Eskom has replaced France's Alstom with Swiss firm ABB Ltd in a control and instrumentation (C&I) contract for its much-delayed Kusile power station, the South African utility said on Friday.
A spokesman said the change would not delay completion of the plant, which is scheduled to begin producing power in 2017 to help end electricity shortages currently hampering Africa's most advanced economy.
A power station's C&I system monitors and controls engineering systems, machinery and processes.
Kusile is one of three large power plants Eskom is building as it scrambles to keep the lights on but work has been delayed by violent labour unrest and technical glitches.
Eskom's Medupi power station produced electricity this month for the first time but its first unit will take three months to achieve its full capacity of 794 megawatts.
Once both Medupi and Kusile are fully operational, they will produce over 9,000 megawatts, close to a quarter of what Eskom typically is able to generate at present.
South Africans face frequent, controlled power cuts which Eskom implements to prevent the national grid from being overwhelmed.
Ratings agency Standard & Poor's (S&P) on Thursday cut its credit ratings for Eskom to junk, which will almost certainly raise borrowing costs for the cash-strapped firm.
Last week, Eskom announced it had temporarily suspended CEO Tshediso Matona and three other executives while an inquiry is held into the company's operations.