KR20030037095A - Method and apparatus for detecting error of digital protective relay - Google Patents

Abstract

PURPOSE: A breakdown detecting device is provided to protect an equipment and a line by separating a breakdown phase when an abnormal state is detected at a three phase current and a three phase voltage. CONSTITUTION: A three phase circuit input part receives a three phase voltage(Va,Vb,Vc), a three phase current(Ia,Ib,Ic) and an intermediate current(In). The first breakdown detecting part(200) calculates effective values of the three phase voltage(Va,Vb,Vc) and the three phase current(Ia,Ib,Ic) and detects whether or not of breakdown according to a calculated result. The second breakdown detecting part(300) extracts sample data of the three phase voltage(Va,Vb,Vc) and the three phase current(Ia,Ib,Ic) and detects whether or not of breakdown according to a comparison result with reference data. A combination part(400) issues a breakdown detection signal output from either one of the first and second breakdown detecting parts(200,300).

Description

Fault detection apparatus and method of digital relay {Method and apparatus for detecting error of digital protective relay}

TECHNICAL FIELD The present invention relates to relays, and more particularly, to a digital protective relay that enables high-precision, wide range of voltage and current sensing.

In general, protection relays are devices installed in electric circuits, communication lines, etc., to accurately detect overcurrent, phase loss, phase imbalance, and reverse phase by a set operating time to protect devices or lines more accurately.

In addition, the digital protection relay is provided with voltage and current transformers (PT, CT) therein, through which they sense the voltage and current of the protection range system.

Such protection relays require a more precise, wide range of correction, particularly for low current and low voltage, and accurate protection as the flow is shifted from inductive or stationary relays to digital relays.

Hereinafter, a failure detection apparatus for a digital protection relay according to the prior art will be described with reference to the accompanying drawings.

1 is a block diagram showing a fault detection apparatus of a digital protection relay according to the prior art, Figure 2 is a diagram showing the configuration of the fault detection logic shown in FIG.

As shown in FIG. 1, the fault detection device of the digital protection relay according to the prior art is inputted through an instrument transformer (not shown) (hereinafter PT) and an instrument transformer (not shown) (hereinafter CT). Three-phase circuit input unit 10 that receives phase voltages Va, Vb, Vc, three-phase currents Ia, Ib, Ic, and neutral current In, and through the three-phase circuit input unit 10. It is composed of a failure determination unit 20 for determining whether the failure by receiving the input voltage value and current value.

The failure determining unit 20 includes an effective value calculating unit 21 for calculating an effective value Ia_rms, Ib_rms, Ic_rms of three-phase currents Ia (Ib) (Ic) to the three-phase circuit input unit 10, The failure detection logic 22 outputs a failure detection value FD_OUT by receiving the effective values Ia_rms, Ib_rms, and Ic_rms calculated by the rms calculation unit 21.

In addition, the failure detection logic 22 receives an effective value Ia_rms (Ib_rms) (Ic_rms) of the three-phase current calculated by the effective value calculator 21 and compares it with a preset reference effective current value IP_LV. The first comparator 22a for outputting the signal, the second comparator 22b for receiving the effective value of the image current and comparing the value with the effective image current reference box I0_LV, the faulty selection element FPS_OP, and fault detection. A first end gate 22c for receiving an element reset FD_RST and a three-phase effective current and performing an AND operation, the first and second comparators 22a and 22b, and an effective value of the three-phase current The second AND gate 22d that receives Ia_rms) (Ib_rms) (Ic_rms) and performs an AND operation, and receives the output of the first AND gate 22c to perform an OR operation to perform a fault detection element FD_OUT. Or gate 22e for outputting

Referring to the operation of the failure detection device of the digital protective relay according to the prior art configured as described above are as follows.

First, the effective value calculator receives three-phase voltages Va, Vb, Vc, three-phase currents Ia, Ib, and three-phase neutral current In, which are input through the three-phase circuit input unit. () Performs an effective operation through a Discrete Fourier Transform (DFT).

Then, the failure detection logic 22 receives the effective value calculated by the effective value calculation unit 21 and outputs a failure detection element. That is, the three-phase effective value Ia_rms (Ib_rms) (Ic_rms) calculated by the effective value calculator (1) is inputted to the first comparator 22a to be compared with a preset effective current reference value IP_LV, and then the three-phase input. When the current effective value Ia_rms Ib_rms Ic_rms is smaller than the reference value IP_LV, a high signal is output.

In addition, the second comparator 22b receives an effective value I0_rms of the image current and an image current reference value I0_LV, and outputs a high signal when the effective value I0_rms of the image current is larger than the image current reference value I0_LV. do.

