Abstract: A differential protection method generates a fault signal which indicates that a fault has occurred at an electrical component of an energy supply network. Differential current values and stabilization values are formed from current measurement values at different measurement points of the component and the fault signal is generated if a measured value pair, formed from one of the differential current values and the respectively associated stabilization value, lies in a predetermined tripping range. The stabilization current values in a predetermined observation period are compared with the respective associated differential current values and, based on the comparison, a fault indicator is formed, which indicates whether the proportion of the differential current values or the proportion of the stabilization current values is greater. The generation of the fault signal is blocked if the fault indicator indicates a greater proportion of the stabilization current values.

Abstract: A method generates a fault signal that displays whether an internal transformer fault is present. According to the method, a differential current signal that indicates the difference between the primary current and the secondary current of the transformer, taking into consideration the conversion ratio of the transformer, is ascertained. A plurality of different criteria signals are generated using the differential current signal. At least two individual fuzzy matching functions are assigned to each criteria signal. The fuzzy matching functions are analyzed, thereby generating the fault signal.

Abstract: A current differential protection arrangement for an electric power supply unit with a measured value pre-processing device and an analysis device that checks on the basis of a predefined dependence of a differential current on a stabilizing current (response characteristic curve) to determine whether the differential and stabilizing current values thus formed are in a blocking range or a triggering range, where an additional stabilization range is present in the blocking range. To avoid fixed-time blocking after an external fault with transformer saturation with such a protection arrangement, the analysis device in a stabilizing circuit contains a testing arrangement which checks the current values thus formed to determine whether they describe a point in the additional stabilization range. If this is the case, a blocking signal is produced, which activates the blocking device downstream from the testing arrangement.

Abstract: A differential current protective device for a transformer arranged in a multi-phase power supply system and having at least one star-connected winding arrangement with a grounded star point. The differential current protective device receives currents proportional to the system currents via current transformers provided on the high and low voltage sides of the transformer. A computing circuit of the protective device determines a differential phase-related current from the currents measured, taking into account a current parameter that corresponds to the zero system current based on the phase and whose intensity is monitored. The differential current protective device includes an auxiliary current transformer having its primary winding in the connection between the star point and ground. The computing circuit processes the secondary current of the auxiliary current transformer as the current parameter corresponding to the zero system current.