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This reflector has been very quiet, so maybe I can stir up some controversy?
A) We are allowing "Env A" PSE's in 802.3af
B) These "Env A" PSE's could have many ports which share the same large DC power source
therefore there could be many meters of cable that are all hooked together at DC.
Example: 200 ports, 100 meters each is 20 km, 656,000 ft, or 12.4 miles.
So, 20 km of cable that is all hooked together at DC, and each PSE port is delivering DTE power
Now, I plug in one more UTP cable and PD into this PSE system.
I'm thinking that there could be a very large transient as the new port turns on due to all the static
charge that could be on all those 20 km of cables.
Now, in reality, there is probably enough leakage to ground to bleed off the charge, but
can we be sure of this?
Proposals:
1) make DTE power be tied to ground in the same way as telecom (48V) power is, and as most power
distribution systems in the world are. The connection to ground could only be at one point, of course.
This would require changing or at least interpreting the existing 802.3 spec.
2) Have each PSE port contain some leakage path, maybe around 10 Meg ohm,
it must be greater that 2 Meg which is the 802.3 spec.
3) Make this concern that of the large PSE producer only and not of the 802.3af
Does anyone out there share these concerns? Any other ideas?
- Rick