JP2019203830A - Voltage measuring device and voltage measuring method - Google Patents

Abstract

To provide a voltage measuring device that can perform non-contact measurement of high voltage without causing an increase in cost.SOLUTION: A voltage measuring device measures an AC voltage at a first frequency, and comprises: an electrode; a constant voltage source that connects to the electrode and outputs an AC voltage at a second frequency; a current measuring unit that measures the magnitude of a current at the first frequency and the magnitude of a current at the second frequency flowing between the electrode and constant voltage source; and an operation unit that calculates the AC voltage at the first frequency on the basis of an output voltage from the constant voltage source, the magnitude of the current at the first frequency, the magnitude of the current at the second frequency, the first frequency, and the second frequency.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a voltage measuring apparatus and a voltage measuring method capable of measuring a voltage of a measurement object in a non-contact manner.

  Patent Document 1 discloses a voltage measurement apparatus 400 that can measure the voltage V1 of the measurement object 404 as shown in FIG. 8 in a non-contact manner. In the voltage measurement apparatus 400, the detection electrode 412 of the probe unit 402 is arranged in a non-contact state in the vicinity of the measurement object 404, and a capacitance C0 is formed between the detection electrode 412 and the measurement object 404. ing.

  In the voltage measuring device 400, when the variable capacitance element 413 is driven from the main body 403 with the AC signal S <b> 1, an alternating current i flows due to a change in the capacitance of the variable capacitance element 413. The magnitude of the current i is determined by the voltage difference between the voltage V1 of the measurement object 404 and the voltage V4 of the shield case of the probe unit 402. The current i is measured by the detection resistor 415 as the AC voltage V2, and a shield voltage V4 corresponding to the amplitude is generated from the voltage generation circuit 425.

  With this configuration, the shield voltage V4 of the voltage measuring device 400 is controlled so that the current i becomes 0. At this time, the shield voltage V4 is the same voltage as the voltage V1 of the measurement object 404. For this reason, the voltage V1 of the measurement object 404 can be measured by measuring the shield voltage V4 with the voltmeter 426.

JP 2007-132926 A

  In the voltage measuring apparatus 400, for example, when measuring a high voltage of several kV, the shield case of the probe unit 402 becomes a high voltage. Therefore, in order to ensure the safety of the measuring device, a high insulation design around the shield case, an electric shock prevention measure due to breakage, and the like are required. Further, a variable voltage source must be used as the voltage generation circuit 425 in order to control the shield voltage V4 so that the current i becomes zero. Therefore, the cost of the voltage measuring device 400 is increased.

  Accordingly, an object of the present invention is to provide a voltage measurement technique capable of non-contact measurement of a high voltage without causing an increase in cost.

In order to solve the above problems, a voltage measuring apparatus according to a first aspect of the present invention is a voltage measuring apparatus that measures an alternating voltage of a first frequency, and is connected to an electrode and the electrode, and has a second frequency. A constant voltage source that outputs an alternating voltage; a current measuring unit that measures the magnitude of the current of the first frequency and the magnitude of the current of the second frequency flowing between the electrode and the constant voltage source; The AC voltage of the first frequency is calculated based on the output voltage of the constant voltage source, the magnitude of the current of the first frequency, the magnitude of the current of the second frequency, the first frequency, and the second frequency. And an arithmetic unit.
According to the voltage measuring apparatus according to the first aspect of the present invention, the measurement side can measure at a voltage much lower than the voltage to be measured by making the second frequency sufficiently higher than the first frequency. In addition, expensive high-voltage components are not required for the components of the voltage measuring device. Moreover, since a high voltage is not generated inside the voltage measuring device, a high insulation design and an electric shock prevention measure are not required. Furthermore, since a constant voltage source having a constant frequency is used, a variable frequency oscillator and a variable voltage source are not necessary. Therefore, the cost increase as in the conventional technique can be prevented, and the voltage measuring device can be configured at low cost.
The calculation unit multiplies the ratio between the second frequency and the first frequency by the ratio between the current magnitude at the first frequency and the current magnitude at the second frequency and the output voltage of the constant voltage source. Thus, the alternating voltage of the first frequency can be calculated.
The constant voltage source may be connected to the electrode via a capacitor.
In order to solve the above-described problem, a voltage measurement method according to a second aspect of the present invention is a voltage measurement method for measuring an alternating voltage of a first frequency, and a measurement object to which the alternating voltage of the first frequency is applied. Measuring the magnitude of the current at the first frequency and the magnitude of the current at the second frequency flowing through the capacity when an AC voltage having a second frequency and a predetermined voltage is applied to the object via the capacity; An AC voltage of the first frequency is calculated based on the voltage, the magnitude of the current of the first frequency, the magnitude of the current of the second frequency, the first frequency, and the second frequency. .
The capacitance may include a parasitic capacitance.
The ratio between the second frequency and the first frequency is multiplied by the ratio between the magnitude of the current at the first frequency and the magnitude of the current at the second frequency and the predetermined voltage. Can be calculated.

