By Faith Anisiobi, The Sight News
The Nigerian Independent System Operator (NISO) has attributed recent changes in power allocations to Distribution Companies (DisCos) serving Lagos, Abuja and the northern parts of the country to multiple transmission line outages and constraints on the national grid.
NISO, in a statement, said the adjustments were made as part of normal system operations to keep the interconnected electricity network within secure operating limits.
The operator explained that the availability of electricity generation does not automatically guarantee that power can be delivered to a particular load centre, noting that power transfer depends largely on the availability and capacity of transmission infrastructure as well as the prevailing configuration of the network.
According to NISO, it continuously monitors and assesses available transmission capacity and network configuration in determining safe generation dispatch and load allocation across the Nigerian Electricity Supply Industry (NESI).
In the Lagos axis, NISO said successive outages involving the Olorunsogo–Ayede 330kV Line 1, Benin–Egbin 330kV Line 1 and Benin–Omotosho 330kV Line 1, alongside the prolonged outage of the Osogbo–Ikeja West circuit, reduced transmission transfer capability into the Lagos complex.
As a result, power allocations to Eko Electricity Distribution Company (EKEDC), Ikeja Electric Distribution Company (IE) and the Sakete international supply were reviewed and curtailed in line with network security requirements.
The Northern corridor was also affected by the tripping of the Shiroro–Mararaba 330kV Line 1 between August 24 and 26, which affected power allocation to Abuja and northern parts of the country as the load was supplied through the remaining circuit.
NISO said the situation became more critical at 6:47 a.m. on August 27, when the Shiroro–Mando 330kV Line 2 and Mando–Jos 330kV Line 1 tripped simultaneously.
At the time, the Mando–Jos line was the only available transmission circuit serving Jos and the North-East, while the alternative Apir–Lafia 330kV Lines 1 and 2 had remained out of service for an extended period due to faults.
The simultaneous outages caused a significant loss of transmission supply to Jos and the North-East, while the separation of the bus at the Mando Transmission Substation further altered the network configuration and constrained power transfer to affected northern load centres.
Consequently, NISO said it had to revise and curtail allocations to Kano, Kaduna, Jos, Yola and other affected areas to ensure that the remaining network operated within secure limits.
On the Abuja axis, the operator said the Shiroro–Katampe 330kV Line 1 and Gwagwalada–Katampe 330kV Line 1 tripped simultaneously at 3:55 a.m. on August 29, temporarily constraining transmission supply to the Federal Capital Territory.
It said the two circuits were restored at 7:25 a.m. and 7:20 a.m., respectively, after which the affected transmission capacity was recovered.
NISO stressed that the incidents demonstrated the interconnected nature of Nigeria’s power system, where the outage of a critical transmission circuit in one location can affect electricity transfer to load centres in other geographical areas.
The operator maintained that generation availability alone does not translate into deliverable electricity for DisCos, stressing that adequate transmission capacity and a secure network configuration are equally essential.
It explained that when transmission constraints or changes in network configuration affect the safe transfer of available generation, NISO may temporarily redispatch generation, curtail load or revise DisCo allocations to maintain system security and prevent wider network disturbances.
NISO therefore clarified that the recent changes in power allocations were caused by transmission line outages, constrained transmission capacity and prevailing network configurations, rather than a shortage or availability of generation.
The operator said the clarification was issued to place the facts on record and provide the public with a clearer understanding of the circumstances surrounding the recent changes in power allocations.
