DEVICE FOR COMPLEX PROTECTION OF ELECTRIC SYSTEM Russian patent published in 1998 - IPC

FIELD: three-phase power supply systems with insulated neutral wire, in particular, for track instruments. SUBSTANCE: device has two test channels for detection of phase disbalance and break and current overload. In addition device has actuating control element and actuating member. Introduced detector of insulation resistance is designed as filter of zero phase-sequence voltage. Detector of phase disbalance and break is designed as reverse sequence filter. Current overload filter is designed using single current transformer. Actuating control elements are designed using Schmidt flip-flops as comparators. Actuating member is designed as thyristor optical coupled pair, gate amplifier of thyristor optical coupled pair, gate amplifier of thyristor and semistor. In addition device has indication unit which is designed as three-channel RS flip- flop with fault indicator. In fault mode actuating control element forces actuating member to turn device off power supply and turn fault indication on. EFFECT: simplified design, increased sensitivity, increased reliability. 11 dwg