Overdrawing can shut down power grid, lead to blackout: Grid-India cautions Southern states

CHENNAI: The Grid Controller of India Limited (GRID-India), under the Ministry of Power, has issued a critical alert to the southern states, including Tamil Nadu, over a severe drop in the all-India grid frequency, citing heightened risks of grid instability and potential blackouts.

In a letter dated April 24, addressed to the Principal Secretary (Energy) of the GoTN, GRID-India highlighted that the frequency dropped to 49.42 Hz on April 21, and stayed below the IEGC (Indian Electricity Grid Code) safe band (49.90 – 50.05 Hz) for nearly six hours.

Alarmingly, this prolonged dip crossed the threshold for Automatic Under Frequency Load Shedding (AUFLS) activation, a defence mechanism designed to prevent system-wide failures. “Any large generation tripping during such vulnerable periods poses a substantial risk of cascading failures and widespread grid disturbances,” the letter stated.

A frequency drop below 49.90 Hz indicates that the power demand has exceeded generation, which can lead to various problems, including voltage fluctuations, equipment damage, and even complete system failures. The situation has been attributed to overdrawing of power during non-solar hours by southern states, with TN recording a peak overdraw of 602 MW between 6-7 pm on the same day. Other hourly overdraws varied between 295 MW and 391 MW in the evening and late-night hours.

GRID-India also wrote identical letters to the energy department secretaries of Andhra Pradesh, Karnataka, Kerala and Telangana. Operational SCADA data, reviewed by GRID-India, revealed significant power overdraw by southern states during the critical evening peak hours of 6 pm to 12 am. Kerala recorded 492 MW, peaking between 7-8 pm, followed by Andhra with 466 MW between 9-10 pm. Karnataka and Telangana reported 327 MW and 296 MW respectively, both peaking from 8-10 pm.

The pronounced overdraw during these vulnerable hours pointed to a stark imbalance between regional electricity demand and available generation. “This kind of low-frequency operation demands urgent and effective corrective actions by SLDCs to maintain the load-generation balance,” said RK Porwal, director (system operation), GRID-India. “It’s important of ensure transmission network integrity and adequate generation capacity, especially as the country enters a high-demand season.”

The letter urged all the states, including TN, to prioritise operational checks and readiness of grid defence mechanisms, including AUFLS, Special Protection Schemes, and Automatic Demand Management Schemes. It also called for issuing directions to all relevant stakeholders to act promptly to secure grid stability.

Southern Regional Power Committee’s Operation Co-ordination Committee, which has shared the official letters in its agenda for the meeting scheduled on May 9, will discuss the issue soon.