GB/T 21714.2-2026Protection against lightning - Part 2: Risk management (English PDF)

1 Scope 1

2 Normative References 1

3 Terms and Definitions 2 4 symbols 8

5 Damage and Loss 11

6 Risks and Risk Components 12

8 Risk Component Assessment 17

9 Frequency and Components of Damage 21

Appendix A (Informative) Estimation of the Annual Average Number of Hazardous Events (NX) 25

Appendix B (Informative) Estimation of Probability of Damage (PX) 33

Appendix C (Informative) Estimation of Various Loss Rates (LX) in Buildings 45

Appendix D (Informative) Estimation of PSPD 48

Appendix E (Informative) Detailed Analysis of Additional Loss Rates (LE) Related to the Surrounding Environment 60

Appendix F (Informative) Example 63 of Building Assessment

References 87

Figure 1.Flowchart for determining protection requirements and selecting protection measures to ensure R <= RT.

Figure 2.Example 20 of risk zoning

Figure 3.Flowchart for determining protection requirements and selecting protection measures to ensure F<=FT.23

Figure A.1 Equivalent lightning interception area (AD) of an isolated building 26

Figure A.2 Buildings with complex shapes 27

Figure A.3 Determining the cut-off area of a given building using different methods 27

Figure A.4 Calculation of the cut-off area (AD) of a portion of a building 28

Figure A.5 Equivalent interception area (AD, ADJ, AM, AL, and AI) 32

Figure D.1 Discharge probability of the first return stroke for positive and negative polarities 49

Figure D.2 The probability PUp corresponding to the 1kA residual voltage Up' of the SPD is 51

Figure D.4 The probability PUp corresponding to the 1kA residual voltage Up' of SPD2 is 52

Figure D.5 The probability PUp corresponding to the 1kA residual voltage Up' of SPD2 is 53

Figure D.6 shows the probability PUp corresponding to the 1kA residual voltage Up'.

Figure D.7 Probability PUp corresponding to the internal circuit length 54

Figure D.8 Probability PUp corresponding to the internal circuit length 55

Figure D.9 The probability PUp corresponding to the 1kA residual voltage Up' of SPD2 is 56.

Figure D.10 shows the probability PUp corresponding to the area of the internal loop when n'=2 and w=0.1m.

Figure D.11 shows the probability PUp corresponding to the internal loop area when n'=2 and w=0.5m.

Figure D.12 shows the probability PUp corresponding to the internal loop area when n'=2 and w=0.1m.

Figure D.13 Probability PUp corresponding to the 1kA residual voltage Up' of the SPD under different internal loop areas.

Figure D.14 Probability PUp corresponding to different internal loop areas under two typical protection levels of GDT 59

Table 1.Comparison of Damage Sources, Causes, Loss Types, and Risk Components for Different Lightning Strike Points (Table 13)

Table 2 Factors Affecting Risk Components 14

Table 3 lists the risk components by source of damage and type of loss.

Table 4.Frequency components of various damage sources 22

Table A.1 Location factors CD and CDJ of buildings 29

Table A.2 Line Installation Factor (CI) 30

Table A.3 Line Type Factor (CT) 31

Table A.4 Line Environmental Factor (CE) 33

Table B.2 Reduction Factors (rt) Related to Soil or Floor Surface Type 34

Table B.3 PLPS values related to direct lightning strike protection and physical damage reduction measures in exposed areas of buildings 35

Table B.4 Probability of Dangerous Sparks Caused by Lightning Strike on Buildings (PS) 36

Table B.5 Reduction Factors (rp) Related to Fire Prevention Measures 36

Table B.6 Reduction Factor (rf) Related to Building Fire or Explosion Risk 36

Table B.7 Typical PSPD values for SPDs used to protect against damage sources S1, S2, S3, and S4 in low-voltage systems (37)

Table B.8 Typical PSPD values of SPDs used to protect against damage sources S1, S2, S3, and S4 in communication systems 38

Table B.9 CLD and CLI values related to shielding, grounding, and isolation conditions 39

Table B.10 KS3 values related to internal wiring type 41

Table B.11 PLD values related to the resistance (RS) of the cable shield per unit length and the rated impulse withstand voltage (UW) of the equipment 42

Table B.12 PLD values related to the resistance (RS) of the cable shield per unit length and the higher equipment rated impulse withstand voltage (UW) 42

Table B.13 Typical PEB values corresponding to the Lightning Protection Level (LPL) of the SPD designed to withstand damage source S3.42

