At the COP26 conference, India pledged to increase its non-fossil fuel capacity to 500 GW, meet 50 per cent of its energy requirements from renewable energy by 2030, and achieve net zero by 2070. Hence, creating transmission evacuation infrastructure for renewable energy generating plants is imperative. The transmission system has to be planned in advance as the gestation period of wind- and solar-based generation projects is shorter than that of the associated transmission system. For enabling growth of renewable energy capacity, areas which have high solar and wind energy potential need to be connected to the inter-state transmission system (ISTS); this will enable evacuation of power to the load centres.
To this end, the Central Electricity Authority (CEA) has released a report, “Transmission System for Integration of over 500 GW Renewable Energy Capacity by 2030”. In the report, the transmission system has been planned for about 537 GW of renewable energy capacity, with major renewable energy potential zones as well as offshore wind farms in Tamil Nadu and Gujarat in mind. Several HVDC transmission corridors have also been planned for the evacuation of power from large renewable energy potential zones.
Need for transmission planning
There is a paradigm shift in the development of renewable energy infrastructure. Earlier, the gestation period for conventional power plants was high, in the order of four to five years. However, the gestation period for renewable energy generation is less than two years and transmission system development also requires at least two years. Therefore, it is essential to develop the transmission system based on the potential with proper renewable integration planning and development. In line with this, the MNRE and SECI have identified the potential zones to carry out transmission planning and establish the transmission system.
Unlike conventional power generation in the eastern parts, more renewable energy plants are being developed in the western and southern parts. Hence, new systems need to be planned based on geography. In addition, the Indian power system is interconnected with Nepal, Bhutan, Bangladesh and Myanmar. Cross-border connectivity plays a vital role in large-scale integration of power resources. Interconnected systems are beneficial in sharing the balancing reserves through large interconnected power systems.
Going forward, energy storage systems, including battery energy storage systems and pump storage systems, would be required to meet the future electricity requirement. Further, the adoption of electric vehicles is expected to grow. These changes to the generation-resource mix necessitate careful transmission planning.
Road map of transmission system
According to the roadmap released by the CEA, the transmission system has been planned for 537 GW renewable energy capacity by 2030. Overall, the CEA has estimated that 50,890 ckt. km. and 4,33,575 MVA of ISTS transmission line length and substation capacity, respectively, would be required for the integration of additional wind and solar capacity by 2030 at an estimated cost of Rs 2,442 billion.
According to the plan, the entire green energy corridor-I (GEC-I) has been commissioned for evacuation of 6,000 MW of power. GEC-II for seven ultra mega solar park projects across five states is also complete. Overall, under both GEC-I and GEC-II, 3,200 ckt.km and 1,842 ckt.km of transmission lines have been implemented under the two phases respectively. Meanwhile, 17,000 MVA and 13,500 MVA of transformation capacity has been established under GEC-I and GEC-II, respectively.
The plan envisages transmission systems for 66.5 GW from potential renewable energy zones, of which 50 MW is solar and 16.5 MW is wind. Out of this, transmission systems for 9.5 GW have already been commissioned and the balance is under implementation or tendering. In addition to the 66.5 GW capacity, another 181.5 GW of renewable energy potential is planned to be developed by 2030. Of this, 75 GW is planned for northern region, and 86 GW and 20.5 GW is planned for southern and western region respectively.
Transmission infrastructure has been planned for about 16,673.5 MW additional hydro capacity likely to be commissioned by 2030. Additionally, a BESS capacity of 51.5 GW and off-shore wind energy integration of 10 GW through submarine cables have been considered under the plan.
Challenges in renewable energy integration
A key challenge with renewable energy resources is that they are not evenly distributed across the country and are location specific. Further, land availability and political will determine a state’s progress in terms of renewable energy expansion, leading to a geographically skewed proliferation. This creates issues in grid management, often hindering the large-scale deployment of renewables in resource-rich states. Thus, it is important that renewable power is transported via transmission systems to renewable-deficit states for balanced distribution of resources.
Another issue in renewable energy generation is the low capacity utilisation factor compared to conventional power generation. For optimal utilisation of the transmission system, implementation of battery energy storage systems (BESS) is required. The government has come out with various enablers to introduce BESS in the country. This includes waiver of ISTS charges, standard bidding guidelines for standalone storage, ancillary services guidelines, storage as part of the National Renewable Energy Hybrid Policy, TBCB guidelines for energy storage, and viability gap funding to support 4,000 MWh storage by 2027-28.
Power system operation under renewable energy integration is a challenge. To integrate power systems into the country, there are two basic challenges – equality constraint and inequality constraint. In equality constraint, generation is matched with the load. In inequality constraint, operating voltage, line loading generator and transformer rating need to be within certain limits. If these two constraints could be matched, then the power system can be securely and safely operated.
Other challenges associated with renewable energy integration are low capacity utilisation of renewable energy plants, missing dynamic reactive compensation, absence of inertial support, seasonal nature of renewables, non-dispatchable variability and uncertainty associated with renewable energy generation, among others. Further, to mitigate challenges in renewable energy integration, advanced planning based on potential, in a phase manner, needs to be done. Further, it requires deployment of hybrid generation, STATCOM/SVC, demand side integration, wide area measurements, REMC for forecasting and scheduling, and automation.
The government has come up with various regulations for enabling renewable energy integration. This includes the notification of Connectivity and GNA Regulations 2022, waiver of interstate transmission charges for solar and wind projects commissioned till June 2025, transmission systems for renewable energy to be considered as national component for calculation of inter-state transmission charges, technical standards for connectivity of distributed generation resources, regulations incentivising flexibility, and introduction of real-time power markets on exchanges.
The Indian power system has around 411 GW of installed capacity; this is expected to be increased to around 776 GW by 2030. Currently, renewable energy has around 30 per cent share in the total installed capacity, comprising generation from non-fossil fuels such as wind, solar, nuclear, biomass and hydro. By 2030, the share of renewable energy will increase to around 500 GW or 53 per cent in the total energy mix. By 2030, peak demand and annual consumption is projected to increase from around 216 GW and 1,375 BUs to around 335 GW and 2,308 BUs, respectively. Currently, the inter-regional transmission capacity of the country is around 112,250 MW. With the additional inter-regional corridors under implementation/planned, the inter-regional capacity is likely to be 149,850 MW by 2030.
Successful implementation of transmission projects, given the right-of-way issues that continue to exist, would be critical to meet the transmission plans outlined in the report and avoid project delays and cost overruns. However, despite these concerns, the detailed report on transmission infrastructure for evacuation of renewables is a positive step forward and will help in scaling up renewables.
Going forward, dynamic compensation to maintain grid parameter and stability is planned. Further, new technologies, an ancillary services market, awareness and capacity building are being introduced for renewable energy integration. These measures will help in transmission capacity development, which, in turn, will help transport solar and wind power to load centres and bring the country closer to its clean energy goals.
Based on a presentation by the Central Transmission Utility of India at a recent Power Line conference