IEC 61557-11:2020

Overview

IEC 61557-11:2020 - part of the IEC 61557 series - specifies requirements for test equipment used to assess the effectiveness of residual current monitors (RCM) already installed in low-voltage distribution systems (up to 1 000 V AC and 1 500 V DC). The standard covers testing in all common earthing arrangements: TT, TN and IT systems, and includes directionally discriminating RCMs used in IT systems. It is a technical revision of the 2009 edition and focuses on the test equipment and test methods rather than product certification of RCMs.

Key topics and technical requirements

• Scope and intent: Requirements apply to test instruments that verify an RCM’s effectiveness in situ; they do not replace RCM product standards.
• RCM types covered: Type A and Type B RCMs are explicitly addressed; requirements for Type B were moved into the main text in this edition.
• Test functions:
  • Operating test - verifying the RCM trips/alarm at or above the rated residual operating current.
  • Non-operating test - ensuring the RCM does not trip below the specified non-operating current.
  • Actuating time test - measuring the time taken for the RCM to change to an alarm state when a residual current appears.
• Safety protections during testing:
  • Prevention of dangerous fault voltages (exceeding defined thresholds) in the monitored system during measurement.
  • Protection against overvoltages when the equipment is connected.
  • Electromagnetic compatibility (EMC) considerations for portable test gear.
• Marking and documentation: Requirements for clear marking and operating instructions, including warnings and test information.
• Test performance and uncertainty: Procedures and requirements for measuring operating uncertainty and validating protective performance.
• Terminology alignment: Terms aligned with IEC 60050 and the broader IEC 61557 series for consistency.

Practical applications and users

IEC 61557-11:2020 is essential for professionals who design, manufacture, specify, commission or maintain electrical safety test equipment and for those that perform on-site verification of protective monitoring systems:

• Test equipment manufacturers - to design instruments that comply with international test requirements for RCM effectiveness.
• Commissioning and maintenance engineers - to validate installed RCMs in TT, TN, IT systems.
• Electrical contractors, utilities and facility managers - to ensure residual current monitoring provides the intended protection.
• Testing laboratories and certification bodies - for developing methods to assess test instrument performance.

Related standards

• IEC 61557-1:2019 - General requirements for testing/monitoring equipment
• IEC 61557-6 - Effectiveness of residual current devices (RCD)
• IEC 62020 - Product standard for RCMs
• IEC 61010-1, IEC 61326-2-2, IEC/TR 60755 - safety, EMC and RCM background references

Keywords: IEC 61557-11:2020, residual current monitors, RCM testing, TT TN IT systems, low voltage distribution, electrical safety test equipment.