Review of National Power System and 2008 Winter Prognosis. Presentation to Public Enterprises Portfolio Committee 20 th May 2008. Contents. Review of recent history Need for a reserve margin Evolution of the reserve margin Generation fleet performance Winter 2007 Review
Presentation to Public Enterprises Portfolio Committee
20th May 2008
The Electrical Power System is considered the most complex system around. It is a mix of electrical, communication, mechanical, civil, information and management systems.
A comprehensive list of things that could go wrong and the possible impact on other risks cannot be modelled. The ability to continuously visualise the current risk status is incredibly difficult and stressful.
The impact of failures can be significant to catastrophic (i.e. blackout). There are various global examples of where this has occurred.
Buffers in the system such as operating reserves, stockpile days, transmission and distribution network redundancy and resources allow the System Operator to deal with multiple events in real time while enabling sustainable medium to long term performance
By continuously operating “on the edge”, you will not need many things to go wrong before you test your defence systems. You do not want to test your defence systems too often as the increased exposure will increase the likelihood of something going wrong and these barriers failing.
South Africa’s ability to deal with a nationwide black out is untested and we cannnot rely on our neighbours to assist.
Operating Reserve Margin margin and other buffers?
Generation Capacity Net Reserve MarginThere are two key components to the reserve margin
Reserve margin build up
KEMA, in a study for NEMCO, indicated that a reserve level of 4 - 6% should be maintained for system security, if necessary, by curtailing customer load in some manner
Operating Reserve Margin
Short term economic growth
Reserve margin allows space for growth
Generation performance variation
High range due to varying capabilities of different systems
Weather variations as seen during cold spells starting in May
Total Reserve margin
Total Reserve margin
Net Reserve Margin (%)
Note: The increase in reserve margin in 2005 was as a result of low peak demand for that year. Peak demand for these years was as follows: 2004 – 34.20 GW; 2005 – 33.46 GW; 2006 – 35.31 GW. ; 2007 – 37.10 GW. This low demand for 2005 was driven by the commodity market and a mild winter
Usage of EL1
Usage of key types of emergency reserve
Usage of interruptible
2007-8 to Dec 31
Unplanned system losses per day – Last 3 years (MW)
Unplanned system losses per day – Last 4 months (MW)
Days within daily limit of 2 500 MW of UCLF:
- Past 3 years = 68%
- Past 4 months = 44%
- April alone = 87%
A key driver of the figures in January and February was availability and quality of coal
Supply Side Initiatives
Demand Side initiatives
Planning and Expansion
12 emergency reserves rises dramatically
Assumptions used for actual classification of a week
20 emergency reserves rises dramatically
We are seeing evidence of increased energy savings from municipalities and Eskom is optimistic that further reductions to reach our 10% savings target are possible.
A task team of senior Eskom executives and top officials of municipalities from around South Africa is to meet early next week to discuss the way forward in driving further energy savings.
Recent savings, particularly from industry, have shown that it should be possible to achieve this objective sustainably through a concerted and committed effort by all of us. This is the spirit of Eskom’s engagement with municipalities and we would hope that it will not be necessary to reinstate scheduled load shedding.
However, should the national grid come under unexpected pressure, there may be occasions where brief periods of load shedding could be required.
Extract from Media Release – 30 April 2008
General trend of reductions against forecast of 2 to 9%. Average of close to 5% in April improving from 3% in March.
Actual Energy demand tracking Scenario B and will need to be monitored against Scenario A and the Medium Term forecast
Original forecast adjusted for a Cold Winter
Original forecast less 2000 MW Reduction
Original forecast less 3000 MW Reduction
Includes Scenario C as well as a warmer winter
General trend of maximum demand reductions against forecast of 2 to 11%. Average of close to 7% in April.
29 emergency reserves rises dramatically