LPS Designer Handbook

Designer Handbook LIGHTNING PROTECTION SYSTEMS PREPARED BY : LPC REFERENCE : D001-DESIGN-001 ISSUE : A DATE : 30 January 2018



ELPA 10515:2 ELPA NATIONAL STANDARD - 10515:2 Designers Guide to the Design of Lightning Protection Systems WARNING - Can only be used in conjunction with the SANS 62305 series of standards

ELPA 10515:2 Design Principles for Lightning 3D Modelling for Protection Systems Contents Earthing & Lightning Protection Designs 1.0 Forward 2.0 Scope 3.0 Normative References 4.0 Definitions 5.0 Component Compliance 6.0 Complete Lightning Protection System 6.1 External LPS 6.2 Internal LPS 6.3 Complete LPS 6.4 Assumed Distribution of a Lightning Current 7.0 SANS 62305 Part 2 - Risk Management 7.1 Planning 7.1.1 Risk Management & Assessment of the Building 7.1.2 Risks to be Considered 7.2 Risk Components 7.3 Assessment & Reduction of Risks 7.2.1 Risk Composition 7.4 Calculated Risk vs Tolerable Risk 7.5 Lightning Protection Level Selection 7.5.1 Lightning Protection Levels 7.6 Risk Assessment Software 7.7 Correct Interpretation of Results 8.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.1 Air Termination Systems 8.1.1 Types of Air Terminals 8.1.2 Air Termination Protection Methods 8.1.3 Rolling Sphere Method 8.1.3.1 Final Strike Zone 8.1.3.2 Level of LPS and Radius of Rolling Sphere 8.1.3.3 Rolling Sphere Applications 8.1.3.4 Calculation of Rolling Sphere Sag 8.1.4 Angle of Protection 8.1.4.1 Determination of Angle of Protection 8.1.5 Mesh Method of Protection 8.1.6 Combination of Air Terminals 8.1.7 Tall Structures 8.1.8 Natural Air Terminals 8.2 Down Conductor System 8.2.1 Determination of the Number of Down Conductors 8.2.2 Installation of Down Conductors 8.2.3 Down Conductor Materials & Sizes 8.2.4 Natural Down Conductors 8.2.5 External Down Conductors 8.2.6 Test Points 8.2.7 Courtyards 8.2.8 Earth Entry Points 8.3 Earth Termination Systems 8.3.1 Type A Earth Electrodes 8.3.2 Type B earth Electrodes 8.3.3 Integrated Earth Electrodes

ELPA 10515:2 Design Principles for Lightning 3D Modelling for Protection Systems Earthing & Lightning Protection Designs Contents 4.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.4 Lightning Equipotential Bonding 8.4.1 Equipotential Bonding of Pipes 8.4.2 Minimum Cross Sectional Size of Bonding Conductors 8.4.3 Equipotential Bonding of Electrical Supply Lines 8.4.4 Equipotential Bonding of Cable Armouring 8.4.5 Equipotential Bonding of IT Systems 8.4.6 Bonding of Other Conductive Elements 8.4.7 Equipotential Bonding in Large Structures 8.4.8 Equipotential Bonding of External Conductive Elements 8.4 Separation Distance Concept 8.5.1 Separation Distance for Down Conductors 8.5.2 Separation Distance Calculation (Simplified Method) 8.5.3 Separation Distance Calculation for Multiple Down Conductors 8.5.4 Separation Distance Calculation Detailed Method 8.5.5 Separation Distances for Air Terminals 8.5.6 Design and Functional of HVRI Conductors 8.5.7 Separation Distance for Rooftop Plant 8.6 Step and Touch Potentials- LPS 8.6.1 Protection Against Touch Voltages 8.6.2 Protection Against Step Voltages 8.6.3 Natural Protection Measures 9.0 SANS 62305 Part 4 - Protection of Electrical and Electronic Systems 9.1 Lightning Current Arresters 9.2 Lightning Protection Zoning Concept (LPZ) 9.3 LEMP vs Induced Surges 9.4 Co-ordinated Surge Protection System 9.5 Selection of Surge Protection Devices (Power Supply) 9.6 Surge Protection for IT Systems 9.7 Spacial Shielding 10.0 ELPA LPS Installation Safety Report 11.0 Rights 12.0 Reference

ELPA 10515:2 Page 1 1.0 Forward This ELPA Document was approved by the Technical Committee of ELPA. The intention of this document is to create a uniform interpretation of the SANS 62305 series of documents. This cannot be used without the SANS 62305 series of documents. The components and assemblies shown in this document represent typical installation details. Similar installation details using compliant components are acceptable. 2.0 Scope This document is a standard guideline for the design of a lightning protection system. The Scope of all parts of SANS 62305 apply. 3.0 Normative References The following documents are indispensable for the application of this document. For dated references, only the edition cited applies. For updated references, the latest edition of the referenced document (including any amendments) applies. - SANS 62305 series of standards - SANS 10313: 2012 - SANS 10199: 2010 - SANS 52561 series of standards 4.0 Definitions For the purpose of this document, the definitions given in SANS 62305-12 series of standards apply. The following definitions are applicable to this handbook: ELPA Accredited Person Person who is a member of ELPA and has passed the relevant accreditation examinations ELPA Accredited LPS Installer Person who is competent to install, construct and test the LPS for compliance with the SANS standards. Further to this, the person is a member of ELPA and has passed the required examinations for the ELPA installer accreditation. The ELPA accredited LPS installer does NOT have the authority to approve the safety report of an installation. ELPA Accredited LPS Designer Person who is competent to design, construct and test the LPS for compliance with the SANS standards. Further to this, the person is a member of ELPA and has passed the required examinations for the ELPA designer accreditation. The ELPA accredited LPS designer has the authority to approve the safety report of an installation. ELPA accredited LPS inspector Person who is competent to install, construct and test the LPS for compliance with the SANS standards. Further to this, the person is a member of ELPA and has passed the required examinations for the ELPA inspector accreditation. The ELPA accredited LPS inspector has the authority to approve the safety report of an installation as well as conduct and or approve an inspection report of an LPS. Installation Safety Report Report that is issued by a lightning protection system designer or installer in respect of an LPS that complies with the relevant requirements of the SANS standards. The approval of the safety report shall be done by either an ELPA accredited designer or inspector. S

ELPA 10515:2 Page 2 5.0 Coomponent Compliance The following standards forms the basis for this document: - SANS 62305-12 series of standards - SANS 62561-13 series of standards - SANS 10313 : 2012 The above standards provide the design principles for effective lightning protection solutions. If however the components used for the subsequent LPS installation are unable to withstand both the electrical as well as the mechanical stresses of a lightning strike then the LPS could cause a life hazard to people or damage to the structure or its contents. It is therefore vitally important that correct components be specified as part of the LPS design. The SANS standards for the various lightning protection components are contained within the SANS 62561 series of standards SANS 62561 SANS 62305 Lightning Protection Components (LPC) Protection against lightning Part 1:Requirements for connection compo- nents Part 1:General principles Part 2:Requirements for conductors and earth electrodes Part 2:Risk management Part 3:Requirements for isolating spark gaps Part 3:Physical damage to structures and life hazard Part 4:Requirements for conductor fasteners Part 4:Electrical and electronic systems within structures Part 5:Requirements for earth electrode in - spec tion housings and earth electrode seals Manufacturer’s Test Report The SANS 62305 and SANS 62561 series of standards are based upon the IEC series of lightning protection standards. Test according to EN 50164-1 In order to comply with the SANS 62305 series, all of the LPS MV Clamp Part No. 390 059 components must be tested and certified in accordance with Material: StSt the SANS 62561 series of standards. Application: above ground Connected conductor Test result Conductor (1): Rd 8 St/tZn N Conductor (2): Rd 8 St/tZn Conductor (1): Rd 8 Cu H Conductor (2): Rd 8 Cu Conductor (1): Rd 8 StSt H Conductor (2): Rd 8 StSt Conductor (1): Rd 8 Al H Conductor (2): Rd 8 Al Legend Lightning current carrying capability class H 100 kA (10/350 μs) Lightning current carrying capability class N 50 kA (10/350 μs) More details on the test conditions are available on request.

