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High Voltage Interface (HVI) in Substations, Power Plants, and Cellular Towers Protect Against Lightning and Ground Potential Rise Damage
Service Interruptions are Guaranteed without an HVI on Wire-Line Communication Circuits

by Ernest M. Duckworth Jr., P.E., President-LPGI & Affiliates

 

-- 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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