METHOD OF PROTECTION AGAINST SINGLE PHASE-TO-EARTH FAULTS IN MEDIUM VOLTAGE ELECTRICAL NETWORKS Russian patent published in 2018 - IPC H02H3/00 

FIELD: electrical engineering.

SUBSTANCE: in the method of protection against single phase-to-earth faults in medium voltage electrical networks, including monitoring of zero-sequence current 3i₀ and zero sequence voltage u₀, determining the earth fault in the network based on the value of the zero sequence voltage, additionally determine the earth fault based on the value of the zero sequence current, differentiate the zero sequence voltage u₀, suppress high-frequency components in zero-sequence current 3i₀ and in the derivative of the voltage zero sequence u_0. Determine the root-mean-square of the zero-sequence current 3I₀ and the derivative of the zero-sequence voltage U'₀, find their attitude 3I₀/U'₀, the value obtained in this case is compared with the setpoint determined by the capacitance of the phases-to-earth of the protected connection, above which, and in the presence of a earth fault in the network, form an output signal of an internal single-phase short circuit to earth.

EFFECT: increasing selectivity and sensitivity of protection against single phase-to-earth faults.

1 cl, 6 dwg