High Solar PV Penetration Blamed for Power Failure

Colombo (News 1st): The Ceylon Electricity Board (CEB) has announced a series of immediate and long-term measures to enhance grid stability following the nationwide power failure on February 9, 2025. 

The outage was triggered by a disturbance at the 33kV Panadura Grid Substation, leading to a sudden voltage drop across the network.

At the time of the incident, over 50% of the national electricity demand was met by 800 MW of solar photovoltaic (PV) generation, supplemented by the Lakvijaya Power Plant at Norochcholai (470 MW) and hydropower plants (130 MW). 

The high penetration of non-synchronous solar PV generation resulted in low system inertia, making the grid vulnerable to faults. The disturbance caused an imbalance between generation and demand, leading to cascading disconnections and a total power failure.

Key Factors Contributing to the Outage:

High Solar PV Penetration & Low Inertia: The lack of synchronous generation made the grid more susceptible to voltage and frequency disturbances.

Solar PV Disconnection: A sharp voltage drop caused multiple solar PV systems to disconnect, exacerbating the imbalance and further destabilizing the grid.

Norochcholai Power Plant Tripping: The plant's automatic protective response to system instability prevented catastrophic damage and prolonged outages.

The CEB attributed the outage to the "Sunny Sunday" effect, where low weekend demand combined with high solar PV generation creates grid instability. With most industrial and commercial customers offline, the grid operated with reduced demand and inertia, making it more susceptible to sudden disturbances.

Immediate Measures:

Maintaining more synchronous generators at minimum generation and operating selected gas turbines in synchronous condenser mode at key locations to enhance grid stability and voltage support.

Curtailing ground-mounted solar PV generation during low-demand periods to mitigate instability risks.

Medium-Term Strategies:

Adjusting rooftop solar PV inverter settings to prevent unnecessary disconnections during minor disturbances.

Introducing special industrial tariffs for weekends and holidays to encourage industries to shift operations to low-demand periods.

Promoting solar installations with appropriate Battery Energy Storage Systems (BESS) capacities.

Long-Term Grid Stability Solutions:

Deploying grid-forming inverters with BESS to provide synthetic inertia and frequency stabilization.

Installing emergency backup generators at Norochcholai Power Plant.

Accelerating the Maha Oya Pumped Hydro Project (Water Battery) – a 600 MW storage facility.

Advancing Smart Grid investments to improve real-time monitoring and control of renewable energy integration.