The Nigerian Independent System Operator has attributed Friday’s nationwide power outage to the simultaneous tripping of key high-voltage transmission lines and the sudden loss of several power generation units connected to the national grid.

According to a preliminary incident report, the disturbance began around 12:40pm, triggering a chain reaction that shut down the interconnected transmission network and plunged the country into a total blackout. Operational data showed that electricity generation, which had been above 4,500 megawatts earlier in the day, crashed to about 24 megawatts at the height of the crisis.

All 23 grid-connected power plants reportedly went offline during the event, leaving the 11 electricity distribution companies across the country with no supply to deliver to homes and businesses. The collapse underscored the fragility of the national grid and the persistent vulnerability of Nigeria’s power infrastructure to sudden shocks.

NISO explained that the incident was “associated with the simultaneous tripping of multiple 330kV transmission lines, alongside the disconnection of some grid-connected generating units.” These combined failures, the operator said, “collectively contributed to the system collapse.”

Grid restoration efforts began at about 1:15pm, following established recovery procedures. Engineers worked to gradually re-energise transmission corridors and bring power plants back online in a controlled sequence to avoid further instability.

By the time of the operator’s update, supply had been restored to Abuja, Osogbo, Benin, Onitsha, Sakete, Jebba, Kainji, Shiroro and parts of Lagos, with work continuing to reconnect remaining parts of the country. The operator stressed that full stabilisation of the grid remained its top operational priority.

NISO also announced the launch of a detailed investigation to determine the root and contributory causes of the disturbance. The probe is expected to examine the performance of protection systems, the condition of critical transmission assets, and the operational status of generating units at the time of the collapse.

The outcome of the investigation is likely to shape future measures aimed at strengthening grid resilience, including possible upgrades to transmission infrastructure, stricter compliance with grid codes, and improved coordination between generators, the system operator and distribution companies.