Lightning arresters?

I've run across a couple of instances where long runs of cable from a
router to a remote AP (even with PoE, so there's no ground loop
problems) can damage the APs, so I'm looking for some CAT5 lightning
arresters that are compliant with PoE.

Does anyone have any experience with, or preferred vendors of such
things? I've got a _lot_ of Google hits that I'm looking over, but
real-life experiences and personal reccomendations (or warnings) are
much better than manufacturer's literature.

My all-time favorite gear for antenna feedlines has always been
PolyPhaser, but I'm not sure how their CAT5 gear is...

Thanks in advance for any hints!

William P.N. Smith <(E-Mail Removed)> wrote:
>I'm looking for some CAT5 lightning arresters that are compliant with PoE.

Oops, just realized I have to specify that I'm looking for lighting
arresters that are compliant with 802.3af PoE _SWITCHES_, as midspans
and switches put their power on different leads...

In article <(E-Mail Removed)>,
William P.N. Smith <(E-Mail Removed)> wrote:
>I've run across a couple of instances where long runs of cable from a
>router to a remote AP (even with PoE, so there's no ground loop
>problems) can damage the APs, so I'm looking for some CAT5 lightning
>arresters that are compliant with PoE.
>
>Does anyone have any experience with, or preferred vendors of such
>things? I've got a _lot_ of Google hits that I'm looking over, but
>real-life experiences and personal reccomendations (or warnings) are
>much better than manufacturer's literature.
>
>My all-time favorite gear for antenna feedlines has always been
>PolyPhaser, but I'm not sure how their CAT5 gear is...
>
>Thanks in advance for any hints!


CAT5 Ethernet devices are isolated at each end good for a few thousand
volts (4kV ?). ISTM that if you get a lightning hit close enough to
exceed that you're screwed in lots more ways than your APs.


--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. Proudly then, even more so in hindsight.

(E-Mail Removed) (Al Dykes) wrote:
>CAT5 Ethernet devices are isolated at each end good for a few thousand
>volts (4kV ?). ISTM that if you get a lightning hit close enough to
>exceed that you're screwed in lots more ways than your APs.

Well, http://geekho.com/IMG_0140.JPG probably could have been
prevented (poor picture, but it blew the cover open) with some
appropriate lighting arresters. The (protected) antenna on the top of
the tower had been removed for replacement when this happened...

I'm looking at http://www.polyphaser.com/datasheets/NX4-60.pdf for
now, but they are pretty pricey, anyone have any other thoughts?

Thanks!

"Al Dykes" <(E-Mail Removed)> wrote in message
news:e5dhhv$ijt$(E-Mail Removed)...
> CAT5 Ethernet devices are isolated at each end good for a few thousand
> volts (4kV ?). ISTM that if you get a lightning hit close enough to
> exceed that you're screwed in lots more ways than your APs.

But that's only really intended to protect against differential earth
problems not lightening. I don't think even the "old" fat ethernet that used
cable piercing taps would survive very close lightening strikes. I don't
think that was rated for use between buildings that could be on different
mains phases.

Perhaps you need to investigate solar power for the remote end so that you
can use fibre and media converters?

"CWatters" <(E-Mail Removed)> wrote:
>Perhaps you need to investigate solar power for the remote end so that you
>can use fibre and media converters?

The 'remote end' is the other side of the house, where the cables go
to the pole on the roof. Antennas, weather station sensors, WebCam,
wireless internet node, don't need converters, just need arresters.

2K or 4K volt isolation in network interface card (NIC) is internal
protection that can be overwhelmed IF protection is not installed where
wire enters a building. Telephone switching stations connected to
overhead wires everywhere in town work uninterrupted and undamaged
during every thunderstorm. Operating without damage is normal and
necessary when protection is properly installed.

Protection is not the protector. Yes Polyphaser protectors are
legendary. But that is not because Polyphaser protectors do something
mythical. Protectors don't stop or block damage as a 2K or 4K NIC
interface must if missing is ... well what does Polyphaser discuss
extensively? Earthing is the protection. Polyphaser protector is
superb because (when) it makes a short connection to a same earth
ground used by AC electric, phone line, cable TV, and ham radio
equipment.

If transients are properly earthed at a building entrance, then that
2K or 4K volt protection in network devices is not overwhelmed. But
again, does PoE ethernet have that common mode transient protection? I
have not seen the numbers.

PoE means protector must remain well above that voltage (42 volts?)
BellCore specs in that Polyphaser protector (because phone lines were
generations ago direct lightning strike protected) define a low voltage
protector. Galvanic isolation inside that PoE ethernet device should
be sufficient to make any transient below those BellCore specs to not
be destructive. However I don't know if a PoE spec for voltage
transient means a lower voltage earthed protector may be necessary.
Contact Polyphaser for their interpretation. Get specs (numbers) from
those PoE devices to learn of their internal protection numbers.
Whereas conventional ethernet has that 2K or 4K volt galvanic
isolation, I don't know if that also applies to power wires in PoE.

