Measuring apparatus and measuring method

Abstract

To accurately measure a phase angle when measuring resistance component leakage current.SOLUTION: A measurement device 10 comprises: a magnetic core 11; a first coil L1 and a second coil L2 which are wound around the magnetic core 11; a current measurement circuit 12; a voltage measuring circuit 13; a phase angle detection circuit 15; a signal generator 14 capable of outputting sine wave to the second coil L2 and to the phase angle detection circuit 15; and a control portion 16. The phase angle detection circuit 15 can detect a phase angle for calibration between current measured by the current measurement circuit 12 while the signal generator 14 outputs the sine wave and sine wave input by the signal generator 14. The control portion 16 calculates a corrected phase angle on the basis of the phase angle and the phase angle for calibration, and calculates the resistance component leakage current on the basis of the leakage current and the corrected phase angle.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a measuring device and a measuring method.

Background Art

[0002] Conventionally, a technique for measuring the leakage current of a live wire has been known. A live wire is a wiring through which current is flowing. The leakage current is also referred to as "Io".

[0003] The leakage current has a resistive component leakage current and a capacitive component leakage current. The resistive component leakage current is also referred to as "Ior". The capacitive component leakage current is also referred to as "Ioc".

[0004] The leakage current (Io) is the vector sum of the resistive component leakage current (Ior) and the capacitive component leakage current (Ioc). Assuming that the phase angle between the leakage current of the wiring and the voltage of the wiring is θ, the resistive component leakage current (Ior) is expressed by the following formula. Ior = Io × cosθ

[0005] Since heat is generated when the resistive component leakage current flows, the resistive component leakage current can cause a fire or the like. Therefore, it is important to accurately measure the resistive component leakage current.

[0006] For example, Patent Document 1 discloses a detection device capable of measuring the resistive component leakage current.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Since the resistance component leakage current is calculated based on the leakage current and the phase angle as described in the above formula, in order to accurately measure the resistance component leakage current, it is necessary not only to accurately measure the leakage current but also to accurately measure the phase angle.

[0009] In the measurement of normal leakage current, an advance or delay of the phase occurs in a magnetic core and a current measurement circuit for measuring the leakage current. Therefore, it is necessary to adjust or correct the advance or delay of the phase during manufacturing or maintenance.

[0010] However, the advance or delay of the phase may vary greatly due to device degradation and changes in environmental temperature. Therefore, when actually measuring the resistance component leakage current, there may be a case where the advance or delay of the phase has changed greatly since the adjustment or correction, and it has been difficult to accurately measure the phase angle.

[0011] Therefore, an object of the present disclosure is to provide a measuring device and a measuring method capable of accurately measuring a phase angle when measuring a resistance component leakage current.

Means for Solving the Problems

[0012] A measuring device according to some embodiments is a measuring device capable of measuring a leakage current of a resistance component, and includes a magnetic core that can be arranged so as to surround the periphery of a wiring, a first coil and a second coil wound around the magnetic core, a current measurement circuit connected to the first coil and capable of measuring the leakage current of the wiring, a voltage measurement circuit capable of measuring the voltage of the wiring, a phase angle detection circuit capable of detecting a phase angle between the leakage current and the voltage, a signal generator capable of outputting a sine wave to the second coil and the phase angle detection circuit, and a control unit. The phase angle detection circuit can detect a calibration phase angle between the current measured by the current measurement circuit when the signal generator outputs the sine wave and the sine wave input from the signal generator. The control unit calculates a corrected phase angle based on the phase angle and the calibration phase angle, and calculates a leakage current of a resistance component based on the leakage current and the corrected phase angle. According to such a measuring device, it is possible to accurately measure the phase angle when measuring the leakage current of the resistance component.

[0013] In the measuring device according to an embodiment, the control unit may calculate the corrected phase angle based on the following formula (1). θ = θ1 - θ2 (1) However, in formula (1), θ represents the corrected phase angle, θ1 represents the phase angle, and θ2 represents the calibration phase angle. Thereby, the corrected phase angle can be calculated.

[0014] In the measuring device according to an embodiment, the control unit may calculate the leakage current of the resistance component based on the following formula (2). Ior = Io × cosθ (2) However, Ior represents the leakage current of the resistance component, and Io represents the leakage current. Thereby, the leakage current of the resistance component can be calculated.