ELPA 10515:2 Page 3 6.0 Complete Lightning Protection System (LPS) The function of a LPS is to protect structures from fire or physical damage and people from injury or death. A lightning protection system consists of an internal and external system (fig.1). The function of the external system is to intercept the lightning, conduct it to ground and then dissipate the energy. The function of the internal system is to prevent dangerous sparking inside the building. The requirements for both of these systems shall be established by conducting a Risk Assessment in terms of SANS 62305-2. In order to provide complete lightning protection systems all protection elements must be installed to the structure. Lightning Protection System as per SANS / IEC 62305-3 Air Termination System Down Conductor System Earth Termination System Equipotential Bonding Separation Distances External Protection System Internal Protection System Fig. 1 6.1 External LPS The required level of protection (LPL I, II, III or IV) for the External Protection System shall be determined through the Risk Assessment which shall be conducted in terms of SANS 62305-2. Once the LPL is established the parameters for the external protection system are selected i.e. conductor sizes, down conductor spacing, rolling sphere radius, mesh size, protective angle etc. - Air Termination System (ATS) The function of the ATS is to prevent any direct lightning strikes from damaging the structure by intercepting the lightning strike, preventing penetration into the protected space. A correctly designed system will significantly reduce the risk of a direct strike to the structure. It is not possible to completely eliminate this risk. An ATS can consist of the following components: - Masts - Spanned wires and cables - Conductors in conductor holders It is important that the ATS covers corners and edges of a structure as these areas are most vulnerable to a direct strike. It is also important that any masts used are able to withstand the wind loading for the area in which it is installed. LPS - Lightning Protection System

ELPA 10515:2 Page 4 6.1 External LPS (Contd.) - Down Conductor System (DCS) The function of the DCS is to safely conduct the lightning current from the ATS to the ETS without damaging the building. The important aspects of a DCS are: - Several parallel current paths ie the more DCS the better - The length of the DCS must be as short as possible (straight, vertical, no loops) - Connections to conductive parts of the structure are made wherever possible The maximum spacing between the down conductors is dependent on the Lightning Protection Level (LPL). The number of down conductors will also depend on the geometry (perimeter) of the structure. The down conductors should be placed such that there is a down conductor at each corner of the structure. The down conductors should then be spaced evenly around the perimeter in accordance with the LPL. In the case of an isolated LPS the number and position of the DCS can vary significantly more than the above method. - Earth Termination System (ETS) The earth termination system is designed to safely dissipate the lightning current (lightning protection systems) or fault current safely into the ground. The design of the Lightning Protection ETS is different to that of Power Frequency ETS, this is mainly due to the high impulse (dynamic) characteristic of Lightning. Components of an External LPS An External Lightning Protection System Consists of: 1 1 Air Termination System 2 Down Conductor System 2 3 Earth Termination System 3 1 2 3

ELPA 10515:2 Page 5 6.2 Internal LPS Sensitive electrical and electronic systems are becoming common place in modern buildings. These systems can be safety critical and therefore require permanent availability and reliability. A few examples are security systems, fire detection systems, life support systems in hospitals, telecommunications, building management systems etc. These systems are also sensitive to temporary over voltages (surges) which are caused by both lightning discharge and switching operations on the electricity supply. Internal LPSs consist of the following protection methods: - Equipotential Bonding (EB) Lightning equipotential bonding is the connection of all conductive elements of the building to the LPS and is carried out to prevent dangerous sparking inside the structure. The typical conductive elements of a building are metal pipes (water, air conditioning etc), gas pipes, steel structures, lift mechanisms, ducts etc. The connection of these systems to the LPS is done to prevent potential differences which can result in hazardous touch potentials as well as damage to electrical / electronic systems. - Separation Distance (’S’) Roof mounted structures such as HVAC, telecommunication masts and CCTV camera systems present a high risk of introducing lightning currents to the inside of the building. This risk can result in the damage of equipment and loss of human life. In order to reduce this risk the roof mounted structures should be protected by an Isolated LPS. An Isolated LPS ensures that all conductors of the LPS are separated from any other conductive elements by the calculated separation distance. Components of an Internal LPS LPS - Lightning Protection System Function of an Internal LPS Prevention of dangerous sparking in the structure by establishing equipotential bonding or keeping a separation distance between the components of the lightning protection system and other conductive elements in the structure.

ELPA 10515:2 Page 6 6.3 Complete Lightning Protection System The complete lightning protection system consist of both the internal LPS and the external LPS. The design and installation of an external LPS only does not constitute a complete LPS. 6.4 Assumed Distribution of a Lightning Current - 50% - 50% Rule The assumed distribution of a lightning current is 50% via the LPS and 50% via other conductive elements of the structure. The anticipated lightning fault current is dependent on the selected Lightning protection level. Assumed Distribution of a Lightning Strike 100% Air Termination Equipotential Earth Bar External Lightning I.T. Network Protection Power Supply System 50% Metal Pipes 50% Earthing System

ELPA 10515:2 Page 7 7.0 SANS 62305 Part 2 - Risk Management In order to evaluate whether or not lightning protection is needed, a risk assessment in accordance with the procedures in IEC 62305 Part 2 shall be made. In other words; a risk assessment must be performed for each and every structure under consideration for lightning protection. Are risk assessments necessary Yes, the analysis of the risk of damage due to lightning is essential for the following reasons : - To comply with the requirements of SANS / IEC 62305 part 2 and - All design parameters including air terminals, down conductor spacings, earth electrode lengths, equipotential bonding, separation distances and surge / lightning arrester sizes are dependant on the lightning protection level which is derived from the risk assessments. 7.1 Planning When planning lightning protection systems, various parameters must be taken into account, such as the building dimensions, electrical equipment, risk classes and financial aspects . 7.1.1 Risk Management and Assessment of the Building A risk analysis is performed to assess the potential risk for a building. Based on this analysis, measures can be taken to reduce the risk. The aim is to select economically sound protection measures which are perfectly adapted to the building’s properties and type of use. A risk analysis does not only allow to determine the class of LPS, but also to develop a complete protection concept of LPS, including the necessary LEMP protection measures. The aim of a risk analysis is to reduce the existing risk to a tolerable risk RT. Therefore, the tolerable risk RT is defined when selecting the risks. These tolerable risks are specified in the standard, however, responsible authorities having jurisdiction may define them in another way. 7.1.2 Risks to be Considered At the beginning of a risk analysis, the type of building use is required to determine the risks to be considered for the object requiring protection. When performing a risk analysis, four different risks are distinguished: • Risk R1: Risk of loss of human life Risk R1: - Risk of loss of Risk R2 - Risk of loss of human life services to the public • Risk R2: Risk of loss of services to the public • Risk R 3 Risk of loss of cultural heritage: • Risk R4: Risk of loss of economic value One or more risks can be relevant. The lightning protection designer must decide which risks to select. Risk R3: - Risk of loss of Risk R4 - Risk of loss of cultural heritage economic value

ELPA 10515:2 Page 8 7.2 Risk Components Environmen- Urban environment: C= 0.01 tal factor Urban environment (buildings < 20.0 m) : C= 0.1 e e Suburban environment (e.g. in the outskirts): C= 0.5 C Rural environment (e.g. small village) : C =1 e e e Each risk component consists of different factors RX = NX X PX X LX These factors are defined as follows : NX = Number of dangerous events per annum PX = Probability of damage to the structure LX = Consequential loss Frequency of dangerous events NX A variety of parameters are required to calculate the frequency of dangerous events NX, for example : - Lightning ground flash density NG - Collection area AD - Location factor CD - Environmental factor CE - Etc. Probability of damage PX The probability PX describes the building and installation properties of the structure. The properties can reduce or increase the risk. Particularly the risk of fire, which defines the specific fire load of the structure. Risk of explosion, classified areas and the number of occupants can also play an important role when performing the risk analysis. Loss LX In addition to the frequency of dangerous events and the probabilities of damage, possible loss must also be calculated.Losses are differentiated according to the risks considered in the risk analysis and thus according to the risk components. The following losses can be determined : L1 Loss of human life L2 Loss of service to the public -Touch and step voltage - Fire - Fire - Overvoltage / LEMP - Overvoltage / LEMP L3 Loss of cultural heritage L4 Loss of economic value - Fire - Touch and step voltage - Fire - Overvoltage / LEMP

ELPA 10515:2 Page 9 7.3 Assessment and Reduction of Risks R Z Flashes... ... near a line R S R A W 4 ... to a ... to a line structure R Risk R R V B X S S 3 1 R S R C U ... near a 2 structure R M 7.3.1 Risk Composition When performing a risk analysis, it is necessary to not only consider risks R1 to R4, but it is even more important to to consider the composition of the total risk since each risk consists of various individual risk components. Subdivision of the risk components according to the source of damage The sources of damage form the basis for the subdivision of the risk components. The SANS / IEC 62305-2 standard describes the different types of lightning effects as sources of damage as follows : - Flashes to a structure - Flashes near a structure - Flashes to a line or service connected to the structure - Flashes near a line or service connected to the structure Source of damage S1: Flashes to a structure RA = Step and touch voltage inside and outside the structure RB = Fire RC = Overvoltage / LEMP Source of damage S2: Flashes near a structure RM = Overvoltage / LEMP Source of damage S3: Flashes to a line RU = Touch voltage inside the structure RV = Fire RW = Overvoltage Source of damage S4: Flashes near a line RZ = Overvoltage Therefore the risk for RA, RB, RC, RM, RW, RV, RU and RZ must be calculated.

