KR102116030B1 - Switchboard with secondary open monitoring of current transformer - Google Patents

Abstract

In addition to the notification that the current transformer secondary terminal is open, a secondary switch open / closed switchgear for a current transformer configured to proactively cope with the danger of the secondary terminal opening of the current transformer is disclosed by notifying the user that it is in a dangerous state that can be opened. The transformer secondary side open monitoring switchgear comprises: a pressure reducer which is connected to the current transformer secondary side first terminal and the second terminal, respectively, to decompress the voltage of the secondary terminal of the current transformer; A comparator for outputting a first square wave signal when the reduced voltage output from the pressure reducer is within a threshold voltage range, and outputting a second square wave signal when the reduced voltage is higher than the threshold voltage range; An analog-to-digital converter converting a first square wave signal into a first digital signal and converting a second square wave signal into a second digital signal; And (i) when the first digital signal is provided from the analog-to-digital converter, determines that the secondary terminal of the current transformer is in an open danger state and outputs a first control signal, and (ii) a second digital from the analog-to-digital converter. When the signal is provided, the control unit determines that the secondary terminal of the current transformer is in an open state and outputs a second control signal.

Description

SWITCHBOARD WITH SECONDARY OPEN MONITORING OF CURRENT TRANSFORMER}

The present invention relates to the secondary side open monitoring switchgear of the current transformer, and more specifically, to inform the user that the secondary side terminal of the current transformer is in a dangerous state that can be opened in addition to the notification that the current side of the current transformer is open, preemptively to the risk of opening the secondary side terminal of the current transformer. It is related to the secondary side open monitoring switchgear configured to cope with this.

In general, a current transformer (CT) is a device that obtains a small current proportional to it from a large alternating current, and the main part of the current transformer includes a primary coil having a small number of windings and a secondary coil having a large number of windings in a stratified core such as a transformer. Winding, the secondary coil is provided with an ammeter, a power meter, a relay, and the like.

The current ratios of the primary and secondary of the current transformer are similar to the half ratio of the number of coil windings, respectively. There are various ratings of the primary current from tens of A to thousands of A, but the rating of the secondary current is mostly 5A.

On the other hand, it is safe to short the secondary terminal of the current transformer, but it is very dangerous to open the secondary terminal of the current transformer. Because, when the secondary coil is opened while the current flows through the primary coil of the current transformer, the primary current magnetizes all the iron cores and can heat up as the iron core is saturated, thereby damaging or exploding the coil wound around the iron core. This is because there are risks.

Therefore, when the internal circuit of the instrument such as an ammeter or power meter connected to the secondary coil of the current transformer is opened or the secondary coil of the current transformer is opened due to other reasons, it is immediately detected and transmitted to the central control center or There is a need for a device capable of immediately shorting an open secondary terminal.

With this in mind, Patent Literature 1 transmits the fact of opening to the central control center when the secondary terminal of the current transformer is opened, and at the same time shortens the secondary terminal of the current transformer to shorten the current explosion accident or electric shock. A secondary open-monitoring switchgear configured to prevent this has been proposed.

However, in the case of patent document 1, the central control center is notified only when the secondary terminal of the current transformer is opened, so that the user side can take only a post-action and there is a problem that it cannot be proactively taken.

Korean Registered Patent No. 10-1772196 (August 22, 2017) (Secondary open monitoring switchgear) Korean Registered Utility Model No. 20-0352036 (2004.06.04) (Open circuit of secondary terminal of current transformer) Korean Patent Publication No. 10-2014-0009622 (2014.01.23) (current transformer protection device) Korean Registered Patent No. 10-1451387 (2014.10.08) (switch switch equipped with monitoring and protection device for secondary terminal opening of instrument) Korean Registered Patent No. 10-1273144 (2013.06.18) (Overcurrent relay and method for diagnosing the open state of the secondary circuit of the current transformer) Korean Patent Publication No. 10-2015-0073273 (2015.07.01) (Digital relay with open circuit secondary circuit monitoring function)

Accordingly, the technical problem of the present invention is to solve this problem, and the object of the present invention is to inform the user that the secondary terminal of the current transformer is in a dangerous state that can be opened in addition to the notification that the secondary terminal of the current transformer is opened. It is to provide a secondary-side open-monitoring switchgear configured to deal proactively.

