NON-CONTACT VOLTAGE SENSOR DEVICE AND VOLTAGE MEASURING METHOD THEREIN

Abstract

The non-contact voltage sensor device includes a non-contact voltage sensor (10) that measures the voltage in a power line (100) having a conductor (110) to which power is supplied from a commercial power source (200) and an insulator (120) covering the conductor (110) while being in electrical non-contact with the conductor (110) in the power line (100), a zero-cross point detection unit (32) that receives an output from the non-contact voltage sensor (10) and outputs a calibration mode command signal indicating a calibration mode when it detects zero potential in the output from the non-contact voltage sensor (10), and a calibration signal circuit (20) that outputs a calibration signal to the non-contact voltage sensor (10) when it receives the calibration mode command signal indicating the calibration mode from the zero-cross point detection unit 32.

Description

[Technical field]

[0001] The present disclosure relates to a non-contact voltage sensor device having a non-contact voltage sensor and a voltage measurement method in the non-contact voltage sensor device. [Background technology]

[0002] When measuring the voltage on a power line, a non-contact voltage sensor device is required to avoid and prevent serious accidents such as short circuits and electric shock. Various non-contact voltage sensor devices have been studied, and one example is shown in Patent Document 1. Patent Document 1 discloses a non-contact voltage measuring device that measures an AC voltage in a conductor by utilizing a coupling capacitor (CO) formed between a conductive sensor and the conductor of an insulated electric wire.

[0003] The non-contact voltage measurement device includes a reference voltage source for generating a reference current between the conductive sensor and the conductor, an input amplifier having an inverting terminal electrically coupled to the conductive sensor and a non-inverting terminal electrically coupled to the internal ground guard, and a feedback resistor coupled between the inverting terminal and an output terminal of the input amplifier.

[0004] The input amplifier receives a signal current through the conductor and a reference current through a reference voltage source from the conductive sensor, outputs a sensor current voltage signal at an output terminal, and processes the sensor current voltage signal to determine an AC voltage in the conductor. Also, since the coupling capacitance value of the coupling capacitor (CO) depends on the distance between the sensor and the conductor, a calibration factor is obtained that includes different calibration factors for multiple physical locations on the conductor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-215329 A Summary of the Invention [Problem to be solved by the invention]

[0006] In general, when power is supplied to a power line from a commercial power source, a calibration signal used in a calibration process has a small amplitude relative to the voltage amplitude of the commercial power source. In the non-contact voltage sensor device disclosed in Patent Document 1, the AC voltage of the reference voltage source is also 2.4V while the AC voltage in the conductor is 120V. In this way, if the voltage amplitude of the calibration signal used in the calibration process is small compared to the voltage amplitude to be observed, a problem occurs in that the measurement sensitivity and accuracy of the calibration process deteriorate due to differences in dynamic range.

[0007] The present disclosure has been made in consideration of the above-mentioned points, and has an object to provide a non-contact voltage sensor device that can maintain high accuracy of the calibration process even when using a calibration signal whose voltage amplitude is relatively small compared to the voltage amplitude of the object to be observed. do. [Means for solving the problem]

[0008] The non-contact voltage sensor device according to the present disclosure comprises a non-contact voltage sensor that measures the voltage in a power line having a conductor to which power is supplied from a commercial power source and an insulator covering the conductor, without being in electrical contact with the conductor in the power line, a zero-cross point detection unit that receives output from the non-contact voltage sensor and outputs a calibration mode command signal indicating a calibration mode when it detects zero potential in the output from the non-contact voltage sensor, and a calibration signal circuit that outputs a calibration signal to the non-contact voltage sensor when it receives the calibration mode command signal indicating the calibration mode from the zero-cross point detection unit. The non-contact voltage sensor has a probe electrode that is placed in contact with or in close proximity to a surface of an insulator of a power line, and a sensor unit, and the sensor unit has an inverting input terminal electrically connected to the probe electrode, a non-inverting input terminal that is set to zero potential in an operation mode and to which a calibration signal is input from an output terminal of a calibration signal circuit in a calibration mode, and one output terminal, and has an amplifier element with a negative feedback circuit connected between the output terminal and the inverting input terminal, and an analog / digital converter that is connected to the output terminal of the amplifier element and converts an analog voltage from the amplifier element into digital data and outputs the digital data to the zero-crossing point detection unit. . Effect of the Invention

[0009] According to the present disclosure, serious accidents such as short circuits and electric shocks can be avoided or prevented when measuring the voltage on a power line, and the accuracy of the calibration process can be maintained at a high level. [Brief description of the drawings]

[0010] [Figure 1]1 is a block diagram showing an example of the configuration of a non-contact voltage sensor device according to a first embodiment. [Diagram 2] 10 is a waveform diagram showing an outline of a voltage waveform (superimposed waveform) in an output from a non-contact voltage sensor in a calibration mode in the non-contact voltage sensor device according to the first and second embodiments. FIG. [Diagram 3] 5 is a flowchart showing a calibration method in the non-contact voltage sensor device according to the first embodiment. [Figure 4] FIG. 11 is a waveform diagram showing an outline of a voltage waveform (superimposed waveform) in an output from a non-contact voltage sensor in a calibration mode in a non-contact voltage sensor device according to Embodiment 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Embodiment 1 The non-contact voltage sensor device according to the first embodiment will be described with reference to FIGS. 1 to 3. FIG. The non-contact voltage sensor device of embodiment 1 is a non-contact voltage sensor device that measures the voltage in a power line to which power is supplied from a commercial power source (50 Hz or 60 Hz, 100 V or 200 V) when measuring the power consumption (active power) of the commercial power source in a power distribution system of a building or factory building, for example.