[0015] In the measuring device according to one embodiment, the measuring device further includes an input unit capable of receiving an operation from a user. When the input unit receives from the user an operation to start a calibration operation, the control unit may cause the signal generator to output the sine wave and detect the calibration phase angle. Thereby, the calibration operation can be started according to an operation from the user.

[0016] In the measuring device according to one embodiment, the measuring device further includes a display unit. The control unit may cause the display unit to display the calculated leakage current of the resistance component. Thereby, the user can confirm the leakage current of the resistance component from the display on the display unit.

[0017] In the measuring device according to one embodiment, the signal generator outputs a sine wave having a frequency different from the measurement target frequency of the leakage current of the resistance component. The control unit may simultaneously execute detection of the calibration phase angle and calculation of the leakage current of the resistance component. Thereby, the calibration operation and the measurement operation can be simultaneously executed.

[0018] In the measuring device according to one embodiment, the signal generator outputs a sine wave having one frequency different from the measurement target frequency of the leakage current of the resistance component. The control unit may calculate the calibration phase angle at the measurement target frequency of the leakage current of the resistance component based on the calibration phase angle detected in a state where the signal generator is outputting a sine wave having one frequency different from the measurement target frequency of the leakage current of the resistance component. Thereby, by the signal generator outputting a sine wave having one frequency different from the measurement target frequency, the calibration operation and the measurement operation can be simultaneously executed.

[0019] In a measuring device according to an embodiment, the signal generator outputs sine waves at two frequencies different from the measurement target frequency of the resistance component leakage current, and the control unit is based on the calibration phase angles detected in a state where the signal generator is outputting the sine waves at two frequencies different from the measurement target frequency of the resistance component leakage current. The calibration phase angle at the measurement target frequency of the resistance component leakage current may be calculated. Thereby, by the signal generator outputting sine waves at two frequencies different from the measurement target frequency, the calibration operation and the measurement operation can be executed simultaneously.

[0020] In a measuring device according to an embodiment, one of the two frequencies may be a frequency higher than the measurement target frequency, and the other of the two frequencies may be a frequency lower than the measurement target frequency. Thereby, the calibration phase angle can be calculated with high accuracy.

[0021] A measurement method according to some embodiments is a measurement device capable of measuring a resistance component leakage current, a magnetic core that can be arranged so as to surround the periphery of a wiring, a first coil and a second coil wound around the magnetic core, a current measurement circuit connected to the first coil and capable of measuring the leakage current of the wiring, a voltage measurement circuit capable of measuring the voltage of the wiring, a phase angle detection circuit capable of detecting a phase angle between the leakage current and the voltage, and a signal generator capable of outputting a sine wave to the second coil and the phase angle detection circuit. A measurement method in a measurement device including: a step of detecting, by the phase angle detection circuit, a calibration phase angle between the current measured by the current measurement circuit when the signal generator is outputting the sine wave and the sine wave input from the signal generator; a step of calculating a correction phase angle based on the phase angle and the calibration phase angle; and a step of calculating a resistance component leakage current based on the leakage current and the correction phase angle. According to such a measurement method, it is possible to accurately measure the phase angle when measuring the resistance component leakage current.

Advantages of the Invention

[0022] According to the present disclosure, it is possible to provide a measuring device and a measuring method capable of accurately measuring a phase angle when measuring a leakage current of a resistance component.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0024] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0025] FIG. 1 is a schematic configuration diagram of a measuring device 10 according to an embodiment.

[0026] The measuring device 10 is a device capable of measuring the resistance component leakage current of a live wire. FIG. 1 is a diagram showing a state in which the measuring device 10 measures the resistance component leakage current of a wiring 5 connecting a switchboard 1 and a load 2. The wiring 5 is a wiring through which current is flowing, and the wiring 5 is a live wire.

[0027] In addition, in FIG. 1, the fact that the measuring device 10 measures the resistance component leakage current of the wiring 5 connecting the switchboard 1 and the load 2 is shown as an example. The measuring device 10 is not limited to such a wiring 5, and can measure the resistance component leakage current of any live wire.