In order to realize the object of the present invention described above, the current transformer secondary side open and close switchgear according to an embodiment is connected to the current transformer secondary side first terminal and the second terminal, respectively, to reduce the voltage of the secondary voltage of the current transformer; A comparator configured to output a first square wave signal when the reduced voltage output from the pressure reducer is within a threshold voltage range, and to output a second square wave signal when the reduced voltage is higher than the threshold voltage range; An analog-to-digital converter converting the first square wave signal into a first digital signal and converting the second square wave signal into a second digital signal; And (i) when the first digital signal is provided from the analog-to-digital converter, determines that the secondary terminal of the current transformer is in an open danger state and outputs a first control signal, and (ii) the analog-to-digital converter. When the second digital signal is provided from the control unit for determining that the secondary terminal of the current transformer is in an open state and includes a control unit for outputting a second control signal, the comparator includes a non-inverting comparator A first comparator that outputs the first square wave signal when the reduced voltage output from the pressure reducer is within a threshold voltage range; And a second comparator outputting the second square wave signal when the decompressor voltage output from the decompressor is higher than a threshold voltage range, wherein the non-inverting comparator inputs an input voltage through the secondary terminal of the decompressor. A third operational amplifier including a positive terminal to which it is applied; A fifth resistor connected to the power supply voltage through one end and connected to the negative terminal of the third operational amplifier through the other end; And a sixth resistor connected to the other end of the fifth resistor and the negative terminal of the third operational amplifier through one end, and connected to the second terminal of the secondary side of the pressure reducer through the other end, and the third operational amplifier. The voltage applied to the negative polarity terminal is set as a reference voltage, and the reference voltage is the same as an upper limit of the threshold voltage range.

In one embodiment, the first comparator includes a window comparator, and the window comparator includes a first operation including a negative terminal to which an input voltage is applied through a first terminal on the secondary side of the pressure reducer. amplifier; A second operational amplifier including a positive terminal to which the input voltage is applied; A first resistor connected to the power supply voltage through one end and connected to the positive terminal of the first operational amplifier through the other end; A second resistor connected to the other end of the first resistor through one end and connected to the negative terminal of the second operational amplifier through the other end; And a third resistor connected to the other end of the second resistor and the negative terminal of the second operational amplifier through one end, and connected to the second terminal of the secondary side of the pressure reducer through the other end, and the first operational amplifier. The input voltage applied to the positive polarity terminal is set to an upper limit of the threshold voltage range, and the input voltage applied to the negative polarity terminal of the second operational amplifier is set to a lower limit of the threshold voltage range, The sum of the resistance value and the resistance value of the third resistance is set to be the same as the resistance value of the sixth resistance, and the sum of the resistance value of the first resistance, the resistance value of the second resistance, and the resistance value of the third resistance is the fifth resistance It may be set to be the same as the resistance value of and the resistance value of the sixth resistance.

In one embodiment, the transformer secondary side open monitoring switchgear includes: a short circuit switch having both ends connected to the secondary side terminal of the current transformer; And a short circuit unit that closes the shorting switch when the second control signal is input to short the secondary terminal of the current transformer.

In one embodiment, the secondary side open monitoring switchgear of the current transformer, when the first control signal is provided, transmits a signal indicating that the secondary side of the current transformer is in an open danger state to a central control center through wired / wireless communication, and the second When a control signal is provided, the wire / wireless communication unit for transmitting a signal indicating that the secondary side of the current transformer is open to the central control center through wire / wireless communication may be further included.

