A known method of indicating faulty loops is described in the Siemens instruction manual "Digitaler Abzweigschutz" (Digital Feeder Protection) 7SA511 V3.0, Order No. C53000-G1100-C98-1, 1995 on page 36. In this conventional method, an impedance excitation is carried out in the form of a loop-related excitation process. It this context, after carrying out a first method step for detecting ground faults, the phase-to-ground loops are monitored in the event of at least one detected ground fault, and the phase-to-phase loops are monitored if there are no detected ground faults. A loop is considered as excited if the corresponding ascertained impedance indicator lies within the excitation polygon effective for the respective loop. If a plurality of loops are excited simultaneously, the impedances are compared, during which only those loops are classified as excited whose impedance is not more than 1.5-fold the smallest loop impedance.
USPTO Backgrounds
USPTO Backgrounds