The Indian transmission segment is growing at a fast pace to support the country’s decarbonisation goals and connect 500 GW of clean energy (non-fossil fuel based) to the grid. Besides growth in the physical network, the segment is witnessing a technological transformation as utilities take steps to adopt solutions such as flexible AC transmission systems (FACTS) and battery energy storage systems (BESSs), which are necessary to improve grid reliability in the wake of increasing integration of highly variable renewable energy generation. There is also a shift towards smart sensors, digital solutions and advanced technologies like IoT, AI and ML to improve the management of the rapidly growing transmission network. An account of the key emerging technologies in transmission…
FACTS
FACTS devices such as static VAR compensators (SVCs) and static synchronous compensators (STATCOMs) are expected to play a key role in grid operations as greater renewables are integrated into the grid. These power electronic devices provide dynamic voltage support, thereby ensuring grid reliability and voltage stability. Powergrid has already installed advanced STATCOMs in the 400 kV network as well as a thyristor controlled reactor (500 MVAR) in Kurukshetra to improve the static as well as dynamic voltage profile of the Kurukshetra high voltage direct current (HVDC) station. The utility has commissioned STATCOMs at 14 substations in the past few years – Solapur, Aurangabad, Satna and Gwalior in the western region; Lucknow and Nalagarh in the northern region; Ranchi, Rourkela, Jaipur and Kishanganj in the eastern region; and Udumalpet, Trichy, Hyderabad and NP Kunta in the southern region. It has also deployed a STATCOM at its Mahendragarh substation, which has helped in reducing load profile changes as well as auxiliary power consumption. Besides STATCOMs, SVC technology, which is being deployed in several substations, enhances the capacity, security and flexibility of power transmission systems. For instance, two SVCs with 140 MVar inductive capacity each were installed at the Kanpur substation on the Rihand-Delhi HVDC line. These SVCs helped avert a cascade tripping across the network when the grid voltage dipped by 10 per cent on a faulty line.
BESS
Energy storage has become crucial for grids aiming for high renewable energy integration. In 2022, the Ministry of Power notified the “Guidelines for procurement and utilisation of BESS as part of generation, transmission and distribution assets, along with ancillary services”. The objectives of these guidelines are to facilitate the procurement of BESS, as part of individual renewable power projects or separately, to address variability, firm up power supply, increase the energy output, extend the time of supply from renewable energy projects, augment existing renewable power projects, and provide ancillary, grid support and flexibility services for the grid; enable optimum utilisation of the transmission and distribution network; ensure transparency and fairness in the procurement process; provide a framework for an intermediary procurer to act as an aggregator, trading licensee and implementing agency for the interstate/intra-state sale and purchase of power; and introduce standardisation and uniformity in processes and a risk sharing framework between various stakeholders involved in energy storage and storage capacity procurement, thereby encouraging competition and enhancing the bankability of projects.
Powergrid is actively planning to invest in BESSs. In 2021, Powergrid’s 500 kW BESS pilot project based on lithium-ion phosphate and lead acid batteries went live in Puducherry. The BESS pilot is aimed at demonstrating various possible use cases through enhanced IT-based controls, ascertaining the feasibility of BESS in the grid, and assessing the economic value of storage. It will be an important contribution to India’s energy sector. The utility is also implementing a 500 kW energy storage project at Gurugram, Haryana, and a 5 MW BESS in Nagda, Madhya Pradesh.
Reportedly, the government plans to invite bids for setting up around 4 GWh of grid-scale BESSs at the regional load despatch centres. Last year, NTPC Limited floated a global tender for setting up a 1 GWh grid-scale BESS.
Notably, the Central Electricity Authority’s (CEA) recently released report “Transmission System for Integration of over 500 GW RE Capacity by 2030” envisages nearly 51.5 GW of BESS capacity in the country over the next decade. A key proposed project is a 12 GWh BESS at Leh, out of which 1 GWh has been planned as a transmission element and the balance 11 GWh will be installed as part of renewable energy generation projects.
