Measuring device and measuring method

Abstract

To enable the physical quantity of the voltage to be measured applied to a core wire to be measured from above a cable coating with higher accuracy.SOLUTION: A measuring device includes a control unit for: injecting an injection current of a second frequency via an insulator to a core wire to which the voltage of a first frequency to be measured is applied; acquiring a composite current composed of the injection current and a leak current of the voltage to be measured having leaked from the core wire via the insulator that are overlapping each other in a circuit unit; analyzing the composite current and calculating measurement effective electric power and measurement reactive electric power that are effective and reactive electric powers based on the contribution of the voltage to be measured; calculating the voltage to be measured on the basis of the measurement effective electric power, the measurement reactive electric power, the first frequency, the second frequency, the voltage of the injection current, and the current effective value of the leak current; and outputting the calculated voltage to be measured.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] With the progress of 24-hour operation of equipment and systemization, etc., the demand for maintenance while the equipment is operating has been increasing. As part of such equipment maintenance, a metal clip is connected to a screw or the like in a live part such as a switchboard, and the voltage, phase, etc. of the live part are measured.

[0003] The live part of the switchboard does not have a structure for clipping, and is often densely packed in a narrow space. Therefore, the method of connecting a clip to the live part and measuring the voltage, etc. may cause a risk of electric shock to the operator. Risks such as a power short circuit during clipping, a short circuit due to clip dropout, and the disappearance of measurement data due to clip dropout may also occur.

[0004] Patent Document 1 describes a non-contact voltage measuring device that measures an alternating voltage applied to the core wire of an electric wire through an insulator in contact with the core wire. The configuration of Patent Document 1 obtains the coupling capacitance based on an input signal obtained by dividing the voltage between the insulator and the electrode by changing the capacitance of a pre-provided reference capacitor, and measures the alternating voltage based on the value of this coupling capacitance. According to such a configuration, it is possible to measure the voltage to be measured applied to the core wire from above the cable sheath instead of the live part. Therefore, risks such as electric shock, short circuit, and disappearance of measurement data of the operator can be reduced.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the configuration of Patent Document 1 had room for improvement in the measurement accuracy of measuring the voltage or the like applied through the insulator in contact with the core wire of the coated electric wire.

[0007] Therefore, an object of the present disclosure is to enable measurement of the physical quantity of the voltage to be measured applied to the core wire from above the cable coating with higher accuracy.

Means for Solving the Problems

[0008] The measuring device according to some embodiments (1) injects an injection current of a second frequency into the core wire to which the voltage to be measured of the first frequency is applied, through the insulator, obtains a composite current composed of the injection current and the leakage current of the voltage to be measured leaking from the insulator, calculates a measured active power and a measured reactive power, which are the active power and the reactive power based on the contribution of the voltage to be measured, based on the composite current, calculates the voltage to be measured based on the measured active power, the measured reactive power, the first frequency, the second frequency, the voltage of the injection current, and the effective value of the current of the leakage current, outputs the voltage to be measured, and includes a control unit.

[0009] Thus, instead of directly acquiring a signal from the core wire to which the voltage to be measured is applied, the measuring device measures the leakage current flowing out through the coating from the core wire to which the voltage to be measured is applied, based on the signal acquired through the insulator. Therefore, the physical quantity of the voltage to be measured can be measured from above the cable coating. Further, the measuring device injects injection power of a second frequency different from the first frequency of the leakage current flowing out through the coating from the core wire to which the voltage to be measured is applied, and measures the voltage to be measured based on the active power and the reactive power based on the contribution of the voltage to be measured. Therefore, based on the frequency, the measuring device can distinguish the leakage current flowing out through the coating from the core wire to which the voltage to be measured is applied and the injection current while the live wire is in a live state, and can measure the voltage to be measured from above the cable coating with higher accuracy with a simple configuration.

[0010] In one embodiment, (2) In the measuring device of (1), the control unit calculates apparent power corresponding to the measured active power and the measured reactive power based on the measured active power, the measured reactive power, the first frequency, and the second frequency, and may calculate the voltage to be measured based on the calculated apparent power, the voltage of the injected current, and the effective current value of the leakage current.

[0011] In this way, since the measuring device calculates apparent power corresponding to the measured active power and the measured reactive power and calculates the voltage to be measured, it is possible to measure the voltage to be measured with higher accuracy according to the resistance component and the capacitance component of the insulator.

[0012] In one embodiment, (3) In the measuring device of (1) or (2), the control unit calculates the phase of the leakage current with respect to the injected current based on the calculated measured active power and the ratio of the measured reactive power, and may further output the calculated phase of the leakage current.

[0013] Therefore, the measuring device can measure not only the voltage to be measured but also the phase of the leakage current leaking from the insulator due to the voltage to be measured with higher accuracy.

[0014] In one embodiment, (4) In any one of the measuring devices of (1) to (3), the control unit measures the injected active power and the injected reactive power, which are the active power and the reactive power in the circuit unit measured by flowing the injected current in the circuit unit in a state where there is a contribution of the leakage current, The offset active power and the offset reactive power, which are the active power and the reactive power in the circuit unit measured by passing the injection current in a state where there is no contribution from the leakage current, are measured, The power obtained by offsetting the injection active power with the offset active power is calculated as the measured active power, The power obtained by offsetting the injection reactive power with the offset reactive power may be calculated as the measured reactive power.

[0015] In this way, the measuring device offsets the injection active power and the injection reactive power using the offset active power and the offset reactive power measured in a state where there is no contribution from the leakage current, measures the measured active power and the measured reactive power, and measures the voltage to be measured using such measured active power and measured reactive power. Therefore, according to the measuring device, it is possible to reduce the influence of the measurement environment and internal leakage, etc., and measure the physical quantity of the voltage to be measured with higher accuracy.

[0016] In one embodiment, (5) In any of the measuring devices according to (1) to (4), The control unit, In a state where there is no contribution from the injection current, the voltage of the leakage current of the voltage to be measured leaking from the core wire through the insulator is acquired, Based on the acquired voltage of the leakage current, the effective current value of the leakage current may be acquired.

