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TECHNICAL REPORT Protection against lightning Risk assessment selection of protection measures Designer info: Name: James Address: Badoers City: Kinsington Postal code: 44200 Country: NZ Professional register: Engineering Professional register number: K121-NZ VAT number: Tax code: - Customer: Customer: METALPHA Sa - industrial design Structure description: Production site Address: 32, Newport Rd City: New Castle District: NZ INDEX 1. DOCUMENT CONTENTS 2. TECHNICAL STANDARDS 3. STRUCTURE TO BE PROTECTED 4. INPUT DATA 4.1 Lightning ground flash density. 4.2 Structure data. 4.3 Electrical lines data. 4.4 Definition and characteristics of zones 5. STRUCTURE AND ELECTRICAL LINES COLLECTION AREAS 6. RISK ASSESSMENT 6.1 Risk R1 loss of human life 6.1.1 Risk calculation R1 6.1.2 Risk assessment R1 7. SELECTION OF PROTECTION MEASURES 7.1 Economic analysis 8. CONCLUSIONS 9. APPENDICES 10. ANNEXS Structure layout Collection area Ad Collection area Am SPD installation Am 1. CONTENT OF DOCUMENT This document contains: - the lightning risk assessment; - the draft design of required protection measures. 2. TECHNICAL STANDARDS This document refers to the following standards: - EN 62305-1: "Protection against lightning. Part 1: General principles" March 2006; - EN 62305-2: "Protection against lightning. Part 2: Risk assessment" March 2006; - EN 62305-3: "Protection against lightning. Part 3: Physical damage to structures and life hazards" March 2006; - EN 62305-4: "Protection against lightning. Part 4: Electrical and electronic systems within structures" March 2006; 3. STRUCTURE TO BE PROTECTED It is important to define the part of structure to be protected in order to define dimensions and characteristics to be used for collection area calculation. The structure to be protected: - is a vertical part of a building; - there are not internal systems in common with other part of the building, - is separated from other parts of the building by menas of walls with resistance to fire of 120 min (REI 120). Therefore the dimensions and characteristics of the structure to be considered are the same of the structure (art. A.2.1.2 - standard EN 62305-2). 4. INPUT DATA 4.1 Lightning ground flash density The lightning flash density in the city of where the structure is located is: Ng = 2,0 flashes/km² year 4.2 Structure data The structure's layout is described in Annex Structure layout. The prevalent type of structure is: industrial The structure could be subject to: - loss of human life - loss of economic value To evaluate the need of protection against lightning, according to standard EN 62305-2, should be calculated: - risk R1; To evaluate the cost effectiveness of protection it is necessary to calculate risk 4. The building has a metallic structure or continuos reinforced concrete framework. 4.3 Electrical lines data The structure is served by the following electrical lines: - Power line: Power aerial - Power line: Power mixed - Power line: Telecom The electrical lines characteristics are described in Appendix Electrical lines charactersitics. 4.4 Zones definition and characteristis With reference to:: - existing walls with resistence to fire of 120 min; - rooms already protected or that should be opportune to protect against LEMP (lightning electromagnetic pulse); - type of soil outside the structure, type of surface inside the structure and the possible presence of persons; - others structure characteristics, as the layout of internal systems and existing protection measures; are defined the following zones: Z1: External Z2: Office Z3: Production The zones characteristics, mean loss values, type of risks and related component are reported in Appendix Zones characteristics. 