The purpose of this part of IEC 62257 is to specify 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 with a rated power up to 100 kVA, and designed for supplying electrical power to isolated sites used in systems as described in IEC/TS 62257-2. This technical specification is not an exhaustive resource for the design, installation, operation or maintenance of generator sets but is more focused on recommendations to provide strategies on selection and criteria which may affect the use of such generation systems in a rural electrification project. Two cases will be considered as illustrated by Figure 1 to power a collective electrification system (microgrid) or an individual electrification system. • the micropowersystem is composed of one generator set • the micropowersystem is a hybrid one and the generator set is only part of it. This case is addressed in the document dedicated to micropower system (IEC/TS 62257-9-1). The aim of this technical specification is to provide users with the appropriate levels of reliability and safety of the equipment during its estimated service lifespan. It describes the minimum safety requirements and does not claim to be an exhaustive instruction manual or design specification. Compliance with this technical specification does not exempt any person, organization or corporation from the responsibility to comply with all other relevant regulations. This technical specification gives recommendations for the following types of generator sets: a) single phase; b) three phase; c) LV range up to 500 V - 50/60 Hz (see IEC/TS 62257-9-2).