First: Lightning and Surge protection terminology
A
|
|
Air
Termination
|
Shall
mean that part of a lightning protection system designed to capture the
lightning strike. Normally is mounted on the roof of the structure and is
bonded to the down conductor.
|
Alternating
Discharge Current
|
The
alternating discharge current is the r.m.s. value of the almost sinusoidal
power-frequency current that flows through the surge voltage limiter.
|
Amperage
|
IEEE has
developed waveform guidelines for testing. In this guideline, discharge
currents (surge currents) are given as 200A, 500A, and 3000A. These values,
when combined with the appropriate transient waveshape represent possible
transient activity according to
ANSI/IEEE
C62.41.
|
Arc
Combustion Voltage
|
The
arc combustion voltage (Vbo) is the instantaneous value of the voltage on the
discharge path while an arc discharge is being arrested.
|
Average
steepness of the short stroke current
|
Average rate of
change of current within a time interval t2 – t1. It is
expressed by the difference i(t2) – i(t1) of the values of
the current at the start and at the end of this interval, divided by t2 – t1.
|
B
|
|
Bond
(bonding)
|
Shall mean a
conductor intended to provide electrical connection between a lightning
protection system and other metalwork and between various metal parts of a
structure or between earthling systems.
|
Bonding bar
|
Metal bar on
which metal installations, external conductive parts, electric power and
telecommunication lines and other cables can be bonded to a Lightning
Protection System.
|
Bonding
conductor
|
Conductor
connecting separated conducting parts to a Lightning Protection System.
|
Bonding network
|
Interconnecting
network of all conductive parts of the structure and of internal systems
(live conductors excluded) to the earth termination system.
|
Burst
|
This pulse is
repeated at certain time intervals.
|
C
|
|
Captive
Coupling
|
Formed by the
strength of the voltage field surrounding a conductor. The voltage field
causes a current to flow in an adjoining conductor to an area of lower field
strength. Proportional to voltage or conductor.
|
Clamping
Voltage
|
Shall mean
the voltage at which the surge arrester starts to conduct. Units typically in
RMS Voltage.
|
Class of LPS
|
Number denoting
the classification of a Lightning Protection System (LPS) according to the
lightning protection level for which it is designed.
|
Combination type
SPD
|
Surge Protective
Device (SPD) that incorporates both voltage switching and voltage limiting
type components and which may exhibit voltage switching, voltage limiting or
both voltage switching and voltage limiting behavior, depending upon the
characteristics of the applied voltage (IEC 61643-1:1998).
|
Connecting
component
|
Part of an
external Lightning Protection System, which is used for the connection of
conductors to each other or to metallic installations.
|
Conventional
earth impedance
|
Ratio of the
peak values of the earth termination voltage and the earth termination
current, which in general, do not occur simultaneously.
|
Coordinated SPD
protection
|
Set of Surge
Protective Devices (SPDs) properly selected, coordinated and installed to
reduce failures of electrical and electronic systems.
|
Common Mode
Voltage
|
The common
mode voltage is the voltage that occurs in the case of interference between
active conductors and ground.
|
Continuous
Operating Voltage
|
The
continuous operating voltage (Vc) is the highest r.m.s. power-frequency
voltage that may be constantly applied to the arrester terminal blocks.
|
Coupling
|
Interaction
between circuits, during which energy is transmitted from one circuit to the
other.
|
D
|
|
Dangerous event
|
Lightning flash
to the object to be protected or near the object to be protected.
|
Dangerous
sparking
|
Electrical
discharge due to lightning, which causes physical damage in the structure to
be protected.
|
Direct
Coupling
|
A physical
connection of two or more electrical conductors.
|
Disconnect
Device (Fuse, Breaker)
|
This is a
device that disconnects an arrester from the system when it fails so that
fire hazard is prevented and the defective arrester is indicated. Note: the
disconnect device is not responsible for providing protection against
electric shock by indirect contact.
|
Down
conductor
|
Shall mean a
conductor which connects an earth termination to the (a) System 3000
Dynasphere Terminal or (b) Copper/Stainless Steel air Termination Tape or
Finials which are intended to capture lightning discharges and form part of a
lightning protection system.
|
Down conductor
system
|
Part of an
external Lightning Protection System which is intended to conduct lightning
current from the air termination system to the earth-termination system.
|
Downward flash
|
Lightning flash
initiated by a downward leader from cloud to earth. A downward flash consists
of a first short stroke, which can be followed by subsequent short strokes.
