The Indian electricity transmission sector has been evolving to meet the increasing power demand and keep up with the changing energy mix, particularly the increasing penetration of renewable energy. As of March 2022, the installed renewable energy capacity stood at 157 GW, accounting for approximately 39 per cent of the total installed capacity. By January 2024, the installed capacity from renewable energy sources, including large hydro, increased to 188 GW. The capacity is further estimated to rise to 537 GW by 2030. The exponential growth in capacity will necessitate the development of transmission and distribution infrastructure such as reactors, transformers and substations.
Plans for renewable energy integration
As per the Central Electricity Authority’s report on “Transmission System for Integration of over 500 GW RE Capacity by 2030”, 50,890 ckt km of ISTS transmission line length and 433,575 MVA of substation capacity are required for integrating additional wind and solar capacities by 2030. This would entail an estimated investment of Rs 2,442 billion.
In terms of voltage-wise line length additions, the required additional transmission systems include 8,120 ckt km of high voltage direct current transmission corridors (+800 kV and +350 kV), 25,960 ckt km of 765 kV AC lines, 15,758 ckt km of 400 kV lines and 1,052 ckt km of 220 kV lines. The report also plans for connecting 10 GW of offshore wind capacity (5 GW each for Gujarat and Tamil Nadu) through submarine cables.
Another key initiative is the green energy corridor I (GEC-I) initiative, under which approximately 24 GW of renewable energy capacity was slated for integration into the intra-state network. The scheme is currently under implementation by state transmission utilities (STUs) of eight renewable-rich states – Andhra Pradesh, Gujarat, Himachal Pradesh, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan and Tamil Nadu. As of March 31, 2023, 9,060 ckt km of transmission lines have been constructed and 21,303 MVA of substations have been charged. Out of the eight states, four have completed all the projects – Rajasthan, Madhya Pradesh, Karnataka and Tamil Nadu. The remaining four states have requested for further extension up to June 30, 2024. The projects have been delayed mainly due to delays in land acquisition, right-of-way issues and forest clearances. Under the GEC-II scheme, about 19.4 GW of renewable energy capacity is planned to be connected into the intra-state system. The GEC-II scheme has been sanctioned with an estimated project cost of Rs 120.31 billion, including central financial assistance (CFA) of Rs 39.7 billion, while the remaining 67 per cent of the project cost is financed through loans.
There has also been a concerted effort towards constructing both intra-state and interstate transmission systems, which is crucial for the efficient evacuation of renewable power. To enhance grid management capabilities, regional energy management centres have been established. These centres focus on improving the renewable power forecasting and assisting grid operators in effectively managing the variability and intermittency associated with renewable energy sources.
The government has also introduced innovative solutions such as solar-wind hybrid projects, renewable energy projects integrated with energy storage systems, and the supply of renewable energy balanced with non-renewable energy sources to mitigate intermittency issues. In addition, flexibility has been granted in the generation and scheduling of thermal/hydro power stations through bundling with renewable energy and storage power. To further strengthen the renewable energy market, initiatives like green term-ahead market and green day-ahead market have been implemented to facilitate the sale of renewable energy. Furthermore, in a bid to incentivise renewable energy adoption, the government has waived interstate transmission charges on the transmission of electricity generated from solar and wind sources. These efforts underscore the government’s commitment to advancing renewable energy integration within the national grid, which is crucial for achieving sustainable energy goals.
Challenges in renewable energy integration
Despite its wind and solar energy potential to address rising energy demands, India faces obstacles in renewable energy infrastructure development. The ageing power grid exacerbates the problem, with many transmission and distribution lines built years ago now incapable of meeting current demands and adapting to extreme weather patterns. Predicting electricity generation is particularly challenging due to the reliance of most renewable energy technologies on weather and environmental conditions. Securing finance has posed a significant hurdle to the advancement of clean energy resources. The substantial initial investment required and the perceived risks associated with renewable energy projects have deterred investors, leading to a reluctance to engage and making projects financially unfeasible.
Further, traditional transformers encounter challenges in managing and transmitting large quantities of electricity, particularly due to the volatile nature of variable renewable energy installations. These systems generate electricity intermittently, leading to significant and rapid fluctuations in electricity generation. Furthermore, the increasing adoption of rooftop solar in the coming years will result in more prosumers interested in selling electricity to the grid during peak hours and drawing electricity during off-peak periods.
The energy storage strategy is becoming increasingly vital for mitigating fluctuations and ensuring consistent power supply, particularly in large-scale renewable energy projects. These systems not only store surplus energy for varying durations but also enhance the reliability of power supply. Battery technology has seen significant advancements, with nickel-chromium, redox-flow, sodium-sulphur and vanadium flow batteries gaining traction alongside lead-acid and lithium-ion variants. Their rapid response rates, quick installation and ability to support several start-stop cycles make them instrumental in addressing grid-related issues in India.
Transitioning to smart transformers will enable the bi directional flow of energy, allowing electricity to flow from the grid to buildings and vice versa. Smart transformers enhance the resilience of energy grids, making them more adept at handling volatility and grid instability. Dynamic compensation methods, like voltage-sourced converter-based HVDC and static synchronous compensators (STATCOM), are also being employed to maintain grid parameters and stability. Utilising internet of things technology will enable real-time monitoring of grid performance, followed by immediate identification and resolution of potential issues by power companies.
Outlook
The regulatory framework in India is aimed at improving renewable energy connectivity, with the GNA Regulations 2022 ensuring equitable access to the central transmission network for all power producers. Ancillary services markets are being established, and efforts to create awareness and build capacity are under way, supporting the effective integration of renewable energy into the grid. The integration of advanced technologies into the grid will enhance its resilience and efficiency, crucial for managing the intermittency of large-scale renewable energy and adapting to evolving load profiles driven by initiatives such as the government’s e-mobility programme.
The transmission system is being strategically developed to accommodate approximately 537 GW of renewable energy capacity by 2030, aligning with the government’s energy transition objectives.
As per the recently released draft National Electricity Plan (NEP) 2023, a transmission line length of 123,577 ckt km and transformation capacity addition of 710,940 MVA are required during 2022-27. Around 170 transmission schemes, with a collective cost exceeding Rs 3.13 trillion for interstate transmission and approximately Rs 1.61 trillion for intra-state systems, are being implemented. In addition, a designated investment of Rs 151.2 billion is aimed at connecting the Andaman & Nicobar Islands with the mainland. At present, these islands heavily depend on diesel generators, with minor contributions from renewable sources. A groundbreaking initiative proposes to connect the islands via an undersea cable spanning 1,150 km, with the objective of facilitating a transition to green energy by 2028-29. Further, an HVDC link between Madurai, India, and New Habarana, Sri Lanka, with 2×500 MW HVDC terminals is in advanced stages of discussion.
In conclusion, India’s robust plans for renewable energy integration demonstrate a clear commitment to sustainable energy goals. Despite challenges in infrastructure development and financing, strategic initiatives, including green energy corridors and advanced grid management technologies, aim to address these hurdles.
Aastha Sharma