Automatic Water-Level Control in South Africa

The principle of proportional, integral, and derivative sensing constitutes the theme of this paper. A study was made of the different types of control elements involved. This resulted in the selection of a PID-controller as the most suitable. This controller was designed and installed and three different methods were employed for determining the optimum parameter settings. These comprise direct calculation, analog computer simulation, and actual practical tests on site. The final parameter settings resulted in efficient and effective automatic water-level control to within a spectrum of 1.18 in.-1.57 in. (3cm-4cm) at full supply level at incoming flows and floods ranging from 285 cfs-25,000 cfs (8m³/s-700m³/s). These results were due to the mechanism actually reacting to a water-level change of as small as 1 mm.