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What is the meaning of fixed working temperature for cable applications ?
The fixed working temperature is defined in order to show that the cable does not crack under external shocks against the minimum temperature that occurs in the environment. This is expressed with the cold impact test.
IEC 60811-506:2012
Electric and optical fibre cables - Test methods for non-metallic materials - Part 506: Mechanical tests - Impact test at low temperature for insulations and sheaths
source : What is the meaning of fixed working temperature for cable applications ? (https://webstore.iec.ch/publication/3556)