METHOD FOR MEASURING FAULT CURRENT Russian patent published in 2016 - IPC G01R19/30 

FIELD: electricity.

SUBSTANCE: method for measuring fault current consists in installation of four reed relays at safe distances h₁, h₂, h₃, h₄ from conductor; angle between perpendicular line of the conductor longitudinal axis and longitudinal axis of the first reed relay, the second, third and fourth relays is equal to 90°. The reed relays are adjusted so that they actuate at actuating currents I_AC4>I_AC3>I_AC2>I_AC1. Time is measured between closure of the first and second reed relays, the second and third reed relays, the third and fourth reed relays, which are placed in a magnetic field of the conductor so that they close contacts at the respective actuating currents I_AC1, I_AC2, I_AC3, I_AC4 in the conductor. Amplitude is determined for periodic component of the measured current I_c and initial value of aperiodic component of the measured current i_ca by solving simultaneous equations for actuating currents I_AC1, I_AC2, I_AC3, I_AC4, thereupon amplitude is determined for total fault current I_total as per the formula:

EFFECT: improved operation speed of the protection relay.

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