This report applies to indoor enclosed switchgear and controlgear complying with IEC Publications 298 and 466, excluding gas-insulated metal-enclosed switchgear, intended to be used in service conditions more severe with respect to condensation and pollution than the normal service conditions specified in those standards.Note.- Whilst the performance of mechanical components, such as mechanisms, interlocks and enclosures, is also of importance, the tests detailed in this report have been designed primarily to investigate the behaviour of electrical insulation.