The Nigerian Independent System Operator (NISO) has cited multiple transmission line outages as reason for the recent reductions in electricity allocations to Distribution Companies serving Lagos, Abuja and the northern parts of the country.
According to NISO, the transmission cuts constrained the capacity of the national grid, forcing 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.
The clarification was contained in a statement by the management of NISO, titled: “Clarification on Recent Changes in Power Allocations Following Transmission Line Outages.”
NISO explained that the changes were caused by transmission constraints and not a shortage of generation.
The clarification came amid concerns over changes in power allocations to DisCos in some parts of the country. 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 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 statement read.
NISO, which is responsible for real-time monitoring, coordination, control and dispatch of the interconnected Nigerian Electricity Supply Industry, said it continuously assessed the transmission network before determining how much electricity could safely be delivered to different areas.
The operator 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.
According to NISO, 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.