In one embodiment, the secondary side open-monitoring switchgear of the current transformer, when the first control signal is provided, alerts that the secondary side of the current transformer is in an open danger state, and when the second control signal is provided, the secondary side of the current transformer It may further include an alarm unit for processing the alarm in the open state.

According to the secondary open / closed switchgear of the current transformer, the voltage of the secondary terminal of the current transformer is decompressed through a decompressor (or transformer), and when the depressurized voltage is equal to or higher than the upper limit (VH) of the threshold voltage range, the secondary terminal of the current transformer is opened. It is determined, and if the depressurized voltage exists between the lower limit VL and the upper limit VH of the threshold voltage range, it is determined as an open danger state in which the secondary terminal of the current transformer can be opened. Accordingly, it is possible to proactively cope with the risk of opening the secondary terminal of the current transformer by notifying the user that it is in a dangerous state that can be opened in addition to the notification that the secondary terminal of the current transformer is opened.

1 is a block diagram for schematically explaining the secondary side open monitoring switchgear according to an embodiment of the present invention.
FIG. 2 is a circuit diagram illustrating an example of the first comparator and the second comparator shown in FIG. 1.
3 is a waveform diagram for schematically explaining input / output waveforms in each of the first comparator and the second comparator of FIG. 2.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. The present invention can be applied to various changes and may have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosure form, and it should be understood that it includes all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing each drawing, similar reference numerals are used for similar components. In the accompanying drawings, the dimensions of the structures are shown to be enlarged than the actual for clarity of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this application, terms such as “include” or “have” are intended to indicate the presence of features, numbers, steps, actions, elements, parts or combinations thereof described in the specification, but one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, actions, components, parts or combinations thereof are not excluded in advance.

Also, unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

1 is a block diagram for schematically explaining the secondary side open monitoring switchgear according to an embodiment of the present invention.

Referring to Figure 1, the secondary switch open-side monitoring switchgear according to an embodiment of the present invention, the overvoltage protection unit 110, the pressure reducer 120, the comparison unit 130, the analog-to-digital conversion unit 140, the control unit 150, a short circuit unit 160, a wired / wireless communication unit 170, and an alarm unit 180.

The overvoltage protection unit 110 blocks the overvoltage output through the secondary terminal of the current transformer 10.

The pressure reducer 120 is connected to the first and second terminals of the secondary side of the current transformer 10, respectively, to reduce the voltage of the secondary terminal of the current transformer 10 and provide the attenuated voltage to the comparator 130. In this embodiment, the pressure reducer 120 is arranged to reduce the voltage of the secondary terminal voltage of the current transformer 10, but the voltage lower than the power supply voltage Vcc used in the comparison unit 130 is 2 of the current transformer 10. The pressure reducer 120 may be omitted if it is a terminal voltage on the vehicle side.

The comparator 130 includes a first comparator 132 and a second comparator 134 and converts the first square wave signal into analog-to-digital signals when the decompression voltage output from the decompressor 120 is within a threshold voltage range. Output to the unit 140, and when the reduced voltage is higher than the threshold voltage range, outputs a second square wave signal to the analog-to-digital converter 140. In this embodiment, the threshold voltage range is used as a criterion to inform the user of the risk of opening or opening the secondary terminal of the current transformer. That is, when the depressurization voltage exceeds the threshold voltage range, the user can inform the user that the secondary terminal of the current transformer is open, and when the depressurization voltage is in the threshold voltage range, the user can inform the user that the secondary terminal of the current transformer is in danger of opening. .

The analog-to-digital converter 140 includes a first A / D converter 142 and a second A / D converter 144, and converts the first square wave signal into a first digital signal to the controller 150. And converts the second square wave signal into a second digital signal and provides it to the controller 150.

When the first digital signal is provided from the analog-to-digital converter 140, the controller 150 determines that the secondary terminal of the current transformer 10 is in an open danger state and transmits the first control signal to the wire / wireless communication unit 170. And outputting to the alarm unit 180, and determining that the secondary terminal of the current transformer 10 is in an open state when the second digital signal is provided from the analog-to-digital converter 140, and shorting the second control signal to the short circuit unit 160. ), Wired / wireless communication unit 170 and the alarm unit 180.

