NISO blames transmission outages on changes in power allocation

NISO blames transmission outages on changes in power allocation

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 have affected available transmission capacity and grid configuration at different times.

According to NISO, the adjustments were made during normal system operation to ensure that the interconnected network remained within safe operational limits.

NISO explained that generation availability does not, in itself, guarantee that available energy can be delivered to a particular load center, emphasizing that energy transfer depends on the availability and capacity of transmission infrastructure, as well as the prevailing grid configuration.

As the independent system operator responsible for real-time monitoring, coordination, control and dispatching of Nigeria’s interconnected electricity supply industry (NESI), NISO said it continuously evaluates available transmission capacity and system configuration to determine safe dispatching of generation and load allocation.

Lagos Complex

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

“The cumulative loss of these critical circuits has reduced the transmission carrying capacity in the Lagos axis.

“Accordingly, NISO has reviewed and reduced load assignments to Eko Electricity Distribution Company (EKEDC), Ikeja Electric Distribution Company (IE) and Sakete International Supply, in accordance with the prevailing grid configuration and system safety requirements,” it said.

North Corridor

The Northern Corridor experienced the disruption of the 330 kV Shiroro-Mararaba 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 load was supplied exclusively through the remaining circuit.

More significantly, at 6:47 am on August 27, 2026, Line 2 Shiroro-Mando 330 kV and Line 1 Mando-Jos 330 kV tripped simultaneously.

At the time, the Mando – Jos 330 kV Line 1 was the only transmission circuit available to serve the Jos and North East areas. The alternative circuits, Apir–Lafia 330kV Lines 1 and 2, had been out of service for a long period due to faults.

The simultaneous outage resulted in a significant loss of transmission supply in the Jos and North-East areas. NISO said bus separation at the Mando transmission substation further altered the grid configuration and limited power transfer to affected northern load centers.

“This condition has necessitated the review and reduction of power allocations in Kano, Kaduna, Jos, Yola and other affected areas in order to manage the remaining grid within safe limits,” NISO said.

Abuja Axis

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

The circuits were restored at 7.25am and 7.20am respectively, after which the affected transmission capacity was restored.

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

He emphasized that generation availability does not automatically translate into supplyable power to DisCos, as adequate transmission capacity and a secure network configuration are equally essential.

“Where transmission constraints or changes in grid configuration impact the ability to safely transfer available power, NISO must temporarily redispatch generation, reduce load, or review DisCo allocations in order to maintain system security and prevent broader grid disturbances,” he explained.

NISO therefore stated that recent changes in energy allocations are the result of transmission line outages, limited transmission capacity, and the prevailing grid configuration at the respective times, rather than generation availability.

The clarification, he 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 the assignment of power.