Computation of Ampacity Derating of HV and MV Multiple Circuit Crossing

Cable crossings may occur in substations and other installations where cable congestion may be unavoidable. When a cable carrying a high level of current crosses another cable carrying high current, additional heat is generated at the crossing point. As a result the current carrying capacity or ampacity of both cables can be reduced. To determine the ampacity, Multiphysics software from Computer Simulation Technology (CST) is used to model 2D temperature profile for the cable system in cross over configuration. The industry specific software which is Power Cable Ampacity Calculation (CYMCAP) is used to validate the CST simulation. The CST model can then be used to recommend the possible ampacity improvement actions for the cases under study. The results of this paper graphically show how the temperature of the cables at the crossing increase and then decrease as the crossing point is approached, passed and moved away from. This temperature increase will, in turn, reduce the ampacity of both cables. The reduction in ampacity can then be estimated when the temperatures of the cables are known. These data will allow the planners and engineers to optimize the lay-out of the cables to achieve the optimum configuration for the required current load on the cable.