Stromdifferentialschutzanordnung für einen Transformator

摘要

The invention relates to a differential current protective device for a stransformer in a multi-phase power supply system having at least one star winding arrangement with an earthed star point. Currents proportional to the mains currents are applied to the differential current protective device via current converters allocated to the transformer's high and low-voltage sides and the device has a computer circuit in which a phase-related current differential is formed taking account of a current corresponding to the zero system current and the value of said differential is monitored. In order to design such a differential current protective device so that it is also as sensitive as possible to the detection of a single-pole internal fault, according to the invention the differential current protective device (SD) comprises an auxiliary current converter (Wh) with its primary winding (Whp) in the connection between the star point (S) and earth; the computer circuit processes the secondary current from the auxiliary current converter (Wh) as that of the current corresponding to the zero system current.