Method for determining state values for describing operating states in an energy supply network, which comprises a subnetwork having electrical loads and/or electrical sources, wherein - a decentralized control device is associated with the subnetwork and comprises a state estimation device by means of which state values that specify voltages at nodes of the subnetwork and/or an electric current on line sections of the subnetwork are estimated by using input signals supplied by the state estimation device; - the state estimation device comprises an artificial mathematical system, which is trained in such a way that it determines the state values by using the input signals, wherein input signals that specify an environmental state present in the region of the subnetwork are fed to the state estimation device; and - the decentralized control device comprises an evaluation device by means of which the state values are checked to determine whether they indicate an impermissible operating state of the subnetwork; characterized in that - in order to train the artificial mathematical system, on the one hand historical input signals and on the other hand such voltages at nodes of the subnetwork and/or electric currents on line sections of the subnetwork associated in terms of time with the historical input signals that have been detected directly using measurement devices installed at the respective nodes and/or line sections are used directly as state values, wherein the state values for this purpose are obtained from an archive system in which they have been stored after their measurement together with a piece of time information that specifies the time of their measurement; and in that - the evaluation device actuates controllable transformers and/or switches capacitor batteries on or off when an impermissible operating state is identified. - a decentralized control device is associated with the subnetwork and comprises a state estimation device by means of which state values that specify voltages at nodes of the subnetwork and/or an electric current on line sections of the subnetwork are estimated by using input signals supplied by the state estimation device; - the state estimation device comprises an artificial mathematical system, which is trained in such a way that it determines the state values by using the input signals, wherein input signals that specify an environmental state present in the region of the subnetwork are fed to the state estimation device; and - the decentralized control device comprises an evaluation device by means of which the state values are checked to determine whether they indicate an impermissible operating state of the subnetwork; characterized in that - in order to train the artificial mathematical system, on the one hand historical input signals and on the other hand such voltages at nodes of the subnetwork and/or electric currents on line sections of the subnetwork associated in terms of time with the historical input signals that have been detected directly using measurement devices installed at the respective nodes and/or line sections are used directly as state values, wherein the state values for this purpose are obtained from an archive system in which they have been stored after their measurement together with a piece of time information that specifies the time of their measurement; and in that - the evaluation device actuates controllable transformers and/or switches capacitor batteries on or off when an impermissible operating state is identified.