KR101037000B1 - Digital relay capable of seting a delay time and method for processing input signal in digital relay - Google Patents

Abstract

The present invention provides a high-speed operation by minimizing the input delay in a stable field by providing an input delay in the digital input processing portion of the digital protective relay as necessary in accordance with the environment in which the digital relay is used, noise and voltage drop In the case of frequent dropping, the input delay is relatively long to prevent malfunction in the digital protection relay, thus enabling the digital relay to set the delay for the digital input detection that can operate the digital relay system stably. And an input signal processing method of a digital relay.

Delay Setting, Noise, Voltage Drop, Digital Relay

Description

DIGITAL RELAY CAPABLE OF SETING A DELAY TIME AND METHOD FOR PROCESSING INPUT SIGNAL IN DIGITAL RELAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital protective relay. In particular, a reference delay time for determining abnormality of a three-phase power supply when a change occurs in an input signal of a detection voltage and a detection current of a three-phase power supply is freely set according to a user's environment. The present invention relates to a digital relay, and an input signal processing method of the digital relay.

In general, digital relays are installed in electric circuits, communication lines, etc. to accurately detect the state of relay targets such as overcurrent, phase loss, phase imbalance, and reverse phase by a predetermined time by a user, etc. Appliance.

In addition, the relay detects the voltage and current of the system in the protection range from the voltage transformer PT and the current transformer CT. As relays evolve from inductive or stationary relays to digital relays, they require a wider range of correction and accuracy of operation. In particular, current digital relays must detect and accurately operate the system's voltage and current without distortion even in a wide range of low current of less than 1A and low voltage of less than 10V to hundreds of A and hundreds of V.

Hereinafter, a digital input circuit of a digital protection relay according to the prior art will be described with reference to the accompanying drawings.

1 is a configuration diagram schematically showing a conventional digital relay, and FIG. 2 is a voltage waveform diagram of an output affected when a disturbance occurs in an input in the conventional digital relay device.

Referring to FIG. 1, the digital protection relay 10 includes a signal input unit 11, an input unit display unit 12, an operation and control unit 13, a digital input unit 14, a digital output unit 15, and a trip coil driver ( 16). Here, the trip coil driver 16 is connected to the trip coil 31 of the circuit breaker 30.

As described above, the digital protective relay receives an input of the relay through a current transformer (aka current transformer) 40 and a voltage transformer 50, a signal input unit 11, and a digital input unit 14 in an electric line, and calculates and The control unit 13 is configured to control the digital output unit 15 and the trip coil driver 16.

The signal input unit 11 receives an analog signal of a phase-specific detection current and a detection voltage for the three-phase power supply from the current transformer 40 and the voltage transformer 50 to step down the voltage level of the corresponding analog signal, thereby reducing the digital input unit 14. The input unit display unit 12 functions to externally display the detected current and the detected voltage input to the signal input unit 11.

The digital input unit 14 is composed of an analog-to-digital conversion circuit and receives an analog signal of phase-specific detection current and detection voltage from the signal input unit 11 and outputs a signal converted into a digital signal to the calculation and control unit 13. .

The calculation and control unit 13 outputs a driving control signal for determining whether the trip coil driving unit is driven based on the output digital signal of the digital input unit 14, and also based on the output digital signal of the digital input unit 14. And an output signal for controlling the digital output unit 15 by processing.

The digital output unit 15 inputs an output signal of the operation and control unit 13 to output a signal for controlling the operation of the component.

The trip coil driver 16 generates a control signal for driving or stopping the trip coil 31 of the circuit breaker 30 according to the operation and the drive control signal from the controller 13.

In Fig. 1, reference numeral 20 denotes a load.

In the conventional digital relay, when noise, such as an imaging voltage, is input to the input terminal of the digital input unit 14, an imaging voltage signal is input from the output terminal of the digital input unit 14 so that a phase image may be mistaken as a phase is generated from a three-phase power source. Output the same signal as

That is, as shown in FIG. 2, when the disturbance duration Ts is long when the external disturbance occurs, even after the forced delay of the predetermined delay time Thd, the disturbance is outputted as a voltage signal in the phase of occurrence of phase error. cause.

Here, the delay time Thd represents a forced delay time due to hardware, and the disturbance duration Ts represents a time for which the disturbance caused by an external factor lasts as an input signal to the input terminal.