[0017] In this way, the measuring device acquires the effective current value based on the measured value of the leakage current measured in a state where there is no contribution from the injection current. Therefore, the measuring device can measure the physical quantity of the voltage to be measured with higher accuracy using a more accurate effective current value.

[0018] The measurement methods according to some embodiments are (6) A measurement method of a measuring device including a control unit, The control unit, Inject an injection current of a second frequency into the core wire to which the measured voltage of the first frequency is applied, through an insulator. Obtain a composite current composed of the injection current and the leakage current of the measured voltage that has leaked through the insulator. Based on the composite current, calculate the measured active power and the measured reactive power, which are the active power and the reactive power based on the contribution of the measured voltage. Based on the measured active power, the measured reactive power, the first frequency, the second frequency, the voltage of the injection current, and the effective current value of the leakage current, calculate the measured voltage. Output the calculated measured voltage. Including.

[0019] In this way, the measurement method does not directly acquire a signal from the core wire to which the measured voltage is applied, but measures the leakage current flowing out through the coating from the core wire to which the measured voltage is applied based on the signal acquired through the insulator. Therefore, the physical quantity of the measured voltage can be measured from above the cable coating. In addition, the measurement method injects an injection power of a second frequency different from the first frequency of the leakage current flowing out through the coating from the core wire to which the measured voltage is applied, and measures the measured voltage based on the active power and the reactive power based on the contribution of the measured voltage. Therefore, the measurement method can distinguish the leakage current flowing out through the coating from the core wire to which the measured voltage is applied and the injection current while the live wire is in a live state based on the frequency, and measure the measured voltage from above the cable coating with higher accuracy with a simple configuration.

[0020] In one embodiment, (7) In the measurement method of (6), The control unit Based on the measured active power, the measured reactive power, the first frequency, and the second frequency, calculate the apparent power corresponding to the measured active power and the measured reactive power. Based on the calculated apparent power, the voltage of the injection current, and the effective current value of the leakage current, the measured voltage may be calculated.

[0021] Thus, the measurement method can calculate the apparent power corresponding to the measured active power and the measured reactive power to calculate the voltage to be measured, and can measure the voltage to be measured with higher accuracy according to the resistance component and the capacitance component of the insulator.

[0022] In one embodiment, In the measurement method of (8), (6) or (7), the control unit calculates the phase of the leakage current with respect to the injection current based on the ratio of the calculated measured active power and the measured reactive power, and may further output the calculated phase of the leakage current.

[0023] Therefore, the measurement method can measure not only the voltage to be measured but also the phase of the leakage current leaking from the insulator due to the voltage to be measured with higher accuracy.

[0024] In one embodiment, In any of the measurement methods of (9), (6) to (8), the control unit measures the injection active power and the injection reactive power, which are the active power and the reactive power in the circuit unit measured by flowing the injection current in the circuit unit in a state where there is a contribution of the leakage current, measures the offset active power and the offset reactive power, which are the active power and the reactive power in the circuit unit measured by flowing the injection current in the circuit unit in a state where there is no contribution of the leakage current, calculates the power obtained by offsetting the injection active power with the offset active power as the measured active power, and may calculate the power obtained by offsetting the injection reactive power with the offset reactive power as the measured reactive power.

[0025] In this way, the measurement method offsets the injected active power and the injected reactive power using the offset active power and the offset reactive power measured in a state where there is no contribution from the leakage current, measures the measured active power and the measured reactive power, and measures the voltage to be measured using such measured active power and measured reactive power. Therefore, according to the measurement method, it is possible to reduce the influence of the measurement environment and internal leakage, etc., and measure the physical quantity of the voltage to be measured with higher accuracy.

[0026] In one embodiment, (10) In any of the measurement methods from (6) to (9), the control unit acquires the voltage of the leakage current of the voltage to be measured that has leaked from the core wire through the insulator in a state where there is no contribution from the injected current, Based on the acquired voltage of the leakage current, the effective current value of the leakage current may be acquired.

[0027] In this way, the measurement method acquires the effective current value based on the measured value of the leakage current measured in a state where there is no contribution from the injected current. Therefore, the measurement method can measure the physical quantity of the voltage to be measured with higher accuracy using a more accurate effective current value.

Advantages of the Invention

[0028] According to the present disclosure, the physical quantity of the voltage to be measured applied to the core wire from above the cable sheath can be measured with higher accuracy.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0030] <Comparative Example> As a configuration according to the comparative example, Patent Document 1 (Claim 1) describes, "In a non-contact voltage measuring device that measures an alternating voltage applied to a core wire of an electric wire through an insulator in contact with the core wire, a first electrode that captures an input signal through the insulator, and a reference capacitor provided in advance whose capacitance is changed to divide the input signal between the capacitance of the insulator and the capacitance between the insulator and the electrode, and a voltage measuring means for obtaining the coupling capacitance based on the input signal and obtaining the alternating voltage from the value of this coupling capacitance, a second electrode that is arranged at a slight distance from the electric wire so as to be coupled only by a capacitance component and not in contact with the resistance component and detects an alternating voltage in phase with the alternating voltage through the insulator, a phase difference detecting means for detecting the phase difference between the alternating voltage obtained by the voltage measuring means and the alternating voltage obtained by the second electrode, and a correcting means for inputting the phase difference obtained by this phase difference detecting means and the voltage from the voltage measuring means and correcting the alternating voltage obtained by the voltage measuring means."

[0031] The capacitance of the insulator covering the electric wire is extremely small and may vary greatly depending on measurement conditions such as temperature and humidity. Therefore, the configuration of the comparative example for measuring an alternating voltage based on the capacitance of the insulator had room for improvement in measurement accuracy.

[0032] <Embodiment> Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, parts having the same configuration or function are denoted by the same reference numerals. In the description of this embodiment, redundant descriptions of the same parts may be omitted or simplified as appropriate.

