NISO Blames Transmission Outages for Changes in Power Allocation

NISO Blames Transmission Outages for Changes in Power Allocation

By Goodness Ekpang

Abuja (Core Reporters) -The Nigerian Independent System Operator (NISO) has attributed recent changes in power allocations to Distribution Companies (DisCos) serving the Lagos, Abuja and Northern corridors to multiple transmission line outages that affected available transmission capacity and the configuration of the network at different times.

According to NISO, the adjustments were made in the course of normal system operations to ensure that the interconnected network remained within secure operating limits.

NISO explained that the availability of generation does not, by itself, guarantee that available power can be delivered to a particular load centre, noting that power transfer depends on the availability and capacity of transmission infrastructure as well as the prevailing configuration of the network.

As the Independent System Operator responsible for real-time monitoring, coordination, control and dispatch of the interconnected Nigerian Electricity Supply Industry (NESI), NISO said it continuously assesses available transmission capacity and system configuration to determine safe generation dispatch and load allocation.

Lagos Complex

NISO said the Lagos complex was affected by successive outages of the Olorunsogo–Ayede 330kV Line 1, Benin–Egbin 330kV Line 1 and Benin–Omotosho 330kV Line 1, in addition to the prolonged outage of the Osogbo–Ikeja West circuit.

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

“Consequently, NISO 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,” it said.

Northern Corridor

The Northern corridor experienced the tripping of the Shiroro–Mararaba 330kV Line 1 between August 24 and 26, 2026. NISO said the outage affected load allocation to Abuja and the Northern part of the country, as the load was supplied solely through the remaining circuit.

More significantly, at 6:47 a.m. on August 27, 2026, the Shiroro–Mando 330kV Line 2 and Mando–Jos 330kV Line 1 tripped simultaneously.

At the time, 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, had 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. NISO said the separation of the bus at the Mando Transmission Substation further altered the network configuration and constrained power transfer to affected northern load centres.

“This condition 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,” NISO said.

Abuja Axis

NISO said that at 3:55 a.m. on August 29, 2026, the Shiroro–Katampe 330kV Line 1 and Gwagwalada–Katampe 330kV Line 1 tripped simultaneously, temporarily constraining transmission supply to the Abuja axis.

The circuits were restored at 7:25 a.m. and 7:20 a.m., respectively, following which the affected transmission capacity was recovered.

According to NISO, the incidents demonstrate the interconnected nature of the Nigerian power system, where the outage of a critical transmission circuit can affect power transfer beyond the immediate geographical location of the outage.

It stressed that generation availability does not automatically translate into deliverable power to DisCos, as 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,” it explained.

NISO therefore said the recent changes in power allocations resulted from transmission line outages, constrained transmission capacity and the network configuration prevailing at the respective times, rather than from generation availability.

The clarification, it said, was intended to put the relevant facts on record and provide the public with a clear understanding of the circumstances surrounding the recent changes in power allocations.