Breaking capacity, follow current extinguishing capability Ifi
The breaking capacity is the uninfluenced (prospective) r.m.s. value of the mains follow current which can automatically be extinguished by the surge protective device when connecting UC. It can be proven in an operating duty test according to EN 61643-11:2012.
Categories according to IEC 61643-21:2009
A number of impulse voltages and impulse currents are described in IEC 61643-21:2009 for testing the current carrying capability and voltage limitation of impulse interference. Table 3 of this standard lists these into categories and provides preferred values. In Table 2 of the IEC 61643-22 standard the sources of transients are assigned to the different impulse categories according to the decoupling mechanism. Category C2 includes inductive coupling (surges), category D1 galvanic coupling (lightning currents). The relevant category is specified in the technical data. LSP surge protective devices surpass the values in the specified categories. Therefore, the exact value for the impulse current carrying capability is indicated by the nominal discharge current (8/20 μs) and the lightning impulse current (10/350 μs).
A combination wave is generated by a hybrid generator (1.2/50 μs, 8/20 μs) with a fictitious impedance of 2 Ω. The open-circuit voltage of this generator is referred to as UOC. UOC is a preferred indicator for type 3 arresters since only these arresters may be tested with a combination wave (according to EN 61643-11).
Cut-off frequency fG
The cut-off frequency defines the frequency-dependent behaviour of an arrester. The cut-off frequency is equivalent to the frequency which induces an insertion loss (aE) of 3 dB under certain test conditions (see EN 61643-21:2010). Unless otherwise indicated, this value refers to a 50 Ω system.
Degree of protection
The IP degree of protection corresponds to the protection categories
described in IEC 60529.
Disconnecting time ta
The disconnecting time is the time passing until the automatic disconnection from power supply in case of a failure of the circuit or equipment to be protected. The disconnecting time is an application-specific value resulting from the intensity of the fault current and the characteristics of the protective device.
Energy coordination of SPDs
Energy coordination is the selective and coordinated interaction of cascaded protection elements (= SPDs) of an overall lightning and surge protection concept. This means that the total load of the lightning impulse current is split between the SPDs according to their energy carrying capability. If energy coordination is not possible, downstream SPDs are insufficiently
relieved by the upstream SPDs since the upstream SPDs operate too late, insufficiently or not at all. Consequently, downstream SPDs as well as terminal equipment to be protected may be destroyed. DIN CLC/TS 61643-12:2010 describes how to verify energy coordination. Spark-gapbased type 1 SPDs offer considerable advantages due to their voltage-switching
characteristic (see WAVE BREAKER FUNCTION).
The frequency range represents the transmission range or cut-off frequency of an arrester depending on the described attenuation characteristics.
With a given frequency, the insertion loss of a surge protective device is defined by the relation of the voltage value at the place of installation before and after installing the surge protective device. Unless otherwise indicated, the value refers to a 50 Ω system.
Integrated backup fuse
According to the product standard for SPDs, over-current protective devices / backup fuses must be used. This, however, requires additional space in the distribution board, additional cable lengths, which should be as short as possible according to IEC 60364-5-53, additional installation time (and costs) and dimensioning of the fuse. A fuse integrated in the arrester ideally suited for the impulse currents involved eliminates all these disadvantages. The space gain, lower wiring effort, integrated fuse monitoring and the increased protective effect due to shorter connecting cables are clear advantages of this concept.
Lightning impulse current Iimp
The lightning impulse current is a standardised impulse current curve with a 10/350 μs wave form. Its parameters (peak value, charge, specific energy) simulate the load caused by natural lightning currents. Lightning current and combined arresters must be capable of discharging such lightning impulse currents several times without being destroyed.
Mains-side over-current protection / arrester backup fuse
Over-current protective device (e.g. fuse or circuit breaker) located outside of the arrester on the infeed side to interrupt the power-frequency follow current as soon as the breaking capacity of the surge protective device is exceeded. No additional backup fuse is required since the backup fuse is already integrated in the SPD.
