A total of five grid islanding schemes are currently under development while two others have been proposed, according to information provided by Central Electricity Authority (CEA).
A report by CEA on Grid Islanding suggests that till late 2020, a total of five grid islanding schemes—one each in the Northern and Southern region, and three in the eastern region—were under implementation as of late 2020. Besides, one scheme in the Northern region and one in the Western region, are in proposal stage. The Northeastern Region has no islanding scheme—either operational or proposed.
Currently, India has a total of 28 grid islanding schemes, which includes 21 under operation and the aforementioned seven that are either under implementation or proposed.
The concept of grid islanding assumed national importance after the major grid disturbance of July 2012. Out of the 21 islanding schemes currently under operation, as many as 13 were commissioned after the major grid failure of July 2012.
The CEA report explained that Grid Islanding or simply “Islanding” is a defence mechanism as a final stage in which a part of the system is islanded (or isolated) from a disturbed grid so that if healthy, this subpart could survive in isolation from the rest of the grid. The basic objective of an islanding scheme is to avoid a total blackout, and quicker restoration of a failed grid.
The CEA report also observed that islanding should take place only when all other defence plans have been allowed their full opportunity to bring back and maintain system integrity.
The report also cautioned that having a very large number of islanding schemes may not be in the interest of secure and integrated operations of the grid. “Opening of a large number of elements simultaneously may trigger mal-operation and the islanding scheme itself could become a cause of grid disturbance,” the report said.
Bangalore and Hyderabad
In a meeting on grid islanding in December 2020, the Union power minister, R.K. Singh, had raised a query regarding islanding schemes for Hyderabad and Bangalore. In reply, the CEA explained that while Hyderabad city was covered under the Ramagundan Islanding Scheme, there was little scope for developing islanding for Bangalore as there was no power generation plant in the vicinity of the city. Subsequently, the Southern Region Power Committee (SRPC) was advised to design an islanding scheme for Bangalore and ensure its quick implementation.
Grid resilience
POSOCO Ltd, which also participated in the meeting, explained that the focus has now shifted from grid islanding to grid resilience. A resilient grid recognizes that systems can fail locally but can be quickly revived through black-start resources (bottom-top approach) or by extending supply from healthy parts of the system (top-bottom approach).
Major cities
The power minister urged that islanding schemes should be designed for all major cities. If there is need to establish a power plant in or around a city (as is the case with Bangalore, as discussed above), the proposal of the same must be submitted to the power ministry for consideration.
Schemes under implementation
The five grid islanding schemes currently under implementation include Unchahar Islanding Scheme. This scheme is in the Northern Region and will cater to a total load of 760 mw covering 50 per cent of Lucknow, Raibareily and Fatehpur, all in Uttar Pradesh. In the Southern Region, the Simhadri Islanding Scheme is advanced stage of completion. The remaining five schemes—all in the Eastern Region—include Chadrapura, MTPS and IB TPS. All these schemes are expected to be commissioned by December 2021.
The two islanding schemes proposed pertain to the Kashmir Valley Region, and the UT of Dadra Nagari Haveli and Daman & Diu (DNHDD).
Major Grid Outages
Two major grid failures in recent history include that on July 30 and 31, 2012 that mainly affected the Northern Grid and that on October 12, 2020, affecting the Western Grid.
Note: This story is based on a meeting held on December 28, 2020, to discuss islanding schemes in the country. The minutes of this meeting were filed by the power ministry on February 8, 2021. This meeting was to come up for review at the 10th meeting of the National Committee on Transmission (NCT) that was supposed to be held on April 9, 2021. The minutes of this NCT meeting have not yet been promulgated by the power ministry.
