Water Journal : Water Journal November 2013
WATER NOVEMBER 2013 48 Feature Article ABSTRACT This article describes the system modelling approach used in the design and commissioning of a control system for Ravenswood Pump Station. The control system is a state-of-the-art system that allows a remote operator in the Water Corporation's Operations Centre to manage water transfers to Perth in the most ef cient way. The control system automatically adjusts the speed of the pumps when system conditions change, to maintain the desired transfer rates. A purpose-built model of the water transfer system was used to simulate the behaviour of the control system in response to changes in the pipeline system. In the early design stages, the model was used to evaluate a number of design options for the control system. One option was selected and developed further in the following stages of design. The model played a further role during the commissioning of the Southern Seawater Desalination Plant Integration Works by simulating commissioning tests before conducting the tests on the live system. This greatly reduced the risks associated with the real-life testing. INTRODUCTION Stage 1 of Perth's second desalination plant, the Southern Seawater Desalination Plant (SSDP), has recently been constructed and commissioned. Substantial upgrades to the existing water transfer system, the Southern System, were required to deliver an additional 166 ML/d into Perth's Integrated Water Supply Scheme (IWSS) (IPB, 2009). In order to maximise transfers of desalinated water, as well as water from existing sources, a new pump station has been constructed in Ravenswood, approximately two-thirds of the way along a major existing transfer main. The new 12MW Ravenswood Pump Station is located at the intersection of two major pipelines and consists of two separate banks of variable speed pumps that can simultaneously deliver water in two separate directions. The two banks of variable speed pumps have been equipped with a control system to provide a remote operator with the means to control the ow rate of each bank via the Supervisory Control and Data Acquisition (SCADA) system. The control system is installed locally and controls the ow rates of the banks using closed loop feedback control. This allows the remote operator in the Water Corporation's Operations Centre to manage water transfers to Perth in the most ef cient way. The introduction of feedback control in pump stations gives rise to complex dynamic behaviour, because the control systems are continuously adjusting the speed of the pumps in response to changing conditions in the pipeline system. Since the application of feedback control of ow rates and pressures in water transfer systems is a relatively new development, control system modelling was used from the early design stages to inform and guide the design process for Ravenswood Pump Station's control system. SOUTHERN SYSTEM The Southern System is supplied from the Stirling Dam, the new Southern Seawater Desalination Plant via Harvey Summit Tank and from Samson Pipehead (Figure 1). The major artery of the system -- the Stirling Trunk Main -- connects Stirling Dam in the south with Tamworth Reservoir in the north and is a DN1400 MSCL pipeline with a length of 108km. CONTROL SYSTEM MODELLING FOR THE INTEGRATION OF PERTH'S SECOND DESALINATION PLANT Eelko Van Der Vaart and Faris Hernich discuss the value of control system modelling from early design through to commissioning. Figure 1. The Southern System.
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