Transmission Line Outages Force Power Allocation Cuts in Lagos, Abuja, Northern Corridors — NISO Explains
Oru Leonard
The Nigerian Independent System Operator (NISO) has attributed recent changes in electricity 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 signed by its management on Sunday, said the outages reduced available transmission capacity and altered the configuration of the network, making it necessary to adjust power allocations in order to keep the interconnected system within safe operating limits.
The system operator stressed that the availability of electricity generation alone does not guarantee that the power can be delivered to a particular area, noting that effective power transfer also depends on the availability and capacity of transmission infrastructure and the prevailing configuration of the national grid.
According to NISO, it is responsible for the real-time monitoring, coordination, control and dispatch of the interconnected Nigerian Electricity Supply Industry (NESI), and continuously evaluates transmission capacity and network conditions when determining generation dispatch and load allocation.
Lagos affected by multiple transmission outages.
NISO said the Lagos complex was particularly affected by successive outages involving 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.
It said the cumulative loss of the critical transmission circuits reduced the capacity to transfer electricity into the Lagos axis.
Consequently, NISO said it reviewed and curtailed allocations to Eko Electricity Distribution Company (EKEDC), Ikeja Electric Distribution Company (IE) and the Sakete international supply, in line with the prevailing network configuration and system-security requirements.
The Northern corridor also experienced significant transmission challenges following the tripping of the Shiroro–Mararaba 330kV Line 1 between August 24 and 26, which affected power allocations to Abuja and other northern parts of the country.
NISO explained that during the period, the affected areas depended on the remaining transmission circuit for electricity supply.
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 the Jos and North-East areas, while the alternative Apir–Lafia 330kV Lines 1 and 2 had remained out of service for an extended period due to faults.
NISO said the simultaneous outage caused a significant reduction in 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 restricted power transfer to affected northern load centres.
As a result, power allocations to Kano, Kaduna, Jos, Yola and other affected areas were revised and curtailed to ensure that the remaining transmission network operated within secure limits.
Abuja supply temporarily constrained.
The Abuja axis also experienced a temporary transmission constraint on August 29, when the Shiroro–Katampe 330kV Line 1 and Gwagwalada–Katampe 330kV Line 1 tripped simultaneously at 3:55 a.m.
NISO said the two circuits were subsequently restored at 7:25 a.m. and 7:20 a.m., respectively, allowing the affected transmission capacity to be recovered.
The system operator explained that the incidents underscored the interconnected nature of Nigeria’s electricity network, where an outage affecting a critical transmission circuit can have consequences beyond the immediate location of the fault.
NISO reiterated that available generation does not automatically translate into electricity that can be delivered to DisCos.
It said adequate transmission capacity and a secure network configuration are equally necessary to move generated electricity to consumers.
“Where transmission constraints or changes in network configuration affect the ability to safely transfer available power,” NISO said, it may have to temporarily redispatch generation, curtail load or revise DisCo allocations to maintain system security and prevent wider network disturbances.
The operator therefore clarified that the recent changes in power allocations were caused by transmission line outages, constrained transmission capacity and prevailing system configurations, rather than a shortage of electricity generation.
NISO said the clarification was issued to put the facts on record and provide the public with a clearer understanding of the circumstances behind the recent changes in electricity allocations across the affected regions.
(NISO Media)
