JP2016205867A - Electric leakage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric leakage detector that can obtain demagnetization effects while suppressing increase in error of electric leakage detection.SOLUTION: An electric leakage detector 10 includes: a relay 11; a magnetic core 12; an exciting coil 13; a detection circuit 15; and a controller 16. When the controller 16 detects an electric leakage, the controller controls the relay 11 so that the relay will be in a non-connection state, and controls an excitation circuit 14 so that an excitation voltage of a second frequency lower than a first frequency will be excited to the exciting coil 13 in a non-connection state for a predetermined period of time.SELECTED DRAWING: Figure 1

Description

  The present invention generally relates to a leakage detection device, and more particularly to a leakage detection device that detects a measured current generated in a measured wire.

  2. Description of the Related Art In recent years, a flux gate type leakage detection device (hereinafter referred to as a leakage detection device) that detects a measured current generated in a measured wire made up of a pair of wires and detects a leakage based on the detected measured current. ) Is used.

  A conventional earth leakage detection device is made of a highly magnetic permeable material and includes a magnetic core having an opening through which a measured electric wire passes. An exciting coil is wound around the magnetic core. The leakage detecting device applies an excitation voltage of an AC rectangular wave having a predetermined period to the excitation coil, and generates an excitation current. The leakage detection device converts the excitation current flowing through the excitation coil into a detection voltage using a resistor, and outputs a PWM signal based on the magnitude relationship between the detection voltage and the threshold value. The leakage detection device outputs an integral value of the PWM signal as an output voltage. The leakage detecting device detects a leakage by detecting a measured current generated in the measured wire based on the output voltage.

  Normally, in the leakage detection device, magnetism remains in the exciting core (magnetization). If this magnetism remains, an error will occur in the leakage detection, and it is necessary to remove this magnetism (demagnetization). Therefore, in Patent Document 1, demagnetization is performed by changing the amplitude of the excitation voltage, that is, the amplitude of a predetermined frequency.

Japanese Patent No. 4118259

  In the technique described in Patent Document 1, in order to obtain a demagnetizing effect, the amplitude of the excitation voltage used at the time of leakage detection is once increased. However, when the amplitude is increased, the excitation voltage (signal) becomes noise, and the target voltage is increased. There is a possibility that the detection error of the measurement current becomes large.

  Therefore, the present invention has been made in view of the above reasons, and an object of the present invention is to provide a leakage detecting device capable of suppressing an increase in leakage detection error and obtaining a demagnetizing effect.

  A leakage detection device according to one aspect of the present invention is a leakage detection device that detects a leakage of a measured wire between a power source and a load, and is interposed in the measured wire, and the power supply and the A magnetic core having a relay that switches between a connection state in which a load is electrically connected and a non-connection state in which the load is not electrically connected, and an opening through which the wire to be measured is inserted An excitation coil wound around the magnetic core, an excitation circuit for applying an excitation voltage of a first frequency to the excitation coil in the connected state to generate an excitation current flowing in the excitation coil, and the excitation A detection circuit that detects a current obtained by averaging the current, and a control unit, and the control unit detects the leakage based on the value of the current detected by the detection circuit in the connected state; So that the Lille And controlling the excitation circuit so that an excitation voltage having a second frequency that is lower than the first frequency is applied to the excitation coil for a predetermined time in the disconnected state. .

  According to the above-described leakage detection device, it is possible to suppress an increase in an error in leakage detection and to obtain a demagnetizing effect.

It is a figure explaining the structure of the earth-leakage detection apparatus of Embodiment 1. FIG. It is a figure explaining the use application of the earth-leakage detection apparatus of Embodiment 1. 3 is a flowchart for explaining the operation of the electric leakage detection apparatus according to the first embodiment. 4A is a BH curve showing the characteristics of the magnetic flux density B and the magnetic field H when the first frequency is used, and FIG. 4B is a BH curve when the second frequency is used. . It is a figure explaining the structure of the leak detection apparatus of Embodiment 2. FIG. 6A shows the change in the detection voltage, FIG. 6B shows the change in the excitation voltage output from the first drive circuit 100, and FIG. 6C shows the change in the excitation voltage output from the second drive circuit 101. It is.

