The feasibility of magnetic field reduction by phase relationship optimization in cable systems

This paper investigates the feasibility of magnetic fields reduction by optimization of phase relationships in a multi-circuit underground cable system, carrying unbalanced loads. A novel algorithm was developed for fast calculation of the multi-circuit cable system generated magnetic field. The unbalanced load was modeled by random selection of phase current values. A computer code was written to calculate the statistical distribution of the magnetic field above the cables on the ground level. The program calculates the maximum magnetic field for different phase relationships and selects the optimum phase relationship. Several multi-circuit cable systems used by utilities have been analyzed. The results show that the optimization of phase relationships effectively reduces the magnetic field for cable systems with both single and multi-point grounded sheaths in spite of the load unbalance.