Maximum continuous operating voltage UC
The maximum continuous operating voltage (maximum permissible operating voltage) is the r.m.s. value of the maximum voltage which may be connected to the corresponding terminals of the surge protective device during operation. This is the maximum voltage on the arrester in
the defined non-conducting state, which reverts the arrester back to this state after it has tripped and discharged. The value of UC depends on the nominal voltage of the system to be protected and the installer’s specifications (IEC 60364-5-534).
Maximum continuous operating voltage UCPV for a photovoltaic (PV) system
Value of the maximum d.c. voltage that may be permanently applied to the terminals of the SPD. To ensure that UCPV is higher than the maximum open-circuit voltage of the PV system in case of all external influences (e.g. ambient temperature, solar radiation intensity), UCPV must be higher than this maximum open-circuit voltage by a factor of 1.2 (according to CLC/TS 50539-12). This factor of 1.2 ensures that the SPDs are not incorrectly dimensioned.
Maximum discharge current Imax
The maximum discharge current is the maximum peak value of the 8/20 μs impulse current which the device can safely discharge.
Maximum transmission capacity
The maximum transmission capacity defines the maximum high-frequency power which can be transmitted via a coaxial surge protective device without interfering with the protection component.
Nominal discharge current In
The nominal discharge current is the peak value of a 8/20 μs impulse current for which the surge protective device is rated in a certain test programme and which the surge protective device can discharge several times.
Nominal load current (nominal current) IL
The nominal load current is the maximum permissible operating current which may permanently flow through the corresponding terminals.
Nominal voltage UN
The nominal voltage stands for the nominal voltage of the system to be protected. The value of the nominal voltage often serves as type designation for surge protective devices for information technology systems. It is indicated as an r.m.s. value for a.c. systems.
Surge protective devices exclusively designed for installation between the N and PE conductor.
Operating temperature range TU
The operating temperature range indicates the range in which the devices can be used. For non-self-heating devices, it is equal to the ambient temperature range. The temperature rise for self-heating devices must not exceed the maximum value indicated.
Protective circuits are multi-stage, cascaded protective devices. The individual protection stages may consist of spark gaps, varistors, semiconductor elements and gas discharge tubes (see Energy coordination).
Protective conductor current IPE
The protective conductor current is the current which flows through the PE connection when the surge protective device is connected to the maximum continuous operating voltage UC, according to the installation instructions and without load-side consumers.
Remote signalling contact
A remote signalling contact allows easy remote monitoring and indication of the operating state of the device. It features a three-pole terminal in the form of a floating changeover contact. This contact can be used as break and / or make contact and can thus be easily integrated in the building control system, controller of the switchgear cabinet, etc.
Response time tA
Response times mainly characterise the response performance of individual protection elements used in arresters. Depending on the rate of rise du/dt of the impulse voltage or di/dt of the impulse current, the response times may vary within certain limits.
In high-frequency applications, the return loss refers to how many parts of the “leading“ wave are reflected at the protective device (surge point). This is a direct measure of how well a protective device is attuned to the characteristic impedance of the system.
Resistance in the direction of the signal flow between the input and output of an arrester.
Relation of the power fed into a coaxial cable to the power radiated by the cable through the phase conductor.
Surge protective devices (SPDs)
Surge protective devices mainly consist of voltage-dependent resistors (varistors, suppressor diodes) and / or spark gaps (discharge paths). Surge protective devices are used to protect other electrical equipment and installations against inadmissibly high surges and / or to establish equipotential bonding. Surge protective devices are categorised:
- a) according to their use into:
- Surge protective devices for power supply installations and devices
for nominal voltage ranges up to 1000 V
– according to EN 61643-11:2012 into type 1 / 2 / 3 SPDs
– according to IEC 61643-11:2011 into class I / II / III SPDs
The changeover of the Red/Line. product family to the new EN 61643-11:2012 and IEC 61643-11:2011 standard will be completed in the course of the year 2014.