When the second control signal is input from the control unit 150, the short circuit unit 160 closes the shorting switch 162 connected to the secondary terminal of the current transformer 10 at both ends to short the secondary terminal of the current transformer 10. .

When the first control signal is provided from the control unit 150, the wire / wireless communication unit 170 transmits a signal indicating that the secondary side of the current transformer 10 is in an open danger state to the central control center through the wire / wireless communication, and the control unit ( When the second control signal is provided from 150), a signal indicating that the secondary side of the current transformer 10 is open is transmitted to the central control center through wired / wireless communication.

The wired / wireless communication unit 170 may include a wired communication unit connected to a central control center through wired communication, and a wireless communication unit that transmits to the central control center through RF wireless communication.

The wireless communication unit includes an IF local oscillator, an IF band upconversion mixer, an IF amplifier, a channel selection filter, an RF upconversion mixer, an RF local oscillator, a phase locked loop (PLL), an image cancellation filter, a driving amplifier, and a primary band. It can be configured to include a pass filter, a power amplifier, an isolator, a second band pass filter, and an antenna.

Specifically, the IF local oscillator is a baseband frequency in the IF band up-converting mixer to convert the base band frequency containing the open data for the secondary terminal of the current transformer 10 to an intermediate frequency (IF). And the frequency to be mixed. The IF band up-conversion mixer synthesizes the base band frequency and the frequency supplied from the IF local oscillator to up-convert the base band frequency to an intermediate frequency. The IF amplifier amplifies the signal output from the IF band up-conversion mixer. The channel selection filter removes a signal of an unwanted channel frequency generated by an IF band up-conversion mixer among signals output from the IF amplifier and passes only a signal of a channel frequency to be transmitted to an RF receiver. The RF up-conversion mixer up-converts the intermediate frequency output from the channel selection filter and the frequency output from the RF local oscillator to the RF frequency. The RF local oscillator supplies a synthesized frequency to the RF upconversion mixer. The phase locked loop (PLL) holds the frequency outputted from the RF local oscillator so that it is output constantly without shaking. The image removal filter removes an image frequency included in a signal output from the RF up-conversion mixer. The driving amplifier amplifies the signal output from the image removal filter to a predetermined gain. The first band pass filter attenuates unnecessary frequency components output from the driving amplifier. The power amplifier amplifies and outputs a signal output from the primary band pass filter. The isolator sends a signal output from the power amplifier to a second band pass filter while preventing the signal from being received in reverse through the antenna. The second band pass filter cuts out nonlinear spurious frequency components output from the isolator and outputs only a desired frequency band. The antenna radiates an electrical signal output from the secondary band pass filter to electromagnetic waves in the air.

When the first control signal is provided from the control unit 150, the alarm unit 180 alarms that the secondary side of the current transformer 10 is in an open danger state, and when the second control signal is provided from the control unit 150, the current transformer 10 ) The secondary side of the alarm is alarmed.

As described above, the secondary terminal voltage of the current transformer is sensed in real time, and an open danger state is determined by notifying that the secondary terminal of the current transformer may exceed the set voltage level, and the fact that the open danger condition is an open danger state is sent to the central control center. Transmission so that preemptive action can be taken.

In addition, the secondary terminal voltage of the current transformer is sensed in real time, and when the secondary terminal of the current transformer exceeds the set voltage level, it is determined that the secondary terminal of the current transformer is open, and the secondary terminal of the current transformer is short-circuited at the same time. The fact that the terminal is open is sent to the central control center so that prompt action can be taken.

Accordingly, the secondary switch monitoring switchgear according to the present invention can prevent an explosion or electric shock accident of the current transformer due to the opening of the secondary terminal of the current transformer.

