IEC 60071-2:2018

Overview - IEC 60071-2:2018 (Insulation co‑ordination - Part 2: Application guidelines)

IEC 60071-2:2018 provides practical application guidance for insulation co‑ordination in three‑phase electrical systems with nominal voltages above 1 kV. It helps engineers and manufacturers select appropriate insulation levels and determine rated withstand voltages (for Ranges I and II of IEC 60071‑1), and to justify their association with standardized highest voltages for equipment. This edition is a horizontal standard (IEC Guide 108) and introduces important updates on surge arresters, very‑fast‑front overvoltages, altitude correction and evaluation of non‑standard lightning overvoltage shapes.

Key topics and technical requirements

• Representative voltage stresses - classification and sources of continuous, temporary, slow‑front, fast‑front and very‑fast‑front overvoltages used for co‑ordination studies.
• Selection of rated withstand voltages - procedures to determine co‑ordination, required and standard withstand voltages and related safety factors.
• Insulation co‑ordination procedures - step‑by‑step methods for ranges I & II (including conversion factors and test voltage selection).
• Surge arresters and protective devices - updated guidance on characteristics and application of MOSA, line surge arresters and spark gaps.
• Very‑fast‑front overvoltages - revised treatment of VFF overvoltages and new Annex J on insulation co‑ordination for UHV substations.
• Atmospheric/altitude correction - new Annex H providing altitude correction guidance affecting withstand voltages.
• Non‑standard lightning shapes - new Annex I with methods to evaluate atypical lightning overvoltage waveforms.
• Testing and standardization - overview of standard lightning and switching impulse tests, test conversion factors, and selection of type test procedures.
• Special cases - dedicated guidance for overhead lines, substations, transferred overvoltages in transformers and practical examples (informative annexes).

Practical applications and users

Who uses IEC 60071‑2:

• Power system designers and substation engineers selecting insulation coordination for transmission and distribution (U > 1 kV).
• Utility planners and protection engineers evaluating surge protection and overvoltage exposure.
• Equipment manufacturers and testing laboratories specifying and verifying rated withstand voltages and type tests.
• Consultants performing risk assessments for UHV substations, overhead lines and transformer transfer phenomena.

How it's used:

• Define insulation levels and safety factors for equipment and installations.
• Select and justify surge arresters and protection strategies.
• Convert representative overvoltages into test voltages and interpret test results for acceptance.

Related standards (if applicable)

• IEC 60071‑1 - Principles, ranges and general definitions for insulation co‑ordination (complements Part 2).
• IEC Guide 108 - Horizontal standard status and applicability guidance.