Method for identifying at least one diagnosis variable, which indicates an ageing state of an operating means (11, 31) in an electrical energy supply network, in which - first measurement values of at least one measurement variable are detected at a first measuring point of the operating means (11, 31); - second measurement values of the at least one measurement variable are detected at a second measuring point of the operating means (11, 31); and - the at least one diagnosis variable is identified using respective simultaneously detected first and second measurement values; characterized in that - the first and second measurement values are detected in a time-controlled manner in such a way that a signal of the at least one measurement variable is sampled at a prescribed sampling rate at set times and over a set measurement duration so as to generate time profiles of the first and second measurement values, wherein - the first and the second measuring point (12a, 12b) of the operating means are arranged at a physical distance from one another; and - the first measurement values are detected by means of a first measuring device and the second measurement values are detected by means of a second measuring device, - the set times and measurement durations for detecting the measurement values of the first and the second measurement values are set in terms of time in such a way that the measurement values are detected simultaneously in a time-controlled manner at least over an overlap time range in the two measuring devices (13a, 13b); and wherein - the profiles of the first and second measurement values are stored and, by subsequent synchronization, respective simultaneously detected measurement value pairs of the at least one measurement variable are identified from the profiles. - first measurement values of at least one measurement variable are detected at a first measuring point of the operating means (11, 31); - second measurement values of the at least one measurement variable are detected at a second measuring point of the operating means (11, 31); and - the at least one diagnosis variable is identified using respective simultaneously detected first and second measurement values; - the first and second measurement values are detected in a time-controlled manner in such a way that a signal of the at least one measurement variable is sampled at a prescribed sampling rate at set times and over a set measurement duration so as to generate time profiles of the first and second measurement values, wherein - the first and the second measuring point (12a, 12b) of the operating means are arranged at a physical distance from one another; and - the first measurement values are detected by means of a first measuring device and the second measurement values are detected by means of a second measuring device, - the set times and measurement durations for detecting the measurement values of the first and the second measurement values are set in terms of time in such a way that the measurement values are detected simultaneously in a time-controlled manner at least over an overlap time range in the two measuring devices (13a, 13b); and wherein - the profiles of the first and second measurement values are stored and, by subsequent synchronization, respective simultaneously detected measurement value pairs of the at least one measurement variable are identified from the profiles.