by Pierre Potgieter, EE Publishers
This article looks at the method behind South Africa's 2040 strategic electricity grid design plan, to show how long-term planning creates efficiencies that bring down energy costs for both energy users and producers, and how GIS is used to achieve this.
The electricity transmission grid, a network of servitudes that span across the entire country, is the vein system of the South African economy. These lines, 132 kV and higher, carry some 40 GW of electricity from where it is generated to various distribution points, which connect end-users to the grid on a local level.
As transmission planning is essentially a transport problem (getting energy from the generation source/supply to the client/demand centre), it has a spatial component, which makes it very suitable to model and plan in a geographic information system (GIS).
Background
The idea of a well-planned network is to create a smooth implementation process. The actual construction process of transmission lines may only take three years, but the mismatch in timing between the preparatory process and construction makes planning important. Planning allows for early land acquisitions and EIAs, which are usually the hardest part in the implementation process and can take five to eight years to accomplish for a single property.
In short, South Africa's strategic grid plan with its 2040 focus is informed by the Department of Energy's energy plan, the Integrated Resource Plan (IRP). The IRP drives new generation capacity development, and in turn shapes shorter-term policies such as the 10-year Transmission Development Plan (the TDP, which presents transmission corridor requirements), the Investment Plan and the Strategic Grid Plan (SGP).
The Department of Energy (DoE) dictates a desired energy profile for the country i.e. the percentage renewables, gas, coal and other generation. The grid planners aim to create a network wide enough to "unlock" these natural sources for generation, with the ability to feed electricity to demand centres. Part of the planning is to identify critical power corridors and constraints in the transmission network.
As in other parts of the world, a central co-ordinating body plans the grid since the design process requires an overview of the entire system. In South Africa, Eskom does this. Eskom has not had a generation monopoly since 1993, and has to take independent power producers (IPPs) into account in the grid design plan. Grid design also has to comply with international standards, and locally with the Grid Code which is regulated by the National Energy Regulator of South Africa (NERSA), with one of the licence conditions requiring open access to all.
Grid design is a catch-twenty-two situation: power will flow on the existing network, but this network should accommodate future configurations. Incremental planning does not work as load centres and generation, which dictate the natural flow of electricity, shift geographically over time. This makes incremental planning constantly corrective and potentially inefficient - which increases costs in the process. Furthermore, the combinations and types of generation, as well as their price, might change in the future, making a flexible and robust grid design essential... (
more)
