Analysis of Induced Voltages on the Sheath of Double-Circuit Underground Power Lines - Part II: With Phases Transposition

This paper presents mathematical formulations for calculating induced voltages on the sheath of double-circuit underground transmission lines, focusing on four formations involving phases of transposition. The study analyzes the application of sectionalized and continuous cross-bonding techniques to assess and reduce induced voltages. Two crucial aspects are assessed: calculating induced voltages on the sheath of underground lines and computing current imbalance in an underground sub-transmission system. The findings demonstrate that utilizing phases transposition allows for effective control and reduced induced voltage on the sheath. However, in practical scenarios, a residual induced voltage persists due to minor section length variations, resulting in low losses on the sheath. Notably, the flat formation exhibits the highest residual induced voltage among all formations, reaching up to 12.69 V with continuous cross-bonding. Nevertheless, this still results in relatively low losses on the sheath. The study underscores the critical role of phases transposition in ensuring double-circuit underground transmission lines’ safe and efficient operation. Additionally, the study reveals that whether phases transposition is implemented or not has no direct influence on the imbalance of the sub-transmission system current. This emphasizes the significance of carefully considering the choice of formations and cross-bonding techniques to achieve optimal performance and reliability in the transmission network.