Design of Inter-state Transmission System for the World’s Largest Renewable Energy Park (~45GW) at Khavda, Gujarat in India - Planning Perspective & Transient Stability Analysis

This paper presents the planning philosophy, system architecture, and dynamic performance assessment of the ISTS designed for full-scale evacuation of power from the Khavda complex.

The studies are carried out for the 2030–31 timeframe using a detailed All-India network model and multiple seasonal and diurnal load generation scenarios to ensure compliance with steadystate, dynamic, and regulatory criteria.

The primary challenges addressed include the concentration of 42 GW of RE generation in a geographically constrained region, the requirement for long-distance bulk power transfer to distant load centers, weak grid conditions due to the absence of synchronous generation, low inertia and limited fault current contribution from IBRs, and corridor constraints. The planning framework also emphasizes future scalability and readiness for potential cross-border interconnections.

To address these issues, a hybrid High Voltage Alternating Current (HVAC) – High Voltage

Direct Current (HVDC) transmission architecture has been adopted. A strong 765 kV and 400 kV HVAC backbone provides meshed network support, while ±800 kV Line Commuted

Converter (LCC) HVDC corridors enable long-distance bulk power transfer. ±500 kV Voltage

Source Converter (VSC) HVDC links enhance controllability, provides black start capability and other grid support functions. The system has been planned in phases, aligned with progressive RE capacity addition, ensuring timely evacuation and operational flexibility.

Special emphasis has been placed on grid strengthening and voltage control. The system is designed to maintain a minimum Short Circuit Ratio (SCR) of 5 at all pooling stations through optimized network meshing, corridor planning, and bus sectionalization. Synchronous condensers have been deployed to provide inertia, fault current contribution, and dynamic voltage support. A layered reactive power compensation strategy comprising shunt reactors,

Static Synchronous Compensators (STATCOMs), Mechanically Switched Capacitor (MSCs)/

Mechanically switched Reactor (MSRs), and plant-level reactive capability ensures stable voltage profiles under varying operating conditions.

Dynamic performance was evaluated using detailed simulations in Phasor Domain Transient software platform with second-generation Western Electricity Coordinating Council (WECC)

- based generic models using the Gujarat Grid model on 2030-31 time frame. The system demonstrates compliance with Low Voltage Ride Through (LVRT) and High Voltage Ride

Through (HVRT) requirements, withstanding voltage dips down to 0.15 pu for 300 ms. During disturbances, plants inject priority reactive current and recover more than 90% of pre-fault active power within one second of fault clearance. Stable voltage recovery without sustained oscillations confirms the robustness of the proposed design. During voltage swell (HVRT) case,

RE generators are able to ride through overvoltage conditions, and sufficient reactive power absorption helps to maintain voltage stability. Dynamic reactive power equipment

(STATCOMs) further contributes towards the stable operation of network during the severe voltage dips.

Overall, the Khavda Inter-State Transmission System (ISTS) enables secure evacuation of 42

GW of renewable power, demonstrates the feasibility of RE-dominated grid operation, and establishes a scalable planning framework. The approach provides a benchmark for future mega renewable zones and supports India’s long-term vision for global power interconnections.