(Embodiment 1)
Hereinafter, the fluxgate type leakage detection device (hereinafter referred to as a leakage detection device) 10 of the present embodiment will be described. FIG. 1 is a diagram for explaining a configuration of a leakage detection device 10 of the present embodiment, and FIG. 2 is a diagram for explaining a use application of the leakage detection device 10.

  The leakage detection device 10 is a device that detects a leakage of the measured wire 22 by detecting a measured current (unbalanced current) generated in the measured wire 22 including a pair of wires. Here, the current to be measured is a difference current between a current flowing through one electric wire and a current flowing through the other electric wire. As shown in FIG. 2, the leakage detection device 10 is used in a charging system that charges a storage battery of an electric vehicle (load) 21. Examples of the electric vehicle 21 include an electric vehicle and a plug-in hybrid vehicle. Specifically, in the charging system, a power source (commercial system) 20 that supplies commercial power and an electric vehicle 21 are connected via a converter 30. The earth leakage detection device 10 is interposed between the power source 20 and the conversion device 30 and detects an earth leakage with respect to the measured electric wire 22 that connects the power source 20 and the conversion device 30. The conversion device 30 has a function of converting AC power into DC power and converting DC power into AC power. Here, the current to be measured 22 flows from the power source 20 to the electric vehicle 21 in the direction of the first electric wire to be measured 22a (see FIG. 1) and from the electric vehicle 21 to the power source 20 in the direction of current. It has the 2nd to-be-measured electric wire 22b (refer FIG. 1). When there is no leakage in the measured wire 22, the amount of current flowing through the first measured wire 22a and the amount of current flowing through the second measured wire 22b are the same, so the value of the measured current Becomes 0. However, when a leakage occurs, the amount of current flowing through the first measured wire 22a is different from the amount of current flowing through the second measured wire 22b. Value. The leakage detection device 10 can detect the presence or absence of a leakage of the measured wire 22 according to the value of the measured current.

  Thereby, the leakage detection device 10 can directly detect a leakage of an alternating current flowing between the power supply 20 and the conversion device 30. In addition, the leakage detection device 10 can indirectly detect a leakage of a high-frequency current flowing through the conversion device 30 and a direct current flowing between the conversion device 30 and the electric vehicle 21.

  The leakage detection device 10 of the present embodiment further has a function of demagnetizing the magnetism remaining in the magnetic core 12 described later during the leakage detection process. By performing demagnetization, the leakage detection device 10 can improve the accuracy of leakage detection and obtain a demagnetization effect.

  First, the configuration of the leakage detection device 10 of the present embodiment will be described. As shown in FIG. 1, the leakage detection device 10 includes a relay 11, a magnetic core 12, an excitation coil 13, an excitation circuit 14, a detection circuit 15, and a control unit 16. In FIG. 1, the conversion device 30 is omitted.

  The relay 11 is a switch that switches between a connected state in which the power source 20 and the electric vehicle 21 are electrically connected and a non-connected state in which the power source 20 and the electric vehicle 21 are not electrically connected under the control of the control unit 16 described later. It is. Hereinafter, when the relay 11 is in an ON state, that is, when the switch is closed, the connection state is established, and when the relay 11 is in an OFF state, that is, when the switch is in an open state, the connection state is established.

  The magnetic core 12 is an annular magnetic core having an opening through which the measured electric wire 22 is inserted, and the exciting coil 13 is a coil wound around the magnetic core 12.

  The excitation circuit 14 is a circuit that applies an excitation voltage to the excitation coil 13. Specifically, the excitation circuit 14 generates an excitation clock that oscillates at a predetermined frequency. The excitation circuit 14 amplifies the generated excitation clock, generates a square wave signal (excitation voltage) having a predetermined voltage amplitude, and outputs the square wave signal to the excitation coil 13. As a result, the excitation voltage is applied to the excitation coil 13. In the present embodiment, the excitation circuit 14 generates a first excitation clock that oscillates at the first frequency while the leakage detection process is being performed. A second excitation clock oscillated at a second frequency lower than the first frequency is generated. Note that the amplitude of the first frequency is the same as the amplitude of the second frequency.

