Contactless voltage sensor device, and voltage measurement method of contactless voltage sensor device

Abstract

A contactless voltage sensor device comprises: a contactless voltage sensor (10) that measures the voltage in a power line (100) while not being in electrical contact with a conductor (110) therein, said power line (100) having the conductor (110), to which power is supplied from a commercial power source (200), and an insulator (120) that covers the conductor (110); a zero-crossing point detection unit (32) that receives an output from the contactless voltage sensor (10) and, upon detecting a zero potential in the output from the contactless voltage sensor (10), outputs a calibration mode command signal indicating a calibration mode; and a calibration signal circuit (20) that, upon receiving the calibration mode command signal indicating the calibration mode from the zero-crossing point detection unit (32), outputs a calibration signal to the contactless voltage sensor (10).

Description

Non-contact voltage sensor device and voltage measurement method for the non-contact voltage sensor device

[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.

[0002] When measuring the voltage of 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 shows a non-contact voltage measurement device that measures the AC voltage in a conductor by using 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 the signal current through the conductor and the reference current through the 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 the 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, including different calibration factors for multiple physical locations on the conductor.

[0005] Japanese Patent Application Laid-Open No. 2019-215329

[0006] Generally, when power is supplied to a power line from a commercial power source, the calibration signal used in the calibration process has a small amplitude compared to the voltage amplitude of the commercial power source. Even in the non-contact voltage sensor device disclosed in Patent Document 1, the AC voltage of the reference voltage source is 2.4 V compared to the AC voltage of 120 V in the conductor. In this way, when the voltage amplitude of the calibration signal used in the calibration process is small compared to the voltage amplitude to be observed, a problem arises 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 points, and has an object to provide a contactless voltage sensor device that can maintain high accuracy in calibration processing even when using a calibration signal whose voltage amplitude is relatively small compared to the voltage amplitude of an object to be observed.

[0008] The non-contact voltage sensor device of the present disclosure includes 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 electrically contacting 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.

[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.

[0010] Fig. 1 is a block diagram showing an example of the configuration of a non-contact voltage sensor device according to embodiment 1. Fig. 2 is a waveform diagram showing an outline of a voltage waveform (superimposed waveform) in the output from a non-contact voltage sensor in a calibration mode in the non-contact voltage sensor devices according to embodiments 1 and 2. Fig. 3 is a flowchart showing a calibration method in the non-contact voltage sensor device according to embodiment 1. Fig. 4 is a waveform diagram showing an outline of a voltage waveform (superimposed waveform) in the output from a non-contact voltage sensor in a calibration mode in the non-contact voltage sensor device according to embodiment 3.

[0011] Embodiment 1 A non-contact voltage sensor device according to embodiment 1 will be described with reference to Figures 1 to 3. The non-contact voltage sensor device according to 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, for example, a power distribution system of a building or factory building.

[0012] The non-contact voltage sensor device according to the first embodiment performs a calibration process when it detects that the voltage on the power line is at zero potential. 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] Non-contact voltage sensor 10 measures the voltage of power (voltage value Vin of the observation signal) from commercial power source 200 supplied to power line 100, which is made up of a cable having conductor (cable core) 110 and insulator 120 covering conductor 110, without electrically contacting conductor 110 in power line 100. Power is applied from commercial power source 200 to conductor 110, and non-contact voltage sensor 10 measures voltage value Vin (voltage amplitude) at conductor 110.

[0014] The non-contact voltage sensor 10 has a probe electrode 11, a sensor unit 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 arranged in contact with or close 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 arranged close to the conductor 110 of the power line 100, and a coupling capacitance 310 is generated between the probe electrode 11 and the conductor 110 of the power line 100.

[0017] The probe electrode 11 detects the voltage waveform in the conductor 110 via a 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 has a different capacitance value depending on the attachment or removal of the probe electrode 11 to 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 digitizes voltage data based on the voltage waveform detected by the probe electrode 11. The sensor unit 12 includes an amplifier element 12a, a negative feedback circuit 12b, and an analog-to-digital (AD) converter 12c.

[0020] The amplifier 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 amplifier element 12a and the negative feedback circuit 12b form an operational amplifier. The analog voltage output from the output terminal of the amplifier element 12a is converted into digital data by an AD converter 12c and output.

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

[0022] In the calibration mode, a calibration signal from the calibration signal circuit 20 is input to the non-inverting input terminal of the amplifying element 12a. The operation mode is a normal operation mode in which the voltage waveform in the conductor 110 is measured. In the calibration mode, the capacitance value C １ This is a mode for identifying the coupling capacitance 310 whose value is unknown (unknown quantity).

