The Nigerian Independent System Operator (NISO) has dismissed claims by the Association of Power Generation Companies (APGC) that the June 25 grid disturbance reflected a nationwide system failure, insisting the incident was a localized voltage instability confined to the Lagos axis and was effectively contained without disrupting the national electricity network.
In a strongly worded statement issued on Friday, NISO accused the power generation companies of presenting a misleading interpretation of the incident, warning that inaccurate public narratives could erode confidence in Nigeria’s electricity system.
According to the system operator, the disturbance was promptly detected and managed through coordinated operational interventions, preventing it from escalating into a nationwide grid collapse.
NISO said the event remained restricted to the Lagos region, where system operators successfully restored normal electricity supply within a short period through established emergency response procedures.
The clarification comes amid heightened public concern over the reliability of Nigeria’s electricity infrastructure, following recurring grid disturbances that have affected consumers, businesses and industrial activities across the country.
Rejecting APGC’s interpretation of system frequency, voltage and generation data, NISO argued that the analysis overlooked key provisions of the Nigerian Grid Code governing the management of system disturbances.
The operator explained that temporary fluctuations in frequency and voltage are expected during periods of system stress and restoration and should not automatically be interpreted as evidence of grid collapse or operational failure.
It noted that while the national grid normally operates within a frequency range of 49.75 to 50.25 Hertz and transmission voltage between 280.5 kilovolts and 346.5 kilovolts on the 330kV network, short-lived deviations are permissible during disturbances before corrective measures restore normal operating conditions.
NISO further explained that the Grid Code allows generating units to remain synchronized even when system frequency temporarily falls outside normal operating limits during restoration activities.
The operator also rejected APGC’s conclusions regarding the temporary decline in electricity generation recorded during the incident, describing the reduction as a deliberate operational response triggered by generator and network protection systems designed to safeguard the integrity of the national grid.
According to NISO, the activation of these protective mechanisms prevented wider cascading outages and enabled rapid stabilization and restoration of electricity supply.
The agency stressed that citing isolated minimum or maximum frequency readings without considering the broader operational sequence and restoration process presents an incomplete and misleading picture of the health of the national grid.
Reaffirming its statutory mandate, NISO stated that it remains the sole authority responsible for providing official information on grid operations, system disturbances and the performance of Nigeria’s electricity transmission network.
It urged policymakers, electricity market participants and the public to rely on verified information issued by the system operator for accurate updates on national grid operations.
The agency reaffirmed its commitment to maintaining the reliability, security and stability of the country’s electricity supply industry through strict adherence to the Nigerian Grid Code, transparent communication and internationally accepted operational standards.
The latest exchange highlights growing tensions between key stakeholders in Nigeria’s electricity sector over the interpretation of grid incidents and underscores the continuing debate on accountability, system performance and public communication within the country’s evolving power market.