5. STRUCTURE AND ELECTRICAL LINES COLLECTION AREAS The collection area Ad due to direct flashes to the structure is calculated with graphic method according to standard EN 62305-2, art.A.2 and it is reported in Annex Collection area Ad. The collection area Am due to flashes near the structure, which could damage internal systems due to induced overvoltages, is calculated with graphic method according to standard EN 62305-2, art.A.3 and it is reported in Annex Collection area Am. The collection areas Al e Ai for each electrical line is calculated with analytic method according to standard EN 62305-2, art.A.4. The values of collection areas (A) and related annual number of dangerous events (N) are reported in Appendix Collection areas and annual number of dangerous events. The values of probability of damage (P) used to calculate the selected risk components are reported in Appendix Values of probability of damage for unprotected structure. 6. RISK ASSESSMENT 6.1 Risk R1: loss of human life 6.1.1 R1 calculation The values of risk components and the value of risk R1 are listed below. Z1: External RA: 1,10E-07 Total: 1,10E-07 Z2: Office RB: 1,10E-06 RC: 5,51E-06 RM: 4,30E-05 RU(Power office): 1,90E-12 RV(Power office): 3,79E-07 RW(Power office): 1,90E-06 RZ(Power office): 3,07E-05 RU(Telecom office): 5,37E-12 RV(Telecom office): 1,07E-06 RW(Telecom office): 5,37E-06 RZ(Telecom office): 1,12E-05 Total: 1,00E-04 Z3: Production RB: 1,10E-06 RC: 1,65E-05 RM: 1,72E-04 RU(Power production): 3,57E-12 RV(Power production): 7,15E-08 RW(Power production): 1,07E-06 RZ(Power production): 9,51E-06 RU(Telecom production): 5,37E-11 RV(Telecom production): 1,07E-06 RW(Telecom production): 1,61E-05 RZ(Telecom production): 3,36E-05 Total: 2,51E-04 Value of total risk R1 for the structure: 3,51E-04 6.1.2 Analysis of risk R1 The total risk R1 = 3,51E-04 is greater than the tolerable risk RT = 1E-05, therefore it is necessary to select protection measures to reduce it. The risk components that constitute risk R1, reported in percentage of risk R1 for the structure, is listed below. Z1 - External RD = 0,0314 % RI = 0 % Total = 0,0314 % RS = 0,0314 % RF = 0 % RO = 0 % Total = 0,0314 % Z2 - Office RD = 1,8826 % RI = 26,6432 % Total = 28,5258 % RS = 0 % RF = 0,7275 % RO = 27,7982 % Total = 28,5257 % Z3 - Production RD = 5,0201 % RI = 66,4227 % Total = 71,4428 % RS = 0 % RF = 0,64 % RO = 70,8029 % Total = 71,4429 % where: - RD = RA + RB + RC - RI = RM + RU + RV+ RW + RZ - RS = RA + RU - RF = RB + RV - RO = RM + RC + RW + RZ and: - RD is the risk due to flashes striking the structure - RI is the risk due to flashes influencing it but not striking the structure - RS is the risk due to injury to livings beings - RF is the risk due to physical damage - RO is the risk due to failure of internal systems. The values listed above, show that risk R1 for the structure is essentially present in the following zones: Z3 - Production (71,4428 %) - essentially due to failure of internal systems - mainly due to flashes striking the structure and flashes influencing it but not striking the structure - the mainly contribution to the value of risk R1 inside the zone is determineted by the following risk components: RM = 68,4946 % Internal systems failure due to flashes influencing it but not striking the structure 7. SELECTION OF PROTECTION MEASURES To reduce the risk R1 below to the tolerable risk RT = 1E-05, it is necessary to act on the following risk components: - RC in the zones: Z3 - Production - RM in the zones: Z2 - Office Z3 - Production - RW in the zones: Z3 - Production - RZ in the zones: Z2 - Office Z3 - Production using at least one of the following possible protection measures: - for risk component C: 1) Coordinated SPD protection - for risk component M: 1) Coordinated SPD protection 2) Shielding the structure 3) Shielding the internal system or provide an adeguate routing 4) Increasing the impulse withstand voltage of equipments - for risk component W: 1) Coordinated SPD protection 2) Increasing the impulse withstand voltage of equipments - for risk component Z: 1) Coordinated SPD protection 2) Increasing the impulse withstand voltage of equipments To protect the structure the following protection measures are selected: - install LPS of class III (Pb = 0,1) - In the zone Z2 - Office: Internal system: Power office - Coordinated SPD - level: II Internal system: Telecom office - Coordinated SPD - level: I - In the zone Z3 - Production: Internal system: Power production - Coordinated SPD - level: I Internal system: Telecom production - Coordinated SPD - level: I - For the line Line1 - Power aerial: - SPD at line