w_tom wrote:
On Aug 13, 5:31 pm, (Al Dykes) wrote:
In large buildings where all the utility wire is below-ground, it
might be nothing. In surburbia with above-ground power, I'd put a
whole-house protector in the panel and a "better" powerstrip under
each PC.
The best information on surges and surge protection I have seen is at:
http://omegaps.com/Lightning%20Guide...ion_May051.pdf
- "How to protect your house and its contents from lightning: IEEE guide
for surge protection of equipment connected to AC power and
communication circuits" published by the IEEE in 2005 (the IEEE is the
dominant organization of electrical and electronic engineers in the US).
And also:
http://www.nist.gov/public_affairs/p.../surgesfnl.pdf
- "NIST recommended practice guide: Surges Happen!: how to protect the
appliances in your home" published by the US National Institute of
Standards and Technology in 2001
The IEEE guide is aimed at those with some technical background. The
NIST guide is aimed at the unwashed masses. Both are aimed at home use,
but contain useful information for all locations. They are also aimed at
surges, but contain some information on voltage loss.
No protector stops or absorbs destructive surges.
I wouldn’t bet on the inductor in a plug-in suppressor being effective.
But there are devices, like ferroresonant transformers that the IEEE
Emerald book says are effective at stopping surges.
Why do some protectors fail during a surge - as the indicator light
reports? Those protectors are grossly undersized. Grossly
undersizing gets the naive to recommend more ineffective protectors.
The effective 'whole house' protector is sufficiently sized
In w_’s mind, plug-in suppressors have miniscule ratings, service
panel suppressors have mega ratings. But plug-in suppressors are readily
available with very high ratings for relatively low cost. It is probably
harder to find UPSs with very high surge ratings. Any surge suppressor
in the US should be listed under UL 1449.
Each structure has its own single
point earth ground. Underground wire to the building also carries
surges:
http://www.erico.com/public/library/...es/tncr002.pdf
w_ has a fetish about tower antennas.
“Single point ground” is of major importance - entrance protectors for
phone, cable, ... connect with a *short* wire to the earth electrode
conductor at the power panel. With a large surge, the building ‘ground’
will always rise above `absolute' ground. The goal is for the power and
phone 'grounds' to rise together. Results of not having a single point
ground are illustrated in the IEEE guide pdf page 40.
Francois Martzloff, the NIST guru on surges, has written "the impedance
of the grounding system to `true earth' is far less important than the
integrity of the bonding of the various parts of the grounding system."
Meanwhile, plug-in protector does not even have an earthing
connection. Therefore its manufacturer avoids discussing earthing.
The IEEE guide explains plug-in suppressors work by CLAMPING the voltage
on all wires (signal and power) to the common ground at the suppressor.
Plug-in suppressors do not work primarily by earthing (or stopping or
absorbing) . The guide explains earthing occurs elsewhere. (Read the
guide starting pdf page 40). UPSs may or may not have the same surge
suppression.
Note that all interconnected equipment needs to be connected to the same
plug-in suppressor, or interconnecting wires need to go through the
suppressor. External connections, like phone, also need to go through
the suppressor. Connecting all wiring through the suppressor prevents
damaging voltages between power and signal wires (including induced from
nearby strikes). These multiport suppressors are described in both guides.
According to NIST guide, US insurance information indicates equipment
most frequently damaged by lightning is
computers with a modem connection
TVs, VCRs and similar equipment (presumably with cable TV
connections).
All can be damaged by high voltages between power and signal wires.
--
bud--