[0028] The wiring 5 includes a signal line 5a and a GND line 5b. The wiring 5 may be, for example, a coaxial cable in which the GND line 5b is wound around the signal line 5a.

[0029] In the example shown in FIG. 1, a current I1 flows through the signal line 5a from the switchboard 1 toward the load 2. Also, a current I2 flows through the GND line 5b from the load 2 toward the switchboard 1. When no leakage current flows from the wiring 5, the current I1 and the current I2 are equal.

[0030] When a leakage current flows from the wiring 5, the leakage current Io is the difference between the current I1 and the current I2 and is represented by the following formula (1). Io = I1 - I2 (1)

[0031] The leakage current Io is the vector sum of a resistance component leakage current Ior that flows from the signal line 5a of the wiring 5 to the GND via the resistor 4 and a capacitance component leakage current Ioc that flows from the signal line 5a of the wiring 5 to the GND via the capacitor 3.

[0032] The resistor 4 shown in FIG. 1 does not image a resistor element but images a resistance component through which the resistance component leakage current Ior flows. Also, the capacitor 3 shown in FIG. 1 does not image a capacitor element but images a capacitor component through which the capacitance component leakage current Ioc flows.

[0033] FIG. 2 is a vector diagram showing the relationship between the leakage current Io, the resistance component leakage current Ior, and the capacitance component leakage current Ioc. The θ shown in FIG. 2 is the phase angle between the leakage current Io flowing through the wiring 5 and the voltage of the wiring 5. In the present embodiment, the "voltage of the wiring 5" means the difference between the voltage of the signal line 5a and the voltage of the GND line 5b.

[0034] As shown in FIG. 2, the resistance component leakage current Ior is represented by the following formula (2) based on the leakage current Io and the phase angle θ. Ior = Io × cos θ (2)

[0035] Referring to FIG. 1 again, the configuration and functions of the measuring device 10 will be described schematically.

[0036] The measuring device 10 includes a magnetic core 11, a first coil L1, a second coil L2, a current measurement circuit 12, a voltage measurement circuit 13, a signal generator 14, a phase angle detection circuit 15, a control unit 16, an input unit 17, a display unit 18, a first switch SW1, a second switch SW2, and a third switch SW3.

[0037] The magnetic core 11 can be arranged to surround the wiring 5 which is the measurement object of the resistance component leakage current. The magnetic core 11 may be, for example, in a ring shape. The magnetic core 11 may have a configuration where a part is openable and closable. When the magnetic core 11 has a configuration where a part is openable and closable, the wiring 5 can be sandwiched.

[0038] The first coil L1 is a coil wound around the magnetic core 11. The first coil L1 can detect the leakage current of the wiring 5 sandwiched by the magnetic core 11.

[0039] The second coil L2 is a coil wound around the magnetic core 11. The second coil L2 is a coil used when performing a calibration operation in the measuring device 10.

[0040] When a sine wave is input from the signal generator 14 to the second coil L2 during the calibration operation, a sine wave current flows through the second coil L2. Then, the second coil L2 generates a magnetic flux corresponding to the sine wave inside the magnetic core 11. Thereupon, a current flows through the first coil L1, and the first coil L1 detects a current corresponding to the sine wave.

[0041] The current measurement circuit 12 is connected to the first coil L1. The leakage current of the wiring 5 detected by the first coil L1 is input to the current measurement circuit 12. Thereby, the current measurement circuit 12 can measure the leakage current of the wiring 5.

[0042] The current measurement circuit 12 may include a current-voltage conversion circuit, an amplification circuit, etc. The current measurement circuit 12 outputs a signal corresponding to the measured leakage current of the wiring 5 to the phase angle detection circuit 15 and the control unit 16. The current measurement circuit 12 may output a signal corresponding to the measured leakage current of the wiring 5 as a current or as a voltage.

[0043] The voltage measurement circuit 13 can be connected to the signal line 5a and the GND line 5b of the wiring 5. The voltage measurement circuit 13 measures the difference between the voltage of the signal line 5a and the voltage of the GND line 5b as the voltage of the wiring 5. The voltage measurement circuit 13 may include a differential amplification circuit, etc. The voltage measurement circuit 13 outputs a signal corresponding to the measured voltage of the wiring 5 to the phase angle detection circuit 15 via the third switch SW3.

