The rise of green energy has increased the grid management requirements. The power generated from these sources is inconsistent as it is dependent on favourable weather conditions. If not managed properly, the dynamic power flow brought in by renewable energy generation could put grid stability at risk. 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, electric vehicle (EV) charging, and other factors 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 and transformers. In light of this, rapid technological advances have taken place in critical power system components. For instance, substation automation technologies have gained traction. Further, there is a demand for next-generation transformers that align with the smart grid. The increasing share of renewable power in the total energy mix is one of the primary reasons that the market for such components is expected to expand in the coming years.
A substation is simply an electrical system capable of handling high voltage. The main task of a substation is to deliver a steady supply of electricity from the power plant through the transmission system to the final consumer. Different types of substations are designed for the efficient operation of the power grid. According to their intended use, substations can be classified as either 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 EV penetration, the emphasis is shifting more to 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 (SF6) gas, which helps in reducing 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. Digital substations 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. Digital substations can effectively manage load and supply while taking into account real-time developments because they can provide continuous electricity in accordance with demand and supply dynamics. Due to their portability, mobile substations are also a common type of substation. They can easily be transported to areas with high electricity demand.
Transformers help in increasing or decreasing the voltage as they move electrical energy from one alternating current circuit to another or to several other circuits. They are used for a wide range of purposes, including raising the voltage from electric generators to enable long distance transmission of electricity and lowering the voltage of conventional power circuits to operate low voltage devices.
“Transformers for Renewable Energy Applications”, a research paper written by K.R.M. Nair and published in 2019, highlights several features of smart transformers. First, voltage sag compensation as the present distribution transformers cannot correct the voltage levels and ensure constant voltage of the customer terminal. Second, harmonic isolation or filtering as the non-linear loads produce harmonics and the transformer will be capable of maintaining clean output waveform. Third, in addition to the stable AC output, the future transformers will have to give DC output for EV charging and other DC loads. Fourth, outage compensation as the transformer will draw power from the energy system and give outage compensation. Fifth, fault isolation because the transformer will isolate the grid from a fault on the load side and also isolate itself from the grid when a fault on the incoming side occurs. Apart from these, features such as reactive power compensation, advanced distribution automation, voltage balancing, protection from single phasing, reduced weight and size are all essential features of a smart transformer.
High voltage direct current (HVDC) converter transformers, phase shifting transformers (PSTs), coupling transformers and smart transformers are some of the leading emerging technologies in the transformer industry. When compared to a high voltage alternating current system, HVDC converters can transmit large amounts of electricity over long distances with lower losses. PSTs can regulate the phase of line voltage to control the active power flow in the network and work independently of energy generation. These transformers are used in networks where there is a lot of power wheeling. Coupling transformers are used in flexible AC transmission systems to improve control and stability. Digital transformers are critical components of digital substations with intelligent monitoring and diagnostics. These can automatically adjust voltage based on smart grid and real-time power supply data. Remote monitoring is possible for components such as transformer core, windings, oil, tap changers and bushings.
In India, several government programmes have been developed to strengthen and modernise the transmission and distribution network. These include the Integrated Power Development Scheme and the Deendayal Upadhyaya Gram Jyoti Yojana (DDUGJY). These programmes are focused on building new substations and enhancing the existing ones. As of January 2023, 2,851 substations and 4,498 aug-substations have been installed in the country according to the DDUGJY portal.
The Revamped Distribution Sector Scheme aims to focus on distribution infrastructure projects. Additionally, transmission utilities are making significant efforts to increase substation capacity, thus strengthening the network and allowing for greater integration of renewable energy.
India commits to installing 500 GW of non-fossil fuel capacity by 2030. Thus, it is important to have advanced and flexible systems to integrate such a large volume of intermittent generation into the grid and to control the sudden imbalances in the production of renewable energy. Therefore, effective digital power systems can aid in grid monitoring and maintenance, and help meet India’s energy needs.
Future developments in these fields will also be crucial in the development of autonomous energy systems (AESs). AESs can automate large-scale grid control by responding to real-time data with algorithms and machine learning technology. The system will react to external data sets, such as weather reporting for prediction of renewable generation, accurately balance load and generation in real time, and improve grid recovery time by identifying and resolving issues as they arise. Such efficient and robust systems can help in reducing energy losses. Systems should be built to last for a long time with lower maintenance costs and fewer instances of breakdown.
Going forward, to ensure the continued implementation of digital technology in the renewable energy transmission space, norms and standards should be developed with the collaboration of consumers, government, transmission and distribution utilities, and manufacturers. They also need to establish the necessary incentives and take into account the costs and difficulties associated with operations and finance that may prevent its uptake.
By Nikita Choubey