The probabilistic rating of separate pipe cooled cables

To protect cable insulation, a temperature limit needs to be imposed on cables during operation. Since heat generated in the cable is mainly current dependent, this limit translates into a current limit which represents the current rating of the system. The authors report on a study carried out on a 400 kV separate pipe cooled underground cable system conventionally rated at 2038 A in winter and 1972 A in summer. Results of the probabilistic analysis giving the temperature profile of the system for December and July are presented. In addition, temperature limits for 20% and 30% overload conditions and the effects of varying water flow rates and inlet temperatures are discussed