This Standard sets out minimum performance requirements for earth-leakage protection devices used on a.c. power supply systems having an earth-fault current limitation system (IT system). The devices are intended to—(a) continuously monitor the earth-leakage current; and (b) initiate tripping of the circuit interrupting device when the level of earth-leakage current and time exceed the predetermined values.NOTES:1 Whereas this Standard is based upon 50 Hz supply systems it is envisaged that equipment may be installed upon higher or low frequency supply systems.Consideration of the effects of these installations upon current limitation and effects upon the human body need to be considered. IEC 60479-1 and IEC 60479-2 should be referenced for the effects upon the human body of other supply frequencies.2 Installation guidelines are provided in Appendix A.