[0023] The negative feedback circuit 12b is a capacitor 12b １ and resistor 12b ２ The capacitor 12b in the negative feedback circuit 12b is a parallel combination of the first and second impedance elements. １ is a variable capacitor whose capacitance value is variable, and in response to a gain change command signal, the capacitance value in the calibration mode is set to a value smaller than the capacitance value 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 connection of a plurality of capacitor elements using a switch element.

[0025] The second impedance element of the negative feedback circuit 12b and the first impedance element 300 are in a corresponding relationship. １ and the coupling capacitance 310 in the first impedance element 300 correspond to each other, and the resistor 12b in the negative feedback circuit 12b ２ and the insulation resistance 320 in the first impedance element 300 have a corresponding relationship.

[0026] In the operation mode, the non-inverting input terminal of the amplifying element 12a is at zero potential, i.e., 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, i.e., the voltage amplitude, is expressed by the following equation (1).

[0027]

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

[0029] In the operation mode, the impedance Z of the negative feedback circuit (second impedance element) 12b ２０ is the impedance Z of the first impedance element 300 １ (=1 / (jωC １ )) is an unknown, so impedance Z １That is, the output gain G ０ Z is ２０ / Z １ is set to 1 / 100, that is, about 0.01.

[0030] Therefore, in the operational mode, the amplifier element 12a has an output gain G ０ =-Z ２０ / Z １ (≈0.01). In the frequency range of the commercial power supply 200, the contribution of the resistance component is small, so Z ２０ / Z １ ≒C １ / C ２０ The following relationship can be assumed.

[0031] Capacitor 12b in negative feedback circuit 12b in the calibration mode １ The capacitance value C ２１ The capacitance value C in operation mode ２０ Since the output gain G of the amplifying element 12a in the calibration mode is set to a smaller value, １ is the output gain G of the amplifying element 12a in the operation mode. ０ It becomes bigger.

[0032] In the first embodiment, in the calibration mode, the capacitance value C ２１ The capacitance value C ２０ Since the output gain is 1 / 100 of １ is approximately 1 according to the following equation (2). That is, the output gain G １ is the output gain G of the amplifying element 12a in the operation mode. ０ It is approximately 100 times larger than that.

[0033] G １ =-Z ２１ / Z １ ≒C １ / C ２１ =C １ / (C ２０ × 1 / 100) = (C １ / 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, C２１ is the capacitor 12b in the negative feedback circuit 12b in the calibration mode １ is the capacitance value.

[0034] In the operation mode, the output terminal of the calibration signal circuit 20 is set to ground potential, and the non-inverting input terminal of the amplifying element 12a is set to zero potential. In the calibration mode in which a calibration mode command signal Enable indicating the calibration mode is received, 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 orthogonal to the AC voltage from commercial power supply 200. The voltage value Vref of the calibration signal is a minute voltage having a different dynamic range from the voltage (100 V or 200 V) of commercial power supply 200, and in the first embodiment, is, for example, 1.0 V or more and 2.4 V or less. Furthermore, the frequency fref of the calibration signal is higher than the frequency fin of commercial power supply 200, and in the first embodiment, is an integer multiple n (n is a natural number equal to or greater than 2) of the frequency fin of commercial power supply 200, that is, fref = n × fin.

[0036] Before explaining the calibration mode, when power is not supplied to the conductor 110 from the commercial power supply 200 and a calibration signal (voltage value Vref) is input from the calibration signal circuit 20 to the non-inverting input terminal of the amplifying element 12a, the output voltage value Vout1 of the amplifying element 12a is expressed by the following equation (3).

[0037]

[0038] When power is not supplied from the commercial power supply 200, the amplifier element 12a outputs a gain G ２ = 1 + Z ２１ / Z １ Since the contribution of the resistance component is small in the frequency domain of the calibration signal, Z ２１ / Z １ ≒C １ / C ２１ Therefore, the output gain G ２ is the output gain G of the amplifying element 12a in the operation mode. ０ It becomes bigger.

[0039] In the above equation (3), the voltage value Vref of the calibration signal and the capacitor 12b in the negative feedback circuit 12b １ The capacitance value C ２１ is known, the capacitance value C of the coupling capacitor 310 can be obtained by obtaining the output voltage value Vout1 of the amplifying element 12a. １ In the above formula (3), Z ２１ / Z １ The term Z corresponds to the output gain in operational mode. ２０ / Z １ Since the output voltage Vout1 is significantly larger than the ２１ / Z １ The relative contribution of the term becomes larger, and the capacitance value C １ 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 of conductor 110 detected by probe electrode 11, and therefore output voltage value Vout2 of amplifying element 12a is expressed by the following equation (4).