The present invention is to set the delay time on the output for the input change so that the change in the input signal does not affect the output signal in the case where the environment where the digital relay is used, noise and voltage drop frequently occurs, The present invention provides a digital relay capable of setting a delay for digital input detection that can stably operate a digital relay system by preventing malfunction of the product due to external noise or voltage drop, and an input signal processing method of the corresponding digital relay.

According to an aspect of the present invention, there is provided a digital relay capable of delay setting, including: a signal input unit configured to receive input signals of phase detection voltages and detection currents of a three-phase power supply and to step-down and output the voltages of the input signals;

A digital input unit which removes and outputs high frequency noise from the stepped down input signal output from the signal input unit;

An A / D converter converting the analog signal output from the digital input unit into a digital signal;

A setting delay time input unit for storing and providing a setting delay time preset to provide a reference delay time for determining an abnormality of the three-phase power source;

And a controller configured to compare the set delay time and the duration of the change when a change occurs in the input signal, and determine whether an abnormality occurs in the input signal according to the result.

The object of the present invention is a variation occurrence determining step of receiving an input signal of a phase detection voltage and a detection current of a three-phase power supply and comparing the input signal with a previous input signal to determine occurrence of variation in the input signal;

An abnormality determining step of determining whether the variation is noise or an abnormality of the three-phase power source when the variation occurs in the input signal;

If it is determined that the fluctuation is noise, it can be achieved by providing an input signal processing method of a digital relay according to the present invention comprising a processing step of processing the input signal as the same as the previous input signal.

According to the present invention, a digital relay capable of delay setting for detecting a digital input and a delay setting method using the same may be configured by temporarily setting an appropriate setting delay time according to a site environment in which noise and voltage drop occur. In case of fluctuation, it is possible to stably operate the digital relay by preventing the malfunction of the digital relay which cuts off the power to the load by mistaken decision of abnormality of three phase power.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram illustrating a configuration of a digital relay device according to an embodiment of the present invention, and FIG. 4 is a block diagram of a delay processing unit for an input signal of a digital relay device according to an embodiment of the present invention.

3 and 4, a digital relay 100 capable of setting a delay for sensing a digital input according to an embodiment of the present invention receives an analog signal of a detection current and a detection voltage for each phase of a phase power source, and receives a corresponding analog signal. A signal input unit 11 for stepping down and providing a voltage level of an analog signal; A digital input unit 110 which removes and outputs high frequency noise from a signal output from the signal input unit 11; An analog-digital converter 120 for converting an analog signal output from the digital input unit 110 into a digital signal; A delay time input unit (140) for providing a set delay time to prevent a malfunction of detection of the input signal due to noise; When the noise occurs in the input signal includes a control unit 130 for comparing the variation prevention signal and the duration of the noise, and determines whether to reflect the change in the input signal to the output signal according to the result.

The digital input unit 110 includes: a noise removing unit Z1 composed of a varistor for removing noise from an input signal (analog voltage signal) input from the signal input unit 11; Voltage divider (R1, R2) for dividing the analog voltage of the input signal from which the noise is removed; A photo coupler 111 for noise-isolating and transmitting the input signal divided by the voltage divider; The low frequency filter unit R3 and C1 may be provided to the analog-to-digital converter 120 of the rear stage by removing the high frequency noise and passing only the low frequency signal to the signal transmitted from the photo coupler 111.

In more detail, the digital input unit 110 receives the detected voltage and the detection current for the three-phase power supply from the signal input unit 11 through the first and second nodes Nd1 and Nd2 and receives the analog voltage signal as an analog voltage signal. Noise, such as a surge voltage included in the power supply, is removed from the varistor ZNR1 forming the noise canceling unit connected between the first and second nodes.

The input power source from which the noise is removed is divided by the resistor R1 and the resistor R2 of the voltage divider, and the divided input voltages are connected to the terminals 1,2 connected to the second and third nodes Nd2 and Nd2. It is input to the photocoupler 111 through. The photocoupler is insulated so as not to include high frequency noise in the voltage input through the first and second terminals, and the terminals 3 and 4 are energized, and the voltage Vcc is connected to the energized terminals 3 and 4 and the low pass filter unit R3 and C1. Only low-frequency signal through the filter is provided to the analog-to-digital converter 120.

