# Terms and definitions

structure to be protected: structure for which protection is required against the effects of lightning in accordance with this standard

NOTE A structure to be protected may be a part of a larger structure.

structures with risk of explosion: structures containing solid explosives materials or hazardous zones as determined in accordance with IEC 60079-10 and IEC 61241-10

NOTE For the purposes of this standard, only structures with hazardous zones type 0 or containing solid explosive materials are considered.

structures dangerous to the environment: structures which may cause biological, chemical and radioactive emission as a consequence of lightning (such as chemical, petrochemical, nuclear plants, etc).

urban environment: area with a high density of buildings or densely populated communities with tall buildings

NOTE ’Town centre’ is an example of an urban environment.

suburban environment: area with a medium density of buildings

NOTE ’Town outskirts’ is an example of a suburban environment.

rural environment: area with a low density of buildings.

NOTE ’Countryside’ is an example of a rural environment.

rated impulse withstand voltage level (U w): impulse withstand voltage assigned by the manufacturer to the equipment or to a part of it, characterizing the specified withstand capability of its insulation against overvoltages

NOTE For the purposes of this standard, only withstand voltage between live conductors and earth is considered.

electrical system: system incorporating low voltage power supply components

electronic system: system incorporating sensitive electronic components such as communication equipment, computer, control and instrumentation systems, radio systems, power electronic installations

internal systems: electrical and electronic systems within a structure

service: power line or telecommunication line connected to the structure to be protected

telecommunication lines: transmission medium intended for communication between equipment that may be located in separate structures, such as phone line and data line

power lines: transmission lines feeding electrical energy into a structure to power electrical and electronic equipment located there, such as low voltage (LV) or high voltage (HV) electric mains

dangerous event: lightning flash to the structure to be protected or near the structure to be protected

lightning flash to a structure: lightning flash striking a structure to be protected

lightning flash near a structure: lightning flash striking close enough to a structure to be protected that it may cause dangerous overvoltages

number of dangerous events due to flashes to a structure (N D): expected average annual number of dangerous events due to lightning flashes to a structure

number of dangerous events due to flashes to a service (N L): expected average annual number of dangerous events due to lightning flashes to a service

number of dangerous events due to flashes near a structure (N M): expected average annual number of dangerous events due to lightning flashes near a structure

number of dangerous events due to flashes near a service (N I): expected average annual number of dangerous events due to lightning flashes near a service

lightning electromagnetic impulse (LEMP): electromagnetic effects of lightning current

NOTE It includes conducted surges as well as radiated impulse electromagnetic field effects.

surge: transient wave appearing as overvoltage and/or overcurrents caused by LEMP

NOTE Surges caused by LEMP can arise from (partial) lightning currents, from induction effects into installation loops and as remaining threats downstream of SPD.

node: point on a service line at a which surge propagation can be assumed to be neglected

NOTE Examples of nodes are a point on a power line branch distribution at a HV/LV transformer, a multiplexer on a telecommunication line or SPD installed along the line conforming to IEC 62305-5.

physical damage: damage to a structure (or to its contents) or to a service due to mechanical, thermal, chemical or explosive effects of lightning.

injury to living beings: injuries, including loss of life, to people or to animals due to touch and step voltages caused by lightning

failure of electrical and electronic systems: permanent damage of electrical and electronic systems due to LEMP

probability of damage (P X): probability that a dangerous event will cause damage to or in the structure to be protected

Loss (L X): mean amount of loss (humans and goods) consequent to a specified type of damage due to a dangerous event, relative to the value (humans and goods) of the structure to be protected

Risk (R): value of probable average annual loss (humans and goods) due to lightning, relative to the value (humans and goods) of the structure to be protected

risk component (R X): partial risk depending on the source and the type of damage

tolerable risk (R T): maximum value of the risk which can be tolerated for the structure to be protected

zone of a structure (Z S): part of a structure with homogeneous characteristics where only one set of parameters is involved in assessment of a risk component

section of a service (S S): part of a service with homogeneous characteristics where only one set of parameters is involved in the assessment of a risk component

lightning protection zone (LPZ): zone where the lightning electromagnetic environment is defined

NOTE The zone boundaries of an LPZ are not necessarily physical boundaries (e.g. walls, floor and ceiling).

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

NOTE Lightning protection level is used to design protection measures according to the relevant set of lightning current parameters.

protection measures: measures to be adopted in the structure to be protected, in order to reduce the risk

lightning protection system (LPS): complete system used to reduce physical damage due to lightning flashes to a structure

NOTE It consists of both external and internal lightning protection systems.

LEMP protection measures system (LPMS): complete system of protection measures for internal systems against LEMP

magnetic shield: closed, metallic, grid-like or continuous screen enveloping the structure to be protected, or part of it, used to reduce failures of electrical and electronic systems

surge protective device (SPD): device intended to limit transient overvoltages and divert surge currents. It contains at least one non-linear component

coordinated SPD protection: set of SPDs properly selected, coordinated and installed to reduce failures of electrical and electronic systems