[0041]

[0042] The above equation (4) shows the output voltage value Vout2 of the amplifier 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 amplifier element 12a. The capacitance value C of the coupling capacitance 310 from the output voltage value Vout2 is １ Since the AC voltage of the calibration signal is orthogonal to the AC voltage from the commercial power supply 200, the output voltage value of the amplifier element 12a corresponding to the voltage value Vref of the calibration signal is extracted from the superimposed signal by processing such as Fourier transform of the output voltage of the amplifier element 12a.

[0043] The output voltage value for the extracted voltage value Vref of the calibration signal corresponds to the output voltage value Vout1 shown in the above equation (3). １ The capacitance value C２１ is known, the capacitance value C of the coupling capacitor 310 can be calculated from the output voltage value for the voltage value Vref of the extracted calibration signal. １ can be calculated.

[0044] The calibration process is performed when a zero potential is detected in the voltage value of the conductor 110 detected by the probe electrode 11. Therefore, the output gain G of the amplifier element 12a is set to 0 in order to extract the calibration signal and to improve the measurement accuracy. １ Even if the voltage Vin measured by the probe electrode 11 at the conductor 110 in the power line 100 is increased, the voltage Vref of the calibration signal is at the same level as the voltage Vin measured by the probe electrode 11 at the conductor 110 in the power line 100, and the voltage Vref of the calibration signal can be extracted with high accuracy from the output voltage Vout2 without causing waveform distortion in the output voltage Vout2 of the amplifying element 12a.

[0045] Calibration signal circuit 20 has calibration signal source 21 and 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 frequency fin of commercial power supply 200, for example, fref = n × fin (n is a natural number of 2 or more), and whose voltage value Vref is a minute voltage value Vref, for example, 1 V, whose dynamic range differs from that of voltage value Vin from commercial power supply 200.

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

[0047] When the calibration mode command signal Enable indicates the calibration mode, that is, 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 applies the calibration signal from the calibration signal source 21 to the non-inverting input terminal of the amplifying element 12a. The calibration mode command signal Enable is an H level signal when indicating the calibration mode, and is an L level signal when not indicating the calibration mode.

[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 supply 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 has a measurement processing section 31, a zero-cross point detection section 32, and a gain control section 33. The measurement processing section 31 receives voltage waveform data from the AD converter 12c of the sensor section 12 in the non-contact voltage sensor 10, and calculates the capacitance value C of the coupling capacitance 310 calculated in the calibration mode from the input voltage waveform data. １ A calibrated voltage value for the voltage value Vin of the commercial power supply 200 supplied to the conductor 110 is calculated using

[0050] That is, the calibrated voltage value is the voltage value Vout0 from the AD converter 12c, the capacitance value C of the coupling capacitance 310 calculated in the calibration mode, １ , and the capacitor 12b in the negative feedback circuit 12b in the operational mode. １ The capacitance value C ２０ By using the above, Vin calculated by the relational expression (1) is obtained, 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 value of the calibrated voltage values ​​obtained by performing the calculation multiple times is calculated, and the calculated average value is used 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 capacitor 12b in the negative feedback circuit 12b in the calibration mode. １ The capacitance value C ２１By using the above equation (2), the capacitance value C of the coupling capacitor 310 is １ Calculate.

[0053] Zero-cross point detector 32 receives the output from non-contact voltage sensor 10, and outputs a calibration mode command signal when it detects a zero potential in the output from non-contact voltage sensor 10. Zero-cross point detector 32 monitors the time when the calibrated voltage values ​​calculated by measurement processor 31 and stored in chronological order in the memory unit reach a zero potential, that is, 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-crossing point detection unit 32 detects a zero potential in the output from non-contact voltage sensor 10, that is, a zero-crossing point in commercial power supply 200, it outputs a calibration mode command signal Enable indicating the calibration mode to calibration signal circuit 20 in synchronization with the zero-crossing points that occur periodically in commercial power supply 200, and for a fixed period Ten centered around the zero-crossing point, as shown in Figures 1 and 2 .

[0055] Zero-cross point detection unit 32 detects zero-cross points 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] Zero-crossing point detection unit 32 outputs a mode command signal Enable to calibration signal circuit 20, which indicates a calibration signal that sets the start time of the calibration mode to Ten / 2 hours before the zero-crossing point in the detection time of zero potential and the end time of the calibration mode to Ten / 2 hours after the zero-crossing point in the detection time of zero potential. As a result, the calibration signal that is 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 (an even function) with respect to the zero-crossing point 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 H level during the calibration mode period Ten, indicating the calibration mode.

