Medupi power station owner Eskom reported on 9 August that there had been an explosion on the Unit 4 generator at approximately 10:50 pm on 8 August.
It is suspected that this was the cause of a trip on Unit 5 of the 6 unit coal fired plant.
No injuries were reported and all employees and contractors have been accounted for. Emergency services attended to seven personnel requiring treatment for shock.
Unit 4 was in a short-term outage (since 6 August) when the incident occurred. All work on the unit was suspended immediately and the area cleared, and inspections and assessments were begun to determine the cause of the incident and extent of the damage.
On 16 August Medupi reported as part of its preliminary findings that the explosion has resulted in extensive damage to the generator. The incident occurred during activity to displace hydrogen with carbon dioxide and air respectively, for the purposes of finding an external leak.
Following the preliminary investigation, it appears that while performing this task air was introduced into the generator at a point where hydrogen was still present in the generator at sufficient quantities to create an explosive mixture, which ignited and resulted in the explosion. It also appears that there was a deviation from the procedure for carrying out this activity.
This being so Eskom has undertaken to place those employees who were responsible to manage and execute this work under precautionary suspension pending the conclusion of the major event investigation.
Further investigations are now underway into the cause of the incident and Eskom will report on any developments, as well as to what extent this the incident will impact the national electricity grid.
The Medupi project has been at the centre of controversy since the start of its construction in 2007 owing to allegations of corruption in the contracting process and huge cost overruns, and has deviated from its loan conditions with the World Bank since it approved $3.75-billion for the new-build and for renewable energy expansion. Despite global pressure to reject the loan from 200 organisations and 2000 signatories in Southern Africa, the US and the UK, the World Bank granted it on the basis that the region’s development was reliant on energy security.
The company also had to deal with the allegations that the boilers supplied under a contract with Hitachi were not fit for South African coal and suffered design defects, while the welding was of poor quality.
Added to that, pressure has mounted over the utility’s special tariff agreements with South African steel smelters and mines, who were paying far less for power than average consumers, as part of agreements with Eskom.