IEC TS 62257-7-3:2018(E) specifies the general requirements for the selection, sizing, erection and operation of generator sets in decentralized rural electrification systems. It applies to all low voltage combustion engine electricity generator sets energized by renewable energy such as biomass gasifier or biogas, or fossil fuel such as gasoline or diesel fuel, and designed for supplying electrical power to isolated sites used in systems as described in IEC TS 62257-2. The aim of this document is to provide users with the appropriate guide to select generator sets for using in micropower plant with different configurations and levels of reliability and safety of the equipment during its estimated service lifespan. This document describes the minimum requirement of generator set functionality and safety requirements and does not claim to be an exhaustive instruction manual or design specification. The main technical changes of this new edition with regard to the previous edition are as follows: - Increased the voltage and power levels to which this TS applies. - Added descriptions of four different types of micropower systems and their relevant requirements.