KR102173348B1 - Earth leakage circuit breaker(elcb) and method for detecting leakage current - Google Patents

Abstract

The present invention relates to an earth leakage circuit breaker, comprising: a calculation unit for calculating a magnitude, a peak value, and an effective value of a fundamental wave from a current signal detected by an image current transformer; and the detected current signal based on a ratio of the calculated peak value. It characterized in that it comprises a control unit for determining whether or not the first leakage current having a preset waveform, and outputting a trip signal based on a ratio of the magnitude of the fundamental wave and the effective value according to the determination result. .

Description

Earth leakage breaker and its leakage current detection method {EARTH LEAKAGE CIRCUIT BREAKER(ELCB) AND METHOD FOR DETECTING LEAKAGE CURRENT}

The present invention relates to an earth leakage circuit breaker and a leakage current detection method thereof.

In modern houses, electricity is a very important energy source that is indispensable for the convenience of life, but it is also a very dangerous entity that can cause property damage or serious personal injury by causing electric fire or electric shock. Therefore, the electrical regulations stipulate to install an overcurrent breaker (MCCB: Mold Cased Circuit Breaker) or an earth leakage breaker (ELCB: Earth Leakage Circuit Breaker, GFCI: Ground Fault Circuit Interrupter) at the entrance of a house or building.

A typical earth leakage circuit breaker is amplified by an amplifier when an earth leakage signal is detected through a zero current transformer (ZCT). The amplified earth leakage signal is compared with the reference voltage set by the level discriminator, and if it is greater than the reference voltage, the trip generator transmits the trip signal to the trip unit. The trip unit blocks the power circuit to protect the load and the human body in case of a short circuit.

Meanwhile, a conventional earth leakage circuit breaker classifies any one of an earth leakage, a ground fault, and an equilibrium using a fundamental wave, a third harmonic, and a peak value. However, in the case of the balanced current generated when the motor is started, the output waveform due to the saturation of the image current transformer (ZCT) is very similar to the A-type (135°) leakage current (pulsating current including a DC component). Therefore, in the case of high frequency effects such as industrial sites using a motor or facilities using a large number of DC loads, the earth leakage circuit breaker is difficult to distinguish between the A type (135 ˚) leakage current and the balanced current. That is, even in the case of the balanced current, there is a problem that the earth leakage breaker is blocked.

The present invention for solving the above-described problem is to determine whether the current signal detected through the image current transformer corresponds to the A-type leakage current by using the ratio of the calculated peak value, and when the A-type leakage current is also determined, the fundamental wave The purpose of this is to improve the detection accuracy of the leakage current by using the ratio of the magnitude of the RMS value and the RMS value.

The present invention relates to an earth leakage circuit breaker, comprising: a calculation unit for calculating a magnitude, a peak value, and an effective value of a fundamental wave from a current signal detected by a video current transformer; and the detected current signal based on the calculated ratio of the peak value. It characterized in that it comprises a control unit for determining whether or not the first leakage current having a preset waveform, and outputting a trip signal based on a ratio of the magnitude of the fundamental wave and the effective value according to the determination result. .

In an embodiment, the ratio of the calculated peak value is a ratio of a peak value of a positive polarity and a peak value of a negative polarity calculated from the detected current signal.

In an embodiment, the calculation unit includes an analog-digital converter (ADC) module that samples the detected current signal and converts it into a digital signal in a time domain, and the converted digital signal is discrete Fourier. A DFT module that performs a Discrete Fourier Transform (DFT) and outputs a digital signal in a frequency domain, and a calculation module that calculates the magnitude, RMS, and peak value of a fundamental wave from the discrete Fourier transformed digital signal. do.

을 이용하여 산출할 수 있고, 여기서, X는 상기 기본파의 크기와 상기 실효값의 비율이고, 상기 기본파의 크기와 상기 실효값의 비율이 기 설정된 임계값보다 큰 경우, 트립 신호를 출력하는 것을 특징으로 한다.In an embodiment, the ratio (X) of the magnitude of the fundamental wave and the effective value is,

Wherein, X is the ratio of the magnitude of the fundamental wave and the RMS value, and when the ratio of the magnitude of the fundamental wave and the RMS value is greater than a preset threshold, outputting a trip signal It features.

