## 3 Design and Analysis
### Electrostatic Field Optimization of the FGIL
#### 3.2.1 Electrostatic Field Dispersion Apropos of Conventional and Stranded Conductors  
Concerning the analysis of the field dispersion along with identification of regions of high electric fields in the proposed GIL scheme, COMSOL Multiphysics(r)-based models for conventional and pliable GILs were developed and compared regarding the different conductor configurations given in Table 2. Figure 2a,b demonstrates the electric potential and electric field dispersion in a conventional GIL. Figure 3a,b exhibits the electric potential and electrostatic field dispersal in the proposed GIL with a circular strand conductor. Figure 4a,b represents the electric potential and electrostatic field distribution in the proposed GIL with trapezoidal strand conductor. Field dispersion regarding conventional and proposed schemes revealed that stranded conductors resulted in regions of concentrated electric field on the conductor's surface contour. Figure 5a,b represents the enlarged view of such concentrated electric field regions in the FGIL scheme regarding specimen 2 and specimen 3 of Table 2. Critical perusal of Figures 2-5 regarding electric field dispersion reveals that due to protrusions and surface irregularities of the stranded conductors, high electric fields appeared on their surface contour as compared to the conventional scheme with a smooth solid conductor. However, the trapezoidal strand conductor had approximately 10% lower magnitude of maximum electric field stresses due to its relatively smoother profile in comparison to the circular strand conductor. Figure 6 compares the average and maximum electric fields for conventional and proposed GIL schemes regarding the different conductor specimens described in Table 2. Further, Figure 7 compares the FUF for conventional and proposed GIL schemes regarding the different conductor specimens described in Table 2. Detailed analysis of Figures 6 and 7 revealed that the surface irregularity of stranded conductors in the proposed pliable GIL resulted in objectionably high electric fields regarding specimen 2 and specimen 3 in \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Specimen** & & & & & **Strand** & **Profile** & **Diameter** \\
**No.** & **Category** & **Material** & **Structure** & **Geometry** & **Profile** & **(mm)** \\ \hline
1. & Conventional & Aluminum & Hollow & & Smooth & 89 \\
2. & Proposed & Aluminum & Stranded & Circular & Irregular & 44.79 \\
3. & Proposed & Aluminum & Stranded & Trapezoidal & Irregular & 44.70 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Conductor specimens used in the comparative appraisal. comparison to the conventional scheme regarding specimen 1. Further, the field utilization factor was also reduced by 31% and 23% respectively for specimens 2 and 3 regarding proposed pliable GIL in comparison to specimen 1 regarding the conventional scheme. A probable solution to the above stated problem could be to enlarge the enclosure's diameter or to suppress the conductor's irregularity [63; 64; 65]. COMSOL Multiphysics(r)-based simulations were performed for this purpose, which revealed that enclosure enlargement resulted in the minimization of the irregular field distribution and reduced the electrostatic stresses on the conductor's surface. However, the FUF was reduced in comparison to the standard allowable limit for GILs because as per GIL standards, the enclosure's diameter should be approximately three times the conductor's diameter in order to acquire an FUF in the permissible range of 0.5 to 0.6 [17; 24; 41; 42]. The violation of the aforementioned constraint regarding enclosure diameter resulted in a poor field utilization factor for the proposed scheme, which is objectionable as per GIL standards. Thus, remedial measures regarding suppression of irregularities in the stranded conductor must be taken in order to achieve the required FUF and eradicate concentrated electric field regions.