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External lightning protection
Comprises the entire number of external devices installed at the outside and in the equipment to be protected with the task to arrest, limit and conduct lightning currents into the earthing unit.
Earthing system of a SPD
This is the ground discharge of a lightning protection system installed for conducting the lightning current into the ground.
Equipotential bonding
(acc. to VDE 01 90) This term defines the equalisation of potential differences (in connection with the operation of electric equipment) occurring, for example, between the protector of a heavy current facility and water-, gas- or heating pipe systems or in-between these pipe systems. In order to equalise potential differences after a lightning strike, measures going beyond the requirements of VDE 01 90 are necessary. The lightning strike protection system is reinforced with additional metallic installations via power lines or isolating spark gaps, if necessary also with active parts of electric equipment by means of surge protectors. These measures are also called “lightning protection equipotential bonding”.
Follow-on current
Is the current following the discharge current after response of the operating voltage. It is indicated as peak value. Remark: with some types of SPDs (e.g. metal oxide varistors) the follow-on current is very weak, i.e.< 1 mA.
Foundation earthing system
This is a surge protector embedded in the concrete foundation of a building.
Impulse current 8/20 µs
It has a rise time of 8 µs and a decay time to half value of 20 µs.
Impulse current limit Isgr
This is a lightning current simulating the impulse current resistance of discharge tubes upon direct lightning strike.
Impulse discharge current
This is the impulse current which flows through the surge protector once it has responded. It is indicated as peak value. The nominal impulse discharge current is the peak value of an impulse current with a 8/20 µs wave form.
Internal lightning protection
Comprises the entire measures taken against consequences of lightning current and its electric and magnetic fields on metallic installations and electrical equipment inside a building.
Insulation resistance Ris
This is the resistance measured in ohms of a surge protector in stand-by mode.
Isolating spark gaps
for lightning protection devices. These are isolating spark gaps designed to separate conductive parts of electric equipment. These equipment parts are temporarily connected due to the response of the isolating spark gap.
Insulating resistance Ris
After 24 h storage in 95% relative air humidity, Leutron-arresters have an insulating resistance of >10¹ºΩ. Leutron-arresters with higher insulating resistance are available on demand.
Lightning impulse current
This is the test current level at which lightning current parameters are simulated. It is determined by: – the lightning current amplitude is (kA) – the rate of rise di/dt (A/s) – the specific energy ƒi² dt(J/Ω) – the charge level ƒi dt (As)
Lightning impulse spark-over voltage
is defined as the spark-over voltage at 1.2/50 µs lightning impulse voltage triggering spark-over. Remark: with some types of SPDs it is not possible to calculate the 100% lightning impulse spark-over voltage (i.e. varistors).
Lightning current surge protection system
This is the entire number of devices installed for internal and external lightning protection for a defined equipment.
Longitudinal voltage drop
SPDs for DC or low operating frequencies up to max. 400 Hz are assessed as to their longitudinal voltage drop properties along the current path/s at nominal current and, where necessary, at operating frequency rather than determining their insertion loss capacity.
Mains supply short-circuit current IK
This is the short-circuit resulting from the impedance of the test mains and the connected lines at the place where a test conductor is installed.
Measuring voltage Ur
Is the maximum permissible actual level of the operating AC voltage to which the protection device is tuned. Remark: for all surge protective devices in the present documentation this value is equivalent to rated voltage Uc.
Maximum impulse discharge current
Maximum peak value of a 8/20 current impulse at which the arresters are not destroyed mechanically or interrupted. Leutron‑arresters have a high discharge capability and therefore offer top safety.
Nominal AC discharge current Iwn
This is the AC discharge current for 15 Hz to 62 Hz frequencies (mostly 50Hz level) at which the test SPD is measured with a specific test programme.
Nominal DC spark-over voltage Uagn
This is the DC spark-over voltage level indicated by the manufacturer of SPDs for a specific type of surge protector.