[0012] The non-contact voltage sensor device according to the first embodiment performs a calibration process when it detects a zero potential in the voltage on the power line. The non-contact voltage sensor device according to the first embodiment includes a non-contact voltage sensor 10 , a calibration signal circuit 20 and a control circuit 30 .

[0013] The non-contact voltage sensor 10 measures the voltage of power (voltage value Vin of the observation signal) from a commercial power source 200 supplied to a power line 100 consisting of a cable having a conductor (cable core) 110 and an insulator 120 covering the conductor 110, without being in electrical contact with the conductor 110 in the power line 100. In the non-contact voltage sensor 10, power is applied to a conductor 110 from a commercial power source 200, and the non-contact voltage sensor 10 measures a voltage value Vin (voltage amplitude) in the conductor 110.

[0014] The non-contact voltage sensor 10 has a probe electrode 11 , a sensor portion 12 and a probe cable 13 . The non-contact voltage sensor 10 measures the voltage value (voltage amplitude) in the conductor 110 by utilizing a minute coupling capacitance 310 that occurs between the probe electrode 11 and the conductor 110 in the power line 100 .

[0015] An insulation resistance 320 , which is the DC resistance of the insulator 120 , exists between the probe electrode 11 and the conductor 110 . A parallel body in which the coupling capacitance 310 and the insulation resistance 320 are connected in parallel is defined as a first impedance element 300 .

[0016] The probe electrode 11 is disposed in contact with or in close proximity to the surface of the insulator 120 so as to surround the insulator 120 of the power line 100 . As a result, the probe electrode 11 is disposed close to the conductor 110 in the power line 100 , and a coupling capacitance 310 is generated between the probe electrode 11 and the conductor 110 in the power line 100 .

[0017] The probe electrode 11 detects the voltage waveform on the conductor 110 via the coupling capacitance 310 without contacting the conductor 110 . The coupling capacitance 310 generated between the probe electrode 11 and the conductor 110 in the power line 100 varies in capacitance depending on the amount of coupling between the probe electrode 11 and the power line 100 .

[0018] Since the absolute value of the voltage amplitude in the conductor 110 using the coupling capacitance 310 depends on the coupling capacitance 310, whose capacitance value is unknown, in embodiment 1, a calibration process is performed on the voltage value (voltage amplitude) in the conductor 110 measured using the calibration signal circuit 20, and the coupling capacitance 310 is calculated.

[0019] The sensor unit 12 converts the voltage waveform detected by the probe electrode 11 into digital voltage data. The sensor unit 12 includes an amplifier element 12a, a negative feedback circuit 12b, and an analog / digital (AD) converter 12c.

[0020] The amplifying element 12a has a non-inverting input terminal (+), an inverting input terminal (-) and one output terminal, and a negative feedback circuit 12b is connected between the output terminal and the inverting input terminal. The amplifying element 12a and the negative feedback circuit 12b constitute an operational amplifier. An analog voltage output from the output terminal of the amplifying element 12a is converted by an AD converter 12c into digital data and output.

[0021] The inverting input terminal of the amplifying element 12a is electrically connected to the probe electrode 11 via the probe cable 13, and the voltage value (voltage amplitude) in the conductor 110 measured by the probe electrode 11 is input to the inverting input terminal. The non-inverting input terminal of the amplifying element 12a is set to zero potential in the operational mode.

[0022] In the calibration mode, a calibration signal is input from a calibration signal circuit 20 to the non-inverting input terminal of the amplifying element 12a. The operation mode is a normal operation mode in which the voltage waveform on the conductor 110 is measured. The calibration mode is a mode for identifying the coupling capacitance 310 whose capacitance value C1 is unknown (unknown quantity).

[0023] Negative feedback circuit 12b is a parallel combination of capacitor 12b1 and resistor 12b2, and serves as a second impedance element. Capacitor 12b1 in negative feedback circuit 12b is a variable capacitor whose capacitance is variable, and upon receiving a gain change command signal, its capacitance in the calibration mode is set to a value smaller than its capacitance in the operation mode.

[0024] In the first embodiment, the capacitance value in the calibration mode is set to 1 / 100 of the capacitance value in the operation mode. The variable capacitor may be, for example, one that switches the connections of a plurality of capacitor elements using a switch element.

