This document covers internal arc-fault control devices, hereinafter referred to as IACD, which are intended to: - detect internal arc-faults in low-voltage switchgear and controlgear assemblies, by processing (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 (see Annex D). For combined-type IACD, this document is considered in addition to the relevant product standard for internal arc-fault mitigation devices (IARD per IEC TS 63107:2020). Compliance to the relevant product standard is mandatory and cannot be claimed by testing to this document alone. 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 and controlgear (i.e. absence of internal arc-fault), including normal arcing associated with operation 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 most critical and challenging conditions for ar ...