Since the input signal (low frequency signal) of the detection voltage and the detection current for the three-phase power provided by the digital input unit 110 through the low frequency filter units R3 and C1 is in the form of an analog signal, the analog-digital converter 120 For converting the analog signal from the digital input unit 110 to a digital signal for use in the control unit 130 and outputs to the control unit 130.

That is, when the digital input unit receives the power Vin to the first and second nodes, the photocoupler 111 is set to " R2 × " A voltage of Vin / (R1 + R2) "is applied. In this case, when the applied voltage is applied to the first and second terminals (primary side) of the photocoupler 111, the applied voltage drives the photocoupler 111 to the third and fourth terminals (secondary side). Turn on. At this time, the high frequency noise in the photocoupler 111 is insulated from being transmitted from the first and second terminals (primary side) to the third and fourth terminals (secondary side).

In this case, the control unit 130 receives a setting delay time through the delay time input unit 140, wherein the setting delay time is for maintaining the state before the change of the input signal occurs when the change of the input signal due to the noise occurs. The delay time is a time value (time setting data) that can be selectively set by the user according to the site where the digital relay is installed.

When a change in the input signal occurs, the controller 130 does not reflect the change in the input signal to the output signal when the noise duration is less than the delay time, and the duration of the noise is greater than the delay time. If large, the change in the input signal is reflected in the determination of whether the trip coil is driven.

That is, when the duration of the noise is less than the delay time, since the variation of the input signal is caused by noise, the output signal does not change according to the variation of the input signal. However, if the duration of the noise is greater than the delay time, the variation of the input signal is not caused by noise but an abnormality in the input signal (i.e., the detection voltage and the detection current of the three-phase power supply). Will fluctuate accordingly. In other words, when an abnormality occurs in the input signal, the controller 130 controls the trip coil driver 16 to drive the trip coil 31 to cut off the power supplied to the load, thereby protecting the load.

The setting delay time may be changed and set by the user through the delay time input unit 140, and the data of the setting delay time according to the use environment may be stored in the form of a data table in the controller.

5 is a flowchart illustrating a method of setting an input delay of a digital relay according to an embodiment of the present invention.

Referring to FIG. 5, in the method of setting an input delay of a digital relay according to an embodiment of the present invention, receiving input signals of a detection voltage and a detection current for a three-phase power source and detecting whether the input signal is changed (S200). )Wow; An abnormality determining step (S230) of determining whether the variation of the input signal is noise or whether an abnormality has occurred in the three-phase power source; If the variation is determined as noise, a processing step of maintaining the input signal as the input signal before the variation and processing it in a steady state is included (S260).

When an input signal of a three-phase power source such as AC 100V is input through the signal input unit 11 (S100), the corresponding input signal is the signal input unit 11, the digital input unit 1, and the analog-digital conversion unit (FIG. 3) of FIG. 3. Through step 120, the digital signal is converted into a digital signal while the high frequency noise is removed and input to the controller 130.

The controller 130 determines whether a change occurs in the input signal data by comparing the input signal input through the analog-to-digital converter 120 with the previous input signal in the change determination step (S200).

 Next, the control unit 130 reads the setting delay time set by the user from the setting delay time input unit 140 as a reference time for determining the abnormality of the three-phase power for the input signal.

When a change occurs in the input signal data, the controller 130 measures the duration of the change through a counter (not shown) provided therein (S220), and measures the set delay time and the measured duration time. In comparison (S230), when the duration is shorter than the delay time, the variation is determined to be noise, and when the duration is longer than the delay time, it is determined that the three-phase power supply is abnormal. When it is determined that there is an abnormality in the three-phase power supply, the control unit 130 drives the trip coil 31 through the trip coil driving unit 16 to cut off the supply of the three-phase power supply to the load side.

If the duration is shorter than the delay time, the controller 130 determines that the variation of the input signal is noise, and maintains the input signal as the same as the pre-change input signal to process it in a normal state. However, when the duration is longer than the delay time, it is determined that the change in the input signal is not a noise but an abnormality in the three-phase power source. However, although not shown, the trip coil 31 is connected through the trip coil driver 16. It controls to cut off the supply of the load side of 3-phase power supply.

The setting delay time may be changed by the user or the administrator according to the installation application environment of the digital relay with various noise and voltage drop occurrence frequency.