[0025] The second impedance element, which is the negative feedback circuit 12b, and the first impedance element 300 are in a corresponding relationship, the capacitor 12b1 in the negative feedback circuit 12b and the coupling capacitance 310 in the first impedance element 300 are in a corresponding relationship, and the resistor 12b2 in the negative feedback circuit 12b and the insulation resistor 320 in the first impedance element 300 are in a corresponding relationship.

[0026] In the operation mode, the non-inverting input terminal of the amplifying element 12a is at zero potential, that is, the potential of the output terminal of the calibration signal circuit 20 is set to the ground potential (virtual GND). Therefore, in the operation mode, the amplifying element 12a operates in an inverting amplification type circuit configuration, and the output voltage value Vout0 of the amplifying element 12a, that is, the voltage amplitude, is expressed by the following equation (1).

[0027] TIFF0007646103000001.tif13166

[0028] In the above formula (1), Vin is a voltage value on the power line 100 when power is supplied from the commercial power source 200 to the power line 100, Z1 is an impedance of the first impedance element 300, C1 is a capacitance value of the coupling capacitance 310, and Z 20 is the impedance of the negative feedback circuit (second impedance element) 12b in the operational mode, C 20 is the capacitance value of the capacitor 12b1 in the negative feedback circuit 12b in the operation mode.

[0029] In the operation mode, the impedance Z of the negative feedback circuit (second impedance element) 12b 20 Since the impedance Z1 (=1 / (jωC1)) of the first impedance element 300 is an unknown quantity, this is set approximately to 1 / 100 of the impedance Z1. That is, the output gain G0 of the amplifying element 12a is Z 20 / Z1 is set to 1 / 100, or about 0.01.

[0030] Therefore, in the operational mode, the amplifier element 12a has an output gain G0=-Z 20 It functions as an inverting amplifier circuit with a factor of / Z1 (≒0.01). In the frequency range of the commercial power supply 200, the contribution of the resistance component becomes small, so Z 20 / Z1≒C1 / C 20 The following relationship can be assumed.

[0031] The capacitance value C of the capacitor 12b1 in the negative feedback circuit 12b in the calibration mode 21 The capacitance value C in the operational mode 20 Since the output gain G1 of the amplifying element 12a in the calibration mode is set to a smaller value than the output gain G0 of the amplifying element 12a in the operation mode, the output gain G1 of the amplifying element 12a in the calibration mode is greater than the output gain G0 of the amplifying element 12a in the operation mode.

[0032] In the first embodiment, in the calibration mode, the capacitance value C 21 The capacitance value C 20 Since the output gain G1 is set to 1 / 100 of the original value, the output gain G1 becomes approximately 1 according to the following equation (2). That is, the output gain G1 of the amplifying element 12a in the calibration mode is approximately 100 times the output gain G0 of the amplifying element 12a in the operation mode.

[0033] G1=-Z 21 / Z1≒C1 / C 21 =C1 / (C 20 × 1 / 100) = (C1 / C 20 )×100=1 (2) In the above formula (2), Z 21 is the impedance of the negative feedback circuit 12b in the calibration mode, C 21 is the capacitance value of the capacitor 12b1 in the negative feedback circuit 12b in the calibration mode.

[0034] In the operation mode, the output terminal of the calibration signal circuit 20 is set to ground potential, the non-inverting input terminal of the amplifying element 12a is set to zero potential, and in the calibration mode upon receiving a calibration mode command signal Enable indicating the calibration mode, the calibration signal circuit 20 outputs a calibration signal (voltage value Vref) from the output terminal to the non-inverting input terminal of the amplifying element 12a.

[0035] The AC voltage of the calibration signal is in an orthogonal relationship with the AC voltage from the commercial power supply 200 . The voltage value Vref of the calibration signal is a minute voltage having a different dynamic range from the voltage (100V or 200V) of the commercial power supply 200, and in the first embodiment, is, for example, 1.0V or more and 2.4V or less. Furthermore, the frequency fref of the calibration signal is higher than the frequency fin of the commercial power supply 200, and in the first embodiment, is an integer multiple n (n is a natural number of 2 or more) of the frequency fin of the commercial power supply 200, that is, fref=n×fin.

[0036] Before explaining the calibration mode, when no power is supplied to the conductor 110 from the commercial power source 200 and a calibration signal (voltage value Vref) is input from the calibration signal circuit 20 to the non-inverting input terminal of the amplification element 12a, the output voltage value Vout1 of the amplification element 12a is expressed by the following equation (3).

[0037] TIFF0007646103000002.tif14166

[0038] When no power is supplied from the commercial power source 200, the amplifier element 12a outputs a signal for calibration with a gain G2=1+Z 21 Functions as a non-inverting amplifier circuit for / Z1. In the frequency domain of the calibration signal, the contribution of the resistance component is small, so Z 21 / Z1≒C1 / C 21 A relationship of (≒1) can be assumed. Therefore, the output gain G2 is greater than the output gain G0 of the amplifying element 12a in the operation mode.