Then, the OR gate 22e outputs a high signal when a high signal is output from either the first comparator 22a or the second comparator 22b, and the signal is the first comparator. It is fed back to the AND gate 22c.

The first AND gate 22c is a fault image selection element FPS_OP that outputs a high signal by determining a phase in which a fault occurs among three phases, and a signal output from the or gate is incorrectly determined. The inverting value of the reset signal FD_RST and the output signal of the second and gate G2 are input to perform a logical multiplication operation.

At this time, the reset signal FD_RST is generated when the effective values of the three-phase currents are all restored to 40% or more of the preset rated currents.

As described above, the failure detection apparatus of the digital protection relay according to the prior art has the following problems.

First, the effective detection of the fault detection element is performed by the Discrete Fourier Transform. However, due to the characteristics of the Discrete Fourier Transform, the minimum time must elapse before the effective value calculation is completed.

Second, it affects the operation time of relays that need to detect and disconnect quickly such as overcurrent relays that require frequent operation in case of system failure.

The present invention has been made to solve this problem, if abnormal conditions are detected in the three-phase voltage and three-phase current, the fault phase is separated from the electric field through the rapid fault detection and the fault is removed and the fault system is separated from the system It is an object of the present invention to provide an apparatus and method for detecting a failure of a digital protective relay to protect equipment and lines.

1 is a block diagram showing a fault detection apparatus of a digital relay according to the prior art.

2 is a detailed view of the fault detection logic shown in FIG.

3 is a block diagram showing a fault detection apparatus of a digital relay according to the present invention.

4 is a data window for obtaining a magnitude and phase of a signal using the sample data calculated in FIG.

5 is a flowchart illustrating a fault detection method of a digital relay according to the present invention.

Explanation of symbols for main parts of the drawings

100: three-phase circuit input unit 200: first fault detection unit

201: effective value calculation unit 202: fault detector

300: second failure detection unit 400: combination unit

The fault detection apparatus of the digital protection relay according to the present invention for achieving the above object is for receiving the three-phase voltage (Va, Vb, Vc), three-phase current (Ia, Ib, Ic) and the neutral current (In) A first value for calculating an effective value of the three-phase circuit input unit and the three-phase voltages Va, Vb, and Vc and the three-phase currents Ia, Ib, and Ic inputted through the three-phase circuit input unit and detecting a failure accordingly; Fault detection unit, and extracts the sample data of the three-phase voltage (Va, Vb, Vc) and three-phase current (Ia, Ib, Ic) input through the three-phase circuit input unit and whether the failure according to the preset reference data and comparison results And a combination unit for outputting a second failure detection unit for detecting a failure detection signal is output from any one of the first failure detection unit or the second failure detection unit.

In the fault detection method of the digital protection relay for achieving the above object, in the fault detection method of the digital protection relay, extracting the sample data of the three-phase voltage to calculate the voltage level of each of the three phases, the calculated voltage level is Determining whether a failure occurs according to whether a predetermined number of times is smaller than a predetermined reference voltage or not, and determining whether to extract sample data according to whether or not there is a failure determination if the calculated voltage level is equal to or greater than a predetermined reference voltage. It is made to include its features.

Hereinafter, an apparatus and method for detecting a failure of a digital protective relay according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram showing a fault detection apparatus of a digital protection relay according to the present invention, FIG. 4 is a screen showing a window for detecting a fault of the second fault detection unit shown in FIG. 3, and FIG. 5 is a digital display according to the present invention. This is a flowchart showing the fault detection method of the protective relay.

The fault detection device of a digital protection relay according to the present invention includes a three-phase circuit input unit (3) for receiving three-phase voltages Va, Vb, Vc, three-phase currents Ia, Ib, Ic, and a neutral current In; First failure detection unit for calculating the effective value of the three-phase voltage (Va, Vb, Vc) and three-phase current (Ia, Ib, Ic) input through the three-phase circuit input unit 100 and detects whether there is a failure accordingly And the sample data of the three-phase voltages Va, Vb, and Vc and the three-phase currents Ia, Ib, and Ic inputted through the three-phase circuit input unit 100 to compare with the preset reference data. According to the second failure detection unit 300 for detecting whether the failure, either the first failure detection unit 200 or the second failure detection unit 300, a combination unit for outputting a failure detection signal is output It consists of 400.

The first failure detection unit 200 receives the three-phase voltage (Va, Vb, Vc), three-phase current (Ia, Ib, Ic) and the neutral current (In) input through the three-phase circuit input unit 100 An effective value calculator 201 for calculating an effective value and a failure detector 202 for detecting a failure by receiving the effective value calculated by the effective value calculator 201 are configured.