FIG. 2 is a circuit diagram illustrating an example of the first comparator 132 and the second comparator 134 shown in FIG. 1. 3 is a waveform diagram for schematically explaining input / output waveforms in each of the first comparator 132 and the second comparator 134 of FIG. 2.

1, 2, and 3, the first comparator 132 includes a window comparator, and the decompression voltage output from the decompressor 120, that is, the input voltage Vin is a threshold voltage range When present in the first square wave signal (Vout1) is output. The window comparator is composed of a first operational amplifier (OP11), a second operational amplifier (OP12), a first resistor (R11), a second resistor (R12), a third resistor (R13) and a fourth resistor (R14) You can.

Specifically, the first operational amplifier OP11 is connected to the contact of the negative terminal, the first resistor R11 and the second resistor R12, to which the input voltage is applied through the first terminal of the secondary side of the pressure reducer 120. It includes a positive polarity terminal and an output terminal that outputs the first square wave signal Vout1 to the first A / D converter 142.

The second operational amplifier OP12 includes a negative polarity terminal connected to the contact of the second resistor R12 and a third resistor R13, a positive polarity terminal to which an input voltage is applied, and a second square wave signal Vout2. / D includes an output terminal output to the conversion unit 144.

The first resistor R11 is connected to the power supply voltage Vcc through one end, and is connected to the positive terminal of the first operational amplifier OP11 and one end of the second resistor R12 through the other end.

The second resistor R12 is connected to the other end of the first resistor R11 through one end, and is connected to the negative terminal of the second operational amplifier OP12 and one end of the third resistor R13 through the other end.

The third resistor R13 is connected to the other terminal of the second resistor R12 and the negative terminal of the second operational amplifier OP12 through one end, and is connected to the second terminal of the secondary side of the pressure reducer 120 through the other terminal. do.

The fourth resistor R14 is connected to the power supply voltage Vcc through one end, and is connected to the output terminal of the first operational amplifier OP11 through the other end.

In the first comparator 132, the input voltage Vin applied to the positive terminal of the first operational amplifier OP11 is set to an upper limit VH of the threshold voltage range, and the negative polarity of the second operational amplifier OP12 The input voltage Vin applied to the terminal is set to the lower limit VL of the threshold voltage range. The input voltage Vin applied to the positive polarity terminal of the first operational amplifier OP11 and the input voltage Vin applied to the negative polarity terminal of the second operational amplifier OP12 are respectively the resistance value of the first resistor R11, It may be set by the resistance value of the second resistor R12 and the resistance value of the third resistor R13. For example, if the resistance values of the first resistor R11, the second resistor R12, and the third resistor R13 are the same, the upper limit VH of the threshold voltage range corresponds to (2/3) Vcc, The lower limit VL of the threshold voltage range may correspond to (1/3) Vcc. In this way, the upper limit value VH and the lower limit value VL of the threshold voltage range may be set by adjusting the resistance values of the first resistor R11, the second resistor R12, and the third resistor R13.

Specifically, each of the upper limit (VH) and the lower limit (VL) of the threshold voltage range may be defined by Equation 1 and Equation 2 below.

[Equation 1]

[Equation 2]

와 같이 계산될 수 있고, 임계 전압 범위의 하한치(VL)는

와 같이 계산될 수 있다. 즉, 감압기(120)의 2차측 제2 단자를 통해 입력되는 입력전압(Vin)이 전원전압(Vcc)의 80% 내지 90%의 범위에 존재하는 경우, 제1 비교기(132)는 제1 구형파 신호(Vout1)를 출력한다. For example, if the resistance values of each of the first resistor R11, the second resistor R12, and the third resistor R13 are 10 µs, 10 µs, and 80 µs, the upper limit of the threshold voltage range (VH) is

It can be calculated as, the lower limit of the threshold voltage range (VL)

Can be calculated as That is, when the input voltage Vin input through the second terminal of the secondary side of the pressure reducer 120 is present in the range of 80% to 90% of the power supply voltage Vcc, the first comparator 132 is the first The square wave signal Vout1 is output.