entrance - level: II - For the line Line2 - Power mixed: - SPD at line entrance - level: I - For the line Line3 - Telecom: - SPD at line entrance - level: I The selected protection measures modify risk parameters and components. The values for risk parameters related to the protected structure are listed below. Zone Z1: External Pa = 1,00E+00 Pb = 0,1 Pc = 1,00E+00 Pm = 1,00E+00 ra = 0,01 rp = 1 rf = 0 h=1 Zone Z2: Office Pa = 1,00E+00 Pb = 0,1 Pc (Power office) = 2,00E-02 Pc (Telecom office) = 1,00E-02 Pc = 2,98E-02 Pm (Power office) = 2,00E-02 Pm (Telecom office) = 1,00E-04 Pm = 2,01E-02 Pu (Power office) = 2,00E-02 Pv (Power office) = 2,00E-02 Pw (Power office) = 2,00E-02 Pz (Power office) = 2,00E-02 Pu (Telecom office) = 1,00E-02 Pv (Telecom office) = 1,00E-02 Pw (Telecom office) = 1,00E-02 Pz (Telecom office) = 1,00E-02 ra = 0,00001 rp = 0,5 rf = 0,01 h=2 Zone Z3: Production Pa = 1,00E+00 Pb = 0,1 Pc (Power production) = 1,00E-02 Pc (Telecom production) = 1,00E-02 Pc = 1,99E-02 Pm (Power production) = 1,00E-02 Pm (Telecom production) = 1,00E-04 Pm = 1,01E-02 Pu (Power production) = * Pv (Power production) = * Pw (Power production) = * Pz (Power production) = * Pu (Telecom production) = 1,00E-02 Pv (Telecom production) = 1,00E-02 Pw (Telecom production) = 1,00E-02 Pz (Telecom production) = 1,00E-02 ra = 0,00001 rp = 0,2 rf = 0,01 h=5 (*) In case of lines with different sections, the probability refers to each section. See Appendix Electrical lines characteristics. Risk R1: loss of human life The values of risk components for protected structure are listed below. Z1: External RA: 1,10E-07 Total: 1,10E-07 Z2: Office RB: 1,10E-07 RC: 1,64E-07 RM: 1,15E-06 RU(Power office): 3,79E-14 RV(Power office): 7,58E-09 RW(Power office): 3,79E-08 RZ(Power office): 1,53E-06 RU(Telecom office): 5,37E-14 RV(Telecom office): 1,07E-08 RW(Telecom office): 5,37E-08 RZ(Telecom office): 7,46E-07 Total: 3,81E-06 Z3: Production RB: 1,10E-07 RC: 3,29E-07 RM: 1,74E-06 RU(Power production): 4,89E-14 RV(Power production): 9,77E-10 RW(Power production): 1,47E-08 RZ(Power production): 4,68E-07 RU(Telecom production): 5,37E-13 RV(Telecom production): 1,07E-08 RW(Telecom production): 1,61E-07 RZ(Telecom production): 2,24E-06 Total: 5,08E-06 Value of total risk R1 for the structure: 9,00E-06 For SPD selection see Appendix SPD selection. 7.1 Economic analysis The economic analysis between different cases of protecion measures is done according to standard EN 62305-2 in order to select the best case. The economic values related to the structure are listed below: - Z1 - External Structure (CB): € 20.000,00 Added value for the structure (CC): € 1.000,00 - Z2 - Office Structure (CB): € 2.500.000,00 Added value for the structure (CC): € 800.000,00 Equipments value - internal system Power office (CS): € 150.000,00 Equipments value - internal system Telecom office (CS): € 300.000,00 - Z3 - Production Structure (CB): € 4.000.000,00 Added value for the structure (CC): € 4.500.000,00 Equipments value - internal system Power production (CS): € 300.000,00 Equipments value - internal system Telecom production (CS): € 500.000,00 The cost of protection measures are listed below. Cost of common protection measures (LPS + SPD at entrance line): € 28.700,00 Z2 - Office - Internal system: Power office Coordinated SPD - level: II- cost: € 7.000,00 - Internal system: Telecom office Coordinated SPD - level: I- cost: € 8.500,00 Z3 - Production - Internal system: Power production Coordinated SPD - level: I- cost: € 6.450,00 - Internal system: Telecom production Coordinated SPD - level: I- cost: € 4.500,00 The values for interest rate, amortisation and maintenance rate are listed below: - Interest rate: 4 % - Amortisation: 10 years - Manteinance rate: 1 % The values of risk components related to R4 for the unprotected structure are listed below: Z2: Office RB: 4,96E-05 RC(Power office): 2,20E-03 RM(Power office): 1,72E-02 RV(Power office): 1,71E-05 RW(Power office): 7,58E-04 RZ(Power office): 1,23E-02 RC(Telecom office): 2,20E-03 RM(Telecom office): 2,29E-06 RV(Telecom office): 4,83E-05 RW(Telecom office): 2,15E-03 RZ(Telecom office): 4,48E-03 Z3: Production RB: 1,87E-05 RC(Power production): 