Earth-short monitoring circuit for three-phase networks - has resistance bridges rectified output controlling flip-flop coupled to logic

摘要

The earth-short monitoring circuit, for 3-phase networks, has a resistance bridge with one diagonal which is coupled to the output of the matching transformer is whose second diagonal is connected to an artificial neutral. The matching transformer is coupled to the phase monitoring transformer. Two bridge rectifiers (G1, G2) are connected to the output terminals of the resistance bridge (R1-R4) and supply a monostable flip-flop (44). The flip-flop has two outputs which are applied, together with the output of a spike generator (48) to two AND-gates (45, 46). The AND-gates drive a bistable flip-flop (49) that operates the indicator relay.