This part of IEC 62271 specifies requirements for internal arc classification of metal-enclosed pole-mounted AC switchgear installations with rated voltages above 1 kV and up to and including 52 kV with service frequencies up to and including 60 Hz. This document is applicable to three-phase, two-phase and single-phase open terminal equipment. Enclosures may include fixed and removable components and may be filled with fluid (liquid or gas) to provide insulation. NOTE 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 the Bibliography. This document 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.