FIG. 6 is a waveform diagram of an input signal DIGITAL INPUT and an input signal (relay processing DI) determined and processed by the controller when the input variation duration Ts is longer than the set delay time Td. Thd is a delay time due to circuit element characteristics. FIG. 7 is a waveform diagram of an input signal DIGITAL INPUT and an input signal (relay processing DI) determined and processed by the controller when the input variation duration Ts is shorter than the set delay time Td.

While the invention has been shown and described with respect to specific embodiments thereof, those skilled in the art can variously modify the invention without departing from the spirit and scope of the invention as set forth in the claims below. And that it can be changed. However, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

1 is a block diagram of the configuration of a digital relay device in the prior art.

FIG. 2 is a voltage waveform diagram of a digital input signal processed by a controller in response to a disturbance occurring in an input in the conventional digital relay device.

3 is a block diagram of a configuration of a digital relay device according to an embodiment of the present invention.

Figure 4 is a block diagram showing the configuration of the main part of the digital relay including a detailed circuit diagram of the digital input unit of the digital relay according to an embodiment of the present invention.

5 is a flowchart of an input signal processing method of a digital relay according to an embodiment of the present invention.

6 is a waveform diagram of an input signal and an input signal corrected by the controller when the input variation duration is longer than the set delay time.

7 is a waveform diagram of an input signal and an input signal corrected by the controller when the input variation duration is shorter than the set delay time.

* Explanation of symbols on the main parts of the drawings

10: digital protective relay 11: signal input

12: input unit display unit 13: operation and control unit

14: digital input unit 15: digital output unit

16: trip coil drive 20: load

30: breaker 31: trip coil

40: current transformer 50: voltage transformer

100: digital relay 110: digital input unit

120: analog-digital conversion unit 130: control unit

140: delay time input unit

Claims (8)

A signal input unit for receiving an input signal of a phase detection voltage and a detection current of a three-phase power supply and stepping down and outputting the voltage of the input signal; A digital input unit which removes and outputs high frequency noise from the stepped down input signal output from the signal input unit; An analog-digital converter converting the analog signal output from the digital input unit into a digital signal; A setting delay time input unit for storing and providing a setting delay time preset to provide a reference delay time for determining an abnormality of the three-phase power source; And a controller configured to compare the set delay time and the duration of the change when a change occurs in the input signal, and determine whether an abnormality occurs in the input signal according to the result. The method of claim 1, The digital input unit, A noise removing unit for removing high frequency noise from the stepped down input signal output from the signal input unit; A voltage divider which divides the voltage of the input signal from which the high frequency noise is removed; A photo coupler for outputting a high frequency isolated analog signal according to the divided input signal; And a low pass filter configured to filter and output only a low frequency signal from the analog signal output by the photo coupler. The method of claim 1, The control unit, When the fluctuation of the input signal occurs, if the duration of the fluctuation is less than the set delay time, the fluctuation of the input signal is determined to be noise to process the input signal to remain in the state of the previous input signal, and And a control unit for determining that an abnormality has occurred in the three-phase power supply when the duration is greater than the set delay time. The method of claim 1, The setting delay time is, And a delay setting digital relay, characterized in that the data can be changed and set by the user through the set delay time input unit. A fluctuation generation determining step of receiving an input signal of a phase detection voltage and a detection current of a three-phase power source and comparing the input signal with a previous input signal to determine occurrence of fluctuation of the input signal; When a variation occurs in the input signal, the predetermined delay time is compared with the measured variation duration, and when the duration is shorter than the delay time, it is determined that the variation is noise and the duration is greater than the delay time. An abnormality determining step of determining whether an abnormality of the three-phase power source has occurred if it is long; And if it is determined that the variation is noise, processing the input signal as the same as the previous input signal. The method of claim 5, The abnormal determination step, Setting a delay time during which the change in the input signal is not reflected in the output signal; Measuring a duration of the change when a change occurs in the input signal; By comparing the delay time with the duration, if the duration is shorter than the delay time, it is determined that the variation is caused by noise. When the duration is longer than the delay time, the variation is determined by the input signal itself. And a variation determination step of determining that the variation is a variation. The method of claim 5, The processing step, And the variation of the input signal reflects the variation of the input signal to the output signal. The method of claim 6, The delay time can be adjusted according to the application environment input signal processing method of the digital relay.

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