What is IEC 62020-1:2020?

IEC 62020-1:2020 is the product standard for residual current monitors (RCMs) for household and similar uses. It covers rated operational and monitored-circuit voltages up to 440 V AC and rated currents up to 125 A. The 125 A rating refers to the load circuit, not the residual current alarm threshold.

The 2020 edition replaces IEC 62020:1998 and its 2003 amendment. Changes include Type F and Type B definitions, marking and associated tests. The IEC copy incorporates the July 2020 corrigendum. Unlike the IEC 61557 series, this document addresses the RCM itself.

RCM, RCD and IMD: different functions

An RCM monitors residual current and signals when its threshold is exceeded. An RCD disconnects the circuit for protection: IEC 61008 concerns RCCBs without integral overcurrent protection, while IEC 61009 concerns RCBOs with that protection. An IMD monitors insulation resistance, particularly in IT systems; its product standard is IEC 61557-8. Residual current in mA and insulation resistance in kΩ are different measurements.

Measurement principle and sensor installation

All live conductors of the monitored circuit, including the neutral where present, pass through the same summation current sensor. The PE protective conductor stays outside that sensor. Current returning through another path creates an imbalance. A leakage current clamp uses the same summation principle when measuring residual current. Clamping only one phase normally measures load current.

Check the earthing arrangement, shared neutrals and unwanted N–PE connections. Select the sensor opening, conductor arrangement and sensor–monitor combination according to the manufacturer’s instructions. PE continuity cannot be established from an RCM reading; protective conductor and bonding resistance testing is a separate check.

Selecting a type for circuits with electronic drives

Type A detects AC and pulsating DC residual currents within its specified scope. Type B also detects smooth DC components. Type F addresses specified mixed-frequency waveforms. Selection requires checking waveform, frequency response and sensor compatibility, alongside current ratings. Circuits with EMC filters may have operational leakage; a higher reading does not necessarily indicate an insulation fault.

Commissioning and interpreting an alarm

Set the alarm threshold and response delay with regard to normal installation behaviour and the protective arrangement. There is no universal “30 mA setting” for every RCM. Use a compatible test method to verify the path from the sensor to the final alarm indication. IEC 61557-11 covers test equipment for checking installed RCM effectiveness; it does not replace the RCM product standard.

If alarms are monitored through a PLC, also check how sensor faults or loss of supply are reported. Initial and periodic installation verification, RCD effectiveness testing and loop impedance measurement retain their respective roles. Continuous residual current monitoring does not remove all these checks.

Illustrative example: Under comparable load conditions, a rise from 8 mA to 18 mA and then 27 mA is a trend to investigate. These are example readings, not standard alarm limits. Investigate possibilities such as moisture, added loads or cable damage. Appropriate insulation resistance testing may help confirm the findings.

Sources: IEC 62020-1:2020, IEC 61557-11:2020 and Bender RCM operating principle.