1,10E-04 RM(Power production): 1,15E-03 RV(Power production): 1,22E-06 RW(Power production): 7,15E-06 RZ(Power production): 6,34E-05 RC(Telecom production): 1,10E-04 RM(Telecom production): 1,15E-07 RV(Telecom production): 1,83E-05 RW(Telecom production): 1,07E-04 RZ(Telecom production): 2,24E-04 Total value of risk R4 for the structure: 6,83E-05 The cost of residual loss (CRL) is calculated according to appendix G of EN 62305-2 standard using the new values that risk R4 components have after the protection measures are applied in the selected cases. The cost of loss for unprotected structure (CL) and the total cost of residual loss in spite of protection measures (CRL) for all the cases are listed below. Zone Z1 - External Cost without protection: € 0,00 Cost with protection: € 0,00 Cost of protection measures: € 0,00 Saving: € 0,00 Zone Z2 - Office Cost without protection: € 7.945,00 Cost with protection: € 294,71 Cost of protection measures: € 2.325,00 Saving: € 5.325,29 Zone Z3 - Production Cost without protection: € 974,14 Cost with protection: € 32,62 Cost of protection measures: € 1.642,50 Saving: € -700,98 Cost LPS and SPD at entrance line: € 4.305,00 Total cost without protection: € 8.919,14 Total cost with protection: € 327,33 Total cost of protection measures: € 8.272,50 Total saving: € 319,31 8. CONCLUSIONS After protection measures (that must be correctly designed) are applied, risk assessment is: Risk lower than tolerable risk: R1 ACCORDING TO STANDARD EN 62305-2 THE STRUCTURE IS PROTECTED AGAINST LIGHTNING. Date 24/10/2006 Rubber stamp and signature 9. APPENDICES APPENDIX - Structure type Dimensions: refer to Annex Location factor: surrounded by smaller objects (Cd = 0,5) Structure shield: No shield Lightning flashes frequency (1/km² year) Ng = 2 APPENDIX - Electrical lines characteristics Line characteristics: Power aerial The whole line has uniform characteristics. Type of line: power - aerial Length (m) Lc = 780 Height above ground (m) Hc = 6 Location factor (Cd): surrounded by higher objects Environmental factor (Ce): suburban (h < 10 m) Adjacent structure dimensions: A (m): 10 B (m): 15 Location factor for adjacent structure (Cd): isolated H (m): 8 Line characteristics: Power mixed Type of line: power Structure's height where the incoming line gets inside (m): 12 The line has more than one section. Section 1 Buried section Length (m) Lc = 200 Resistivity (ohm x m) = 400 Location factor (Cd): surrounded by higher objects Environmental factor (Ce): suburban (h < 10 m) Shielding (ohm/km ) connected to the same equipotential bar of equipment: R <= 1 ohm/km Section 2 Transformer HV/LV Section 3 Aerial section Length (m) Lc = 400 Height above ground (m) Hc = 6 Location factor (Cd): surrounded by smaller objects Environmental factor (Ce): suburban (h < 10 m) Section 4 Adjacent structure Adjacent structure dimensions: A (m): 10 B (m): 15 H (m): 7 Location factor for adjacent structure (Cd): surrounded by smaller objects Line characteristics: Telecom The whole line has uniform characteristics. Type of line: TLC - aerial Length (m) Lc = 800 Height above ground (m) Hc = 6 Location factor (Cd): isolated Environmental factor (Ce): suburban (h < 10 m) Shielding (ohm/km ) connected to the same equipotential bar of equipment: 5 < R <= 20 ohm/km APPENDIX - Zones characteristics Zone characteristics: External Zone type: outside Type of surface: Grass (ra = 0,01) Protection measures to reduce the touch and step voltages: no protection measures Zone characteristics: Office Zone type: inside Type of surface: Linoleum (ru = 0,00001) Risk of fire: ordinary (rf = 0,01) Special hazard: Low panic level (h = 2) Fire protections: manually operated (rp = 0,5) Zone shielding: No shield Protection against touch voltage: no protection measures Internal system: Power office Connected to line Power aerial Wiring: Loop area in the order of 10 m² (Ks3 = 0,2) Withstand voltage: 2,5 kV Coordinated SPD - level: none (Pspd =1) Internal system: Telecom office Connected to line Telecom Wiring: shielded cable 1 < R <= 5 ohm/km (Ks3 = 0,0002) Withstand voltage: 1,5 kV Coordinated SPD - level: none (Pspd =1) Mean loss value for the zone: Office Loss due to touch and