A study of zero-sequence current induced in a cable system

Large zero-sequence currents found in an actual crossbonded cable system led to a study of their causes and a solution to the problem. Measured values were compared to calculated results by the BPA-EMTP circuit analysis program. It was found that the zero-sequence currents were circulating between different circuits in the cable system and that they were being generated by the induction between phases in the same cable route. It was determined that the zero-sequence currents could be greatly reduced in a twin circuit (six phases) by symmetrical configuration of the cables. However, in a four-circuit system, no significant reduction could be achieved even by the symmetrical configuration