On the other hand, the second failure detection unit 300 extracts the sample data of the three-phase voltage input through the three-phase circuit input unit 100 through a failure detection algorithm, if the normal data is not extracted a predetermined number of times as a failure It consists of an algorithm for determining.

Then, the combination unit 400 is configured as an or gate, and when a failure detection signal is input from either the first failure detection unit 200 or the second failure detection unit 300, the combination unit 400 may be notified of a failure occurrence. have.

In this case, referring to FIG. 5, the algorithm operated by the second failure detection unit 300 is first extracted sample data of an input three-phase voltage (S11).

Then, the calculated sample data is applied to the least square method to calculate the voltage level (S12).

It is determined whether the calculated voltage level is smaller than a preset reference voltage level (S13).

Subsequently, when the calculated voltage level is lower than the preset reference voltage level (S13), the voltage level is continuously determined about three times while increasing the count value one by one (S14 to S15).

As a result of the determination (S15), if the voltage level is lower than the preset reference voltage level three or more times, it is determined that a failure has occurred and outputs a high signal (S16).

On the other hand, if the calculated voltage level is higher than the predetermined reference voltage level (S13), it is determined whether the count value is 0 (S17).

Subsequently, if the calculated voltage level is greater than 0, the determination result S17 decreases the count value and returns to step S11.

On the other hand, if the calculated voltage level is 0, the determination result (S17) sets the count value to 0, and returns to the initial step (S11) (S19).

Therefore, in the fault detection method of the digital protection relay according to the present invention, the magnitude and phase of a signal can be obtained using the above method, and the screen appearing in the window is as shown in FIG.

When the waveform of the voltage and current of the power system of the three-phase voltage and the three-phase current to be input is expressed as a formula.

Yc, Ys: magnitude of cos and sin terms

yk: kth sample value

ω _0: each frequency of the system

Δt: Sampling period

Θ: angular velocity

That is, three samples are acquired at times of -Δt, 0, and Δt using Equation 1, and the magnitude and phase of each phase are calculated using the following least square method.

The magnitude and phase of the input three-phase voltage and three-phase current can be obtained by using the above equation.If the magnitude and phase of the calculated three-phase voltage are obtained, and the magnitude is less than the voltage reference value, the count is increased by one. Get the sample data.

That is, if the count value is greater than 3, it is determined that a failure has occurred and outputs a high signal, and if the count value is less than 3, the count value is decreased by 1 so that only when the voltage is more than 3 samples consecutively less than the reference value It is determined that an error has occurred in the phase and inputs a high signal to the combination unit 400.

Then, the combination unit 400 combines the output of the first failure detection unit 200 and the output of the second failure detection unit 300 to output the failure detection element FD_OUT to the next relay element.

As described above, the fault detection device and method of the digital protection relay according to the present invention, when an abnormal state is detected in the three-phase voltage and three-phase current input through the instrument transformer, the transformer for the instrument to detect it quickly and In general, there is an effect to protect the equipment and lines on the system by separating the fault phase, removal of the fault and separation of the fault system.

Claims (5)

A three-phase circuit input unit for receiving three-phase voltages Va, Vb, and Vc, three-phase currents Ia, Ib, and Ic, and a neutral current In; A first failure detection unit for calculating an effective value of three-phase voltages Va, Vb, and Vc and three-phase currents Ia, Ib, and Ic inputted through the three-phase circuit input unit and detecting whether there is a failure accordingly; Extracts sample data of three-phase voltages Va, Vb, and Vc and three-phase currents Ia, Ib, and Ic inputted through the three-phase circuit input unit, and detects whether or not a failure occurs according to a comparison result with preset reference data A second fault detection unit; And, And a combination unit for outputting a fault detection signal when the fault detection signal is output from either the first fault detection unit or the second fault detection unit. The method of claim 1, And the combination part is an or gate. In the fault detection method of the digital protective relay, Calculating voltage levels of each of the three phases by extracting sample data of the three phase voltages; Determining whether or not a failure occurs according to whether the calculated voltage level is a predetermined number or more smaller than a preset reference voltage; And, And determining whether to extract sample data according to whether or not there is a failure determination in the case where the calculated voltage level is equal to or greater than a preset reference voltage. The method of claim 3, wherein The step of calculating the three-phase voltage level Comprising a step of calculating the voltage level through the magnitude and phase of the input three-phase voltage. The method of claim 3, wherein And the predetermined number of times is three times.