Table C.1 Loss rate values for each partition 45

Table C.2 Typical average values of LT, LD, LF1, LF2, LO1, and LO2 46

Table D.1 PUp value of voltage-limited SPD in the combination of voltage-limited SPD and voltage-switching SPD 52

Table D.2 PUp values of voltage-limited SPDs 55

Table E.1 Risk Components for Different Damage Sources and Loss Types (Applicable to Damage to the Surrounding Environment) 60

Table E.2 Loss Type L1.Typical Recommended Values for Personnel On-Site Time (tzE/8760) in Different Environments (Applicable to those specified in Table E.2)

(Environment type) 61

Table E.4 Loss Type L2.Typical Average Values of LF2E and LO2E Outside Buildings 62

Table F.1 Residential Buildings. Environmental and Building Characteristics 63

Table F.2 Residential Buildings. Power Supply Line 64

Table F.3 Residential. Communication Line 64

Table F.4 Residential Buildings. Equivalent Cut-off Area of Buildings and Lines 65

Table F.5 Residential. Expected average annual number of hazardous events 65

Table F.6 Residential Buildings. Risk Components of Personnel Stay Time and Risk Zoning 66

Table F.7 Residential. Z2 Zone (Building Interior) Value 66

Table F.8 Residential Buildings. Risk of Unprotected Structures (Value × 10-5) 67

Table F.9 Residential Buildings. Risk Components of Protected Buildings (Value × 10-5) 68

Table F.10 Office Buildings. Environmental and Building Characteristics 68

Table F.11 Office Building. Power Supply Line 69

Table F.12 Office Building. Communication Line 69

Table F.13 Office Buildings. Equivalent intercepted area of buildings and lines 70

Table F.14 Office Buildings. Estimated Average Annual Number of Hazardous Events 70

Table F.15 Office Building. Personnel Stay Time and Risk Components of Risk Zones 71

Table F.16 Office Building. Value 71 applicable to Zone Z1 (outside the entrance area)

Table F.17 Office Buildings. Value 72 applicable to Zone Z2 (Rooftop)

Table F.18 Office Building. Value 73 applicable to Zone Z3 (Archives)

Table F.20 Office Building. Value 74 applicable to Zone Z5 (Computer Center)

Table F.21 Office Buildings. Risk of Unprotected Structures (Value × 10-5) 75

Table F.22 Office Buildings. Damage Frequency of Unprotected Buildings 75

Table F.23 Office Buildings. Risk Components with Protective Buildings (Value × 10-5) 76

Table F.24 Office Buildings. Frequency of Damage to Protected Buildings 76

Table F.25 Hospitals. Environmental and Architectural Characteristics 77

Table F.26 Hospital. Power Supply Line 77

Table F.27 Hospitals. Equivalent interception area of buildings and power lines 78

Table F.28 Hospitals. Estimated average number of hazardous events per year. 78

Table F.29 Hospitals. Personnel Stay Time and Risk Components of Risk Zones 80

Table F.30 Hospital. Value 80 applicable to Zone Z1 (outside the entrance area)

Table F.31 Hospital. Value 80 applicable to Zone Z2 (Rooftop)

Table F.32 Hospital. Value 81 applicable to Zone Z3 (Room Zone)

Table F.33 Hospital. Value 82 applicable to Zone Z4 (Surgical Area)

Table F.34 Hospital. Value 83 applicable to Zone Z5 (Intensive Care Unit)

Table F.35 Hospitals. Risk of Unprotected Buildings (Value × 10-5) 83

Table F.36 Hospitals. Frequency of damage to unprotected buildings 84

Table F.37 Hospitals. Risk Components with Protective Buildings (Value × 10-5) 85

Table F.38 Hospitals. Damage frequency of protected buildings 85

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document is Part 2 of GB/T 21714 "Lightning Protection". GB/T 21714 has the following parts published.

---Part 1: General Provisions;

---Part 2: Risk Management;

---Part 3: Physical Damage to Buildings and Life Hazards;

---Part 4: Electrical and Electronic Systems within Buildings.

This document replaces GB/T 21714.2-2015 "Lightning Protection Part 2: Risk Management" and is consistent with GB/T 21714.2-2015.

Compared to previous versions, aside from structural adjustments and editorial changes, the main technical changes are as follows.

a) The scope of application has been changed (see Chapter 1, Chapter 1 of the 2015 edition);

b) Some terms and definitions have been changed (see Chapter 3, Chapter 3 of the 2015 edition);

c) Modified damages and losses (see Chapter 5, 4.1 of the 2015 edition);

d) Risks and risk components have been changed (see Chapter 6, 4.2 of the 2015 edition);

e) The term "risk management" was changed to "risk assessment," and the corresponding provisions were amended (see Chapter 7, Chapter 5 of the 2015 edition);

f) The assessment of risk components has been changed (see Chapter 8, Chapter 6 of the 2015 edition);

g) Increased the frequency and components of damage (see Chapter 9).

