Often what appears to be strange or capricious events are
explained when hidden or overlooked electrical paths are
discovered.
To have damage, a complete circuit was exist through
electronics. Once a transient passes through everything in an
electrical path, only then does something in that path fail.
The transient does not just crash on the beach like an ocean
wave. First the transient passes through everything in a
circuit that starts at the cloud and ends up at earthborne
charges miles distant. The building simply becomes a part of
that long electrical circuit from cloud, through building,
into earth, and then over to those earthborne charges. To
suffer damage, a transistor must be between incoming and
outgoing paths.
Things often considered non-electrical conductors can become
electrical conductor during transients. EVen concrete is an
excellent conductor. If a stereo speaker cable contacts the
baseboard heat, that can become an outgoing and destructive
path through a stereo. Incoming on AC electric. Outgoing
through that stereo wire. Yes, wire insulation connects
stereo wire to baseboard heat.
A building is chock full of conductive paths; some that we
initially don't consider conductive. So many paths that some
people instead assume lightning is capricious.
Cited previously was a TV and VCR sharing same electrical
receptacle. TV was not damaged. VCR was. Contributing to
this damage was that the VCR provided a better outgoing path
to earth. VCR conducted a destructive transient to earth;
thereby acting as a very expensive surge protector to the TV.
To better appreciate why some things are damaged and other are
not, one must first learn of every conductive path inside the
building. Again, lightning is not so capricious once we
analyze damage at the electronic component level; learn of
'sneaky' external connections.
A radio station was constructed to eliminate many of those
conductive 'sneak' paths by making the building's floor
equipotential. The floor was made into one big single point
ground beneath equipment so that interior electronics remained
at a constant voltage. No voltage difference (therefore no
separate incoming and outgoing paths) means no destructive
transients:
http://scott-inc.com/html/ufer.htm
Equipotential being one way to eliminate transients through
appliances. But this author also provided his radio station
with best earthing - an Ufer ground. IOW he also made the
entire building into a most conductive earth ground. He
provided protection by two methods: using good conductivity
and making the building equipotential.
We can never make a connection to earth ground sufficient.
So we also make the building equipotential using a single
point earth ground technique. But a truly equipotential
building is not possible. So we make the connection to earth
the most conductive as possible - ie Ufer ground.
The best protection means installing an earthing system when
earth is first dug and footings are poured. If Ufer grounds
cannot be installed, another alternative is the halo ground -
a buried wire surrounding the building. However if neither is
feasible (because the plans were not done at the architects
level), we still bring all utilities into the building as a
same location AND provide utilities with good earthing. Even
one 10 foot earthing rod will be a major earthing
improvement. An electric utility demonstrates the principles
with their 'bad, ugly, and good' examples:
http://www.cinergy.com/surge/ttip08.htm
Another manufacturer demonstrates the principles in a
communication facility on Adobe page 14 at:
http://leminstruments.com/grounding_tutorial/html/index.shtml
Protection involves two basic objectives.
First is to earth a destructive transient before it can
enter the building using a most conductive earth ground.
Earth before a transient can find the so many 'sneak' paths
through appliances. This is accomplished with 'whole house'
protectors (AC electric and phone) or direct hardwire
connections (cable TV and satellite dish), made as short as
possible, to earth ground that is as large or conductive as is
reasonable.
Second is to make the voltage differences between appliances
or between an appliance's 'incoming verses outgoing' wires to
be equipotential. This is accomplished by making that earth
ground a single point ground, addressing the protection in
terms of a building wide and geological evaluation, and again,
bringing everything that could carry a transient into a
building at the common service entrance.
We learn from damage by finding paths into and out of the
electronics that found earth ground using circuits initially
not known to be electrical conductors.
Discover why damage occurs by first learning incoming and
outgoing electrical paths. A most common path that damages
computer modems is incoming on AC electric and outgoing to
earth ground via the telco installed 'whole house' protector.
Notice a transient did not come down the phone line, damage
the modem, then stop. Destructive transients don't crash on
the beach like ocean waves. First a transient establishes a
complete electrical path to earth ground. Then something
fails in that path. Often damaged is a PNP transistor that
drives the modem's off-hook relay. The complete path includes
a direct electrical connection from relay's coil to relay's
wiper. Another example of a path that we normally consider
non-conductive. From relay's data sheets, the breakdown
voltage between that coil and wiper defines another part of
the conductive electrical path.
Lightning seeks earth ground. To discover why some
transistors are damaged and others are not, first find
surprise (sneak) paths to earth ground. To avoid future
damage, modify the incoming path with non-destructive and more
conductive paths to earth (ie. use a well earthed 'whole
house' protector). Never think of transients as capricious.
Transistors are damaged for specific reasons. Learn from
'dead bodies' (the best evidence) why damage occurred; what
was the destructive earthing path. Two principles to superior
protection being a most conductive path to earth and making
the structure equipotential. Protection is not provided by
stopping, blocking, absorbing, or filtering destructive
transients. And yet that is what a plug-in (power strip or
UPS) protector manufacturer hopes you will assume.
Damage is about destructive paths to earth ground via
transistors. Protection has always been about earthing
transients.