[0039] In the above formula (3), the voltage value Vref of the calibration signal and the capacitance value C of the capacitor 12b1 in the negative feedback circuit 12b 21 is known, the capacitance value C1 of the coupling capacitance 310 can be calculated by obtaining the output voltage value Vout1 of the amplifying element 12a. In the above formula (3), Z 21The term / Z1 corresponds to the output gain in operational mode, Z 20 Since this is significantly larger than Z / Z1, Z 21 The relative contribution of the term / Z1 becomes large, and the capacitance value C1 of the coupling capacitance 310 can be calculated with high accuracy, that is, a highly accurate calibration process can be performed.

[0040] In the first embodiment, when power is supplied from commercial power source 200 to power line 100, calibration processing is performed when a zero potential is detected in the voltage value in conductor 110 detected by probe electrode 11, so that output voltage value Vout2 of amplifying element 12a is expressed by the following equation (4).

[0041] TIFF0007646103000003.tif14166

[0042] The above formula (4) represents the output voltage value Vout2 of the amplifying element 12a as a superimposed signal obtained by adding the voltage value Vin at the conductor 110 detected by the probe electrode 11 and the voltage value Vref of the calibration signal by the amplifying element 12a. The capacitance value C1 of the coupling capacitance 310 is calculated from the output voltage value Vout2, because the AC voltage of the calibration signal is orthogonal to the AC voltage from the commercial power supply 200. Therefore, the output voltage value for the voltage value Vref of the calibration signal is extracted from the superimposed signal by processing the output voltage of the amplifying element 12a such as by Fourier transform.

[0043] The output voltage value for the extracted voltage value Vref of the calibration signal corresponds to the output voltage value Vout1 shown by the above equation (3). Therefore, the voltage value Vref of the calibration signal and the capacitance value C of the capacitor 12b1 in the negative feedback circuit 12b 21 is known, the capacitance value C1 of the coupling capacitor 310 can be calculated from the output voltage value for the extracted voltage value Vref of the calibration signal.

[0044] The calibration process is performed when a zero potential is detected in the voltage value at conductor 110 detected by probe electrode 11. Therefore, even if the output gain G1 of amplifier element 12a is increased to improve the extraction of the calibration signal and the measurement accuracy, the voltage value measured by probe electrode 11 corresponding to the voltage value Vin at conductor 110 in the power line 100 and the voltage value Vref of the calibration signal are at the same level, and the voltage value Vref of the calibration signal can be extracted with high accuracy from the output voltage value Vout2 without causing waveform distortion in the output voltage value Vout2 of amplifier element 12a.

[0045] The calibration signal circuit 20 has a calibration signal source 21 and a calibration signal selection element 22 . Calibration signal source 21 is an AC voltage source that outputs a calibration signal consisting of a sine wave whose frequency fref is higher than the frequency fin of commercial power supply 200, for example, fref=n×fin (n is a natural number equal to or greater than 2), and whose voltage value Vref is a minute voltage value Vref, for example, 1 V, having a different dynamic range from the voltage value Vin of commercial power supply 200.

[0046] The calibration signal selection element 22 is an element for switching between the operation mode and the calibration mode. The calibration signal selection element 22 receives the calibration mode command signal Enable, and if the calibration mode command signal Enable does not indicate the calibration mode, i.e., the operational mode, sets the output terminal of the calibration signal circuit 20 to ground potential and sets the non-inverting input terminal of the amplifying element 12a to zero potential.

[0047] When the calibration mode command signal Enable indicates the calibration mode, i.e., when the calibration mode is selected, the calibration signal selection element 22 outputs the calibration signal from the calibration signal source 21 to the output terminal of the calibration signal circuit 20 and provides the calibration signal from the calibration signal source 21 to the non-inverting input terminal of the amplification element 12a. The calibration mode command signal Enable is an H level signal when the calibration mode is indicated, and is an L level signal when the calibration mode is not indicated.

[0048] The control circuit 30 has a voltage measurement function that calculates a calibrated voltage value for the voltage value Vin (voltage amplitude) of the commercial power source 200 applied to the conductor 110 in the power line 100 from the non-contact voltage sensor 10, a calibration mode selection function that outputs a calibration mode command signal Enable to the non-contact voltage sensor 10, and a gain change function that outputs a gain change command signal to change the output gain of the non-contact voltage sensor 10.

[0049] The control circuit 30 includes a measurement processing section 31 , a zero-cross point detection section 32 , and a gain control section 33 . The measurement processing unit 31 receives voltage waveform data from the AD converter 12c of the sensor unit 12 in the non-contact voltage sensor 10, and calculates a calibrated voltage value for the voltage value Vin of the commercial power source 200 supplied to the conductor 110 by using the input voltage waveform data and the capacitance value C1 of the coupling capacitance 310 calculated in the calibration mode.

[0050] That is, the calibrated voltage value is the voltage value Vout0 from the AD converter 12c, the capacitance value C1 of the coupling capacitance 310 calculated in the calibration mode, and the capacitance value C 20 By using the above, Vin is calculated using the relational expression (1) above, that is, the voltage value on the power line 100 when power is supplied from the commercial power source 200 to the power line 100.

