This part of IEC 62271 applies to high-voltage alternating current disconnecting circuit-breakers for operation at frequencies of 50 Hz and 60 Hz on systems having voltages above 52 kV. This standard identifies which requirements of IEC 62271-1, IEC 62271-100 and IEC 62271-102 standards are applicable. It also gives the additional requirements specific to these devices. This standard covers single switching devices which perform the functions of both a circuit-breaker and a disconnector by means of contacts housed in a single enclosure, and in which the circuit-breaker contacts in the open position satisfy, or contribute to, the isolating requirements of the disconnector function. As there is interaction between the requirements of the separate functions it is necessary to consider the standardisation of requirements. This standard details the requirements for a disconnecting circuit-breaker, identifying where these differ from the separate requirements of a discrete circuit-breaker and a disconnector. NOTE For design examples of disconnecting circuit-breakers, refer to Annex A.