ABC Book

Find here definitions of specific technical and scientific terms and acronyms.

All | A B C D E F H I K L M N O P Q R S T U V W
There are currently 67 results in this directory
Air terminals
Metallic components dedicated to the be the privileged point of impact of a lightning discharge (lightning rods, Early Streamer Emission air terminal, taut wires..).
Ball lightning
Ball lightning usually looks like a luminous spheric phenomenon, yellowish color, with a 15 to 20cm diameter (La foudre – Claude Gary – Ed. Dunod).
Electrically charged particles (positive or negative).
Mass of water or solid particles in suspension in the air.
Corona Effect
Natural phenomena due to the intensification of the electrical field causing the over-ionization of all surrounding elevated points (rods, antennae, trees, mountain crests…).
Very large clouds reaching several kilometers height and containing thousands of tons of water in suspension. Cumulonimbus are the typical lightning cells structures.
Current impulse (/imp)
Peak value (/peak) defined by charge Q and specific energy W/R (NF C 17 102 : 2011).
Dangerous sparking
Electrical discharge due to lightning which causes physical damage inside the structure to be protected (NF C 17 102 : 2011).
Impulse electrical current from earth to cloud (ascending) or cloud to earth (descending).
Part of the Lightning Protection System intended to conduct the lightning current from ESEAT to the earth termination system (NF C 17 102 : 2011).
Early Streamer Emission (ESE) lightning rod
Air terminal generating a streamer earlier than a simple rod air terminal when compared in the same conditions (NF C 17 102 : 2011).
Early Streamer Emission Air Terminal ESEAT efficiency (ΔT)
Difference expressed in micro-seconds between the emission time of an ESEAT and an SRAT measured in a laboratory under the conditions defined in this standard (NF C 17 102 : 2011).
Early Streamer Lightning Protection System
System made of one or several Early Streamer Emission rods, conductors and earth terminations to conduct safely the lightning discharge current to the ground and protect the structure, building or open areas against direct lightning hazards.
Earth termination system
Part of an external Lightning Protection System which is intended to conduct and disperse lightning current into the earth.
Electrical / Telecommunication lines
Transmission medium intended for communication / power supply between equipment that may be located in separate structures.
Electrical Field
A field of force surrounding a charged particle within which another charged particle experiences a force.
Find out more on
Electro-geometric Model (EGM)
Theoretical representation model of the upward streamer development, based on Electrical Field E, height of the lightning rod and intensity of the lightning discharge parameters.
Electromagnetic radiations
Waves of energy traveling around the a lightning discharge and causing overvoltage phenomenon on the neighboring electrical / telecom lines.
Equipotential bonding
Bonding to the ESESystem of separated conductive parts (see 5.5) of an installation, by direct connections or via surge protective devices, to reduce potential differences caused by lightning current. (NF C 17 102 : 2011).
Equipotential bonding main bar
A bar used to connect the natural components, ground conductors, earth conductors, screens, shields and conductors protecting telecommunication cables or other ones, to the lightning protection system. (NF C 17 102 : 2011).
Faraday or Meshed Cage
Network of metallic conductors fixed regularly (every 5 to 20 meters) on the structure to protect it against direct lightning discharges.
Frequency of dangerous events due to flashes to a structure
Expected average annual number of dangerous events due to lightning flashes to a structure (NF C 17 102 : 2011).
Fulgurite (lightning stones)
Also called « lightning stones, there are due to sand particles fuse together under very high temperature (more than 3000C°) when a lightning strikes the ground.
High Voltage Lab
Specific labs able to reproduce a discharge in the air along several meters. The Early Streamer Emission lightning rods efficiency is assessed in such laboratories in comparison to a Single Rod performances.
Amount of water in the atmosphere. Thunderstorms come usually with very heavy rain and hail.
Interconnected reinforcing steel
Steelwork within a concrete structure which is considered to provide an electrically continuity. (NF C 17 102 : 2011).
Formation of ions during a thunderstorm as a result of electrical discharge, particle collisions, or radiation.
Keraunic Level
Number of days per year the thunder has been heard.
Benjamin Franklin demonstated the electrical nature of the lightning phenomenon in 1792 thanks to his famous kite experience.
Very vibrant flash created by an electrical discharge, intra-clouds, inter-clouds or Cloud to Ground, during a thunderstorm.
Lightning electromagnetic impulse (LEMP)
Electromagnetic effects of lightning current (NF C 17 102 : 2011).
Lightning Flash
Atmospheric originated electrical discharge between cloud and earth consisting of one or more arcs (NF C 17 102 : 2011).
Lightning ground flash density (Ng)
Is the number of lightning flashes per km2 per year. This value is available from ground flash location networks (NF C 17 102 : 2011).