ELPA 10515:2 Page 10 7.4 Calculated Risk vs Tolerable Risk Once the calculated risk RX has been determined taking into account all of the risk and loss factors, then the calculated risk RX is compared to the tolerable risk RT. If RX is greater than or equal to RT, then lightning protection is required. if RX > RT then protection measures are required. Value of RT (as per SANS / IEC 62305-2) The values shown below are as per the SANS / IEC 62305-2 standard and are to be used unless the responsible authorities having jurisdiction over the structure define the tolerable risks in another way. Type of Loss RT (y ) -1 -5 Loss of Human Life 10 -3 Loss of services to the public 10 -4 Loss of cultural heritage 10 7.5 Lightning Protection Level Selection Once the need for a LPS has been determined, then the most suitable protection measures shall be selected by the lightning protection designer according to the share of risk of each risk component in the total calculated risk RX. The lightning protection designer should recalculate the total calculated risk RX, taking into account the appropriate lightning protection level and critical risk components until RX < RT. Each risk analysis could therefore consist of two or more risk assessments. 7.5.1 Lightning Protection Levels There are four lightning protection levels; level 1 being the highest level of protection and level 4 being the lowest level of protection. Each lightning protection level has its own characteristics for the following lightning protection components: - Air termination system parameters - Typical distance between down conductors - Minimum length of earth electrodes - Separation distances against dangerous sparking - Size and placement of lightning current and surge arresters Class of LPS Lightning Protection Assumed Max Lightning Level (LPL) Fault Current I I 200 kA II II 150 kA III III 100 kA IV IV 100 kA

ELPA 10515:2 Page 11 7.6 Risk Assessment Software The calculation of the total risk RX and the selection of the correct lightning protection level is a complex process which should only be undertaken by a lightning protection specialist who has the necessary experience and expertise to correctly interpret the structure and the results obtained. LPC utilises the DEHN Risk Tool software to assist us in delivering the correct results. 3.7 Correct Interpretation Of Results The DEHN software allows each risk to be considered is displayed in a different colour. Blue stands for the tolerable risk, red or green for the risk calculated for the structure to be protected. Without measures With measures RT RT R1 25238 % R1 61 % 2,52E-03 1E-5 6,14E-06 1E-5 - Determination Of The Potential Risks The risk components describe the potential risks for a structure. Therefore, the risk components must be considered in detail when performing a risk analysis. The aim of a risk analysis is to reduce the main risks by taking reasonable measures. - Selection Of Measures n The Dehn Risk Tool Measures can be defined with the help of a selection matrix. These measures are displayed according to the risk components selected. - Cost-effectiveness Of Protection Measures Building owners are often faced with the question, which damage can occur as a result of lightning effects and how the high costs for protection measures should be with regard to the value of the building. Therefore, economic aspects are an important decision criterion. The risk analysis as per SANS / IEC 62305-2 is integrated in the DEHN Risk Tool software.

ELPA 10515:2 Page 12 8.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.1 Air Termination Systems A properly designed air termination system is designed to prevent penetration of a lightning strike into the protected space. The design of the air termination system depends on the selected lightning protection level derived from the lightning protection risk assessment. The air termination system should be designed by an accredited lightning protection designer, LPS installers must by competent enough to install the air termination system in accordance with the LPS design drawings. 8.1.1 Types of Air Terminals Air termination systems are made up of different types of air terminals as follows: - Meshed Conductors - Finials - Masts - Catenary Wires Individual air terminals should be connected together at roof level to increase current division. 8.1.2 Air Termination Protection Methods The design of the air termination system uses three methods of protection: - Rolling Sphere Method - Angle of Protection Method - Mesh Method Combination of ATS Protection Methods mesh size M air-termination rod down conductor protective angle h 2 α rolling sphere r h 1 earth-termination system

ELPA 10515:2 Page 13 8.1.3 Rolling Sphere Method 8.1.3.1 Final Strike Distance For cloud-to-earth flashes, a downward leader grows step by step in a series of jerks from the cloud towards the earth. When the downward leader has got close to the earth within a few tens, to a few hundreds of metres, the electrical insulation strength of the air near the ground is exceeded. A further “leader” discharge similar to the downward leader begins to grow towards the head of the downward leader - the upward leader. This defines the point of strike of the lightning strike. The starting point of the upward leader and hence the subsequent point of strike is determined mainly by the head of the downward leader. The head of the downward leader can only approach the earth within a certain distance. This distance is defined by the continuously increasing electrical field strength of the ground as the head of the downward leader approaches. The smallest distance between the head of the downward leader and the starting point of the upward leader is called the final striking distance hB (corresponds to the radius of the rolling sphere). Immediately after the electrical insulation strength is exceeded at one point, the upward leader, which leads to the final strike and manages to cross the final striking distance, is formed. This is based on the hypothesis that the head of the downward leader approaches the objects on the ground, unaffected by anything, until it reaches the final striking distance. The point of strike is then determined by the object closest to the head of the downward leader. The upward leader starting from this point “forces its way through”. Starting Upward Leader Defining The Point Of Strike 8.1.3.2 Level of LPS and Radius of Rolling Sphere There is a proportionality between the peak value of the lightning current and the electrical charge stored in the downward leader. Furthermore, the electrical field strength of the ground as the downward leader approaches is also linearly dependent on the charge stored in the downward leader. Therefore there is a proportionality between the peak value I of the lightning current and the final striking distance hB (= radius of the rolling sphere): 0.65 r = 10 X I Where r = Radius in m and l = Peak value of minimum lightning current (as per lightning protection level)

ELPA 10515:2 Page 14 8.1.3.2 Level of LPS and Radius of Rolling Sphere (Contd.) SANS 62305 differentiates between four classes of LPS. Level of LPS I provides the most protection and a level of LPS IV, by comparison, the least. The interception effectiveness Ei of the air termination systems is directly related to the level of LPS, i.e. which percentage of the prospective lightning strikes is safely controlled by the air-termination systems. From this, the final striking distance and the radius of the rolling sphere is obtained. The relationships between lightning protection level of the LPS, interception effectiveness of the air-termination systems, final striking distance / radius of the rolling sphere and the minimum peak current value are shown in Table 1. Relation Between Interception Probability and the Final Striking Distance Table 1 Taking into account that the head of the downward leader approaches the objects on the earth in an arbitrary way, unaffected by anything, until it reaches the final striking distance, a method of protection can be determined which allows the volume to be protected of any arrangement of objects to be protected. A true-to-scale sphere with a radius corresponding to the final striking distance (depending on the class of LPS, the radius r of the rolling sphere must correspond true-to-scale to the radii 20, 30, 45 or 60 m) is required for the class of LPS. The centre of the rolling sphere used corresponds to the head of the downward leader towards which the respective upward leaders will approach. The rolling sphere is now rolled around the building under examination and the contact points which represent potential points of strike are marked in each case. The rolling sphere is then rolled over the object in all directions. All contact points are marked again. All possible points of strike are thus shown on the model; it is also possible to determine the areas which can be hit by side flashes. The naturally protected volumes resulting from the geometry of the object to be protected and its surroundings can also be clearly seen. Air-termination conductors are not required at these points (Figure 1). However, it must be observed that lightning footprints have also been found on steeples in places which were not directly touched as the rolling sphere rolled over. This, among other things, is due to the fact that in the event of multiple lightning strikes, the base of the lightning strike moves because of the wind conditions. Consequently, an area of approximately one metre can come up around the point of strike determined where lightning strikes can also occur. Application of the Rolling Sphere Method rolling sphere r r r r r r The rolling sphere does not only touch the steeple, but also the nave building of the church at multiple points further down the structure. All of the potential Fig. 1 points of strike are shown in gold.

ELPA 10515:2 Page 15 8.1.3.3 Rolling Sphere Applications Once the potential points of strike have been determined, air termination conductors and masts are installed in the pre-determined positions and then the rolling sphere is once again rolled over the structure with air terminals to ensure that the rolling sphere does not touch the structure but the air terminals. PROTECTION METHOD-ROLLING SPHERE Class of LPS Rolling Sphere Radius r M I 20 II 30 III 45 IV 60 If the rolling sphere is rolled over the structure in all possible directions then a protective ‘blanket’ is positioned over the structure or equipment that require protection. Application of Rolling Sphere on Buildings

ELPA 10515:2 Page 16 8.1.3.4 Calculation of Rolling Sphere Sag In many cases, the use of multiple masts is requires for large structures or structures with high lightning protection levels (i.e. LPL I and II) the sag of the rolling sphere between the air terminals is decisive when dimensioning the air-termination system for a structure or a roof-mounted structure. The following formula can be used to calculate the penetration or sag of the rolling sphere with a depth ‘p’: 2 d 2 p = r − r − 2 Where : p = Penetration Depth r = Radius of Rolling Sphere d = Distance between two Air Terminals In order to calculate the penetration depth properly the longest distance between the two air terminals must be calculated. Only once the penetration depth has been calculated can the height of the air termination masts be determined. Calculation of Penetration Depth ‘p’ between Penetration Depth ‘p’ of the Rolling Sphere Multiple Air Terminals air-termination conductor r Class of LPS penetration depth p r r 20 30 45 60 I II III IV ∆h d p ∆h d rectangular protected volume between four air-termination rods Calculation of Penetration Depth ‘p’ between Multiple Air Terminals d diagonal ∆h domelight installed on the roof

