The Maximum Safe Operating Temperature of Low-Voltage Paper-Insulated Cables

The Standards of the Institute state that for low-voltage cables the maximum safe operating temperature is 85 deg. cent. Experiments show that continuous operation of 100 deg. cent. for less than a month, seriously impairs the mechanical condition of impregnated paper. A standard of permissible mechanical condition should, therefore, be established, if such high temperatures are to be allowed. Operation at higher temperatures than allowed by the present Standards is, however, in the nature of a gamble and it is questionable whether the Standards should take cognizance of it.