step voltage (related to R1) Lt = 0,00001 Loss due to physical damage (related to R1) Lf = 0,002 Loss due to failure of internal systems (related to R1) Lo = 0,0001 Loss due to physical damage (related to R4) Lf = 0,09 Loss due to failure of internal systems (related to R4) Lo = 0,04 Risk and risk components for the structure: Office Risk 1: Rb Rc Rm Ru Rv Rw Rz Risk 4: Rb Rc Rm Rv Rw Rz Zone characteristics: Production Zone type: inside Type of surface: Linoleum (ru = 0,00001) Risk of fire: ordinary (rf = 0,01) Special hazard: Average panic level (h = 5) Fire protections: automatically operated (rp = 0,2) Zone shielding: No shield Protection against touch voltage: no protection measures Internal system: Power production Connected to line Power mixed Wiring: Loop area in the order of 50 m² (Ks3 = 1) Withstand voltage: 2,5 kV Coordinated SPD - level: none (Pspd =1) Internal system: Telecom production Connected to line Telecom Wiring: shielded cable 1 < R <= 5 ohm/km (Ks3 = 0,0002) Withstand voltage: 1,5 kV Coordinated SPD - level: none (Pspd =1) Mean loss value for the zone: Production Loss due to touch and step voltage (related to R1) Lt = 0,0001 Loss due to physical damage (related to R1) Lf = 0,002 Loss due to failure of internal systems (related to R1) Lo = 0,0003 Loss due to physical damage (related to R4) Lf = 0,034 Loss due to failure of internal systems (related to R4) Lo = 0,002 Risk and risk components for the structure: Production Risk 1: Rb Rc Rm Ru Rv Rw Rz Risk 4: Rb Rc Rm Rv Rw Rz APPENDIX - Collection areas and number of annual dangerous events. Structure Collection area due to direct flashes to the structure Ad = 5,51E-02 km² Collection area due to flashes near the structure Am = 3,14E-01 km² Annual number of dangerous events due to direct flashes to the structure Nd = 5,51E-02 Annual number of dangerous events due to flashes near the structure Nm = 5,73E-01 Electrical lines Collection area due to direct flashes (Al) and to flashes near (Ai) to the lines: Power aerial Al = 0,025272 km² Ai = 0,780000 km² Power mixed Al = 0,016924 km² Ai = 0,500000 km² Telecom Al = 0,026856 km² Ai = 0,800000 km² Annual number of dangerous events due to direct flashes (Nl) and to flashes near (Ni) to the lines: Power aerial Nl = 0,012636 Ni = 0,780000 Power mixed Nl = 0,004369 Ni = 0,180000 Telecom Nl = 0,053712 Ni = 0,800000 APPENDIX - Values of probability of damage for unprotected structure Zone Z1: External Pa = 1,00E+00 Pb = 1,0 Pc = 1,00E+00 Pm = 1,00E+00 Zone Z2: Office Pa = 1,00E+00 Pb = 1,0 Pc (Power office) = 1,00E+00 Pc (Telecom office) = 1,00E+00 Pc = 1,00E+00 Pm (Power office) = 7,50E-01 Pm (Telecom office) = 1,00E-04 Pm = 7,50E-01 Pu (Power office) = 1,00E+00 Pv (Power office) = 1,00E+00 Pw (Power office) = 1,00E+00 Pz (Power office) = 4,00E-01 Pu (Telecom office) = 1,00E+00 Pv (Telecom office) = 1,00E+00 Pw (Telecom office) = 1,00E+00 Pz (Telecom office) = 1,50E-01 Zone Z3: Production Pa = 1,00E+00 Pb = 1,0 Pc (Power production) = 1,00E+00 Pc (Telecom production) = 1,00E+00 Pc = 1,00E+00 Pm (Power production) = 1,00E+00 Pm (Telecom production) = 1,00E-04 Pm = 1,00E+00 Pu (Power production) = * Pv (Power production) = * Pw (Power production) = * Pz (Power production) = * Pu (Telecom production) = 1,00E+00 Pv (Telecom production) = 1,00E+00 Pw (Telecom production) = 1,00E+00 Pz (Telecom production) = 1,50E-01 (*) In case of lines with different sections, the probability refers to each section. See Appendix Electrical lines characteristics. APPENDIX - SPD selection It is assumed that a cascade of SPD (if present) is coordinated (installed as required by the manufacturer's instructions). In this case the selection of SPD is required for the following lines: L1 - Power aerial L2 - Power mixed L3 - Telecom LINE L1 - Power aerial General data The electrical installation is a TN system. The line that supplies the main board is three phase + neutral and phase to neutral voltage is 230 V. Overvoltages due to direct flashes to the structure are considered. It is assumed a safety coefficient b = 0,9 Lightning current that flows in each line conductor is 5,68 kA (resistivity of soil : 500 ohm x m number of entering services : 5). Installation