[0051] The calculation of the calibrated voltage value is performed multiple times per cycle of the commercial power supply 200. The average of the calibrated voltage values ​​obtained by performing the test multiple times is calculated, and the calculated average is set as the effective voltage value. The calibrated voltage value is stored in a memory unit (not shown).

[0052] In the calibration mode, the measurement processing unit 31 extracts the voltage value Vout1 from the voltage value Vout2 from the AD converter 12c by processing such as Fourier transform, and calculates the voltage value Vout1, the voltage value Vref of the calibration signal, and the capacitance value C of the capacitor 12b1 in the negative feedback circuit 12b in the calibration mode. 21By using the above formula, (3) The capacitance value C1 of the coupling capacitance 310 is calculated using the following relational expression.

[0053] The zero-cross point detector 32 receives the output from the non-contact voltage sensor 10, and outputs a calibration mode command signal when it detects a zero potential in the output from the non-contact voltage sensor 10. The zero-crossing point detection unit 32 monitors the time when the calibrated voltage values ​​calculated by the measurement processing unit 31 and stored in the memory unit in chronological order reach zero potential, that is, the time when the amplitude of the voltage data indicated by the calibrated voltage values ​​reaches a zero-crossing point, and outputs a calibration mode command signal.

[0054] When commercial power supply 200 is 50 Hz, the zero crossing points occur at a cycle of 20 ms, and when commercial power supply 200 is 60 Hz, the zero crossing points occur at a cycle of 16.67 ms. In the first embodiment, when zero-cross point detection unit 32 detects a zero potential in the output from non-contact voltage sensor 10, that is, a zero-cross point in commercial power supply 200, it outputs a calibration mode command signal Enable indicating the calibration mode to calibration signal circuit 20 for a fixed period Ten centered on the zero-cross point, in synchronization with the zero-cross points that occur periodically in commercial power supply 200, as shown in FIGS. 1 and 2 .

[0055] The detection of zero-cross points by zero-cross point detection unit 32 is performed by taking advantage of the fact that zero-cross points appear periodically in commercial power supply 200. After detecting zero potential in the output from non-contact voltage sensor 10, the zero-potential calibration mode period Ten is set to Ten / 2 hours before and after the period of the zero-cross points, in accordance with the period of the zero-cross points in commercial power supply 200.

[0056] The zero-crossing point detection unit 32 outputs to the calibration signal circuit 20 a mode command signal Enable that indicates a calibration signal that sets the start time of the calibration mode to Ten / 2 hours before the zero-crossing point at the detection time of the zero potential and the end time of the calibration mode to Ten / 2 hours after the zero-crossing point at the detection time of the zero potential. As a result, the calibration signal output from calibration signal circuit 20, which has received mode command signal Enable indicating the calibration mode, to non-contact voltage sensor 10 has a waveform that is symmetrical (even function) with respect to the zero crossing points in commercial power supply 200.

[0057] The mode command signal Enable indicating the calibration mode rises from L level to H level at the start time of the calibration mode, falls from H level to L level at the end time of the calibration mode, and remains at H level during the calibration mode period Ten to indicate the calibration mode.

[0058] In addition, the detection of the zero-crossing point by the zero-crossing point detection unit 32 may be performed by comparing the output from the non-contact voltage sensor 10 with a threshold value, for example 1 V, and the zero potential calibration mode period Ten may be the time from when the output from the non-contact voltage sensor 10 falls below the threshold value to when the output from the non-contact voltage sensor 10 rises above the threshold value.

[0059] In this case, the zero-cross point detection unit 32 outputs a mode command signal Enable to the calibration signal circuit 20, which indicates a calibration signal that sets the start time of the calibration mode when the output from the non-contact voltage sensor 10 falls below a threshold value, and sets the end time of the calibration mode when the output from the non-contact voltage sensor 10 rises above the threshold value.

[0060] The zero-cross point detector 32 may detect the zero potential every time a zero-cross point appears in the commercial power source 200, but may also detect the zero potential at regular time intervals, such as one second or one minute.

[0061] The gain control unit 33 receives a mode command signal Enable indicating the calibration mode from the zero-cross point detection unit 32, and in order to increase the output gain of the amplifying element 12a in the sensor unit 12 of the non-contact voltage sensor 10 in the calibration mode relative to the output gain in the operation mode, the gain control unit 33 sets the capacitance value C 21 The capacitance value C in the operational mode 20A gain change command signal for changing the gain to a smaller value is output to the negative feedback circuit 12b.

[0062] The gain change command signal changes the capacitance value of the capacitor 12b1 to C when the calibration mode starts in the mode command signal Enable, that is, when the signal rises from the L level to the H level. 20 From C 21 The switching signal changes the capacitance value of the capacitor 12b1 to C when the calibration mode ends in the mode command signal Enable, that is, when the signal falls from H level to L level. 21 From C 20 This is a switching signal to change to.

