**Field Optimization and Electrostatic Stress Reduction of Proposed Conductor Scheme for Pliable Gas-Insulated Transmission Lines**

**Muhammad Junaid Alvi 1,2,\*, Tahir Izhar 1, Asif Ali Qaiser 3, Hafiz Shafqat Kharal 1 and Adnan Safdar 2**


Received: 13 June 2019; Accepted: 16 July 2019; Published: 25 July 2019

**Featured Application: Flexible gas-insulated transmission lines (FGILs) are a potential candidate for the trenchless underground implementation of high-voltage transmission lines in metropolitan areas. This research highlights the necessity of field intensity minimization and field irregularity suppression for FGILs regarding stranded conductors and proposes a practicable scheme for the same. The proposed scheme will facilitate the achievement of analogous electrostatic and dielectric characteristics for FGILs as compared to conventional gas-insulated lines (GILs).**

**Abstract:** The implementation of stranded conductors in flexible gas-insulated transmission lines (FGILs) requires field intensity minimization as well as field irregularity suppression in order to avoid dielectric breakdown. Moreover, the interdependence of enclosure and conductor sizes of FGILs regarding electrostatic aspects necessitate critical consideration of their dimensional specifications. In this research, geometric and electrostatic field optimization for FGILs regarding stranded conductors is performed. In addition, the effect of conductor irregularity on field dispersion is analyzed, and a semiconducting film (SCF)-coated stranded conductor is proposed as a potential candidate for FGILs. Considering the performed optimized design, an 11 kV scaled-down model of a 132-kV FGIL was also fabricated in order to practically analyze its electrostatic and dielectric performances regarding simple and SCF-coated stranded conductors. Simulation and experimental investigations revealed that the SCF-coated stranded conductor significantly minimized the field irregularity of the FGIL along with improving in its dielectric breakdown characteristics.

**Keywords:** dielectric strength; field grading; field utilization factor (FUF); gas-insulated transmission line; metropolitan; stranded conductor
