Eskom separation plan will mean sharply higher costs and massive complications

Date: Mar 29, 2019

Power system planners would work in isolation and the result would be a chronic shortage of generating capacity in the medium and long term

Separating generation and transmission is another disastrously bad policy decision that should be reversed before any further damage is inflicted on Eskom and additional unnecessary costs  are imposed on the South African electricity consumer.

Understanding why this is the case requires some knowledge of how a power supply system operates and how the costs of managing the system are minimised.

Turbines driving electricity generators produce power within a range that varies between 100% and about 60% of rated capacity. In general, their most efficient operating point is about 80% of rated capacity.

The job of men and women operating a power system is to balance supply and demand to ensure that all the generators connected to the system operate within this range at all times. They do this by monitoring the system frequency. This must be held as closely as possible to 50 cycles per second, implying that the rotation of all the turbines must be synchronised and held at 3,000rpm.

When turbines are overloaded they slow down. When they are too lightly loaded they speed up. As long as all the machines are supplying power within their operating ranges the speed of rotation is held within narrow, pre-specified, limits by electro-mechanical devices and the system operators take no action.

An imbalance between supply and demand causes the system frequency to fall below or drift above its limits. When this happens, or when the operators anticipate it will happen in the near future, generating sets held in reserve must be activated or one or more generators supplying the system at that time need to be disconnected. Now the operators have to decide which generators should be brought into operation or which removed from the system.

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