The demand for substations is growing rapidly in the country, driven by the expansion of the transmission and distribution (T&D) network and the growing integration of renewable energy. Various government schemes have been formulated to strengthen and modernise the T&D network. Transmission utilities are focusing on augmenting substation capacity to further enhance the network and enable greater renewable energy integration. The Revamped Distribution Sector Scheme also lays emphasis on network modernisation and upgradation in the distribution segment. These factors are driving the demand for substations in the sector.
In order to meet the emerging requirements, utilities are adopting new substation designs and technologies. They are also investing in solutions to reduce the environmental impact of the segment and deploying digital technologies and internet of things to facilitate automated operations, energy management and smart grid operations. Renewable Watch provides an overview of the technology trends in the substation market and the implications of the segment on renewables uptake in India…
Types of substations
A substation is an electrical system capable of handling high voltage. The primary task of a substation is to deliver a steady supply of electricity from the power plant through the transmission system to the final consumer. There are different types of substations for the efficient operation of the power grid. According to their intended use, substations can be classified as indoor, outdoor, power generation and converter substations. A typical substation switches from one transformer to another with low-voltage equipment.
There are different types of substations available in the market. Air-insulated substations (AISs) use air to insulate various live parts and have traditionally been used for power transmission in India. However, with the increase in space constraints, land costs, renewable energy and electric vehicle (EV) penetration, the emphasis is shifting towards substation and switchgear technologies that require less space and are more reliable. Gas-insulated substations (GISs) have emerged as a popular choice as they use sulphur hexafluoride gas, which helps reduce the distance between active and non-active switchgear parts, resulting in reduced space requirements. GIS can also be installed both indoors and outdoors. Hybrid substations are a combination of AIS and GIS technologies and can be installed both indoors and outdoors, making them ideal for space and money savings.
The concept of digital substations is also gaining traction. They occupy less space than traditional substations. Further, smart digital substations can be helpful during extreme weather conditions because they can effectively reroute electricity to minimise the loss and damage of assets. Given the quick uptake of renewable energy generation, digital substations are urgently needed. They can effectively manage load and supply while accounting for real-time developments, providing continuous electricity in accordance with demand and supply dynamics. Mobile substations are also a common type of substation owing to their portability. They can easily be transported to areas with high electricity demand.
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. Digital substations primarily enable 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 the 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.
Implications for renewables uptake
As per the Central Electricity Authority’s report on “Transmission System for Integration of over 500 GW RE Capacity by 2030”, around 25,000 MW of high-voltage direct current transformation capacity is expected to be added at the interstate level by 2030. Voltage-wise, the expected additions are 20,000 MW at the ±800 kV level and 5,000 MW at the ±350 kV level. Meanwhile, alternating current substation capacity of 408,575 MVA is expected to be added by 2030, of which 274,500 MVA is expected at the 765 kV level and 134,075 MVA at the 400 kV level. Overall, the interstate transmission system will require an investment of about Rs 2.44 trillion.
According to the report, approximately 33,658 MW is already available in existing/under construction inter-state transmission system (ISTS) substations and can be used for the integration of renewables. This comprises 15,058 MW and 18,600 MW at the 220 kV level and 400 kV level, respectively. Region-wise summary of margin available in ISTS sub-stations is: northern (5,250 MW), western (9,628 MW), southern (5,630 MW) and eastern (13,150 MW).
India’s power sector is witnessing significant investments in the renewable energy segment, including wind and solar power, with the aim of mitigating carbon emissions. The increasing adoption of renewables has increased grid management requirements. The power generated from these so-urces is inherently inconsistent, relying on favourable weather conditions. If not efficiently managed, the dynamic power flow brought in by renewable energy generation could pose risks to grid stability. Furthermore, utilities may face significant challenges in balancing consumer supply and demand due to the volatile nature of renewable energy sources such as solar and wind. The use of distributed renewable energy generation systems, numerous non-linear loads, EV charging, etc., are increasing the complexity of electrical grid systems. This calls for the development of smart grid technology to assist utilities in managing power demand across their entire distribution network, including substations. The growing integration of renewable energy into the grid creates a need for automatic switchgear and substation solutions that provide better monitoring and control capabilities. Going forward, renewable energy addition requires transmission network expansion, which will create demand for innovative substation technologies and enable capacity expansion of substations.
