IEC TR 61641:2014 gives guidance on the method of testing of ASSEMBLIES under conditions of arcing in air due to an internal fault. The purpose of this test is to assess the ability of the ASSEMBLY to limit the risk of personal injury, damage of ASSEMBLIES and its suitability for further service as a result of an internal arcing fault. This third edition cancels and replaces the second edition published in 2008. It constitutes a technical revision. This third edition includes the following significant technical changes with respect to the previous edition: - arcing classes to define the different forms of protection provided against arcing faults; (i) personnel protection, (ii) damage restricted to part of the ASSEMBLY, and (iii) ASSEMBLY suitable for limited further service.; - two levels of personnel protection afforded by ASSEMBLIES under arcing fault conditions; (i) for ASSEMBLIES installed in areas where access to the ASSEMBLY is restricted to skilled persons, and (ii) for ASSEMBLIES installed in areas where the area is accessible to ordinary persons; - option of individually insulating all live conductors to make the complete ASSEMBLY an arc ignition protected zone (referred to as an 'arc free zone' in previous editions of the Technical report); - arc fault protection front, back and sides of an ASSEMBLY as the normal requirement; - minimum performance requirements for arc ignition protected zone.