Sparsity Enhancement in Mutuality Coupled Networks

Mutual coupling in three-phase or zero-sequence networks often results in severe sparsity degredation in network analyses based on the nodal admittance matrix. Retention of mid-line nodes in the zero-sequence nodal admittance matrix results in sparsity enhancement and computational improvements. These improvements come about from the breaking up of large mutually coupled groups. Examples based on both small and large test cases are used to illustrate the principles involved. These results indicate that even though, for a system of realistic size, retaining mid-line nodes approximately doubles the size of the nodal admittance matrix, the net computational requirements can sometimes be reduced to a third or less of those of the original system.