applies to free standing operation a.c. static transfer systems (STS) intended to ensure the continuity of load supply through controlled transfer, with or without interruption of power, from two or more independent a.c. sources.includes requirements for the switching elements, their control and protective elements, where applicable. The IEC 62310 series also includes information for the overall integration of the STS and its accessories into the a.c. power network. it applies to systems up to 1 000 V a.c. which are intended to be used in single-phase, phase-phase or three-phase applications