ELPA 10515:2 Page 45 9.0 SANS 62305 Part 4 - Protection Of Electrical And Electronic Systems Electrical and electronic systems, which are sensitive to high energy temporary overvoltage resulting from the lightning discharge, are rapidly becoming common in practically all areas of residential and functional buildings in the form of building management, telecommunications, control and security systems. The owner / operator places very high demands on the permanent availability and reliability of such systems. It is therefore necessary to provide adequate protection of these electronic systems. 9.1 Lightning Current Arresters In accordance with IEC 62305 Part2, once the appropriate risk assessments have been completed, the lightning protection designer shall select a lightning protection level that will reduce the calculated risk to within acceptable limits. If a structural lightning protection system is required for the building, then a Type 1 lightning current arrester must be installed at the main distribution panel (i.e. point of entry). Furthermore, the maximum rating of the Type 1 arrester must also be selected based upon the lightning protection level (Table 10). Lightning Protection Assumed Lightning Level (LPL) Fault Current I 200 kA II 150 kA III 100 kA IV 100 kA Table 10 Using the 50% - 50% rule as described in Item 2,8, lightning protection level I and II require the installation of a Type 1 lightning arrester rated to 100kA. Similarly lightning protection level III and IV require the installation of a Type 1 lightning arrester rated to 50kA. 9.2 Lightning Protection Zoning Concept (LPZ) The protection of electrical and electronic systems in structures against surges resulting from the lightning electromagnetic pulse (LEMP) is based on the principle of lightning protection zones (LPZ). According to this principle, the structure to be protected must be divided into inner lightning protection zones according to the risk level posed by the LEMP (Figure 21 ). This allows to adapt areas with different LEMP risk levels to the immunity level of the electronic system. With this flexible concept, suitable LPZs can be defined according to the number, type and sensitivity of the electronic devices / systems ranging from small local zones to large integral zones which can encompass the whole building. Depending on the lightning threat, inner and outer lightning protection zones are defined in SANS 62305-4 standard. Outer Zones: LPZ 0 - Zone where the threat is due to the unattenuated lightning electromagnetic field and where the internal systems may be subjected to the full or partial lightning current. LPZ 0 is subdivided into: LPZ 0A - Zone where the threat is due to direct lightning strikes and the full lightning electromagnetic field. The internal systems may be subjected to the full lightning current. LPZ 0B - Zone protected against direct lightning strikes but where the threat is due to the full lightning electro- magnetic field. The internal systems may be subjected to partial lightning currents.
ELPA 10515:2 Page 46 9.2 Lightning Protection Zoning Concept (LPZ) (Contd.) Inner zones (protected against direct lightning strikes): LPZ 1 - Zone where the impulse currents are limited by current distribution and isolating interfaces and / or by SPDs at the zone boundaries. Spatial shielding may attenuate the lightning electromagnetic field. LPZ 2...n - Zone where the impulse currents are limited by current distribution and isolating interfaces and / or by additional SPDs at the zone boundaries. Additional spatial shielding may be used to further attenuate the lightning electromagnetic field. air-termination system spatial shield terminal device ventilation down- conductor system l.v. power supply system foundation earth electrode IT system steel reinforcement Lightning equipotential bonding Lightning equipotential bonding Lightning electro- Lightning Lightning current arrester (SPD Type 1) Lightning current arrester magnetic pulse protection zone Local equipotential bonding Local equipotential bonding Switching electro- Surge arrester (SPD Type 2, SPD Type 3) Surge arrester magnetic pulse Fig. 24 LPS = Lightning Protection System LEMP = Lightning Electromagnetic Pulse LPZ = Lightning Protection Zone The number of zones is to be determined by the lightning protection designer which is dependant on the type of facility and the sensitivity of the electrical / electronic systems being protected. At the boundary of each zone, the equipotential bonding must be carried out for all metallic components and utility lines entering each zone. This is done by direct connections or with suitable surge protection devices, this equipotential bonding should be carried out as described in Item 8.4. The zone boundary is then formed by these shielding measures (Figure 24 and 25).
