Feasibility study on lengthening the high-voltage cable section and reducing the number of cable joints via alternative bonding methods

Among all failures in cable circuits, the failure rate of cable joints is much higher than that in cable bodies. In an effort to reduce cable failure rates and improve the reliability of power cable systems, this article studies the possibility of increasing the length of a cable section and thus reducing the number of cable joints via alternative sheath bonding methods. As the maximum length of an electrical cable section is governed by the permissible sheath standing voltage, this article first proposes a precise sheath voltage calculation model without approximations and simplifications. The sheath voltage per unit length has then been calculated for each bonding method using the proposed model. The maximum length of a cable section has then been calculated, based on the permissible sheath standing voltage, for the various sheath bonding methods. Results show that the traditional 500-m minor section length could be increased to 2.21 km by using the single-point bonding method. The maximum distance can be further lengthened by increasing the physical spacing among the three-phase cables. The economic comparison for each bonding method has also been made. Finally, the proposed method has been applied to a HV cable circuit already in operation, and the operational data confirms the feasibility.