In an embodiment, the control unit determines whether the detected current signal corresponds to a second leakage current having a waveform different from a preset waveform, based on the calculated ratio of the peak value, and the determination result Accordingly, based on the magnitude of the fundamental wave, the peak value, and the magnitude of the third harmonic of the detected signal, a trip signal is output.

Meanwhile, in an embodiment, when the calculated ratio of the peak value exceeds a reference ratio, the control unit determines it as the first leakage current, and when the calculated ratio of the peak value is less than the reference ratio, the It is characterized in that it is determined by the second leakage current.

Furthermore, it is characterized in that the reference ratio is 1.

The present invention relates to a leakage current detection method, wherein in an earth leakage circuit breaker, a first step of calculating a magnitude, a peak value, and an effective value of a fundamental wave from a current signal detected by an image current transformer, and a ratio of the calculated peak value A second step of determining whether the detected current signal is a first leakage current having a preset waveform, based on the determination result, the control unit based on the ratio of the magnitude of the fundamental wave and the effective value, It characterized in that it comprises a third step of outputting a trip signal.

Meanwhile, in an embodiment, the ratio of the calculated peak value is a ratio of a positive polarity peak value and a negative polarity peak value calculated from the detected current signal.

In addition, the first step is a step 1-1 in which an analog-digital converter (ADC) module samples the detected current signal and converts the detected current signal into a digital signal in the time domain, Discrete Fourier (DFT). Transform) module performs discrete Fourier transform (DFT) and outputs the digital signal in the frequency domain as a frequency domain, and the calculation module performs a fundamental wave amplitude and an effective value from the discrete Fourier transformed digital signal. And it characterized in that it comprises a 1-3 step of calculating the peak value.

을 이용하여 산출할 수 있고, 여기서 X는 상기 기본파의 크기와 상기 실효값의 비율을 의미하고, 상기 기본파의 크기와 상기 실효값의 비율이 기 설정된 임계값보다 큰 경우, 트립 신호를 출력하는 것을 특징으로 한다.In an embodiment, the ratio between the magnitude of the fundamental wave and the effective value is

Wherein X means the ratio of the magnitude of the fundamental wave and the RMS value, and when the ratio between the magnitude of the fundamental wave and the RMS value is greater than a preset threshold, a trip signal is output. Characterized in that.

Further, the second step is, based on the calculated ratio of the peak value, the detected current signal is applied to any one of a first leakage current having a preset waveform and a second leakage current having a waveform different from the preset waveform. It characterized in that it comprises a step 2-1 of determining whether or not.

In an embodiment, in the third step, a trip signal is output based on at least one of the peak value and a third harmonic level of the detected current signal according to the determination result of step 2-1. It characterized in that it includes a step 3-1.

In an embodiment, in step 2-1, when the calculated ratio of the peak value exceeds the reference ratio, it is determined as the first leakage current, and the calculated ratio of the peak value is less than the reference ratio , It is characterized in that it is determined as the second leakage current.

The present invention relates to an earth leakage circuit breaker and a leakage current detection method, and it is possible to determine whether a current signal detected through an image current transformer corresponds to a type A leakage current by using a ratio of a calculated peak value. In addition, when it is determined as the A-type leakage current, there is an effect of improving the classification accuracy between the A-type leakage current and the balanced current by using the ratio between the magnitude of the fundamental wave and the effective value.

