Load management through the utilisation of VSDs on water transfer schemes

South Africa is a water scarce country and due to this, large water transfer schemes were built to supply major parts of the country with raw and potable water. These water transfer schemes are high energy consumers due to the large pumps utilised for distributing water over great distances against significant static heads. With the present electricity situation in the country, Eskom invested in, among others, Demand-Side Management (DSM) interventions to ease the load on the electrical grid during peak hours. A transfer scheme's pump station that utilises Variable Speed Drive (VSD) technology for pump control was identified for a possible load management intervention. To develop an optimised control philosophy that utilises the VSD technology, tests were conducted on the pump station. Data gathered from these tests was used for the verification of a simulation model built to verify the proposed optimised control philosophy. After the proposed strategy was simulated and optimised, control and maintenance constraints limited the implementation of the control philosophy. The simulation however, indicated that an annual electricity cost savings of approximately R 3.3 million can be achieved. Due to the constraints, it was not possible to implement the load management initiative for a significant part of 2016. During periods when the pump station was operating at a reduced capacity, a 2.29 MW evening peak load reduction was achieved. This equates to a daily cost saving of R10 000 during the winter high demand season.