Lightning Protection, Grounding,
& Surge Suppression Glossary of Terms

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Capacitance
The capacity of an electric nonconductor that permits the storage of energy when opposite surfaces are maintained at a difference of potential. Measured at 1.0 Hz unless other wise stated.
Capacitor
A device that can store an electrical charge.
Charge Separation
Generally, positive ions (water/ice molecules that have lost their electrons) are moved to the tops of clouds by the strong wind currents in the storm. Meanwhile, electrons gather on heavier ice particles that fall to the bottom of the clouds. This causes the charge separation: the tops of the clouds are positive, while the bottom is negative.
Chimney
A smoke or vent stack not meeting the requirements of a heavy-duty stack.
Circuit
An electronic closed-loop path between two or more points used for signal transfer.
Circuit Breaker
An automatic protective device that will allow current to flow under normal conditions, but will open the circuit under abnormal conditions to prevent damage from excessive current.
Circular Mil
A unit of area equal to the area of a circle whose diameter is one mil (1 mil = 0.001 inch).
Clamping Device
A component whose action is triggered by a pre-determined voltage. A clamping device will activate (turn on) and deactivate (turn off) at specific predetermined voltages.
Clamping Voltage
The voltage that appears across surge suppressor terminals when the suppressor is conducting transient current.
Classification Of Buildings
a) Ordinary Buildings - A building of common or conventional construction used for ordinary purposes, whether commercial, farm, industrial, institutional, or residential.

b) Class I Ordinary Building - A building that is not more than 75 feet (22.9 m)

c) Class II Ordinary Building - A building that is more than 75 feet (22.9 m) high or greater.

d) Metal-Clad Building - A building with either sides or roof made of or covered with sheet metal.

e) Metal-Framed Building - A building with electrically continuous framing of sufficient size and conductivity to be used as part of the lightning protection system.
Cloud-to-Cloud Lightning
Lightning discharges may occur between areas of cloud having different potentials without contacting the ground. These are most common between the anvil and lower reaches of a given thunderstorm. This lightning can sometimes be observed at great distances at night.
Cloud-to-Ground Lightning
A lightning discharge between a cumulonimbus cloud and the earth initiated by the downward-moving leader stroke. This is the second most common type of lightning, and poses the greatest threat to life and property of all known types.
Commercial Power
Power furnished by an electric power utility company.
Common-Mode Noise (longitudinal)
The noise voltage that appears equally, and in phase, from each current-carrying conductor to ground.
Concrete-Encased Ground Electrode
Also know as a Ufer ground. A grounding electrode completely encased within concrete, located within, and near the bottom of, a concrete foundation or footing or pad, that is in direct contact with the earth.
Conductor
The portion of a lightning protection system intended to transfer lightning discharge currents between strike termination devices and ground or to provide potential equalization between conductive bodies in/on the structure.

a) Main Conductor - A conductor intended to conduct primary lightning currents that interconnects strike termination devices with grounding electrodes.

b) Secondary Conductor - A conductor that connects metal bodies within the zone of protection to the lightning protection system to eliminate electrical potential that may create arcing.
Conductor Combination
The various conductors that are joined by a connection.
Conductor Shielding
An envelope that encloses the conductor of a cable and provides an equipotential surface in contact with the cable insulation.
Connection
A metallic device of suitable electric conductance and mechanical strength used to join conductors.
Connection Thermal Capacity
The ability of a connection to withstand the amount of current required to produce a specified temperature on the control conductor without increasing the resistance of the connection beyond that specified in this standard.
Control Conductor
The conductor that is utilized to measure equivalent changes in temperature, size, etc., that are occurring in at least one of the conductors joined by the connection under test.
Copper Clad Steel
Steel with a coating of copper bonded on it.
Corona
A faint glow enveloping the high-field electrode in a corona discharge, often accompanied by streamers directed toward the low-field electrode.
Coulomb
Named after Charles-Augustin de Coulomb, Coulomb is Current times Time. A measurement of charge in amp-seconds.
Counterpoise
A conductor or system of conductors located on, above or most frequently below the surface of the earth.
Coupling
The association of two or more circuits or systems in such a way that power or signal information may be transferred from one to another.
Coupling Capacitance
The association of two or more circuits with one another by means of capacitance mutual to the circuits.
Crest Factor (of A Periodic Function)
The ration of the peak value of a periodic function (ypeak) to the root-mean-square (rms) value (yrms); cf=ypeak/yrms.
Critical Load
Devices and equipment whose failure to operate satisfactorily jeopardizes the health or safety of personnel, and/or results in loss of function, financial loss, or damage to property deemed critical by the user.
Crowbar
Crowbar is a method of shorting a surge current to ground in surge protection devices. This method provides protection against more massive surges than other types, but lowers the clamping voltage below the operational voltage of the electronic equipment causing noise and operational problems. It also permits a follow current which can cause damage.
Cumulonimbus
Cumulonimbus clouds are also called thunderstorm clouds. They are frequently accompanied by heavy showers, lightning, thunder, and sometimes hail, tornadoes or strong, gusty winds. This cumulus cloud is vertical and often appears with an anvil-shaped cloud on top. A thunderstorm occurs from a cumulonimbus cloud.
Current
The flow of electrons through a conductor. Current is measured in amperes.
Current Loop Cycle
The combination of conductors and connections that carries the current of the circuit under test.
Customer Premises Equipment (CPE)
Any equipment connected by customer premises wiring to the customer side of the demarcation point (network interface). (ANSI T1.318)