Meanwhile, the second comparator 134 includes a non-inverting comparator, and outputs a second square wave signal Vout2 when the decompression voltage output from the decompressor 120 is higher than a threshold voltage range. The non-inverting comparator may include a third operational amplifier OP21, a fifth resistor R21, and a sixth resistor R22.

Specifically, the third operational amplifier OP21 is connected to the contact of the positive terminal, the fifth resistor R21 and the sixth resistor R22, through which the input voltage is applied through the first terminal of the secondary side of the pressure reducer 120. It includes a negative polarity terminal and an output terminal outputting the second square wave signal Vout2 to the second A / D conversion unit 144.

The fifth resistor R21 is connected to the power supply voltage Vcc through one end, and is connected to the negative terminal of the third operational amplifier OP21 and one end of the sixth resistor R22 through the other end.

The sixth resistor R22 is connected to the other end of the fifth resistor R21 and the negative terminal of the third operational amplifier OP21 through one end, and is connected to the second terminal of the secondary side of the pressure reducer 120 through the other end. do.

In the second comparator 134, the voltage applied to the negative terminal of the third operational amplifier OP21 is set to the reference voltage VREF. Here, the reference voltage VREF corresponds to the upper limit VH of the threshold voltage range.

The voltage applied to the negative polarity terminal of the third operational amplifier OP21 may be set by the resistance value of the fifth resistor R21 and the resistance value of the sixth resistor R22. For example, if the resistance values of each of the fifth resistor R21 and the sixth resistor R22 are the same, the reference voltage may correspond to (1/2) Vcc. In this way, the reference voltage VREF, that is, the upper limit VH of the threshold voltage range may be set by adjusting the resistance values of the fifth resistor R21 and the sixth resistor R22.

Specifically, the reference voltage VREF, that is, the upper limit VH of the threshold voltage range may be defined by Equation 3 below.

[Equation 3]

와 같이 계산될 수 있다. 즉, 감압기(120)의 2차측 제2 단자를 통해 입력되는 입력전압(Vin)이 전원전압(Vcc)의 90%의 범위에 존재하는 경우, 제2 비교기(134)는 제2 구형파 신호(Vout2)를 출력한다. For example, if the resistance values of the fifth resistor R21 and the sixth resistor R22 are 10 ㏀ and 90 각각, respectively, the reference voltage V _REF is

Can be calculated as That is, when the input voltage Vin input through the second terminal of the secondary side of the pressure reducer 120 is present in the range of 90% of the power supply voltage Vcc, the second comparator 134 displays the second square wave signal ( Vout2).

Therefore, in order to be set equal to the reference voltage VREF and the upper limit VH of the threshold voltage range, the sum of the resistance value of the second resistor R12 and the resistance value of the third resistor R13 is the resistance value of the sixth resistor R22. Is set to be equal to (that is, R12 + R13 = R22), the sum of the resistance value of the first resistor R11, the resistance value of the second resistor R12 and the resistance value of the third resistor R13 is the fifth resistor R21 It is preferable to set the same as the resistance value of and the resistance value of the sixth resistor R22 (that is, R11 + R12 + R13 = R21 + R22).

As described above, according to the present invention, the voltage of the secondary terminal of the current transformer is reduced through a pressure reducer (or transformer), and when the reduced voltage is equal to or higher than the upper limit of the threshold voltage range (VH), the secondary terminal of the current transformer is open If it is determined that the depressurized voltage exists between the lower limit (VL) and the upper limit (VH) of the threshold voltage range, it is determined as an open danger state in which the current transformer secondary terminal can be opened. Accordingly, it is possible to proactively cope with the risk of opening the secondary terminal of the current transformer by notifying the user that it is in a dangerous state that can be opened in addition to the notification that the secondary terminal of the current transformer is opened.

Although described above with reference to examples, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand.

