The invention relates to a diagnostic method for multiple-stage excess voltage protection apparatuses that include at least one gas discharge distance between an input and a reference potential as a first stage, at least one diode path between an output and the reference potential as a second stage, and at least one decoupling inductance interposed between the input and the output. The diagnostic method is characterized in that a secondary voltage applied to a secondary inductance, which is actively connected, inductively, to the decoupling inductance, is measured and evaluated with a view to excess voltage events in the excess voltage protection apparatus. The invention also relates to a two-stage excess voltage protection apparatus.
