On 9/4/19 10:35 AM, David Gilbert wrote:
The fine print on every whole house surge protector I've been able to
find specifically excludes lightning for coverage. The coverage
specifies only power line surges. Are you aware of one that includes
lightning?
I think that the value of the whole house protector is in reducing the
amplitude of spikes that are *induced* by a nearby lightning strike, as
opposed to dealing with the *direct* effect of a strike.
For instance, lightning current flowing in your tower or ground system
inducing a voltage in power wiring in your wall that is parallel to the
tower, even with no physical connection.
There's a lot of ways to kill equipment with fairly small, but fast
transients. Tesla coils are notorious for this, since the "sparks" are
about 5-6 feet long, discharging a 20-50 pF capacitor really fast (2
microhenry inductance from the spark), so you get this nice high di/dt
which induces differential voltages in the loops formed by the 3rd wire
grounding of appliances and the like.
A lightning strike can do the same thing - the main stroke causes
induced voltages in near by objects, which then breaks down as a
separate discharge, with really high di/dt (higher than the lightning
stroke itself, because the inductance in the circuit is lower than in
the lightning stroke)
Dave AB7E
On 9/4/2019 8:44 AM, john@kk9a.com wrote:
GL rebuilding Keith.
A tower lightning strike will cause an induced voltage spike in a
home's electrical system, even if nothing is connected to the tower. I
have had this occur while building a new tower and the control cables
and coax were not yet connected or even touching the tower. Simply
disconnecting the coax which many hams do is ineffective lightning
protection. There is a lot of valuable protection information on this
list. Assuming that you have a bunch of ground rods and a SPG, I would
suggest a good whole house surge protector.
John KK9A
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