110: overvoltage protection unit 120: pressure reducer
130: comparator 132: first comparator
134: second comparator 140: analog-to-digital converter
142: first A / D converter 144: second A / D converter
150: control unit 160: short circuit
170: wired / wireless communication unit 180: alarm unit
162: short circuit switch

Claims (5)

A pressure reducer which is connected to the current transformer secondary side first terminal and the second terminal, respectively, to decompress the voltage of the secondary terminal of the current transformer;
A comparator configured to output a first square wave signal when the reduced voltage output from the pressure reducer is within a threshold voltage range, and to output a second square wave signal when the reduced voltage is higher than the threshold voltage range;
An analog-to-digital converter converting the first square wave signal into a first digital signal and converting the second square wave signal into a second digital signal; And
(i) when the first digital signal is provided from the analog-to-digital converter, determines that the secondary terminal of the current transformer is in an open danger state and outputs a first control signal, and (ii) from the analog-to-digital converter When the second digital signal is provided, a control unit for determining that the secondary terminal of the current transformer is in an open state and outputting a second control signal, wherein the comparator includes:
A first comparator for outputting the first square wave signal when a decompression voltage output from the decompressor is within a threshold voltage range, including a non-inverting comparator; And
And a second comparator outputting the second square wave signal when the decompression voltage output from the decompressor is higher than a threshold voltage range, wherein the non-inverting comparator comprises:
A third operational amplifier including a positive terminal to which an input voltage is applied through a first terminal on the secondary side of the pressure reducer;
A fifth resistor connected to the power supply voltage through one end and connected to the negative terminal of the third operational amplifier through the other end; And
A sixth resistor connected to the other terminal of the fifth resistor and the negative terminal of the third operational amplifier through one end, and connected to the second terminal of the secondary side of the pressure reducer through the other end,
The voltage applied to the negative terminal of the third operational amplifier is set as a reference voltage, and the reference voltage is the same as the upper limit of the threshold voltage range. The method of claim 1, wherein the first comparator comprises a window comparator (Window comparator), the window comparator,
A first operational amplifier including a negative terminal to which an input voltage is applied through a second terminal on the secondary side of the pressure reducer;
A second operational amplifier including a positive terminal to which the input voltage is applied;
A first resistor connected to the power supply voltage through one end and connected to the positive terminal of the first operational amplifier through the other end;
A second resistor connected to the other end of the first resistor through one end and connected to the negative terminal of the second operational amplifier through the other end; And
A third resistor connected to the other terminal of the second resistor and the negative terminal of the second operational amplifier through one end, and connected to the second terminal of the secondary side of the pressure reducer through the other end,
The input voltage applied to the positive polarity terminal of the first operational amplifier is set to an upper limit of the threshold voltage range, and the input voltage applied to the negative polarity terminal of the second operational amplifier is set to a lower limit of the threshold voltage range,
The sum of the resistance of the second resistor and the resistance of the third resistor is set equal to the resistance of the sixth resistor, and the sum of the resistance of the first resistor, the resistance of the second resistor, and the resistance of the third resistor Is a second resistance open and closed switchgear of the current transformer, characterized in that set to be the same as the resistance value of the fifth resistor and the resistance value of the sixth resistor. According to claim 1,
A short circuit switch having both ends connected to a secondary terminal of the current transformer; And
When the second control signal is input further comprises a short circuit section for closing the short-circuit switch to short-circuit the secondary terminal of the current transformer, the current transformer secondary-side open monitoring switchgear. According to claim 1,
When the first control signal is provided, a signal indicating that the secondary side of the current transformer is in an open danger state is transmitted to a central control center through wired / wireless communication, and when the second control signal is provided, indicating that the secondary side of the current transformer is open Further comprising a wired / wireless communication unit for transmitting a signal to the central control center through the wired / wireless communication. According to claim 1, When the first control signal is provided, an alarm unit is configured to alert that the secondary side of the current transformer is in an open danger state, and when the second control signal is provided, an alarm unit to process the secondary side of the current transformer to be alarmed Further comprising the current transformer secondary side open monitoring switchgear, characterized in that it further comprises.

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