Power Allocation: NISO Blames Transmission Outages for Cuts to Lagos, Abuja, North

"The outages had reduced available transmission capacity and forced the system operator to adjust generation dispatch and load allocations to keep the national grid within safe operating limits." Management 

.... Says "the availability of electricity generation did not automatically mean that the power could be delivered to a particular area."

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

NISO, in a clarification issued on Sunday, said the outages had reduced available transmission capacity and forced the system operator to adjust generation dispatch and load allocations to keep the national grid within safe operating limits.

It stressed that the availability of electricity generation did not automatically mean that the power could be delivered to a particular area, noting that transmission infrastructure and the prevailing configuration of the network were equally critical to power supply.

According to NISO, the Lagos axis was particularly affected by successive outages involving the Olorunsogo–Ayede 330kV Line 1, Benin–Egbin 330kV Line 1 and Benin–Omotosho 330kV Line 1, as well as the prolonged outage of the Osogbo–Ikeja West circuit.

It said the cumulative loss of the transmission circuits reduced the capacity to transfer electricity into Lagos, prompting it to curtail allocations to Eko Electricity Distribution Company, Ikeja Electric Distribution Company and the Sakete international supply.

The situation, it explained, was managed in line with the prevailing network configuration and system-security requirements.

The northern corridor also suffered significant transmission constraints following the tripping of the Shiroro–Mararaba 330kV Line 1 between August 24 and 26, which affected electricity allocations to Abuja and parts of northern Nigeria.

NISO said the situation became more critical at 6:47am on August 27 when the Shiroro–Mando 330kV Line 2 and Mando–Jos 330kV Line 1 tripped simultaneously.

It explained that the Mando–Jos circuit was, at the time, the only available transmission line 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.

The simultaneous outages, according to NISO, resulted in 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 restricted power transfer to affected northern load centres.

Consequently, allocations to Kano, Kaduna, Jos, Yola and other affected areas were revised and curtailed to enable the remaining network to operate within secure limits.

On the Abuja axis, NISO said two critical transmission circuits—Shiroro–Katampe 330kV Line 1 and Gwagwalada–Katampe 330kV Line 1—tripped simultaneously at 3:55am on August 29.

It, however, disclosed that both circuits were restored within hours, with the Shiroro–Katampe line restored at 7:25am and the Gwagwalada–Katampe line at 7:20am.

The system operator said the incidents underscored the interconnected nature of Nigeria's electricity network, where the failure of a critical transmission circuit could affect power supply far beyond the location of the fault.

NISO said its responsibility as the Independent System Operator included real-time monitoring, coordination, control and dispatch of the interconnected Nigerian Electricity Supply Industry.

It explained that whenever transmission constraints or changes in network configuration threatened the safe transfer of available electricity, it could temporarily redispatch generation, curtail load or revise DisCo allocations to maintain system stability and prevent wider disturbances.

The agency therefore dismissed any suggestion that the recent changes in allocations were primarily caused by inadequate generation, insisting that they resulted from transmission line outages, constrained transfer capacity and changes in network configuration at the affected times.

NISO said the clarification was issued to put the facts on record and help the public understand the circumstances behind the recent changes in electricity allocations.