Strengthening of the Transmission Network to the Cape Province
A strategic viewpoint
Background briefing document
GENERAL OVERVIEW
Eskom is an independent, self-financing utility company that is managed on business principles for the benefit of customers. It is a separate legal entity and is funded entirely from borrowing and accumulated reserves. It operates under the Eskom Act of 1987 and the Electricity Act of 1987. Policies are determined by the Electricity Council, which represents customers, organized labour and the government. The Management Board, appointed by the Council, is the executive body responsible for the day-to-day running of Eskom.
Transmission is a ring-fenced business within Eskom, basically operating independent from its Generation and Distribution counterparts. In describing the role of the National Grid it could be seen that Eskom Transmission's duty is to firstly maintain the grid in terms of balancing available supply to actual demand. Secondly Transmission's duty is to provide reliable power to its customers. Within these duties, legal requirements need to be taken into account.
In order to perform these duties, the strategic planning process could not totally be independent. Future generation options as proposed by Generation will always be included; this will even include independent power producers' options. On the Distribution side, Demand Side Management (DSM) is also a process always considered (described within the planning process).
The main criterion for strategic planning is based on one of four criteria as described within the planning process (Justification).
Overview of the system planning process
Ø Need Identification
The need for any planning process could arise from one of many triggers, including a Generation, Distribution or customer requirement; new load, degrading plant performance, ageing plant, high operating and maintenance cost, recommendation from an audit, statutory requirement, Quality of supply issues, normal load growth, Network reliability enhancement or a.
Ø Evaluation of Alternatives
All possible alternatives available to fulfil the need are listed and eventually evaluated. The possible alternatives include:
- The "Do Nothing" option as base case
- Demand Side Management (DSM) options. DSM considers the actual time of utilization of power is very important in DSM. One example of DSM is the process of spreading the time when customers require energy. An example is to negotiate with large customers to rather operate at full output outside of the peak demand times than within (similar to use a washing machine after using the stove or kettle. This is normally between 9.00 to 11.00 in the mornings and 19.00 to 21.00 in the evening. Another DSM option would include the moving of load from a specific substation to another by changing the operation of the substation (similar to plug your kettle into a socket in another room when other apparatus are used in the kitchen). Another example is ripple control, switching off geysers during peak time, since most residential sources require most power during peak load times.
- Impact of future generation (Eskom Generation as well as independent producers' options)
- Performing of reverse engineering studies to determine how much can be spent on solutions
- Technical reinforcement solutions (keep available and latest technologies e.g. FACTS devices in mind) such as new lines, series compensation, etc.
The Economic Evaluation is the means by which the “the least cost” option is selected from a variety of “do something” options.
Ø Economic Justification
This is the process of determining whether the chosen option meets the Capital Investment Criteria and costs less than the “do nothing” option. The various criteria could be one or more of the following:
- Statutory requirement (including NER, environmental legislation, OSH Act)
- Operating Cost Reduction (to reduce cost of maintenance and operation of existing plant)
- Positive NPV (typical for large new loads, e.g. Saldanha Steel, Hillside, Coega, etc)
- Reliability Enhancement (optimising total cost of electricity supply, providing more reliable network, cater for normal load growth). An investment is valid if the cost reduction to the customer as a result of the improvement exceeds the cost to provide the improvement.
Ø Sensitivity analysis
This is done to verify the effect of generation cost, capital expenditure, inflation rate, load growth and tariff changes.
Ø Execution of the project
A project can only be executed after it is economically justified and approved by the specific board.
Ø Commissioning and Operation
Commissioning takes place after the new infrastructure is in place and ready for operation.
Ø Review
Every project is reviewed after a sensible period of time.
Please note that the effect of AIDS has not specifically been taken into account during any strategic planning process.
To summarize, the planning of the reinforcement and maintenance of the National Grid is based on current and projected load demands, as well as current and confirmed future generation sources. The uncertainty in demand projections requires that this be reviewed annually. However due to the length of time required to plan a specific high voltage line, it is necessary to initiate the route planning process between 5 to 10 years prior to the anticipated construction of the line. It is recognized that in this period a number of strategic factors may change:
- Demand may grow more rapidly or more slowly, resulting in the need to advance or delay construction of the line.
- Alternative generation sources may become available requiring a review of the need for the proposed line.
Therefore it is always necessary to review the need for the line prior to construction. This is inherent in the planning process, as Eskom Transmission will not construct a line unless it is economically viable, justified and approved by the Management Board and the Electricity Council. The planning process always includes the environmental process as described in the following section.
Environmental decision making process
Depending on the magnitude of each of the projects envisaged, Environmental Impact Studies would be conducted taking into account the potential effects on:
Ø Endangered / threatened fauna and flora species
Ø Agricultural land use
Ø Recreation facilities
Ø Tourist potential
Ø Cultural resources
Ø Archaeology
Ø Visual impact, etc.
Interested and affected parties will be invited to comment on each project as the investigation proceeds further and will have the opportunity to review the studies. Should the projects go ahead, every effort will be made to mitigate any negative social, economic or biophysical impacts.
Once the EIS on a project has been carried out and publicly reviewed, a final decision will be made on the preferred route. Servitudes for the construction of the proposed power line will then be obtained through negotiations between Eskom and the individual landowners. Based on the outcome of these negotiations, the final alignment of the proposed line will be surveyed and an Environmental Impact Management Plan developed (EIMP). This EIMP ensures that care is taken of the environment during and after the construction phase of a project.
To summarize, the Environmental Impact Studies (EIS's), following the "Integrated Environmental Management" procedure as advocated by the Department of Environmental Affairs and Tourism, will be done for each project ensuring public participation and least impact on the environment. This will typically be followed by negotiations with the affected landowners and Environmental Impact Management Plans (EIMP's) that will precede construction.
