By Mary Izuaka

 

The Nigerian Independent System Operator (NISO) on Sunday said recent reductions in electricity allocations to distribution companies in Lagos, Abuja and parts of Northern Nigeria were caused by multiple transmission line outages.

In a statement signed by the Management, NISO explained that adjustments to load allocations were made in the course of normal system operations to ensure that the interconnected network remained within secure operating limits after several 330kV circuits tripped in the past week.

“The availability of generation does not, by itself, guarantee that the available power can be delivered to a particular load centre. Power transfer is dependent on the availability and capacity of transmission infrastructure and the prevailing configuration of the network.”

The agency, which is responsible for real-time monitoring, coordination and dispatch of the and dispatch of the interconnected Nigerian Electricity Supply Industry (NESI), said it continuously assesses available transmission capacity and system configuration in determining safe generation dispatch and load allocation.

Lagos complex

According to NISO, the Lagos complex suffered the cumulative impact of four critical outages.

The affected lines are the Olorunsogo–Ayede 330kV Line 1, Benin–Egbin 330kV Line 1, Benin–Omotosho 330kV Line 1, and the prolonged outage of the Osogbo–Ikeja West circuit.

The cumulative loss of these critical circuits, NISO said, reduced the transmission transfer capability into the Lagos axis.

Consequently, NISO said it reviewed and curtailed load allocations to Eko Electricity Distribution Company (EKEDC), Ikeja Electric Distribution Company (IE) and the Sakete international supply, in accordance with the prevailing network configuration and system-security requirements.

Northern Corridor

NISO said the Northern corridor experienced tripping of Shiroro–Mararaba 330kV Line 1 from 24 to 26 August.

This, it said, affected load allocation to Abuja, and Northern part of the country as load was supplied solely through the remaining circuit.

“More significantly, at 06:47hrs of 27 August 2026, the Shiroro–Mando 330kV Line 2 and Mando–Jos 330kV Line 1 tripped simultaneously,” it said.

During that time, the system operator said the Mando–Jos 330kV Line 1 was the only available transmission circuit serving the Jos and North-East areas.

“The alternative circuits, Apir–Lafia 330kV Lines 1 and 2 have been out of service for an extended period, due to faults.

“The simultaneous outage resulted in a significant loss of transmission supply to the Jos and North-East areas. The separation of the bus at the Mando Transmission Substation further altered the network configuration and constrained power transfer to the affected northern load centres,” it added.

This condition, it said, necessitated the revision and curtailment of power allocations to Kano, Kaduna, Jos, Yola and other affected areas in order to operate the remaining network within secure limits.

Abuja axis

NISO said at 03:55hrs of 29 August, the Shiroro–Katampe 330kV Line 1 and Gwagwalada–Katampe 330kV Line 1 tripped simultaneously, temporarily constraining transmission supply to the Abuja axis.

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“The circuits were restored at 07:25 hrs and 07:20 hrs respectively, following which the affected transmission capacity was recovered.”

NISO stressed that the incidents highlight how interconnected the Nigerian power system is, noting that the outage of a single critical circuit can affect power transfer far beyond its immediate geographical location of the outage.

“Generation availability does not automatically translate into deliverable power to distribution companies. Adequate transmission capacity and a secure network configuration are equally essential.

“Where transmission constraints or changes in network configuration affect the ability to safely transfer available power, NISO needs to temporarily redispatch generation, curtail load or revise DisCo allocations in order to maintain system security and prevent wider network disturbances,” the statement said.

Accordingly, NISO said the recent changes in power allocations resulted from transmission line outages, constrained transmission capacity and system configuration prevailing at the respective times, rather than being attributed to generation availability.