  The detection circuit 15 is a circuit that detects a current obtained by averaging the excitation current output from the excitation coil 13. Specifically, the excitation current output from the excitation coil 13 is converted into a detection voltage. The detection circuit 15 averages the detection voltage. The average value of the detection voltage changes linearly with respect to the magnitude of the leakage current. Thereby, the detection circuit 15 can detect the current obtained by averaging the excitation current.

  The control unit 16 includes a device including a processor that operates according to a program as a main hardware element. A device provided with a processor may be a micro controller in addition to a microprocessor. The program to be executed by the processor is written in advance in a ROM (Read Only Memory), and is provided through an electric communication line such as the Internet, or is provided by a computer-readable recording medium.

  The control unit 16 controls the opening and closing of the relay 11 and detects the presence or absence of electric leakage. When the power supply 20 and the electric vehicle 21 are in an electrically connected state, the control unit 16 detects the presence / absence of electric leakage based on the signal averaged by the detection circuit 15. The control unit 16 stores in advance a value (reference value) proportional to the average value of the excitation current in a state where no leakage occurs, that is, an unbalanced current is not flowing through the measured wire 22. If a leakage occurs, that is, if an unbalanced current flows through the wire 22 to be measured, the electric field of the magnetic core 12 changes, and the detected voltage to be detected also changes. The control unit 16 detects a leakage based on the difference (change amount) between the average value output from the detection circuit 15 and the reference value.

  When detecting a leakage, the control unit 16 controls the relay 11 so that the power source 20 and the electric vehicle 21 are electrically disconnected from each other. The controller 16 controls the excitation circuit 14 so that the frequency used for generating the excitation clock is switched from the first frequency to the second frequency while the relay 11 is turned off when restarting at the next use. The control unit 16 controls the excitation circuit 14 so that the frequency used for generating the excitation clock is switched from the second frequency to the first frequency when the predetermined time has elapsed, and the power source 20 and the electric vehicle 21 are electrically connected to each other. The relay 11 is controlled so as to be connected. Here, the predetermined time is, for example, 1 minute. In addition, this numerical value is an example, Comprising: It is not the meaning limited to this numerical value.

  Next, the operation of the leakage detection device 10 will be described using the flowchart shown in FIG.

  The controller 16 controls the excitation circuit 14 to set the frequency used for the excitation clock to the first frequency before the start of the leakage detection operation (step S5).

  The controller 16 performs a leakage detection process (step S10), and determines whether or not a leakage has been detected (step S15). Specifically, the excitation circuit 14 applies the excitation voltage of the first frequency to the excitation coil 13 in a state where the power source 20 and the electric vehicle 21 are connected. The detection circuit 15 detects a current obtained by averaging the excitation current output from the excitation coil 13. Based on the value of the current detected by the detection circuit 15, the control unit 16 determines whether or not a current to be measured is detected, that is, whether or not a leakage has occurred.

  When the leakage is not detected (“No” in step S15), the control unit 16 continues the leakage detection process.

  When the electric leakage is detected (“Yes” in step S15), the control unit 16 turns off the relay 11 (step S20). That is, the control unit 16 turns off the relay 11 to bring the power source 20 and the electric vehicle 21 into a disconnected state.

  After the user has dealt with the electric leakage, when a restart instruction is input by a user operation, the control unit 16 restarts (step S25). The control unit 16 controls the excitation circuit 14 so that the frequency used for generating the excitation clock is switched from the first frequency to the second frequency while the relay 11 is kept OFF (step S30). Thereby, the excitation circuit 14 applies the excitation voltage of the second frequency to the excitation coil 13.

  The control unit 16 determines whether or not a predetermined time has elapsed since the frequency switching (step S35).

