IEC 61557-15:2014 specifies requirements related to functional safety and is based on the IEC 61508 standard series for the realization of Insulation Monitoring Devices (IMD) as specified in IEC 61557-8 and for Insulation Fault Location Systems (IFLS) according to IEC 61557-9, according to phase 10 of the IEC 61508-1 lifecycle. These devices provide safety related functions for IT systems. This part of IEC 61557 is - concerned only with functional safety requirements intended to reduce the functional risk during the use of IMDs and IFLSs; - restricted to risks arising directly from the device itself or from several IMDs or IFLSs working together in a system; and - intended to define the basic safety functions provided by the devices. This part of IEC 61557 does not - deal with electrical safety according to IEC 61010-1 and the requirements of IEC 61557-8 and IEC 61557-9; - cover the hazard and risk analysis of a particular use of the IMD or IFLS; - identify all the safety functions for the application in which the IMD or IFLS is used; and - cover the IMD or IFLS manufacturing process. Functional safety requirements depend on the application and should be considered as part of the overall risk assessment of the specific application. The supplier of IMDs and IFLSs is not responsible for the application. The application designer is responsible for the risk assessment and for specifying the overall functional safety requirements of the complete IT system and he should select the functional safety level (SIL) of the IMD and/or IFLS when their safety function is part of the functional safety assessment in the IT system. This publication is to be read in conjunction with IEC 61557-8:2007 and IEC 61557-9:2009