structure The structure of low voltage electrical installation, considered for selection of protection measures against overvoltages, is reported in Annex Structure installation (**** provided by designer ****). The main characteristics of installation are listed below. Main board Short-circuit current : 10 kA The Main board supplies the following boards : Board (2° level) - Distance : 45 m - Wiring : loop area 0,5 m² - Type : three phase + neutral The Main board directly supplies (without intermediate boards) some terminal circuit. All final circuits have the same withstand voltage (2500 V), therefore to select protection measures it is considered the circuit with the worst characteristics : Final circuit n° 1 - Distance from Main board : 22 m - Wiring : loop area 0,5 m² - Type of line : three phase + neutral Board (2° level) The Board (2° level) directly supplies (without intermediate boards) some terminal circuit. All final circuits have the same withstand voltage (2500 V), therefore to select protection measures it is considered the circuit with the worst characteristics : Final circuit n° 1 - Distance from Board (2° level) : 2 m - Wiring : shielded cable R <= 1 ohm/km - Type of line : phase - neutral Protection measures selection The selected protection measures are described for each board. Main board On Main board, supplied by a line three phase + neutral, SPD are installed at the board entrance (upstream of circuit breaker or residual current device), with the following characteristics : level : I class : I type: varistor protection level Up : 1000 V length of connecting conductors : 0,2 m effective protection level Up/f : 1200 V max continuous operating voltage Uc : 253 V impulse current Iimp : 10 kA short-circuit current with or without fuse : 10 kA The installed SPD protects this board. The installed SPD protects final circuits / equipments according the following table: Length (m) Uw (V) lpo (m)lpi (m) Protected coeff. Main board - Final circuit n° 1 0,7 Board (2° level) - Final circuit n° 1 - 22 2500 42 49,1 Si 47 2500 42 51,3 No To select protection measures it is considered, for each withstand voltage, the circuit with the worst characteristics. Because this circuit is protected, are protected also all the circuits supplied by Main board. Final circuits protected by SPD SPD of class II (In >= 5 kA) or class III (Uoc >= 10 kV) are provided on the following circuits : Board (2° level) - Final circuit n° 1 - Up/f required for the SPD : 2250 V SPD coordination The installed SPD are coordinated. The protection against overvoltages is completed. The lengths of final circuits supplied by boards without SPD (for which the circuits with worst Eff. characteristics are protected directly by SPD), infact, have lengths lower than the one reported in Annex B. ANNEX B It is necessary to verify that final circuits supplied by the following boards have length lower than the one reported in table (distance in meters). The table reports the lower length between the protection distance lpo (oscillation phenomenon) and protection distance lpi (induction phenomenon). Board (2° level) Wiring Loop area in the order of 50 m²" Loop area in the order of 10 m²" Loop area in the order of 0,5 m²" Shielded cable R <= 1 ohm/km Shielded cable 1 < R <= 5 ohm/km Shielded cable 5 < R <= 20 ohm/km Withstand voltage (V) 1500 2500 4000 0 0 0 0 0 0 0 0 0 6000 0 1,3 3 0 6,7 15,1 0 67,2 151,3 > 10000 > 10000 > 10000 > 10000 1343,8 3026,6 LINE L2 - Power mixed General data The electrical installation is a TN system. The line that supplies the main board is three phase + neutral and phase to neutral voltage is 230 V. Overvoltages due to direct flashes to the structure are considered. The earth electrode of building and transformer HV/LV are not connected. It is assumed a safety coefficient b = 0,9 Lightning current that flows in each line conductor is 3,37 kA (resistivity of soil : 500 ohm x m number of entering services : 5). The connected line is shielded (S = 10 mm2 in copper) and the distance between the structure and the closest earthing point of the screen is 60 m. The minimum withstand voltage of installed equipment: 2500 (V). The cross-section of connected line