[0063] That is, the gain change command signal changes the capacitance value of the capacitor 12b1 to C during the calibration mode period Ten when the mode command signal Enable indicates the calibration mode. 21 During the operation mode, the capacitance value of the capacitor 12b1 is maintained at C 20 This is a command signal to maintain the

[0064] Therefore, during the period when the calibration signal is supplied from the calibration signal circuit 20 to the non-inverting input terminal of the amplifying element 12a in response to the mode command signal Enable from the zero-crossing point detector 32, the gain controller 33 sets the capacitance value of the capacitor 12b1 to C 21 The gain change command signal is applied to the negative feedback circuit 12b to change the gain.

[0065] As a result, in the calibration mode, the calibration signal can be amplified with the output gain of the amplifying element 12a being greater than the output gain in the operation mode, so that highly accurate calibration can be performed. The hardware configuration of the measurement processing section 31, the zero cross point detection section 32 and the gain control section 33 that constitute the control circuit 30 is a microcomputer or the like.

[0066] Next, a method for measuring the voltage on power line 100 supplied with power from a commercial power source by using the non-contact voltage sensor device according to the first embodiment will be described with reference to FIG. In step ST1, the non-contact voltage sensor 10 detects a voltage value (voltage waveform) Vin in a conductor 110 of a power line 100 to which power is supplied from a commercial power source, with the probe electrode 11 detecting the voltage value (voltage waveform) Vin via coupling capacitance 310 while being in no electrical contact with the conductor 110.

[0067] In step ST2, the zero-cross point detection unit 32 detects a zero potential in the output obtained by amplifying the voltage waveform detected by the probe electrode 11 by the sensor unit 12, and outputs a calibration mode command signal indicative of the calibration mode. Step ST2 is a calibration mode command step. In step ST3, when the calibration mode command signal indicating the calibration mode output from the zero-cross point detection unit 32 in step ST2 is received by the calibration signal circuit 20, the calibration signal circuit 20 outputs a calibration signal to the non-contact voltage sensor 10. Step ST3 is a calibration signal output step.

[0068] In step ST4, when the calibration mode command signal indicates the calibration mode, the gain control unit 33 changes the capacitance C 21 The capacitance value C in the operational mode 20 A gain change command signal is output to set the capacitance value to a smaller value. Step ST4 is a capacitance value change command step. In step ST5, in the calibration mode, the measurement processing unit 31 calculates the capacitance value C1 of the coupling capacitance 310. Step ST5 is a capacitance value calculation step.

[0069] In step ST6, in the operation mode, measurement processing unit 31 calculates voltage Vin in power line 100 using the output from non-contact voltage sensor 10 and capacitance value C1 of coupling capacitance 310 calculated in step ST5 (capacitance value calculation step). Step ST6 is a voltage measurement step.

[0070] The non-contact voltage sensor device of embodiment 1 includes a zero-cross point detection unit 32 that outputs a calibration mode command signal indicating a calibration mode when it detects a zero potential in the output from non-contact voltage sensor 10, and a calibration signal circuit 20 that outputs a calibration signal to non-contact voltage sensor 10 when it receives a calibration mode command signal indicating the calibration mode from zero-cross point detection unit 32.Therefore, it is possible to maintain high accuracy of the calibration process while using non-contact voltage sensor 10 that can avoid and prevent serious accidents such as short circuits and electric shock when measuring the voltage on power line 100.

[0071] Furthermore, by using a minute voltage having a different dynamic range from the voltage of commercial power source 200 as the calibration signal from calibration signal circuit 20, the capacitance value of variable capacitor 12b1 of negative feedback circuit 12b in non-contact voltage sensor 10 in the calibration mode is set to a value smaller than the capacitance value in the operational mode so that the output gain of amplifying element 12a in non-contact voltage sensor 10 in the calibration mode is higher than the output gain in the operational mode, so that highly accurate calibration processing can be achieved without causing waveform distortion in the output from non-contact voltage sensor 10.

[0072] Embodiment 2 The non-contact voltage sensor device of embodiment 2 differs from the non-contact voltage sensor device of embodiment 1 in that the calibration mode period Ten is specified to be a time that is an integer multiple m (a natural number greater than or equal to 2) of the wavelength λ of the calibration signal output from calibration signal source 21, that is, Ten = m × λ = m / fref, but is otherwise the same.

[0073] Since the components in the non-contact voltage sensor device of embodiment 2 are substantially the same as the components in the non-contact voltage sensor device of embodiment 1 shown in Figure 1, we will refer to Figures 1 and 3 and mainly use Figure 2 to explain the calibration signal output from calibration signal source 21.

[0074] As described in the first embodiment, the calibration signal output from calibration signal source 21 has a frequency fref higher than the frequency fin of commercial power supply 200, for example, fref=n×fin (n is a natural number equal to or greater than 2), and is a sine wave whose voltage value Vref is a minute voltage value Vref, for example, 1 V, having a different dynamic range from the voltage value Vin from commercial power supply 200.

[0075] Furthermore, the voltage waveform of the calibration signal output from calibration signal source 21 is in an orthogonal relationship with the voltage from commercial power supply 200, as described in the first embodiment. Furthermore, in the second embodiment, the calibration mode period Ten of the calibration signal output from calibration signal source 21 is set to a time that is an integer multiple m (a natural number of 2 or more) of the wavelength λ of the calibration signal, centered on the zero-crossing point in commercial power supply 200, in response to a mode command signal Enable indicating the calibration mode from zero-crossing point detection unit 32, as shown in FIG. 2, i.e., Ten=m×λ=m / fref.

