IEC 60071-2:2023

Overview

IEC 60071-2:2023 - Insulation co‑ordination, Part 2: Application guidelines provides practical guidance for selecting insulation levels and rated withstand voltages for equipment and installations in three‑phase AC systems (nominal voltages > 1 kV). It supports the application of the voltage ranges I and II defined in IEC 60071‑1 and justifies association of rated values with standardized highest voltages for equipment for insulation‑co‑ordination purposes only (it does not address human safety requirements). IEC 60071‑2:2023 is a horizontal standard per IEC Guide 108 and includes several substantive updates to reflect modern practices such as detailed simulation and new line/cable considerations.

Key topics and technical requirements

• Representative voltage stresses in service: origin and classification of overvoltages (continuous, temporary, slow‑front, fast‑front, very‑fast‑front).
• Overvoltage protection devices: characteristics and application of metal‑oxide surge arresters (MOSA) and line surge arresters (LSA).
• Determination of representative voltages: procedures and models (including a new Subclause on detailed simulation) to derive realistic stress levels for insulation co‑ordination.
• Co‑ordination withstand voltage: insulation strength characteristics, influence of polarity and weather, probability of disruptive discharge, and performance criteria.
• Required and standard withstand voltages: atmospheric/altitude corrections, safety factors (ageing, manufacturing dispersion), and conversion to standard test voltages (switching and lightning impulse).
• Special considerations: dedicated guidance for overhead lines, cable lines, GIL/GIB (gas‑insulated transmission line / gas‑insulated busduct) and substations. New informative annexes cover practical calculations (temporary overvoltages, lightning stroke and outage rates, use of line shunt reactors, Weibull distributions, simplified lightning methods, and examples).

Practical applications

• Defining insulation levels and withstand voltage requirements for high‑voltage equipment design and selection.
• Specifying surge protection strategy and arrester sizing for transmission and substation projects.
• Performing insulation co‑ordination studies using both simplified methods and detailed simulations to quantify overvoltage risks.
• Guiding testing and type‑testing procedures for manufacturers and test laboratories (selection of standard impulse levels and conversion factors).
• Informing design choices for overhead lines, cable systems and GIL/GIB installations to reduce lightning and switching‑related outages.

Who should use this standard

• Transmission and distribution utilities, substation and line designers, equipment manufacturers, insulation/co‑ordination engineers, consulting engineers, testing laboratories and regulators involved in high‑voltage system design, protection and specification.

Related standards

• IEC 60071‑1 (insulation co‑ordination - definitions and principles) - referenced for voltage ranges and foundational principles.
• IEC Guide 108 - horizontal standard classification.

Keywords: insulation co‑ordination, IEC 60071‑2:2023, withstand voltage, overvoltage, surge arrester, three‑phase AC systems, GIL GIB, temporary overvoltage, lightning overvoltage.