These requirements apply to low smoke halogen-free, flexible, single-core power cables with crosslinked insulation and sheath. In particular for use at the direct current (DC) side of photovoltaic-systems, with a nominal DC voltage up to 1,5 kV between conductors and between conductor and earth. The cables are suitable to be used with Class II equipment. The cables are designed to operate at a normal maximum conductor temperature of 90 °C, but for a maximum of 20.000 hrs. a max. conductor temperature of 120 °C at a max. ambient temperature of 90 °C is permitted. NOTE The expected period of use under normal usage conditions as specified in this standard is at least 25 years.