is 20 mm². Installation structure The structure of low voltage electrical installation, considered for selection of protection measures against overvoltages, is reported in Annex Structure installation (**** provided by designer ****). The main characteristics of installation are listed below. Main board Short-circuit current : 12 kA The Main board supplies the following boards : Board (2° level) - Distance : 23 m - Wiring : shielded cable 1 < R <= 5 ohm/km - Type : three phase + neutral The Main board directly supplies (without intermediate boards) some terminal circuit. All final circuits have the same withstand voltage (2500 V), therefore to select protection measures it is considered the circuit with the worst characteristics : Final circuit n° 1 - Distance from Main board : 22 m - Wiring : shielded cable R <= 1 ohm/km - Type of line : three phase + neutral Board (2° level) The Board (2° level) supplies the following boards : Board (3° level) - distance : 33 m - Wiring : shielded cable R <= 1 ohm/km - Type : three phase + neutral Board (3° level) The Board (3° level) supplies the following boards : Board (4° level) - distance : 22 m - Wiring : shielded cable R <= 1 ohm/km - Type : phase - neutral The Board (3° level) directly supplies (without intermediate boards) some terminal circuit. All final circuits does not have the same withstand voltage, therefore to select protection measures it is considered, for each withstand voltage, the circuit with the worst characteristics : Final circuit n° 1 - Impulse withstand voltage : 2500 (V). - Distance from Board (3° level) : 12 m - Wiring : shielded cable 1 < R <= 5 ohm/km - Type of line : phase - neutral Final circuit n° 2 - Impulse withstand voltage : 4000 (V). - Distance from Board (3° level) : 27 m - Wiring : shielded cable R <= 1 ohm/km - Type of line : three phase + neutral Board (4° level) The Board (4° level) directly supplies (without intermediate boards) some terminal circuit. All final circuits have the same withstand voltage (2500 V), therefore to select protection measures it is considered the circuit with the worst characteristics : Final circuit n° 1 - Distance from Board (4° level) : 22 m - Wiring : shielded cable R <= 1 ohm/km - Type of line : phase - neutral Protection measures selection The selected protection measures are described for each board. Main board On Main board, supplied by a line three phase + neutral, SPD are installed at the board entrance (upstream of circuit breaker or residual current device), with the following characteristics : level : I class : I type: varistor protection level Up : 1000 V length of connecting conductors : 0 m effective protection level Up/f : 1000 V max continuous operating voltage Uc : 253 V impulse current Iimp : 5 kA short-circuit current with or without fuse : 12 kA The installed SPD protects this board. The installed SPD protects final circuits / equipments according the following table: Length (m) Uw (V) lpo (m) lpi (m) Eff. coeff. Main board - Final circuit n° 1 Board (3° level) - Final circuit n° 1 - Final circuit n° 2 Board (4° level) - Final circuit n° 1 - Protected 22 2500 *** --- Si 68 2500 *** --- Si 83 4000 *** --- Si 100 2500 *** --- Si *** Up/f <= bUw / 2 and/or circuit length is lower than 10 m, therefore it is not ncessary to evaluate the oscillation protection distance (lpo). --- It is not necessary to evaluate the induction protection distance (lpi). To select protection measures it is considered, for each withstand voltage, the circuit with the worst characteristics. Because this circuit is protected, are protected also all the circuits supplied by Main board. Final circuits protected by SPD SPD are not provided on the final circuits. The protection against overvoltages is completed. Cross-section of connecting conductors for SPD The minimum cross-section of connecting conductors for SPD is: Class I : 6 mm2 Class II : 4 mm2 Class III : 1,5 mm2 In any case, for SPD class I, the cross-section of connecting conductors (S) should respect the following relation: S >= Iimp / 8 for PVC connecting conductors S >= Iimp / 10 for EPR connecting conductors The layout of SPD installation is reported in Annex "SPD installation".