This document is equivalent to IEC 62305-2:2024 "Lightning protection - Part 2: Risk management".

The following minimal editorial changes have been made to this document.

---Notes have been added to the "Scope" chapter, sections 3.10 and 3.51, to facilitate understanding of the document;

---Added corresponding English terms (see 3.19);

---Change the informative content in the definition to a note (see 3.19, 3.20);

---The positions of PSPD, rM, and RS annotations have been corrected, and the missing symbol rI and its definition have been added (see Chapter 4);

---Changing "×" to "sqrt" better aligns with usage habits in my country (see Tables 2, F.6, F.15, and F.29);

---The meaning of L1 has been corrected (see Table 3 and Table E.1);

---The phrase "typical value of risk tolerance" should be corrected to "typical value of damage frequency tolerance" (see note 1 in 9.3);

---The title of Figure 3 has been corrected, adding the statement "make F<=FT";

---The formula number has been corrected (see Figure A.3);

---The content of IEC 62305-2:2024/COR1.2024 has been incorporated, and the formula has been corrected [see formula (D.6)].

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed and is under the jurisdiction of the National Technical Committee on Lightning Protection Standardization (SAC/TC258).

Introduction

GB/T 21714 "Lightning Protection" aims to propose lightning protection (LP) measures to effectively reduce lightning risks, and is proposed to consist of four parts.

---Part 1: General Provisions. The purpose is to stipulate the general principles to be followed for lightning protection of buildings and their facilities, internal objects, and personnel.

in principle.

---Part 2: Risk Management. The purpose is to define the process for managing lightning risk in buildings, including calculating the building's lightning strike risk.

Value. After selecting the upper limit of risk tolerance, this process allows for the selection of appropriate protective measures to reduce the risk to the tolerance limit or above.

The following also includes assessing the frequency of damage to internal systems caused by lightning surges. After selecting an upper limit for the acceptable frequency of damage, this process is followed.

Choose appropriate protective measures to reduce the frequency of damage to or below the permissible limit.

---Part 3: Physical Damage to Buildings and Life Hazards. The purpose is to specify lightning protection measures for physical damage to buildings.

Requirements for protection systems (LPS) and requirements for preventing personal injury from contact voltage and step voltage near the LPS.

---Part 4: Electrical and Electronic Systems within Buildings. The purpose is to specify surge protection measures for electrical and electronic systems within buildings.

The design, installation, inspection, maintenance, and testing requirements for (SPM) are designed to reduce permanent failures caused by lightning electromagnetic pulses (LEMP).

risk.

Lightning strikes to the ground can damage buildings and their power lines.

This harm may lead to.

---Damage to the building and its interior objects;

---Failure of related electrical and electronic systems;

Damage to buildings and their interior objects, as well as the consequences of electrical and electronic system failures, can affect objects surrounding the building or its own environment.

Furthermore, regardless of the extent of the damage, if the frequency of damage is high, the availability of the building and its internal systems will be unacceptably compromised.

damage.

To reduce the frequency and extent of damage caused by lightning strikes, protective measures may be necessary. A damage frequency and risk assessment should be conducted to determine this.

Determine whether protective measures are needed and to what extent.

Note 1.Regardless of the frequency of damage or the results of the risk assessment, a decision can be made to provide lightning protection if the goal is to prevent avoidable damage.

Note 2.IEC 60364-4-44 stipulates that a surge protector must always be installed at the power supply line inlet of a building when the consequences of overvoltage affect the following scenarios.

Protector (SPD).

---Human life care, such as security services and medical facilities;

---Public services and cultural heritage, such as public services, information centers, museums, etc.;

---Commercial or industrial activities, such as hotels, banks, factories, shopping malls, farms, etc.

This document defines damage frequency as the number of damage events that a protected building's internal systems may suffer in a year, depending on.

---The average number of lightning strikes that affect buildings per year;

---The probability of a single, impactful lightning strike causing damage.

This document defines risk as the average annual potential loss to a building or a section of a building caused by a lightning strike, depending on.

---Frequency of damage;

---The average extent of loss caused by a single incident.

The following types of lightning can affect buildings.

---Lightning strikes a building;

Lightning strikes on buildings or connected wiring can cause physical damage and personal injury. Not only can lightning strikes on buildings or wiring cause...

