IEC 60282-1 :2020 pdf download-High-voltage fuses – Part 1: Current-limiting fuses.
4.2 Special service conditions 4.2.1 General By agreement between the manufacturer and the user, high-voltage fuses may be used under conditions different from the normal service conditions given in 4.1 . For any special service condition, the manufacturer shall be consulted. 4.2.2 Altitude For installations at an altitude higher than 1 000 m, the required rated insulation withstand level of external insulation shall be determined by multiplying the needed insulation levels at the service location by an altitude correction factor, K a (> 1 ) given in column (2) of Table 1 . The dielectric withstand voltages of a fuse at a particular altitude may be determined by multiplying its rated insulation withstand levels by 1 /K a (< 1 ), given in column (3) of Table 1 . For altitudes between 1 000 m and 1 500 m and between 1 500 m and 3 000 m, the correction factors may be obtained by linear interpolation between the values in Table 1 .5.2.2 Rated current of a fuse-base The current assigned to a fuse-base that a new clean fuse-base will carry continuously without exceeding specified temperature rises under prescribed conditions. These conditions are that the fuse-base is equipped with a fuse-link designed to be used in the particular fuse- base, that the fuse-link has a rated current the same as the rated current of the fuse base, that the fuse-base is connected to the circuit with conductors of certain specified sizes and lengths, and that the ambient air temperature is not more than 40 °C. The rated current of a fuse-base should be selected from the following values: 1 0 A; 25 A; 63 A; 1 00 A; 200 A; 400 A; 630 A; 1 000 A. 5.2.3 Rated current of a fuse-link (I r ) The current assigned to a fuse-link that a new clean fuse-link will carry continuously without exceeding specified temperature rises when mounted on a fuse-base specified by the manufacturer and connected to the circuit with certain specified conductor sizes and lengths, at an ambient air temperature of not more than 40 °C (see IEC TR 62655:201 3). The rated current in amperes of the fuse-link should be selected from the R1 0 series.