BTW, why long before WWII did we suffer direct lightning strikes
without damage - and not use fiber optics? Direct lightning strikes
without damage is routine if the human does his job in advance. I just
don't know what internal protection numbers are for the PoE wires;
whether those BellCore numbers are sufficient..

William P.N. Smith wrote:
> (E-Mail Removed) (Al Dykes) wrote:
>> CAT5 Ethernet devices are isolated at each end good for a few thousand
>> volts (4kV ?). ISTM that if you get a lightning hit close enough to
>> exceed that you're screwed in lots more ways than your APs.
>
> Well, http://geekho.com/IMG_0140.JPG probably could have been
> prevented (poor picture, but it blew the cover open) with some
> appropriate lighting arresters. The (protected) antenna on the top of
> the tower had been removed for replacement when this happened...
>
> I'm looking at http://www.polyphaser.com/datasheets/NX4-60.pdf for
> now, but they are pretty pricey, anyone have any other thoughts?
>
> Thanks!

"w_tom" <(E-Mail Removed)> wrote:
>Earthing is the protection. Polyphaser protector is
>superb because (when) it makes a short connection to a same earth
>ground used by AC electric, phone line, cable TV, and ham radio
>equipment.

Agreed! In this case, the wires from the roof come into one side of
the house (where there's a separate ground wire to a
lightning-arrester-only ground rod), and the computer gear is all
(lessee) about 100 feet of wire away. Not ideal, but we don't live in
an ideal world...

Fiber doesn't help because things like phone lines will also be on the
CAT5 cables, and those are more difficult and expensive to run over
fiber.

> PoE means protector must remain well above that voltage (42 volts?)

48V nominal, up to 52(?)V within spec. The switch/midspan thing just
means in my case that the data lines are only going to be clamped to
70(?) volts, not the 15(?) volts that they could use if the PoE
injectors were on dedicated "unused" pairs. I've found lots of
lightning arresters that only work on midspans, but only the
PolyPhasers that'll work with switches.

Notice what is protective voltages in BellCore specs. Don't worry
about 70 volts on a 52 volt wire. Cat5 interfaces should be good for at
least 100 volts. But again, I don't have specific numbers. That's
not 100 volts continuous which is why protectors can earth such
tremenous transients.

Protectors are not filters. A filter does not provide effecitve
protection. Protectors are 'shunts' to earth. Protectors are best
when (for example) 50 meters from electronics. That separation between
a protector and transistor means better protection. A protector is
nothing more than a temporary connecting device (ie a switch) to earth.
A earthng connection that should be less than 3 meters, which is why
wires drop down to earth before rising back up to enter a building. A
connection that is better when 100 feet from transistors - not adjacent
to electronics.

Every incoming utility wire must use a common earth ground. No way
around that requirement since earthing - not a protector - is
protection. If CAT5 wire is earthed to a different ground, then
multiple earth grounds increase damage possibility. No way around that
common earthing requirement. Numerous solutions to fix the 'imperfect'
world from an Ohio utility is their 'good' solution. A 'preferred'
solution also demonstrated:
http://www.cinergy.com/surge/ttip08.htm

How do telcos install protection? Ideally a protector is up to 50
meters distant from switching computer transistors and near 0 meters to
a big, common, earth ground. IOW potectors on midspans don't really
accomplish much because they don't have that earthing connection common
to all other utilities..

William P.N. Smith wrote:
> "w_tom" <(E-Mail Removed)> wrote:
> >Earthing is the protection. Polyphaser protector is
> >superb because (when) it makes a short connection to a same earth
> >ground used by AC electric, phone line, cable TV, and ham radio
> >equipment.
>
> Agreed! In this case, the wires from the roof come into one side of
> the house (where there's a separate ground wire to a
> lightning-arrester-only ground rod), and the computer gear is all
> (lessee) about 100 feet of wire away. Not ideal, but we don't live in
> an ideal world...
>
> Fiber doesn't help because things like phone lines will also be on the
> CAT5 cables, and those are more difficult and expensive to run over
> fiber.
>
> > PoE means protector must remain well above that voltage (42 volts?)
>
> 48V nominal, up to 52(?)V within spec. The switch/midspan thing just
> means in my case that the data lines are only going to be clamped to
> 70(?) volts, not the 15(?) volts that they could use if the PoE
> injectors were on dedicated "unused" pairs. I've found lots of
> lightning arresters that only work on midspans, but only the
> PolyPhasers that'll work with switches.

"w_tom" <(E-Mail Removed)> wrote:
> http://www.cinergy.com/surge/ttip08.htm

Ah, that makes a lot of sense, I'll have the electrician run another
heavy wire between the lightning ground rod and the main power panel
to bond them together.

Should this bond wire go to the main power panel, or to the ground rod
for the main power panel?

Thanks!