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| Illustration of offset in simple control algorithm |
A sophisticated mathematical algorithm on i2O's server is used to automatically generate and update the control parameters.
When the system is first installed, P2 is set to a safe fixed level (similar to the level it would have been set to if the PRV outlet pressure had been fixed).
On a scheduled basis, flow and pressure data from the controller and pressure data from the P3 sensor is uploaded to the server. After each upload, the server processes the data through the control algorithm which incrementally learns the head-loss characteristics of the DMA with increasing confidence.
When the algorithm gains sufficient confidence to commence optimisation, it generates a control parameter file. The next time that the controller communicates with the server, the control parameter file is downloaded to the controller. The controller then begins to use the control parameters to control P2. As these first control parameters are only based on a few days worth of data, P2 cannot be determined with high confidence. The algorithm therefore uses a large offset (margin of security) when setting P2. As each day passes, the server has more data and can therefore update and improve the control algorithm. This means that P3 begins to track P3ref more closely, lowering the average pressure in the network and steadily increasing the leakage saving. The algorithm may continue to improve even after a period of several years as longer term factors start to take effect, such as the time of year.
The control parameters are usually calculated so that the probability that P3 is above P3ref is 99.5% for any one 15 minute logged period.
If there are changes in the DMA, such as new houses or a factory closure, the control algorithm automatically adapts to the new demand pattern. A sudden change to the data caused by, for example, a large burst or boundary valve being opened would trigger an alarm and would not lead to a change in the control algorithm.