1 is a block diagram showing the configuration of an earth leakage circuit breaker according to an embodiment of the present invention.
2 is a block diagram showing a configuration of a calculation unit of an earth leakage circuit breaker according to an embodiment of the present invention.
3A is a reference diagram for explaining an AC type leakage current.
3B is a reference diagram for explaining the A-type leakage current.
3C is a reference diagram for explaining balance and leakage current.
4 is a flowchart of a leakage current detection method according to an embodiment of the present invention.
5 is a flowchart of a method of detecting a type A leakage current of an earth leakage circuit breaker according to an embodiment of the present invention.
6 is a flowchart of a method of detecting an AC type leakage current of an earth leakage circuit breaker according to an embodiment of the present invention.

Hereinafter, embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, but the same or similar components are denoted by the same or similar reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and "unit" for components used in the following description are given or used interchangeably in consideration of only the ease of preparation of the specification, and do not have meanings or roles that are distinguished from each other by themselves. In addition, in describing the embodiments disclosed in the present specification, when it is determined that a detailed description of related known technologies may obscure the subject matter of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are for easy understanding of the embodiments disclosed in the present specification, and the technical idea disclosed in the present specification is not limited by the accompanying drawings, and all modifications included in the spirit and scope of the present invention It should be understood to include equivalents or substitutes.

In addition, expressions in the singular include plural expressions unless the context clearly indicates otherwise.

The present invention relates to an earth leakage circuit breaker and a leakage current detection method thereof, wherein the detected current signal is classified into an AC type leakage current signal and an A type leakage current signal, and in particular, when it is determined as an A type leakage current, an A type Leakage current and equilibrium current can be accurately discriminated.

Here, the type AC leakage current is a current of an alternating current (AC) component of a pure sine wave that does not include a direct current (DC) component, and has a shape of a waveform including both positive and negative polarities. When the input signal is determined to be an AC type leakage current, the earth leakage breaker outputs a trip signal. Meanwhile, the Type A leakage current includes an alternating current pulsating current with a direct current (DC) component and may have a half-wave waveform including either a positive polarity or a negative polarity. Even when the input signal is determined to be an A-type leakage current, the earth leakage breaker outputs a trip (TRIP) signal.

A method of classifying AC-type current and A-type current, that is, different types of current, will be described in detail below.

Meanwhile, a circuit breaker and a method of detecting a leakage current thereof according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram showing the configuration of an earth leakage circuit breaker according to an embodiment of the present invention.

Referring to FIG. 1, the earth leakage circuit breaker according to the present invention may include a current detection unit 100, a calculation unit 200, and a control unit 300.

First, the current detection unit 100 outputs a leakage current detection signal from the circuit. To this end, the current detection unit 100 includes a ring-shaped core installed to pass through the circuit as shown in FIG. 1 and a secondary winding wound around the core and outputting a leakage current detection signal. It may include a configured image current transformer (ZCT; zero current transformer).

Here, the image current transformer (ZCT) is a device capable of detecting a leakage current, and is used in combination with a ground fault relay to cut off a circuit when a short circuit occurs. In this case, the principle of operation of the image current transformer is that the sum of the electric vectors in the electric line should theoretically be '0' in the normal state, but the sum of the vectors does not become zero when a single-line ground fault (short circuit) occurs. In other words, there is no problem as the current flowing through the ZCT and flowing through the line is the same as the current flowing from the ZCT to the load in the normal state (no leakage occurs). However, when a ground fault (leakage) occurs in the line, a difference in current entering and leaving the load occurs, and the current equal to this difference is the ground fault current (leakage). That is, the ground fault current can be detected by the ZCT.

Meanwhile, from the current signal detected by the calculator 200 and the image current transformer, the magnitude, peak value, and effective value of the fundamental wave of the detected signal may be calculated.

Here, the magnitude of the fundamental wave means the magnitude of the fundamental frequency component in the system. In addition, the effective value means the square root of the average value over one period of the instantaneous value of the input AC current signal. Also, the peak value means the maximum value of the detected current signal. Meanwhile, detailed meanings of the magnitude, peak value, and effective value of the fundamental wave will be described below with reference to FIG. 2.

On the other hand, the control unit 300 may control not only each component constituting the earth leakage circuit breaker, but also generally control the overall operation of the device.

