Sri Lanka’s nationwide electricity failure on the 17th began with the sudden loss of 187 megawatts of power from the first generating unit of the Lakvijaya coal-fired power station in Norochcholai, according to a preliminary investigation report submitted to the Public Utilities Commission by the National System Operator.
The report states that the loss occurred at approximately 11.43am, with the 187MW supply disappearing from the national grid within 450 milliseconds. The sudden reduction in generation caused the electricity system’s frequency to fall rapidly to 48.75 hertz, resulting in a complete collapse of the national grid within 4.1 seconds of the initial incident.
The National System Operator said all five stages of the Under Frequency Load Shedding (UFLS) mechanism were activated during the incident. The automatic protection system is designed to disconnect electricity loads when grid frequency falls, helping to preserve the stability of the network.
However, the protective measures failed to prevent the complete system collapse. According to the report, 449.2MW of electricity was disconnected through the load-shedding mechanism, equivalent to 39.6 per cent of the total 1,135MW generation available immediately before the failure.
The disruption also triggered protective shutdowns at several other power stations. In addition to generating units at Norochcholai, units at the Victoria, Kotmale, Randenigala, Samanalawewa and Lakshapana hydropower stations, along with several other hydroelectric facilities, were taken out of operation after their protection systems activated.
The National System Operator began restoration work immediately after the collapse, using four main electricity generation and transmission systems to progressively reconnect the national network.
These included the Mahaweli system, using the Kotmale and Victoria power stations; the Lakshapana system, involving the New Lakshapana and Wimalasurendra hydropower stations; the Samanalawewa/Southern system, using Samanalawewa and Kukule Ganga; and the Colombo system, based on the Kelanitissa power station complex.
The report states that restoration of the transmission network took five hours and 15 minutes. All major substations had been brought back into operation by 4.58pm, marking the restoration of the national transmission system.
The report also identified technical difficulties and operational delays during the process of reconnecting generating stations to the grid. In particular, the restart of a generating unit at the Yugadanavi power station was delayed because of a technical problem involving one of its auxiliary systems.
Despite identifying the sequence of events that led to the collapse, the preliminary report has not established the precise underlying cause of the sudden loss of generation at Norochcholai’s first unit.
The National System Operator has said a more comprehensive report examining the incident will be submitted to the Public Utilities Commission at a later date.
