Abstract: The teachings herein include methods for operating a low- or medium-voltage power supply network including lines and a plurality of systems connected thereto. The method may include: providing GIS data with geographic location information relating to the power supply network; producing a branch model of the lines on the basis of the GIS data, including determining a starting probability for connections; providing system data characterizing at least one system; producing a prior model of the network by combining the branch model with the system data, including determining a starting probability for the system; generating an input state describing a possible state of the power supply network described by the prior model; carrying out a load flow simulation calculating a state variable on the basis of the input state; determining a state model of the power supply network on the basis of the state variable; and operating the power supply network based on the state model.