Power loss estimation in a 420kv Gas Insulated Busbar (GIB) by theoretical and simulation techniques — A comparison

Gas Insulated Substations (GIS) have found wide use in the past few decades. They offer several advantages over traditional Air Insulated Substations (AIS) which include superior dielectric strength, limited space requirements. Gas Insulated Busbar (GIB) is a critical part in a GIS since it serves as a component for tapping power for subsequent distribution to various interconnected components. Its failure would be detrimental and costly. Hence, manufacturers are faced with the task of minimizing the power loss in GIB. Standards stipulate stringent norms on the upper temperature rise limit for conductors and enclosures. Joule loss in a GIB is the primary source of heat for temperature rise and depends on the rated current, geometric dimension and resistivity. Further, skin-proximity effect results in a non-uniform current distribution leading to greater losses. This paper develops a 2-D finite element model of a GIB and employs magnetic analysis to estimate the power loss in the conductor and enclosure for rated current at maximum operating temperature. For the GIB taken up for study and analysis, losses are calculated using a theoretical method as per procedures laid out in CIGRE Working Group 21.12. The simulation and theoretical values are compared and cross-validated.