BACKGROUND TO THE CAPE TRANSMISSION NETWORK
South Africa has an energy-intensive economy. Eskom has undertaken to reduce the real price of electricity for industry so that South African producers and manufacturers can remain competitive on world markets, create jobs and generate wealth. Electrification of houses is an ongoing process. These obligations and undertakings are rapidly increasing the pressure on Eskom's existing power generating and transmission capacity.
Electricity can not be stored. The service is therefore generated and delivered over long distances at the very instant it is required. In South Africa, thousands of kilometres of high voltage lines transmit power to major substations where the voltage is down rated for distribution to industry, businesses, homes and farms all over the country. The main source of power to the Cape Province is the generation pool of power stations up in Mpumalanga. Koeberg and Palmiet can provide some of the power required, but not all of it
The transmission network between Alpha and Koeberg forms the backbone of the Cape Network. Although it allows for the distribution of electricity in both directions, it has developed as a result of the fact that most of the country's power is generated in Mpumalanga. Koeberg can supply up to 1840MW of power locally, but might not always be available. Similarly some of the 765kV or 400kV lines may have faults on it or be out for maintenance purposes or switched out because of veld fires, which impact on the reliability of the electricity to all customers, due to limitations in line capacities. This is why the Transmission network in the Cape Province is planned holistically to provide adequate and reliable electricity to all customers.
The next sections will provide an overview of past and planned developments in respect of the transmission network for the Cape region.
History of the Cape Transmission System
In 1987, Eskom’s very first 765 kV transmission line between Alpha and Beta Substations was commissioned, with the second line converted to 765 kV in 1991. The existing Alpha-Beta two-line 765 kV system plays an important role to feed electricity from the centralised generation pool in the Mpumalanga Province, via Gauteng and the Free State, to Transmission Substations, south of Beta Substation. In 1991, the 765 kV network was extended south, from Beta Substation to Hydra Substation with the construction of the Beta-Hydra 1st 765 kV line. The line was constructed for 765 kV operation because it formed part of the long-term plan to overlay the Cape 400 kV network with a two-line 765 kV network.
During 1996 and 1997 a 3rd 400 kV line was commissioned between Droërivier and Hydra 400 kV Substations. (This line was not built at 765kV level due to unknown circumstances).
The Cape Transmission System also serves to export power to Namibia for a large portion of the year. The first 400 kV inter-connector between South Africa and Namibia was commissioned in 1999. Indications are that Namibia will continue to rely on energy import from South Africa to meet the bulk of their energy requirements in the short to medium term. The loading on the Cape Transmission System is therefore likely to increase as a result of increased energy demand by NamPower.
A step increase in load demand realised when the new Saldanha Steel smelter started production in 1998.
The existing Cape Network and its future requirements
The Cape Transmission System, south of Alpha Substation supplies electricity consumers in the Southern Cape, West Coast, Peninsula, Namaqualand, Karoo, East London, Port Elizabeth, Kimberley and Bloemfontein load centres as shown in Figure 1. These load centres had a combined 2001 peak load demand of 5000 MW, utilized per area as indicated.
The Cape 400kV Transmission System, south of Hydra Substation supplies customer loads in the Southern Cape, West Coast, Peninsula and Namaqualand load centres as shown in Figure 1. These four load centres had a combined 2001 peak load demand of 3000 MW, utilized per area as indicated in Figure 1. This peak load does not include the supply to Namibia, which can amount to 250 MW.
Local generation in the Cape region is limited to the Koeberg Nuclear Power Station (1840MW), the Palmiet Pumped Storage scheme 400MW (near Grabouw), Gariep Hydro scheme 360MW (close to Colesberg) and Van der Kloof Hydro scheme 240MW (near Petrusville). This leaves around 2160MW (5000MW - 2840MW) of load that presently needs to be fed from sources in Mpumalanga during system healthy conditions. For the time being Koeberg is still fine, but will in future (unknown at this stage) reach the end of its lifetime. This also needs to be taken into account when developing the network.
The forecasted average load growth, based on historical data, is around 2% per annum. The steady growth in electricity demand is expected to continue, as a result of electrification, increased housing densities and commercial development.
FIGURE 1
Each Koeberg unit is normally out of service for a reasonably lengthy duration during scheduled nuclear re-fueling outages. When one Koeberg unit is not available, the power generated drops to a maximum of 920MW and hence increase the demand from Mpumalanga to 3080MW (2160 MW+920MW). The risk of the other Koeberg unit faulting or simultaneous line faults will increase the power flow substantially through the remaining lines, which eventually could lead to lines or series capacitors being overloaded. Presently the maximum transfer into Hydra substation is limited to 3600MW, because of the available line capacities. This means that if we loose the remaining Koeberg unit, we will be forced to shed at least 400MW of load.
Even when both Koeberg units are available situations occur when line maintenance is scheduled on a specific line and another parallel line has a fault on it, again leaving the system unreliable. In some cases load needs to be switched out to keep some load provided with power, but preventing the loss of the entire load in the Cape Region. These conditions together with the increase in load demand forces Transmission to develop and extend the existing Transmission network to provide adequate and reliable electricity to the customers. If Transmission would do nothing about the situation, the amount of energy that can not be delivered during these conditions increase each year. This can be maintained if only small amounts of load need to be shed, but unfortunately the demand is growing each year and the expected energy that is at risk is growing.
The Cape Transmission System plays an important role to supply electricity consumers in the Cape load centres during these and other forced outages of local generation plant. Therefore the need exist to improve the reliability and ultimately the capacity to supply the required demand.
Proposed 765 kV over-lay scheme