[0033] FIG. 1 is a diagram showing a configuration example of a measuring device 1 according to an embodiment. The measuring device 1 measures the phase θ of the voltage V to be measured applied to the cable 80 and the leakage current I flowing out through the coating. The cable 80 includes a core wire 81 to which the voltage V to be measured is applied and a cable coating 82 which is an insulator covering the core wire 81. The measuring device 1 includes a device main body 10, an insulating clip 41, and a wiring 45. M、 and the leakage current I flowing out through the coating M of the phase θ M The insulating clip 41 contacts the cable coating 82 and acquires the current I (the effective current value of the leakage current: I) flowing out through the coating from the core wire 81 to which the voltage V to be measured is applied. As shown in FIG. 1, the insulating clip 41 contacts the cable coating 82 of the cable 80 by sandwiching the cable coating 82 with a pair of clip electrodes 40a and 40b. Hereinafter, the clip electrodes 40a and 40b may be collectively referred to as the "clip electrode 40". M The insulating clip 41 may include a gripping structure 47 that presses the clip electrode 40 of FIG. 1 against the cable 80. FIG. 2 is a diagram showing a configuration example of the gripping structure 47 included in the insulating clip 41 of FIG. 1. The gripping structure 47 includes an arm portion 471, a contact portion 472, and a gripping portion 473. The gripping structure 47 presses the pair of clip electrodes 40a and 40b against the cable coating 82 by using the elastic force of a leaf spring or the like by the arm portion 471. In the present embodiment, the contact portion 472 which is an end portion of the arm portion 471 is connected to the clip electrodes 40a and 40b via an adhesive portion 408 (see FIG. 3). The gripping portion 473 is operated by an operator to widen the length between the clip electrodes 40a and 40b.

[0034] The insulating clip 41 contacts the cable coating 82 and acquires the current I flowing out through the coating from the core wire 81 to which the voltage V to be measured is applied. M The insulating clip 41 contacts the cable coating 82 and acquires the current I flowing out through the coating from the core wire 81 to which the voltage V to be measured is applied. M (the effective current value of the leakage current: I M ) As shown in FIG. 1, the insulating clip 41 contacts the cable coating 82 of the cable 80 by sandwiching the cable coating 82 with a pair of clip electrodes 40a and 40b. Hereinafter, the clip electrodes 40a and 40b may be collectively referred to as the "clip electrode 40".

[0035] The insulating clip 41 may include a gripping structure 47 that presses the clip electrode 40 of FIG. 1 against the cable 80. FIG. 2 is a diagram showing a configuration example of the gripping structure 47 included in the insulating clip 41 of FIG. 1. The gripping structure 47 includes an arm portion 471, a contact portion 472, and a gripping portion 473. The gripping structure 47 presses the pair of clip electrodes 40a and 40b against the cable coating 82 by using the elastic force of a leaf spring or the like by the arm portion 471. In the present embodiment, the contact portion 472 which is an end portion of the arm portion 471 is connected to the clip electrodes 40a and 40b via an adhesive portion 408 (see FIG. 3). The gripping portion 473 is operated by an operator to widen the length between the clip electrodes 40a and 40b.

[0036] The clip electrode 40 has an electrode 402 that acquires an electrical signal from the cable sheath 82 via an insulator portion 401. FIG. 3 is a cross-sectional view showing a configuration example of the clip electrode 40 in FIG. 2. The clip electrode 40 includes an insulator portion 401, an electrode 402, an insulator portion 403, a shield 404, insulator portions 405 and 406, and an adhesive portion 408.

[0037] The insulator portion 401 is an insulator that contacts the cable sheath 82 of the cable 80. The insulator portion 401 may be formed of, for example, rubber containing ethylene propylene rubber. The electrode 402 is a conductor that acquires an electrical signal from the cable sheath 82 via the insulator portion 401. The electrode 402 outputs the electrical signal acquired from the cable sheath 82 to the apparatus main body 10 via the wiring 45.

[0038] The insulator portion 403 is an insulator that covers the periphery of the electrode 402 to prevent short circuits. The shield 404 is a conductor that covers the electrode 402 through the insulator portion 403 to suppress the influence of external electromagnetic fields and electromagnetic waves. The insulator portion 405 is an insulator that constitutes the housing of the clip electrode 40. The insulator portion 406 is an insulator that prevents the cable 80 from moving relative to the insulator portion 401. The insulator portion 406 may be provided as a protrusion at the edge of the insulator portion 401. The insulator portions 403, 405, and 406 may be formed of, for example, a resin containing acrylic.

[0039] The insulator portion 401, the electrode 402, the insulator portion 403, the shield 404, and the insulator portions 405 and 406 are adhered to each other by the adhesive portion 408. The adhesive portion 408 may be formed of, for example, an insulating adhesive (binder).

[0040] In the examples of FIGS. 2 and 3, the contact portion 472 of the gripping structure 47 is fixed to the outer surface of the insulator portion 405 by the adhesive portion 408. Therefore, the operator can operate the gripping portion 473 to widen the length between the clip electrodes 40a and 40b, and attach and detach the insulating clip 41 to and from the cable 80.

[0041] FIG. 4 is a diagram showing a configuration example of the measuring device 1 including the circuit configuration of the device main body 10 of FIG. 1. As shown in FIG. 4, the device main body 10 includes a circuit unit 71 and a control unit 72. The circuit unit 71 outputs an electrical signal to the cable 80 and acquires a response from the cable 80. The control unit 72 controls the operation of the circuit unit 71 and provides an interface with the operator.

[0042] The circuit unit 71 includes operational amplifiers 11 to 14, switches 21 and 22, a resistor 25, an injection terminal 31, and measurement terminals 35 to 37.

