ESKOM’s Cape Town-based Peaking Generation unit is responsible for meeting peak power demands on the national grid at a moment’s notice. This geographically-distributed initiative, consisting of hydro-electric, pump storage and gas turbine plants, is maintained in a high state of readiness at all times with the help of sophisticated condition-based monitoring systems.
In an environment with virtually zero tolerance for malfunctions, relevant information is often the only differentiator between success and failure. Such is the case for ESKOM's peak demand generation plants, which include pump storage schemes in the Drakensberg and at Palmiet in Grabouw, Cape Town as well as the Gariep (previously Hendrik Verwoerd) and Vanderkloof conventional hydroelectric power stations. In addition to this, ESKOM Peaking Generation operates two gas turbine plants, Acacia in Cape Town and Port Rex in East London.
"The stations bracket about a ten year span of supervisory and control technology ranging from relay ladder logic to PLCs," says Julian Visser, Senior Engineer, ESKOM Peaking Generation. "Over the past few years, however, we have gradually been introducing PC-based scada systems in order to provide with operators more information and to involve them to a greater degree in the efficient running of the plants. One of the key factors for achieving better efficiency is the accurate analysis of cause and effect scenarios in order not to repeat errors of the past.
"For example, when a plant is brought on-line, which often needs to happen in just a couple of minutes, it is vital to avoid trips or mode-change failures as this would defeat the rapid response requirement. However, if the system does trip, it is vital that we determine the root cause of that trip as soon as possible and, more importantly, make sure that the conditions which caused the trip in the first place are not only understood but are not repeated in the future. To this end, Sequential Event Recorders and scada systems have contributed enormously to our knowledge of the cause of incidents. This includes the integration of complex, realtime transient analyses which is necessary for the study of such realtime analogue events as circuit-breaker behaviour."
ESKOM's initiative to improve the efficiency of its Peaking Generation business unit would require open solutions that could be implemented by their own technical staff, since they best understand the job to be done.
These solutions would also have to provide their engineers with nationwide access to plant information for both proactive control and analysis purposes. Time-based preventative maintenance was to give way to condition-based maintenance while web-based reporting would be the order of the day.
"Today, we make extensive use of Wonderware's InTouch, IndustrialSQL and ActiveFactory solutions to meet our operational requirements while ESKOM's intranet means that all Peaking Power Stations are linked nationally and that we can get access to the best possible knowledge when we need it," says Visser. "We can now record trends and provide windows of knowledge into history down to millisecond resolution over virtually any time frame.
This provides engineers and operators an unprecedented level of decision support while achieving our original business objective of reduced operating costs through improved efficiency. We were assisted by system integrators at the start of the project but later took overall responsibility for ongoing system development and maintenance."
Efficiency alone, however, is not the only consideration. Quite apart from power generation and by virtue of the scale and nature of its operations, ESKOM plays an important strategic role in the South African economy not the least of which is the re-channelling of precious water resources from the Tugela to the Vaal system to help meet Gauteng's growing industrial and domestic water needs.
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