Sheath current characteristic and its reduction on underground power cable systems

Sheath current causes the sheath loss and can reduce the permissible current of the power cable transmission system. High sheath current is usually caused by the mixed burying formation of the cable, different length between sections, poor connection of the bonding leads, and connection of distribution cable on the transmission system. This paper analyses the characteristics of the sheath circulating current at various conditions and presents a useful method to reduce the sheath current in a mixed buying formation system. It can effectively reduce the current by up to 90%. The method is validated by the practical measurements and simulation using ATP, and also adopted in actual system. In addition, a special equipment is designed in this paper to measure and analyze the sheath circulating current. It can measure and analyze nine currents at a single time.