ELPA 10515:2 Page 47 9.2 Lightning Protection Zoning Concept (LPZ) (Contd.) LPS Zoning Concept Lightning Protection System LPZ 0 A LPZ 0 B LPZ 1 LPZ 2 LPZ 3 Equipment Sub D/B (Subject to Potential Damage) Main D/B Surge Arrester Surge Arrester Class 3 Class 2 Lightning Current Arrester Class 1 Incoming Supply Lines Fig. 25 In accordance with IEC 62305 Part 4, the principle of Lightning Protection Zones (LPZ) is to be used in the protection of electrical and electronic equipment against lightning electromagnetic pulse (LEMP). The determination of the zones is based upon the type and sensitivity of the electronic devices. 9.3 LEMP vs Induced Surges In order to understand the need for the installation of Class 1 lightning current arresters, we need to understand the difference between a lightning or partial lightning current wavelength and an induced surge current wavelength. A lightning current has a wavelength of 10/350us compared with an induced surge wavelength of 8/20us. This means that a lightning fault current take 10 microseconds to reach its peak (40kA as per figure below) and 350 microseconds to reach half of its intensity. The same applies for the 8/20us induced surge current wavelength. The duration of the fault is therefore far longer for a lightning current and therefore its destructive power is far greater than an induced surge current. We therefore cannot expect surge arresters to be able to handle the destructive power of a lightning fault current, similarly we cannot expect a lightning current arrester to be able to effectively handle both types of surges. Based upon the above a co-ordinated surge protection system is essential (Figure 27). LEMP vs Induced Surges 45 i [kA] 40 35 30 1-LEMP 2-Induced Surge 25 20 15 2 1 10 5 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 t [ms] Fig. 26
ELPA 10515:2 Page 48 9.4 Coordinated Surge Protection System Lightning and surge protection devices are classified according to their loads and function in the surge protection system as Class 1, 2 and 3. The highest discharge capacity is found in Class 1 SPDs (Lightning Current Arresters). These are installed at the boundary of LPZ 0A and LPZ 1 (as shown above). These protective devices must be capable of carrying partial lightning currents, waveform 10/350us, many times without consequential damage to equipment. Their function is to prevent destructive partial lightning currents from penetrating the electrical installation of a structure. At the boundaries of LPZ 0B to LPZ 1 and higher, or LPZ 1 to LPZ 2 and higher Class 2 SPDs are employed to protect electrical systems from induced surges, waveform 8/20us, without causing damage to more sensitive electrical devices. The last link in the co-ordinated surge protection system is for the protection of terminal devices. At the boundary of LPZ 2 to LPZ 3 and higher Class 3 SPDs are installed to protect the most sensitive electrical devices from primarily switching surges. Energy co-ordination of the surge protection system is absolutely essential to ensure that the selective functioning of the various SPDs at each LPZ boundary is in place. At each protective stage only the amount of interference energy for which that SPD is designed may be present. All higher interference energies must protected by the upstream SPD, e.g. Class 1 SPDs, must take over the discharge of the impulse current and relieve the downstream SPDs. The energy co-ordination of the surge protection system is as per the requirements of SANS / IEC 62305 Part 4. In cases where sensitive electronic equipment is installed in the main distribution board; then a combination Class 1 + 2 SPD is recommended (Figure 24). Coordinated Surge Protection System possible threat potential ~10…100 kV rated impulse withstand sensitive devices can be installed closer to the meter voltage (“Smart Grid“, electronic household meter, heating control, …) 6 kV voltage protection 1.5 kV sensitive devices level £ 1.5 kV terminal SE M SDB device 230/400 V type 1 type 2 type 3 type 3 10/350 8/20 8/20 Fig. 27
