The Nigerian Independent System Operator (NISO) has attributed recent reductions in electricity allocations to Distribution Companies (DisCos) serving Lagos, Abuja and parts of northern Nigeria to multiple transmission line outages.
NISO said the outages constrained the capacity of the national grid, forcing it to adjust power generation dispatch and allocations to keep the remaining transmission network within safe operating limits and prevent a wider system disturbance.
In a statement signed by its management on Sunday and titled, “Clarification on Recent Changes in Power Allocations Following Transmission Line Outages,” the operator stressed that the reductions were caused by transmission constraints and not insufficient power generation.
NISO explained that adequate electricity generation alone does not guarantee supply to a particular location, as available power must be safely evacuated and transmitted through infrastructure with sufficient capacity.
According to the operator, the Lagos axis was particularly affected by successive outages on the Olorunsogo-Ayede 330kV Line 1, Benin-Egbin 330kV Line 1 and Benin-Omotosho 330kV Line 1, while the Osogbo-Ikeja West circuit remained out of service for an extended period.
The cumulative loss of these critical transmission circuits reduced the amount of electricity that could safely be transferred into Lagos, leading to revised and curtailed allocations to Eko Electricity Distribution Company, Ikeja Electric and the Sakete international supply.
NISO said the northern corridor also experienced transmission failures, including the tripping of the Shiroro-Mararaba 330kV Line 1 between August 24 and 26, which affected supply to Abuja and northern Nigeria as the remaining circuit carried the load.
The situation worsened at 6:47am on August 27 when the Shiroro-Mando 330kV Line 2 and Mando-Jos 330kV Line 1 tripped simultaneously.
NISO said the development significantly reduced transmission supply to Jos and the North-East, forcing it to revise and curtail allocations to Kano, Kaduna, Jos, Yola and other affected areas to maintain system security.
The Abuja axis was similarly affected on August 29 when the Shiroro-Katampe 330kV Line 1 and Gwagwalada-Katampe 330kV Line 1 tripped simultaneously at 3:55am. Both circuits were restored shortly afterwards.
NISO said the incidents highlighted the vulnerability of Nigeria’s interconnected electricity network, where a fault on a critical transmission line can affect power supply far beyond the location of the fault.
The operator reiterated that generation availability does not automatically translate into deliverable electricity, noting that adequate transmission capacity and a secure network configuration are equally essential.
It said that whenever transmission constraints prevent the safe transfer of available generation, it may temporarily redispatch generation, curtail load or revise allocations to DisCos.
NISO maintained that the recent changes in electricity allocations were therefore the result of transmission line outages, constrained transmission capacity and prevailing network conditions, rather than a shortage of generation.