One or more short strokes may be followed by a long stroke.
|
Duration of long
stroke current (Tlong)
|
Time duration
during which the current in a long stroke is between the 10% of the peak
value during the increase of the continuing current and 10% of the peak value
during the decrease of the continuing current.
|
Dynamic Test
|
Test
conducted with normal operating voltage applied.
|
Dynasphere
|
Is an air
terminal designed to capture a lighting strike with the use of Controlled Streamer
Emission (CSE) Technology.
|
E
|
|
Earth
Termination (earth termination network)
|
Shall mean
that part of an earthing system that makes contact with, and is intended to
discharge currents to the general mass of earth. In the case of a lightning
protection system, this includes all parts below any test link.
|
Earth
Conductor
|
Shall mean
the conductor making the final connection to the earth rod or electrode.
|
Earthing
Electrodes
|
Shall mean
those portions of the earth termination, which make direct low resistance /
impedance electrical contact with the earth.
|
Earthing
Resistance/Impedance
|
Shall mean
the resistance/impedance of the earthing system to the general mass of earth,
as measured from a test point.
|
Earthing
System
|
Shall mean
and include all conductors, piping, electrodes, clamps and other connections
and earthing compounds whereby installations are earthed.
|
Electrical
Engineering Consultant
|
Shall mean an
eminent expert in a sub-discipline of Electrical Engineering.
|
Electromagnetic
Compatibility (EMC)
|
EMC is the
ability of a device to function satisfactorily in its electromagnetic
environment, without producing interference which cannot be tolerated in this
environment or by other devices.
|
Electromagnetic
Interference
|
Electromagnetic
interference is the loss of performance, malfunctions or failure of an
electrical or electronic device caused by electromagnetic interference.
|
Electromagnetic
shield
|
Closed metallic
grid-like or continuous screen enveloping the object to be protected, or part
of it, used to reduce failures of electrical and electronic systems.
|
Electronic
system
|
System
incorporating sensitive electronic components such as communication
equipment, computer, control and instrumentation systems, radio systems,
power electronic installations.
|
Earth
termination voltage
|
Potential
difference between the earth termination system and the remote earth.
|
Electrical
system
|
System
incorporating low voltage power supply components and possibly electronic
components.
|
Energy
|
Maximum
allowable energy for a single impulse on a 10/1000mS current
waveform. Indicative of the maximum amount of energy that the suppressor can
dissipate. This energy is transitory and is dependent upon three (3)
variables: 1) voltage, 2) current, and 3) time. Any variation of the three
will effect this figure.
|
Equipment to
be Protected
|
All devices
of a structural system or a range which require surge voltage protection or
lightning protection.
|
Equipotential
Bonding
|
This is the
elimination of differences in potential between conductive parts, whereby all
points take on approximately the same potential. A distinction is made
between functional equipotential bonding and protective equipotential
bonding.
|
Equipotential
Bonding System
|
This refers
to all the interconnected equipotential bonding conductors, including the
conductive parts such as housings or extraneous conductive parts, which work
in the same way. The equipotential bonding system can also be a grounding
system or part of a grounding system.
|
Equipotential
Conductor
|
These are
electrically conductive connections which serve to produce the equipotential
bonding.
|
External
conductive parts
|
Extended metal
items entering or leaving the structure to be protected such as pipe works,
cable metallic elements, metal ducts, etc which may carry a part of the
lightning current.
|
External
lightning protection system
|
Part of the
Lightning Protection System consisting of an air termination system, a down
conductor system and an earth termination system. Typically these parts are
outside the structure.
|
External LPS isolated
from the structure to be protected
|
Lightning
Protection System (LPS) whose air termination system and down conductor
system are positioned in such a way that the path of the lightning current
has no contact with the structure to be protected. In an isolated Lightning
Protection System dangerous sparks between the Lightning Protection System
and the structure are avoided.
