The Indian power system faces the challenging task of balancing demand and generation while maintaining grid stability. With a peak demand of around 250 GW and a significant renewable energy capacity of 203 GW, India’s grid requires precise management to keep frequency deviations within regulatory limits. High frequency operation, largely caused by a mismatch between demand and generation are exacerbated by weather conditions. Further, renewable energy variability poses a unique set of operational challenges. GRID-India’s recent report on “High Frequency Operation in Indian Power System” delves into event analysis of the happenings of August 4, August 11 and August 25, 2024. It further provides an analysis of intra-state and interstate grid management, evaluates thermal and renewable generation responses and outlines key recommendations to enhance flexibility, manage down reserves and improve forecasting for better grid stability.
This story provides an overview of the key findings of the report, shedding light on crucial aspects of grid management; and summarises key recommendations for achieving enhanced flexibility and managing reserves to improve
grid stability.
Analysis of high frequency operations
Event analysis of August 4, 2024
On August 4, 2024, the frequency of India’s power grid consistently exceeded the upper threshold of the Indian Electricity Grid Code (IEGC) band, set at 50.05 Hz, for a substantial portion of the day. From around 11:00 hrs to approximately 15:30 hrs, frequency levels remained elevated, with a peak of 50.39 Hz recorded at 12:02:30 hrs.
The day’s average frequency was calculated at 50.032 Hz, showing only a slight deviation from the nominal value of 50 Hz. This minor deviation is reflected in the frequency variation index (FVI), which was recorded at 0.1378, highlighting notable frequency fluctuations. The frequency’s standard deviation, measured at 0.1132, further indicates the variability observed. Overall, the grid operated above the 50.05 Hz threshold for about 26.27 per cent of the day, underscoring periods of sustained high frequency in grid performance.
Event analysis of August 11, 2024
On August 11, 2024, the all-India power system experienced frequent fluctuations in frequency, often remaining above the IEGC limit of 50.05 Hz for most of the day. This high frequency persisted mainly between 09:30 and 15:00 hrs, peaking at 50.329 Hz at 13:44:50 hrs. The average frequency for the day was 50.043 Hz, slightly above the target of 50 Hz, indicating minor deviations. The FVI was recorded at 0.0892, reflecting some inconsistency, while the standard deviation was 0.0844, showing variability.
The conventional generation on this day also revealed notable fluctuations across different sources.
Thermal generation: The maximum output reached 139 GW, with a minimum of 96 GW and an average of 118 GW. Thermal generation showed 70 per cent flexibility in adjusting to demand changes.
Hydro generation: Hydropower was actively used for demand balancing, peaking at 35 GW, with a minimum of 23 GW and an average of 28 GW, achieving a load factor of 0.64.
Gas generation: Gas plants ramped up quickly during peak hours, with a maximum generation of 3.1 GW, a minimum of 2.1 GW and an average of 2.5 GW, maintaining a load factor of 0.11.
Additionally, the report highlighted that on the same day, curtailments affected intra-state wind and solar generation in Rajasthan and Gujarat. In Rajasthan, wind generation was curtailed by 6.4 MUs, peaking at 878 MW, while Gujarat saw a reduction of 2.16 MUs, with a peak curtailment of 90 MW. Solar generation was also curtailed in Rajasthan by 10 MUs, reaching a maximum of 1,356 MW, and in Gujarat by 0.72 MUs, peaking at 30 MW.
Event analysis of August 25, 2024
The report stated that on August 25, 2024, the all-India power system experienced extended periods of frequency levels above the IEGC limit of 50.05 Hz, particularly from 08:30 to 16:00 hrs, with only a few brief drops. The highest frequency recorded was 50.377 Hz at 13:07:50 hrs, while the daily average frequency was 50.065 Hz, slightly above the target of 50 Hz. In the analysis of conventional generation for that day, the report made the following observations.
Thermal generation: During solar hours, the thermal output decreased to match lower demand, with a minimum of 96 GW and a peak of 139 GW. Thermal generation exhibited about 69 per cent flexibility, averaging 118 GW with a load factor of 0.60. In the evening, thermal generation ramped up significantly to compensate for the decline in solar output and the increase in demand.
Hydro generation: Hydro output reached a low of 23,695 MW but increased during non-solar hours, peaking at 35,306 MW to meet higher demand. The average hydro output for the day was 28,666 MW, with a load factor of 0.64, demonstrating hydro’s ability to quickly adjust to demand changes.
Gas generation: Gas plants notably ramped up during evening peak demand, recording a minimum of 2,191 MW and a peak of 3,176 MW. The average gas generation was 2,526 MW with a load factor of 0.11, providing crucial back up as other sources declined.
The report also provided insights into the interstate and intra-state thermal generation on August 25, 2024 and the reasons for non-flexible operation among intra-state thermal plants. It was observed that these plants often do not operate flexibly, even though they could reduce generation during periods of high grid frequency. Several factors limit their flexibility; in some states, technical minimum limits for thermal generation are not defined in the state grid code and in practice, these limits are often set between 65 and 75 per cent of their MCR. This high limit makes it challenging to schedule them at a lower level of about 55 per cent of MCR. Additionally, in states such as Punjab, transmission constraints hinder effective generation reduction.
Key recommendations
The report notes that the Indian power system encountered high frequency operational challenges on August 4, August 11 and August 25, 2024, largely driven by a suppressed demand due to heavy rainfall and weekends, as well as over-injection from variable renewable energy sources. Limited flexibility in hydropower stations due to high inflows and reservoir levels, inadequate intra-state thermal generating flexibility and insufficient down reserves at the interstate level further complicated grid stability.
The report suggests that to address these issues, it is essential to enhance the flexibility of both intra-state and interstate thermal units by allowing operation at a minimum power level of 40 per cent to increase down reserves in the grid. Regulatory bodies should incentivise flexible operation by providing compensation mechanisms to encourage part-load operation of thermal plants. Additionally, implementing two-shifting operations for thermal units with high energy charge rates–allowing them to be offline during solar hours and active during non-solar hours–will further optimise operations. Expanding long-duration energy storage systems such as pumped storage is crucial to enhance operational flexibility. Finally, improving forecasting capabilities for both demand and renewable energy generation at the state, regional and national levels will facilitate better management of resources.
These measures will strengthen India’s grid stability, create a more adaptable power system and accommodate the growing share of renewable energy sources. By implementing these recommendations, the grid can effectively respond to variable energy inputs and the changing energy landscape, ensuring reliable and resilient operations for the future.