[0043] The operational amplifiers 11 to 14 are electronic circuit modules of an amplifier having a non-inverting input terminal (+), an inverting input terminal (-), and an output terminal. The operational amplifiers 11 to 14 amplify the potential difference between the non-inverting input terminal and the inverting input terminal at a predetermined amplification factor (gain) and output it from the output terminal. The operational amplifier 11 includes a non-inverting input terminal connected to the output terminal of the operational amplifier 13 and the resistor 25, an inverting input terminal connected to the output terminal of the operational amplifier 14, and an output terminal connected to the measurement terminal 36. The operational amplifier 12 (I / V amplifier) includes a non-inverting input terminal connected to the ground (GND), an inverting input terminal connected to the switch 21, and an output terminal connected to the measurement terminal 37. The operational amplifier 13 includes a non-inverting input terminal connected to the injection terminal 31 and the measurement terminal 35, an inverting input terminal connected to the output terminal of the operational amplifier 14, and an output terminal connected to the non-inverting input terminal of the operational amplifier 11 and the resistor 25. The operational amplifier 14 (buffer amplifier) includes a non-inverting input terminal connected to the switch 21 and the resistor 25, an inverting input terminal connected to the output terminal of the operational amplifier 14, and an output terminal connected to the inverting input terminals of the operational amplifiers 11, 13, and 14.

[0044] One end of switch 21 is connected to switch 22. By means of a switching operation, switch 21 connects either the inverting input terminal of operational amplifier 12, the non-inverting input terminal of operational amplifier 14, or resistor 25 to switch 22. One end of switch 22 is connected to switch 21, and the other end is connected to clip electrode 40. Switch 22 connects or disconnects between switch 21 and clip electrode 40 by means of a switching operation. Resistor 25 has a resistance value of R x .

[0045] Injection terminal 31 outputs an injection current to the non-inverting input terminal of operational amplifier 13. The injection current is an AC signal of voltage V t and frequency F t (second frequency).

[0046] Measurement terminals 35 to 37 output measurement signals V1 to V3. Measurement signal V1 output by measurement terminal 35 is the same as voltage V t of the injection current output by injection terminal 31. Measurement signal V2 output by measurement terminal 36 is the current output from the output terminal of operational amplifier 11. When switch 21 is connected to the resistor 25 side and switch 22 is connected, measurement signal V2 corresponds to the combined current obtained by superimposing the injection current on the leakage current of the measured voltage V M . When switch 22 is open, measurement signal V2 corresponds to the current flowing through circuit unit 71 by injecting the injection current into circuit unit 71. Measurement signal V3 output by measurement terminal 37 is the current output from the output terminal of operational amplifier 12. Measurement signal V3 is the voltage V M of the leakage current leaking from core wire 81 via cable sheath 82 and insulator portion 401 when switch 21 is connected to the operational amplifier 12 side.

[0047] Control unit 72 includes a control section 721, a storage section 722, an input section 723, and an output section 724.

[0048] The control unit 721 includes one or more processors. The control unit 721 is communicably connected to each component constituting the apparatus main body 10 and controls the operation of the entire measuring apparatus 1. For example, the control unit 721 may control the switching of the switches 21 and 22, the input of the injection current from the injection terminal 31, the voltage measurement at the measurement terminals 35 to 37, and the analysis of the voltage measurement values.

[0049] The storage unit 722 includes one or more memories. The storage unit 722 stores any information used for the operation of the measuring apparatus 1. For example, the measuring apparatus 1 may store information regarding the voltage measurement of the voltage V M applied to the core wire 81.

[0050] The input unit 723 includes one or more input interfaces that receive the input operations of the operator and acquire the input information based on the operations of the operator. For example, the input unit 723 may be a physical key, a capacitance key, a touch screen provided integrally with the display of the output unit 724, etc., but is not limited thereto.

[0051] The output unit 724 includes one or more output interfaces that output information to the operator and notify the operator. For example, the output unit 724 may be a display that outputs information as an image, etc., but is not limited thereto.

[0052] In the present embodiment, the apparatus main body 10 includes the circuit unit 71 and the control unit 72, but a part of these functions may be realized by an external apparatus.

[0053] Hereinafter, for the sake of simplicity of explanation, an example in which the measuring apparatus 1 measures the voltage V M applied to the core wire 81 and the phase θ M of the leakage current based on the electrical signal acquired from one clip electrode 40 will be described. As shown in FIGS. 1 and 2, when receiving electrical signals from a plurality of clip electrodes 40, the measuring apparatus 1 provides a circuit unit 71 for each of the clip electrodes 40, so that the voltage V M applied to the core wire 81 and the phase θ Mcan be measured.

[0054] In the example of FIG. 4, the voltage V to be measured is applied from the power source 84 to the core wire 81. M The voltage V to be measured M is an alternating current signal with a frequency F M (first frequency), voltage V M , and phase θ M . When the clip electrode 40 is brought into contact with the cable sheath 82, the leakage current I M of the voltage V to be measured M (effective current value: I M ) leaks out to the clip electrode 40. Here, the resistance component 87 and capacitance component 88 of the cable sheath 82 also include the contributions of the resistance component and capacitance component of the insulator portion 401. Hereinafter, when the frequency F M of the voltage V to be measured M is known, the operation of the measuring device 1 for measuring the voltage V to be measured M and the phase θ of the leakage current M will be described. For the sake of simplicity of explanation, hereinafter, the description of the operations related to the gains of the operational amplifiers 11 to 14 will be omitted.

[0055] The measuring device 1 connects the switch 21 to the resistor 25 side and connects the switch 22. In such a state, the measuring device 1 applies an injection current (for example, V t = 8V, F t = 40 Hz) from the injection terminal 31. In this case, the combined current obtained by combining the current flowing from the circuit unit 71 to the cable sheath 82 due to the injection current and the leakage current I M of the voltage V to be measured leaking from the core wire 81 through the cable sheath 82 to the circuit unit 71 M flows through the resistor 25 (for example, R x = 1 to 10 MΩ). The measurement terminal 36 outputs a measurement signal V2 of the voltage V2 proportional to the magnitude of such a combined current. The measurement terminal 35 is the voltage V of the injection current tOutputs the same measurement signal V1. Therefore, the measuring device 1 calculates the injected active power Ix_Active, which is the active power of the combined current, and the injected reactive power Ix_Reactive, which is the reactive power, based on the voltages V1 and V2. The measuring device 1 determines the phase θ of the leakage current with respect to the injected current based on the ratio of the injected active power Ix_Active and the injected reactive power Ix_Reactive. M can be obtained. Note that the phase θ M is the phase of the voltage V t with respect to the measured voltage V M and corresponds to it.

