Replacement and Upgrade of a 66kV AIS to GIS at a Major Gas Refinery in India: A Phased Execution Strategy

Combined Cycle Power Plant (CCPP). land scarcity at the project location prevented AIS expansion, while the 4km transmission corridor required 60% capacity increase (from 25 MW to 40 MW per circuit) without replacing existing transmission towers. Additionally, the facility was vulnerable to riverbank flooding and cascading blackouts.

Objective: Replacement of AIS with a 66 kV GIS, upgradation of transmission lines, and deploy automated stability logic—the tasks to be achieved while maintaining "Zero Disruption" to active refinery production.

Approach: A multi-level GIS hall was designed and constructed on pile foundations, elevating equipments to first floor for flood resilience. Capacity was increased using HTLS GTACSR conductors through live-circuit reconductoring methodology. An IEC 61850 based FPBLS scheme implemented to scores of Refinery’s loads.

Key Results: The GIS commissioned with zero safety incidents and zero operational downtime while freeing up additional space in AIS yard. 66 kV Transmission Line capacity enhanced by reconductoring on existing towers. Real-time simulations validated the FPBLS scheme’s priority logic and spinning reserve management across seven substations.

Value: The project delivers a resilient, high-capacity power backbone for capacity expansion

It serves as a technical blueprint for brownfield modernization in industrial environments where space constraints and process continuity are critical factor.