The Indian power grid is becoming increasingly complex owing to the integration of large-scale renewables, growth in decentralised generation, penetration of electric vehicles and rise in digital loads. This necessitates electric utilities to take steps to expeditiously expand their transmission networks and strengthen their existing transmission links to ensure a seamless flow of power. The management and control of the evolving transmission system require the deployment of smart grid solutions, digital substations, and greater automation in load management and power despatch. New-age technologies such as internet of things (IoT), machine learning (ML) and artificial intelligence (AI) are gradually gaining prominence in the segment for intelligent decision-making and greater reliability.
A digital substation is a crucial component of the smart grid in the power transmission segment. In a digital substation, fibre optic cables replace traditional copper connections that use analogue signals. One of the key features of a digital substation is the implementation of a process bus based on the IEC 61850 protocol. The process bus replaces hard-wired connections with communication lines, enabling the deployment of optical fibre network (Ethernet based) instead of copper wiring between intelligent electronic devices and various other equipment. This allows the substation’s status and performance parameters to be shared in real time through digital signals without complicated wiring. Transformers and switchgear continuously transmit data over the process bus and to any upstream devices for protection, measurement, metering and monitoring.
Digital substations incorporate integrated information and real-time communication technologies, which are interfaced with process bus and station bus architecture. Installing digital substations primarily enables the integration of real-time data and data analytics into the system, facilitating more accurate decision-making, reduced downtime and enhanced diagnostics. Real-time diagnostics, in turn, help eliminate the need for troubleshooting and reduce the cost and time expended on repairs and maintenance through timely diagnosis of problems in the substation. Other intangible benefits of digital substations include improved productivity and functionality, greater asset reliability, substation operator safety, and lower cost and space requirements.
In December 2020, Power Grid Corporation of India Limited (Powergrid), in collaboration with Bharat Heavy Electricals Limited, successfully commissioned India’s first indigenously developed 400 kV optical current transformer and digital substation components at the 400/ 220 kV Bhiwadi substation. Powergrid has also commissioned a digital substation based on IEC 61850 process bus technology at Malerkotla, Punjab. The technology provides flexibility in engineering, paving the way for faster commissioning, reduced downtime, enhanced diagnostics and ease in troubleshooting during asset management.
The primary function of SCADA is data acquisition from across the system, followed by visualisation of the acquired data for the grid operator. The arithmetic logic unit functionality in SCADA is used for decision-making, applied in the automatic demand management system, condition-based load shedding, undervoltage monitoring scheme, or any other critical monitoring applications. It is an effective tool for utilising the power grid during contingencies and avoiding voltage collapse, cascade tripping, load generation mismatch and blackouts in the grid. GETCO has undertaken a smart grid project using SCADA.
The system includes an automated distribution management system, a renewable energy management centre, an energy accounting and scheduling system and a smart grid feeder management system. Meanwhile, Karnataka Power Transmission Corporation Limited’s SCADA system has an automatic generation control module, which helps continuously balance the system, maintain a constant frequency and eliminate area control error.
The basic infrastructure of the wide area measurement system (WAMS) technology comprises phasor measurement units (PMUs) and wideband communication network and phasor data concentrator (PDC) units. PMUs are devices that measure the electricity flow, voltage and current magnitude, frequency levels, rate of change of frequency, and phase angle through the grid using a common time source (GPS) for synchronised data collection. As part of WAMS implementation, PMUs are dispersed throughout the electricity grid and placed at strategic locations in order to cover the diverse footprint of the grid. The PDC unit is installed at the central location. It collects the information from PMUs and sends out alerts and alarms in emergency situations. It facilitates the development of different types of analytics for smooth grid operation. The PMU data is also transmitted to the SCADA system. These systems not only address the immediate reliability concerns but also operational issues such as enhancing power transfer capability in real time and blocking/de-blocking of distance relay zones in case of power swings.
Powergrid is implementing WAMS technology across India under its flagship Unified Real Time Dynamic State Measurement project. In July 2018, GE T&D India Limited commissioned the first stage of the project, which will enable Powergrid to monitor the power flow across 110 substations in the northern grid and respond to fluctuations within a fraction of a second. When fully commissioned, the project will be the largest in the world comprising 1,184 phasor measurement units and 34 control centres across the country. It will cover over 350 substations in the national grid.
Remote monitoring centres
The transmission utilities are increasingly adopting remote monitoring solutions for effective monitoring of power transmission assets and reduced manual intervention in network operations. In order to facilitate the remote operation of transmission systems and monitoring of various parameters in real time, Powergrid has set up the National Transmission Asset Management Centre at Manesar, near Gurugram, Haryana, and regional transmission asset management centres at various locations across the country. These state-of-the-art centres are manned round-the-clock by experts for monitoring and management of transmission assets. During 2021-22, 22 additional extra high voltage substations were integrated with NTAMC for remote operation. By the end of 2021-22, a total of 264 substations were being operated remotely from these asset management centres.
One of the key technologies that is transforming the operations and management of power transmission is internet of things (IoT). The implementation of IoT in the transmission system provides effective line monitoring and real-time control of various grid operating parameters. With the use of IoT, ML and AI, the transmission utilities are increasingly moving to predictive maintenance strategies that leverage data analytics tools to forecast equipment health. Utilities are moving to condition-based monitoring, where maintenance of assets is carried out when certain indicators signal that the equipment is deteriorating and the probability of failure is increasing. This approach helps in significantly reducing maintenance costs in the long run, minimising the occurrence of serious faults and optimising the management of available resources.
For the successful roll-out of digital technologies and smart grid solutions, utilities must identify the most suitable technologies and develop a roadmap for technology adoption. The implementation of technologies in isolation may not deliver the desired result, and an integrated approach is essential. Apart from this, with greater interconnectedness in the network, the risk of cybersecurity breach is higher and utilities must adopt a robust cybersecurity framework to ensure safe operations. It is also essential for utilities to provide adequate manpower training, build capacity and manage change to facilitate the smooth adoption of these technologies.