  ADVANTAGE OF THE INVENTION According to this invention, the voltage measurement technique in which the high voltage non-contact measurement is possible, without causing cost increase is provided.

It is a figure explaining the measurement principle of the voltage measuring device of this invention. It is a figure explaining the example of grounding of a measuring object and a measurement side. It is a figure which shows the structure of 1st Example of the voltage measuring device of this invention. It is a figure which shows the structure of 2nd Example of the voltage measuring device of this invention. It is a figure which shows the structure of 3rd Example of the voltage measuring device of this invention. It is a figure which shows the structure of 4th Example of the voltage measuring device of this invention. It is a figure which shows the structure of 5th Example of the voltage measuring device of this invention. It is a figure explaining the conventional non-contact-type voltage measuring device.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining the measurement principle of the voltage measuring device of the present invention. In the voltage measuring instrument of the present invention, an AC voltage is a measurement object, and in this figure, an AC voltage Vx having a frequency fx is a measurement object. The present invention is particularly effective when the measurement target voltage Vx is a high voltage of about several kV, for example.

  On the measurement side, a constant voltage source 110 having an output voltage Vs at a frequency fs is provided. It is assumed that the frequency fx and the frequency fs are known and fs >> fx and Vx >> Vs. A capacitance C1 exists between the measurement target and the measurement side, and the measurement target and the measurement side are not in contact with each other. The capacity C1 may be unknown.

  The current at the frequency fx flowing through the capacitor C1 due to the voltage Vx to be measured is denoted as Ix, and the current at the frequency fs flowing through the capacitor C1 due to the voltage Vs of the constant voltage source 110 is denoted as Is. Actually, a current obtained by superimposing the current Ix and the current Is flows through the capacitor C1.

  On the measurement side, a current measurement unit 120 and a calculation unit 130 are provided. In addition, as shown to Fig.2 (a), a measurement object and the grounding of a measurement side may be common, and as shown in FIG.2 (b), it does not need to be common. Further, as shown in FIG. 2C, the reference potential with respect to the ground on the measurement side may vary.

  The current measuring unit 120 measures the magnitudes of the currents Ix and Is. The magnitude of the current may be any of amplitude, effective value, average value, and the like. The calculation unit 130 calculates and outputs the voltage Vx based on the measurement results of the current Ix and the current Is in the current measurement unit 120.

ここで、容量Ｃ１のインピーダンスについて［数２］が成り立つ。

［数１］と［数２］とから、

が得られる。 In this configuration, when the impedance of the capacitor C1 with respect to the current Ix is Xcx and the impedance of the capacitor C1 with respect to the current Is is Xcs, the current Ix and the current Is can be expressed as follows. However, the impedance of the constant voltage source 110, the current measurement unit 120, and the voltage source to be measured is assumed to be sufficiently small.

Here, [Equation 2] holds for the impedance of the capacitor C1.

From [Equation 1] and [Equation 2],

Is obtained.

  Since the frequency fx of the voltage to be measured, the voltage Vs and the frequency fs of the constant voltage source 110 are known, the current Ix and the current Is are measured to calculate the measurement target voltage Vx based on [Equation 3] and measure As a result, it can be output.

  For example, if the frequency fx of the voltage to be measured is 50 Hz of the commercial power supply, the frequency Vs of the constant voltage source 110 is 50 kH which is sufficiently larger than 50 Hz. A value obtained by multiplying the obtained Ix / Is becomes the voltage Vx to be measured. That is, even if the voltage to be measured is several kV, it can be measured with a voltage of several volts.

  As described above, in the present invention, since the measurement side can measure at a voltage much lower than the voltage to be measured, an expensive high-voltage component is not necessary as a component of the voltage measuring instrument. In addition, since a high voltage is not generated inside the voltage measuring device, a high insulation design and an electric shock prevention measure are not required. Furthermore, since the constant frequency constant voltage source 110 is used, a variable frequency oscillator and a variable voltage source are not necessary. Therefore, the cost increase as in the conventional technique can be prevented, and a voltage measuring device capable of high voltage non-contact measurement can be configured at low cost.

  Next, an embodiment of a voltage measuring device using the above measurement principle will be described. FIG. 3 is a diagram showing the configuration of the first embodiment of the voltage measuring instrument 100 of the present invention.

  In the example of this figure, the measurement object is the conductor 310 to which the voltage Vx having the frequency fx is applied. The conductor 310 is covered with an insulating coating 320 to form a covered electric wire 300.

