This technical report, which serves as an application guide for the determination of selectivity between over-current protective devices of low-voltage switchgear and controlgear, summarises the definitions of the terminology and provides examples of application. The following standards for devices are considered in this technical report: − IEC 60255-3; IEC 60255-6; IEC 60255-8, IEC 60255-12 − IEC 60269-1, IEC 60269-2, IEC 60269-3;IEC 60269-4; − IEC 60898-1; − IEC 60947 series; − IEC 61008-1; − IEC 61009-1. This report does not deal with other forms of protection, such as power-reversal protection,directional protection and arc-protection systems.