This part of IEC 61439 defines the specific requirements for the power switchgear and controlgear assembly (abbreviated ‘PSC-assembly’ throughout this document see 3.1.101) as follows: assemblies for which the rated voltage does not exceed 1 000 V AC or 1 500 V DC; assemblies designed for a nominal frequency of the incoming supply or supplies not exceeding 1 000 Hz; Frequencies above 1 kHz are considered as high frequencies, see also IEC 60664-1:2007, 5.3.3.2.5 to take into account additional constraints to insulation coordination.