ELPA 10515:2 Page 17 8.1.4 Angle of Protection The protective angle method is derived from the electric-geometric lightning model. The protective angle is determined by the radius of the rolling sphere. The protective angle, which is comparable with the radius of the rolling sphere, is given when a slope intersects the rolling sphere in such a way that the resulting areas have the same size (Table 2). α° 80 Maximum Height of Protective Angle are: 70 60 LPL I = 20m Level of Lightning 50 Protection LPL II = 30m 40 LPL III = 45m 30 LPL IV = 60m I II III IV 20 For air terminals higher 10 than the maximum height as per table, the rolling 0 0 2 10 20 30 40 50 60 sphere method of protec- tion should be used. h [m] Table 2 Protective Angle Based Upon Height and Lightning Protection Level This method must be used for buildings with symmetrical dimensions (e.g. steep roof) or roof-mounted structures (e.g. antennas, ventilation pipes). 8.1.4.1 Determination of Angle of Protection The use of the old 45° angle of protection principle no longer applies, the angle of protection must now be determined by the table 2 above. The protective angle depends on the class of LPS and the height of the air-termination system above the reference α° α° h 1 plane. Air-termination conductors, air-termination rods, masts and wires should be arranged in such a way that all parts of the structure to be protected are situated within the protected volume of the air- termination system. The protected volume can be “cone-shaped” or “tent-shaped”, if a cable, for example, is spanned over it (Fig. 2 and Fig. 3). If air-termination rods are installed on the surface of the roof to Fig. 2 protect roof-mounted structures, the protective angle α can be different. In Figure 4, the reference plane for protective air-termination angle α1 is the roof surface. The protective angle α2 has the conductor ground as its reference plane and therefore the angle α2. α 2 α° h 1 h 1 α 1 h 1 h 2 H Angle α depends on the class of LPS and the height of the air-termination conductor above ground h 1 : Physical height of the air-termination rod Fig. 3 Note: Protective angle α refers to the height of the ATS. 1 h above the roof surface to be protected (reference plane). 1 Protective α refers to the heigh h = H + h where the earth 1 2 2 surface is the reference plane. Fig. 4

ELPA 10515:2 Page 18 8.1.5 Mesh Method of Protection A “meshed” air-termination system can be used universally regardless of the height of the building and shape of the roof. A meshed air-termination network with a mesh size according to the class of LPS is arranged on the roofing (Table 3 ). To simplify matters, the sag of the rolling sphere is assumed to be zero for a meshed air-termination system. By using the ridge and the outer edges of the building as well as the metal natural parts of the building serving as an air-termination system, the individual meshes can be positioned as desired. The air-termination conductors on the outer edges of the structure must be laid as close to the edges as possible. The metal capping of the roof parapet can serve as an air-termination conductor and / or a down conductor if the required minimum dimensions for natural components of the air-termination system are complied with Table 4. PROTECTION METHOD-MESH METHOD Class of LPS Mesh Size W M I 5 X 5 II 10 X 10 III 15 X 15 IV 20 X 20 Table 3 Gutter

ELPA 10515:2 Page 19 8.1.6 Combination of Air Terminals All three methods of protection namely the Rolling Sphere method, the Angle of Protection method and the Mesh method of protection can be combined to form one air termination system. The combination of the different methods of protection can result in the most effective air termination system that is specifically designed for the structure. Class of LPS Radius of the Mesh Size Rolling Sphere (M) I 20m 5 X 5m II 30m 10 X 10m Mesh Size M III 45m 15 X 15m IV 60m 20 X 20m Down Conductor Protective Angle Air Termination Rod h2 a Rolling Sphere r h1 Earth Termination System 8.1.7 Tall Structures Tall structures (taller than 60m) or structures where the rolling sphere touches the side of the structure not only require air terminals installed to the roof of the structure but additional air terminals must be installed around the side of the .structure Typically these additional air terminals are installed around the top 20% of the structure or wherever the rolling sphere touches the side of the structure. These air terminals are installed to protect structures from side flashes. 8.1.8 Natural Air Terminals Metal structural parts such as roof parapets, gutters, railings or claddings can be used as natural components of an air termination system. If a building has a steel frame construction with a metal roof and facade made of conductive material, these parts can be used for the external lightning protection system, under certain circumstances. Sheet metal claddings at or on top of the building to be protected can be used if the electrical connection between the different parts is permanent. These permanent electrical connections can be made by e.g. soldering, welding, pressing, screwing or riveting. The continuously welded surface of the connection must be at least 10 cm² with a width of at least 5 mm. If there is no electrical connection, these elements must be additionally connected e.g. by means of bridging braids or bridging cables. If the thickness of the sheet metal is not less than the value ‘t' in Table 4 and if melting of the sheets at the point of strike or the ignition of flammable material under the cladding does not have to be taken into account, such sheets can be used as an air-termination system. The material thicknesses are not distinguished according to the class of LPS.

ELPA 10515:2 Page 20 8.1.8 Natural Air Terminals (Contd.) If it is, however, necessary to take precautionary measures against melting or intolerable heating at the point of strike, the thickness of the sheet metal must not be less than value t in Table 4. The required thicknesses t of the materials can generally not be complied with, for example, in case of metal roofs. For pipes or containers, however, it is possible to comply with these minimum thicknesses (wall thicknesses). If, though, the temperature rise (heating) on the inside of the pipe or tank represents a hazard for the medium contained therein (risk of fire or explosion), these must not be used as air-termination systems. If the requirements concerning the appropriate minimum thickness are not met, the components, e.g. pipes or containers, must be situated in an area protected from direct lightning strikes. A thin coat of paint, 1 mm bitumen or 0.5 mm PVC, cannot be regarded as insulation in the event of a direct lightning strike. Such coatings are punctured when subjected to the high energies deposited during a direct lightning strike. If conductive parts are located on the surface of the roof, they can be used as a natural air-termination system if there is no conductive connection into the building. By connecting e.g. pipes or incoming electrical conductors, partial lightning currents can enter the structure and interfere with or even destroy sensitive electrical / electronic equipment. In order to prevent these partial lightning currents, isolated air termination systems must be installed for such roof-mounted structures. The isolated air-termination system can be designed using the rolling sphere or protective angle method. An air-termination system with a mesh size according to the class of LPS used can be installed if the whole arrangement is elevated (isolated) by the required separation distance ‘s’. See Item 7,0 for Isolated Lightning Protection Systems. Minimum Thickness of Natural Air Terminals Class Thickness Thickness Material of LPS a t [mm] b t' [mm] Lead – 2.0 Steel (stainless, 4 0.5 galvanised) I to IV Titanium 4 0.5 Copper 5 0.5 Aluminium 7 0.65 Zinc – 0.7 a t prevents puncture b t` only for sheet metal if puncture, overheating and ignition does not have to be prevented Table 4

ELPA 10515:2 Page 21 8.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.2 Down Conductor Systems The down conductor is the electrically conductive connection between the air-termination system and the earth-termination system. The function of a down conductor is to conduct the intercepted lightning current to the earth-termination system without damaging the building e.g. due to intolerable temperature rises. To avoid damage caused during the lightning current discharge to the earth-termination system, the down conductors must be mounted to ensure that from the point of strike to the earth, - Several parallel current paths exist, - The length of the current paths is kept as short as possible (straight, vertical, no loops), - The connections to conductive parts of the structure are made wherever required. 8.2.1 Determination of the Number of Down Conductors The number of down conductors depends on the perimeter of the external edges of the roof (perimeter of the projection onto the ground surface). The down conductors must be arranged to ensure that, starting at the corners of the structure, they are distributed as uniformly as possible to the perimeter. Depending on the structural conditions (e.g. gates, precast components), the distances between the various down conductors can be different. In each case, there must be at least the total number of down conductors required for the respective class of LPS. The SANS 62305-3 standard specifies typical distances between down conductors and ring conductors for each class of LPS (Table 5 ). Minimum Distance Between Down Conductors Class of LPS Typical distance I 10 m II 10 m III 15 m IV 20 m Table 5 The exact number of down conductors can only be determined by calculating the separation distance ‘s’. If the calculated separation distance cannot be maintained for the intended number of down conductors of a structure, one way of meeting this requirement is to increase the number of down conductors. The parallel current paths improve the partitioning coefficient kc . This measure reduces the current in the down conductors and the required separation distance can be maintained. Natural components of the structure (e.g. reinforced concrete supports, steel frameworks) can also be used as down conductors if continuous electrical conductivity can be ensured. By interconnecting the down conductors at ground level (base conductor) and using ring conductors for higher structures, it is possible to balance the lightning current distribution which, in turn, reduces the separation distance ‘s’. The latest SANS 62305 series attaches great significance to the separation distance. The measures specified allow to reduce the separation distance for structures and thus the lightning current can be safely discharged.