  When determining that it has not elapsed (“No” in step S35), the control unit 16 waits for a predetermined time. While waiting for the elapse of a predetermined time, the excitation circuit 14 is demagnetizing by applying an excitation voltage of the second frequency to the excitation coil 13.

  When determining that the time has elapsed (“Yes” in step S35), the control unit 16 controls the excitation circuit 14 to switch the frequency used for generating the excitation clock from the second frequency to the first frequency (step S40). . Furthermore, the control part 16 turns ON the relay 11 (step S45). That is, the control part 16 makes the connection state between the power supply 20 and the electric vehicle 21 by turning on the relay 11. And the control part 16 returns to step S10, and performs the detection process of an electrical leakage.

  Next, the demagnetizing effect by the leakage detection device 10 of the present embodiment will be described with reference to FIGS. 4A and 4B. FIG. 4A is a magnetic hysteresis curve (BH curve) showing the characteristics of the magnetic flux density B and the magnetic field H when the first frequency is used, and FIG. 4B shows B when the second frequency is used. -H curve.

  Usually, in order to obtain a demagnetizing effect, it is necessary to saturate the magnetic flux density. For example, in FIG. 4A, the magnetic flux density B is saturated at b1, and this saturated state is reached when the magnetic field H becomes h1. 4A represents the amplitude of the excitation voltage, that is, the frequency amplitude. Generally, the amplitude is increased to bring the magnetic flux density to a completely saturated state, and then the amplitude is decreased to obtain a demagnetizing effect.

  Incidentally, the BH characteristic depends on the frequency of the excitation voltage, and the higher the frequency, the larger the width of the magnetic field H (the width of -h1 to h1 in FIG. 4A). Therefore, as shown in FIG. 4B, by using the second frequency lower than the first frequency, the width of the magnetic field H (the width from −h3 to h3 in FIG. 4B) is used. It can be made smaller than the case. Therefore, even if the amplitude is the same, the magnetic flux density can be sufficiently saturated by changing the frequency. That is, the same demagnetization effect as when the frequency amplitude is increased can be obtained.

  In the present embodiment, the leakage detecting device 10 switches the frequency from the first frequency to the second frequency to obtain the demagnetizing effect, but is not limited thereto. The leakage detection device 10 may change the amplitude of the second frequency while switching the frequency. Specifically, in order to sufficiently saturate the magnetic flux density, the control unit 16 controls the excitation circuit 14 so that the amplitude of the second frequency is once increased, and then, as time elapses within a predetermined time, The excitation circuit 14 is controlled so that the amplitude becomes small. Thereby, since the leak detection apparatus 10 can make a magnetic flux density into a more sufficient saturation state, the further demagnetizing effect can be anticipated.

  As described above, the leakage detection device 10 of the present embodiment detects a leakage of the measured wire 22 between the power source 20 and the electric vehicle 21 (load). The leakage detection device 10 includes a relay 11, a magnetic core 12, an excitation coil 13, an excitation circuit 14, a detection circuit 15, and a control unit 16. The relay 11 is interposed in the electric wire 22 to be measured and is in a connected state in which the power source 20 and the electric vehicle 21 are electrically connected by opening and closing the switch, and in a disconnected state in which the power source 20 and the electric vehicle 21 are not electrically connected. And switch. The magnetic core 12 has an opening through which the wire to be measured 22 is inserted. The exciting coil 13 is wound around the magnetic core. The excitation circuit 14 generates an excitation current that flows through the excitation coil 13 by applying an excitation voltage of the first frequency to the excitation coil 13 in the connected state. The detection circuit 15 detects a current obtained by averaging the excitation current. When the leakage current is detected based on the value of the current detected by the detection circuit 15 in the connected state, the control unit 16 controls the relay 11 to be in the disconnected state. The control unit 16 controls the excitation circuit 14 so that an excitation voltage having a second frequency that is lower than the first frequency is applied to the excitation coil 13 for a predetermined time in a disconnected state.

