KR101157125B1 - Device for detecting resistive current and method thereof - Google Patents

Abstract

PURPOSE: A device and a method for detecting resistive currents are provided to prevent the malfunction of a leakage breaker by accurately detecting the volume of required resistive currents. CONSTITUTION: A device for detecting resistive currents comprises a reference signal generator(30), a switch(20), and a signal measurement circuit(100). The reference signal generator inputs a reference signal for measuring a phase error to the switch. The switch is controlled by the signal measurement circuit and selectively inputs voltage and currents detected from the reference signal to the signal measurement circuit. The signal measurement circuit measures a phase error using the reference signal inputted from the switch and detects resistive currents using the measured phase error and the detected voltage and currents.

Description

Device for Detecting Resistive Current and Method Thereof}

The present invention relates to a resistive current detection device and a detection method, and more particularly, a reference signal of voltage and current is input from a reference signal generator 30, and a reference signal voltage is received from a signal measuring circuit 100 based on the reference signal. And it relates to a device and method for measuring the phase error of the current, by using the phase error and the detection voltage, the current to detect the resistive current to more accurately determine the overcurrent or short-circuit in an electrical safety device such as a circuit breaker.

Currently commercialized power sources used in many electrical appliances are alternating current signals. In Korea, AC current of 60 Hz is used, which consists of a resistive current and a capacitive current depending on the phase (FIG. 1). In general, a leakage current detector (ZCT) is used to measure the leakage current. When the leakage current detector is used, the capacitive current flowing to the ground due to the resistive current flowing through the ground insulation resistance and the capacitance of the line is used. Is measured in the form of the combined synthetic current. Among them, resistive current is the cause of electrical safety accidents such as overcurrent and short circuit. However, conventional electric safety devices such as earth leakage breakers do not distinguish between resistive current and capacitive current, and determine whether leakage or current is excessive based on the magnitude of the synthesized current. Even when the current flows in small amounts, it is often misjudged to a dangerous level. In particular, in the case of an earth leakage breaker used in an industrial facility, when the earth leakage is blocked, safety checks must be made after restarting the operation of the industrial facility to restart it.

In order to overcome this problem, conventionally, a method of detecting a resistive current by integrating a current for half a cycle of a power supply voltage has been used. Referring to FIG. 2, the voltage measuring circuit 110 and the current measuring circuit 120 measure the voltage and current of the line to be measured 10 and input them to the integrating circuit through an A / D converter to convert the current to half of the voltage. When integrating over a period, the resistive current can be computed. However, in this case, the signal is delayed due to the device characteristics of the circuit for measuring the supply voltage and current, which causes phase error in the measured voltage and current. Due to the phase error, the integration period is different in the operation of integrating the current for half a period of the voltage, which causes a large error in the calculation result of the resistive current, thereby reducing the accuracy of short circuit and overcurrent determination.

Accordingly, in the present invention, in detecting a resistive current for accurately determining whether a short circuit or overcurrent is detected, a phase delay caused by device characteristics of the signal measuring circuit 100 including the voltage and current measuring circuits 110 and 120 may be reduced. It aims at measuring in advance and preventing the error of resistive current detection which arises because of a phase delay. In addition, it is an object to more accurately detect the resistive current by adjusting the integral section of the resistive current detection calculation to reflect the phase error.

The device for detecting the resistive current for solving the above object is a reference signal generator 30 for inputting a reference signal for phase error measurement to the switch 20, the reference signal or the measurement target of the reference signal generator 30 The phase error is measured using a switch 20 for selectively inputting the voltage and current detected from the line into the signal measuring circuit 100 and a reference signal input from the switch 20, and the phase error and the detected voltage are measured. And a signal measuring circuit 100 that detects the resistive current using the current.

The signal measuring circuit 100 includes a voltage measuring circuit 110 measuring a voltage input through a switch 20, a current measuring circuit 120 measuring a current input through a switch 20, and the voltage measuring circuit. Using an analog to digital (A / D) converter for converting the voltage and current measured by the 110 and the current measuring circuit 120 into a digital signal and the voltage and current converted into a digital signal by the A / D converter 130 And a digital logic circuit 200 for detecting a resistive current, wherein the reference signal generator 30 includes a digital-to-analog (D / A) converter and generates a voltage and current generated by the digital logic circuit 200. D / A conversion and input to the reference signal.

