Under pressure: The mistake at Kendal that plunged SA into Stage 4 load shedding

Just after 02:00 on Thursday, red lights flashed on screens in the control room of Kendal Power Station in Mpumalanga, about an hour and a half's drive from Johannesburg.

Within minutes, the vast noise of rushing steam and turbines spinning faster than the speed of sound, encased in massive steel tombs, started to fade - and, for the first time in many years, a comparative hush fell over the 526-metre-long turbine hall of what was, for decades, the largest coal-fired power station in the world.

Electronic systems comprising a sprawling network of sensors that monitor thousands of data points, including pressures and temperatures, had detected an increase in the heat of water being used to cool hundreds of auxiliary systems spread out across the power station, each one playing a vital role in the infinitely complex machinery that is used to make electricity.