ELPA 10515:2 Page 49 9.5 Selection of Surge Protection Devices (Power Supply) In accordance with SANS / IEC 62305 Part 4, the zoning concept for power supply systems and the installation of the associated lightning and surge protection devices is an indispensable component of the trouble free operation of a structure`s complex electrical and electronic systems (Figure 25). SPDs that are employed as part of a structure`s fixed installation are classified as follows : - LPZ 0A to LPZ 1 - Class 1 (Lightning Arresters) - LPZ 0B to LPZ 1 - Class 2 (Surge Arresters) - LPZ 1 to LPZ 2 - Class 2 (Surge Arresters) - LPZ 2 to LPZ 3 and above - Class 3 (Surge Arresters) The appropriate lightning and surge arresters should be selected based upon the following : - Type of electrical supply (TNC, TNS or TT) - Lightning Protection Level (I, II, III or IV) - Nominal Voltage and AC or DC Surge Protection for Power Supplies main distribution board subdistribution board terminal equipment lightning current arrester surge arrester F1 meter L1 L2 Wh L3 PEN SEB N PE external lightning protection system F2 F3 MEBB local EBB Fig. 28 9.6 Surge Protection for IT Systems The surge protection principles for IT and other data type systems is the same as for the power supply systems. It is recommended to apply the concept of protective devices with several protective stages. This reduces the high energy interference (partial lightning currents) in stages because the initial energy absorbing stage prevents the main part of the interference from reaching the downstream system. The relevant interface where the protective devices are installed are at the lightning protection zone boundaries. This forms part of the lightning protection zone concept which conforms with the requirements of SANS / IEC 62305 Part 4 (Figure 30).
ELPA 10515:2 Page 50 9.6 Surge Protection For IT Systems (Contd.) Co-ordination According To Let-through Method Of 2 Spds And One Terminal Device I P1 I IN2 I P2 I IN ITE U IN Surge immunity against impulse voltages Surge immunity against I SPD 1 SPD 2 U IN ITE ITE IN impulse currents U P1 U IN2 U P2 U P Voltage protection level impulse voltage I P Let-through impulse current Fig. 29 Depending on the conditions of the installation, several protective stages can also be integrated into one surge protective device using a combined protective circuit. Although the LPZ principles for power supplies and data systems are the same, the naming of the data SPDs is slightly different as follows : - Class 1 (power supply) = Type 1 (data systems) - Rated 2.5kA (10/350us) - Class 2 (power supply) = Type 2 (data systems) - Rated 2.5kA (8/20us) - Class 3 (power supply) = Type 3 (data systems) - Rated 0.25kA (8/20us) - Figure 27. Surge Protection for IT Systems Use Of Combined Lightning Current And Surge Arrester Cascaded Use Of Spds Lightning current TYPE 2 P1 TYPE 2 P1 TYPE 2 P1 Fig. 30
ELPA 10515:2 Page 51 59.7 Spacial Shielding The further protection of critical lightning protection zones equipped with sensitive electronic / electrical equipment can be achieved by means of ‘Spacial Shielding’ against magnetic fields caused by lightning. Depending on the type of facility being protected, the spacial shielding can either shield the entire structure or strategic areas like computer / server rooms, control rooms and security rooms. Spacial shielding is achieved by installing conductive (metallic) meshes to the walls, roofs and floors of structures or rooms. The meshes are normally made of galvanised steel meshes with a mesh apature not exceeding 400mm but the mesh sizes can be as small as 50mm depending on the type of environment being protected. The shielding meshes are normally installed during the construction of the structure but they can also be retrofitted. All equipotential bonding as per the lightning protection zoning concept shall be installed at the points of entry