The National Union of Electricity Employees (NUEE) general secretary Joe Ajaero told Reuters the union would suspend the strike for two weeks after a meeting with TCN management and the minister of power.
"A committee chaired by the Minister of State for Power has been set up to work out modalities on resolution of the issues. Power would be restored either this night or tomorrow in the morning," Ajaero said.
Nigeria's 11 electricity distribution companies issued notices to clients on Wednesday saying that they were unable to supply power due to the strike.
Lagos-based Ikeja Electric, the largest distribution company, said "we are currently experiencing disruption of power supply as most stations within our network have been shut down."
The grid capacity had dropped to zero by 5:00 p.m. (1600 GMT) from 4,100 megawatts (MW) early on Wednesday, according to TCN. By 9:50 p.m. (20:50 GMT) capacity was at just 35 MW.
On Tuesday, Nigeria's national grid had a peak supply of 4,800 MW, the highest in many months but still far below what the country of 200 million people needs.
In calling the strike, NUEE had said in a notice to members that it was protesting against discriminatory promotion procedures at the state-owned transmission company and unfair labor practices in the power sector, among other grievances.
Due to reliability problems with Nigeria's electrical grid, a majority of businesses and homes rely on diesel and petrol-powered generators while many more go without electricity.