In addition, the controller 300 may determine whether the detected current signal is a first current having a preset waveform, based on the calculated ratio of the peak value. Further, according to the determination result, a trip signal may be output based on a ratio between the magnitude of the fundamental wave and the effective value.

Here, the ratio of the calculated peak value may be calculated as a ratio of the peak value of the positive polarity and the peak value of the negative polarity calculated from the detected current signal. For example, the ratio of the calculated peak value is a value calculated by dividing the peak value of the positive polarity by the peak value of the negative polarity.In the case of an AC current in which the peak value of the positive polarity and the peak value of the negative polarity are the same , The ratio becomes 1.

2 is a block diagram showing in more detail the calculation unit 200 of an earth leakage circuit breaker according to an embodiment of the present invention.

Referring to FIG. 2, the calculation unit 200 of the earth leakage circuit breaker according to an embodiment of the present invention includes an analog-digital converter (ADC) module 210, a Discrete Fourier Transform (DFT) module 220, and a calculation module ( 230) may be included.

First, of the components included in the calculation unit 200, the ADC module 210 may sample a current signal detected by the current detection unit 100 and convert it into a digital signal in a time domain. In this case, the ADC module 110 is a chip (I/C) or module that converts a continuous analog signal into a digital signal composed of 0s and 1s.

The DFT module 220 performs a discrete Fourier transform on the digital signal in the time domain transformed by the ADC module 210 and outputs the digital signal in the frequency domain. In this case, the discrete Fourier transform refers to Fourier transform of a function sampled at regular intervals.

On the other hand, the calculation module 230 may calculate the magnitude, the rms value, and the peak value of the fundamental wave from the digital signal in the frequency domain of the detected current signal output through the ADC module 210 and the DFT module 200. have.

Here, the magnitude of the fundamental wave may mean the magnitude of a frequency component that is fundamental to the system. For example, Europe uses 50Hz and Korea uses 60Hz. In this case, Europe may be the size of the 50Hz frequency component. And in Korea, it may be the size of the 60Hz frequency component.

The root-mean-square value means the square root of the average value over one period of the instantaneous value of the input AC current signal. That is, in the case of a sinusoidal wave, it is 0.707 times the maximum amplitude.

The peak value means the maximum value of the detected current signal. In addition, the peak ratio represents the ratio between the positive polarity peak value and the negative polarity peak value. For example, in the case of a sine waveform with positive and negative polarity based on 0 (Zero), the peak value of the positive polarity and the peak value of the negative polarity have the same magnitude, so the peak ratio is It becomes 1.

The control unit 300 according to an embodiment of the present invention determines whether the detected signal corresponds to a first current of a preset waveform based on a ratio of the peak value calculated by the calculation unit 200. Here, the first current may include an A-type leakage current. However, it is not limited to the A-type leakage current, and may include a current having another waveform.

Here, the ratio of the peak value means the ratio of the peak value of the positive polarity and the peak value of the negative polarity, that is, the peak ratio, as described above.

At this time, when the input signal is determined to be an A-type leakage current based on the peak ratio, the controller 300 generates a trip signal based on the ratio of the magnitude and RMS value of the fundamental wave calculated by the calculation unit 200. Can be printed.

3A to 3C are reference diagrams for explaining AC current, A-type leakage current, balance and leakage current.

3A is an AC type (Type AC) leakage current, a pure sinusoidal current of an alternating current (AC) component that does not include a direct current (DC) component, and has a shape of a waveform including both positive and negative polarities. . If it is determined as an AC type leakage current, the earth leakage circuit breaker can output a trip signal.

Meanwhile, FIG. 3B shows a type A leakage current, which includes an alternating current pulsating current with a direct current (DC) component, and has the form of a half-wave waveform including either positive polarity or negative polarity. I can. Here, FIG. 3B is an example of the A-type leakage current, and may include a waveform of another type. In addition, when it is determined as an A-type leakage current, the earth leakage circuit breaker may output a trip signal.

