IEC 60282-1-2020 High-voltage fuses – Part 1: Current-limiting fuses (IEC 60282-1:2020)

IEC 60282-1-2020 High-voltage fuses – Part 1: Current-limiting fuses (IEC 60282-1:2020). 4 Normal and special service conditions 4.1 Normal service conditions Fuses complying with this document are designed to be used under the following conditions. a) The maximum ambient air temperature is 40 °C and its mean measured over a period of 24 h does not exceed 35 °C. The minimum ambient air temperature is –25 °C. NOTE 1 The time-current characteristics of fuses will be modified between the minimum and maximum temperatures. b) The altitude does not exceed 1 000 m. c) The ambient air is not excessively (or abnormally) polluted by dust, smoke, corrosive or flammable gases, vapour or salt. d) For indoor installations, the conditions of humidity are under consideration but, in the meantime, the following figures can be used as a guide: – the average value of the relative humidity, measured during a period of 24 h, does not exceed 95 %; – the average value of the vapour pressure, for a period of 24 h, does not exceed 22 hPa; – the average value of the relative humidity, for a period of one month, does not exceed 90 %; – the average value of the water vapour pressure, for a period of one month, does not exceed 1 8 hPa. In these conditions, condensation may occasionally occur. NOTE 2 Condensation can be expected where sudden temperature changes occur in periods of high humidity. NOTE 3 To withstand the effects of high humidity and occasional condensation, such as breakdown of insulation or corrosion of metallic parts, indoor fuses designed for such conditions and tested accordingly or outdoor fuses are an alternative. NOTE 4 Condensation is prevented by special design of the building or housing, by suitable ventilation and heating of the station or by the use of dehumidifying equipment. e) Vibrations due to causes external to fuses or earth tremors are negligible. In addition, for outdoor installations, f) account should be taken of the presence of condensation or rain and rapid temperature changes; g) the wind pressure does not exceed 700 Pa (corresponding to 34 m/s wind speed); h) the solar radiation does not exceed 1 ,0 kW/m 2 . Applications involving fuse-links in enclosures (fuse enclosure packages) typically satisfy the requirements of “normal service conditions” because the ambient temperature (the temperature outside the enclosure) meets the temperatures in a) of this subclause. However, in an...