| The
Nature of the Threat
The nature of the threat to the
communciations equipment consists of overvoltage, overcurrent, or both.
The overvoltage element can destroy the semiconductors in the PBX, KSU
or CPU; while overcurrent can generate enough heat to cause a building
wiring fire.
Lightning is a major cause of overvoltage.
The map below is an isokeraunic map. The isokeraunic lines represent
areas of equal mean numbers of thunderstorms per year. The southeastern
US, as shown in the map, has a tremendous number of storms which produce
lightning. Remember, even if you are in a low density area, it takes
only one lightning strike to cause thousands of dollars in damage to
your communications systems.
Other threats to communications must be
considered equally important.
Lightning
This is the most common cause of voltage
surges which can damage a communications system. The building does not
have to take a direct hit for lightning to damage a system. A lightning
strike within a few miles can induce a surge which can travel along
aerial or buried cables into the equipment. |
Power
Line Crosses
The telecommunications line comes in
contact with an electric power line creating excess current on the
communications line. This can be caused by an electrician accidentally
crossing a power line with a telephone line or a downed electric and
telephone line crossing.
Conductive Spikes
Voltage surges created with the
accidental momentary contact of a telephone line with a power line.
Inductive Spikes
Power surges may be caused when high
power equipment is turned on or off generating an inductive kickback.
These spikes are easily induced into communications cables via
longitudinal coupling.
Electrostatic Discharge
Voltage surge of electrostatic energy
discharged into the communcation lines. The problem is usually found in
dry climates, but also may be caused by the electrical field that
surrounds a high voltage power facility. |
