DEVICE FOR PROTECTING AGAINST SINGLE-PHASE EARTH FAULTS IN NETWORKS WITH ISOLATED NEUTRAL Russian patent published in 2017 - IPC H02H3/16 

FIELD: electricity.

SUBSTANCE: device comprises a residual current filter, a secondary current converter, a bandpass filter passing the main component of 50 Hz, a first current measuring element, a first time delay element, a higher harmonic component frequency bandpass filter, a first and a second unit for calculating the signal RMS value at the given averaging time interval, a scheme for comparing the values of two electrical quantities, a second current measuring element, a measuring unit for time Δt intervals between the surges of the transient current 3i₀ with an arc intermittent earth fault, the element of comparing the measured value Δt to a given value Δt_g, an EXCEPT element, a first and a second AND element, an OR element, a second time delay element.

EFFECT: increasing the sensitivity of the residual current protection against single-phase earth faults of medium-voltage electrical networks operating with isolated neutral both for stable and for the most dangerous for the network arc intermittent earth faults.

4 dwg