The Indian power transmission segment has grown significantly over the years to cater to the rise in generation capacity and power demand, making the country’s electricity grid one of the largest synchronous grids in the world. The segment is now set for another phase of accelerated growth, primarily driven by the need to evacuate large-scale renewables. With India aiming to meet 50 per cent of its energy needs from renewables and achieve 500 GW of non-fossil fuel capacity by 2030, significant expansion and strengthening of the interstate transmission system (ISTS) and intra-state transmission system will be required.
As a significant step towards successfully achieving the planned renewable energy capacity by 2030, the Central Electricity Authority (CEA) recently came out with a transmission system plan for the integration of about 537 GW of renewable energy capacity, which requires significant expansion and strengthening of the ISTS system. As per the report, a transmission line length of 50,890 ckt. km and a substation capacity of 433,575 MVA at the ISTS level are required for integration of the additional wind and solar capacity by 2030, entailing a total cost of Rs 2,442 billion.
Network size and growth
As of May 2023, the total transmission line length (at the 220 kV level and above) stood at 472,345 ckt. km, the total alternating current (AC) substation capacity stood at 1,156 GVA and the high voltage direct current system (HVDC) substation capacity stood at 33,500 MW.
Between 2016-17 and 2022-23, the line length has grown at a compound annual growth rate (CAGR) of 4.2 per cent, while AC and HVDC substation capacities have grown at 8 per cent and 9.4 per cent respectively. In absolute terms, about 103,490 ckt. km of lines, about 425,587 MVA of AC substation capacity and 14,000 MW of HVDC substation capacity have been added during this period.
The interregional transfer capacity has grown considerably over the years, from about 75,050 MW in 2016-17 to 112,250 MW in 2022-23, recording a CAGR of 6.9 per cent.
Update on various programmes and initiatives
Green energy corridors: Initiated in 2015, GEC is a key programme for renewable energy evacuation in the country. Under GEC Phase I, 3,200 ckt. km of ISTS lines and 17,000 MVA of substation capacity have been commissioned. The intra-state GEC-I component of 9,700 ckt. km transmission lines and 22,600 MVA capacity substations is expected to be completed by March 2023. As of October 2022, 8,651 ckt. km of intra-state transmission lines have been constructed and 19,558 MVA of substation capacity has been charged.
The intra-state GEC Phase II scheme, approved by the cabinet in January 2022, envisages an intra-state transmission line length of 10,750 ckt. km and a substation capacity of 27,500 MVA, scheduled for commissioning by March 2026. The transmission scheme is currently under implementation by transmission utilities of seven states – Gujarat, Himachal Pradesh, Karnataka, Kerala, Rajasthan, Tamil Nadu and Uttar Pradesh – for evacuation of approximately 20 GW of renewable power.
Transmission scheme for renewable energy zones: Transmission systems have been planned for major renewable energy potential zones such as the Leh renewable energy park in Ladakh; Fatehgarh, Bhadla, and Bikaner in Rajasthan; the Khavda renewable energy park in Gujarat; the Anantapur and Kurnool renewable energy zones in Andhra Pradesh; and offshore wind farms in Tamil Nadu and Gujarat under the recently released CEA Report for Transmission System Integration of 500 GW of renewable energy by 2030.
As per the report, under the “Transmission System for 66.5 GW ISTS connected Renewable Energy Capacity” section, a part of the transmission system has already been commissioned (13 GW). The rest is at various stages of implementation/bidding/planning. Around 19 GW is under construction (slated for commissioning between December 2022 and November 2023); 8 GW under tendering; 10.5 GW to be undertaken for bidding and the rest of the capacity is at various stages of planning. Further, a transmission system has been planned for 236.58 GW (55.08 GW+181.5 GW) of renewable energy capacity, which is at various stages of implementation including approval and tendering.
The battery energy storage system capacity needed for the projected renewable energy capacity is 51.5 GW by 2030. A margin of about 33,658 MW is already available in existing/under-construction ISTS substations, which can be used for renewable energy integration. Further, transmission system has been planned for about 16,673 MW of additional hydro capacity likely to be commissioned by 2030. Other planned transmission schemes will be taken up progressively for implementation, commensurate with the renewable energy capacity. Additional transmission systems would be planned, based on the progress of green hydrogen manufacturing and the emergence of additional renewable energy potential sites.
TBCB update: As of April 2023, 77 ISTS projects have been bid out to public and private players since 2009 through the TBCB mechanism (excluding four projects that have been cancelled or are under litigation). Of these, 32 projects have been secured by Powergrid and 45 have been won by private players. Of the private sector projects won so far, 29 have been commissioned and the remaining 16 are under construction. Of Powergrid’s projects, 15 have been commissioned and 17 are under construction.
Cross-border interconnections: The existing cross-border interconnections have a transmission capacity of about 4,230 MW and this is planned to be increased to about 6,450 MW progressively over the next few years. Several interconnections are planned between India and neighbouring countries, including a new 765 kV link between India and Bangladesh; and the 400 kV new Gorakhpur and new Butwal transmission lines between India and Nepal. Further, there are plans for the development of an overhead electricity link with Sri Lanka, after the earlier proposal to set up an undersea power transmission link was shelved due to high cost.
The transmission segment is at the forefront of adopting the latest technology. The key drivers for technology advances in cables and conductors, tower designs, transformers and substations have been addressing right-of-way issues, optimising space, reducing visual impact, lowering cost, reducing failure rate, increasing asset life, moving to higher voltages and increasing loadability.
A task force set up by the power ministry in 2021 under the chairmanship of Powergrid with the CEA, state transmission utilities, central transmission utility and others as members has recommended centralised remote monitoring, operation of substations including supervisory control and data acquisition, flexible AC transmission devices, dynamic line loading systems, wide area measurement systems using phasor measurement units and data analytics, hybrid AC-HVDC, predictive maintenance techniques using artificial intelligence/machine learning algorithms, high temperature low sag conductors, process bus-based protection automation and control, gas-insulated switchgear/hybrid substations, cybersecurity, energy storage systems, and drones and robots in the construction/inspection of transmission assets.
A major issue faced by transmission developers is limited right of way, especially in urban areas, which often leads to project delays and cost overruns. Further, large-scale integration of renewables poses challenges for grid stability, leading to demand-supply imbalance, and voltage and frequency instability. Moreover, the shorter gestation period of renewable projects vis-à-vis transmission projects may cause stranding of upcoming renewable capacity. Besides, for ageing infrastructure networks, upgradation and modernisation need to be undertaken in a phased manner to improve operational efficiency. With the increasing integration and digitalisation of the network, there is an increased threat of cybersecurity breaches.
The way ahead
The cumulative interregional transmission capacity is likely to be around 150,000 MW in 2030. Significant investments are thus required for strengthening and ramping up the country’s transmission infrastructure to meet the future peak load as well as to integrate expanding renewable energy capacity. The roadmap for ISTS transmission capacity development, as outlined in the CEA’s report, will help transport the targeted solar and wind power to load centres and bring the country closer to its clean energy mix goals. In addition to expanding the physical grid, utilities will increasingly need to invest in advanced and grid-enhancing technologies to improve capacity, grid resilience and stability, going forward.