[0056] Also, the phase difference between the voltage V1 of the applied injected current and the voltage V2 of the combined current changes according to the ratio of the resistance component 87 and the capacitance component 88 of the cable sheath 82 (including the insulator part 401). Therefore, the measuring device 1 can calculate the resistance component 87 and the capacitance component 88 of the cable sheath 82 (including the insulator part 401) based on the injected active power Ix_Active and the injected reactive power Ix_Reactive. Furthermore, since the voltage V2 is the voltage corresponding to the combined current, the measuring device 1 compares the waveform of the voltage V2 with the waveform of the voltage V1 (= V t ) to extract only the leakage current I M of the measured voltage V M . The frequency F t of the voltage V t of the injected current and the frequency F M of the measured voltage V M are known. Therefore, the measuring device 1 can calculate the measured voltage V M using this information.

[0057] As described above, theoretically, the measuring device 1 measures the measured voltage V M and the phase θ of the leakage current Mcan be measured. However, in reality, there are influences from measurement environments such as temperature and humidity, as well as capacitance leakage and resistance leakage within the circuit unit 71, and errors may occur in the measured values due to these contributions. Therefore, the measuring device 1 may measure the measurement signal V1 of the measurement terminal 35 and the measurement signal V2 of the measurement terminal 36 in a state where the switch 21 is connected to the resistor 25 side and the switch 22 is open. The measuring device 1 measures the voltage V M The offset active power Iofs_Active, which is the active power of the voltage V2 in a state where the influence of is excluded, and the offset reactive power Iofs_Reactive, which is the reactive power, may be calculated. The measuring device 1 may calculate the active power I_Active (measured active power) obtained by offsetting the offset active power Iofs_Active from the injected active power Ix_Active, and the reactive power I_Reactive (measured reactive power) obtained by offsetting the offset reactive power Iofs_Reactive from the injected reactive power Ix_Reactive. Here, the active power I_Active and the reactive power I_Reactive are obtained by the following equations (1) and (2). I_Active = Ix_Active - Iofs_Active (1) I_Reactive = Ix_Reactive - Iofs_Reactive (2)

[0058] The measuring device 1 uses the active power I_Active and the reactive power I_Reactive calculated as described above to measure the voltage V M and the phase θ of the leakage current M may be calculated. Thereby, Measuring device 1 reduces the influence of measurement environments and internal leakage, etc., and the measured voltage V M and the phase θ of the leakage current M can be acquired.

[0059] Also, as described above, theoretically, by comparing the waveform of the voltage V2 and the waveform of the voltage V1 (= V t ), the leakage current I of the measured voltage V M M ​Only can be obtained. However, actually, there is leakage in the resistor 25 etc., and due to the contribution of such leakage, an error may occur in the measured value. Therefore, the measuring device 1 may connect the switch 21 to the side of the operational amplifier 12 and measure the measurement signal V3 of the operational amplifier 12 in the state where the switch 22 is connected, by the measurement terminal 37. The measuring device 1, based on the voltage V3, the measured voltage V M of the leakage current I M (effective current value: I M ) may be directly measured. The measuring device 1, in addition to the leakage current I M measured in this way, based on the active power I_Active, the reactive power I_Reactive, the leakage current I M of the effective current value I M , the voltage V t of the injection current, the frequency F t , and the frequency F M of the measured voltage V M , may calculate the measured voltage V M . In this way, the measuring device 1 is provided with the measurement terminal 37 for directly measuring the leakage current I M , and the switch 21 for connecting the clip electrode 40 to the measurement terminal 37, so that a more accurate measured voltage V M can be obtained. Note that the relationships between the active power I_Active and the reactive power I_Reactive and the resistance component 87 and the capacitance component 88 of the aforementioned cable covering 82 (including the insulator portion 401) will be described later.

[0060] The specific operation of the measuring device 1 will be described with reference to FIG. 5. FIG. 5 is a diagram for explaining an example of a measurement sequence by the measuring device 1. In FIG. 5, the horizontal axis represents time and the vertical axis represents voltage.

[0061] During the measurement period T1 (for example, a length of 100 ms), the measuring device 1 calculates the offset active power Iofs_Active and the offset reactive power Iofs_Reactive inside the circuit unit 71. Specifically, the measuring device 1 opens the switch 22 and injects an injection current from the injection terminal 31. The measuring device 1 acquires the measurement signal V1 (= the voltage V of the injection current) measured by the measurement terminal 35 t ), and the measurement signal V2 measured by the measurement terminal 36. In FIG. 5, the graph 101 shows the time change of the voltage V1 of the measurement signal V1. The graph 102 shows the time change of the voltage V2 of the measurement signal V2. The measuring device 1 acquires, as the offset active power Iofs_Active, the average value obtained by multiplying the instantaneous value of the voltage V1 by the instantaneous value of the voltage V2. The measuring device 1 calculates, as the offset reactive power Iofs_Reactive, the average value obtained by multiplying the instantaneous value of the voltage V1 shifted by 90 degrees in phase by the instantaneous value of the voltage V2. In other words, the offset active power Iofs_Active and the offset reactive power Iofs_Reactive are the active power and the reactive power in the circuit unit 71 measured by flowing an injection current inside the circuit unit 71 in a state where there is no contribution from the leakage current from the core wire 81 to which the measured voltage V M is applied.

