Lightning strikes between 59 and 237
structures per 100 miles of electric power lines
each year, depending upon the geographical location
of the power lines.
The average lightning discharge through grounded
structures can exceed 50,000 amps and 100,000 to
500,000 volts in about 30 microseconds. This
discharge must be dissipated through a series of
Because of the immense energy that is discharged, a
number of individual ground connections must be
available in order to dissipate the energy to the
earth’s crust. Normally, the strike is discharged
through 10 to 20 individual structure grounds.
Our investigations show that properly installed
POLY-GROUND® backfill should maintain
both structural strength and electrical properties
under lightning conditions.
We theorize POLY-GROUND® has several
advantages. One advantage being that lightning
strikes create permanent electrical pathways through
the POLY-GROUND® backfill. With the
greater the intensity of the strike, the electrical
pathways that are created are multiplied. The more
electrical pathways created, the more electrically
conductive the POLY-GROUND® backfill
Another theory is that structural integrity is
maintained, although some scorching appears on the
foam-metal interface. Our investigation indicates
that the POLY-GROUND® should not burn
because of the limited oxygen present in the soil
and in the foam material, when at least ten (10)
structures are grounded. Most applications will have
more grounds connected (10+) together.
Also, the lower resistance of the backfill should
allow the energy to radiate the strike to the
interface of the POLY-GROUND® soil and
will reduce dramatically the high voltage shock. Our
conclusions are based on testing and theoretic
The test samples were four feet long, six inches in
diameter, filled with POLY-GROUND® with a
5/8 inch ground rod in the center of the POLY-GROUND®.
It is our conclusion from these tests that
POLY-GROUND® makes a far superior
backfill/ground for dealing with lightning strikes
and avoiding the damages they can cause to an
Corrosion is an electro-chemical
phenomenon where the metal tends to return to metal
oxide by oxidation where a conductive circuit
exists. POLY-GROUND® backfill material
used to install metal structures is a closed cell
polyurethane foam that isolates the metal structure
from the soil.
Our test procedure was done with a 3" foam cube that
had a steel bar embedded in the foam block. The foam
block with steel bar was immersed in a salt-water
electrolyte with a 10 volt DC connected to the steel
bar and the electrolyte.