Ampacity Calculations of Complex Underground Cables Arrangements

The limitations of the current methodologies are briefly presented, and the point-source method is proposed as an effective approach for modelling complex cable arrangements. Two methods for calculating the current rating of underground power cables using the point-source method are presented. The single-step method is straightforward to implement, but required more computation time whereas the optimization method involves more effort to implement but provides optimal results with significantly reduced computation effort.

A case study involving an installation of three circuits is used to compare both methods. When the current ratings of the three circuits are calculated, both methods yield the same results; however, the optimization method operated approximately two times faster. When the current in one of the circuits is fixed and the current ratings of the other two circuits are computed, the single-step method converges in 37 iterations, while the optimization method reaches an optimal solution in only 7 iterations.

The point-source method is then used to model three different installations. The first installation, a simple crossing, is used to demonstrate that the results obtained using the method described in IEC 60287-3-3[1] are consistent with those produced by the point-source approach. The other two modelled installations illustrate the utility of the point-source method.