[0062] During the measurement period T2 (for example, a length of 100 ms), the measuring device 1 calculates the injection active power Ix_Active and the injection reactive power Ix_Reactive inside the circuit unit 71. Specifically, the measuring device 1 connects the switch 21 to the resistor 25 side and connects the switch 22 to inject an injection current from the injection terminal 31. The measuring device 1 acquires the measurement signal V1 (= the voltage V of the injection current) measured by the measurement terminal 35 t) and acquire the measurement signal V2 measured by the measurement terminal 36. Also in the measurement period T2 of FIG. 5, the graph 101 shows the time change of the voltage V1 of the measurement signal V1. The graph 103 shows the time change of the voltage V2 of the measurement signal V2. The measuring device 1 acquires, as the injected active power Ix_Active, the average value obtained by multiplying the instantaneous value of the voltage V1 and the instantaneous value of the voltage V2. The measuring device 1 calculates, as the injected reactive power Ix_Reactive, the average value obtained by multiplying the instantaneous value of the voltage V1 shifted by 90 degrees in phase and the instantaneous value of the voltage V2. In other words, the injected active power Ix_Active and Injection disabled the power Ix_Reactive are the active power and reactive power in the circuit unit 71 measured by flowing an injected current in the circuit unit 71 in a state where there is a contribution from the leakage current I M from the core wire 81 to which the voltage V M is applied.

[0063] In the measurement period T3 (for example, with a length of 300 ms), the measuring device 1 measures the leakage current I M of the voltage V M being measured. Specifically, the measuring device 1 connects the switch 21 to the side of the operational amplifier 12 and outputs the leakage current I M of the voltage V M being measured to the operational amplifier 12. The operational amplifier 12 amplifies the leakage current I M and outputs it to the measurement terminal 37. The measuring device 1 acquires the measurement signal V3 measured by the measurement terminal 37, which is the current corresponding to such a leakage current I M . In FIG. 5, the graph 104 shows the time change of the voltage V3 of the measurement signal V3. The measuring device 1 acquires the effective current value I M of the leakage current I M measured in this way. In other words, the measuring device 1 acquires the voltage V3 of the leakage current I M leaking from the core wire 81 through the insulator (cable sheath 82 and insulator portion 401) in a state where there is no contribution from the injected current, and based on the voltage V3, acquires the effective current value of the leakage current I M . M

[0064] The measuring device 1 acquires the measured voltage V M and the phase θ M based on the information acquired during the measurement periods T1 to T3. First, the measuring device 1 calculates the active power I_Active according to Equation (1) based on the injected active power Ix_Active and the offset active power Iofs_Active acquired during the measurement periods T1 and T2. Similarly, the measuring device 1 calculates the reactive power I_Reactive according to Equation (2) based on the injected reactive power Ix_Reactive and the offset reactive power Iofs_Reactive acquired during the measurement periods T1 and T2.

[0065] Based on the active power I_Active and the reactive power I_Reactive, the measuring device 1 determines the phase θ t of the leakage current I M with respect to the voltage V M of the injected current. Specifically, the measuring device 1 may calculate the phase θ M of the leakage current I M according to the following Equation (3). θ M = arctan(I_Reactive / I_Active) (3)

[0066] Based on the active power I_Active, the reactive power I_Reactive, the voltage V t of the injected current and the frequency F t , the frequency F M of the measured voltage V M , as well as the effective current value I M of the leakage current I M , the measuring device 1 acquires the measured voltage V M .

[0067] Here, as shown in Equation (4), a value I_Reactive’ is calculated by multiplying the ratio of the frequency F M of the measured voltage V M to the frequency F t of the voltage V t of the injected current with respect to the reactive power I_Reactive. I_Reactive’ = I_Reactive × (F M / Ft ) (4)

[0068] In this case, the apparent power current I_Apparent is calculated by the following equation (5). I_Apparent = ((I_Active) 2 +(I_Reactive’) 2 ) 1 / 2 / V t (5) Here, (I_Active) 2 +(I_Reactive’) 2 ) 1 / 2 corresponds to the apparent power.

[0069] Therefore, the measuring device 1 calculates the apparent power current I_Apparent by equation (5), and then calculates the voltage V to be measured by equation (6). M V M =I M / I_Apparent×V t (6)

[0070] When the switch 21 is connected to the resistor 25 side, the switch 22 is connected, and an injection current is injected from the injection terminal 31, the currents I R , I C flowing through the resistance component 87 and the capacitance component 88 of the cable sheath 82 (including the insulator portion 401) are represented by equations (7) and (8). I R =I_Active / R x (7) I C =I_Reactive / R x (8)

[0071] Then, the resistance value R I of the resistance component 87 and the capacitance value C I of the capacitance component 88 of the cable sheath 82 (including the insulator portion 401) are represented by equations (9) and (10). R I =V t / I R (9) C​I =V t / I C (10) Therefore, the calculations of formulas (4) to (6) are to calculate the voltage level of the measurement signal V3 by inverse calculation from the resistance component 87 and the capacitance component 88 obtained from the measurement signals V1 and V2, and the voltage V to be measured M corresponds to this calculation.

[0072] The measuring device 1 measures the voltage V to be measured obtained as described above M and the phase θ of the leakage current M and outputs them. For example, the measuring device 1 may display the voltage V M and the phase θ M on the output unit 724, or store them in the storage unit 722.

[0073] As described above, the measuring device 1 injects an injection current into the cable 80 to which the voltage V to be measured is applied, and the injection current and the leakage current I M of the voltage V to be measured leaking from the cable sheath 82 M are superimposed to measure the combined current (V2). The measuring device 1 analyzes the injection current (voltage V1 = V M ) and the combined current (voltage V2) to calculate the active power (measured active power) and the reactive power (measured reactive power) based on the contribution of the voltage V to be measured t . The measuring device 1 obtains the phase θ M of the voltage V to be measured with respect to the voltage V t of the injection current from the ratio of the reactive power and the active power. Further, the measuring device 1 calculates the apparent power M I_Apparent based on the ratio of the reactive power and the active power, the voltage V M to be measured, the frequency F M of the voltage V to be measured, the frequency F M of the voltage V t of the injection current, and the voltage V t of the injection current. The measuring device 1 calculates the leakage current I t , the apparent power current I_Apparent, and the voltage V M of the injection current to calculate the voltage V current to be measured t and the phase θ MCalculate it. Thus, the measuring device 1 measures the measured voltage V M at a frequency F M different from the frequency F t of the injected current into the cable sheath 82. Therefore, the measuring device 1, based on the frequency, while the live wire is in the live state, distinguishes the measured voltage V M from the voltage V t of the injected current, and with a simple configuration, can measure the measured voltage V M and the phase θ M from above the cable sheath 82.

