The power sector in India is constantly evolving and embracing new transformer technologies to enhance grid efficiency, bolster energy security and facilitate the integration of renewable energy sources. Meanwhile, transformer technologies have undergone significant advancements to meet the changing requirements of power utilities and adapt to the dynamic nature of the grid. The evolution of transformer designs and features has been driven by various factors, including the need for space optimisation, cost reduction, increased asset lifespan, improved core materials, enhanced safety measures, integration of digital hubs, lower failure rates and reduced noise levels.
High voltage direct current (HVDC) transformers, phase-shifting transformers, coupling transformers, ester-oil-filled transformers, dry-type transformers, green transformers and smart transformers are among the cutting-edge technologies reshaping the power sector. As utilities prioritise grid modernisation, investing in these new and advanced transformer technologies can prove to be a viable solution to ensure a safe, reliable and cost-effective grid. By adopting these innovative technologies, they can effectively address the growing demand for a more efficient and sustainable energy infrastructure in the country.
New and emerging transformer technologies
HVDC transformers: HVDC transformers hold immense significance in the transmission of electricity over long distances. Their primary application is in HVDC converter stations, where they convert alternating current (AC) to direct current (DC), ensuring highly efficient transmission, with minimal losses. The value of HVDC technology becomes particularly evident when transmitting power from distant renewable energy sources to load centres, facilitating seamless integration of renewable energy into the grid.
Phase-shifting transformers: Phase-shifting transformers serve a crucial purpose in the control of power flow on transmission lines. This can be achieved by allowing for the adjustment of the phase angle between input and output voltages. Through this dynamic control of power flow, these transformers play a key role in optimising the grid stability and alleviating congestion, particularly in interconnected power systems.
Coupling transformers: Coupling transformers play a vital role in flexible AC transmission systems (FACTS), enhancing the control, stability and power transfer capabilities of the transmission system. These transformers facilitate the connection between the grid and the static synchronous compensator (STATCOM), a FACTS device responsible for supplying dynamic, precise and adjustable amounts of reactive power to the connected AC power system. As STATCOM cannot be directly connected to high voltage grids such as 220 kV and 400 kV, a coupling transformer serves as the intermediary device, enabling bidirectional power flow between the STATCOM system and the HV grid. Unlike conventional transformers, the coupling transformer’s voltage control is handled by the STATCOM system, eliminating the need for a tap changer.
In STATCOM applications, the coupling transformer’s step-up duty is of utmost importance, requiring specific design considerations to meet these requirements. Properly positioned STATCOM devices in the system enhance loadability and stability and reduce network losses through the optimisation process. Overall, coupling transformers in FACTS systems improve the efficiency and stability of the power transmission network.
Ester-oil-filled transformers: While traditional transformers rely on mineral oils as their insulating fluid, ester-filled transformers utilise natural esters for liquid insulation. The use of natural esters offers significant advantage over the use of mineral oils due to their higher fire-resistance properties. With a fire point of around 360 ºC, which is about twice that of mineral oil and a flashpoint of 320 ºC, ester-filled transformers are much less susceptible to fire hazards. Furthermore, in the event of a leak, ester-filled transformers outperform their conventional counterparts because natural esters are biodegradable. This property minimises the risk of soil contamination, making them more environmentally friendly and reducing potential ecological impacts in case of accidents.
Dry-type transformers: A dry-type transformer operates without the use of any liquid as an insulating or cooling medium for its windings and core. Instead, it relies on air or gas as the medium and uses epoxy resin or polyester resin for insulation. The two main types of dry-type transformers are cast resin transformers and vacuum pressure impregnated transformers. Dry-type transformers offer numerous advantages, making them highly useful in various applications. They are associated with enhanced safety and reliability, as well as environmental compatibility. Their installation is easy and maintenance requirements are minimal. These transformers exhibit excellent overload capacity, provide cost reductions, deliver exceptional performance, pose no fire hazards and offer remarkable resistance. They have a long lifespan and are suitable for use in damp and contaminated areas. However, dry-type transformers do have some drawbacks compared to oil-filled transformers, they generally come with a higher cost. They tend to be larger and heavier, making handling and transportation more challenging. Dry-type transformers can be more sensitive to certain conditions and may produce higher noise levels than their oil-filled counterparts. Despite such limitations, their overall benefits often outweigh drawbacks, making them a preferred choice in various applications.
Green transformers: Emerging green transformers, designed for ultra-low-noise applications, incorporate ester oil to enhance fire safety. These environmentally friendly transformers present many advantages over their traditional counterparts. Notably, they contribute to a lower carbon footprint and exhibit slower ageing, promoting longer-lasting performance. One of the key benefits of green transformers is their lower life-cycle costs. Through the implementation of hermetically sealed tanks, they eliminate the need for an oil conservator and associated devices. This feature significantly reduces maintenance requirements, resulting in cost savings over the transformer’s lifetime.
Smart transformers: Smart transformers are designed to be adaptable, allowing them to efficiently manage the fluctuating demands of the power grid. Their ability to monitor and control voltage, current and power factor makes them well suited to handle uncertainties posed by intermittent renewable energy sources such as solar and wind power. Unlike traditional transformers that struggle with the variability of renewables, smart transformers step up to bridge the gap, ensuring a smooth and seamless flow of clean energy. Beyond their application in the main grid, smart transformers extend their potential to microgrids and distributed energy resources. They skilfully manage the electricity flow between the main grid and the localised power systems, resulting in a more resilient and flexible energy supply, which in turn bolsters the overall grid stability. Among the key strengths of smart transformers are their versatility and communication capabilities. They support the integration of renewable energy sources and electric vehicles, playing a pivotal role in the modern energy landscape. As this technology matures and becomes more accessible, smart transformers hold the promise of significantly impacting the energy sector. They have the potential to propel towards an efficient, reliable and sustainable future, where the dynamic demands of a modern grid are effectively managed, paving the way for a cleaner and more resilient energy infrastructure.
Other transformers: Some of the other power transformer technologies used in India include distribution transformers, autotransformers, amorphous core transformers and mobile transformers, among others. Distribution transformers are widely used in India’s power distribution networks to step down high voltage electricity from the transmission system to lower voltages suitable for consumer use. These transformers ensure safe and reliable electricity supply to homes, businesses and industries. Autotransformers are employed in situations where a small voltage adjustment is needed, as they have a single winding with taps along the coil to vary the voltage ratio. They are commonly used in applications such as voltage regulation, where the load fluctuates as in railway electrification. Moreover, amorphous core transformers are designed to reduce energy losses and improve energy efficiency. They use amorphous metal alloys for the core, which have lower hysteresis and eddy current losses compared to traditional silicon steel cores. These transformers contribute to energy conservation and reduced carbon emissions. Further, mobile transformers are designed for rapid deployment in emergency situations such as natural disasters or during grid maintenance. These portable units provide a temporary power supply to critical facilities and help restore power quickly in affected areas.
The way forward
In the coming years, we are likely to witness a surge in the adoption of smart transformers by distribution and transmission utilities and they are going to become vital components of the modern electricity grid. These transformers operate independently to monitor voltage and maintain seamless communication with the smart grid. This capability enables remote management and real-time adjustments of power supply parameters, facilitating efficient and responsive power distribution.
In conclusion, transformer technologies are continually advancing to meet the evolving needs of power systems and tackle the challenges that utilities encounter. By adopting appropriate technology, utilities can enhance power reliability, reduce faults and optimise asset management for more efficient and reliable electrical infrastructure.