Meanwhile, the resistive current detector further includes a reference signal generating load 400 connected to the line under measurement to convert the voltage and current measured at the line under measurement to be input as a reference signal, and the reference signal generator 30 when the reference signal is input. And selectively using the reference signal generating load 400.

The apparatus further includes a voltage sizing circuit 300 and a current sizing circuit 310 between the line 10 to be measured and the switch 20, and a short circuit between the switch 20 and the A / D converter 130. The circuit further includes a measurement circuit 140 and further includes a leakage current adjusting circuit 320 between the line 10 to be measured and the switch 20.

The digital logic circuit 200 provided in the resistive current detector of the present invention is a microcontrol unit (MCU) 210 that controls the switch 20, the reference signal generator 30, and the reference signal generating load 400, the reference. Reflects the phase error measured by the phase error measuring unit 220 and the phase error measuring unit 220 to measure the phase error of the signal, and is resistive by using a current converted into a digital signal by the A / D converter 130. And a calculation unit 230 for calculating a current, and the calculation unit 230 shifts the lower limit of the integration section by the magnitude of the phase error, and converts the detected current converted into a digital signal by the A / D converter 130 into a detected voltage or a detected current. The resistive current is calculated by integrating for half a period of.

In addition, the digital logic circuit 200 may further include a reference signal generator 240 for inputting a voltage and a current in phase to the reference signal generator 30.

Resistive current detection method for achieving the object of the present invention comprises the steps of (a) receiving a reference signal of the voltage and current from the reference signal generator 30, (b) the reference signal is to pass through the signal measuring circuit 100 Measuring a phase error occurring at the time; (c) receiving a detected voltage and current from the line 10 to be measured; and (d) detecting a resistive current using the phase error and the detected voltage and current. (D) step (d-1) shifting the lower limit of the integration interval by the magnitude of the phase error (d-1) (d-2) half the period of the detected current or the detected voltage Integrating to calculate the resistive current.

In another embodiment, a resistive current detection method includes (a) receiving a reference signal of voltage and current from a reference signal generating load 400, and (b) inputting the reference signal from the line under measurement 10 to the switch 20. Measuring a phase error occurring when the signal is passed through the signal measuring circuit 100 and (c) receiving the detected voltage and current from the line 10 to be measured, (d) the phase error, and Detecting a resistive current using a detection voltage and a current, wherein step (d) comprises: (d-1) moving a lower limit of an integration section by the magnitude of the phase error, (d-2) ) Calculating the resistive current by integrating the detected current for half the period of the detected voltage or detected current.

According to the present invention, it is possible to more accurately detect the magnitude of the resistive current required to determine whether the earth leakage and overcurrent, it is possible to prevent the malfunction of the electrical safety device such as an earth leakage breaker.

In addition, due to the malfunction of the electrical safety device can prevent the situation that the operation of the industrial facility should be stopped, thereby enabling more economical and safe operation of the industrial facility, including the facility equipped with the electrical safety device.

1 is a diagram showing the relationship between the magnitude and phase of an alternating current, a resistive current, a capacitive current, and a voltage.
2 is a circuit diagram of a device for detecting a conventional resistive current.
3 and 5 are circuit diagrams showing one embodiment of the resistive current detector of the present invention.
4 and 6 illustrate one embodiment of a digital logic circuit 200 in a resistive current detector of the present invention.

Hereinafter, a resistive current detector and a resistive current detection method of the present invention will be described with reference to the accompanying drawings.

3 is a view showing an embodiment of the resistive current detector of the present invention. The resistive current detector consists of a reference signal generator 30, a switch 20 and a signal measuring circuit 100.