[0044] The signal generator 14 is a signal generator of an arbitrary configuration capable of outputting two synchronized sine waves. The signal generator 14 is connected to the second coil L2 via the first switch SW1. The signal generator 14 is connected to the phase angle detection circuit 15 via the second switch SW2.

[0045] When the calibration operation is performed in the measuring device 10, the signal generator 14 outputs a sine wave synchronized with the second coil L2 and the phase angle detection circuit 15.

[0046] The phase angle detection circuit 15 is a circuit capable of detecting the phase angle between two input signals.

[0047] When the measurement operation is performed in the measuring device 10, the phase angle detection circuit 15 detects the phase angle between the leakage current measured by the current measurement circuit 12 and the voltage measured by the voltage measurement circuit 13. The phase angle detection circuit 15 outputs the detected phase angle to the control unit 16.

[0048] When the calibration operation is performed in the measuring device 10, the phase angle detection circuit 15 detects the calibration phase angle between the current measured by the current measurement circuit 12 when the signal generator 14 outputs a sine wave and the sine wave input from the signal generator 14. In the present embodiment, the phase angle between the current measured by the current measurement circuit 12 when the signal generator 14 outputs a sine wave and the sine wave input from the signal generator 14 may be referred to as the "calibration phase angle". The phase angle detection circuit 15 outputs the detected calibration phase angle to the control unit 16.

[0049] The control unit 16 controls the entire measuring device 10 and each block of the measuring device 10. The control unit 16 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for specific processing. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0050] Details of the operation of the control unit 16 will be described later.

[0051] The input unit 17 includes an interface capable of receiving operations from the user. The input unit 17 may include, for example, buttons.

[0052] The display unit 18 can display various data. The display unit 18 may include, for example, an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescent) display.

[0053] The first switch SW1 is connected between the signal generator 14 and the second coil L2. The first switch SW1 can turn on / off the connection between the signal generator 14 and the second coil L2 according to the command of the control unit 16. The first switch SW1 may be a switch of any configuration capable of switching on / off the electrical connection.

[0054] The second switch SW2 is connected between the signal generator 14 and the phase angle detection circuit 15. The second switch SW2 can turn on / off the connection between the signal generator 14 and the phase angle detection circuit 15 according to the command of the control unit 16. The second switch SW2 may be a switch of any configuration capable of switching on / off the electrical connection.

[0055] The third switch SW3 is connected between the voltage measurement circuit 13 and the phase angle detection circuit 15. The third switch SW3 can turn on / off the connection between the voltage measurement circuit 13 and the phase angle detection circuit 15 according to the command of the control unit 16. The third switch SW3 may be a switch of any configuration capable of switching on / off the electrical connection.

[0056] (Operation of the measuring device) When measuring the resistive component leakage current, the measuring device 10 executes a calibration operation and a measurement operation. The calibration operation and the measurement operation will be described in order.

[0057] <Calibration operation> First, the calibration operation of the measuring device 10 will be described. By executing the calibration operation immediately before executing the measurement operation, the measuring device 10 can correct the phase advance or delay caused by the magnetic core 11, the first coil L1, and the current measurement circuit 12.

[0058] FIG. 3 is a diagram showing the state when the measuring device 10 is performing the calibration operation. When performing the calibration operation, the magnetic core 11 does not sandwich the wiring 5. Therefore, in FIG. 3, the switchboard 1, the wiring 5, the load 2, the capacitor 3, and the resistor 4 are not shown.

[0059] The input unit 17 can receive an operation from the user to start the calibration operation. When the input unit 17 receives an operation from the user to start the calibration operation, the control unit 16 starts the calibration operation.

[0060] When starting the calibration operation, the control unit 16 turns on the first switch SW1 and the second switch SW2. Also, the control unit 16 turns off the third switch.

[0061] Subsequently, the control unit 16 causes the signal generator 14 to generate a sine wave. The signal generator 14 outputs the sine wave to the second coil L2 via the first switch SW1. Also, the signal generator 14 outputs the sine wave to the phase angle detection circuit 15 via the second switch SW2.