and within the shielded area. Lightning currents and the associated electromagnetic field represent the primary source of interference for devices and installations requiring protection in an object. Figure 28 shows the principle of how grid structures work. The calculation bases, which are described in SANS / IEC 62305-4 standard, are based on assumptions and assessments. The complex distribution of the magnetic field inside grid-like shields is determined in a first approximation. The formulas for determining the magnetic field are based on numerical calculations of the magnetic field. The calculation takes into account the magnetic field coupling of each rod in the grid-like shield with all other rods including the simulated lightning channel. Reduction of the magnetic ield by means of grid-like shields / High field strength, large magnetic fields / Lower partial currents, reduced magnetic fields induction voltages close to the down conductor induction voltages in the building i o w w i d r d r d w H 2 d w W H 1k i m [A/m ] i = lightning current in LPZ 0 A o h O d d W r Magnetic ield in case of a direct lightning strike in Magnetic field strength in case of a direct LPZ 1 (LEMP), SANS / IEC 62305-4 lightning strike in LPZ 2 Fig. 31
ELPA 10515:2 Page 52 10.0 ELPA Lightning Protection Safety Report LIGHTNING PROTECTION SYSTEM INSTALLATION SAFETY REPORT (as per SANS 10313:2012 Edition 3.2) 1-PROJECT DETAILS Physical address: Province, Country: ELPA No. Postal Code Unit / Building No.: Issue Date Customer / Owner details: Company name: Expity Date 2-GENERAL Protected space (details): Type of Certification: Acceptance Re-certification Type of Inspection: Visual Testing Additional 2 Lightning ground flash density (N G ) (Flashes/km /year): Accepted annual lightning flashes to structure (N D ): 3-RISK ASSESSMENT Has a risk assessment been done for system? Yes No Is the risk assessment report attached? Yes No Calculated Risk Are the calculated Calculated Risk with User-specified acceptable risks (R T ) R x risks acceptable? Protection R x Loss of human life R 1 1.00E-05 Yes No User-calculated Loss of services 1.00E-03 Yes No R 2 risks R X Tolerance on risk R T Loss of cultural heritage R 3 1.00E-04 Yes No Loss of economic value 1.00E-03 Yes No R 4 Lightning Protection System (LPS) level: LPL 1 LPL 2 LPL 3 LPL 4 Risk mitigation Lightning Equipotential Bonding (LEB) level: LPL 1 LPL 2 LPL 3 LPL 4 methods required Coordinated surge protection device (SPD) level: LPL 1 LPL 2 LPL 3 LPL 4 4-LIGHTNING PROTECTION SYSTEM (LPS) Has the LPS design been done in accordance with SANS 62305:2011 Yes No Is the LPS design drawing attached? Yes No Are all LPS components tested and certified in accordance with SANS Are the test certificates of these components Yes No Yes No 62561:2012 attached? 5-AIR-TERMINATION SYSTEM (ATS) Thatched roof: Yes No Roof used as ATS: Yes No Hazardous location: Yes No External conductors installed: Yes No Type of roof/striucture: Type of ATS used: Metal roof: Yes No Free-standing masts: Yes No Other: Yes No Isolated ATS: Yes No 2 Protective angle (ᶿ): Yes No Details: ATS size and or detail (mm ) Rolling sphere radius (m): Yes No Details: HVI Steel(St/tZn,StSt) ATS method used: Mesh method (grid): Yes No Details: ATS material used: Copper (Cu) Aluminium (Al) Hybrid (mix of methods) Yes No Details: Zinc (Zn) Other Overall Comments: 6-DOWN CONDUCTOR SYSTEM (DCS) 2 Natural conductive element used as DCS Yes No DCS size and or detail (mm ) Reinforcement used as DCS: Yes No Spacing between down conductors (m): Type of DCS used: External DCS used: Yes No Number of down conductors in the system: Existing structure used as DCS: Yes No Accessible test joints/terminations: Yes No DCS material used: HVI Steel (St/tZn, StSt) Copper (Cu) Aluminium (Al) Zinc (Zn) Other Overall Comments: NOTES: The following codes have been referenced in this report SANS 10142, SANS 10199, SANS 10313, SANS 60364, SANS 62305, SANS 62561 Page 1 of 2