The reference signal generator 30 is a component for inputting a reference signal for measuring a phase error to the signal measuring circuit 100 through the switch 20. The reference signal generator 30 generates a voltage and a current having the same phase, and reflects this when the phase error occurring between the voltage and the current after each voltage and current passes through the signal measuring circuit 100 is measured. Thus, the resistive current can be detected. In other words, it is a configuration for measuring in advance the phase error generated by the signal measuring circuit 100.

The reference signal generator 30 may be a device that generates analog voltage and current by itself, and may generate a reference signal using the digital logic circuit 200 of the present invention. When using the digital logic circuit 200 of the present invention, the reference signal generator 30 includes a digital to analog (D / A) converter and is generated by the reference signal generator 240 in the digital logic circuit 200. This digital voltage and current is converted into an analog signal and used to determine the phase error.

The switch 20 is configured to selectively input the reference voltage and current input from the reference signal generator 30 and the voltage and current detected from the line to be measured 10 to be selectively input to the signal measuring circuit 100. Since the voltage and current input from the reference signal generator 30 need only be input for a predetermined period, which is a degree suitable for determining a phase error, the reference of the reference signal generator 30 for a predetermined period is first input to the signal measuring circuit 100. After inputting the signal, under the control of the microcontrol unit (MCU) 210 in the digital logic circuit 200, the voltage and current detected from the line to be measured 10 are input to the signal measuring circuit 100.

The signal measuring circuit 100 measures the phase error using a reference signal input from the switch 20, and after measuring the phase error, the detected voltage input from the line under measurement 10 through the switch 20 and It is a structure for detecting a resistive current using the detection current.

The signal measuring circuit 100 includes a voltage measuring circuit 110 measuring a voltage input through a switch 20, a current measuring circuit 120 measuring a current, the voltage measuring circuit 110, and a current measuring circuit 120. A / D converter 130 that converts the voltage and current measured by the digital signal into a digital signal, and the digital logic circuit 200 that detects the resistive current using the voltage and current converted by the A / D converter 130 into the digital signal. The voltage measuring circuit 110, the current measuring circuit 120, and the A / D converter 130 use a known device.

The digital logic circuit 200 includes the MCU 210, the phase error measuring unit 220, and the calculating unit 230, which is illustrated in FIG. 4.

The MCU 210 controls the switch 20 to input a reference signal input from the reference signal generator 30 to the signal measuring circuit 100 during a predetermined period, and thereafter, input from the line under measurement 10. The detection voltage and current are input to the signal measuring circuit 100.

The phase error measuring unit 220 measures a phase error using a reference signal input from the reference signal generator 30, and measures the voltage and current measuring circuit 120 of the reference signal input through the voltage measuring circuit 110. By measuring the amount of change in the phase of the current of the reference signal input through the) may be measured the difference between the amount of change in the phase of the voltage and current, or only the relative phase difference between the voltage and the current. Based on the zero crossing point at which the voltage code of the reference signal is changed, it measures whether the power current becomes zero after a few seconds or several sample periods, and repeats this for a predetermined period to send the measurement result to the operation unit 230.

The calculator 230 calculates an average value of the phase error measurement result measured by the phase error measurer 220 for a predetermined period, and detects and detects the detected voltage converted into a digital signal input through the A / D converter 130. Calculate the resistive current using the current.

The resistive current is calculated by integrating the detected current for a half period of the detected voltage or the detected current. The lower limit and the upper limit of the integral section at the time of integration reflect the magnitude of the phase error, and if the phase error is positive, the lower limit and the upper limit of the integral section are increased in the positive direction by the magnitude of the phase error while maintaining the magnitude of the integral section. If the phase error is negative, the lower and upper limits are moved in the negative direction by the magnitude of the phase error while maintaining the magnitude of the integral section. The resistive current is calculated based on the phase of the voltage and reflects the phase error generated between the voltage and the current as shown in [Equation 1].

[Equation 1]

Igr is the resistive current and i (wt + θ) is the detection current.

