The Grid Controller of India (GRID-India) has flagged a sustained frequency oscillation event in the Bhadla-Bikaner-Fatehgarh renewable energy complex in Rajasthan earlier this month.

The event occurred between 10:26 AM and 10:40 AM on May 11, 2026, during which oscillations in voltage, active power, and reactive power were recorded across seven renewable energy projects with a cumulative capacity of 3,168 MW.

GRID-India has asked these renewable energy developers to conduct a detailed root cause analysis of the oscillation event and submit a report within 15 days.

In a communication to renewable energy developers’ associations, GRID India said that according to an analysis based on phasor measurement unit (PMU) data, the 400 kV bus voltage at the Bhadla substation varied sharply between 373 kV and 440 kV during the event. This severe system-wide oscillation calls for a detailed review by the renewable energy developers and original equipment manufacturers (OEMs).

The preliminary assessment covered the timing of oscillation onset, active and reactive power swings, dissipated energy flow, and the Q-V phase relationship. Certain projects showed early oscillatory response and positive energy-flow characteristics.

Explanations have been sought from the following projects:

• SJVN Green’s 888 MW project at Bikaner-II
• Eden Renewable Alma’s 300 MW project at Bhadla-II
• GEPL’s 300 MW project at Bikaner-II
• XL Xergi Power’s 400 MW project at Fatehgarh-III
• SPCEP’s 300 MW project at Bikaner
• Altra Exergi’s 380 MW project at Fatehgarh-III
• Ayana’s 600 MW project at Bikaner

Developers must specifically examine inverter response, plant controller behavior, power plant controller settings, reactive power and voltage control functions, and any protection or control action that may have occurred during the oscillation period.

They must support their findings with disturbance recorder data, event logger records, protection relay event logs, low-voltage ride-through and high-voltage ride-through activation records, and internal or OEM analyses.

GRID-India also expressed concern about the unavailability of complete PMU data for 24 renewable energy projects totaling 6,751 MW during the event window. PMU data was available for only 71.4% against the target of 100%.

It noted that the lack of PMU data significantly affected post-event analysis and source identification. It directed developers to immediately resolve PMU data availability issues and ensure 100% data availability for future events.

The letter also referred to the root cause analysis reports that remain pending in response to a January 27, 2026, communication seeking data on 15 earlier major oscillation events that had been shared with renewable energy associations and developers.

According to an earlier GRID-India discussion paper, major renewable energy complexes, particularly in Rajasthan, had revealed challenges related to low system strength, altered fault behavior, weak-grid oscillations, and sensitivity of inverter controls.

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