IEC TR 61912-2-2009 PDF

Full title and description

IEC TR 61912-2:2009 — Low-voltage switchgear and controlgear — Over-current protective devices — Part 2: Selectivity under over-current conditions. This Technical Report is an application guide that summarises terminology and provides worked examples for determining selectivity (coordination) between over-current protective devices used in low-voltage switchgear and controlgear assemblies.

Abstract

Provides guidance on how to assess and apply selectivity (discrimination) between fuses, circuit-breakers and other over-current protective devices in low-voltage installations. The report explains relevant definitions, presents examples and discusses interactions with device-specific standards to assist designers and specifiers in achieving selective protection under over-current conditions.

General information

• Status: Published (Technical Report).
• Publication date: 13 May 2009.
• Publisher: International Electrotechnical Commission (IEC).
• ICS / categories: 29.130.20 (Low voltage switchgear and controlgear).
• Edition / version: Edition 1.0 (2009).
• Number of pages: 33.

Scope

IEC TR 61912-2:2009 serves as an application guide for determining selectivity between over-current protective devices used in low-voltage switchgear and controlgear. It summarises terminology, describes methods of assessment and gives application examples; it also refers to the device standards (fuse and circuit-breaker series) relevant when performing coordination studies.

Key topics and requirements

• Definitions and terminology relevant to selectivity and coordination of over-current protective devices (clear definitions to ensure consistent application).
• Guidance on methods for assessing selectivity between devices (time/current discrimination, energy-based approaches and practical example calculations).
• Examples of selectivity coordination for combinations of fuses, thermal-magnetic and electronic circuit-breakers, and residual-current devices.
• Reference to device standards that must be considered when applying selectivity (for example IEC 60255 series, IEC 60269 series, IEC 60898-1, IEC 60947 series, IEC 61008/61009).
• Practical considerations and limitations (application boundaries and illustrative case studies rather than mandatory test procedures).

Typical use and users

Used by electrical designers, switchgear and protection engineers, specifiers, consulting engineers, manufacturers of protective devices, testing laboratories and utilities to plan and verify selective coordination of protection systems in low-voltage installations. The document is particularly useful when preparing protection studies, writing specifications, or training staff on coordination principles.

Related standards

Closely related to IEC TR 61912-1 (Part 1: application of short-circuit ratings) and other IEC application guides such as IEC TR 61459 and IEC TR 61818; it also references device standards including the IEC 60255 protection relays series, IEC 60269 fuses series, IEC 60898-1 (circuit-breakers for household), the IEC 60947 series (industrial switchgear) and IEC 61008/61009 (residual current devices). These documents are commonly used together when designing and verifying coordination.

Keywords

selectivity, coordination, over-current protective devices, low-voltage switchgear, fuses, circuit-breakers, discrimination, protection study, application guide, IEC TR 61912.

FAQ

Q: What is this standard?

A: IEC TR 61912-2:2009 is a Technical Report published by the IEC that provides application guidance on selectivity (coordination) between over-current protective devices used in low-voltage switchgear and controlgear.

Q: What does it cover?

A: It covers definitions, practical guidance and worked examples for determining selectivity between protective devices (fuses, circuit-breakers and related devices), and points to relevant device standards to be considered during coordination. The report is informative and intended as guidance rather than prescriptive test requirements.

Q: Who typically uses it?

A: Electrical and protection engineers, switchgear manufacturers, test laboratories, utilities and specifiers who need to design, verify or specify selective protection in low-voltage installations.

Q: Is it current or superseded?

A: As published on 13 May 2009 the Technical Report remains the 2009 edition (Edition 1.0). The IEC webstore lists the document as published with a stability indication extending to 2026 and does not indicate a later superseding edition at the time of record. Users should check the IEC catalogue or national standards bodies for any amendments or newer editions if up-to-date confirmation is required.

Q: Is it part of a series?

A: Yes — it is Part 2 of IEC 61912 (TR 61912-1 is Part 1 covering short-circuit rating application); the TR is part of a set of application guides dealing with coordination and related topics in low-voltage switchgear and controlgear.

Q: What are the key keywords?

A: Selectivity, coordination, over-current protection, fuses, circuit-breakers, low-voltage switchgear, discrimination, protection study, IEC TR 61912.