[0058] In addition, the zero-cross point detection unit 32 may detect the zero-cross point 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 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 detection unit 32 may detect the zero potential every time a zero-cross point appears in the commercial power supply 200, or may detect the zero potential at regular time intervals, for example, at time intervals of 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 adjusts the output gain of the amplifier element 12a in the sensor unit 12 of the non-contact voltage sensor 10 to be larger in the calibration mode than in the operation mode. １ The capacitance value C in the calibration mode ２１ The capacitance value C in operation mode ２０ A 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 is generated at the start time of the calibration mode in the mode command signal Enable, that is, at the rise from L level to H level, by the capacitor 12b. １ The capacitance value of C ２０From C ２１ The switching signal is used to change the voltage of the capacitor 12b to the voltage of the capacitor 12b when the calibration mode ends in the mode command signal Enable, that is, when the voltage of the capacitor 12b falls from the H level to the L level. １ The capacitance value of C ２１ From C ２０ This is a switching signal to change to.

[0063] That is, the gain change command signal is applied to the capacitor 12b during the calibration mode period Ten when the mode command signal Enable indicates the calibration mode. １ The capacitance value of C ２１ During the operational mode, the capacitor 12b １ The capacitance value of C ２０ This is a command signal to maintain the

[0064] Therefore, during the period when the calibration signal circuit 20 supplies the calibration signal to the non-inverting input terminal of the amplifying element 12a in response to the mode command signal Enable from the zero-cross point detector 32, the gain controller 33 supplies the capacitor 12b １ The capacitance value of C ２１ The gain change command signal is sent to the negative feedback circuit 12b.

[0065] As a result, in the calibration mode, the calibration signal can be amplified with the output gain of the amplifier element 12a set to be greater than the output gain in the operation mode, thereby enabling highly accurate calibration. The hardware configuration of the measurement processing unit 31, the zero-cross point detection unit 32, and the gain control unit 33 that make up the control circuit 30 is a microcomputer or the like.

[0066] Next, a method for measuring the voltage in power line 100 supplied with power from a commercial power source using the non-contact voltage sensor device according to embodiment 1 will be described with reference to Fig. 3. In step ST1, non-contact voltage sensor 10 detects the voltage value (voltage waveform) Vin in conductor 110 of power line 100 supplied with power from the commercial power source through probe electrode 11 via coupling capacitance 310 without being in electrical contact with conductor 110.

[0067] In step ST2, zero-cross point detection unit 32 detects a zero potential in the output obtained by amplifying the voltage waveform detected by probe electrode 11 by sensor unit 12, and outputs a calibration mode command signal indicating the calibration mode. Step ST2 is a calibration mode command step. In step ST3, upon receiving the calibration mode command signal indicating the calibration mode output from zero-cross point detection unit 32 in step ST2, calibration signal circuit 20 outputs a calibration signal to 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 controls the variable capacitor 12b １ The capacitance value C ２１ The capacitance value C in operation mode ２０ Step ST4 is a capacitance value change command step. In step ST5, the measurement processing unit 31 outputs a gain change command signal to change the capacitance value C of the coupling capacitor 310 in the calibration mode. １ Step ST5 is a capacitance value calculation step.

[0069] In step ST6, the measurement processing unit 31 compares the output from the non-contact voltage sensor 10 and the capacitance value C of the coupling capacitance 310 calculated in step ST5 (capacitance value calculation step) in the operation mode. １ The voltage Vin on the power line 100 is calculated using the above equation. 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 calibration mode when it detects 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 calibration mode from zero-cross point detection unit 32.Therefore, it is possible to maintain high accuracy in 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, a minute voltage having a different dynamic range from the voltage of the commercial power supply 200 is used as the calibration signal from the calibration signal circuit 20, and the output gain of the amplifying element 12a in the non-contact voltage sensor 10 in the calibration mode is set to be higher than the output gain in the operation mode. １ Since the capacitance value in the calibration mode is set to a value smaller than the capacitance value in the operation mode, no waveform distortion occurs in the output from non-contact voltage sensor 10, and highly accurate calibration processing can be achieved.

[0072] Embodiment 2 A non-contact voltage sensor device according to embodiment 2 differs from the non-contact voltage sensor device according to embodiment 1 in that the calibration mode period Ten is specified to be a time that is an integer multiple m (a natural number of 2 or more) 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] The components of the non-contact voltage sensor device of embodiment 2 are essentially the same as the components of the non-contact voltage sensor device of embodiment 1 shown in Figure 1, so Figures 1 and 3 will be used to explain the calibration signal output from calibration signal source 21, and Figure 2 will be used to mainly explain the calibration signal.

