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Re: [8023-POEP] Query of Protection for PoE



Hi all,

 

Regarding the protection of PSE and PD ports:

 

The current IEEE802.3/af is taking care of these issues as follows:

 

Environment A: All system segments are within the same building, Power source gnd is referenced to a single system gnd.

-          1500Vac rms isolation between MDI to chassis GND

-          Port toport isolation is not required

 

Environment B: Parts of the system segments are locating outside the building, system may be powered from different power sources with different GND.

 

-          1500Vac rms isolation between MDI to chassis GND

-          1500Vac rms isolation from port to port

 

 

Protection measures (circuits) against transient voltage, lightning etc are implementation specific and are out of scope of the IEEE802.3af.

 

Yair

 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Mukundan R
Sent: Monday, January 31, 2005 7:44 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Query of Protection for PoE

 

 

Thanks Geoff Thomson,

Waiting for the group to give its thoughts and action points..

Regards
Mukundan


Geoff Thompson wrote:

Mukundan-

Now that your question has been refined to be within what I believe is the scope of the group, I will turn it over to the group for consideration when we come to that part of the project.

To date I have not heard anything said about raising any of the minimum isolation requirements set forth in the current standard.

Best regards,

Geoff


At 03:20 PM 1/29/2005 +0530, Mukundan R wrote:

Hi Geoff Thomson,

Yes, EFM could be where this can lead to more problems. But in PoE, how are we going to protect the PoE PSE and PD ICs' from failure? Will the 1500V isolation and the fuse present enough to handle this?  the query i have raised can happen in indoor cabling also.

There will be people in this group who would have dealt with these issues earlier itself. And when we are trying to provide comments for the cabling addedum, i wanted to bring this dimension also..ie, for example do we think of a protection mechanism in the cabling itself? But that will not make the standard attractive.

Thanks and Regards
Mukundan


Geoff Thompson wrote:

Mukadan-

There was nothing wrong with your query. The scope has not yet been formally set for PoEplus. I would say (only my opinion) that the predominant sentiment is to confine the work to augmenting the power available via clause 33 (and changes appropriate to support that).

I believe what you are asking for is power for use in copper outside cabling. I believe that would be a separate project directed at the copper PHYS specified in IEEE Std 802.3ah, Ethernet in the First Mile.

I believe that it is unlikely that there will be a change in the 802.3 standard that will include the use of 10BASE-T/100BASE-TX/1000BASE-T in outdoor situations.

Again, just my opinion.

Best regards,

Geoff


At 09:57 AM 1/28/2005 +0530, Mukundan R wrote:

Geoff Thompson-

Thanks for the information provided.

Yes, i saw this clause in the standard and know its beyond the scope of the IEEE Std.

But, the reason i raised this query is to try get a systems approach to the PoE. Just by having a standard we cannot forward that, we need to use that standard to design products that the customer might require and install at totally different real world infrastructure.

And as the PoE is now trying to go for higher wattage, i wanted to check whether we are considering in this angle also.

It would be grateful if the correct forum / any archive discussing this issue earlier is pointed, so that i need not query at the wrong place.

Thanks and Regards
Mukundan

Geoff Thompson wrote:

Mukadan-

This is not considered to be within the application space.

9.7.2 Environment B requirements

The attachment of network segments, which cross environment A boundaries, requires electrical isolation of 1500 V rms, 1 min withstand, between each segment and all other attached segments and also the protective ground of the repeater unit.

If segments are of an electrically conductive medium, it is recommended that this isolation be provided by the use of external MAUs connected by AU Interfaces. If internal MAUs are used for attachment to conductive media segments, then the segments shall be installed such that it is not possible for an equipment user to touch the trunk cable screen or signal conductor. A repeater of this variety requires professional installation.

The requirements for interconnected electrically conducting LAN segments that are partially or fully external to a single building environment may require additional protection against lightning strike hazards. Such requirements are beyond the scope of this standard.

It is recommended that the above situation be handled by the use of a nonelectrically conducting LAN segment (see 9.9 or Clause 15).



See also 27.5.3.2
See also 41.4.3.2

Best regards,

Geoff Thompson

At 09:29 PM 1/27/2005 +0530, Mukundan R wrote:

Hi,

This is Mukundan from madras, India.

We are implementing PoE in our Metro Ethernet Switches.

Thanks for this mail on the telecom cabling standard for DC power requirements! We are checking on what is the protection /safety procedure to be implemented for PoE protection in the designs. ie, when we say PoE, the concept is to power remote products / appliances and this cabling could be across buildings / intra building.

IEEE 802.3af as such does not indicate on the GR / ITU-T standards like GR1089 / K.21 / K.20 power crossing requirements. Indoor cabling has more issues with power crossing than lightning whereas outdoor ethernet cabling is prone to lightning.

The PoEplus is striving for nearly 40watts of power, which exaggrates the requirement for a secure cabling infrastructure especially burn proof in case of short circuiting - an extreme state of power crossing.

The Query: Whether the meeting proposed on the cabling structure can take in this                                dimension of query ?
                                                        or
                   Whether the interims session meeting will be the appropriate forum?

Thanks and Regards
Mukundan

Michael McCormack wrote:


I apologize for the late notice; however, I am giving as much as I have received . . .

There will be a meeting this evening to determine if a response is warranted from the 802.3 to the TIA regarding their latest draft of " P-4425-AD6-D (TIA/EIA-568-B.1-6) 'Commercial Building Telecommunications Cabling Standard Part 1: General Requirements. Addendum 6: Additional Cabling Requirements for DC Power'  " and if a response is warranted, then what the response should be.  This response needs to be drafted from the viewpoint of the existing 802.3 standard.  The meeting will take place in the Windsor Room of the Hyatt Hotel this evening at 6:00 PM Vancouver time.

All interested parties are invited to attend; however, I would like to extend a special invitation to anyone who has worked on the current specification (i.e. worked on 802.3af) and / or has crafted previous responses to previous revisions of the TIA document to please make every effort to attend this meeting.

Mike

P