The Nigerian Independent System Operator (NISO), a key unit within the Transmission Company of Nigeria (TCN), has attributed the national grid collapse recorded on Friday to the simultaneous tripping of several 330 kilovolt transmission lines, compounded by the disconnection of some grid-connected power generation units.
The system operator disclosed this in an official statement released on Friday, January 23, through its verified social media platforms, as it provided updates on the incident and ongoing restoration efforts across the country.
According to NISO, operational reports from the national control centre confirmed that the combined effect of multiple transmission line failures and the sudden loss of generation capacity destabilised the power system, ultimately leading to the nationwide outage.
The operator explained that the disturbance occurred when several critical 330kV lines tripped almost at the same time, creating a sharp imbalance between electricity generation and demand. This imbalance was further worsened by the automatic disconnection of some power plants that were supplying electricity to the grid at the time of the incident.
Power system experts note that the national grid is designed with protective mechanisms that isolate faults to prevent widespread damage to equipment. However, when multiple faults occur simultaneously, especially on high-voltage transmission lines, the system can become overwhelmed, resulting in a complete or partial grid collapse.
NISO said restoration activities commenced promptly at about 1:15 pm, in accordance with established grid recovery and restoration procedures. These procedures involve a carefully sequenced process of re-energising transmission lines, synchronising power stations, and gradually reconnecting distribution networks to avoid further instability.
“As of the time of this update, power supply has been successfully restored to Abuja, Osogbo, Benin, Onitsha, Sapele, Jebba, Kainji, Shiroro and parts of Lagos, while restoration efforts are ongoing progressively across other parts of the country,” the statement said.
The operator assured electricity consumers that engineers and system operators were working round the clock to stabilise the grid and restore supply to all affected areas as quickly as possible.
In addition to the immediate response, NISO revealed that a comprehensive investigation has been launched to determine both the root and contributory causes of the disturbance. The probe, it said, would examine the condition of the affected transmission lines, the performance of grid protection systems, and the sequence of events that led to the disconnection of generation units.
The findings of the investigation are expected to inform corrective measures aimed at preventing similar incidents in the future, particularly as concerns continue to mount over the frequency of grid collapses in the country.
Data obtained from the system operator showed that power generation was gradually improving as the restoration process progressed. As at the time of filing the report, seven power generation companies were contributing a combined total of 1,118.80 megawatts to the national grid.
Although this figure remains significantly below the country’s installed generation capacity, NISO noted that the incremental increase reflects the cautious approach required to stabilise the grid after a major disturbance.
On the distribution side, load allocation to the eleven electricity distribution companies (DisCos) also showed signs of recovery. Collectively, the DisCos were allocated a total load of 1,540 megawatts as restoration continued.
Ikeja Electricity Distribution Company received the highest allocation at 350 megawatts, reflecting the high demand profile of its coverage area, which includes parts of Lagos. Abuja DisCo followed with an allocation of 270 megawatts, while Ibadan DisCo received 240 megawatts.
Eko DisCo, which serves parts of Lagos and its environs, was allocated 200 megawatts. Kano DisCo received 100 megawatts, while Kaduna DisCo was allocated 150 megawatts. Enugu DisCo had an allocation of 100 megawatts, Benin DisCo received 70 megawatts, and Sapele area benefitted from partial restoration through connected substations.
At the lower end of the allocation scale, Yola and Jos DisCos recorded the least, with 30 megawatts each. Port Harcourt DisCo had no allocation at the time of the report, standing at 0.00 megawatts, as restoration to that axis had yet to commence or be completed.
NISO emphasised that these allocations were subject to change as more generation units come online and additional transmission lines are re-energised.
The system operator reiterated that restoration efforts would continue in phases until full stability is achieved on the national grid. It appealed for patience from electricity consumers, noting that the gradual approach is necessary to ensure the safety of equipment and prevent another system collapse.
Friday’s incident adds to a growing list of grid disturbances in recent years, fuelling public concern about the resilience of Nigeria’s power infrastructure and the need for sustained investment in transmission capacity, system protection and maintenance.
As investigations continue, NISO maintained that lessons learned from the incident would be applied to strengthen grid operations and improve the reliability of electricity supply nationwide.