ELPA 10515:2 Page 22 8.2.2 Installation of Down Conductors Down conductors are normally mounted directly onto the building, if the walls are made of flame resistant or inflammable materials like masonry, bricks or concrete. If the building`s walls are made of combustible materials like wood then the installation of down conductors directly onto the structure is not recommended. The down conductors must be arranged in such a way that they are the direct continuation of the air-termination conductors. They must be installed vertically in a straight line so that they represent the shortest most direct connection to earth. Loops, e.g. on projecting eaves or structures, must be avoided. If this is not possible, the distance measured where two points of a down conductor are closest and the length I of the down conductor between these points must fulfil the requirements on the separation distance ‘s’ (Figure 5 ). The separation distance ‘s’ is calculated by means of the total length l = l1 + l2 + l3 . Loop in the Down Conductor l 1 s l 2 l 3 Fig. 5 Down conductors must not be installed in gutters and downpipes, even if they are incorporated into an insulating material since the moisture in the gutters would cause corrosion of the down conductors. If an aluminium down conductor is used, it must not be installed directly (without separation distance) on, in or under plaster, mortar or concrete nor in the ground. If it is equipped with a PVC sheath, aluminium can be installed in mortar, plaster or concrete. It is recommended to mount down conductors in such a way that the required separation distance ‘s’ is maintained from all doors and windows (Figure 6). Metal gutters must be connected with the down conductors at the points where they intersect (Figure 6). The base of metal downpipes must be connected to the equipotential bonding or earth-termination system, even if the downpipe is not used as a down conductor. Since it is connected to the lightning current carrying gutter, the downpipe also carries a part of the lightning current which must be diverted to the earth- termination system. Figure 6 illustrates a possible down conductor design. Down Conductor Design s Connection must be Only soldered or riveted as short as possible, downpipes may be used straight and vertical as a down conductor s s Fig. 6

ELPA 10515:2 Page 23 8.2.3 Down Conductor Materials and Sizes Copper, aluminium and galvanized steel are generally used as down conductor materials, the minimum dimension as shown below in Table 6. Protection Level Material Down Conductor mm² Copper 50 1 to 4 Aluminium 50 Steel 50 Table 6 8.2.4 Natural Down Conductors When using natural components of the structure as a down conductor, the number of separately installed down conductors can be reduced or, in some cases, no separately installed down conductors are required. The following parts of a structure can be used as natural components of the down conductor: - Structural Steelwork - Concrete Steel Reinforcing Care must be taken to ensure electrical continuity across the concrete steel reinforcing. This is normally achieved by install- ing an additional down conductor cast into the concrete column. - Rainwater Down Pipes Provided that the cross section exceeds 50mm², the thickness exceeds 0,5mm and that the sections are welded together. - Steel Facades Provided that the thickness exceeds 0,5mm and that there is electrical continuity in a vertical direction. Structural Steel Down Conductor Concrete Steel Reinforced Down Conductor

ELPA 10515:2 Page 24 8.2.4 Natural Down Conductors (Contd) Steel Facade used as Natural Down Conductor 8.2.5 External Down Conductors When the does not have natural elements that can be used as natural down conductors, then the installation of external down conductors is necessary. Normally aluminium conductors are used for this function but copper, stainless steel or galvanised steel conductors may also be used. Even if down conductors are covered in insulating material, shall not be installed in gutters or water spouts Aluminium Conductor Conductor Holder/ 8mm dia. (50mm²) Plastic Base Aluminium Conductor 8mm dia. (50mm²) Bimetallic Test Point 50mm² PVC Copper Conductor Aluminium Conductor Conductor holder 1000mm 8mm dia. (50mm²) for downpipe Bimetallic Test Point Conductor holder for downpipe Bimetallic Test Point 50mm² PVC Copper Conductor

ELPA 10515:2 Page 25 8.2.6 Test Points A test joint must be provided at every connection of a down conductor to the earth-termination system (above the earth entry, if practicable). Test joints are required to facilitate the inspection of the following characteristics of the lightning protection system: - Connections of the down conductors via the air-termination systems to the next down conductor, - Interconnections of the terminal lugs via the earth-termination system, e.g. in case of ring or foundation earth electrodes (type B earth electrodes), - Earth resistances of single earth electrodes (type A earth electrodes). Test joints are not required if the structural design (e.g. reinforced concrete or steel frame structure) allows no electrical isolation of the natural down conductor from the earth-termination system (e.g. foundation earth electrode). The test joint may only be opened with the help of a tool for measurement purposes, otherwise it must be closed. Each test joint must be clearly identifiable in the plan of the lightning protection system. Typically, all test joints are marked with numbers. 8.2.7 Courtyards Structures with enclosed courtyards with a perimeter of more than 30 m require down conductors with the distances shown in Table 5 (Figure 7). Down Conductor Systems For Courtyards 45 m metal capping of 15 m the roof parapet courtyard 7.5 m > 30 m courtyards with a cir- circumference 30 m cumference of more than 30 m, typical distances according to class of LPS Fig. 7 8.2.8 Earth Entry Points When using bare or uninsulated conductors, the point of entry of the uninsulated down conductor into the ground is particularly vulnerable to corrosion at this point of entry. Protection measures for the conductor by means of a PVC protective sheath must be installed to prevent corrosion. Bare Conductor PVC Protective Sheath 300mm

ELPA 10515:2 Page 26 8.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.3 Earth Termination Systems The earth-termination system is the continuation of the air termination systems and down conductors to discharge the lightning current to the earth. Other functions of the earth termination system are to establish equipotential bonding between the down conductors and to control the potential in the vicinity of the building walls. It must be observed that a common earth-termination system is to be preferred for the different electrical systems (lightning protection systems, low-voltage systems and telecommunications systems). This earth-termination system must be connected to the equipotential bonding system via the main earthing bar (MEB). Since the IEC 62305-3 (EN 62305-3) standard requires consistent lightning equipotential bonding, no particular value is specified for the earth resistance. In general, a low earth resistance (≤ 10 Ω, measured with a low frequency) is recommended. The standard distinguishes two types of earth electrode arrangements, namely, type A and type B . Both type A and B earth electrode arrangements have a minimum earth electrode length I1 of the earthing conductors according to the class of LPS (Figure 8) The soil resistivity should be determined by on-site measurements using the “WENNER method“ (four-pole measuring method). Minimum Length of Earth Electrodes l (m) 1 Length of Earth Electrode 70 class of LPS I 80 60 class of LPS II 50 40 30 20 10 0 class of LPS III-IV 0 500 1000 1500 2000 2500 3000 Soil Resistvity ρ (Ωm) E Fig. 8 8.3.1 Type A Earth Electrodes Type A earth electrode arrangements describe individually arranged vertical earth electrodes (earth rods) or horizontal earth electrodes (surface earth electrodes), which must be connected to a down conductor. A type A earth electrode arrangement require at least two earth electrodes. A single earth electrode is sufficient for individually positioned air-termination rods or masts. A minimum earth electrode length of 5 m is required for class of LPS III and IV. For class of LPS I and II the length of the earth electrode is defined as a function of the soil resistivity. Figure 8 shows the minimum earth electrode length I1. The minimum length of each earth electrode is: - I1 x 0.5 For vertical or inclined earth electrodes - I1 For horizontal earth electrodes. The values determined apply to each single earth electrode. If different earth electrodes (vertical and horizontal) are combined, the equivalent total length should be taken into account. The minimum earth electrode length can be disregarded if an earth resistance of less than 10 Ω is achieved.

ELPA 10515:2 Page 27 8.3.1 Type A Earth Electrodes (contd.) In general, earth rods are vertically driven deeply into natural soil which typically starts below foundations. Earth electrode lengths of 9 m have proven to be advantageous. Earth rods have the advantage that they reach soil layers in greater depths whose resistivity is generally lower than in the areas close to the surface. Type A earth electrodes do not meet the requirements with regard to equipotential bonding between the down conductors and potential control. Single earth electrodes of type A must be interconnected to ensure that the current is evenly split. This is important for calculating the separation distance ‘s’. Type A earth electrodes can be interconnected below or on the surface of the earth. When retrofitting existing installations the connecting cable of the single earth electrodes can also be implemented in the structure. 8.3.2 Type B Earth Electrodes Type B earth electrodes are ring earth electrodes encircling the object to be protected or foundation earth electrodes. If it is not possible to encircle the structure by means of a closed ring, the ring must be complemented by means of conductors inside the structure. Pipework or other permanently conductive metal components can also be used for this purpose. The earth electrode must be in contact with the soil for at least 80 % of its total length to ensure that a type B earth electrode can be used as a base for calculating the separation distance. The minimum lengths of type B earth electrodes depend on the class of LPS. In case of classes of LPS I and II, the minimum earth electrode length also depends on the soil resistivity (Figure 8). The mean radius r of the area encircled by a type B earth electrode must be not less than the specified minimum length l1. The number of additional earth electrodes must not be less than the number of down conductors, but at least two. These additional earth electrodes should be connected to the ring earth electrode so as to be spaced equally around the perimeter. If additional earth electrodes are to be connected to the foundation earth electrode, the earth electrode material and the connection to the foundation earth electrode must be observed. The following systems may place additional requirements on the earth-termination system: - Electrical systems – Disconnection requirements of the relevant system configuration (TN, TT, IT systems) in accordance with IEC 60364-4-41 / IEEE 80 - Equipotential bonding in accordance with SANS 62305-3 - Electronic systems – Data information systems / Telecomm systems - Antenna earthing - Electromagnetic compatibility (EMC) - Transformer earthing in or near the structure

