Economic Analysis of a Generalized Design for a Forced Cooled Cable

The thermal ratings of forced cooled and self-cooled cable runs are reviewed in order to assess the merit of forced cooling. These ratings, along with those of forced cooled joints, are employed to show that the ampacity of a 138 kV, 2000 kc mil high pressure oil filled pipe type system can be increased by at least 100o through forced cooling by circulating the pipe oil. The refrigeration requirements to permit this increased ampacity is determined, and the flow schemes which will meet these requirements are outlined along with the generic design of a refrigeration package to implement the preferred flow scheme. This generic design is used as the basis for an economic analysis which shows that single forced cooled cable ampacities greater than the ratings of a pair of self-cooled cables can be achieved at a 20% cost saving over the use of two self-cooled cables to meet the same load requirement. The emergency ratings of these forced cooled cables which correspond to the usual 100 and 300 hour emergency ratings are found to be 8 and 6% of the 100% duty cycle rating.