Frequency-dependent transmission line modeling utilizing transposed conditions

Existing phase domain transmission line models are capable of producing highly accurate results for both overhead lines and underground cables. This paper introduces a hybrid line model which gives substantial savings in computation time without loss of accuracy, when one or more circuits of a transmission system are treated as continuously transposed. This is achieved by means of a constant transformation matrix in combination with a reduced-size phase domain line model and a number of single-phase (modal) line models. The calculated examples demonstrate a potential speed increase over a full phase domain model between three and four. If none of the circuits are transposed, the line model degenerates into a full phase domain line model.