IEC 60755-1 Ed. 1.0 en:2022

This document gives requirements, recommendations and information for the drafting of standards for residual current operated protective devices, intended to be used in DC systems, hereafter referred to as DC-RCDs.

NOTE 1 When referring to IEC 60755, "RCD" shall be understood as "DC-RCD".

This document is primarily intended to be used as a reference for drafting product safety standards for:
– DC-RCD intended for general use;
– DC-RCD specifically intended to be incorporated in a specific item of equipment;
– DC-RCD embedded in an equipment.

This document is applicable for standards covering devices:
– which detect a residual current,
– compare it to a reference value, and
– open the contacts when the residual current exceeds this reference value.

Any association of devices, each one of them performing separately one or two of the abovementioned functions but acting together in order to accomplish all three functions, is also covered by this document.

DC-RCDs are intended to provide fault protection, the exposed conductive parts of the installation being connected to a protective conductor, in accordance with IEC 60364-4-41:2005 and IEC 60364-4-41:2005/AMD1/2017.

DC-RCDs having a rated residual operating direct current not exceeding 80 mA and having a rated voltage not exceeding 220 V DC for single-pole or 440 V DC for two-pole are also used as a provision for additional protection, according to IEC 60364-4-41.

NOTE 2 Further requirements for higher voltages are under consideration.

NOTE 3 The value of 80 mA was the result of a calculation based on the content of clause 6 of IEC 60479-1:2018 and 5.3.4 of IEC 60479-2:2019.

NOTE 4 In Austria the value of 80 mA is considered as provisional until a broader and more solid set of data than the actual basis of the IEC 60479 series is available for DC.

In accordance with IEC 60364-4-42, residual current devices with a rated residual operating current not exceeding 300 mA can also be used to provide protection against fire hazards due to insulation faults.

DC-RCDs are suitable for isolation. They are suitable for use in TN, TT, and, under specific conditions, IT systems.

DC-RCDs are resistant to unwanted tripping including the case where surge voltages (as a result of switching transients or induced by lightning) cause loading currents in the installation without occurrence of flashover.

This group safety publication is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 104 and lSO/lEC Guide 51. It is not intended for use by manufacturers or certification bodies.

One of the responsibilities of a technical committee is, wherever applicable, to make use of group safety publications in the preparation of its publications. The requirements, test methods or test conditions of this group safety publication will not apply unless specifically referred to or included in the relevant publications.