IEC 61557-9:2023

Overview

IEC 61557-9:2023 - part of the IEC 61557 series on electrical safety in low-voltage distribution systems - specifies requirements for Insulation Fault Location Systems (IFLS) used to localize insulation faults in unearthed IT systems. The standard covers IFLS for unearthed IT AC systems (and AC systems with galvanically connected DC circuits) up to 1 000 V AC, and unearthed IT DC systems up to 1 500 V DC, and is independent of the measuring principle used. Edition 4.0 (2023) supersedes the 2014 edition and contains technical revisions to definitions, performance and test requirements, and document structure.

Key topics and technical requirements

• Mandatory and optional functions: Specifies required functions such as location warning, local and remote location warnings (LLW / RLW), and optional features like insulation value indication and self-test.
• Performance requirements: Defines response sensitivity and permissible locating current and locating voltage limits; performance test criteria were newly added in this edition.
• Safety and insulation coordination: Requirements for clearance/creepage distances, protection class, earth connection and permanently admissible voltages.
• Environmental and mechanical requirements: Climatic, mechanical robustness and IP protection class requirements to ensure reliable operation in intended environments.
• Electromagnetic compatibility (EMC): EMC limits and testing applicable to IFLS products, with specific provisions for medical locations (MED‑IFLS).
• Testing and verification: Detailed type and routine tests covering locating current/voltage, response sensitivity, location warning function, loss of sensors, marking and instructions, and record keeping. The structure is aligned with IEC 61557-1:2019.
• Annexes: Normative annexes for medical locations (MED-IFLS) and for portable IFLS, plus an informative annex explaining leakage capacitances and example IFLS layouts.

Practical applications

• Locating insulation faults in unearthed IT systems to support electrical safety and continuity of service in:
  • Industrial plants and process installations
  • Power distribution within buildings and complexes
  • Renewable energy and DC microgrids using unearthed architectures
  • Medical locations (special MED‑IFLS requirements)
• Enhances maintenance, reduces downtime and helps comply with electrical safety regimes by providing clear requirements for equipment performance, testing and documentation.

Who should use this standard

• Manufacturers and designers of IFLS equipment
• Test laboratories and certification bodies performing type and routine tests
• Electrical safety engineers, installers and maintenance teams working with unearthed IT AC/DC systems
• Facility managers and medical-planning engineers specifying equipment for critical installations

Related standards

• IEC 61557 series (general requirements for equipment for testing, measuring or monitoring protective measures)
• IEC 61557-1:2019 (general requirements and structure alignment)

Keywords: IEC 61557-9, insulation fault location, IFLS, IT systems, unearthed IT, locating current, locating voltage, electrical safety, low voltage distribution.