Cape Town - The Labour Court issued an order on Tuesday barring Numsa from striking at Eskom's plants, a spokesperson for the electricity firm said.
"We went to the Labour Court today and an interdict was granted preventing Numsa from embarking on a strike at Eskom," spokesperson Andrew Etzinger said.
They were demanding an increase of 12% across the board.
Union spokesperson, Castro Ngobese, said the court interdict would not stop them from demonstrating.
"We are continuing tomorrow whether they have an interdict or not," said Ngobese.
"We aren't threatened by Eskom's interdict and it should not be wasting money and energy on interdicts."
He said the manner in which Eskom had handled the matter had angered the workers.
The union's members had a right to demand better wages, Ngobese said.