Substation automation involves the integration of operations-related activities like system protection, control and data acquisition into a unified control system. The objective of automating substations is to reduce overall costs and eliminate redundant equipment and database by minimising human intervention. A unified control system in an automated substation includes control of substation systems from one screen; comprehensive protection management; compact system designs; decentralised system structure; no conventional mimic board; numerical protection and control, self interlocking and supervision; modern man-machine interface; operator guidance and maintenance support.
There are many benefits associated with an automated substation. These include less use of hardware and panels, reduced maintenance costs, minimum outages, integration of third-party equipment, lower cabling and installation costs, reduced testing and commission costs, less space and civil works requirement, easy customisation and use, operational efficiency with minimum errors, lower risks, and better power quality.
Functions of automated substations
The prerequisites for selecting an automation system while designing a new substation include a reliable system that is compatible with the vendor’s hardware; it should incorporate distributed infrastructure to minimise wiring requirements, it should be flexible and easy to set up, and the substation unit must have a computer to store data and pre-process information.
Automated substations are required to perform some basic functions such as control of bay-level devices and personal computers from a remote control station. They should be able to perform software interlocking, synchronisation checks for circuit breaker operations, on-load tap changer operations, runtime supervision, double command lock out, as well as communication with local and remote control stations. Some of the enhanced control function requirements pertain to sequential switching, automatic changeover of bus bars, parallel operation of transformers, auxiliary services, and control and monitoring. Automated substations are also required to provide global positioning system time synchronisation and International Electrotechnical Commission (IEC) 61850-protocol support.
The analysis and diagnostic functional requirements of automated substations include relay parameterisation, fault location and records, asset management, failure analysis, sequence of event analysis, automatically generated fault reports, disturbance evaluation, alarm statistics and station-wide data storage.
IEC 61850 communication standard
Ethernet-based IEC 61850 is the first real global communication standard for substation automation systems. It is a part of the IEC Technical Committee 57 (TC57) reference architecture for electric power systems. All the upcoming substations of Power Grid Corporation of India Limited, are planned to be equipped with substation automation systems based on IEC 61850.
The IEC 61850 standard specifies expandable data models and services. It also provides the substation configuration description language, and supports comprehensive and consistent system engineering. For communication, the IEC 61850 uses Ethernet, transmission control protocol and internet protocol. The standard is also open for future communication concepts.
The main objective of the IEC 61850 standard is to ensure interoperability, free configuration and long-term stability in the system. Interoperability refers to the ability of intelligent electronic devices (IEDs) from different vendors to exchange and use information over a common communications media. Meanwhile, free configuration implies that the standard will support different philosophies and thus allow a free allocation of functions. Long-term stability emphasises that the standard will be future proof, which means that it must be able to keep pace with the progress in communications technology as well as evolving system requirements.
The most important objective of the standard is to reduce overall costs by ensuring interoperability and open IED description, allowing communication closer to power apparatus, and reducing conventional wiring by using LAN.
In sum, modern substation automation technology and the new IEC 61850 standard significantly reduce the amount of manual effort needed in substation operations. According to industry experts, with the introduction of new technology, communication redundancy for substation automation is possible at a reasonable cost. However, there is still scope for investment in research and development to bring down costs and promote extensive deployment of automation technologies.