As shown in FIG. 3B, the A-type leakage current (0˚, 90˚, 135˚) may have a phase control method using a silicon controlled rectifier (SCR). At this time, the waveform of the 135˚A-type leakage current, which has the highest high-frequency ratio among the phases of 0˚, 90˚, and 135˚ of the current, is similar to the balanced current, so it is difficult to distinguish it. That is, if the detected current signal is determined to be an A-type leakage current even though the detected current signal is a balanced current, the earth leakage circuit breaker may output a trip signal, thereby causing a malfunction of the earth leakage circuit breaker.

On the other hand, Figure 3c shows the waveforms of the balance current and ground current.

Balanced current is the waveform generated when the inverter starts, and the sum of the current entering and exiting is ideally 0 (Zero), and the output waveform should not be output. However, the waveform is output at the point of crossing the zero point due to physical phenomena such as impedance mismatch and ZCT saturation.

Furthermore, the equilibrium current is the current flowing in the normal state, and unlike the leakage or ground fault current, the earth leakage breaker should not trip. Therefore, the earth leakage breaker must accurately distinguish between the state of generating the balanced current and the state of generating the leakage current in the circuit.

On the other hand, ground fault current is a waveform current that occurs when a ground fault occurs, and its peak value is very high. Therefore, by using the size of the peak value, it is possible to distinguish between the ground fault current and the leakage current. In this case, the ground fault current is when a part of a wire or a converter is directly or indirectly connected to the ground (ground), that is, a voltage that is dangerous to the outside of the converter or device due to the influence of an arc or conductive material due to deterioration of the insulation between the converter and the ground. Appears or means a state in which current flows. Such earth fault current may cause electric shock to the human body, electric leakage, fire, or damage to equipment. When ground current occurs, the earth leakage breaker outputs a trip signal.

Meanwhile, the balanced current according to an exemplary embodiment may have a waveform of the shape shown in FIG. 3C. However, when the balanced current is actually measured, the shape of the waveform may be different from the waveform of the balanced current shown in FIG. 3C.

As an example, referring to [Table 1] below, unlike FIG. 3C, a section in which only a positive polarity waveform (or a negative polarity waveform) is detected may exist as a waveform of an actual balanced current. The waveform on the right of Table 1 represents the balanced current in which only positive polarity waveforms exist.

Referring to [Table 2] below, it can be seen that in the case of a balanced current in which only a positive polarity waveform exists, it is not easy to distinguish it from an A-type leakage current of 135°. Therefore, even though the detected current is a balanced current that should not cause the earth leakage breaker to trip, it may be mistaken for a leakage current and an error in which a trip may occur.

Therefore, the control unit of the earth leakage circuit breaker according to the present invention can distinguish between the A-type leakage current and the balanced current including only the positive polarity by setting the ratio of the magnitude and the effective value of the fundamental wave as variables.

Referring to [Table 2], when comparing the waveforms of the A-type leakage current (135˚) and the balanced current having only positive polarity, the A-type leakage current (135˚) is non-zero compared to the waveform of the balanced current. It can be seen that the area of the waveform in the duration Δt of the waveform having a value, that is, the magnitude of the fundamental wave has a larger value. Therefore, it is possible to distinguish the waveforms of the A-type leakage current (135°) and the balanced current by comparing the ratio of the magnitude and the effective value of the fundamental wave with a preset threshold.

If the ratio of the magnitude of the fundamental wave and the rms value is designated as an arbitrary variable X, it is as shown in [Equation 1].

That is, in Equation 1, the A-type leakage current (135°) and the equilibrium current can be distinguished by using a characteristic in which the size of the fundamental wave and the ratio (X) of the effective value have a larger value as the area of the signal increases.

Meanwhile, in the above description, the earth leakage breaker for detecting the type A leakage current has been described. Hereinafter, a method of detecting a leakage current of an earth leakage circuit breaker will be described with reference to FIGS. 4 to 6. That is, let's take a closer look at the A-type leakage current detection method and the AC-type leakage current detection method of an earth leakage breaker.