The failure of electrical and electronic systems, and lightning strikes near buildings or lines can also cause resistive coupling between the lightning current and these systems, as well as electrical...

Overvoltages caused by inductive coupling can lead to the failure of electrical and electronic systems.

In addition, failure of user electrical equipment and power supply lines due to lightning overvoltage can also lead to operational overload in the electrical equipment.

Voltage.

Note 3.GB/T 21714 (all parts) does not cover the problem of electrical and electronic systems malfunctioning due to interference. For interference issues, see GB/T 17626.5-2019.

The number of lightning strikes that affect a building depends not only on the density of lightning strike points in the area, but also on the size and characteristics of the building and its wiring.

The quality and environment. See Appendix A for guidelines on assessing the impact of lightning strikes on buildings.

The probability of damage depends not only on the type and effectiveness of the protective measures taken, but also on the tolerance level of the building and the equipment within it.

Characteristics of the line and lightning current. See Appendix B for guidelines on assessing the probability of damage.

The average annual extent of loss caused by each lightning strike depends on the severity of the damage and its potential consequences. A single strike causes...

For guidelines on assessing the average extent of loss, see Appendix C.

The effectiveness of protection depends on the characteristics of each protective measure; protection can reduce the probability of damage.

Note 4.It is assumed that the protective measures are implemented with the necessary quality.

The protective measures are intended to comply with the requirements of GB/T 21714 (all parts), IEC 61643 (all parts) and IEC 62793, if applicable.

Note 5.For complex buildings, such as petrochemical plants and large industrial facilities, the parameters described in the appendix of this document need to be further refined based on the characteristics of the building.

Evaluate.

National or local laws and regulations provide guidance or stipulate minimum requirements for the application of this document, including determining the risk tolerance (RT) and damage.

Frequency tolerance (FT), and the calculation rules and parameter values given in Appendices A through C and Appendices E.

1 Scope

This document outlines the procedures for managing lightning risks in buildings, including.

---Calculate the lightning strike risk value of a building. After selecting the upper limit of the risk tolerance, choose appropriate protective measures through this process to mitigate the risk.

Reduce to or below the permissible limit;

---Assess the frequency of damage to internal systems caused by lightning surges. After selecting an upper limit for the allowable frequency of damage, select an appropriate [system/mechanism] through this process.

Protective measures will reduce the frequency of damage to or below the permissible limit.

This document applies to lightning risk management for buildings.

Note. In this document, "buildings" refers to any structure or building.

2 Normative references the contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 21714.1-2026 Lightning protection – Part 1: General principles (IEC 62305-1:2024, IDT) GB/T 21714.3-2026 Lightning Protection - Part 3: Physical Damage to Buildings and Hazards to Life (IEC 62305-3) 2024, IDT) GB/T 21714.4-2026 Lightning protection – Part 4: Electrical and electronic systems in buildings (IEC 62305-4:2024, IDT) Note. GB/T 18802.11-2020 Low-voltage surge protectors (SPDs) Part 11: Performance requirements and tests for surge protectors in low-voltage power systems Method (IEC 61643-11:2011, MOD) GB/T 18802.12-2024 Low-voltage surge protectors (SPDs) Part 12: Guidelines for the selection and use of surge protectors in low-voltage power systems GB/T 18802.21-2016 Low-voltage surge protectors – Part 21: Surge protectors (SPDs) for telecommunications and signaling networks – Performance requirements and testing Test method (IEC 61643-21:2012, IDT) GB/T 18802.22-2019 Low-voltage surge protectors - Part 22: Guidelines for selection and use of surge protectors for telecommunications and signaling networks (IEC 61643-22:2015, IDT) GB/T 18802.31-2021 Low-voltage surge protectors - Part 31: Performance requirements and test methods for surge protectors used in photovoltaic systems (IEC 61643-31:2018, IDT) GB/T 18802.32-2021 Low-voltage surge protectors - Part 32: Guidelines for selection and use of surge protectors for photovoltaic systems (IEC 61643-32:2017, IDT) GB/T 18802.311-2017 Low-voltage surge protector components - Part 311: Performance requirements and test circuits for gas discharge tubes (GDTs) (IEC 61643-311:2013, IDT) GB/T 18802.312-2017 Low-voltage surge protector components - Part 312: Guidelines for selection and use of gas discharge tubes (GDTs) (IEC 61643-312:2013, IDT) GB/T 18802.321-2007 Low-voltage surge protector components - Part 321: Avalanche breakdown diodes (ABD) specification (IEC 61643-321.

2001, IDT)