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No, Leutron surge arresters can divert lightning currents several times. This was also demonstrated by various laboratory tests whose results are also confirmed in our many years of field experience.
Yes. It is typical that somewhere a lightning strikes and the lightning current searches all possible ways direction „earth“. A part often flows into the power and telephone network and damages the surrounding connected devices. There are studies that telephone systems were still damaged 3 km away from a lightning strike.
This information is the maximum leakage current of the protective components used. The higher this value is, the greater may be an overvoltage without destroying the protective device, or the more frequently smaller overvoltage can be dissipated without destruction. These ampere numbers increase the performance and life of the surge protective device.
Since DSL signals are very sensitive, the additional signal attenuation of the overvoltage protection device can sometimes impair the DSL connection (e.g. reduced transmission speed or disconnections). Whether this problem occurs or not depends on the DSL signal quality at the port. This in turn depends on the distance of the connection from the switching station, the used cable cross-section and possibly influencing disturbances. A concrete statement as to whether or not the overvoltage protection can be used without problems in the application can unfortunately not be made. In general, however, DSL connections with high transmission rates are particularly sensitive due to the higher frequencies used and thus more problematic.
The overvoltage protection should preferably be inserted at the LNB connection of the multi-switch (i.e. between the LNB and the multi-switch). In this case, therefore, eight pieces overvoltage protection plugs would be required.
With the TNS device (4-pole), varistor arresters are plugged into all 4 slots (L1-L3 + N) and connected to ground (PE). With the TT device, only L1-L3 is provided with varistors, the outputs are then fed together with N via a spark gap module to PE.
No! In the case of the TT network, the PE is not connected to N in contrast to the TNS network.
N may only be grounded in the substation, and there may still be impedance between the earth and the transformer star point. It follows that PE and N do not have to have the same potential.
Usually, this will only be a handful of volts, but e. q. in lightning strikes or large currents in the earth (railway line, gas line with electrical corrosion protection, etc.) may also higher voltage differences occur.
If the varistor is now aging and / or overloaded, the house installation can become the auxiliary earthing for the substation. The spark gap now has the advantage that it does not age (become low-impedance) and can become conductive over time.
Surge arresters are divided into three classes: Type 1, 2 or 3. The arresters differ in their discharge capacity and in the protection level (maximum voltage in the case of a discharge process).
Yes! Although the earth-sensitive foundations provide a certain earthing function, however, a meshed earthing system is necessary from a lightning protection point of view. With earth-sensitive foundations, however, it is possible to use them as part of the grounding system.
The Supplement 5 of DIN EN 62305 Part 3 provides detailed information on this.
No, installing a standard PV system on or on a building does not increase the risk of lightning.
The cross-sections of conductors used in lightning protection must be applied as described in EN 62305-3 (VDE 0185-305-3) Tables 18.104.22.168 and 22.214.171.124.
Table 126.96.36.199 describes the minimum dimensions of conductors that connect different equipotential bus bars to each other or to the earthing system.
The minimum cross sections for protection class I to IV are:
Copper = 16 mm²
Aluminium = 25 mm²
Steel = 50 mm²
Table 188.8.131.52 describes the minimum dimensions of conductors connecting internal metal installations to the equipotential bonding rail.
The minimum cross sections are for protection class I to IV:
Copper = 6 mm²
Aluminium = 10 mm²
Steel = 16 mm²
No! The requirements for the use of surge arresters are set out in the technical connection rule VDE-AR-N 4100, Technical Rules for the Connection of Customer Installations to the Low Voltage Grid and their Operation (TAR Low Voltage) as well as the standards DIN VDE 0100-443 and DIN VDE 0100-534 regulated by low-voltage systems.
They are exclusive leak-free overvoltage arresters on spark gap basis allowed. No operating current for instance of LED monitoring will be accepted. The varistor-based Leutron IsoProS arresters do not meet these requirements.
A distinction is made in particular with lightning arresters between spur connection and V-shaped connection.
When stub line connection connects a line e.g. a bus bar system with the arrester connection. The result is T-shaped connection geometry. With this type of connection, the system backup (F1) can be greater than the maximum permissible backup fuse of the arrester (F2). The arrester is additionally protected accordingly in the line pass. With the V-shaped connection, the incoming and outgoing cables are each connected directly to a terminal of the protection device. Possible voltages are kept to a minimum by short cable routing. In this case, however, the system fuse must not exceed the maximum back-up fuse of the arrester. These two connection options are also possible with combined arresters (type 1/type 2) and with arrester type 2.
The plastics used in the arresters comply with the UL94 Classification V0. This means: no burning dripping and extinguishing of the flame within 10 seconds with a maximum afterglow of 30 seconds.
The advantage of the varistor is a short response time. The disadvantage is a high self-capacitance.
The advantage of the suppressor diode is a short response time. The disadvantages are a high self-capacitance and a low current-carrying capacity.
The advantages of the gas discharge tube (GDT) are its low self-capacitance and high current-carrying capacity. The disadvantage is its delayed / slow response.
The IEC test classes have been renamed several times over time. Currently, type 1, formerly class B or rough protection is mentioned. Type 2, formerly class C or medium protection and Type 3, formerly class D or fine protection.
SPD stands for „Surge Protective Devices“
Depending on the network types, different arresters are used. A widespread network form is the TN network. In the TN-C system, the RU (electric power company) transports the potential of the low-voltage source (transformer) through the PEN conductor to the consumer plant. Here, the PE has the same potential as the N conductor. Here, the 3-pole arrester is used. In the TN-S network, PE and N are disconnected. This can lead to a potential shift between PE and N. Here, a 4-pole arrester is used.