[0062] The frequency of the sine wave output by the signal generator 14 may be the same as the measurement target frequency of the resistance component leakage current. For example, when the measurement target frequency is 50 Hz, the frequency of the sine wave output by the signal generator 14 may be 50 Hz. Also, for example, when the measurement target frequency is 60 Hz, the frequency of the sine wave output by the signal generator 14 may be 60 Hz.

[0063] When a sine wave is input from the signal generator 14 to the second coil L2, the first coil L1 detects a current corresponding to the sine wave input to the second coil L2. The current measurement circuit 12 measures the current flowing through the first coil L1 and outputs a signal corresponding to the measured current to the phase angle detection circuit 15.

[0064] The phase angle detection circuit 15 detects a calibration phase angle between the current measured by the current measurement circuit 12 when the signal generator 14 is outputting a sine wave and the sine wave input from the signal generator 14. Here, the calibration phase angle detected by the phase angle detection circuit 15 is the phase angle caused by the magnetic core 11, the first coil L1, and the current measurement circuit 12.

[0065] The phase angle detection circuit 15 outputs the detected calibration phase angle to the control unit 16. The control unit 16 holds the calibration phase angle.

[0066] <Measurement operation> Subsequently, the measurement operation of the measuring device 10 will be described. When the calibration operation is completed and the control unit 16 holds the calibration phase angle, the measuring device 10 can execute the measurement operation.

[0067] FIG. 1 is a diagram showing the state of the measuring device 10 during the measurement operation. When performing the measurement operation, the magnetic core 11 sandwiches the wiring 5 that is the measurement target of the resistance component leakage current. At this time, a current is flowing through the wiring 5, and the wiring 5 is a live wire.

[0068] When starting the measurement operation, the control unit 16 turns off the first switch SW1 and the second switch SW2. Also, the control unit 16 turns on the third switch. At this time, the control unit 16 does not cause the signal generator 14 to output a sine wave.

[0069] The first coil L1 detects the leakage current of the wiring 5 sandwiched by the magnetic core 11. The leakage current of the wiring 5 detected by the first coil L1 is input to the current measurement circuit 12. Thereby, the current measurement circuit 12 measures the leakage current of the wiring 5. The current measurement circuit 12 outputs a signal corresponding to the measured leakage current to the phase angle detection circuit 15.

[0070] The voltage measurement circuit 13 measures the difference between the voltage of the signal line 5a and the voltage of the GND line 5b as the voltage of the wiring 5. The voltage measurement circuit 13 outputs a signal corresponding to the measured voltage of the wiring 5 to the phase angle detection circuit 15 via the third switch SW3.

[0071] The phase angle detection circuit 15 detects the phase angle between the leakage current measured by the current measurement circuit 12 and the voltage of the wiring 5 measured by the voltage measurement circuit 13.

[0072] The phase angle detection circuit 15 outputs the detected phase angle to the control unit 16.

[0073] Based on the phase angle θ1 obtained from the phase angle detection circuit 15 in the measurement operation and the calibration phase angle θ2 obtained from the phase angle detection circuit 15 in the calibration operation, the control unit 16 calculates the corrected phase angle θ as shown in the following formula (3). θ = θ1 - θ2 (3)

[0074] In this way, by correcting the phase angle θ1 obtained in the measurement operation based on the calibration phase angle θ2 obtained in the calibration operation, the control unit 16 can calculate the corrected phase angle θ that corrects the advance or delay of the phase caused by the magnetic core 11, the first coil L1, and the current measurement circuit 12.

[0075] Based on the leakage current Io measured by the current measurement circuit 12 and the corrected phase angle θ calculated by the above formula (3), the control unit 16 calculates the resistive component leakage current Ior as shown in the following formula (4). Ior = Io × cosθ (4)

[0076] The control unit 16 causes the calculated resistive component leakage current Ior to be displayed on the display unit 18.