ELPA 10515:2 Page 53 LIGHTNING PROTECTION SYSTEM INSTALLATION SAFETY REPORT (as per SANS 10313:2012 Edition 3.2) 7-EARTH-TERMINATION SYSTEM (ETS) Has a soil resistivity test been done for the site? Yes No Is the existing ETS used? Yes No Is the soil resistivity test report attached? Yes No If a new ETS was designed, is the ETS design attached? Yes No Top layer soil resistivity (p1) Type A Type of earthing arrangement: Bottom layer soil resistivity Type B (p2) Soil resistivity test results: Reflection Factor (k) Final earth resistance (Ω): Depth of top layer (h) Final reading acceptable: Yes No Copper (Cu) Steel (St/tZn,StSt) Particular soil conditions: Material used for the ETS: Zinc (Zn) Other Reason for ETS arrangement: Overall Comments: 8-LIGHTNING EQUIPOTENTIAL BONDING (LEB) Is the LPS bonded to the building earthing system? Yes No Copper (Cu) Steel (St/tZn,StSt) Material of bonding bar: Is an equipotential bonding bar installed? Yes No Zinc (Zn) Other 2 Communication Pipes Conductor size to connect bonding bar to ETS (mm ): System connected to bonding 2 Electrical Equipment Equipment Conductor size to connect metal installation to ETS (mm ): bar: IT Equipment Other Is the bonding bar labelled? Yes No Overall Comments: 9-SURGE PROTECTIVE DEVICES (SPD) Are new SPDs installed? Yes No Are the existing/new SPDs tested and certified in accordance with SANS 61634 60643: 2011 Yes No Are the SPDs pre-fused? Yes No Main distribution board current rating(A) Prospective Short-circuit current (I sc ) rating (kA) Type 1 Impulse current I imp (kA, 10/350µs): Voltage protection level at I imp (kV) Type of SPD installed Type 2 Impulse current I n (kA, 8/20µs): Voltage protection level at I n (kV) Overall Comments: 10-CERTIFICATION I/We, being the person(s) responsible for the design, installation, inspection, testing, of the lightning protection system (LPS), am/are competent to certify that the LPS complies with the requirements of SANS 10142, 62305 & 10313 10.1-DETAILS OF LPS DESIGNER Name: Tel No.: ELPA No. ID No.: Signature: Date: cc yy mm dd 10.2DETAILS OF LPS INSTALLER Name: Tel No.: ELPA No. ID No.: Signature: Date: cc yy mm dd 10.3DETAILS OF FIXED ELECTRICAL INSTALLATION Type of electrical installation New Existing Has a new/updated COC been issued? Yes No COC Doc No. Any work performed on the electrical installation with regard to the LPS shall be witnessed by an accredited person and a new electrical Notes: COC may be issued in accordance with SANS10142:1. 10.4 APPROVAL SIGNATURE (LPS INSPECTOR) Name: Tel No.: ELPA No. ID No.: Signature: Date: cc yy mm dd Overall Comments: NOTES: The following codes have been referenced in this report SANS 10142, SANS 10199, SANS 10313, SANS 60364, SANS 62305, SANS 62561 Page 2 of 2
ELPA 10515:2 Page 54 11.0 Rights We reserve the to make changes in design, technology, dimensions, weights and materials in the course of technical progress. Illustrations are not binding. We accept no liability for misprints, modifications or errors. Reproduction, even in extracts, is only permitted with prior consent. This Handbook is a guide and is not specific to a manufacturer, products, methods of installation or design. 12.0 Reference - SANS 62305 Part 1 - Protection against lightning - General principles - SANS 62305 Part 2 - Protection against lightning - Risk Management - SANS 62305 Part 3 -Protection against lightning - Physical damage to structures and life hazard - SANS 62305 Part 4 - Protection against lightning - Electrical and electronic equipment within structures - SANS 10313:2012 - Protection against lightning - Physical damage to structures and life hazard - SANS 10199 : 2010 - The design and installation of earth electrodes - SANS 62561 Series of Standards (Edition 1) - Lightning protection system components - SANS 10142-1 - The wiring of premises : part 1 low voltage installations - DEHN Lightning Protection Guide - 3rd Edition
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