In the TT system, SPDs type 1 and type 2 arresters are not operated between the active conductors and the ground potential as in TN systems, but between phases L1, L2 and L3 and the neutral conductor. In the “classical” arrangement of the overvoltage protection devices between the phases and the earth potential, these could no longer be reticulated at the end of their service life, age, or even produce a short circuit. Then, depending on the existing grounding resistance of the consumer system, a fault current flows back to the feeding source. As a rule, due to relatively high loop resistance in TT systems, the operational current fuses will not recognize this fault current as a fault and will not disconnect in time. This can lead to potential increases in the entire equipotential bonding system of the building. If buildings located farther away from this consumer installation are supplied or consumers are operated outside the effective range of the building’s equipotential bonding system via mobile lines, dangerous voltage carry-over can occur. Here the 3 + 1 circuit is used.
In some consumer installations, an IT system is being built for availability. When a single-phase ground fault occurs, a TN system is practically created. The energy supply is not interrupted, but maintained. IT systems can be found, for example, in medical areas. An insulation monitoring device provides information about the quality of the insulation conditions of the active conductors and the connected consumers in relation to the earth potential. SPDs are switched between the active conductors and the main equipotential bonding. Fuse, conductor cross-section and cable routing are handled as with T-systems. In circuit distributors, all active conductors are also protected against the local earth potential. To protect sensitive consumers, type 3 SPDs are used. The arresters must be dimensioned for the outer conductor voltage.
First letter (earth connection of the feeding power source):
T direct earthing of a point (star point)
I either isolate all active parts of the earth or connect a point to earth via impedance.
Second letter (earth connections of the bodies):
T body directly grounded, regardless of the grounding at the power source
N body connected directly to the farm ground
Additional letters (arrangement of the neutral conductor and the protective conductor):
S neutral conductor and protective conductor are separated (separately)
C Neutral conductor and protective conductor are combined in one conductor
Protection against contact with dangerous electrical voltages
Name: IP, 1st digit, 2nd digit
1st digit: touch / foreign body
2nd digit: humidity
Caution: Do not confuse with protection class!
Further information on the protection class is specified in the following publications: DIN EN 60529, IEC Publication 529, and DIN 40050
Meaning Degree of protection 1st digit, contact protection / foreign body protection:
0 no protection
1 Protection against large body parts / foreign bodies Ø 50mm
2 finger protection / medium foreign bodies Ø 12mm
3 Protection against tools, wires from Ø 2.5mm
4 Protection against tools, wires, grain-shaped foreign bodies from Ø 1mm
5 (K) wire protection (like IP4) dust-proof, dust deposit
6 (K) wire protection (like IP4) dustproof, no dust ingress
Meaning Degree of protection 2nd digit, water protection, and protection against:
0 No protection
1 vertically falling water
2 Sloping (up to 15 °) falling water
3 Falling spray water up to 60 ° to vertical
4 All-round splashing water
4k All-side spray under increased pressure (vehicles)
5 jet water (nozzle) from any angle
6 Heavy jet water (flooding)
7 Temporary submersion
8 Continuous submersion
9k water in high-pressure / steam jet cleaning (vehicles)
The inclusion of roof structures in a lightning protection system can basically be realized in different ways.
- By connecting the component to be protected to the lightning protection system, provided it is made of conductive material. It must be distinguished in
a) Direct connection of the metal roof structure
b) Connection of the metal roof structure via separating spark gaps
- By installing a catching device (e.g. catch rod, catching tip …) that brings the component into the protected area. It must be distinguished in:
a) Roof construction in the protected area without separation distance
b) Roof construction in the protected area with separation distance
In point 1a) „direct connection“ occurs in the case of a direct lightning strike high partial flash currents in the building interior, which bring a significant risk potential.
Non-negligible partial flash currents reach in case 2a) „lightning strike in the lightning protection system“ in the building interior and can cause damage there.
The performance of the lightning protection system is represented by the division into lightning protection classes I to IV:
Lightning protection class I = highest protection requirement, e.g. Hospitals, Data Centers…
Lightning protection class II = high protection requirement, e.g. industrial plants or hazardous areas…
Lightning protection class III = low protection requirements, e.g. residential buildings…
Lightning protection class IV = lowest protection requirement
In lightning protection class I and II, lightning current-carrying arresters type 1 or combination arresters type 1+2 or type 1+2+3 with a discharge capacity per pole L-N (10/350 μs) Iimp = 25 kA, N-PE (10/350μs) Iimp = 100 kA, with L+N-PE (10/350 μs) Itotal = 100 kA be used.
For lightning protection class III + IV, arresters with a reduced discharge capacity of 12.5 kA are also permissible in cases 1a) and 2a).
In application 2b), a type 2 surge arrester is sufficient for all lightning protection classes.
Low-voltage fuses are used in the distribution network, in industry and at the end customer, e.g. in the fuse box. The typical rated voltage is 230/400 V AC.
For industrial plants, versions up to 1000 V DC or AC are available. There are different designs (e.g. screw fuses, NH fuses, cylinder fuses), which in turn are produced in different operating classes (tripping characteristics).
Operating classes of low-voltage fuses
The operating class of a low-voltage fuse is expressed by two letters, of which the first character identifies the functional class and the second character identifies the protected object. The functional class of a fuse indicates its ability to carry certain currents without damage and to turn off over current above a range.
There are two functional classes:
g „general purpose fuse“
Full-range fuses, which can continuously carry currents up to at least their rated current, can switch off currents from the smallest melt current to the rated breaking current.
a „protected fuse“, (accompanying fuse)
Partial protection that continuously conducts currents up to at least their rated current, can switch off currents above a certain multiple of their rated current up to the rated breaking current.