Present-day systems for modeling and control of gas transport and distribution commonly offer the Leak Detection and Leak Localization as one of their features. The function is usually based on running comparison of calculated and measured values. Sensitivity of Leak Detection, accuracy of Leak Localization, and speed of setting the above information up depend on the number and accuracy of the meters, their distribution over the pipeline system, and the current mode of transport. General specification of the sensitivity, accuracy, and speed in dependence on the above relevant parameters is not viable. Nevertheless, from experience is known that the state of the art in Leak Detection and Localization does not satisfy the requirements. Therefore, a new method has been designed that employs the effect of State Finder. For the purpose of Leak Detection and Localization, the State Finder was modified in a special way. The use of State Finder suppresses the negative influence of the inevitable errors of meters and thus remarkably sensitizes the Leak Detection, significantly enhances the accuracy of Leak Localization and considerably shortens the time for setting the alert information up. The modified State Finder is triggered periodically in frame of the cyclic simulation. Effect of the new Leak Detection and Localization Method is analyzed and demonstrated by a series of experiments on factual trunk line where no compressor station has flow rate measurement.
Leak detection systems for gas networks can be divided into externally based system (acoustic, fiber optic sensing cables…) and internally based system (balancing method, pressure/flow monitoring…). Below described method, based on the State Finder properties, belongs to internally based methods but does not require flow rate measurements in compressor stations. The state of network is described by a complete set of values for all process variables, namely pressures and flow rates, for the entire network. Naturally, because of the perpetual transients in the network, the state changes continually. State Finder (State Reconstruction) is a tool known from Control Theory. Employing the measured values and the mathematical model of dynamic processes running within the technical system, the State Finder computes an estimate of the actual state of the system. The ability to find the state of given dynamic system, on the basis of a set of values measured over a time interval, is called observability. Consider all non by-passed compressor stations, control valves, and closed valves being removed from the network. This divides the network in separated sub-networks. If all supplies and off-takes are measured, set points of nonpipe elements are known, and at minimum one pressure measurement exists in each sub-network, the entire system is observable. The sub-network in which the pressure measurement is for a longer time not available is not observable; the errors in flow rate measurements result in uncertainty of the in-take/off-take balance of the sub-network. Without the information about pressure the State Finder is unable to compensate the drift of system balance.