4 is a flowchart of a method of detecting a leakage current of an earth leakage circuit breaker according to an embodiment of the present invention.

First, the calculation unit 200 calculates a magnitude, a peak value, and an effective value of the fundamental wave from the current signal detected by the image current transformer (ZCT) (S100).

Here, the magnitude, peak value, and effective value of the fundamental wave are the same as the meanings of the terms described above, and thus redundant descriptions will be omitted.

Meanwhile, a preprocessing process for calculating the magnitude, peak value, and effective value of the fundamental wave from the detected current signal is as follows.

The current detection unit 100 detects a current signal from the image current transformer ZCT.

The ACD module 210 samples the detected current signal and converts it into a digital signal in the time domain. The DFT module 220 performs Discrete Fourier Transform on the converted digital signal and outputs the converted digital signal as a frequency domain digital signal.

That is, the magnitude, the effective value, and the peak value of the fundamental wave may be calculated through the digital signal in the frequency domain of which the detected current signal is output through the ADC module 210 and the DFT module 220.

The controller 300 of the earth leakage circuit breaker according to the present invention may determine whether the detected current corresponds to the A-type leakage current based on the calculated peak value ratio, that is, the peak ratio (S200). Meanwhile, the controller 300 may also determine whether or not the detected current corresponds to an AC type leakage current based on the peak ratio. The case of AC leakage current will be described in detail below.

Meanwhile, the step S200 may be a step of determining whether the detected current is an A-type leakage current based on the peak ratio. For example, in the case of a sine waveform with positive and negative polarity based on 0 (Zero), the peak value of the positive polarity and the peak value of the negative polarity have the same magnitude, so the peak ratio is It becomes 1. That is, the detected current may be determined to correspond to an AC-type leakage current when the peak ratio is 1, and to correspond to an A-type leakage current when the peak ratio is greater than 1. However, this is an example of the present invention, and the reference value may be set differently.

Meanwhile, when it is determined that the detected current signal corresponds to the A-type leakage current, a trip signal may be output based on the ratio of the magnitude of the fundamental wave and the effective value (S300).

Therefore, whether or not the detected current signal corresponds to the A-type leakage current may be determined according to the ratio of the magnitude and the effective value of the fundamental wave. For example, according to the ratio of the magnitude and the effective value of the fundamental wave, the A-type leakage current (135°) and the balanced current may be classified.

The ratio (X) of the magnitude of the fundamental wave and the effective value is as shown in [Equation 1].

That is, according to the above [Equation 1], the controller 300 uses a characteristic in which the size of the fundamental wave and the ratio (X) of the RMS value are larger as the area of the waveform of the current signal increases. Current (135˚) and equilibrium current can be distinguished.

5 is a diagram showing in detail a method of detecting a type A leakage current according to step S300.

First, if the control unit 300 determines that the detected current corresponds to the A-type leakage current based on the calculated ratio of the peak value, that is, the peak ratio, the RMS value is compared with a preset value to generate a trip of the earth leakage breaker. Whether or not it can be determined (S310).

In the A-type leakage current, in which only one polarity waveform of positive or negative polarity is output, the entire waveform (for example, a sine wave) is output, unlike AC-type leakage current that compares the magnitude of the fundamental wave, the RMS value ( RMS) can be compared with a preset value to determine whether to trip.

That is, since the A-type leakage current is a waveform by SCR phase angle control, and it is limited to compare waveforms with only the magnitude of the fundamental wave, the magnitude of the RMS value can be utilized.

If it is determined that the effective value is greater than the set value according to the determination result of step S310, it may be determined whether the detected current signal corresponds to the balanced current (S320). That is, when it is determined that the third harmonic of the detected current signal is larger than the set value by comparing the calculated third harmonic with a preset set value (eg, 70%), the detected current is a balanced current. Does not output trip signal.