Nominal impulse discharge current Isn
This is the peak value of an impulse current with a defined duration upon which a SPD is tested with a specific test programme. The course of the impulse discharge current whose wave form corresponds to 8/20 µs is determined in DIN VDE 0432 T2.
Nominal impulse spark-over voltage Uasn
This is the maximum permissible level of impulse sparkover voltage.
Nominal penetration voltage Udn
This is the voltage level on the equipment to be protected at the beginning of the arresting effect. Usually it is measured at a constant discharge current of 1 mA. For SPDs with low limiting voltages and comparatively high rejection currents it can also be based on 10mA. The penetration voltage indicates the voltage level at the equipment under protection at the exact moment when it changes from rejection mode to conducting mode. The deviation from penetration voltage to nominal penetration voltage within a consignment must be indicated in per cent, whereby deviations of 2, 5 and 10% are considered normal and usual.
Nominal voltage
Serves as reference for different types of surge protection devices defining the maximum operating voltage a SPD can be loaded with.
Nominal impulse discharge current
Peak value of the maximum admissible 8/20 current impulse (8µs time to rise and 20µs time to half-value). Leutron-arresters can be discharged with this current impulse for at least 10 times.
Nominal alternating discharge current
Rated rms value of an AC current (15…62Hz) applied to an arrester several times for 1 s each time. Leutron arresters excel by their high AC current discharge capability.
Operating frequency range
This is defined by the insertion loss of a surge protector which will not exceed a certain frequency range.
Potential equalisation bar
This is a metallic rail connecting earthing lines, equipotential bonding lines and, where necessary or existent, surge protectors.
Prospective short-circuit current of a test loop
The current which would flow at a specific part of a test circuit if the test specimen was short-circuited at this place at negligible impedance.
Protection level
This is the higher value of either 100% ightning current spark-over voltage or residual voltage at nominal discharge current.
Rated frequency
This is the rated frequency of the mains for which the SPD has been dimensioned.
Rated voltage Uc
Is the maximum permissible actual level of the operating AC voltage hich can be permanently connected to the SPD terminals.
Residual voltage
This is the peak value of the voltage at the terminals of a SPD during discharge current flows.
Service life test
This is a test simulating frequently happening overload situations on SPDs.
Spark-over
This is the moment where either the peak value of the ohmic part of the current flowing through the SPD reaches 5 mA or where a voltage drop takes place due to the fact that the current peak level flowing through the SPD has risen beyond 5 mA.
Spark-over voltage
This is the highest momentary voltage level reached at the SPD’s terminals before spark-over.
Storage temperature range
This defines the temperature zone in which a SPD can be stored without risk of negative influence on its nominal values and properties.
Surge protective devices (or arresters)
These are modules and protection circuits limiting surge voltages in equipment or devices down to permissible levels. Protection circuits are devices which consist of discharge tubes, varistors, semi-conductor elements and decoupling coils, switched in a circuit as defined, for example, by DIN VDE 0845, part 1/10.87, par. 4.2.2: serial circuits consisting of discharge tube and varistor plus discharge tube and diode parallel circuits consisting of discharge tube and varistor combined parallel and serial circuits as complete protection systems
Telecommunication equipment
Including data processing units (referred to as telecommunications equipments herein) is equipment for transmission and processing of messages and teleinformation by means of electric devices, such as electric measuring systems and automatic control devices (MSC) for the registration and processing of measured values (measuring units).
Thermal disconnection device
This is a device separating a conductor from the mains in case of failure to function, thus preventing a possible fire hazard and indicating the deficient arrester at the same time. Remark: the thermal disconnector does not have to ensure the proper functioning of the safety measure called "protection in case of indirect contact".
Glow-voltage
Voltage level at the ignited arrester at a current level of 10 mA.
Arc discharge voltage va
Voltage level of arrester in the arc area. Ranges usually between 10 and 20 V.
Capacitance C
Leutron-arresters have a self-capacitance of ca. 1 pF.
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