|
External LPS not
isolated from the structure to be protected
|
Lightning
Protection System (LPS) whose air termination system and down conductor
system are positioned in such a way that the path of the lightning current
can be in contact with the structure to be protected.
|
F
|
|
Failure current
(la)
|
Minimum peak
value of lightning current that will cause damage in a line.
|
Failure of
electrical and electronic system
|
Permanent damage
of electrical and electronic system due to LEMP.
|
Fixing component
|
Part of an
external Lightning Protection System, which is used to fix the elements of
the Lightning Protection System to the structure to be protected.
|
Flash charge
(Qflash)
|
Time integral of
the lightning current for the entire lightning flash duration.
|
Flash duration
(T)
|
Time for which
the lightning current flows at the point of strike.
|
Foundation
earthing electrode
|
Reinforcing
steel of foundation or additional conductor embedded in the concrete
foundation of a structure and used as an earthing electrode.
|
Filter
Frequency Range
|
The range of
frequency in which a filter operates. This is usually dictated by the -3db points
on the low and high ends of the frequency scale.
|
Follow-Through
Current
|
This is the
current which follows the leakage current under the influence of the
operating voltage. It is given as a peak value. Note: with some arrester
types (e.g. Metal-Oxide-Varistors) the follow-through current is very small
(<1 mA).
|
Frequency
(Noise) Attenuation
|
The range of
attenuation for a given frequency range. A larger negative number indicates a
greater attenuation.
|
G
|
|
Grid-like
spatial shield
|
Electromagnetic
shield characterised by openings. For a building or a room, it is preferably
built by interconnected natural metal components of the structure (eg rods of
reinforcement in concrete, metal frames and metal supports).
|
Gas Filled
Surge Arrester
|
The gas
filled surge arrester is a discharge path that is filled with another gas
than air, generally an inert gas.
|
Ground
|
This
expression refers to the soil and the ground.
|
Grounding
|
Grounding
describes all methods and measures utilized.
|
Grounding Busbar
|
this is the
rail which is used to connect equipment grounding conductors, equipotential
bonding conductors and, if necessary, functional grounding conductors with
the ground conductor and the ground electrodes.
|
Ground
Conductor
|
This is a
conductor that connects a device to be grounded with a ground electrode. This
is only relevant when the ground conductor is not embedded in the ground.
|
Ground
Electrode
|
This is a
conductor that is embedded in the ground and is conductivity connected to it.
Parts of feed lines that are in the ground but are not insulated are regarded
as parts of the ground electrode.
|
Ground Flash
(Earth Discharge)
|
Means a
lightning flash in which at least one discharge channel reaches the ground.
|
Ground
Resistance
|
This is the
resistance between the grounding system and the reference ground. The amount
of ground resistance results from the combined effect of the individual
ground electrodes and soil conditions.
|
I
|
|
Injuries of
living beings
|
Injuries,
including loss of life, to people or to animals due to touch and step
voltages, fire or explosion caused by lightning.
|
Interconnected
reinforcing steel
|
Steelwork within
a concrete structure, which is considered electrically continuous.
|
Internal
lightning protection system
|
Part of the
Lightning Protection System consisting of lightning equipotential bonding and
compliance with the separation distance within the structure to be protected.
|
Internal system
|
Electrical and
electronic systems within a structure.
|
Inductive Coupling
|
Formed by the
magnetic field surrounding a conductor with a changing current flowing
through it. When the magnetic flux lines are cut by another conductor, a
voltage is developed on that conductor. The greater the rate of change of the
flux lines, the greater the voltage developed.
|
Impulse
Withstand Voltage
|
The peak
value of the highest impulse voltage (Vst) with a preset form and polarity,
which will not lead to a disruptive charge under the given test conditions.