However, when the calculated third harmonic is smaller than a preset set value (eg, 70%), it is necessary to distinguish between the A-type leakage current (135°) and a similar type of balanced current (see Table 2).

Therefore, the control unit of the present invention, based on the ratio of the magnitude of the fundamental wave and the effective value (X in Equation 1, but an arbitrary variable is denoted as'PF' in FIG. 5), the balanced current and the A-type leakage current ( 135˚) can be distinguished (S330).

When the ratio (X) of the magnitude of the fundamental wave and the rms value has a value greater than a preset value (for example, 20%), it is determined as an A-type leakage current (135˚), and thus a trip signal can be output (S340). ). However, when the ratio (X) of the magnitude of the fundamental wave and the rms value is less than a preset value (eg 20%), the detected current corresponds to the balanced current and the earth leakage breaker does not trip.

At this time, the ratio between the magnitude of the fundamental wave and the rms value was described as X or PF as an arbitrary variable. This means the same variable, only there are differences in notation.

Meanwhile, according to step S200, the controller 300 according to the present invention may determine the detected current as an AC type leakage current based on the calculated peak ratio. In this case, a trip signal can be output even if it corresponds to an AC type leakage current based on a preset condition.

6 is a flowchart of a method of detecting an AC type leakage current when it is determined as an AC type leakage current in step S200.

First, when the current detected in step S200 is determined to be an AC-type leakage current based on the peak ratio, it is possible to determine whether or not a trip occurs by comparing the magnitude of the fundamental wave with a preset value (S410).

Specifically, when the ratio between the magnitude of the fundamental wave and the sensitivity current is greater than or equal to a preset ratio, it may be determined whether it corresponds to either a ground fault current or a balanced current. For example, when the sensitivity current is 100mA and the magnitude of the fundamental wave is 80mA, the ratio is 80% when calculated. Therefore, since it has a value greater than 70%, it is necessary to determine whether it corresponds to a ground fault current. However, if the magnitude of the fundamental wave does not reach 70%, it does not correspond to the leakage current and does not output a trip signal.

Meanwhile, when the magnitude of the fundamental wave is greater than a preset ratio (eg, 70%), it may be determined whether the detected current signal corresponds to a ground fault current. For example, by comparing the calculated peak value and the set value, it may be determined as a ground fault current according to whether the peak value has a larger value than the set value (S420).

Meanwhile, when the peak value of the detected current signal is smaller than the set value, it may be determined whether the detected current signal corresponds to the balanced current. It may be determined whether the current signal corresponds to a balanced current by using the third harmonic of the detected current signal (S430).

At this time, when it is determined that the magnitude of the third harmonic is smaller than the set value, the controller may output a trip signal (S440). However, when the magnitude of the third harmonic is larger than the set value, it may be determined as a balanced current and set so that the earth leakage breaker does not trip.

Accordingly, in the present invention, when the detected current is determined as an AC-type leakage current based on the peak ratio, the leakage current can be determined using the magnitude, peak value, and third harmonic of the fundamental wave.

On the other hand, the present invention distinguishes leakage current, ground fault current and theoretical equilibrium current by using the effective value and the third harmonic when the detected current is determined as the A-type leakage current based on the peak ratio, and additionally The leakage current and the actual balanced current can be classified using the ratio of the size and the effective value to prevent malfunction of the earth leakage breaker.

The present invention described above can be implemented as a computer-readable code in a medium on which a program is recorded. The computer-readable medium includes all types of recording devices storing data that can be read by a computer system. Examples of computer-readable media include HDD (Hard Disk Drive), SSD (Solid State Disk), SDD (Silicon Disk Drive), ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc. There is also a carrier wave (eg, transmission over the Internet). In addition, the computer may include a control unit of the terminal. Therefore, the detailed description above should not be construed as restrictive in all respects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

100: current detection unit
200: calculation unit
210: ADC (Analog-Digital Converter) module
220: Discrete Fourier Transform (DFT) module
230: output module
300: control unit

Claims (14)

