Electric power systems were traditionally designed for unidirectional flow of power. Also, as conventional fuels dominated the energy mix, there were fewer power supply variations. Therefore, critical equipment such as transformers and substations were designed in a simple manner. However, with the changing energy mix due to greater integration of renewables and varying loads due to the installation of sopisticated digital equipment on consumer premises, the features of electric power equipment have evolved. Electric power equipment now needs to provide for bidirectional energy flows, information exchange, and energy storage for grid stability. Also, digital loads require quality power at constant frequency and voltage along with predictive forecasting.
In addition, new power market designs, regulations, and environmental and energy efficiency norms have been introduced. Further, new grid protection solutions need to be developed in order to balance infirm renewable generation. These requirements are leading to the deployment of intelligent substations and smart transformers with capabilities such as real-time monitoring and control, and load and supply management. Further, the internet of things (IoT) and solid-state transformers are emerging as game changers in the technology landscape of the power sector.
The digitisation of substations is the next big thing for power systems. Digital substations comprise intelligent electronic devices (IEDs) with integrated information and communication technology, non-conventional instrument transformers, merging units and phasor measurement units that are interfaced with process bus and station bus architectures. The communication framework of a digital substation is based on fibre optic cables rather than the copper cables used in traditional substations.
Digitisation will reduce the space requirement at the relay house by up to 60 per cent, the outage time by up to 50 per cent, the carbon footprint by up to 50 per cent, the installation time by up to 40 per cent and copper cable requirement by up to 80 per cent vis-à-vis an air-insulated switchgear substation. The key characteristics of a digital substation include substation automation protection and control system with IEC 61850 station bus, condition-based maintenance, more safety and a robust communication system.
The development of digital substations requires sophisticated communication technologies such as Ethernet and multicast networking to ensure a seamless network performance. Ethernet network switches are capable of providing gigabit speeds, which have not been widely deployed in substation networks so far, as the existing protection and control equipment does not require high levels of bandwidth to perform its functions. It is only recently that Ethernet technology is being deployed for substation communication. With its deployment, the need for increased bandwidth is expected to rise across the network.
Multicast networking is another communication technology that allows a Layer 2 message from a single source to be propagated to multiple receivers on the network. Multicast is implemented across the network through managed network switches that receive the message on one port and transmit it to recipient ports. Multicast messaging needs to be managed by available technologies such as virtual local area networks for providing increased bandwidth. While IEC 61850 utilises Layer 2 multicasts for different protocols, IEEE 1588 utilises time synchronisation and sampled measured values on the process bus.
Transformers serve as a centre for the collection and distribution of electricity. They are crucial for the successful transition to a smart grid, and will directly benefit from reliability and efficiency improvements with the deployment of new online monitoring technologies. Currently, the majority of transformers are not ready for the smart grid because they were installed years before the advent of interactive information transfer. The next generation of transformer technology, including smart transformers, allows remote monitoring of a wide range of grid parameters as well as transformer parameters.
Smart transformers are an integral part of digital substations and help in regulating the voltage while maintaining contact with the smart grid. These transformers allow remote administration and real-time feedback on power supply parameters. These transformers are equipped with IEDs, and intelligent monitoring and diagnostics programmes. Besides, they provide web and supervisory control and data acquisition-friendly interfaces. A smart transformer provides the exact amount of power that is required and immediately responds to fluctuations within the power grid, acting as a voltage regulator to ensure that the optimised voltage is undisturbed. Moreover, smart transformers consume less energy, thereby reducing greenhouse gas emissions.
Smart transformers have a variety of applications. They can be deployed at the point of common coupling of a microgrid to control the active power exchange between the microgrid and the utility grid. They can be used for faster and superior regulation of the voltage, frequency and harmonic behaviour of each feeder.
During power supply fluctuations, smart transformers can be monitored and controlled in real time to ensure that the voltage level is optimised even when the system is heavily loaded. These transformers enhance the power quality by aggregating unbalanced loads in a phase. These features make smart transformers ideal for renewable energy integration.
IoT is being called a revolutionary technology, which would play a key role in transforming the technology landscape across many sectors. IoT is essentially an emerging paradigm of internet-connected things that allows physical objects or things to connect, interact and communicate with one another. IoT has a wide range of applications in the power sector, homes and industries. In energy systems, it can play a major role in the smart grid space. IoT extends the benefits of a smart grid beyond automation, distribution and monitoring. It also covers Ethernet-based communication substations for effective coordination and better power transmission and distribution, especially during peak hours. For instance, the country’s largest power transmission utility, Power Grid Corporation of India manages most of its assets remotely through IoT. From its National Transmission Asset Management Centre located in Manesar, it can now track substations, transformers and transmission towers as well.
Meanwhile, solid-state transformers are under development. These transformers can receive both alternating current (AC) and direct current (DC) inputs as well as generate AC and DC outputs, and therefore they are suitable for bidirectional power flows. Although the first patent for solid-state transformers was filed in the 1980s, the technology could not be commercialised owing to the non-availability of suitable materials. With recent innovations in material sciences, solid-state transformer technology is likely to achieve commercial success in the future. These transformers come with other benefits such as power quality improvement, and small size and light weight vis-à-vis a comparable distribution transformer. Solid-state transformers of ratings 11-15 kV are expected to be commercialised in the next five to seven years.
On the whole, power system technologies are developing at a fast pace and new applications may require innovative protocols and physical interfaces, which may not be updated simply by software or firmware upgrades. Therefore, utilities must adopt a hardware design that allows interchangeable modules in order to future-proof the network and reduce capex requirements in the coming years.