IEC 62305-2-2024 PDF

Full title and description

St IEC 62305-2-2024 — Protection against lightning — Part 2: Risk management. International standard giving the procedure for evaluation of the risk to structures due to lightning and for selection of protection measures to reduce that risk to an acceptable level.

Abstract

This third edition (2024) revises the risk-management methodology for lightning protection. It updates calculation inputs and introduces new concepts including a single combined risk metric (combining loss of life and fire), the lightning ground strike‑point density (NSG) replacing the former flash density (NG), the concept of frequency of damage affecting internal system availability, and allowance for preventive temporary measures activated by thunderstorm warning systems (TWS, IEC 62793). The edition cancels and replaces IEC 62305-2:2010 and includes Corrigendum 1 (2024).

General information

• Status: Current / Valid (third edition).
• Publication date: 12 September 2024.
• Publisher: International Electrotechnical Commission (IEC).
• ICS / categories: 29.020; 91.120.40.
• Edition / version: Edition 3.0 (2024).
• Number of pages: 256.

Scope

Specifies a procedure for evaluating the risk to structures and their contents arising from lightning flashes to earth and for identifying protection measures (lightning protection systems, surge protective devices, bonding, organizational and temporary measures) required to reduce that risk below a chosen tolerable limit. The standard covers evaluation of expected annual number of dangerous events using updated density data (NSG), partitioning of structures into risk zones, treatment of different damage sources, and incorporation of temporary preventive measures such as TWS.

Key topics and requirements

• Formal risk assessment procedure for structures: calculation of expected annual number of dangerous events and resulting risk.
• Introduction of the single risk concept (combined human-life and fire losses) and the frequency-of-damage concept for internal-system availability.
• Use of lightning ground strike‑point density (NSG) in risk calculations.
• Partitioning structures into zones, lines and sections for detailed assessments.
• Guidance for selecting protection measures: external LPS (air‑termination, down-conductors, earthing), equipotential bonding and internal surge protective devices (SPDs).
• Consideration of preventive temporary measures using thunderstorm warning systems (TWS) compliant with IEC 62793 to reduce certain risk components.
• Documentation, verification and maintenance requirements for implemented protection measures.

Typical use and users

Used by lightning protection designers and engineers, building and facility safety managers, electrical consultants, utilities, industrial plant operators, insurers assessing lightning-related risk, and standards committees. It serves as the reference for designing and justifying lightning protection and surge mitigation strategies for buildings, critical infrastructure and external installations.

Related standards

Part of the IEC 62305 series (Parts 1–4). Relevant associated documents include IEC 62305-1, IEC 62305-3, IEC 62305-4, IEC 62793 (thunderstorm warning systems), the IEC 61643 series (surge protective devices) and other normative references for surge/immunity and earthing practices used in lightning protection design.

Keywords

lightning protection, risk management, lightning strike density, NSG, thunderstorm warning system, TWS, surge protection, equipotential bonding, lightning protection system (LPS), risk assessment, IEC 62305.

FAQ

Q: What is this standard?

A: IEC 62305-2:2024 is the Part 2 international standard of the IEC 62305 series that defines the risk‑management procedure for protection of structures against lightning.

Q: What does it cover?

A: It covers methods to calculate the expected number of dangerous lightning events and the resulting risk, introduces updated inputs and concepts (NSG, single risk, frequency of damage), and provides criteria for selecting both permanent and temporary protection measures to reduce risk to tolerable levels.

Q: Who typically uses it?

A: Lightning protection designers, electrical and safety engineers, facility managers, asset owners, consultants, utilities, and insurers use it when assessing lightning risk and specifying protection measures for buildings and installations.

Q: Is it current or superseded?

A: Current. This is the third edition published in 2024 and it cancels and replaces IEC 62305-2:2010; Corrigendum 1 (2024) has been incorporated into the edition.

Q: Is it part of a series?

A: Yes — it is one part of the IEC 62305 series (Protection against lightning), which also includes Parts 1 (general principles), 3 (physical damage to structures and life hazard) and 4 (electrical and electronic systems within structures).

Q: What are the key keywords?

A: Lightning protection, risk assessment, NSG, TWS, surge protection, equipotential bonding, LPS, lightning strike density, IEC 62305.