[0074] Also, the measuring device 1 measures the offset active power Iofs_Active and the offset reactive power Iofs_Reactive with the switch 22 turned off, corrects the injected active power Ix_Active and the injected reactive power Ix_Reactive, and then calculates the voltage V M and the phase θ M . The offset active power Iofs_Active and the offset reactive power Iofs_Reactive reflect the power consumed by the capacitance component and the insulation resistance component inside the circuit unit 71. Therefore, the measuring device 1 can measure the measured voltage V M and the phase θ M with higher accuracy by excluding the influence of leakage and environment in the circuit unit 71.

[0075] Also, the measuring device 1 directly measures the leakage current I M of the measured voltage V M by switching the switch 21, and measures the measured voltage V M based on the measured value. Therefore, the measuring device 1 can measure the measured voltage V M and the phase θ M with higher accuracy by excluding the influence of resistance leakage in the circuit unit 71.

[0076] Note that FIG. 5 shows an example in which the offset active power Iofs_Active and the offset reactive power Iofs_Reactive are calculated during the measurement period T1, then the injected active power Ix_Active and the injected reactive power Ix_Reactive are calculated during the measurement period T2, and then the leakage current I M is measured. However, the measurement order is arbitrary and is not limited to that shown in FIG. 5.

[0077] The measuring device 1 described with reference to FIGS. 1 to 5 may be applied, for example, to a device for measuring electrical quantities in a three-wire power transmission circuit.

[0078] FIG. 6 is a diagram showing an example of a device 2 for measuring the live wire insulation resistance to which the measuring device 1 of FIG. 1 is applied. The device 2 is a configuration example in which the measuring device 1 according to the present embodiment is applied to a clamp sensor. A clamp sensor is a device that measures a voltage to be measured based on a measured value of a magnetic field generated in a magnetic core located around a conductor by using electromagnetic induction. The device 2 includes a main body portion 51, a clamp portion 52, insulating clips 41 (41r, 41s, 41t), and wirings 45 (45r, 45s, 45t). The device 2 has the same configuration as the insulating clips 41 and the wirings 45 described with reference to FIGS. 2 and 3 for each of R, S, and T. The main body portion 51 has the same configuration as the device main body 10 described with reference to FIG. 4 for each of R, S, and T. Further, the main body portion 51 has a configuration for measuring the current detected in the clamp portion 52 by electromagnetic induction.

[0079] In FIG. 6, power is supplied from terminals 91 (91r, 91s, 91t) to a load 90 by a three-phase three-wire cable 92 (92r, 92s, 92t). In the example of FIG. 6, the clamp portion 52 is used, for example, to measure the leakage current of a distribution board circuit. The device 2 can measure the voltage to be measured and the phase applied to each cable 92 in a non-contact manner by clipping each cable 92 with the insulating clips 41 (41r, 41s, 41t).

[0080] Device 2 constitutes a live wire insulation resistance measuring Ior measuring instrument with such a configuration of a non-contact voltage probe. That is, the current Io measured by the clamp unit 52 is a combined value of capacitive leakage and resistive leakage. Therefore, device 2 can extract only the resistive leakage by the difference between the phase of the voltage to be measured measured by the insulation clip 41 and the phase of the current Io measured by the clamp unit 52. Further, device 2 can obtain the value of the insulation resistance from the voltage value to be measured measured by the insulation clip 41 and the leakage current of the resistive component of Io measured by the clamp unit 52. Since device 2 can perform these measurements without directly touching the live wire, the operator can work safely in the dangerous switchboard work.

[0081] FIG. 7 is a diagram showing an example of a power meter 3 applying the measuring device 1 of FIG. 1. The power meter 3 includes a main body unit 61, clamp units 62 (62r, 62s, 62t), wirings 65 (65r, 65s, 65t), insulation clips 41 (41r, 41s, 41t), and wirings 45 (45r, 45s, 45t). Comparing the power meter 3 in FIG. 7 with the device 2 in FIG. 6, the difference is that not only the insulation clips 41 and the wirings 45 but also the clamp units 62 and the wirings 65 are provided for each of R, S, and T. According to the power meter 3 as shown in FIG. 7, in a clamp power meter or a direct current measurement type power meter, in addition to measuring the load current, the phase and voltage can be measured non-contact, and the power measurement can be performed. Since the power meter 3 can also perform these measurements non-contact with the live wire, the operator can work safely in the dangerous switchboard work.

[0082] As described above, the measuring device 1 can be applied not only to live wire insulation measurement but also to power meters, voltmeters, etc. For example, it can also be applied to voltage measurement at dangerous locations and devices for safely measuring voltage, such as digital multimeters and voltage detectors, in outdoor high-voltage equipment.

[0083] As described above, the measuring device 1 measures the voltage V to be measured M at a frequency F M different from the frequency F tBy injecting the injection current, the resistance component 87 and the capacitance component 88 of the cable sheath 82 can be specified in the live wire state, distinguishable from the signal to be measured. Further, the measuring device 1 clips the insulating clip 41 from above the cable sheath 82, and based on the signal acquired through the cable sheath 82 and the insulator part 401, the measured voltage V M and the phase θ M can be measured. Therefore, the operator can safely perform maintenance work without clipping the live wire part.

[0084] Also, the measuring device 1 has a simple circuit configuration as shown in FIG. 4. Therefore, the measuring device 1 can be realized with a relatively inexpensive configuration.

[0085] The present disclosure is not limited to the above-described embodiments. For example, a plurality of blocks described in the block diagram may be integrated, or one block may be divided. Other changes are possible without departing from the spirit of the present disclosure.