- Surge protective devices for information technology installations and devices
for protecting modern electronic equipment in telecommunications and signalling networks with nominal voltages up to 1000 V a.c. (effective value) and 1500 V d.c. against the indirect and direct effects of lightning strikes and other transients.
– according to IEC 61643-21:2009 and EN 61643-21: 2010.
- Isolating spark gaps for earth-termination systems or equipotential bonding
- Surge protective devices for use in photovoltaic systems
for nominal voltage ranges up to 1500 V
– according to EN 50539-11:2013 into type 1 / 2 SPDs
- b) according to their impulse current discharge capacity and protective effect into:
- Lightning current arresters / coordinated lightning current arresters
for protecting installations and equipment against interference resulting from direct or nearby lightning strikes (installed at the boundaries between LPZ 0A and 1).
for protecting installations, equipment and terminal devices against remote lightning strikes, switching over-voltages as well as electrostatic discharges (installed at the boundaries downstream of LPZ 0B).
for protecting installations, equipment and terminal devices against interference resulting from direct or nearby lightning strikes (installed at the boundaries between LPZ 0A and 1 as well as 0A and 2).
Technical data of surge protective devices
The technical data of surge protective devices include information on their conditions of use according to their:
- Application (e.g. installation, mains conditions, temperature)
- Performance in case of interference (e.g. impulse current discharge capacity, follow current extinguishing capability, voltage protection level, response time)
- Performance during operation (e.g. nominal current, attenuation, insulation resistance)
- Performance in case of failure (e.g. backup fuse, disconnector, failsafe, remote signalling option)
Short-circuit withstand capability
The short-circuit withstand capability is the value of the prospective power-frequency short-circuit current handled by the surge protective device when the relevant maximum backup fuse is connected upstream.
Short-circuit rating ISCPV of an SPD in a photovoltaic (PV) system
Maximum uninfluenced short-circuit current which the SPD, alone or in conjunction with its disconnection devices, is able to withstand.
Temporary overvoltage (TOV)
Temporary overvoltage may be present at the surge protective device for a short period of time due to a fault in the high-voltage system. This must be clearly distinguished from a transient caused by a lightning strike or a switching operation, which last no longer than about 1 ms. The amplitude UT and the duration of this temporary overvoltage are specified in EN 61643-11 (200 ms, 5 s or 120 min.) and are individually tested for the relevant SPDs according to the system configuration (TN, TT, etc.). The SPD can either a) reliably fail (TOV safety) or b) be TOV-resistant (TOV withstand), meaning that it is completely operational during and following
Surge protective devices for use in power supply systems equipped with voltage-controlled resistors (varistors) mostly feature an integrated thermal disconnector that disconnects the surge protective device from the mains in case of overload and indicates this operating state. The disconnector responds to the “current heat“ generated by an overloaded varistor and disconnects the surge protective device from the mains if a certain temperature is exceeded. The disconnector is designed to disconnect the overloaded surge protective device in time to prevent a fire. It is not intended to ensure protection against indirect contact. The function of
these thermal disconnectors can be tested by means of a simulated overload / ageing of the arresters.
Total discharge current Itotal
Current which flows through the PE, PEN or earth connection of a multipole SPD during the total discharge current test. This test is used to determine the total load if current simultaneously flows through several protective paths of a multipole SPD. This parameter is decisive for the total discharge capacity which is reliably handled by the sum of the individual
paths of an SPD.
Voltage protection level Up
The voltage protection level of a surge protective device is the maximum instantaneous value of the voltage at the terminals of a surge protective device, determined from the standardised individual tests:
– Lightning impulse sparkover voltage 1.2/50 μs (100%)
– Sparkover voltage with a rate of rise of 1kV/μs
– Measured limit voltage at a nominal discharge current In
The voltage protection level characterises the capability of a surge protective device to limit surges to a residual level. The voltage protection level defines the installation location with regard to the overvoltage category according to IEC 60664-1 in power supply systems. For surge protective devices to be used in information technology systems, the voltage protection level must be adapted to the immunity level of the equipment to be protected (IEC 61000-4-5: 2001).
Planning of internal lightning protection and surge protection