The state of South Africa's power stations - according to Eskom

Eskom needs to add thousands of megawatts to SA's power grid in the next two years, just to keep up with the country's needs.

Eskom COO Jan Oberholzer and other senior officials at the embattled utility spoke at the utility's system status and outlook briefing on Monday morning, where they outlined the state of the country's power stations. 

Oberholzer said the upgrades to the system needed to be on a sound financial basis but they needed to be done to grow the country's economy. In total, between 4,000MW and 6,000MW were needed in two years. 

“We need a strong performance distribution and we need to sustain it. I'm concerned about the protection of old assets and financial challenges [Eskom faces] ... Funds have been released late, but they have been released and we will continue the process to fix the design faults,” he said.

He added that he was “convinced” that the focus needed to be on maintenance.

The COO began the briefing with an overview and summary of the Eskom's system's year-to-date performance, which included:

• Good performance from the transmission and performance sectors but generation of electricity still concerning; 
• The distribution technical performance is positive;
• Transmission performance positive — low number of interruptions and no major incidents;
• Since February, 1,594MW of new generation capacity was commissioned;
• Coal stock levels are healthy, costs reduced and wet coal to be avoided;
• Environmental matters, emissions and water consumption, have improved, but are not yet at the set targets;
• Safety below the tolerance levels, despite an employee and a contractor fatality;
• Generation remains a concern, specifically the availability of the coal power stations;
• Energy Availability Factor (EAF) at 65.3% is not at targeted level of performance;
• Contributing to the low EAF was high levels of planned maintenance;
• Recent high levels of unplanned outages is a concern;
• Eskom was forced to implement load-shedding on October 25, due to increasing breakdowns and low plant availability, totalling 29 days since April 1; and 
• Eskom has used more than the anticipated levels of diesel on its open-cycle gas turbines (OCGT).

According to Eskom, it was correcting all the major boiler plant defects (that is, mills, gas air heaters, fabric filters, air and flue gas ducts, and reheaters) at both Medupi and Kusile plants.

A defect-correction programme was established in collaboration with the original boiler contractor, to test, develop and implement technical solutions at the two critical power stations.

Below are some of the repair, fault and maintenance issues Eskom has had to deal with recently.

Medupi: dry-cooled coal-fired power station in Limpopo 

• On July 31, Medupi Unit 1, the last of six generation units, was successfully commissioned and handed over to generation. 
• The boiler plant modifications have been implemented on all six units, except for the long lead time milling modifications and the duct erosion modifications on Unit 6. 
• Medupi Unit 3 was used as a pilot for the initial implementation of boiler plant defect solutions, which require extended unit outages to execute. 
• The process to address design defects at Medupi is progressing well and from next year Eskom will implement additional enhancements.
• After the failure of Medupi Unit 4 (see incident below), the capacity plan was revisited and optimised. No outages were cancelled and the Medupi 4 failure continues to have significant affect on generation’s Unplanned Capacity Loss Factor (UCLF) allowance.
• The plan requires OCGT usage over weekdays, and low diesel use on some weekends. The failure of Medupi 4 has increased the dependency on diesel generation to manage the power system.

The incident:

Medupi Unit 4 was on outage for mill repairs between August 6-15. An external generator hydrogen leak was also discovered at the time.

Eskom group executive of generation Phillip Dukashe explained that hydrogen is used as a cooling agent, but will combust if it comes into contact with air. Therefore, when hydrogen is added or extracted (purged) to the generator, the generator is first pumped with CO₂ to avoid an explosion. 

The operating department was tasked with the purging of hydrogen from the generator before the leak search.

It appears air was introduced into the generator at a point where hydrogen was still present and Unit 4 exploded.

This caused severe damage to the generator and exciter and the turbogenerator auxiliaries — the extent of which is yet to be confirmed. It damaged the fire systems and civil structures and fire doors of Units 4 and 5. It also damaged equipment and battery rooms.

