This part of IEC 62271 specifies requirements for internal arc classification of metal enclosed pole-mounted switchgear installations used for alternating current with rated voltages above 1 kV and up to and including 52 kV with service frequencies up to and including 60 Hz. This standard is applicable to three-phase, two phase and single phase equipment. Enclosures may include fixed and removable components and may be filled with fluid (liquid or gas) to provide insulation. NOTE 1 For the use of this document high-voltage (IEC 60050-601:1985, 601-01-27) is the rated voltage above 1 000 V. However, medium voltage (IEC 60050-601:1985, 601-01-28) is commonly used for distribution systems with voltages above 1 kV and generally applied up to and including 52 kV; refer to [1] of Bibliography. This standard does not preclude that other equipment may be included in the same enclosure. In such a case, any possible influence of that equipment on the switchgear and controlgear is to be taken into account.