[0077] According to the measuring device 10 according to the above-described embodiment, it is possible to accurately measure the phase angle during the measurement of the resistive component leakage current. More specifically, the measuring device 10 includes a signal generator 14 capable of outputting a sine wave to the second coil L2 and the phase angle detection circuit 15, and the phase angle detection circuit 15 can detect the calibration phase angle between the current measured by the current measurement circuit 12 when the signal generator 14 outputs a sine wave and the sine wave input from the signal generator 14. Then, the control unit 16 calculates the corrected phase angle based on the phase angle between the leakage current and the voltage and the calibration phase angle, and calculates the resistive component leakage current based on the leakage current and the corrected phase angle. In this way, by detecting the calibration phase angle and calculating the corrected phase angle based on the phase angle and the calibration phase angle, the measuring device 10 can calculate the corrected phase angle that corrects the advance or delay of the phase caused by the magnetic core 11, the first coil L1, and the current measurement circuit 12. Therefore, the measuring device 10 can accurately measure the phase angle during the measurement of the resistive component leakage current.

[0078] Also, according to the measuring device 10 according to one embodiment, since the calibration phase angle can be automatically calculated, it is not necessary to adjust or correct the advance or delay of the phase during maintenance or the like. Therefore, the burden on the operator can be reduced. In addition, it is possible to eliminate the need to provide calibration equipment.

[0079] (Modification example) FIG. 4 is a diagram showing a schematic configuration of a measuring device 10a according to a modification example. With reference to FIG. 4, the measuring device 10a according to the modification example will be described.

[0080] The measuring device 10a according to the modification example is different from the operation of the measuring device 10 shown in FIG. 1 in that the calibration operation and the measurement operation are executed simultaneously.

[0081] Since the configuration of the measuring device 10a according to the modification example is the same as the configuration of the measuring device 10 shown in FIG. 1, the description of the configuration of the measuring device 10a will be omitted.

[0082] The measuring device 10a according to the modification example executes the calibration operation and the measurement operation simultaneously. Therefore, the measuring device 10a according to the modification example operates in a state where all of the first switch SW1, the second switch SW2, and the third switch SW3 are turned on, as shown in FIG. 4.

[0083] Note that, since it operates in a state where all of the first switch SW1, the second switch SW2, and the third switch SW3 are turned on, the measuring device 10a according to the modification example may not include the first switch SW1, the second switch SW2, and the third switch SW3. In this case, the portions of the first switch SW1, the second switch SW2, and the third switch SW3 may be short-circuited.

[0084] The signal generator 14 of the measuring device 10a according to the modification example outputs a sine wave having a frequency different from the measurement target frequency of the resistance component leakage current. For example, when the measurement target frequency of the resistance component leakage current is 50 Hz, the signal generator 14 outputs a sine wave having a frequency different from 50 Hz.

[0085] In this way, by setting the measurement target frequency of the resistance component leakage current and the frequency of the sine wave output by the signal generator 14 to different frequencies, the measuring device 10a can execute the calibration operation and the measurement operation simultaneously.

[0086] The measurement target frequency will be described as Freq_meas, and the frequency of the sine wave for calibration output by the signal generator 14 will be described as Freq_cal.

[0087] The phase angle detection circuit 15 detects the phase angle between the current of the frequency Freq_cal measured by the current measurement circuit 12 and the sine wave of the frequency Freq_cal input from the signal generator 14 as the calibration frequency phase angle.

[0088] The phase angle detection circuit 15 outputs the detected calibration frequency phase angle to the control unit 16.

[0089] Based on the calibration frequency phase angle θ obtained by the control unit 16 from the phase angle detection circuit 15, cal the calibration phase angle θ2 is calculated as shown in the following formula (5).

Equation

[0090] Also, the phase angle detection circuit 15 detects the phase angle θ1 between the leakage current of the frequency Freq_meas measured by the current measurement circuit 12 and the voltage of the frequency Freq_meas of the wiring 5 measured by the voltage measurement circuit 13.

[0091] The phase angle detection circuit 15 outputs the detected phase angle θ1 to the control unit 16.

[0092] Based on the phase angle θ1 obtained by the control unit 16 from the phase angle detection circuit 15 and the calibration phase angle θ2 calculated based on the above formula (5), the correction phase angle θ is calculated based on the above formula (3).

[0093] The signal generator 14 of the measuring device 10a according to the modification example may output a sine wave of one frequency different from the measurement target frequency of the resistance component leakage current as described above, or may output sine waves of two frequencies different from the measurement target frequency of the resistance component leakage current. Hereinafter, the operation when the signal generator 14 outputs sine waves of two frequencies different from the measurement target frequency of the resistance component leakage current will be described.

