Escalating modernization has intensified the load requirement in metropolitan areas, which will mount further in future due to increasing trend of urbanization. Moreover, obligation of power system stability requires upgradation and new installation of power transmission systems (PTSs). Conventional PTSs include overhead lines (OHLs), underground cables (UGCs) and gas insulated lines (GILs). OHLs as well as UGCs face several impediments regarding their metropolitan applications like proximity concerns, aesthetics, right of way concerns, trench requirements, electromagnetic compatibility (EMC) concerns, land devaluation, health concerns, and repeated excavations due to faults. Conventional GILs also encounter several hindrances regarding their implementation in urban localities like larger bending radius, trench requirements, structural rigidity, right of way concerns, land devaluation, aesthetics and larger laying length at bends. Thus, complexities associated with conventional schemes necessitate the trenchless subsurface implementation of PTSs which requires structural pliability and significant load bearing capability. Considering the concerns mentioned above, in this thesis, a flexible gas insulated transmission line (FGIL), comprising of pliable enclosure, conductor and insulator is proposed for trenchless subsurface application of PTSs. Concerning the proposed scheme, a comprehensive design and analysis was performed in this research regarding electrostatic, dielectric and mechanical aspects. Practicability of performed design was analyzed analytically as well as through Autodesk Inventor and COMSOL Multiphysics based simulations. Further, an enclosed sphere gap discharge arrangement was developed in order to perform practical investigations regarding the synergistic dielectric characteristics of proposed conductor support with different gaseous dielectrics. Additionally, in order to identify the effectiveness of proposed electrode irregularity suppression scheme for FGIL, reinforced polyvinylchloride enclosure based 11 kV prototypes of FGIL were developed and analyzed through high voltage testing. Finally, as per the performed design, an 11 kV prototype of FGIL, comprising of polyethylene enclosure, was developed and tested through standard power frequency and lightning impulse withstand tests, in order to identify the dielectric withstand capability of proposed scheme. Results reveal that the proposed scheme could provide substantial structural flexibility along with the required electrical as well as mechanical integrity regarding trenchless subsurface applications of PTSs and could simplify the complexities associated with metropolitan applications of conventional PTSs.