx
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