[0094] The measurement target frequency will be described as Freq_meas, one frequency of the sine wave for calibration output by the signal generator 14 as Freq_cal1, and the other frequency of the sine wave for calibration output by the signal generator 14 as Freq_cal2. Note that Freq_cal1 is a frequency smaller than Freq_meas, and Freq_cal2 is a frequency larger than Freq_meas.

[0095] The phase angle detection circuit 15 detects the phase angle between the current of the frequency of Freq_cal1 measured by the current measurement circuit 12 and the sine wave of the frequency of Freq_cal1 input from the signal generator 14 as the first calibration frequency phase angle.

[0096] The phase angle detection circuit 15 detects the phase angle between the current of the frequency of Freq_cal2 measured by the current measurement circuit 12 and the sine wave of the frequency of Freq_cal2 input from the signal generator 14 as the second calibration frequency phase angle.

[0097] The phase angle detection circuit 15 outputs the detected first calibration frequency phase angle and second calibration frequency phase angle to the control unit 16.

[0098] The control unit 16 calculates the calibration phase angle θ2 based on the first calibration frequency phase angle θ cal1 and the second calibration frequency phase angle θ cal2 as shown in the following formulas (6) to (8).

Equation

Equation

[0099] Further, the phase angle detection circuit 15 detects a phase angle θ1 between the leakage current of the frequency of Freq_meas measured by the current measurement circuit 12 and the voltage of the frequency of Freq_meas of the wiring 5 measured by the voltage measurement circuit 13.

[0100] The phase angle detection circuit 15 outputs the detected phase angle θ1 to the control unit 16.

[0101] Based on the phase angle θ1 acquired from the phase angle detection circuit 15 and the calibration phase angle θ2 calculated based on the above-described formulas (6) to (8), the control unit 16 calculates the correction phase angle θ based on the above-described formula (3).

[0102] In this way, by the signal generator 14 outputting sine waves of two frequencies different from the measurement target frequency, compared with the case where the signal generator 14 outputs a sine wave of one frequency different from the measurement target frequency, the measurement device 10a according to the comparative example can calculate the correction phase angle θ with high accuracy over a wide frequency range.

[0103] (Comparative Example) FIG. 5 is a schematic configuration diagram of a measurement device 200 according to the comparative example.

[0104] The measurement device 200 according to the comparative example includes a magnetic core 11, a first coil L1, a current measurement circuit 12, a voltage measurement circuit 13, a phase angle detection circuit 15, a control unit 16, an input unit 17, and a display unit 18.

[0105] The measurement device 200 according to the comparative example is different from the measurement device 10 according to the embodiment shown in FIG. 1 in that it does not include a second coil L2, a signal generator 14, a first switch SW1, a second switch SW2, and a third switch SW3.

[0106] Since the measuring device 200 according to the comparative example does not include the second coil L2 and the signal generator 14, it cannot perform the calibration operation that the measuring device 10 shown in FIG. 1 can perform.

[0107] Therefore, the measuring device 200 according to the comparative example cannot correct the phase advance or delay caused by the magnetic core 11, the first coil L1, and the current measurement circuit 12 by means of a calibration operation. Accordingly, the measuring device 200 according to the comparative example cannot accurately measure the phase angle when measuring the resistive component leakage current.

[0108] It is obvious to those skilled in the art that the present disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the foregoing description is illustrative and not restrictive. The scope of the disclosure is defined by the appended claims rather than by the foregoing description. Some changes within the equivalent scope of any change are included therein.

[0109] For example, the arrangement and number of each of the above-described components are not limited to the content shown in the above description and the drawings. The arrangement and number of each component may be arbitrarily configured as long as its function can be realized.

[0110] For example, in the above-described embodiment, the measuring device 10 that can correct the phase angle when measuring the resistive component leakage current has been described. However, the above-described technique for correcting the phase angle is also applicable to other devices that measure the phase angle. For example, it is also important to accurately measure the phase angle in a clamp power meter, but the above-described technique for correcting the phase angle is also applicable to a clamp power meter. If the above-described technique for correcting the phase angle is implemented in a clamp power meter, the clamp power meter can accurately measure the phase angle and thus can accurately measure the power.