[0076] The non-contact voltage sensor device of embodiment 2 has the same effect as the non-contact voltage sensor device of embodiment 1, and in the calibration mode, the measurement processing unit 31 can accurately perform the process of extracting the output voltage value Vout1 corresponding to the voltage value Vref of the calibration signal from the voltage value Vout2 from the AD converter 12c by Fourier transform.

[0077] Embodiment 3 The non-contact voltage sensor device of embodiment 3 differs from the non-contact voltage sensor device of embodiment 1 in that the waveform of the calibration signal output from calibration signal circuit 20 to non-contact voltage sensor 10 is symmetrical with respect to the zero crossing points in commercial power source 200, and is specified as an even function waveform centered on the zero crossing points, but is otherwise the same.

[0078] Since the components in the non-contact voltage sensor device of embodiment 3 are substantially the same as the components in the non-contact voltage sensor device of embodiment 1 shown in Figure 1, we will use Figures 1 and 3 and mainly explain the calibration signal output from the calibration signal circuit 20 to the non-contact voltage sensor 10 using Figure 4.

[0079] As described in the first embodiment, the calibration signal output from calibration signal source 21 has a frequency fref higher than the frequency fin of commercial power supply 200, for example, fref=n×fin (n is a natural number equal to or greater than 2), and is a sine wave whose voltage value Vref is a minute voltage value Vref, for example, 1 V, having a different dynamic range from the voltage value Vin from commercial power supply 200.

[0080] In the third embodiment, when calibration signal circuit 20 receives mode command signal Enable indicating the calibration mode from zero-cross point detection unit 32, as shown in FIG. 4, the calibration signal output from calibration signal source 21 is adjusted in calibration signal circuit 20, and calibration signal circuit 20 outputs to non-contact voltage sensor 10 a calibration signal whose voltage waveform is symmetrical with respect to the zero-cross points in commercial power supply 200 and has an even function waveform centered on the zero-cross points.

[0081] That is, as shown in FIG. 4, during a calibration mode period from -t1 to +t1 centered on a zero crossing point in commercial power supply 200 due to mode command signal Enable indicating the calibration mode from zero crossing point detection unit 32, calibration signal circuit 20 outputs to non-contact voltage sensor 10 a voltage waveform of a calibration signal output from calibration signal source 21 that has a maximum amplitude at the zero crossing point in commercial power supply 200 and is an even function waveform that is symmetrical on the left and right with respect to the time axis.

[0082] As shown in FIG. 4, the voltage waveform detected by probe electrode 11 corresponds to the voltage waveform on power line 100 when power is supplied from commercial power source 200 to power line 100, and is an odd function waveform since it is synchronized with the zero crossing points on commercial power source 200.

[0083] In the non-contact voltage sensor device according to the third embodiment, the measurement processing unit 31 extracts the output voltage value Vout1 for the voltage value Vref of the calibration signal from the voltage value Vout2 from the AD converter 12c as follows. That is, during the calibration mode period from -t1 to +t1, the measurement processing unit 31 calculates the average of data at times symmetrical with respect to the time t=0 which is the zero-cross point of the commercial power supply 200, that is, the voltage value Vout2, from the AD converter 12c.

[0084] By averaging the voltage values ​​Vout2 at times that are symmetrical with respect to the time t=0, the calibration signal has a waveform that is an even function with respect to t=0, so the output voltage value for the voltage value Vref of the calibration signal is averaged. On the other hand, since the voltage waveform detected by probe electrode 11 is an odd function with respect to t=0, the voltage values ​​detected by probe electrode 11 at times symmetrical with respect to time t=0 are cancelled out.

[0085] That is, by averaging the voltage values ​​Vout2 at times symmetrical with respect to the time t=0, it is possible to extract the output voltage value Vout1 for the voltage value Vref of the calibration signal. In short, the non-contact voltage sensor device according to the third embodiment can extract the output voltage value Vout1 for the voltage value Vref of the calibration signal by a simple process called weighted averaging, rather than using a Fourier transform, in the calibration mode.

[0086] The non-contact voltage sensor device of embodiment 3 has the same effect as the non-contact voltage sensor device of embodiment 1, and in calibration mode, the measurement processing unit 31 can extract the output voltage value Vout1 for the voltage value Vref of the calibration signal from the voltage value Vout2 from the AD converter 12c with high accuracy by a simple processing method called averaging.

