Method for determining a reliability state of an electrical network , the electrical network comprising a plurality of interconnected electrical devices (T1, Util, JDB1, D1), the electrical network being modelled by a single-line representation, the method comprising the following steps: a) identifying an undesired event at a given location in the electrical network, the undesired event corresponding to a critical state of the electrical network resulting in partial or total, temporary or permanent unavailability of electrical power at the given location; b) traversing at least one subset comprising electrical devices of the plurality of electrical devices of the electrical network starting from the given location; c) identifying an electrical device of the subset of the electrical network traversed in step b); d) determining a list of events of concern that are associated with the identified electrical device and could result in the undesired event, the events of concern corresponding respectively to causes leading to a failure or malfunction for the identified electrical device and likely to result, alone or in combination, in the undesired event; e) determining a total unavailability value associated with the identified electrical device taking into account the unavailability rates and the repair times respectively associated with each event of concern in the list of events of concern; f) repeating steps b) to e), the method being interrupted once a predefined number, which is greater than or equal to two, of electrical protection devices have been traversed in the subset; and g) calculating a reliability state of the electrical network on the basis of the total unavailability values respectively associated with the traversed electrical devices. a) identifying an undesired event at a given location in the electrical network, the undesired event corresponding to a critical state of the electrical network resulting in partial or total, temporary or permanent unavailability of electrical power at the given location; b) traversing at least one subset comprising electrical devices of the plurality of electrical devices of the electrical network starting from the given location; c) identifying an electrical device of the subset of the electrical network traversed in step b); d) determining a list of events of concern that are associated with the identified electrical device and could result in the undesired event, the events of concern corresponding respectively to causes leading to a failure or malfunction for the identified electrical device and likely to result, alone or in combination, in the undesired event; e) determining a total unavailability value associated with the identified electrical device taking into account the unavailability rates and the repair times respectively associated with each event of concern in the list of events of concern; f) repeating steps b) to e), the method being interrupted once a predefined number, which is greater than or equal to two, of electrical protection devices have been traversed in the subset; and g) calculating a reliability state of the electrical network on the basis of the total unavailability values respectively associated with the traversed electrical devices. <EOS>