Digital protective relay

Patent metadata

Field	Value
Publication number	US-2016233876-A1
Application number	US-201615003728-A
Country	US
Kind code	A1
Filing date	Jan 21, 2016
Priority date	Feb 6, 2015
Publication date	Aug 11, 2016
Grant date	—

Abstract

The present disclosure relates to provide an active erroneous sample elimination device or erroneous sample elimination method for a relay capable of correctly implementing erroneous sample elimination processing even during a plurality of electrical disturbances mixed with an electrical quantity detection signal, and a digital protective relay according to the present disclosure may include a converter that samples an analog signal and converts the sampled signal to a digital signal; and a processor that searches an inflection point at which an electrical variation quantity varies from an increase to a decrease or from a decrease to an increase based on the digital signal, and compares an electrical variation quantity prior to and subsequent to the inflection point with a preset electrical quantity.

First claim

What is claimed is:

1 . A digital protective relay, comprising:
a converter that samples an analog signal and converts a sampled analog signal to a digital signal; and a processor that searches an inflection point at which an electrical variation quantity varies from an increase to a decrease or from a decrease to an increase based on the digital signal, and compares an electrical variation quantity prior to and subsequent to the inflection point with a preset electrical quantity.

2 . The digital protective relay of claim 1 , wherein the processor is configured to perform a Discrete Time Fourier Transform on the digital signal for a predetermined period of time, to compare a value at which a transformed value is increased and then converged with a predetermined normal convergence value, to determine the digital signal as a harmonic wave when a difference between the constantly converged transformed value and the predetermined normal convergence value exceeds a predetermined difference, and to determine the digital signal as an electrical disturbance when the difference between the constantly converged transformed value and the predetermined normal convergence value is larger or equal to a reference electrical variation quantity.

3 . The digital protective relay of claim 2 , wherein the processor is configured to perform a root mean square processing on the digital signal when the digital signal is determined as the harmonic wave.

4 . The digital protective relay of claim 2 , wherein the processor is configured to substitute an electrical quantity data at the inflection point with an electrical quantity data prior to a predetermined period when the digital signal is determined as the electrical disturbance.

5 . A noise elimination method for a digital relay, the method comprising:
a sampling and analog-digital conversion step that allows an analog-digital converter to sample an analog signal of an electrical quantity detection signal and convert a sampled analog signal to a digital signal; an inflection point search step that searches an inflection point at which an electrical variation quantity varies from an increase to a decrease or from a decrease to an increase based on the digital signal by a processor; a variation quantity comparison step that compares an electrical variation quantity prior to and subsequent to the inflection point with a predetermined normal reference electrical variation quantity by the processor; and an electrical disturbance elimination step that determines the digital signal as an electrical disturbance and substitutes an electrical quantity data at the inflection point with an electrical quantity data prior to a predetermined period by the processor in case where an electrical variation quantity prior to and subsequent to the inflection point is not less than a predetermined normal reference electrical variation quantity during the variation quantity comparison step.

6 . The method of claim 5 , further comprising:
a Discrete Time Fourier Transform convergence value comparison step of performing a Discrete Time Fourier Transform on the digital signal for a predetermined period of time, and comparing a value at which the transformation value is increased and then converged with a predetermined normal convergence value by the processor; and a harmonic wave determination and processing step of determining that a harmonic wave is mixed with an electrical quantity detection signal to perform root mean square processing on the digital signal when a difference between the converged value and the normal convergence value exceeds a predetermined difference during the Discrete Time Fourier Transform convergence value comparison step.

Assignees

• Lsis Co Ltd

Inventors

• Kim Jiung

Classifications

• G01R31/50

  Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58) · CPC title

• G01R19/16509 Primary

  using electromagnetic relays, e.g. reed relay (magnetically driven reeds G01R9/06) · CPC title

• H02H1/04

  Arrangements for preventing response to transient abnormal conditions, e.g. to lightning {or to short duration over voltage or oscillations; Damping the influence of DC component by short circuits in AC networks} · CPC title

• G01R19/2509

  Details concerning sampling, digitizing or waveform capturing · CPC title

• G01R19/252

  using analogue/digital converters of the type with conversion of voltage or current into frequency and measuring of this frequency · CPC title