Seven employees were treated for shock. There were no other injuries.

Kusile: coal-fired power plant under construction in Mpumalanga

• Kusile Power Station is 50% complete — three of the six units completed.
• March 29, Kusile Unit 3 achieved commercial operation.
• In June the Unit 1 boiler plant modification outage was completed.
• The process to address design defects at Kusile is progressing well and from next year Eskom will implement additional enhancements.

The lower than expected availability of Tutuka, Duvha and Kendal reduced generation’s electricity availability factor EAF by between 3% and 6%, assuming they could perform at the targeted EAF.

Tutuka, Duvha and Kendal contributed about 46% of the total unplanned capability loss factor in year to date. Boiler, turbine, draught and milling plants were the main contributors (60%) for the period of September 30. 

Tutuka: coal-fired power plant in Mpumalanga

• Tutuka’s performance has constantly been below the budget for the review period.

Duvha: coal-fired power plant in Mpumalanga

• Duvha had a better performance vs the budget in November, December and May, otherwise the EAF performance has been constantly below the budget.

Kendal: coal-fired power station in Mpumalanga

• Kendal’s performance has constantly been below the budget for the review period.
• On September 11 at 3.36am the Unit 1 main generator transformer failed and caught fire (see incident below).
• Units 2 and 3's cables were repaired and both returned to service on September 14.
• Unit 1 recovery scope of work was frozen on October 14.
• Unit 1 transformer and associated systems work and cold commissioning is scheduled for completion on December 2.
• Unit 1 return to service expected on December 22.

The incident:

The unit tripped on the generator transformer pressure relief device and transformer differential protection.

Burning oil from the transformer flowed into the main cooling (MCW) ducting, burning cables that affected Units 2 and 3.

All requested investigation data has been captured and an investigation is in progress.

Transformer failed on blue phase (fault directly down to earth), but the root cause of the failure is under investigation by Eskom's forensic team.

Civil structure damage assessment due to the fire has been concluded and repairs are in progress with an estimated completion on November 15. 

Camden: coal-fired power plant in Mpumalanga

• First ash deposition was achieved at the Camden Power Station Ash Facility on October 2.
• But commercial, construction issues, including inclement weather and Covid-19 constraints are affecting execution.
• Camden’s ash constraint contributes about 39% to total year to date operational capability loss factor of 2.68%.

Majuba: coal-fired power plant in Mpumalanga

• The first coal train was successfully offloaded at the Majuba power station coal tippler facility.
• But commercial, construction issues, including inclement weather and Covid-19 constraints are affecting execution.

Koeberg: nuclear power station in Cape Town

• Koeberg is fully operational and the project to replace the steam generators is on track for 2022.
• Unit 1 tripped after being on line for 75 days on August 30, due to a protection relay failure on a primary pump breaker. The unit was returned to service on September 3.
• Unit 2 has been online for 344 days (as at September 30) since completing its last refuelling outage in October 2020.
• The reactor pressure vessel head arrived at Koeberg on October 11.
• Three steam generators are already on site and are being prepared for installation during the Unit 2 outage starting in January 2022.
• The remaining three steam generators are nearing manufacturing completion and will be delivered to site in time for the next Unit 1 outage, scheduled to start in September 2022.
• The long-term operation activities to enable Koeberg to operate for another 20 years beyond 2024/254 continue as per schedule. The formal application to extend the operating licence has been submitted to the National Nuclear Regulator and accepted for further processing.

Coal-related losses at 0.85% contributed about 31% of the total operational capability loss factor (OCLF) year to date, with Matla Power Station in Mpumalanga at 195MW (51%) and Kriel Power Station in Mpumalanga at 148MW (39%) being the biggest contributors.

Ingula: pumped storage scheme in KwaZulu-Natal

• Completed as part of the new build programme, which focuses on bringing new capacity online and driving plant defect corrections.

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