Meanwhile, the reference signal generator 30 may generate a voltage and a current by itself and input it to the switch 20, or receive a voltage and current in phase from the digital logic circuit 200 and input the same into the switch 20. When the voltage and current are input from the digital logic circuit 200 and the reference signal is input to the switch 20, the digital logic circuit 200 generates a reference signal for inputting the voltage and current in phase to the reference signal generator 30. The unit 240 further includes. In addition, the reference signal generator 30 includes a D / A converter to convert the voltage and current generated by the digital logic circuit 200 into an analog signal and input the same to the switch 20. At this time, the reference signal generator 240 is controlled by the MCU 210, and inputs the reference signal to the reference signal generator 30 for a predetermined period, and after the predetermined period has passed, the detected voltage and current are measured by the signal measuring circuit ( When the input signal is input to 100, the generation of the reference signal from the reference signal generator 240 is stopped.

5 is a diagram illustrating an embodiment of the resistive current detector of the present invention. The resistive current detector of the present invention adds a voltage sizing circuit 300, a current sizing circuit 310, a ground fault sizing circuit 320 and a reference signal generating load 400 to the resistive current detector of FIG. The earth leakage measuring circuit 140 is added to the signal measuring circuit 100.

Since the switch 20, the voltage measuring circuit 110, the current measuring circuit 120, and the A / D converter 130 of FIG. 5 are the same as those of the resistive current detector of FIG. do.

The reference signal generating load 400 of the present embodiment is connected to the line under measurement 10 to convert the voltage and current measured from the line under measurement 10 and input the reference signal to the switch 20. The phase error of the voltage and the current in the detection of the resistive current is not only when the signal measuring circuit 100 including the voltage measuring circuit 110 and the current measuring circuit 120 passes, but also the detection voltage and the current in the line to be measured 10. Even in the step of inputting at 20, a phase error due to signal delay occurs. The present invention compensates even the phase error generated when the detection voltage and the current are input from the line under measurement 10 to the signal measuring circuit 100 to detect the resistive current more accurately.

The reference signal generating load 400 is composed of a resistor or a resistive element. In order to input the voltage and current of the measured line 10 generated from the power source as a reference signal, the voltage and current must be in phase, so they are input as reference signals of voltage and current without a phase change by connecting a resistor. . The reference signal generating load 400 is controlled by the MCU 210 in the digital logic circuit 200. When the reference signal is input, the reference signal generating load 400 opens the SW2 of the reference signal generating load 400 and closes the SW1 to measure the line 10 to be measured. In this case, only the reference signal generating load 400 is connected. In this case, since the voltage and the current of the line 10 to be measured have the same phase, they can be used as a reference signal of the resistive current detector. After the reference signal is input to the signal measuring circuit 100 for a predetermined period, the control voltage of the MCU 210 opens SW1 and closes SW2 so that the detected voltage and current can be input to the signal measuring circuit 100.

On the other hand, when the reference circuits by the reference signal generator 30 and the reference signal generating load 400 are input at the same time, a plurality of reference signals for phase error measurement are input, which causes confusion in the measurement. You must enter it. The MCU 210 in the digital logic circuit 200 controls the reference signal generator 30 and the reference signal generating load 400, respectively, and when the reference signal is input by the reference signal generator 30, the reference signal generating load ( When SW1 of 400 is opened and the reference signal is input by the reference signal generating load 400, the operation of the reference signal generator 240 is stopped to prevent both reference signals from being input at the same time.

Meanwhile, the resistive current detector may further include a voltage scaling circuit 300 and a current scaling circuit 310. Since a commercial power supply has a voltage of 220V and a current of a large voltage, the commercial power supply may cause excessive force in the signal measuring circuit 100, particularly the digital logic circuit 200. Therefore, it is necessary to adjust the magnitudes of the voltages and currents and lower them before inputting them. These roles are the voltage sizing circuit 300 and the current sizing circuit 310. The calculation unit 230 of the digital logic circuit 200 performing the operation of detecting the resistive current through the adjusted detection voltage and the current reflects the adjusted magnitude. For example, when the magnitude of the current is reduced to 1/10 by the current sizing circuit 310, the calculating unit 230 detects the resistive current by scaling 10 times again after performing the integral calculation.