  The voltage measuring device 100 according to the first embodiment includes an electrode 101, a current measurement unit 120, a calculation unit 130, and a display unit 140 that displays a measurement target voltage Vx calculated by the calculation unit 130 as a measurement result.

  The electrode 101 is attached to the covered electric wire 300. For this reason, the conductor 310 and the electrode 101 are not in contact with each other, and a parasitic capacitance C1 exists between the conductor 310 and the electrode 101. Since it is sufficient that the parasitic capacitance C1 exists between the conductor 310 and the electrode 101, a gap may be formed between the electrode 101 and the insulating coating 320, or further insulation is provided between the electrode 101 and the insulating coating 320. You may place your body. The electrode 101 may be arranged with an insulator or a gap interposed between conductors 310 not provided with the insulating coating 320. The same applies to the other embodiments.

  The current measuring unit 120 includes a resistor R121, an instrumentation amplifier 122 that detects a voltage generated in the resistor R121, a first filter unit 123a that passes a signal of frequency fx, a second filter unit 123b that passes a signal of frequency fs, The first AC-DC converter 124a that smoothes the signal of the frequency fx that has passed through the first filter unit 123a and converts the signal to the DC voltage Vmx, and the signal of the frequency fs that passes through the second filter unit 123b is smoothed and the DC voltage Vms. The second AC-DC converting unit 124b for converting into In this example, the constant voltage source 110 is connected to the electrode 101 via the current measurement unit 120.

  The DC voltage Vmx corresponds to the magnitude of the current Ix, and the DC voltage Vms corresponds to the magnitude of the current Is. In the current measurement unit 120, the resistor R121 and the instrumentation amplifier 122 constitute a current detection part that detects current, and the filter part 123 and the AC-DC conversion part 124 constitute an amplitude measurement part that measures amplitude. .

  The filter unit 123 removes frequency components and noise other than the passage target. The AC-DC conversion unit 124 outputs a DC voltage corresponding to the amplitude of the AC voltage output by the filter unit 123. The resistor R121 is desirably a small value in order to avoid an influence on the current Ix and the current Is.

  The calculation unit 130 calculates the measurement target voltage Vx based on the DC voltage Vmx, the DC voltage Vmx output from the current measurement unit 120, the known frequencies fs and fx, and the known voltage Vs, and the display unit 140 displays the measurement result. Display as.

  In addition, although the current detection part of the current measuring unit 120 is configured by the resistor R121 and the instrumentation amplifier 122, the present invention is not limited to this configuration, and various methods capable of acquiring a signal corresponding to the magnitude of the current are employed. can do. For example, a magnetic field due to current may be detected using a hall sensor, a current transformer circuit, or the like, and a voltage proportional to the magnitude of the current may be output. Further, instead of the resistor R121, a capacitor, a coil, or a combination thereof may be used.

  The first filter unit 123a and the second filter unit 123b include an active bandpass filter VCVS (salen key) type, multiple feedback type, state variable type, passive bandpass filter LC bandpass filter, and RLC bandpass. Various systems such as a filter can be used.

  The first AC-DC converter 124a and the second AC-DC converter 124b include various types such as an RMS-DC converter (effective value detection), a full-wave average or half-wave average average value detection, a peak hold circuit, and the like. This method can be used.

  Next, a second embodiment of the voltage measuring device 100 of the present invention will be described with reference to FIG. In the second embodiment, the amplitude measurement portion of the current measurement unit 120 is configured using the synchronous detection circuit 125. The synchronous detection circuit is a circuit that converts the magnitude of a signal having the same frequency component as that of a reference signal among input signals into a DC voltage and outputs the signal.

  In the example of this figure, the DC voltage Vmx corresponding to the magnitude of the signal of the frequency fx is obtained from the output signal of the current measurement portion using the first synchronous detector 125a, and the frequency fs using the second synchronous detector 125b. The DC voltage Vms corresponding to the magnitude of the signal is obtained. The voltage measuring device 100 according to the second embodiment includes a sine wave oscillator 126 having a frequency fx for the reference signal of the first synchronous detection unit 125a. The reference signal of the second synchronous detector 125b uses the output signal of the constant voltage source 110 having the frequency fs.

  Next, a third embodiment of the voltage measuring device 100 of the present invention will be described with reference to FIG. In the third embodiment, the amplitude measurement of the current measuring unit 120 is performed by digital signal processing. For this reason, the A / D converter 127 for converting the output signal of the current detection portion into digital data, the frequency separator (fx) 128a for separating the signal of frequency fx and extracting Vmx, and the signal of frequency fs And a frequency separator (fs) 128b for extracting Vms. The frequency separator 128 can be configured using a digital filter or a synchronous detection circuit.