  According to this configuration, since the leakage detection device 10 switches the frequency in order to obtain a demagnetizing effect, the amplitude of the excitation voltage does not change. Therefore, the leakage detection device 10 can obtain a demagnetization effect while suppressing an increase in leakage detection error.

  Here, it is preferable that the control unit 16 further controls the excitation circuit 14 so that the amplitude of the excitation voltage of the second frequency decreases as time elapses within a predetermined time.

  According to this configuration, the leakage detection device 10 can be expected to have a further demagnetizing effect.

(Embodiment 2)
The earth leakage detection device 10 in the present embodiment will be described focusing on differences from the first embodiment. In the present embodiment, the configurations of the excitation circuit 14 and the detection circuit 15 are embodied. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  The detection circuit 15 of this embodiment includes a resistor Rs and an averaging circuit 110 as shown in FIG. The resistor Rs is connected in series with the exciting coil 13 and converts the exciting current output from the exciting coil 13 into a detection voltage. The averaging circuit 110 averages the detection voltage converted by the resistor Rs. The control unit 16 detects the measured current generated in the measured wire 22 based on the average value (the average value of the excitation current) obtained by the averaging circuit 110.

  As shown in FIG. 5, the excitation circuit 14 of the present embodiment includes a first drive circuit 100, a second drive circuit 101, and a switch 102. The first drive circuit 100 is a circuit that outputs an excitation voltage of the first frequency by self-oscillating depending on the time constant of the series circuit of the excitation coil 13 and the resistor Rs. Specifically, when the absolute value of the detection voltage exceeds a predetermined value, self-oscillation occurs by inverting the polarity of the excitation voltage output. The second drive circuit 101 is a circuit that outputs an excitation voltage having a second frequency. The switch 102 switches between the first drive circuit 100 and the second drive circuit 101 as a connection destination of the exciting coil 13 under the control of the control unit 16.

  The control unit 16 controls the switch 102 so that the first drive circuit 100 and the exciting coil 13 are electrically connected when performing a leakage detection operation. Thereby, the first drive circuit 100 can apply the excitation voltage of the first frequency to the excitation coil 13. When the controller 16 detects that a leakage has occurred, the controller 16 controls the switch 102 so that the second drive circuit 101 and the exciting coil 13 are electrically connected. The controller 16 controls the switch 102 so that the connection destination of the exciting coil 13 becomes the second drive circuit 101 when restarting at the next use. Then, the control unit 16 controls the switch 102 so that the first drive circuit 100 and the exciting coil 13 are electrically connected when a predetermined time has elapsed. As long as the second drive circuit 101 and the exciting coil 13 are electrically connected, the relay 11 is OFF, that is, the power source 20 and the electric vehicle 21 are not connected, as in the first embodiment. It has become.

  Since the operation of the leakage detection device 10 of the present embodiment can be realized by the flowchart shown in FIG. 3, the description thereof is omitted here.

  Next, the detection voltage, the excitation voltage output from the first drive circuit 100, and the excitation voltage output from the second drive circuit 101 will be described. 6A shows the change in the detection voltage, FIG. 6B shows the change in the excitation voltage output from the first drive circuit 100, and FIG. 6C shows the change in the excitation voltage output from the second drive circuit 101, respectively. Yes.

  When the value of the detected voltage becomes equal to or greater than the predetermined value “a” at time t1, the first drive circuit 100 reverses the polarity, and the voltage value is “−” from the output of the excitation voltage having the voltage value “Va”. It changes to the output of the excitation voltage which is Va ″ (see FIGS. 6A and 6B). Thereby, the first drive circuit 100 can apply the excitation voltage of the first frequency (1 / (2 × t1)) to the excitation coil 13.

  In addition, the excitation voltage output from the second drive circuit 101 is the second frequency lower than the first frequency as described above. For example, as shown in FIG. 6C, the second frequency is “1 / (4 × t1)”.

  In the present embodiment, the first drive circuit 100 is a self-excited oscillation circuit, but the present invention is not limited to this. The first drive circuit 100 may be a circuit that outputs an excitation voltage having the first frequency.

