As electrical grids become more complex with the integration of intermittent renewable energy, grid operators need solutions that are reliable, safe and enable quick decisions in case of an emergency. A digital substation offers precisely these benefits and much more. Based on the process bus architecture, digital substations remove the last electrical connection between high voltage equipment, and protection and control panels, thereby ensuring greater safety, reduced capital and operations and maintenance costs, as well as faster communication of vital operational parameters of a substation.
A key feature 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, which allows the deployment of optical fibre network (Ethernet based) in place of copper wiring between intelligent electronic devices (IEDs) and various other equipment. As a result, the substation’s status and performance parameters can be shared in real time through digital signals without complicated wiring. The transformers and switchgear continuously transmit data over the process bus and any upstream devices for protection, measurement, metering and monitoring.
The benefits of digital substations are plenty, including better productivity and functionality, greater reliability of assets, safety of substation operators, lower cost and less space requirement. A digital substation uses fibre optic cabling instead of copper wiring, which results in a reduction in capital cost through direct savings on the cost of copper wires as well as associated civil works. Tonnes of traditional copper wires between high voltage equipment and the control room can be replaced with a few fibre optic digital communication buses (process bus), which results in a reduction in the installation cost and time.
According to industry estimates, digitalising can reduce the quantity of copper in air-insulated switchgear substations by up to 80 per cent through the use of fibre optics. In addition, it helps 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 and installation time by up to 40 per cent. This represents significant cost savings for utilities.
Further, digital communications via fibre optic cables are faster, which helps in real-time monitoring and control of substation parameters. This improves flexibility, availability and reliability of power transmission. Grid operators can, therefore, detect anomalies and plan maintenance in advance to prevent substation breakdowns. In contrast, conventional substations rely on traditional diagnostic methods, wherein corrective action is taken after a failure. In addition, digital substations have enhanced features to ensure cybersecurity as its system data management software continuously looks for possible cyberthreats. Digital substations are also equipped with a number of sensors that help mitigate transient stresses. Besides, digital substations are equipped with current and voltage sensors, which do not require regular maintenance or calibration. In contrast, traditional substations require large and bulky testing equipment that needs to be properly calibrated. Digitalised communications within a substation can increase control, facilitate the integration of intermittent renewables and improve safety.
The first digital substation was installed by Australian electricity transmission company Powerlink Queensland in 2009. Since then, several utilities across the world have installed digital substations. In India, the first digital substation (110 kV) was commissioned in 2018 at Technopark, one of the largest IT parks in the country, by Kerala State IT Infrastructure Limited. The country’s leading power transmission utility, Power Grid Corporation of India Limited (Powergrid) is also taking steps to introduce process bus architecture in substations, paving the way for digital substations. It is implementing process bus in new substations and renovating old substations based on experience gained from certain pilot projects. Currently, Powergid is implementing process bus for retrofitting the oldprotection systems at the Malerkotla substation and at the 220 kV greenfield gas-insulated switchgear substation in Chandigarh. At the state level, Gujarat Energy Transmission Corporation Limited and Maharashtra State Electricity Transmission Company Limited are also implementing digital substations in their projects to improve power reliability and evacuate renewable energy.
The way forward
Given the growing focus on smart grids and smart cities, the adoption of digital substations is expected to grow in the country. The benefits of faster installation, and lower cost and space requirements are expected to find favour with transmission and distribution utilities, especially in light of right-of-way constraints. That said, the deployment of digital substations should be accompanied by solutions to manage data and turn it into actionable insights to derive maximum benefits.