Description of Reference Numerals

[0111] 1 Switchboard 2 Load 3 Capacitor 4 Resistance 5 Wiring 5a Signal Line 5b GND Line 10, 10a Measuring Device 11 Magnetic Core 12 Current Measurement Circuit 13 Voltage Measurement Circuit 14 Signal Generator 15 Phase Angle Detection Circuit 16 Control Unit 17 Input Unit 18 Display Unit L1 First Coil L2 Second Coil SW1 First Switch SW2 Second Switch SW3 Third Switch 200 Measuring Device

Claims

1. A measuring device capable of measuring the leakage current of a resistance component, comprising: A magnetic core that can be arranged to surround the wiring; A first coil and a second coil wound around the magnetic core; A current measurement circuit connected to the first coil and capable of measuring the leakage current of the wiring; A voltage measurement circuit capable of measuring the voltage of the wiring; A phase angle detection circuit capable of detecting the phase angle between the leakage current and the voltage; A signal generator capable of outputting a sine wave to the second coil and the phase angle detection circuit; A control unit; and The phase angle detection circuit can detect a calibration phase angle between the current measured by the current measurement circuit when the signal generator outputs the sine wave and the sine wave input from the signal generator; The control unit: calculates a correction phase angle based on the phase angle and the calibration phase angle; calculates the leakage current of the resistance component based on the leakage current and the correction phase angle; The signal generator simultaneously outputs sine waves of two frequencies different from the measurement target frequency of the leakage current of the resistance component; The control unit calculates the calibration phase angle at the measurement target frequency of the leakage current of the resistance component based on the calibration phase angles detected in the state where the signal generator outputs sine waves of two frequencies different from the measurement target frequency of the leakage current of the resistance component; The control unit simultaneously executes detection of the calibration phase angle and calculation of the leakage current of the resistance component. A measuring device.

2. In the measuring device according to claim 1, The control unit calculates the correction phase angle based on the following formula (1). A measuring device. θ = θ1 - θ2 (1) However, in formula (1), θ represents the correction phase angle, θ1 represents the phase angle, and θ2 represents the calibration phase angle.

3. In the measuring device according to claim 2, The control unit calculates the resistive component leakage current based on the following formula (2). A measuring device. Ior = Io × cos θ (2) However, Ior represents the resistive component leakage current, and Io represents the leakage current.

4. In the measuring device according to claim 1, It further includes an input unit capable of receiving an operation from a user, When the input unit receives from the user an operation to start a calibration operation, the control unit causes the signal generator to output the sine wave and detects the calibration phase angle. A measuring device.

5. In the measuring device according to claim 1, It further includes a display unit, The control unit causes the calculated resistive component leakage current to be displayed on the display unit. A measuring device.

6. In the measuring device according to claim 1, One of the two frequencies is a frequency higher than the measurement target frequency, and the other of the two frequencies is a frequency lower than the measurement target frequency. A measuring device.

7. A measuring method in a measuring device capable of measuring a resistive component leakage current, the measuring device comprising: a magnetic core that can be arranged so as to surround the periphery of a wiring; a first coil and a second coil wound around the magnetic core; a current measuring circuit connected to the first coil and capable of measuring the leakage current of the wiring; a voltage measuring circuit capable of measuring the voltage of the wiring; a phase angle detecting circuit capable of detecting a phase angle between the leakage current and the voltage; and a signal generator capable of outputting a sine wave to the second coil and the phase angle detecting circuit. The method includes: A step of detecting a calibration phase angle between the current measured by the current measurement circuit when the signal generator outputs the sine wave and the sine wave input from the signal generator by the phase angle detection circuit; A step of calculating a correction phase angle based on the phase angle and the calibration phase angle; A step of calculating a resistive component leakage current based on the leakage current and the correction phase angle; Including, The signal generator simultaneously outputs sine waves of two frequencies different from the measurement target frequency of the resistive component leakage current, The step of detecting the calibration phase angle calculates the calibration phase angle at the measurement target frequency of the resistive component leakage current based on the calibration phase angle detected in a state where the signal generator outputs sine waves of two frequencies different from the measurement target frequency of the resistive component leakage current, A measurement method for simultaneously executing the step of detecting the calibration phase angle and the step of calculating the resistive component leakage current.

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