Calculation and Analysis of Circulating Currents in the Metal Sheath of XLPE Cables under Cross-bonded Interconnection

Abstract

The large current of the grounding ring of the cable metal sheath not only increases electrical energy loss, but also affects the service life of the cable, and even causes major accidents such as cable line fires. Therefore, it is necessary to study the influencing factors of sheath circulation.The factors that generate metal sheath circulation mainly include the sheath circulation caused by the induced voltage generated by electromagnetic induction on the metal sheath due to the core current, and the leakage current injected into the metal sheath by electrostatic induction. This article establishes an equivalent model for calculating the circulating current of XLPE cable metal sheath based on cross interconnection, and writes a PyCharm program to verify the magnitude of the circulating current value of the three-phase sheath. A simulation model was built using PSCAD/EMTDC software, and the accuracy of the calculation method in this paper was verified by comparing theoretical values with simulation values. According to the debugging results, the larger the load current, the greater the loop current of the protective sheath. When the three equal lengths of cross shaped laying, three-phase load current balance, and cross interconnection are used, the minimum loop current of the protective sheath is achieved, while the grounding resistance of the circuit has almost no effect on the loop current.