Patent ID: 6313639
Filing Date: 2001-11-06
Classification: H02H

Abstract:
A method for identifying short circuits in low-voltage networks, the method which comprises:determining a first envelope and a second envelope for a plurality of locus curves of a current steepness as a function of a current in a low voltage network, the first and second envelopes including all switching angles, the first envelope being determined for a lower power factor, the second envelope being determined for an upper power factor;additionally determining a third envelope taking into account rated-current switching operations between the lower power factor and the upper power factor;forming a resultant envelope from a combination of the first, second, and third envelopes by overlaying the first, second, and third envelopes, the resultant envelope defining a tolerant locus curve criterion indicating a short circuit for values of at least one of the current steepness and the current outside the tolerant locus curve criterion, the tolerant locus curve criterion being independent of power factors and independent of an initial current; anddetecting at least one of an instantaneous current value and an instantaneous current steepness value for use as a disconnection criterion.