A calculation unit that calculates a magnitude, a peak value, and an effective value of the fundamental wave from the current signal detected by the image transformer; And
Based on the calculated ratio of the peak value, it is determined whether the detected current signal is a first leakage current having a preset waveform,
And a controller configured to output a trip signal based on a ratio of the magnitude of the fundamental wave and the effective value according to the determination result, and
The control unit,
And determining whether the detected current signal corresponds to a second leakage current having a waveform different from a preset waveform, based on the calculated ratio of the peak values. The method of claim 1,
The ratio of the calculated peak value is,
An earth leakage circuit breaker comprising a ratio of a peak value of a positive polarity and a peak value of a negative polarity calculated from the detected current signal. The method of claim 1,
The calculation unit,
An analog-digital converter (ADC) module for sampling the detected current signal and converting it into a digital signal in a time domain;
A DFT module that performs a Discrete Fourier Transform (DFT) on the converted digital signal and outputs the converted digital signal as a frequency domain digital signal; And
And a calculation module for calculating a magnitude, an effective value, and a peak value of a fundamental wave from the discrete Fourier-transformed digital signal. The method of claim 1,
The ratio between the magnitude of the fundamental wave and the rms value is,

Can be calculated using
Here, X means the ratio of the magnitude of the fundamental wave and the effective value,
When the ratio of the magnitude of the fundamental wave and the effective value is greater than a preset threshold, a trip signal is output. The method of claim 1,
The control unit,
And outputting a trip signal based on the magnitude of the fundamental wave, the peak value, and the magnitude of the third harmonic of the detected signal according to a result of determining the first and second leakage currents. The method of claim 5,
The control unit,
When the ratio of the calculated peak value exceeds the reference ratio, it is determined as the first leakage current,
When the ratio of the calculated peak value is less than or equal to the reference ratio, it is determined as the second leakage current. The method of claim 6,
An earth leakage circuit breaker, characterized in that the reference ratio is 1. In the leakage current detection method of an earth leakage breaker,
A first step of calculating a magnitude, a peak value, and an effective value of a fundamental wave from the current signal detected by the image transformer;
A second step of determining whether the detected current signal is a first leakage current having a preset waveform based on the calculated ratio of the peak values; And
In accordance with the determination result, a third step of the controller outputting a trip signal based on the ratio of the magnitude of the fundamental wave and the effective value; and
The second step,
Based on the calculated ratio of the peak value, a first leakage current having a preset waveform and a second leakage current having a waveform different from the preset waveform are determined based on the ratio of the calculated peak value. 2-1 step; leakage current detection method comprising a. The method of claim 8,
The ratio of the calculated peak value is,
A leakage current detection method, characterized in that it is a ratio of a positive polarity peak value and a negative polarity peak value calculated from the detected current signal. The method of claim 8,
The first step,
Step 1-1 of an analog-digital converter (ADC) module sampling the detected current signal and converting it into a digital signal in a time domain;
A step 1-2 of performing, by a Discrete Fourier Transform (DFT) module, the converted digital signal as a digital signal in a frequency domain by performing a Discrete Fourier Transform (DFT); And
And a first-3 step of calculating, by a calculation module, the magnitude, rms value, and peak value of a fundamental wave from the discrete Fourier-transformed digital signal. The method of claim 8,
The ratio between the magnitude of the fundamental wave and the rms value is,

Can be calculated using
Here, X means the ratio of the magnitude of the fundamental wave and the effective value,
And outputting a trip signal when the ratio of the magnitude of the fundamental wave and the effective value is greater than a preset threshold value. delete The method of claim 8,
The third step,
And a step 3-1 of outputting a trip signal based on at least one of the peak value and the magnitude of the third harmonic of the detected current signal according to the determination result of step 2-1. Leakage current detection method. The method of claim 8,
The step 2-1,
When the ratio of the calculated peak value exceeds the reference ratio, it is determined as the first leakage current,
When the ratio of the calculated peak value is less than or equal to the reference ratio, it is determined as the second leakage current.

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