This part of IEC 61643 describes the principles for selection, operation, location and coordination of SPDs to be connected to 50 Hz to 60 Hz a.c. and to d.c. power circuits and equipment rated up to 1 000 V r.m.s. or 1 500 V d.c. NOTE 1 Additional requirements may be necessary for special applications such as electrical traction, etc. NOTE 2 It should be remembered that IEC 60364 series and IEC 62305-4 are also applicable. NOTE 3 This standard deals only with SPDs and not with SPDs components integrated inside equipment.