Note: the
surge voltage is equal to or greater than the rated surge voltage.
|
Input Power
Frequency - frequency
|
Range in
which the suppressor operates without causing damage to suppressor or
equipment, or interference with the power signal. Applicable to AC circuits.
|
Intrinsically
Safe Circuit
|
A circuit
protected against sparks and ignition and thermal effects (as specified in
the DIN VDE 0170/0171 standard which applies to normal operation and specific
conditions) which could cause an ignition in an explosive atmosphere.
|
J
|
|
Joint
|
Shall mean a
mechanical and electrical junction between two or more portions of a
lightning protection system.
|
L
|
|
LEMP Protection
Measures System (LPMS)
|
Complete system
of protection measures for internal systems against LEMP.
|
Lightning
current (i)
|
Current flowing
at the point of strike.
|
Lightning
Electromagnetic Impulse (LEMP)
|
Electromagnetic
effects of lightning current. It includes conducted surges as well as
radiated impulse electromagnetic field effects.
|
Lightning
Equipotential Bonding (EB)
|
Bonding to the
Lightning Protection System of separated metallic parts, by direct conductive
connections or via surge protective devices, to reduce potential differences
caused by lightning current.
|
Lightning flash
near an object
|
Lightning flash
striking close enough to an object to be protected that it may cause
dangerous overvoltages.
|
Lightning flash
to an object
|
Lightning flash
striking an object to be protected.
|
Lightning flash
to earth
|
Electrical
discharge of atmospheric origin between cloud and earth consisting of one or
more strokes.
|
Lightning
protection designer
|
Specialist
competent and skilled in the design of a Lightning Protection System.
|
Lightning
protection installer
|
Person competent
and skilled in the installation of a Lightning Protection System.
|
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 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).
|
Lead Length
|
The length of
leads, whether integral to the unit or added to effect field connection,
extending from the suppression device enclosure on a hard wire panel unit.
This is an important factor in testing, as specifications should reflect
actual installation application.
|
Leakage
Current
|
The minuscule
current flowing through insulators, electronic components which are in a
non-conductive state, or any two points which are insulated between each
other. A rising leakage current can be a warning of impending insulation or
component failure.
|
Let-through
Voltage
|
Shall mean
the voltage appearing on the equipment side of a surge arrester when an
impulse voltage-current, with the voltage exceeding the clamping voltage is
applied to the input. Surge arresters have non-linear V-1 characteristics,
and the let-through voltage increases significantly depending on the peak
current in the surge.
|
Lightning
Flash (lightning discharge)
|
Shall mean an
electrical discharge in the atmosphere involving one or more electrically
charged regions, and shall include flashes that do or do not reach the
ground.
|
Lightning
Protection System
|
Shall mean a
System designed to reduce the injurious and damaging effects of lightning by
providing a safe path for capture and conducting lightning energy to ground.
|
Lightning
Strike
|
Is the term
used to describe a lightning flash when the attention is centered on the
effects of the flash at the point where it connects to the ground or a
structure.
|
Lightning
Stroke
|
Is the term
used to describe an individual current impulse in a complete ground flash.
|
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.
|
Listings
|
Statement of
independent laboratory testing, for safety and/or performance.
|
Location
Categories
|
Shall mean
the categories for the placement of protective equipment as per ANSI C62.41.
|
M
|
|
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).
|
Maximum
Continuous Operating Voltage (MCOV) (of a surge arrester)
|
Shall mean
the maximum RMS voltage that can be applied continuously between the
terminals of a surge arrester without inhibiting its correct operation.
|
Mesh method
(MM)
|
Method to
determine position of air-termination system
|
Metallic
Sheath (of a cable)
|
Shall include
any conductive sheath, armor or screen.
|
N
|
|
“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.
|
Nominal
Voltage
|
Normal
operating voltage or average voltage at which equipment operates.
|
Normal Mode
Voltage
|
Normal mode
voltage is voltage interference between two conductors of a circuit. (Line to
Line)
|
O
|
|
Object to be
protected
|
Structure or
service to be protected against the effects of lightning.
|
P
|
|
Peak Surge
Current
|
Maximum
current allowed for a single 8x20mS impulse waveform with continuous
voltage applied. The higher the number, the stronger the unit.