  As described above, the excitation circuit 14 of the leakage detection device 10 of the present embodiment includes the first drive circuit 100 that applies the excitation voltage of the first frequency to the excitation coil 13 and the excitation voltage of the second frequency. And a second drive circuit 101 that applies to the exciting coil. The control unit 16 operates the first drive circuit 100 in the connected state, and switches the operation target from the first drive circuit 100 to the second drive circuit 101 when a leakage is detected. It is preferable to operate the second driving circuit 101 for a time.

  According to this configuration, the leakage detection device 10 can obtain a demagnetizing effect only by switching the connection destination with the exciting coil 13.

  Here, the detection circuit 15 is connected in series with the excitation coil 13 and includes a resistor Rs that converts the excitation current into a detection voltage. The first drive circuit 100 preferably applies the excitation voltage of the first frequency to the excitation coil 13 by self-excited oscillation that reverses the polarity of the output of the excitation voltage when the absolute value of the detection voltage exceeds a predetermined value. .

  According to this configuration, the leakage detection device 10 can obtain a demagnetizing effect by switching the frequency of the excitation voltage even when the self-excited oscillation method is used.

(Modification)
As mentioned above, although this invention was demonstrated based on Embodiment 1 and Embodiment 2, this invention is not restricted to embodiment mentioned above. For example, the following modifications can be considered.

  (1) In each of the embodiments described above, the magnetic core 12 has an annular shape, but is not limited thereto. The shape of the magnetic core 12 may be any shape that forms a closed magnetic path.

  (2) In each of the embodiments described above, when the control unit 16 detects a leakage, it is preferable to notify that a leakage has occurred in the measured wire 22.

  Thereby, the user can know that the electric leakage has occurred in the measured electric wire 22, and can promptly perform subsequent measures such as replacement of the measured electric wire 22.

  (3) You may combine the said embodiment and modification.

DESCRIPTION OF SYMBOLS 10 Leakage detection apparatus 11 Relay 12 Magnetic body core 13 Excitation coil 14 Excitation circuit 15 Detection circuit 16 Control part 22 Wire to be measured 100 1st drive circuit 101 2nd drive circuit Rs Resistance

Claims (4)

A leakage detection device for detecting a leakage of a measured wire between a power source and a load,
A relay interposed between the measured wires and switching between a connected state in which the power source and the load are electrically connected by opening and closing a switch and a non-connected state in which the power source is not electrically connected; ,
A magnetic core having an opening through which the wire to be measured is inserted;
An exciting coil wound around the magnetic core;
An excitation circuit for generating an excitation current flowing in the excitation coil by applying an excitation voltage of a first frequency to the excitation coil in the connected state;
A detection circuit for detecting a current obtained by averaging the excitation current;
A control unit,
The control unit, when detecting a leakage based on the value of the current detected by the detection circuit in the connected state, controls the relay so as to be in the disconnected state, and for a predetermined time in the disconnected state, The leakage detection device, wherein the excitation circuit is controlled so that an excitation voltage having a second frequency lower than the first frequency is applied to the excitation coil. The excitation circuit is
A first drive circuit that applies the excitation voltage of the first frequency to the excitation coil; and a second drive circuit that applies the excitation voltage of the second frequency to the excitation coil;
The controller is
When in the connected state, the first drive circuit is operated, and when the leakage is detected, the operation target is switched from the first drive circuit to the second drive circuit, and in the disconnected state for the predetermined time. The leakage detection device according to claim 1, wherein the second drive circuit is operated. The detection circuit includes a resistor connected in series with the excitation coil and converting the excitation current into a detection voltage.
The first drive circuit applies the excitation voltage of the first frequency to the excitation coil by self-excited oscillation that reverses the polarity of the output of the excitation voltage when the absolute value of the detection voltage exceeds a predetermined value. The leakage detecting device according to claim 2, wherein: The control unit further includes:
The leakage detection according to any one of claims 1 to 3, wherein the excitation circuit is controlled so that an amplitude of the excitation voltage of the second frequency decreases as time elapses within the predetermined time. apparatus.

Images