  Next, a fourth embodiment of the voltage measuring device 100 of the present invention will be described with reference to FIG. The fourth embodiment is applicable to a case where an accurate frequency to be measured is not known. Although the description will be based on the configuration of the first embodiment, it may be applied to other embodiments.

  In the fourth embodiment, the frequency measurement unit 129 is used to measure the frequency of the signal that has passed through the first filter unit 123a to obtain the accurate frequency fx to be measured. The calculation unit 130 calculates the measurement target voltage Vx based on the DC voltage Vmx, the DC voltage Vmx, the frequency fx, the known frequency fx, and the known voltage Vs output from the current measurement unit 120, and the display unit 140 performs measurement. Display as a result. In addition, the 1st filter part 123a shall use the filter which contains the approximate frequency of a measuring object in a pass band.

  The frequency measuring unit 129 can use various methods. For example, a method of measuring the number of times that the input signal and the reference voltage intersect at a fixed measurement time, a method of measuring the time (period) at which the input signal and the reference voltage intersect, and the like can be used.

  Next, a fifth embodiment of the voltage measuring device 100 of the present invention will be described with reference to FIG. In the fifth embodiment, the electrode 101 can measure the voltage not only in contact with the measurement object but also in the contact state. The electrode 101 is in contact with the measurement object, but the measurement object and the measurement side are not in contact with each other because the capacitance C1 exists between the measurement object and the measurement side. Here, the description is based on the configuration of the first embodiment, but the present invention may be applied to other embodiments.

  In the voltage measuring device 100 of the fifth embodiment, an actual capacitor 102 is connected between the electrode 101 and the current measuring unit 120. In this example, the constant voltage source 110 is connected to the electrode 101 via the capacitor 102 and the current measuring unit 120.

  By connecting the actual capacitor 102, the measurement object voltage Vx can be measured because the capacitor 102 plays the role of the capacitance C1 even when the electrode 101 is in contact with the conducting wire 330. Moreover, when measuring the covered wire | conductor 300, since the synthetic capacity of a parasitic capacitance and the capacitor | condenser 102 plays the role of the capacity | capacitance C1, the measurement object voltage Vx can be measured. That is, the measurement target voltage Vx can be measured regardless of whether or not the electrode 101 is in contact with the measurement target.

DESCRIPTION OF SYMBOLS 100 Voltage measuring device 101 Electrode 102 Capacitor 110 Constant voltage source 120 Current measurement part 121 Resistance 122 Instrumentation amplifier 123 Filter part 124 AC-DC conversion part 125 Synchronous detection circuit 126 Sine wave oscillator 127 A / D conversion part 128 Frequency separator 129 Frequency measurement unit 130 Calculation unit 140 Display unit 300 Insulated wire 310 Conductor 320 Insulation coating 330 Conductor

Claims (6)

A voltage measuring device for measuring an alternating voltage of a first frequency,
Electrodes,
A constant voltage source connected to the electrode and outputting an alternating voltage of a second frequency;
A current measuring unit that measures the magnitude of the current at the first frequency and the magnitude of the current at the second frequency flowing between the electrode and the constant voltage source;
The AC voltage of the first frequency is calculated based on the output voltage of the constant voltage source, the magnitude of the current of the first frequency, the magnitude of the current of the second frequency, the first frequency, and the second frequency. An arithmetic unit to perform,
A voltage measuring device comprising:   The computing unit multiplies the ratio between the second frequency and the first frequency by the ratio between the current magnitude at the first frequency and the current magnitude at the second frequency and the output voltage of the constant voltage source. The voltage measuring device according to claim 1, wherein the AC voltage of the first frequency is calculated.   The voltage measuring apparatus according to claim 1, wherein the constant voltage source is connected to the electrode via a capacitor. A voltage measurement method for measuring an alternating voltage of a first frequency,
When a second frequency, an alternating voltage of a predetermined voltage is applied to a measurement object to which the alternating voltage of the first frequency is applied, the magnitude of the current of the first frequency flowing through the capacitor and the first Measure the magnitude of the current at two frequencies,
An AC voltage of the first frequency is calculated based on the predetermined voltage, the magnitude of the current of the first frequency, the magnitude of the current of the second frequency, the first frequency, and the second frequency. Voltage measurement method.   The voltage measurement method according to claim 4, wherein the capacitance includes a parasitic capacitance.   The ratio between the second frequency and the first frequency is multiplied by the ratio between the magnitude of the current at the first frequency and the magnitude of the current at the second frequency, and the predetermined voltage, to thereby generate an AC voltage at the first frequency. The voltage measurement method according to claim 4, wherein the voltage is calculated.

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