|
Phase Angle
|
The point on
the sine wave at which a transient occurs. IEEE states that transients can
occur at any phase angle. It is important to be able to see suppression
device response to transients at varying phase angles.
|
Physical
Dimensions
|
The length,
width and height or depth or the suppression device. When considering space
constraints in any application, this specification affords quick
determination of acceptability.
|
Physical damage
|
Damage to a
structure (or to its contents) or to a service due to mechanical, thermal,
chemical or explosive effects of lightning.
|
Point of strike
|
Point where a
lightning flash strikes the earth, or a protruding object (eg structure,
Lightning Protection System, service, tree, etc). A lightning flash may have
more than one point of strike.
|
Probability of
damage (PX)
|
Probability that
a dangerous event will cause damage to or in the object to be protected.
|
Protection
measures
|
Measures to be
adopted in the object to be protected to reduce the risk.
|
Protection
angle method (PAM)
|
Method to
determine position of air-termination system
|
Positive or
Negative Polarity
|
Indicates
direction in which the surge occurs.
|
Power
|
Shall mean
electrical power, (e.g., power apparatus refers to electrical power
apparatus.)
|
Power-Frequency
Withstand Voltage
|
This is the
r.m.s. value of the highest sinusoidal voltage with system frequency that
will not lead to a disruptive charge under the given test conditions.
|
Pressure
Relief Device
|
Relieves the
arrester of internal over-pressure in the case of overload.
|
Protection
Modes
|
Protection
mode indicates suppressor’s ability to protect different paths of transient
activity. Normal mode = line to neutral and/or line to line. Common mode =
line to ground and/or neutral to ground.
|
R
|
|
Rated impulse
withstand voltage (UW)
|
Impulse
withstand voltage assigned by the manufacturer to the equipment or to a part
of it, characterising the specified withstand capability of its insulation
against overvoltages. For the purpose of BS EN 62305, only withstand voltage
between live conductors and earth is considered. [IEC 60664-1:2002]
|
Ring conductor
|
Conductor
forming a loop around the structure and interconnecting the down-conductors
for distribution of lightning current among them.
|
Ring earthing
electrode
|
Earthing
electrode forming a closed loop around the structure below or on the surface
of the earth.
|
Risk (R)
|
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.
|
Risk component (RX)
|
Partial risk
depending on the source and the type of damage.
|
Rural
environment
|
Area with a low
density of buildings. ”Countryside” is an example of a rural environment.
|
Rolling
sphere method (RSM)
|
Method to
determine position of air-termination system
|
Rated Voltage
|
Rated voltage
is the desired normal continuous operating voltage at which surge components
are specified.
|
Residual
Voltage
|
The rated
peak voltage reached while surge current is flowing through the surge
arrester.
|
Response Time
|
The time in
which a suppression device responds to a transient.
|
S
|
|
Separation
distance
|
Distance between
two conductive parts at which no dangerous sparking can occur.
|
Service to be
protected
|
Service
connected to a structure for which protection is required against the effects
of lightning in accordance with this standard.
The service to
be protected comprises the physical connection between:
– the switch
telecommunication building and the user’s building or two switch
telecommunication buildings or two user’s buildings, for the
telecommunication (TLC) lines;
– between the
switch telecommunication building or the user’s building and a distribution
node, or between two distribution nodes for the telecommunication (TLC)
lines;
– the high voltage
(HV) substation and the user’s building, for the power lines;
– the main
distribution station and the user’s building, for pipes.
|
Shielding wire
|
Metallic wire
used to reduce physical damage due to lightning flashes to a service.
|
Short stroke
|
Part of the
lightning flash which corresponds to an impulse current. This current has a
time to the half value T2 typically
less than 2ms.
|
Short stroke
charge (Qshort)
|
Time integral of
the lightning current in a short stroke.
|
SPD tested with
a combination wave
|
Surge Protective
Devices (SPDs) that withstand induced surge currents with a typical waveform
8/20μs and require a corresponding impulse test current Isc. For power
lines a suitable combination wave test is defined in the Class III test
procedure of IEC 61643-1 defining the open circuit voltage Uoc 1,2/50μs and the
short circuit current Isc 8/20μs of a 2Ω combination wave
generator.