Explanation of Signs

[0086] 1 Measuring device 10 Device body 11 - 14 Operational amplifier 21, 22 Switch 25 Resistor 31 Injection terminal 35 - 37 Measuring terminal 40 Clip electrode 41 Insulating clip 45 Wiring 47 Gripping structure 51 Body part 52 Clamp part 61 Body part 62 Clamp part 65 Wiring 71 Circuit unit 72 Control unit 80 Cable 81 Core wire 82 Cable sheath 84 Power supply 87 Resistance component 88 Capacity component 90 Load 91 Terminal 101 - 104 Graph 401 Insulator part 402 Electrode 403 Insulator part 404 Shield 405 Insulator part 406 Insulator part 408 Adhesive part 471 Arm part 472 Contact part 473 Gripping part 721 Control unit 722 Memory unit 723 Input unit 724 Output unit

Claims

**Claim 1**: A measuring device comprising a circuit unit and a control unit for controlling the circuit unit, which measures a measured voltage of a first frequency applied to a core wire, wherein: the circuit unit: inject an injection current of a second frequency into the core wire from an electrode in contact with an insulator covering the core wire; while injecting the injection current, obtain the composite current based on the voltage across the terminals of a resistor through which a composite current flows, the composite current being composed of the injection current and a leakage current of the measured voltage leaking from the insulator through the electrode; the control unit: obtain a measured active power, which is the active power based on the contribution of the measured voltage, based on an injection active power, which is an average value obtained by multiplying an instantaneous value of the voltage of the injection current and an instantaneous value of the voltage of the composite current; obtain a measured reactive power, which is the reactive power based on the contribution of the measured voltage, based on an injection reactive power, which is an average value obtained by multiplying an instantaneous value of the voltage of the injection current with its phase shifted by 90 degrees and an instantaneous value of the voltage of the composite current; obtain a current of apparent power based on the measured active power, the measured reactive power multiplied by the ratio of the first frequency to the second frequency, and the voltage of the injection current; obtain the measured voltage based on the current of apparent power, the effective value of the current of the leakage current, and the voltage of the injection current; A measuring device. **Claim 2** The control unit: obtain the phase of the leakage current with respect to the injection current by the arctangent of the ratio of the measured active power and the measured reactive power; The measuring device according to Claim 1. **Claim 3** The circuit unit: obtain an offset active power, which is the active power in the circuit unit measured by flowing the injection current in the circuit unit in a state where the electrode is electrically disconnected, as an average value obtained by multiplying an instantaneous value of the voltage of the injection current and an instantaneous value of the voltage corresponding to the voltage across the terminals of the resistor; obtain an offset reactive power, which is the reactive power in the circuit unit measured by flowing the injection current in the circuit unit in a state where the electrode is electrically disconnected, as an average value obtained by multiplying an instantaneous value of the voltage of the injection current with its phase shifted by 90 degrees and an instantaneous value of the voltage corresponding to the voltage across the terminals of the resistor; The control unit: obtain the measured active power by offsetting the injection active power with the offset active power; Obtaining the measured reactive power as the power obtained by offsetting the injected reactive power with the offset reactive power. The measuring device according to claim 1 or 2.

4. In a state where the injection current is not flowing, the circuit unit obtains the voltage of the leakage current of the measured voltage leaking from the core wire through the insulator. Based on the obtained voltage of the leakage current, the control unit obtains the effective current value of the leakage current. The measuring device according to claim 1 or 2.

5. A measuring method of a measuring device including a circuit unit and a control unit that controls the circuit unit, and measuring a measured voltage of a first frequency applied to a core wire. The circuit unit is Injecting an injection current of a second frequency into the core wire from an electrode in contact with an insulator covering the core wire. While injecting the injection current, obtaining the combined current based on the voltage between the terminals of a resistor through which a combined current composed of the injection current and the leakage current of the measured voltage leaking from the insulator through the electrode flows. The control unit is Obtaining the measured active power, which is the active power based on the contribution of the measured voltage, based on the injection active power, which is the average value obtained by multiplying the instantaneous value of the voltage of the injection current and the instantaneous value of the voltage of the combined current. Obtaining the measured reactive power, which is the reactive power based on the contribution of the measured voltage, based on the injection reactive power, which is the average value obtained by multiplying the instantaneous value of the voltage of the injection current with its phase shifted by 90 degrees and the instantaneous value of the voltage of the combined current. Obtaining the current of the apparent power based on the measured active power, the product of the ratio of the first frequency and the second frequency to the measured reactive power, and the voltage of the injection current. Obtaining the measured voltage based on the current of the apparent power, the effective current value of the leakage current, and the voltage of the injection current. A measuring method including.

6. The control unit is Obtaining the phase of the leakage current with respect to the injection current by the arctangent of the ratio of the measured active power and the measured reactive power. The measuring method according to claim 5.

7. The circuit unit is The offset active power, which is the active power in the circuit unit measured by flowing the injection current in the circuit unit in a state where the electrodes are electrically disconnected, is obtained by an average value obtained by multiplying the instantaneous value of the voltage of the injection current and the instantaneous value of the voltage corresponding to the voltage across the resistor. The offset reactive power, which is the reactive power in the circuit unit measured by flowing the injection current in the circuit unit in a state where the electrodes are electrically disconnected, is obtained by an average value obtained by multiplying the instantaneous value of the voltage of the injection current with its phase shifted by 90 degrees and the instantaneous value of the voltage corresponding to the voltage across the resistor. The control unit: Obtains the measured active power as the power obtained by offsetting the injection active power with the offset active power. Obtains the measured reactive power as the power obtained by offsetting the injection reactive power with the offset reactive power. The measurement method according to claim 5 or 6.

8. In a state where the injection current is not flowing, the circuit unit obtains the voltage of the leakage current of the measured voltage leaking from the core wire through the insulator. The control unit obtains the effective current value of the leakage current based on the obtained voltage of the leakage current. The measurement method according to claim 5 or 6.

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