The resistive current detector of the present invention may further include a short circuit measuring circuit 140 between the switch 20 in the signal measuring circuit 100 and the A / D converter 130. In this case, the voltage measuring circuit 110 and the current measuring circuit 120 not only determine whether the overcurrent and the current are leaking, but also by the separate ground fault measuring circuit 140 to continuously check whether the line to be measured 10 is leaked. Since it is possible to monitor, it is possible to prevent the occurrence of an accident due to a short circuit, and to determine whether a short circuit occurs more efficiently. When the ground fault measuring circuit 140 and the reference signal generating load 400 are included, the digital logic circuit 200 of the present invention is configured as shown in FIG.

On the other hand, when the ground fault measuring circuit 140 is added, a ground fault magnitude adjusting circuit 320 may be further included between the switch 20 and the line under test 10. When the magnitude of the leakage current increases rapidly, the resistance current detector may fail or malfunction, such as the A / D converter 130 or the digital logic circuit 200 in the signal measurement circuit 100 may be destroyed by the leakage current. It is necessary to reduce the magnitude of the leakage current input to the signal measuring circuit 100 through the switch 20 by the magnitude adjusting circuit 320.

One embodiment of the method for detecting a resistive current according to the present invention receives a reference signal of voltage and current from a reference signal generator 30, and detects a phase error generated when the reference signal passes through the signal measuring circuit 100. It is measured by the phase error measuring unit 220 included in the digital logic circuit 200 in the measuring circuit 100 and repeatedly measured for a predetermined period, and the average value is calculated by the calculating unit 230 to determine this as the phase error. Thereafter, the signal measuring circuit 100 receives the detected voltage and current from the line under measurement 10, detects the resistive current using the phase error, the detected voltage, and the detected current, and detects the resistive current. The current is calculated by integrating for half the period of detection voltage or detection current. The lower limit and the upper limit of the integral section at the time of integration reflect the magnitude of the phase error, and if the phase error is positive, the lower limit and the upper limit of the integral section are increased in the positive direction by the magnitude of the phase error while maintaining the magnitude of the integral section. If the phase error is negative, the lower and upper limits are moved in the negative direction by the magnitude of the phase error while maintaining the magnitude of the integral section. The resistive current is calculated by reflecting the generated phase error. In this case, the resistive current may be detected by correcting an error caused by the phase delay of the voltage and the current generated by the signal measuring circuit 100.

On the other hand, another embodiment of the resistive current detection method according to the present invention receives a reference signal of the voltage and current from the reference signal generator 30, generates a reference signal by the reference signal generating load 400, the line to be measured Phase errors occurring when power and current are input from the switch 10 to the switch 20 and when passing through the signal measuring circuit 100 are measured. The average value of the measured value obtained by repeating the measurement for a predetermined period is determined as the phase error, after which the detected voltage and current are input from the line to be measured 10, and the resistive current is obtained using the phase error, the detected voltage, and the detected current. Detect. The resistive current is calculated by integrating the detected current for half the period of the detected voltage or the detected current. The lower limit and the upper limit of the integral section at the time of integration reflect the magnitude of the phase error, and if the phase error is positive, the lower limit and the upper limit of the integral section are increased in the positive direction by the magnitude of the phase error while maintaining the magnitude of the integral section. If the phase error is negative, the lower and upper limits are moved in the negative direction by the magnitude of the phase error while maintaining the magnitude of the integral section. The resistive current is calculated by reflecting the generated phase error. In this case, the resistive current is detected more accurately by correcting not only the phase delay of the voltage and current generated by the signal measuring circuit 100 but also the error generated when detecting the voltage and the current from the line 10 to be measured. Can be detected.