|
SPD tested with
(Iimp)
|
Surge Protective
Devices (SPDs) which withstand the partial lightning current with a typical
waveform 10/350μs require a corresponding impulse test current Iimp. For power
lines, a suitable test current Iimp is defined in the Class I test procedure
of IEC 61643-1.
|
SPD tested with
(In)
|
Surge Protective
Devices (SPDs) which withstand induced surge currents with a typical waveform
8/20μs require a corresponding impulse test current In. For power
lines a suitable test current In is defined in the Class II test procedure of
IEC 61643-1.
|
Specific energy
(W/R)
|
Time integral of
the square of the lightning current for the entire flash duration; it
represents the energy dissipated by the lightning current in a unit
resistance.
|
Specific energy
of short stroke current
|
Time integral of
the square of the lightning current for the duration of the short stroke. The
specific energy in a long stroke current is negligible.
|
Structure to be
protected
|
Structure for
which protection is required against the effects of lightning in accordance
with BS EN 62305. A structure to be protected may be a part of a larger structure.
|
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).
|
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. For the purposes of BS EN 62305
structures with hazardous zones type 0 or containing solid explosive
materials are considered.
|
Suburban environment
|
Area with a
medium density of buildings. ”Town outskirts” is an example of a
suburban environment.
|
Surge
|
Transient wave
appearing as overvoltage and/or overcurrent caused by LEMP. Surges caused by
LEMP can arise from (partial) lightning currents, from induction effects in
installation loops and as a remaining threat downstream of a Surge Protective
Device (SPD).
|
Surge Protective
Device (SPD)
|
Device that is
intended to limit transient overvoltages and divert surge currents. It
contains at least one non-linear component (see IEC 61643 series).
|
Side Flash
|
Shall mean a
discharge occurring between nearby metallic objects or from such objects to a
lightning protection system or to earth.
|
Sparkover
Voltage
|
The voltage
at which a surge arrester becomes conductive.
|
Stage (of
protection)
|
Describes the
configuration of circuit elements of a surge protective device. Each phase or
line of a typical protective device might be composed of the following
elements:
|
Static Test
|
Test
conducted with no normal operating voltage applied.
|
Structure
|
Shall mean
any building or construction, process plant, storage tank, tree, or similar,
on or in the ground.
|
Surge
Arrester (Shunt Diverter)
|
shall mean a
protective device, usually connected between any conductor of a system and
earth, tested IEC1643 and ANSI C62.1, which limits surge voltages by
diverting surge current to earth when a given voltage is exceeded. The
let-through voltage must be within a certain tolerance acceptable to the
equipment being protected.
|
Surge
Arresting Capacity
|
This is the
rated maximum current a surge arrester is capable of shunting to ground.
|
Surge
Arrestors
|
Consist
mainly of voltage dependent resistors and/or discharges. The two elements are
connected either in series or in parallel, but each can also be used on its
own. Arresters are used to protect other electrical equipment and electrical
systems against inadmissible surge voltages.
|
Surge Current
|
The surge
current is the current flowing through the arrester after it has sparked
over. It is given as a peak value.
|
Surge Current
Rating
|
Shall mean
the peak value of a standard one-shot 8/20 microsecond impulse current wave
that a surge arrester can absorb without damage.
|
Surge
Reduction FilterÔ (SRFÔ)
|
Shall be an
in-line series filter designed to remove all surges and transients to an
acceptable level produced by a lightning strike.
|
Surge Voltage
|
The surge
voltage is the permanent or temporary voltage between conductors or between
conductor and ground in functioning systems (also in switched off systems)
which can endanger people and have damaging effects on cables and connected
devices.
|
Surge Voltage
Arrester
|
This is a
device for limiting the surge voltage between two parts within the volume to
be protected, e.g. spark gaps, valve arresters or semiconductors.
|
Surge Voltage
Category
|
Allocation of
an electrical device to the expected surge voltage.
|
Surge Voltage
Limiter
|
Surge voltage
limiters are components and protective circuits, which limit surge voltages
in systems or devices to permissible values.
