• Failure to address issue increases likelihood of another nationwide blackout
• CEB will have to absorb additional cost of emergency power 
• Solar power to grid during weekends, holidays; unstable without storage

Sri Lanka’s power grid remains at severe risk of failure due to continued delays in implementing necessary measures to stabilise the system.

Despite the urgent need for action, the State-run Ceylon Electricity Board (CEB) has yet to find a viable solution, increasing the likelihood of another nationwide blackout similar to the one experienced last Sunday (9).

Sunday’s outage, which lasted six hours, was initially blamed on a monkey disrupting a grid station in a Colombo suburb. However, the larger issue lies in the instability of the system, exacerbated by the automatic shutdown of the Chinese-built Norochcholai Coal Power Plant.

Following the blackout, scheduled power cuts were imposed to manage the shortfall, yet no concrete steps have been taken to prevent a recurrence. 

Although discussions on short-term solutions, such as shifting to diesel-powered thermal plants, began as early as October-November last year, progress has been slow due to regulatory bottlenecks and lack of coordination between the CEB, Public Utilities Commission of Sri Lanka (PUCSL), and Ministry of Energy.

A senior engineer at the CEB, speaking on condition of anonymity, warned that the delay in decision-making would ultimately burden electricity consumers. 

“The system remains at risk and the decisions made by authorities are not in line with what is required to stabilise it. Moreover, with no immediate tariff revision expected for another six months, the CEB will have to absorb the additional cost of emergency power generation, most likely from diesel,” he explained.

While the system has an abundance of solar power generation, especially on weekends and holidays, it remains unreliable without backup stability measures. The failure to act swiftly has left the country vulnerable, with hydro and thermal oil power being the only immediate options. 

Unless urgent steps are taken, Sri Lanka could face further blackouts, underscoring the consequences of continued inaction.

Concerns over growing instability 

In a letter addressed to the Office of the Deputy General Manager (System Control), CEB National System Control Centre Deputy General Manager Eng. M.B.S. Samarasekara has once again raised concerns about the growing instability in Sri Lanka’s power system, specifically due to the rapid increase in rooftop solar and inverter-based Non-Conventional Renewable Energy (NCRE) sources. 

Despite these warnings, no effective action has been taken by the management to address the issue.

The instability has become particularly problematic on weekends and long holidays, especially sunny Sundays, when industrial and commercial electricity demand drops significantly. As a result, many dispatchable power plants remain idle, leading to frequency fluctuations and reduced system inertia, which, in turn, heightens the risk of major power failures – especially at critical power plants like Lakvijaya. 

Samarasekara has highlighted that on 22 September 2024, system demand fell to just 670 MW, prompting the curtailment of 160 MW of NCRE generation to prevent further instability. The frequency fluctuations have become increasingly common, especially during daylight hours on low-demand days, making the system more vulnerable to faults.

In the letter, Samarasekara has emphasised the risks associated with the shutdown of dispatchable plants to accommodate NCRE generation, which weakens the system’s inertia and makes the grid more prone to total collapse during disturbances.  

Proposed solutions

Several critical mitigating actions have been proposed, including introducing special industrial electricity tariffs on weekends and holidays to encourage increased power consumption and improve system stability. 

Samarasekara has also recommended operating large hydro plants like Victoria, Kotmale, Uma Oya, and New Laxapana in synchronous condenser mode to provide essential reactive power support without generating active power. 

Additionally, he has urged the operation of Gas Turbine Generator 7 (GT 7) at Kelanitissa in synchronous condenser mode, as it has the highest inertia constant in the thermal fleet, to help stabilise frequency fluctuations.

Furthermore, Samarasekara has stressed the need for fast frequency response solutions, such as Battery Energy Storage Systems (BESS), fast-acting gas turbines, and flywheel energy storage systems, to enhance system resilience. 

He has also proposed establishing an NCRE control desk at the National System Control Centre for real-time forecasting and response to grid disturbances, and reassessing the current 5% hot spinning reserve, which may no longer be adequate with the increasing penetration of NCRE.

In anticipation of future challenges, Samarasekara has recommended developing a structured curtailment mechanism for large-scale NCRE projects (above 5 MW capacity) to ensure grid security. Additionally, he has suggested optimising hydro and thermal plant operations by evaluating their minimum operating load and ramp rates, allowing for greater flexibility in generation and improved overall system inertia.

These proposed measures are crucial to stabilising the grid and preventing large-scale blackouts. However, despite repeated warnings and clear recommendations in the letter, the necessary steps have yet to be implemented by management, leaving the system vulnerable to further failures.

Behind the breakdown 

When contacted by The Sunday Morning, CEB Spokesman Eng. Dhammika Wimalaratne said the situation that arose due to the breakdown on Sunday highlighted the instability of the system. 

This instability is especially pronounced on Sundays due to the ‘sunny Sunday’ effect, which occurs when industrial and office activities are reduced, leading to lower demand while solar power generation remains high.

“On this particular Sunday, just before the breakdown, 50% of the generation came from solar power. The system became weak because fewer large power plants were operating. The big machines we rely on, such as Norochcholai and combined cycle plants, were not running at full capacity, and solar power does not provide the necessary inertia for stability. As a result, the system was vulnerable,” he said.

“To prevent such issues in the future, we must take immediate measures. One of the key factors in the recent breakdown was a fault at the KTKB busbar in Pannipitiya, which caused a sudden voltage drop. 

“Solar inverters in the affected area were programmed to disconnect when they sensed a voltage drop, leading to a chain reaction where solar generation was lost, creating an imbalance between demand and supply. The frequency dropped rapidly, affecting power plants across the country and ultimately leading to a total system failure,” Wimalaratne added.

Immediate actions required 

The Spokesman also noted that had there been a large rotating power plant operating in Colombo, the situation might have been different. A local power source could have absorbed some of the fault current, preventing system collapse. 

However, Sri Lanka’s cost-minimisation strategy prioritises solar power over thermal generation, reducing the number of running thermal plants and inadvertently weakening system stability.

“To address this issue, we must consider running a thermal power plant at minimum load, particularly on Sundays, to provide system inertia. The Colombo combined cycle power plant, running on naphtha, is a viable option since its cost is relatively low. This plant should be operated at a minimal load on weekends to maintain stability without significantly increasing costs,” he said.

Further, he went on to explain that another immediate action was revisiting the settings of solar inverters to ensure they remained connected to the system for a longer duration during disturbances. If they can sustain operations for at least 20 seconds, the system might be able to recover before a full collapse occurs.

“Additionally, we must address the ‘sunny Sunday’ effect by incentivising industries to operate on Sundays. This can be achieved by introducing reduced electricity tariffs on Sundays and  encouraging businesses to shift their operations, thereby increasing system demand and enhancing stability,” he added.

Wimalaratne highlighted that for a sustainable future, large-scale battery storage was crucial. Batteries can quickly inject power into the grid during disturbances, similar to large rotating machines. According to him, by 2026, Sri Lanka should aim to install at least 100 MW of battery storage as a fast-track measure.

Another long-term solution is pumped hydro storage, also known as a ‘water battery.’ This method utilises excess solar power during the daytime to pump water to an upper reservoir, which can then be released to generate electricity at night or during peak demand. 

He noted that this infrastructure should be in place by 2032-’33, with feasibility studies already completed and funding of approximately $ 450 million required for construction. 

Attempts by The Sunday Morning to contact Energy Minister Kumara Jayakody and Secretary Udayanga Hemapala were futile.