NISO Blames Transmission Constraints for Epileptic Power Supply in Lagos, Others

By Adedapo Adeosanya, Omolola Makanjuola

The Nigerian Independent System Operator (NISO) has disclosed that the shortage of electricity in Lagos, Abuja, and other northern parts of the country was caused by transmission line outages that affected the capacity of the national grid.

The system operator said the outages forced it to adjust generation dispatch and power allocations to ensure that the remaining transmission network operated within safe limits and to prevent a wider system disturbance.

In a statement signed by its management on Sunday, NISO said the changes were caused by transmission constraints and not a shortage of generation.

NISO explained that having sufficient electricity generation was not enough to guarantee supply to a particular location because the transmission network must also have enough capacity to evacuate and transfer the available power.

“The Nigerian Independent System Operator wishes to provide clarifications on the recent changes in power allocations to Distribution Companies serving the Lagos, Abuja and Northern corridors.

“The changes in allocations occurred due to multiple transmission line outages that affected available transmission capacity and configuration of the network at different times. Adjustments were made in the course of normal system operations to ensure that the interconnected network remained within secure operating limits.

“The availability of generation does not, by itself, guarantee that the available power can be delivered to a particular load centre. Power transfer is dependent on the availability and capacity of transmission infrastructure and the prevailing configuration of the network,” the notice issued yesterday said.

The system operator, which is responsible for real-time monitoring, coordination, control and dispatch of the interconnected Nigerian Electricity Supply Industry (NESI), said it continuously assessed the transmission network before determining how much electricity could safely be delivered to different areas.

NISO said 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, while the Osogbo-Ikeja West circuit remained out of service for an extended period.

It also said the cumulative loss of the critical transmission circuits reduced the amount of electricity that could safely be transferred into the Lagos area. It consequently reviewed and curtailed allocations to Eko Electricity Distribution Company, Ikeja Electric and the Sakete international supply, based on the prevailing network configuration and system-security requirements.

The northern corridor was also affected by transmission failures. NISO said the Shiroro-Mararaba 330kV Line 1 tripped between August 24 and 26, affecting electricity allocation to Abuja and the northern part of the country because the remaining circuit had to carry the load.

NISO said the incidents demonstrated the vulnerability and interconnected nature of the national electricity network, where a fault on a single critical transmission circuit could affect electricity supply far beyond the location of the fault.

“Generation availability does not automatically translate into deliverable power to Distribution Companies. Adequate transmission capacity and a secure network configuration are equally essential.”

The operator added that where transmission constraints prevented the safe transfer of available generation, it had to temporarily redispatch generation, curtail load or revise DisCo allocations.

“Accordingly, the recent changes in power allocations resulted from transmission line outages, constrained transmission capacity and system configuration prevailing at the respective times, rather than being attributed to generation availability,” it added.