According to the Transmission Company of Nigeria (TCN), the unexpected drop in system frequency from 49.94 Hertz (HZ) to 47.36Hz, which led to system instability, is what caused the national grid to collapse.
Hertz, a frequency measurement unit, has replaced the previous concept of one cycle per second (cps).
This information was released in a statement to the media on Thursday in Abuja by TCN’s general manager of public affairs, Mrs. Ndidi Mbah.
Mbah said that reports from the National Control Centre (NCC), revealed that the collapse was precipitated by the tripping of a unit with a load of 106 Megawatts (MW) in one of the generating stations due to “Exhaust over Temperature”.
She said the tripping pulled out other grid-connected units in the plant, which resulted in aggregated generation loss of 457MW.
Mbah said, ”The incident was a result of sudden drop in system frequency from 49.94 Hertz (HZ) to 47.36Hz, which created system instability.
“A train of events ensued, culminating in the collapse of the national grid.
“As obtainable in all systems, when a component of the electric power system is defective, the entire configuration is vitiated”, she stated.
She also noted that an investigation was going on to establish the cause of the failure.
Meanwhile, Mbah in the statement also disclosed that the restoration of the national grid was almost completed following its collapse on Wednesday.
She said that the national grid experienced system disturbance at about 11:27a.m. on Wednesday, but that its restoration was almost completed as at 11:00p.m.
The TCN spokesperson said the Nigerian Electricity Supply Industry (NESI) appreciated the understanding of the government and consumers of electricity within and outside the country, noting that NESI was committed to leveraging on interventions instituted thus far to enhance power supply reliability.