A Guide to BS EN 62305:2006 Protection Against Lightning Part 10 ppsx

Glossary

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Lightning Protection Level (LPL)

Number related to a set of lightning current

parameters values relevant to the probability that the

associated maximum and minimum design values will

not be exceeded in naturally occurring lightning.

Lightning protection level is used to design protection

measures according to the relevant set of lightning

current parameters.

Lightning Protection System (Lightning

Protection System)

Complete system used to reduce physical damage due

to lightning flashes striking a structure. It consists of

both external and internal lightning protection

systems.

Lightning Protection Zone (LPZ)

Zone where the lightning electromagnetic

environment is defined. The zone boundaries of an

LPZ are not necessarily physical boundaries (eg walls,

floor and ceiling).

Lightning protective cable

Special cable with increased dielectric strength, whose

metallic sheath is in continuous contact with the soil

either directly or by the use of conducting plastic

covering.

Lightning protective cable duct

Cable duct of low resistivity in contact with the soil

(for example, concrete with interconnected structural

steel reinforcements or a metallic duct).

Lightning stroke

Single electrical discharge in a lightning flash to earth.

Long stroke

Part of the lightning flash which corresponds to a

continuing current. The duration time Tlong (time from

the 10% value on the front to the 10% value on the

tail) of this continuing current is typically more than

2ms and less than 1 second.

Long stroke charge (Qlong)

Time integral of the lightning current in a long stroke.

Loss (Lx)

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

object to be protected.

Metal installations

Extended metal items in the structure to be protected,

which may form a path for lightning current, such as

pipework, staircases, elevator guide rails, ventilation,

heating and air conditioning ducts, and

interconnected reinforcing steel.

Multiple strokes

Lightning flash consisting on average of 3 - 4 strokes,

with typical time interval between them of about

50ms (events having up to a few tens of strokes with

intervals between them ranging from 10ms to 250ms

have been reported).

“Natural” component of LPS

Conductive component installed not specifically for

lightning protection which can be used in addition to

the Lightning Protection System (LPS) or in some cases

could provide the function of one or more parts of the

Lightning Protection System (LPS).

Examples of the use of this term include:

– “natural” air termination;

– “natural” down conductor;

– “natural” earthing electrode.

Node

Point on a service line at which surge propagation can

be assumed to be neglected. Examples of nodes are a

point on a power line branch distribution at a HV/LV

transformer, a multiplexer on a telecommunication

line or Surge Protective Device (SPD) installed along

the line.

Number of dangerous events due to flashes near

a service (NI)

Expected average annual number of dangerous events

due to lightning flashes near a service.

Number of dangerous events due to flashes near

a structure (NM)

Expected average annual number of dangerous events

due to lightning flashes near a structure.

Number of dangerous events due to flashes to a

service (NL)

Expected average annual number of dangerous events

due to lightning flashes to a service.

Number of dangerous events due to flashes to a

structure (ND)

Expected average annual number of dangerous events

due to lightning flashes to a structure.

Object to be protected

Structure or service to be protected against the effects

of lightning.

Peak value (I)

Maximum value of the lightning current.

Physical damage

Damage to a structure (or to its contents) or to a

service due to mechanical, thermal, chemical or

explosive effects of lightning.

Pipes

piping intended to convey a fluid into or out of a

structure, such as gas pipe, water pipe, oil pipe.

Glossary