The aim of Advanced Pressure Management is to keep P3 as stable as possible and just above P3ref. As the head loss in the DMA between the PRV and the critical point changes with changing demand patterns, P2 must be continually adjusted in order to achieve this.
Controllers used to date for Pressure Management have tended to use a pre-determined fixed relationship that gives a value for P2 depending on the flow. There are a number of drawbacks to this: the table has to be entered manually following a logging exercise; the controller does not take into account demand patterns that vary depending on the day of the week or time of year; neither does it take into account changes to the demand pattern in the DMA caused by seasonal effects, or a factory closing or new house building. Because of these uncertainties, it is usual to enter a very conservative table. This limits the opportunity to optimise pressures and hence maximise the water that can be saved.
The i2O system overcomes these problems by using a sophisticated self-learning algorithm in an Open Loop configuration. The algorithm automatically learns the head loss characteristic of the DMA and downloads optimised control parameters to the controller. In this way they are always optimised and save the maximum amount of water.
The controller communicates with the i2O server on a scheduled basis using the GSM network. During each communication, the latest pressure and flow data are uploaded to the server and updated control parameters are downloaded to the controller.
A sensor at the critical point (P3 sensor) also sends the latest pressure data to the i2O server over the GSM network. The P3 data is required to update the control algorithm and to monitor the performance of the system. The P3 sensor also sends an alarm if P3 falls below P3ref.
A further weakness in existing Pressure Management systems is the method of adjusting P2. This is done by using hydraulic or pneumatic actuators which exert a variable force on the conventional pilot valve spring. The pneumatic version of this system has a short battery life, limited range and is vulnerable to valve chamber flooding. The hydraulic system has a high power requirement, limited pressure control range and relies on solenoids which can be unreliable.
i2O has overcome these issues by developing the Advanced Pilot Valve (APV). This has been designed to provide smooth and reliable control of the P2 pressure using minimal power. The APV works on the same principle as a conventional pilot valve with an innovative Patent Applied For feature.
The i2O server plays a number of vital roles: it receives and stores data; it processes data through the control algorithms on a scheduled basis and downloads optimised control parameters to the controller; it handles alarms and provides reports both to the water company and to i2O.
Where required, a sensor can also be installed at the AZP point (the P4 sensor). This can measure the AZP pressure (P4) and send the data back on a scheduled basis to the i2O server. Where a P4 sensor is not installed, P4 can be estimated or calculated.
In some DMAs, the critical point may be at different locations depending on the DMA flow characteristics. In this case, a P3 sensor is installed at each critical point. The control algorithm works in the same way, and learns to maintain P3 above P3ref at both critical points.