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

[0075] As explained in the first embodiment, the voltage waveform of the calibration signal output from calibration signal source 21 is orthogonal to the voltage from commercial power supply 200. Furthermore, in the second embodiment, in response to mode command signal Enable indicating the calibration mode from zero-cross point detector 32, 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 greater) of wavelength λ of the calibration signal, centered on a zero-cross point in commercial power supply 200, as shown in FIG.

[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 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 according to embodiment 3 is the same as the non-contact voltage sensor device according to embodiment 1 except 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 supply 200 and is specified as an even function waveform centered on the zero-crossing points.

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

[0079] As explained in the first embodiment, the calibration signal output from the calibration signal source 21 has a frequency fref higher than the frequency fin of the commercial power supply 200, for example, fref = n × fin (n is a natural number of 2 or more), and is a sine wave with a voltage value Vref of a minute voltage value Vref, for example, 1 V, which has a different dynamic range from the voltage value Vin of the 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 , calibration signal circuit 20 adjusts the calibration signal output from calibration signal source 21, and 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 whose waveform is an even function centered on the zero-cross points.

[0081] That is, as shown in FIG. 4 , during the calibration mode period of −t1 to +t1 centered around a zero-cross point in commercial power supply 200 in response to mode command signal Enable indicating the calibration mode from zero-cross 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 is an even function waveform whose amplitude is maximum at the zero-cross point in commercial power supply 200 and is symmetrical left and right with respect to the time axis.

[0082] As shown in FIG. 4 , the voltage waveform detected by the probe electrode 11 corresponds to the voltage waveform on the power line 100 when power is supplied from the commercial power source 200 to the power line 100, and is an odd function waveform because it is synchronized with the zero crossing points of the 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 corresponding to 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 an arithmetic average of the data of the voltage value Vout2 from the AD converter 12c 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.

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

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

[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 corresponding to the voltage value Vref of the calibration signal from the voltage value Vout2 from the AD converter 12c with high accuracy using a simple processing method called additive 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.

[0088] The non-contact voltage sensor device according to the present disclosure is suitable for use in a power distribution system such as a building or factory building as a non-contact voltage sensor device 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 conductor of the power line.

[0089] 10 Non-contact voltage sensor, 11 Probe electrode, 12 Sensor unit, 12a Amplifying element, 12b Negative feedback circuit, 12b １ Capacitor, 12b ２Resistor, 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 device comprising: 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 making electrical contact with the conductor in the power line; a zero-cross point detection unit that receives the output from the non-contact voltage sensor and outputs a calibration mode command signal indicating 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 calibration mode from the zero-cross point detection unit.

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

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

4. A 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 (n is a natural number of 2 or greater) of the frequency of the commercial power supply.

5. A non-contact voltage sensor device as described in any one of claims 1 to 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 the calibration mode from the zero-cross point detection unit has a waveform symmetrical with respect to the zero-cross point in the commercial power supply.

6. A non-contact voltage sensor device as described in any one of claims 1 to 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 the calibration mode from the zero-cross point detection unit is symmetrical with respect to the zero-cross point in the commercial power supply and has an even function waveform centered on the zero-cross point.

7. A method for measuring a voltage in a power line in a non-contact state, comprising: a probe electrode placed in contact with or close to the surface of an insulator of a power line having a conductor to which power is supplied from a commercial power source and an insulator covering the conductor; and an amplifying element connected to a negative feedback circuit which is a parallel combination of a variable capacitor and a resistor, and to which a voltage waveform measured by the probe electrode is input, the method comprising: a calibration mode command step in which a zero-crossing point detection unit outputs a calibration mode command signal indicating a calibration mode when detecting zero potential in the output from the non-contact voltage sensor; a calibration signal output step in which a calibration signal circuit outputs a calibration signal to the non-contact voltage sensor when receiving a calibration mode command signal indicating the calibration mode; a capacitance value change command step in which a gain control unit outputs a gain change command signal to change the capacitance value of the variable capacitor to a value smaller than the capacitance value in operation mode when the calibration mode command signal indicates the calibration mode; and a capacitance value calculation step in which a measurement processing unit calculates the capacitance value of the coupling capacitance in the calibration mode. a voltage measurement step in which a measurement processing unit calculates, in an operation mode, a voltage on the power line using an output from the non-contact voltage sensor and the capacitance value of the coupling capacitance calculated in the capacitance value calculation step.

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