Reasons for deviations from the targets
The increased growth in demand over recent years, combined with
limited operational capacity, has resulted in a signiFIcant increase
in the production required from existing power stations. In order
to deliver on the continued demand, this increased production
has, in many instances, led to plant components being stressed
beyond their design operating parameters. This increased level
of usage, combined with exceptionally wet conditions in January
and February 2008, contributed signiFIcantly to a culmination of
conditions that resulted in forced capacity losses.
Benchmarking Generation’s performance
The increased pressure on the available power stations highlighted
the need to determine whether or not the existing coal-FIred
stations are performing at world-class levels. A benchmark study
of coal-FIred plant in Eskom and plants in international databases
was conducted over the period 1998 to 2006. Results show that
over a period of nine years, Eskom generating plant has performed
consistently and markedly better than their international
counterparts. The only point of caution is that the Eskom UCF
(availability) showed a signiFIcant drop in 2007.
Despite the decline in performance over the past two years, our
coal-fired plant performance continues to be among the best in
the world.
Generation technical recovery plan
Generation launched the UCLF (unplanned capability loss factor)
recovery action in February 2008. The aim is to stabilise power
station performance to an acceptable level by winter 2008, and
a predictable and sustainable power supply by the end of 2008.
More recently, the Minister of Public Enterprises indicated that
Eskom should restrict the total level of forced outages to within
2 500MW (2 000MW from UCLF and 500MW from OCLF).
This relates to an annual average UCLF performance of 5,1%
across the system.
Eskom power stations have been performing well when compared
to international practice.
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Condition monitoring |
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Any piece of equipment ages with time and use. As
equipment ages, it is more prone to breakdown and failure,
which is obviously not desirable. If the breakdown modes of
the equipment are well understood, there are certain signals
and events that can be used to pro-actively determine when
the plant is close to failure. An analogy of this is the use of
cholesterol measurements to give early warning of heart
disease. Condition monitoring is the process of monitoring
a parameter, or number of parameters, for equipment and
to then use this information to indicate the condition or
“health” of that item. Condition-monitoring information is
used to identify a significant change that points to a possible
failure which allows Eskom to take pro-active, preventative
maintenance steps to prevent a breakdown. |
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The UCLF recovery strategy is therefore focused on addressing
a multitude of factors, both skills and plant related. The following
plant focus areas have been identified within which these issues
are being addressed:
- Coal plant (focus on wet coal handling)
- Boiler plant (focus on boiler tube failures)
- Generator and other electrical systems
- Turbine and related plant
- Ash removal systems
The current plant performance recovery initiative will extend
over many years. In order to minimise negative customer impact,
only the most critical issues can be dealt with in the short term,
while many others will be blended into the normal maintenance
cycle over years to come. Any limitation on us achieving the
minimum level of required maintenance will provide a severe
setback to the recovery programme and lead to unpredictable
plant performance. For now, the outlook for unplanned outages remains high, although these are being managed on an ongoing
basis to reduce customer impact. The overall level will only
show sustainable improvement as the above interventions show
significant progress.
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Click here for more details on the UCLF recovery strategy. |
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