10 measuring line 20 switch
30 reference signal generator 100 signal measurement circuit
110 Voltage measuring circuit 120 Current measuring circuit
130 A / D converter 140 Earth leakage measuring circuit
200 Digital Logic Circuits 210 Micro Control Units
220 phase error measurement unit 230 calculation unit
240 reference signal generator 300 voltage scaling circuit
310 current sizing circuit 320 earth leakage sizing circuit
400 reference signal generating load

Claims (15)

A device for detecting a resistive current for use in an electrical safety device,
A reference signal generator 30 for inputting a reference signal for measuring phase error to the switch 20;
A switch 20 controlled by the signal measuring circuit 100 and selectively inputting the voltage and current detected from the reference signal of the reference signal generator 30 or the line under measurement to the signal measuring circuit 100; And
A signal measuring circuit (100) for measuring a phase error using a reference signal input from the switch (20) and detecting a resistive current using the phase error and the detected voltage and current;
Resistive current detector comprising
The method of claim 1, wherein the signal measuring circuit 100
A voltage measuring circuit 110 measuring a voltage input through the switch 20;
A current measuring circuit 120 measuring a current input through the switch 20;
An analog-to-digital (A / D) converter for converting the voltage and current measured by the voltage measuring circuit 110 and the current measuring circuit 120 into digital signals; And
A digital logic circuit 200 for detecting a resistive current using the voltage and current converted from the A / D converter 130 into a digital signal;
Resistive current detector comprising a
The method of claim 2, wherein the reference signal generator 30 includes a digital to analog (D / A) converter, and converts the voltage and current generated by the digital logic circuit 200 into a reference signal by D / A conversion. Resistive current detector, characterized in that
2. The resistive current detector of claim 1, further comprising a reference signal generating load 400 connected to the line to be measured 10 so that voltage and current in phase are input to the switch 20 as a reference signal.
The method according to claim 4, wherein the reference signal of the reference signal generator 30 or the reference signal generated by the reference signal generating load 400 by the control of the signal measuring circuit 100 is alternative to the switch 20 Resistive current detector, characterized in that input
The resistive current detector of claim 1, further comprising a voltage sizing circuit 300 and a current sizing circuit 310 between the line under test 10 and the switch 20.
The resistive current detector of claim 2, further comprising a short circuit measuring circuit 140 between the switch 20 and the A / D converter 130.
8. The resistive current detector as recited in claim 7, further comprising a short circuit sizing circuit (320) between the line to be measured (10) and the switch (20).
The method of claim 2, wherein the digital logic circuit 200
A microcontrol unit (MCU) 210 for controlling the switch 20, the reference signal generator 30, and the reference signal generating load 400;
A phase error measuring unit 220 measuring a phase error of the reference signal; And
A calculator 230 reflecting the phase error measured by the phase error measurer 220 and calculating a resistive current using a current converted into a digital signal by the A / D converter 130;
Resistive current detector comprising a
The method of claim 9, wherein the calculation unit 230 moves the lower limit of the integral section by the phase error and integrates the detected current converted into a digital signal by the A / D converter 130 for a half period of the detected voltage or the detected current, thereby resisting the resistance. Resistive Current Detector, Computing Current
10. The resistive current detector of claim 9, wherein the digital logic circuit 200 further comprises a reference signal generator 240 for inputting a voltage and current in phase to the reference signal generator 30.
A method for detecting resistive currents for use in electrical safety devices,
(a) receiving a reference signal of voltage and current from the reference signal generator 30 via the switch 20;
(b) measuring a phase error occurring when the reference signal passes through the signal measuring circuit 100
(c) controlling the switch 20 to receive the detected voltage and current from the line to be measured 10;
(d) detecting a resistive current using the phase error, the detected voltage, and the current;
The method of claim 12, wherein step (d)
(d-1) moving a lower limit of an integration section by the phase error by the magnitude of the phase error
(d-2) calculating the resistive current by integrating the detected current for half the period of the detected voltage or the detected current;
A method for detecting resistive currents for use in electrical safety devices,
(a) receiving a reference signal of voltage and current from a reference signal generating load 400
(b) measuring a phase error occurring when the reference signal is input to the switch 20 from the line under measurement 10 and passes through the signal measuring circuit 100;
(c) receiving the detected voltage and current from the line to be measured 10;
(d) detecting a resistive current using the phase error, the detected voltage, and the current;
The method of claim 14, wherein step (d)
(d-1) moving a lower limit of an integration section by the phase error by the magnitude of the phase error
(d-2) calculating the resistive current by integrating the detected current for half the period of the detected voltage or the detected current;

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