The transmission grid faces numerous challenges. Renewable energy integration is the biggest challenge. Based on the agenda of COP26, India needs to integrate over 500 GW of renewable energy by 2030. Thus, the transmission segment needs to work proactively to establish transmission infrastructure to keep pace with upcoming renewable energy projects and evacuate green energy.
Renewable energy integration poses challenges of low-capacity utilisation and missing dynamic reactive compensation. It is seasonal in nature, non-despatchable and is often characterised by resource availability at remote locations. There is also an absence of inertial support. Hence, there is an urgent need for consistently high availability of power from a transmission system that is reliable and can tackle this intermittency.
Evacuating renewable power often comes with the challenge of distance and terrain. Be it offshore wind projects or solar plants in Rajasthan or Leh, transmission assets in these areas face both these challenges as power has to not only be transmitted over long distances but often through very difficult and geologically fragile terrain.
Transmission, being the crucial part in this connectivity, is all the more burdened and transmission assets need to be in good health to support power evacuation and grid stability. Hence, maintaining asset health is all the more challenging and necessary.
Voltage variation can easily trigger variations in system parameters and with this, another challenge that has emerged is to ensure that system parameters fall within the acceptable bandwidth in order to maintain power quality. Transmission structures now need to be more resilient to reduce forced outages and tripping.
Meanwhile, more subliminal challenges have come up. With the advent of IoT in power, there is a pressing need to protect transmission systems from cyberattacks. In order to accommodate this technological shift, manpower needs to be upskilled for these developments. Hence, these are unpredictable times for the transmission segment, faced with numerous challenges.
Solutions and strategies
In order to facilitate renewable energy integration, potential renewable energy zones need to be identified. Transcos need to develop transmission infrastructure based on potential renewable energy zones, which are identified based on resource and wasteland availability. The grid needs to be expanded to those zones.
To manage the seasonality of renewable energy, a key technology that will be used is energy storage systems (ESS). An ESS uses devices (a battery or accumulator) that store energy in forms such as chemical, electrical potential, electricity, elevated temperature, etc., and then converts it from these forms. Robust energy storage systems can help mitigate the intermittency of power and increase the utilisation of transmission assets. ESS is key to the energy transition as it can add flexibility and resource availability to an otherwise uncertain system. It can also defer capex for transmission companies. Hybrid generation can also help mitigate the seasonality of renewable energy. Renewable energy management centres for forecasting and scheduling can make the grid more reliable and manage demand-side integration.
Another strategy to improve renewable energy integration is to invest in better transmission infrastructure, which includes software for forecasting and stability inducing software static synchronous compensator (STATCOM) and static VAr compensator (SVC), along with various types of bipoles that can help in bulk power transfer.
Using dynamic reactive power compensating devices and forecasting of renewable power output can save both time and energy and contribute to power reliability. Synchronous condensers can help provide inertial support. Both these initiatives can improve power quality and make transmission cost-effective and efficient.
Also, in October 2021, the Central Electricity Authority (CEA) released guidelines for cybersecurity in the power sector. While most of the utilities in the power sector have their own cyber crisis management plans, a major issue in grid security emanates from operating legacy systems. To mitigate the risks, utilities need to have a strong and secure password protected system, secured firewalls, intrusion detection and intrusion prevention systems, regular backup of data, vulnerability assessment and penetration testing. Utilities should also get their critical information infrastructure audited from a Computer Emergency Response Team empanelled cybersecurity auditor and ensure training of their IT personnel.
Utility experience and plans
As mentioned above, technological upgradation plays a key role in unlocking the potential of the transmission segment. Many power utilities are actively engaging in upgrading transmission technologies and tower equipment.
Power Grid Corporation of India Limited (Powergrid) is using state-of-the art equipment to achieve its goals. The company has deployed 765 kV EHVAC, ±800kV 6,000 MW HVDC, ±320kV 2,000 MW VSC HVDC with underground cables in its various projects. It is also using pole type, narrow-based, multi-circuit towers to overcome RoW issues. Other technologies in use are the process bus-based protection automation and control, coupled with flexible AC transmission devices such as STATCOM, SVC and FSC (fixed series capacitor). Powergrid relies on centralised remote monitoring and operation of substations, wide area measurement system using phasor measurement units, advanced diagnostic tools and condition monitoring of equipment in asset management. Powergrid is also undertaking re-conductoring of existing lines, live line maintenance and app-based transmission line health monitoring to maintain the transmission asset health.
Dynamic line loading systems, predictive maintenance techniques using AI/ ML algorithms, energy storage systems, digital twins for vegetation management and virtual and augmented reality for asset management are some of the other promising technologies that it seeks to deploy in its upcoming projects. Similarly, state utility Gujarat Energy Transmission Corporation Limited has adopted technologies such as GIS and hybrid switchgear and HTLS (hight tension low sag) conductors for its transmission infrastructure. It also routinely conducts geographic information system mapping of transmission assets and has an integrated asset management system with real-time grid visualisation software, along with a substation automation system (installed at 53 substations), which have greatly helped in maintaining asset health and efficiency of power transmission. It is also constructing a fully digital substation at Sevaliya and installing STATCOMs for dynamic reactive power compensation at the 220 kV Timbdi substation.
North East Transmission Company Limited (a joint venture of ONGC Tripura Power Company Limited, Powergrid, Assam Electricity Grid Corporation Limited) is focusing on new initiatives such as aerial patrolling, remote monitoring and use of advanced O&M instruments for addressing challenges in its network and building climate-resilient infrastructure. Advanced information systems, which can help in preparedness for cyclones, earthquakes and lightning are also being looked at to achieve 100 per cent availability. Further, it is exploring the use of 400kV transmission line arrestors.
Outlook
As the country undertakes the transition in its generation segment, new challenges are emerging for the transmission segment. Not only do newer sources of power have to be integrated into the grid, but technology upgrades need to be undertaken in order to transfer large amounts of power and cope with the speed of the transition. With new projects being allocated, the transmission segment needs to keep pace by building new lines while simultaneously upgrading its older assets.
The above-mentioned technologies can facilitate the transition towards renewables, along with strategic interventions for the construction of a robust transmission system. Strategies such as interconnections between intra-regional and interregional grids; adopting a fully automated, digitally controlled and responsive smart grid; and fiberisation of transmission infrastructure can set the ball rolling for long-term power reliability. Also, deploying optical ground wire and ESS will help tackle the uncertainty associated with renewable energy.
Making active efforts to ensure cybersecurity will prevent power theft and grid hacking events and save countless outages and resources, while building climate resilient systems will reduce capex and enable preventive maintenance.
In addition, upskilling and reskilling of the workforce can help bridge gaps in management and administration. These “softer” strategies can make a larger difference and, coupled with other moves, can ensure a durable and reliable transmission system.
