NEGATIVE-SEQUENCE CURRENT MEASURING TRANSDUCER FOR THREE-PHASE THREE-WIRE CIRCUIT Russian patent published in 2014 - IPC G01R29/16 

FIELD: electricity.

SUBSTANCE: device comprises the first and second differentiating current induction transducers (DCIT) and negative-sequence voltage filter which consists of the three elements: a capacitor, a resistor and a switch. Coils of the first and second DCITs are connected to input terminals of the filter. Mutual inductance of the second DCIT coil and the second current lead of the three-phase circuit is twice less than the same of the first DCIT coil and the third current lead of the three-phase circuit. Between the beginning and end of the first DCIT there is in-series capacitor and resistor. The first output terminal of the device is connected to the connection point of the capacitor and resistor. To the end of the first DCIT coil beginning of the second DCIT coil is connected and the end of the second DCIT coil is coupled through a switch to the second output terminal of the device. At rated frequency of the three-phase circuit voltage at the resistor advances electromotive force of the first DCIT per angle of π/3, while module of this voltage is one half of the above electromotive force module.

EFFECT: increasing sensitivity towards the negative-sequence current component in phase currents of the protected three-phase circuit, in particular, to disconnection of one phase in this circuit from the three-phase voltage source.

5 dwg