ELPA 10515:2 Page 28 8.3.2 Type B Earth Electrodes (contd.) Foundation Earth Electrode - Foundation Earth Electrodes Type B earth electrodes are specified as ring type or foundation type - earth electrodes of new buildings. Many national and international ... 2 m ... standards prefer foundation earth electrodes because, when properly installed, they are embedded in concrete on all sides and - are thus corrosion and theft resistant. The hygroscopic characteristics of concrete typically ensure a sufficiently low earth resistance. The foundation earth electrode Higher earth electrode cross-sections may be re- must be installed as a closed ring in the strip foundation or floor quired for buildings with slab (Figure 9) and therefore primarily serves the purpose of transformer stations. functional equipotential bonding. Foundation earth electrode 70mm² bare copper conductor The division into meshes ≤ 20 m x 20 m and the connectors required to the outside to connect the down conductors of the Terminal lug to main earth bar external lightning protection system and to the inside for Terminal lugs to external LPS equipotential bonding must be considered (Figure 10). The Clamped connection to reinforcing installation of the foundation earth electrode is an electrical at intervals of 2m measure and must therefore be carried out or supervised by a Fixed earth terminal certified lightning protection specialist or electrician. Fig. 9 The question of how to install the foundation earth electrode depends on the measure required to ensure that the foundation earth electrode is embedded in concrete on all sides Mesh Foundation Earth Electrode ...2 m ... Additional connecting cable for forming meshes ≤ 20 x 20 m ≤ 20 m ≤ 20 m 15 m Fixed Earth Terminal According to LPL III Recommendation: Several at intervals of 15m fixed earth terminals installed in every electrical room Fig. 10

ELPA 10515:2 Page 29 8.3.2 Type B Earth Electrodes (contd.) - Ring Earth Electrodes The earth-termination system of existing structures can be design in the form of a ring earth electrode (Figure 11). This earth electrode must be installed as a closed ring around the building or, if this is not possible, a connection must be made inside the structure to close the ring. 80 % of the conductors of the earth electrode must be installed in such a way that they are in contact with the soil. If this is not possible, it has to be checked if additional type A earth electrodes are required. The requirements on the minimum earth electrode length must be taken into account depending on the class of LPS. When installing the ring earth electrode, it must be also observed that it is buried at a depth > 0.5 m and 1 m away from the building. If the earth electrode is driven into the soil as described before, it reduces the step voltage and thus controls the potential around the building. This ring earth electrode should be installed in natural soil. If it is installed in backfill or soil filled with construction waste, the earth resistance is reduced. When choosing the earth electrode material with regard to corrosion, local conditions must be taken into consideration. It is advisable to use stainless steel. This earth electrode material does neither corrode nor subsequently require time-consuming and expensive reconstruction measures for the earth-termination system such as removal of paving stones, tar surfaces or even steps for installing a new earthing material. In addition, the terminal lugs must be particularly protected against corrosion. Ring Earthing System Around Structure HES Fig. 11 Type A Earth Electrodes Type B Earth Electrodes

ELPA 10515:2 Page 30 8.3.3 Integrated Earth Electrodes The use of a single integrated earthing system for all of a site`s earthing requirements is currently regarded as being ‘good practice’. The single integrated earthing system would typically serve for the protection of the following systems : - High-voltage System (HV system) - Medium-voltage System (MV system) - Low-volatge System (LV system) - Information Technology (IT system) The basis for the reliable interaction of the various systems is a common earth termination system and a common equipotential bonding system. It is therefore imperative that all conductors clamps and connectors are specified for the various applications. For buildings with integrated transformers, the standards concerning power plants / substations with nominal voltages over 1 kV must be considered. The conductor materials and connection components for use in HV, MV and LV systems must comply with the requirements for 50Hz currents. Because prospective 50Hz short circuit currents may occur, it is imperative that the minimum cross sections of the earthing materials be determined. Currents of short circuits to earth must not lead to inadmissable overheating of the components. Unless otherwise specified, the standard 1 second duration of the fault current and the maximum 300°C are used for the calculation of the earthing conductors and connection components. The material and the current density ‘G’ (in A/mm²) in relation to the fault current duration are essential in the selection of the earthing conductor cross section. The diagram below shows the permissible 50 Hz short circuit current density (G) for conductor materials copper, galvanised steel and stainless steel 2000 copper 1000 galvanised steel G 800 2 [A/mm ] 600 StSt V4A (1.4571) 400 300 200 150 100 80 60 40 t = duration of fault current F G = short-circuit current density 20 10 0,02 0,06 0,1 0,2 0,4 0,8 2 4 6 10 0,04 0,08 0,6 1 t [s] F Ampacity of Earth Electrode Materials

ELPA 10515:2 Page 31 8.3.3 Integrated Earth Electrodes (Contd) 50 Hz Ampacity of Conductors and Connection Components (Contd) Calculation of Cross Section Earthing Conductor Size Option 1 Specification of 3-phase fault current by the system designer. Eg. I k3 = 15000 A Option 2 Calculation of theoretical worst case 3-phase fault current, assuming that the supply voltage will remain constant. The short circuit voltage (Uk) is used to determine the max three phase short circuit current. The three phase short circuit current I”k3 is the maximum fault current at the transformer, neglecting the impedance on the fault site (Z=0). In the calculation, the following data is considered at the transformer : - Normal capacity of the transformer S = 630kVA - Nominal voltage on the low-voltage side U = 400V - Short circuit voltage Uk = 6.05% Calculation Linear conversion for the fault current voltage (worst case) : S I’’ = –––––––––––– k3 √ 3 XU X U k 630X 10 VA 3 I’’ = ––––––––––––––––– ≈ 15000 A k3 √ 3 X400 V X 0.0605 Current Division If the short-circuit current to earth spreads via the earthing system and the protective equipotential bonding conductors, it may be assumed that the current will be distributed at the nodal point into two directions. The asymmetry in the intermeshing of the earth termination system can be assumed with a sufficient accuracy of 65%. I”kEE(branch) is calculated as follows : I”kEE(branch) = 0.65 X I”k3 I”kEE(branch) =0.65 X 15000A = 9750A The current of 9750A is therefore taken as the basis for the dimensioning of the cross section of the earth termination system.

ELPA 10515:2 Page 32 8.3.3 Integrated Earth Electrodes (Contd) 50 Hz Ampacity of Conductors and Connection Components (Contd) Calculation of Cross Section Earthing Conductor Size Determination of the Resulting Cross Section The cross section of the conductor results from the material and the disconnecting time. Time St/tZn Copper StSt (V4A) 0.3 s 129 A/mm 2 355 A/mm 2 70 A/mm 2 0.5 s 100 A/mm 2 275 A/mm 2 55 A/mm 2 1 s 70 A/mm 2 195 A/mm 2 37 A/mm 2 3 s 41 A/mm 2 122 A/mm 2 21 A/mm 2 5 s 31 A/mm 2 87 A/mm 2 17 A/mm 2 The determined current now is divided by the Current Density G of the respective material and the assigned disconnecting time and the minimum cross section Amin of the conductor will be determined. Legend: S Nominal capacity [VA] I’’kEE / (branch) A min = –––––––––– (mm²) U Nominal voltage (low voltage) [V] G u k Short-circuit voltage [%] I K Short-circuit current [A] I’’ k3 Three-pole short-circuit current [A] I’’ kEE Double short-circuit current to earth [A] G Short-circuit current density [A/mm²] A Min Minimum cross section [mm²] With the cross section calculated, the conductor may be selected. Always the next largest nominal cross section conductor will be taken. Conclusions 1) Only lightning protection systems with conductors, earth electrodes, connectors and other lightning protection components that are tested in accordance with the SANS 62561 series of standards comply with the requirements of the SANS / IEC 62035 series of standards. 2) LPS designers cannot just presume that a 70mm² bare copper earth termination system will comply with the relevant SANS standards, the minimum cross sections must be calculated and taken into account specific to the electrical supply of the particular site. 3) The information provided in this handbook are guidelines to the proper design of an integrated earth termination system. The correct design principles for the earth termination system design for 50Hz systems, in particular for substations and switch yards will be covered in detail in a separate accreditation course.

