EN IEC 60947-9-2:2025

This document covers internal arc-fault control devices, hereinafter referred to as IACD, whichare intended to:- detect internal arc-faults in low-voltage switchgear and controlgear assemblies, byprocessing (at a minimum) the optical effect of an internal arc-fault, and- operate mitigation device (either external or combined)in order to minimize the effects of the internal arc-fault (see Figure 1).For the purpose of this document the terms "light" or "optical" covers more than visible spectra.They may cover also, for example, infrared or ultraviolet electromagnetic radiations (seeAnnex D).For combined-type IACD, this document is considered in addition to the relevant productstandard for internal arc-fault mitigation devices (IARD per IEC TS 63107:2020). Complianceto the relevant product standard is mandatory and cannot be claimed by testing to this documentalone.NOTE 1 Low-voltage switchgear and controlgear assemblies are usually described by IEC 61439 series.[Figure 1]Therefore, this document covers the following:- internal arc-fault control device (stand-alone, multifunction or combined);- one or more associated sensor(s) used to detect optical effect of the internal arc-fault;- sensor(s), sensing another physical effect, to confirm the fault;- associated or combined mitigation device.An IACD is not intended to trigger under normal operation of low-voltage switchgear andcontrolgear (i.e. absence of internal arc-fault), including normal arcing associated withoperation of disconnecting and switching devices.This document only covers the following methods:- optical detection of the light caused by an internal arc-fault;- optional confirmation of internal arc-fault by line current measurement.Many different conductive materials could be used in LV assemblies (e.g. steel, copper,aluminium). Nevertheless, tests specified in this document are deemed to represent the mostcritical and challenging conditions for arc-detection and cover all combinations of conductivematerials.NOTE 2 Compared to other materials (e.g. steel, aluminium), copper leads to a lower optical radiation energy.The rated voltage of the assembly in which an IACD is installed does not exceed 1 000 V AC.Such devices are designed to be operated and maintained by skilled persons only.This document does not cover:- DC internal arc-fault detection and control;- overcurrent relays;- AFDD (arc-fault detection devices) as defined by IEC 62606;- guidance on installation within assemblies;NOTE 3 The integration of an IACD into an assembly is described in IEC TS 63107.- use with additional measures needed for installation and operation within explosiveatmospheres. These are given in IEC 60079 series documents;- requirements for embedded software and firmware design rules; for this subject, themanufacturer is responsible for taking additional safety measures;NOTE 4 IEC TR 63201 describes rules for firmware and embedded software development preventing errors insoftware.- cybersecurity aspects; for this subject, the manufacturer is responsible for taking additionalsafety measures;NOTE 5 See IEC TS 63208.- mobile applications.NOTE 6 Even when addressing internal arc-fault mitigation devices, this document does not supersede any otherrelevant product standard (e.g. IEC 60947-2 or IEC 60947-9-1).NOTE 7 DC arcing fault phenomena are under consideration. Further investigation is needed to comprehend DCarcing phenomena and required sensing.