HVDC
HVDC technology enables long distance transmission with minimal losses vis-à-vis high voltage alternating current (HVAC) lines. It is set to grow in the coming years especially as India takes steps to realise its offshore wind goals. Though it is an established and known technology in India that has been in existence for over 60 years, there are only a few HVDC links in the country. The CEA’s recent report on RE integration envisages several new HVDC corridors for the evacuation of power from large renewable energy potential zones. These include the ±800 kV Barmer II (Rajasthan)-Jabalpur (MP) HVDC line, the ±800 kV Bhadla III-Fatehpur HVDC line, the ±350 kV Pang-Kaithal HVDC line, the ±800 kV Barmer II-Jabalpur HVDC line, and the ±800 kV Khavda-Aurangabad HVDC line.
Asset management technologies
Transmission utilities are increasingly moving to predictive maintenance strategies, which call for actions to be taken based on equipment health forecast through the use of data analytics tools for objective decision-making. Some of the key factors considered under the strategy are design and voltage class, past operational history, failure trend, service age and health index.
Remote monitoring of transmission assets has gathered pace, especially after the Covid-19 pandemic. Powergrid’s National Transmission Asset Monitoring Centre (NTAMC) at Manesar, Haryana, facilitates remote operation of the company’s transmission system and monitoring of various parameters on a real-time basis at regional and national levels. Likewise, regional transmission asset monitoring centres have been set up at various locations across the country. These state-of-the-art centres are manned round the clock by experts for effective monitoring and management of transmission assets. During financial year 2021-22, two additional extra high voltage substations were integrated with the NTAMC for remote operation, taking the total remotely monitored substations to 264.
Transmission companies are also adopting technological tools such as drones with thermovisual scanning, high resolution videos and corona cameras for patrolling transmission lines, substations and reactors in real time. Today, utilities can rapidly and effectively identify vulnerabilities of the transmission grid with the help of drones. Aerial surveillance as well as remote airborne inspection and scanning devices are more effective, less expensive, and quicker than traditional line patrolling methods based on monkey patrols and on-ground procedures. These imageries can be used to develop intelligent digital twins integrated with AI, which can accurately recreate transmission lines and towers to optimise asset maintenance and records.
Emerging switchgear and substation technologies
The segment has witnessed an increase in the demand for intelligent switchgear, which has built-in protection and control intelligent electronic devices (IEDs) in their switchgear solutions. These new IEDs, combined with the latest information and communication technologies, form a base for enhanced protection, control and monitoring. Intelligent switchgear can connect with the internet and provide comprehensive monitoring and protection functions, as well as measure all electrical parameters in real time. Intelligent switchgear can significantly enhance the efficiency and reliability of the grid and help utilities avoid blackouts and equipment failures.
Substation technologies have also evolved considerably to meet the emerging requirements of utilities and adapt to the changing grid. New designs and features have been driven by considerations such as space optimisation, lower costs, greater asset life, enhanced safety and reduced failure rates of equipment. Conventionally, utilities installed AIS, which uses air for insulation between various live parts. A key trend is the growing installation of GIS and hybrid substations in place of conventional AIS substations as Indian utilities grapple with right-of-way and land acquisition issues. In addition, digital substations are gaining traction across utilities as digitalisation enables utilities to identify, prevent and rectify faults through the use of sensors and IEDs.
Further, the deployment of the IEC 61850 protocol has provided seamless communication and integration between IEDs. In addition, the application of process bus architecture in digital substations helps add flexibility by enabling digital devices to communicate directly with each other. Process bus also allows for the replacement of bulky copper wiring with optic fibre, making digital substations more compact and safer than conventional substations. Further, the pandemic has accelerated the need to automate and digitalise power systems and equipment. T&D utilities have increasingly realised the importance of unmanned substations and remote operations and maintenance of assets with local/national lockdowns in the past two years. Consequently, substation automation and remote monitoring solutions are gaining traction.
Conclusion
A technological shift in the transmission segment is the need of the hour to facilitate the ongoing energy transition. Utilities need to prepare a technology roadmap to ensure the grid is operated in a smooth and reliable manner.