Lightning protection level (LPL)
Number related to a set of lightning current parameter values relevant to the probability that the associated maximum and minimum design values will not be exceeded in naturally occurring lightning (NF C 17 102 : 2011).
Lightning rod
System design and fix on a structure to protect it against direct lightning discharge.
Study of the processes in the Earth's atmosphere that cause particular weather conditions, especially in order to predict the weather.
Find out more on
Natural component
Conductive element located outside the structure, sunk in the walls or located inside a structure and which may be used to supplement the ESESystem down conductors. (NF C 17 102 : 2011).
Voltage exceeding the maximum operating voltage of an equipment. Transient overvoltages have four main causes :
- Lightning
- Industrial and switching surges
- Electrostatic discharges (ESD)
- Nuclear electromagnetic pulses (NEMP).
Physical damage
Damage to a structure (or to its content) or to a service due to mechanical, thermal, chemical or explosive effects of lightning. (NF C 17 102 : 2011).
Protected area
Zone protected by a lightning protection system. (NF C 17 102 : 2011).
Protection Radius
Value in meters to assess the protected area around a lightning rod. This value calculation is based on the “angle method”, the Electro-Geometric Model or the Rolling Sphere Theory.
French certification delivered since 2004 to certified lightning protection system manufacturers, consultants, maintenance and inspection organizations.
Rayonnement électromagnétique
Transport d’énergie sous forme d’ondes générées par les décharges, induisant des surtensions dans les tronçons de lignes électriques / communication à proximité.
Resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (I), (R = U/I, Ohm’s Law).
Return stroke
Electrical discharges flowing into the ionized lightning channel.
Value of probable average annual loss (humans and goods) due to lightning, relative to the total value (humans and goods) of the object to be protected (NF C 17 102 : 2011).
Rolling Sphere
Calculation method to assess the impact point of the lightning discharge, being the points in contact with the fictitious sphere surrounding the lower extremity of downward leader.
Saint Elmo Fire
Natural corona effect phenomenon on the top of the ship masts, named Saint Elmo fires by the XVth and XVth centuries sailors.
Separation distance
Distance between two conductive parts at which no dangerous sparking can occur. (NF C 17 102 : 2011).
Shock generator
Generator delivering very high intensity electrical shocks with a specific intensity and waveform. These generators are required to test Early Streamer Emission Lightning Rods (100kA minimum with 10/350µs waveform).
Single Rod
Traditional lightning protection system, made of metallic rods (usually copper) of different heights : from several meters high for Single Rods to 30 – 50cm for Meshed Cage rods.
Early Streamer Emission air terminals are tested and installed according to standrds (French NF C 17 102, Spanish UNE 21 186, Portuguese NP4426 etc…).
Step Voltage
The flow of lightning in the ground causes earth potential increases that vary according to the current intensity and the local earth impedance. It generate a voltage between two points on the ground (two earth pits or two feet for a person).
First phase of a lightning discharge, it’s a pre-discharge that progress upward from the Ground to the downward leader.
Striking point
Point where a lightning stroke contacts the earth, a structure or a lightning protection system. (NF C 17 102 : 2011).
Structures with risk of explosion
Structures containing solid explosive materials or hazardous zones (NF C 17 102 : 2011).
Transient wave appearing as overvoltage and/or overcurrents caused by the electromagnetic effects of lightning discharges (NF C 17 102 : 2011).
Surge protective device (SPD)
Device intended to limit transient overvoltages and drain away surge currents. It contains at least one non-linear component.
Taut Wires
Overhead wires air terminal system (for example the protective wire above the overhead High Voltage power distribution lines).
Test joint
Joint designed and placed to facilitate electrical testing and measurement of Early Streamer Emission lightning protection system components. (NF C 17 102 : 2011).
Loud noise caused by lightning discharges, due to the air violent dilatation when the current flows into the lightning channel.
Storm caused by strong rising air currents and characterized by thunder and lightning and usually heavy rain or hail. There are two type of thunderstorms: convective type (local high temperature variation and humidity) and frontal type (massive temperature and humidity cells meeting).
The initial corona effect converts into an upward streamer due to the intensification of the electrical field.
Voltage symbol (measured in Volt).
MOV (Multi Oxyde Varistors) is the mainstream surge protection devices technology.
Ventricular fibrillation
The most common cause of lightning death due to a total desynchronization of the myocardial muscles.
Form in which things such as sound, light, and radio signals travel.
Discover more

Find more on the lightning phenomenon