The Nigerian Independent System Operator (NISO) has attributed recent reductions in electricity allocations to Distribution Companies serving Lagos, Abuja and parts of northern Nigeria to multiple transmission line outages.

NISO said the outages reduced the capacity of the national transmission network, forcing it to temporarily adjust generation dispatch and electricity allocations to prevent further disruption and keep the grid operating within safe limits.

The system operator made this known in a statement issued by its management on Sunday, titled, “Clarification on Recent Changes in Power Allocations Following Transmission Line Outages.”

It said the reduced allocations were caused by transmission constraints rather than inadequate electricity generation.

NISO explained that available generation could not automatically translate into electricity supply to a particular location, stressing that sufficient transmission capacity was also required to move generated power to load centres.

According to the operator, the Lagos corridor was significantly affected by outages involving the Olorunsogo-Ayede 330kV Line 1, Benin-Egbin 330kV Line 1 and Benin-Omotosho 330kV Line 1.

It added that the Osogbo-Ikeja West circuit had also remained unavailable for an extended period.

NISO said the combined loss of the transmission circuits reduced the volume of electricity that could be safely transferred into Lagos, leading to adjustments in allocations to Eko Electricity Distribution Company, Ikeja Electric and the Sakete international supply.

The operator said the adjustments were made according to the condition of the network at the time and the need to maintain system security.

The northern part of the country also experienced transmission constraints following the tripping of the Shiroro-Mararaba 330kV Line 1 between August 24 and 26.

NISO said the incident affected power allocations to Abuja and northern areas because the remaining transmission circuit was required to carry the additional load.

The situation worsened at about 6:47am on August 27 when the Shiroro-Mando 330kV Line 2 and Mando-Jos 330kV Line 1 tripped simultaneously.

According to NISO, the Mando-Jos circuit subsequently became the only available transmission route serving Jos and the North-East, while the alternative Apir-Lafia 330kV Lines 1 and 2 had already been unavailable for an extended period because of faults.

The operator said the simultaneous failures significantly reduced the amount of power that could be transmitted to Jos and the North-East and also changed the network configuration following the separation of the bus at the Mando Transmission Substation.

It consequently revised and reduced allocations to Kano, Kaduna, Jos, Yola and other affected locations in order to keep the remaining transmission network within secure operating limits.

The Abuja transmission corridor experienced a similar incident on August 29 when the Shiroro-Katampe 330kV Line 1 and Gwagwalada-Katampe 330kV Line 1 tripped simultaneously at about 3:55am.

NISO, however, said both circuits were restored within hours, with the Shiroro-Katampe line returning to service at 7:25am and the Gwagwalada-Katampe line at 7:20am.

The system operator said the incidents highlighted the interconnected nature of Nigeria’s electricity grid, noting that an outage on a critical transmission line could affect electricity supply in areas far removed from the location of the fault.

NISO said it continuously monitors the transmission network and determines the quantity of electricity that can be safely delivered to different locations based on prevailing network conditions.

It stressed that generation capacity alone was insufficient to guarantee supply, as electricity delivery also depended on the availability and capacity of transmission infrastructure.

The operator said that when transmission constraints limit the safe movement of available electricity, it may be required to redispatch generation, curtail demand or adjust allocations to DisCos.

NISO therefore reiterated that the recent changes in electricity allocations were a result of transmission line failures, reduced transfer capacity and prevailing grid configuration, rather than a shortage of generation.

The clarification comes amid concerns over changing electricity allocations to DisCos in different parts of the country and highlights the continued impact of transmission infrastructure constraints on electricity supply despite available generation capacity.