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

[Geoff Thompson <gthompso@xxxxxxxxxxxxxxxxxx>]

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