Hydraulic and economic analysis of real time control

The aim of this paper is to analyze the hydraulic and economic effectiveness of the real-Time control (RTC) of pressure reducing valves (PRVs), for the purpose of managing pressure to reduce leakage and pipe bursts. In their conventional use, a PRV automatically reduces a higher inlet pressure to a lower downstream set-point pressure (steady-state), regardless of changing flow rate or varying inlet pressure. In local RTC, instead, the set-point can be adjusted in real time to accommodate the variations in the water discharge though the valve. In detail, local RTC is performed thanks to a programmable logic controller (PLC), which can use the water discharge measurement received from an electromagnetic flowmeter in proximity to the valve, to calculate a new valve setting. The initial applications of the work will concern the extended period simulation of a pressure zone, in which the locally controlled PRVs is installed in the feed pipe that connects the source to the pressure zone. In this case study, nodal demands are reconstructed stochastically through the bottom-up approach and the relationship between downstream set-point pressure and water discharge through the device is derived in such a way as to meet users' pressure requirements at all nodes. The subsequent sections describe the assessment of the total cost of the controlled system, including the installation cost of the control device, the flow-dependent operation and maintenance (O&M) cost, and the pipe burst repair cost over the planning horizon. The total cost of the local RTC will be compared with that of three other scenarios: 1) no control, 2) conventional PRV and 3) remote RTC under various conditions of system size, demand pattern and leakage. The analysis shows that conventional PRV's are most appropriate for small pressure zones, with limited leakage and low-cost water while real time control is needed in larger zones, with high leakage and high-cost water.