ELPA 10515:2 Page 33 8.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.4 Lightning Equipotential Bonding Equipotentialization is performed to prevent dangerous sparking within a structure due to lightning current lowing in the external LPS or any conductive parts of a structure. The equipotential bonding of the following elements to the external LPS is essential : - Metal Installations - Internal Systems - External conductive parts and lines connected to the structure. The interconnection of the LPS to these systems can be done by means of the following : - Bonding conductors, where electrical continuity is not provided by natural bonding - Surge Protection Devices, where direct connections with bonding conductors is not feasible. The correct principles of the various methods of carrying out the lightning equipotential bonding is shown in Figure 12. The correct lightning equipotential is vitally important in preventing fire (dangerous sparking) and protecting electronic equipment from damage. Principles of Lightning Equipotential Bonding buried installation, functionally isolated (e.g. cathodically protected tank) metal element extend- ing through the entire building (e.g. lift rail) telecommunications system equipotential bonding system 230/400 V Main earthbar Foundation earth antenna of the bathroom kWh electrode Connector Lightning current arrester Connecting clamp Pipe clamp Terminal lug / earthing conductor to PEN Isolating spark gap SEB heating insulating joint gas waste- distribution network M information technology system water water M terminal lug for external lightning protection system foundation earth electrode/ lightning protection earth electrode Fig. 12

ELPA 10515:2 Page 34 8.4 Lightning Equipotential Bonding 8.4.1 Equipotential Bonding of Pipes In order to integrate pipes in the equipotential bonding system, earthing pipe clamps which correspond to the diameters of the pipes are used (Figure 13). Stainless steel earthing pipe clamps with tensioning straps, which can be universally adapted to the diameter of the pipe, offer enormous installation benefits (Figure 14). These earthing pipe clamps can be used to clamp pipes made of different materials (e.g. steel, copper and stainless steel) and also allow through-wiring. Figure 15 shows the equipotential bonding system of heating pipes with through-wiring. Pipe Clamp Pipe Clamp Bonding of Heating Pipes Fig. 13 Fig. 14 Fig. 15 8.4.2 Minimum Cross Sectional Size of Bonding Conductors The cross-sections of conductors used for lightning protection purposes must be dimensioned for high stress since these conductors must be capable of carrying lightning currents. Therefore, they must have larger cross-sections. Irrespective of the class of LPS, the minimum cross-sections according to Table 7 must be used for connecting equipotential bonding bars with one another and to the earth termination system. The minimum cross-sections of equipotential bonding conductors, which allow to connect internal metal installations to the equipotential bonding bar, can be smaller since only low partial lightning currents flow through these conductors (Table 8). Minimum Conductor Size for Bonding Between Bars Class of LPS Material Cross-section 2 Copper 16 mm - 2 - I to IV Aluminium 25 mm Steel 50 mm² Table 7 Minimum Conductor Size for Bonding Internal Metal Elements Class of LPS Material Cross-section Copper 6 mm 2 2 I to IV Aluminium 10 mm Steel 16 mm² Table 8

ELPA 10515:2 Page 35 8.4.3 Equipotential Bonding of Electrical Supply Lines In addition to the equipotential bonding for metal installations, the DEHNventil Combined Arrester for Bonding equipotential bonding for the feeder cables of the low-voltage electrical of Incoming Electrical Lines installation should also be established directly at the entry point into the building. The requirements governing the installation of the surge protective devices upstream of the meter of the low-voltage electrical installation (main power supply system) are described in SANS 62305 Part 4. 8.4.4 Equipotential Bonding of Cable Armouring Cable shielding can play a large role in the prevention of damage to electrical equipment, cable shielding is used to reduce the effect of interference on active lines and the interference emitted from active lines onto neighboring systems. . Guidelines For Shield Earthing - A cable shield must be continuously connected along the whole of its length for good conducting performance. - Cable shielding should be earthed at least at both ends. - Only a shield earthed at both ends can reduce inductive and capacitive inputs. - Shields earthed at one end reduces the irradiation of electric fields but does not offer protection against the electromagnetic induction arising with lightning strikes. - Shields must enclose the conductors completely. - LV cables, telecommunication cables auxiliary cables and other sensitive system cables should be separated to prevent interference. - Cable ducting should fully enclose all cables, be electrically continuous and be earthed as frequently as possible, at least at the beginning and at the end. C the impulse transfer EBB 1 EBB 2 EBB 1 impedance of the EBB 2 shield has to be considered! No shield connection – No shielding from capacitive/inductive couplings Shield connection at both ends – Shielding from capacitive/inductive couplings shield terminal not recommended Recommended cable shield l.v. cables right auxiliary cables telecommunica- tion cables cable metal cable trays sensitive applications anchor bar Low voltage cables Telecommunication cables Auxiliary cables (e.g. fire alarm systems, door openers) Cables for sensitive applications Shield Connection Separation of Cables in Cable Duct Systems

ELPA 10515:2 Page 36 8.4.5 Equipotential Bonding of IT Systems As with electrical supply lines Telecomm and Data lines that enter the building or transition from one lightning protection zone to another lightning protection zone require equipotential bonding. This equipotential bonding is performed by the installation of surge protection devices, the type of surge arrester or lightning arrester depends on in which lightning protection zone the equipotential bonding is carried out. See Item 5 in this document for the design principles for the Lightning Protection Zoning Concept. Bonding of Instrumentation Lines To Protected Equipment BLITZductor Class 1 & 2 Surge Arrester Din Rail To Main Earth Bar Bonding of Network Cables Protected Cables to Equipment Din Rail Network Surge Arrester To Main Earth Bar Unprotected Cables Bonding of Network Switches Network Cabinet Network Hub NET-protecter Equipotential Bonding to Earth Bar NET-protecter

ELPA 10515:2 Page 36 8.4.5 Equipotential Bonding of IT Systems (Contd.) Bonding of Telecom Lines Krone Block Type ADSL Modem / Router Surge Arrester Incoming Telecom Line Termination Block for Incoming Telecom Lines Mounting Bracket Type 2 ADSL Surge Arrester 8.4.6 Bonding of Other Conductive Elements Bonding of Cable Racks Fixed Earth Terminal Cable Rack Bridge Connection 70mm² PVC Copper Bonding of Handrails Metallic Hand Rail Metallic Hand Rail Aluminium Conductor Aluminium Conductor Bolted Connection Fixed Earth Terminal Fixed Earth Terminal

ELPA 10515:2 Page 37 8.4.7 Equipotential Bonding in Large Structures Conductive elements should be bonded directly to Equipotential earth bars if possible. Larger structures require the installation of several equipotential earth bars. All equipotential earth bars shall be interconnected together, these interconnections as well the runs to the earth termination system should be kept as short as possible. Very long equipotential bonding runs can be the cause for big earth loops leading to large induced voltages. To minimize these effects, a meshed interconnection of equipotential earth bars with short connection runs is required. Concrete steel reinforcing steel which is used as part of the down conductor system of structures should be utilised for both internal and external bonding of conductive elements. The same applies to other natural down systems such as interconnected structural steelwork. The use of the concrete steel reinforcing for the equipotential bonding will result in enhanced current division and therefore only a minor fraction of the total lightning current can be expected to flow through the bonding parts. 8.4.8 Equipotential Bonding of External Conductive Elements External Bonding is required for the following types of elements : • Connected piping , gantries, walkways and other steelwork • Conductive elements external to the structure e.g.. facades, curtain walls, stairways, cat ladders, handrails etc. • All conductors (power, data and telephone) shall be bonded to the LPS via SPDs Bonding of external elements into the LPS should be done as close to the point of entry into the protected space as possible – bonding should be done at ground floor level or in basements if applicable.

ELPA 10515:2 Page 38 8.0 SANS 62305 Part 3 - Protection Against Physical Damage & Life Hazard 8.5 Separation Distance Concept The ‘Separation Distance’ concept are the measures employed when an Isolated Air Termination System is required. In accordance with the SANS / IEC Code 62305 series, “An isolated external LPS should be used when the flow of the lightning current into bonded internal conductive parts may cause damage to the structure or its contents.” In other words; an isolated LPS should be installed to prevent partial lightning currents from entering into protected space via electrical equipment or plant situated in areas that are vulnerable to direct lightning strikes. The uncontrolled entry of partial lightning currents into a structure can lead to flashovers between the LPS and the internal conductive elements of the structure. This will result in the risk of fire and damage to internal systems will be unacceptably high. The correct separation distance therefore must be maintained to prevent these flashovers. Isolated LPS and Separation Distances Special problems occur when plant and equipment is installed to roofs and these elements are vulnerable to direct lightning strikes, these vulnerable elements require additional protection measures. If the roof mounted plant and equipment is connected directly to the external lightning protection system, then, in the event of a direct lightning strike, partial lightning currents are conducted into the structure. This could result in the destruction of surge sensitive equipment, the increase of step and touch hazards and the increased risk of fire within the structure. Direct lightning strikes to the roof mounted equipment can be prevented by having an isolated air termination system. An isolated air termination system is achieved by calculating and maintaining a separation distance ‘s’ between the equipment and the air terminal. The separation distance must therefore be taken into account when dimensioning the air termination system. Assumed flow of Lightning current Protection of roof mounted equipment with Isolated Air Termination System Assumed flow of Lightning current

