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High
Voltage Interface (HVI) in Substations, Power Plants, and
Cellular Towers Protect Against Lightning and Ground Potential
Rise Damage
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Interruptions are Guaranteed without an HVI on Wire-Line
Communication Circuits |
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by Ernest M. Duckworth
Jr., P.E., President-LPGI & Affiliates
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-- HIGH VOLTAGE
INTERFACE (HVI)
WHY? To protect both power and telephone company (1) personnel,
(2) equipment and (3) plant from the exposure of a remote ground
due to a Ground Potential Rise (GPR). May also be used to
protect anyone from the exposure of a remote ground due to a GPR
from a power line fault or a lightning strike. A absolute
necessity to insure power company protective relaying to
minimize the chances of a major power blackout, and an absolute
necessity to insure continued wireless telephone service from
lightning strikes.
WHEN? When the GPR is capable of exceeding 1000V
peak-asymmetrical an HVI must be used in-place of standard gas
tube or solid state protection on communications pairs. The
failure to use an HVI will result in equipment and cable damage,
and represents a significant safety risk to personnel. An HVI
must be used when there is any requirement for circuit
reliability associated with the circuits that are connected to
remote ground.
WHERE? An HVI is required
at every high voltage location where there are circuits
connected to a remote ground. A remote ground may be another
high voltage location. An HVI should be placed on the ground
grid and sheltered from the elements in a building.
HOW? This is a very good question! There are many basic rules
and some information on the subject. The best way to learn how
is to take a training seminar from LPGI & Affiliates. Also,
a copy of IEEE Std. #487-2000 will be very helpful as will a
visit to this web-site and www.gpr-expert.com
Visualize the HVI as having a face (front-side) and a rear
(back-side). The face is the high voltage side and isolates
circuits from a remote ground. The rear is the low voltage or
station side in which circuits do not leave the grid and are
bonded to grid ground. Do not forget that PVC conduit is
required for your cable entrance and steel conduit is
recommended for the cables on the station. Also remember to
protect the station side of your HVI from lightning surges and
switching transients using solid state (five pin) cable pair
protection.
Beware of the dangers of doing nothing! Gas tube or solid state
pair protection are not an HVI and do not meet the requirements
of IEEE Std. 487-2000. The use of an HVI is a recognized
necessity both nationally and internationally. Major power
blackouts can be traced to a failure of communications during
protective relaying.
LPGI & Affiliates
962 Coronado Drive
Sedalia, CO 80135
303-688-5800
Fax: 303-688-5551
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