[0087] It should be noted that the embodiments may be freely combined, any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted. [Industrial Applicability]

[0088] The non-contact voltage sensor device according to the present disclosure is suitable as a non-contact voltage sensor device in a power distribution system such as a building or factory building that measures the voltage of a power line to which power is supplied from a commercial power source in the power distribution system without contacting the power line conductor. [Explanation of symbols]

[0089] 10 non-contact voltage sensor, 11 probe electrode, 12 sensor unit, 12a amplifying element, 12b negative feedback circuit, 12b1 capacitor, 12b2 resistor, 12c AD converter, 20 calibration signal circuit, 21 calibration signal source, 22 calibration signal selection element, 30 control circuit, 31 measurement processing unit, 32 zero cross point detection unit, 33 gain control unit, 100 power line, 110 conductor, 120 insulator, 200 commercial power supply, 310 coupling capacitance.

Claims

1. A non-contact voltage sensor measures the voltage in a power line having a conductor supplied with power from a commercial power source and an insulator covering the conductor, in a state where it is not electrically in contact with the conductor in the power line. A zero-crossing point detection unit receives the output from the non-contact voltage sensor and, upon detecting a zero potential in the output from the non-contact voltage sensor, outputs a calibration mode command signal indicating a calibration mode. A calibration signal circuit that, upon receiving a calibration mode command signal indicating the calibration mode from the zero-crossing point detection unit, outputs a calibration signal to the non-contact type voltage sensor, A non-contact voltage sensor device equipped with the following features.

2. The non-contact voltage sensor has a probe electrode and a sensor portion that are in contact with or close to the surface of the insulator of the power line. The sensor unit includes an inverting input terminal electrically connected to the probe electrode, a non-inverting input terminal which is set to zero potential in operation mode and to which a calibration signal is input from the output terminal of the calibration signal circuit in calibration mode, and an amplification element having one output terminal, with a negative feedback circuit connected between the output terminal and the inverting input terminal, and an analog-to-digital converter connected to the output terminal of the amplification element which converts the analog voltage from the amplification element into digital data and outputs it to the zero-crossing point detection unit. The non-contact voltage sensor device according to claim 1.

3. The aforementioned negative feedback circuit is a parallel configuration of a capacitor and a resistor. The capacitor in the negative feedback circuit is a variable capacitor whose capacitance value in calibration mode is smaller than its capacitance value in operation mode. The non-contact voltage sensor device according to claim 2.

4. The non-contact voltage sensor device according to any one of claims 1 to 3, wherein the frequency of the calibration signal is an integer multiple n (where n is a natural number of 2 or more) of the frequency of the commercial power supply.

5. A non-contact voltage sensor device according to any one of claims 1 to 3, wherein the calibration signal output from the calibration signal circuit to the non-contact voltage sensor receives a calibration mode command signal indicating a calibration mode from the zero-crossing point detection unit, and the calibration signal has a waveform symmetrical with respect to the zero-crossing point in the commercial power supply.

6. The non-contact voltage sensor device according to claim 4, wherein the calibration signal output from the calibration signal circuit to the non-contact voltage sensor, upon receiving a calibration mode command signal indicating a calibration mode from the zero-crossing point detection unit, has a waveform symmetrical with respect to the zero-crossing point in the commercial power supply.

7. A non-contact voltage sensor device according to any one of claims 1 to 3, wherein the calibration signal output from the calibration signal circuit to the non-contact voltage sensor, which receives a calibration mode command signal indicating a calibration mode from the zero-crossing point detection unit, is symmetrical with respect to the zero-crossing point in the commercial power supply and has an even function waveform centered on the zero-crossing point.

8. The non-contact voltage sensor device according to claim 4, wherein the calibration signal output from the calibration signal circuit to the non-contact voltage sensor, upon receiving a calibration mode command signal indicating a calibration mode from the zero-crossing point detection unit, is symmetrical with respect to the zero-crossing point in the commercial power supply and has an even function waveform centered on the zero-crossing point.

9. A method for measuring the voltage in a power line in an electrically non-contact manner with the conductor in the power line, comprising: a probe electrode positioned in contact with or near the surface of an insulator of a power line having a conductor supplied with power from a commercial power source and an insulator covering the conductor; and an amplification element connected to a negative feedback circuit which is a parallel configuration of a variable capacitor and a resistor, to which the voltage waveform measured by the probe electrode is input, wherein the voltage in the power line is measured in an electrically non-contact manner with the conductor in the power line by utilizing the coupling capacitance generated between the probe electrode and the conductor in the power line, A calibration mode command step in which the zero-crossing point detection unit detects a zero potential in the output from the non-contact voltage sensor and outputs a calibration mode command signal indicating a calibration mode, The calibration signal circuit, upon receiving a calibration mode command signal indicating a calibration mode, outputs a calibration signal to the non-contact type voltage sensor in a calibration signal output step, A gain control unit, when the calibration mode command signal indicates calibration mode, outputs a gain change command signal to set the capacitance value of the variable capacitor to a value smaller than the capacitance value in operation mode, in a capacitance value change command step. The measurement processing unit performs a capacity value calculation step in calibration mode to calculate the capacity value of the combined capacity, The measurement processing unit performs a voltage measurement step in which, in the operating mode, calculates the voltage in the power line using the output from the non-contact voltage sensor and the capacitance value of the coupled capacitance calculated in the capacitance value calculation step, A voltage measurement method in a non-contact voltage sensor device equipped with the following features.

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