ELPA 10515:2 Page 39 8.5 Separation Distance Concept 8.5.1 Separation Distance for Down Conductors Separation Distance of Down Conductors The separation distance between the LPS down conductors and internal conductive elements increases linearly with length from zero separation distance at ground floor to the calculated separation distance at roof level (Figure 16). The use of natural down conductors such as concrete steel reinforcing or structural S1 steelwork eliminates the need to maintain the separation distance, S1 this is because of the enhanced current division of the natural down conductors. In order to maintain the separation distance of down conductors the down conductor must be physically separated away from any S2 S2 internal conductive elements. This can be achieved by using non-conductive fibre glass rods to isolate the down conductor from the structure. The separation distance of down conductors can also be acheived by using HVRI (High Voltage Resistant Insulated) conductors. Depending on the manufacturer, the applicable HVRI conductor should be selected based upon the calculated maximum separation distance (Figure 17). MDB Different Types of HVI Conductors MEB Fig. 18 HVI light Conductor HVI long Conductor HVI power Conductor Fig. 17 8.5.2 Separation Distance Calculation (Simplified Method) The calculation of the separation distance forms the basis for the creation of an isolated lightning protection system. Consequently, the design of an isolated lightning protection system is based on the calculated separation distance. To be able to take adequate protection measures, the separation distance calculations must form part of the LPS design. The absolute conductor lengths are decisive for calculating the separation distance. According to SANS 62305-3, the separation distance ‘s’ for preventing uncontrolled flashovers is calculated as follows: k k Note: s= i c l The separation distance is determined by means k of the length (l) of the down conductor, the class Where: m of LPS (ki), the distribution of the lightning current s = separation distance to different down conductors (kc) and the material factor (km). ki = depends on the selected class of LPS kc = depends on the lightning current flowing through the down conductors km = depends on the material of the electrical insulation l = length along the air-termination system or down conductor in metres from the point where the separation distance is supposed to be determined to the next equipotential bonding or earthing point

ELPA 10515:2 Page 40 8.5 Separation Distance Concept 8.5.3 Separation Distance Calculation for Multiple Down Conductors (Simplified Method) The calculation of the separation distance is dependent on the current division properties of the DCS and the ATS. The more current division paths from the point of strike, the less then Separation distance will be. Formula for calculating the partitioning coefficient k of a LPS with multiple down conductors is as c follows: 1 3 c k = ¾¾ + 0.1 + 0.2 · ¾ c 2 n h · Where: n = total number of down-conductors c = distance of a down-conductor to the next down-conductor h = spacing (or height) between ring conductors Once Kc has been calculated, the appropriate separation distance is calculated using the simplified method formula on page 38. 8.5.4 Separation Distance Calculation Detailed Method The calculation of more complex arrangements involve using more complex calculation formulas. In order to calculate the correct separation distances, please refer to SANS 62305-12 part 3 annexure C. It is also possible to use specifically designed computer software to assist you with these more complex calculations. The example below gives an indication of the calculation formula used for a meshed type ATS. Ki s = ( Kc1 L1 + Kc2 L2 + ... + Kcn Ln ( Km

ELPA 10515:2 Page 41 8.5.5 Separation Distances for Air Terminals In order to provide effective protection for structures that have rooftop plant and equipment, the air termination system must be isolated from the rooftop plant. A non-isolated LPS will allow partial lightning currents to enter into the building and thereby causing damage to internal elements of the structure. There is also an unacceptably high risk of fire caused by uncontrolled sparking inside the structure and the risk of high step and touch voltages being present as well causing injury or death to people. An isolated LPS is created by calculating the required separation distance. Then the air termination masts are installed far enough away from the rooftop equipment so that any lightning currents travelling along the air termination conductors are not induced onto the equipment or their cables. If possible, conventional air termination masts should be installed at a minimum distance away from the rooftop plant and their cables. If it is not possible to install the air terminals a sufficient distance away from the rooftop plant then HVRI conductors should be considered. Rooftop Plant / Equipment Zone of Protection Tripod Mast Installed with Separation Distance OK S S Separation Distance OK Physically Separated Air Terminals 8.5.6 Design and Functional of HVRI Conductors The basic principle of a high-voltage-resistant, insulated down conductor is that a lightning current carrying conductor is covered with insulating material to ensure that the required separation distance ‘s’ from other conductive parts of the building structure, electrical lines and pipelines is maintained. In principle, a high-voltage- resistant, insulated down conductor must fulfil the following requirements: - Sufficient electric strength of the insulation in case of lightning voltage impulses along the entire HVI Conductor - Prevention of creeping discharge - Sufficient current carrying capability thanks to a sufficient cross-sectional area of the down conductor - Lightning current carrying connection of the down conductor to the air-termination system (air-termination rod, air termination conductor, etc.) - Connection to the earth-termination or equipotential bonding system

ELPA 10515:2 Page 42 8.5.6 Separation Distance for Rooftop Plant Metal and electrical roof-mounted structures protrude from the roof level and are exposed to lightning strikes. Due to conductive connections into the structure via pipes, ventilation ducts and electrical lines, partial lightning currents may be injected into the structure. The injection of partial lightning currents into the structure is prevented by connecting an isolated air-termination system to the insulated down conductor which ensures that the entire electrical / metal equipment protruding from the roof is located in the protected volume. The lightning current is led past the structure to be protected and is distributed via the earth-termination system. According to the state of the art of lightning protection technology, such roof-mounted structures are protected against direct lightning strikes by means of isolated air termination system. This prevents partial lightning currents from entering the building where they would interfere with or even destroy sensitive electrical / electronic equipment. In the past, these roof-mounted structures were directly connected so that parts of the lightning current were conducted into the building. Later, roof-mounted structures were indirectly connected via a spark gap. This meant that direct lightning strikes to the roof-mounted structure could still flow through the “internal conductor” although the spark gap should not reach the sparkover voltage in the event of a more remote lightning strike to the building. This voltage of approximately 4 kV was almost always reached and thus partial lightning currents were also injected into the building via the electrical cable, for example, which led to interference with the electrical or electronic installations. The only way of preventing these currents from being injected into the building is to use isolated air-termination systems which ensure that the separation distance ‘s’ is maintained. Once the separation distances at roof level are calculated, then air termination masts are installed to protect the rooftop plant by either the rolling sphere or angle of protection and if possible normal tripod masts are installed at the calculated separation distance and high enough to afford the correct zone of protection. If the dimensions of the structure do not allow for enough distance to install normal tripod masts then HVRI masts are installed with the type of HVRI conductor being selected based upon the calculated separation distance. Different HVRI manufacturers have different HVI conductors with different equivalent separation distances. This information should be obtained from the manufacturers of the HVRI conductor. Isolated Lightning Protection α α air-termi- nation tip sealing end range GRP/Al supporting tube antenna cable earthing air termination conductor low-voltage feeder cable RBS sealing end HVRI Conductor bare down conductor equipotential bonding conductor

ELPA 10515:2 Page 43 8.6 Step and Touch Potentials- LPS SANS 62305 Part 3 indicates that in some cases outside of a building the touch voltage may be extremely dangerous near the down conductors even though the structure may have a lightning protection system installed in accordance with the standards. The dangerous touch potentials can occur where down conductors are installed near entrances or high visitor frequency areas such shopping centres, theatres etc. The exposure to the dangerous touch potentials is increased when bare or uninsulated down conductors are used. The presence of dangerous step potentials occur when people are standing in close proximity to the down conductor and the lightning protection earth electrode connected to the down conductor. The touch potential is defined as the voltage affecting a person standing on the ground within a distance of 1m from the down conductor and who is touching the down conductor. In this case the current flows from the hand into the body and down to the feet (Fig. 21). The LPS design should avoid the placement of down conductors in areas where dangerous potentials can occur. 8.6.1 Protection Against Touch Voltages If the installation of a down conductor in a dangerous area is unavoidable, then the dangerous down conductor must be protected from touch voltages to an area which is at least the height of a person standing with their arms raised plus a separation distance ‘s’, (Fig. 22) Effective protection measures against touch voltages are defined as follows: - Installation of an insulated (coated) conductor with at least a 3mm thick cross-linked polyethylene covering. This conductor must also be able to prevent creepage sparkovers in the event of rain. - Installation of physical barriers and /or warning signs to minimise the possibility of the down conductors being touched. - Installation of specialised conductors has been specifically designed to serve the purpose of protection against touch voltages. specialised down conductor anti-splash plate 3 m insulation U t ±0 ground level Fig. 21 Schematic Diagram Fig.22 Protective Measures of Touch Voltage Ut

ELPA 10515:2 Page 44 8.6.2 Protection Against Step Voltages The protection against step voltages for dangerous down conductor locations must also be taken into account when a LPS. The risk to living beings can be reduced by increasing the resistance of the surface ground (asphalt or concrete) and barriers or warning signs can be installed. a meshed type earth termination system should be installed around the dangerous down conductor. This type of earthing system is called the potential control grid and installed in addition to the lightning protection earth termination system (Fig. 23). 8.6.3 Natural Protection Measures SANS 62305 Part 3 states that in certain circumstances the provision of protection against step and touch voltages can be ignored. These are as follows: - When natural down conductor systems are installed (concrete steel reinforcing or structural steel work) - When the LPS has more than ten down conductors and earthing positions. 480 698 4013364144590 1-7-1 128 g 1 pc(s) 49,50 € Fig.23 Protective Measures Warning Sign