|
Surge Voltage
Protection Appliances
|
Surge voltage
protection appliances are surge voltage limiters together with all the
appliances in telecommunications systems including the cables for surge
voltage protection.
|
Surge Voltage
Protection Arrangement
|
This is an
element, a group or an appliance that limits the expected surge voltage.
|
Switching
Surge Voltage
|
This is surge
voltage caused by a switching operation.
|
T
|
|
Test joint
|
Joint designed
to facilitate electrical testing and measurement of Lightning Protection
System components.
|
Time to peak
value of short stroke current (t1)
|
Virtual
parameter defined as 1.25 times the time interval between the instants when
the 10% and 90% of the peak value are reached.
|
Time to half
value of short stroke current (t2)
|
Virtual
parameter defined as the time interval between the virtual origin O1 and the
instant at which the current has decreased to half the peak value.
|
Tolerable risk (RT)
|
Maximum value of
the risk, which can be tolerated for the object to be protected.
|
To Ground
|
To ground
means to connect an electrically conductive component (e.g. the lightning
protection system) with the ground via a grounding system.
|
Transient
|
These are
irregular and relatively short positive and/or negative voltage or current
changes between two stationary states.
|
Test Link
|
Shall mean a
joint designed and situated so as to allow resistance/impedance or continuity
measurements to be made.
|
Thunderday
|
Shall mean a
calendar day during which thunder is heard at a given location. The
international definition of lightning activity is given as the number of
thunderdays per year (also called isokeraunic level)
|
Transient
Earth Clamp (TEC)
|
Shall mean a
device placed in the bond between the lightning earth and the MEN earth to
equalize potentials during a lightning strike.
|
U
|
|
Upward flash
|
Lightning flash
initiated by an upward leader from an earthed structure to cloud. An upward
flash consists of a first long stroke with or without multiple superimposed
short strokes. One or more short strokes may be followed by a long stroke.
|
Urban
environment
|
Area with a high
density of buildings or densely populated communities with tall buildings.
”Town centre” is an example of an urban environment.
|
V
|
|
Virtual origin
of short stroke current (O1)
|
Point of
intersection with time axis of a straight line drawn through the 10% and the
90% reference points on the stroke current front; it precedes by 0.1T1 that
instant at which the current attains 10% of its peak value.
|
Voltage
switching type SPD
|
SPD that has a
high impedance when no surge is present, but can have a sudden change in
impedance to a low value in response to a voltage surge. Common examples of
components used as voltage switching devices include spark gaps, gas
discharge tubes (GDT), thyristors (silicon controlled rectifiers) and triacs.
These SPD are sometimes called “crowbar type“. A voltage switching device has
a discontinuous voltage/current characteristic. (IEC 61643-1:1998)
|
Voltage limiting
type SPD
|
SPD that has a
high impedance when no surge is present, but will reduce it continuously with
increased surge current and voltage. Common examples of components used as
non-linear devices are varistors and suppressor diodes. These SPDs are
sometimes called “clamping type“. A voltage-limiting device has a continuous
voltage/current characteristic. (IEC 61643-1:1998)
|
Varistors
|
The varistor
is a bipolar non-linear resistor with a symmetrical voltage/current
characteristic curve whose resistance value decreases as the voltage
increases.
|
Voltage
|
the peak
transient voltage which is applied to unit under test according to ANSI/IEEE C62.41
1980, section 4.1: “...This 6 KV level, therefore, can be selected as a
typical cutoff for the occurrence of surges in indoor power systems.”
|
W
|
|
Weight
|
Weight of
suppression device. Useful in determining application and installation
requirements.
|
Z
|
|
Zone of a
structure (ZS)
|
Part of a
structure with homogeneous characteristics where only one set of parameters
is involved in assessment of a risk component.
|
Second: Lightning and Surge protection Abbreviations (see fig.1)
Fig(1): Lightning and Surge protection Abbreviations |
Third: Lightning and Surge protection Sign and Symbols (see fig.2)
Fig (2): Lightning and Surge protection Sign and Symbols |
In the next Article, I will continue explaining the introduction to lightning design. Please, keep following.
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