Abstract: A protection device for monitoring an energy supply grid has a measured value acquisition device for acquiring measured values which indicate an electrical state of the energy supply grid, and an evaluation device which is connected to the measured value acquisition device and is configured to carry out a plurality of protection functions and, as a result, to make a decision as to whether the energy supply grid is in a permissible or impermissible operating state. Here, the evaluation device be designed entirely in the form of a single neural network with an input neuron layer that receives the measured values and/or values derived therefrom, intermediate neuron layers, and an output neuron layer which outputs a classification of operating states of the energy supply grid. The neural network for classifying the operating states is trained to carry out all protection functions together.