The entire architecture of the electricity sector is currently being restructured by the shift in generation to variable renewable energy (VRE) from the existing paradigm of thermal energy-based generation. As a result of this transition, several components of the grid would need to be upgraded in order to enable and effectively manage load variations in real time.
Digital technologies are therefore being embedded in various areas of the grid to enable real-time optimisation of electricity flow in an efficient manner. Additionally, digital systems are equipped with data analytics software, which facilitates predictive maintenance and quick identification of issues in the system. In light of these benefits, the significance of digitalising transformers cannot be overstated, given their function in directing, varying and determining the flow and supply of electricity.
Operational principle of digital transformers
A digital transformer is constituted of three elements – hardware, software and services – which function seamlessly in order to manage the flow efficiently, reliably and safely. The hardware consists of digital sensors, dissolved gas analysers and digital safety devices to continuously gather real-time data for monitoring, diagnostics and control at the local level. The same data can also be preventive and predictive maintenance at the station control level, via the cloud. The transformer will constantly supply data in real time to a control room and if there are any red flags or anomalies in any component of the digital transformer, it will immediately identify them and alert the control room. Subsequently, the control room will trigger an immediate inspection of the specific parts, in accordance with a predetermined plan. Such a rapid response will help in resolving issues even before they affect grid operations. Digital transformers also include auxiliary digital technologies such as submersible transformer inspection robots and dry-type transformers. Submersible transformer robots can be used for monitoring and supervising liquid/ oil-filled transformers, with minimal risk to remotely situated personnel. Additionally, they are endowed with the capacity to perform a meticulous observation of the system and record it, ensuring that the inconspicuous/inaccessible components receive the same attention as visible components.
Dry-type transformers are also often equipped with digital technologies such as smart sensors and other auxiliary mechanisms, which are able to accumulate data and redirect air to the core more efficiently. While conventional transformers require regular application of oil to cool the core and the coil, dry-type transformers utilise solid insulation material to harness external air to cool their core and coil. Such transformers are ideally suited for high-risk applications such as in offshore and densely populated areas and also in sensitive ecosystems.
Advantages of digital transformers
One of the biggest advantages of a digital transformer is that it provides the precise amount of power required and immediately responds to fluctuations in the power grid, thereby acting as a voltage regulator. In contrast, conventional transformers require constant manual supervision to respond to fluctuations in the grid and are also slower at responding, compared to digital transformers, which are capable of responding immediately, making adjustments by taking into account real-time data and optimising the power flow. This helps utilities to reduce expenses, maximise efficiency and minimise any power losses that occur by way of excessive heat or other technical issues. It also helps utilities in isolating the specific problem areas before they debilitate the entire grid and cause outages, in addition to requiring a huge outlay on component repair and replacement.
Further, digital transformers are able to extrapolate the wear and tear caused by load changes and estimate the next outage, or next time a component would be inoperative, with their data analytical and modelling capabilities. This will help transmission and distribution companies to schedule maintenance periodically for specific parts, instead of scheduling system-wide maintenance, where the grid is often forced to go offline for a couple of hours.
Also, traditional cooling controls of power transformers are moving towards digitalisation as the former have many limitations. One such limitation is that the cooling is grouped into banks, where the only possible operational states are no-cooling, half-cooling or full-cooling. For large power transformers, one such bank may consist of many pumps and fans. The use of digital systems removes this limitation by allowing independent control of the cooler banks and thus providing a more fine-grained regulation of cooling capacity.
Apart from the various aforementioned technical functionalities incorporated in the transformers, new digital transformers also allay customers’ cybersecurity concerns. This is being done by adding additional layers of security such as radio frequency identification access card-enabled Wi-Fi. Moreover, the data stored is encrypted and the user needs a decryption key to be able to read it.
These features make digital transformers ideal for power systems with increasing renewable energy integration. According to the Central Electricity Authority’s report, as of June 2021, India has an installed renewable energy capacity of 96.7 GW, of which solar and wind power account for a share of 84.6 per cent. Therefore, a substantial portion of the installed capacity in India is of VRE category, which tends to have volatile electricity generation. The capacity is only set to grow at a compound annual growth rate of 8-10 per cent over the next decade, to reach a share of 30-40 per cent of India’s installed capacity. In other words, by 2030, 170-180 GW of the country’s capacity can be expected to be of the VRE category.
Meanwhile, at the distribution transformer level, digital distribution transformers provide intelligence to maximise reliability, optimise operations and maintenance costs, and manage asset more efficiently. Technology providers are working towards integrating sensing technology directly into the transformer during the manufacturing process, which will help in enhancing accuracy and will also ensure that the digital components are cohesively integrated into the rest of the transformer.
Simultaneously, a substantial portion of the growth in variable renewable energy capacity will be driven by the installation of rooftop solar in commercial settings or in households. These entities, in turn, will sell the excess electricity generated in the morning and afternoon to discoms, while purchasing electricity in the evening and off-peak hours from discoms. Hence, in the future, there will be a two-way flow of electricity and to optimise this two-way, intermittent and volatile flow would necessitate that transformers at the distribution level have real-time load balancing and network controls. Digital transformers are endowed with the aforementioned capabilities, unlike conventional transformers, which cannot facilitate a two-way flow of volatile and fluctuating loads of electricity.
Digital transformers have a longer lifetime and entail lower expenses on repair and maintenance. They also help in enhancing the safety of the system and reduce outages caused by unanticipated component failures because they utilise data analytical mechanisms to predict equipment failure in advance. Real-time data availability also helps asset managers make better short-term and long-term decisions regarding their upkeep and capacity expansion.
Further, installing digital transformers is inevitable considering the forecasted growth in variable renewable energy capacity. These energy systems have a volatile load curve that will thermally and mechanically subject transformers and the grid to significant stress, which conventional transformers will be unable to optimally manage.
Therefore, consumers, government, distribution utilities, transmission utilities and manufacturing companies should collaborate to devise a mutually beneficial set of institutional norms and standards to ensure a steady and phased execution of digital transformers. It is also necessary that manufacturing companies embed digital technologies in the upcoming generations of digital transformers so that hardware, software and the main equipment operate seamlessly.