JP2018179927A - Voltage measuring device and voltage measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage measuring device with which it is possible to measure a high voltage contactlessly without incurring an increase in cost.SOLUTION: Provided is a voltage measuring device for measuring an AC voltage of first frequency, comprising: an electrode; a variable frequency oscillation unit, connected to the electrode, for outputting an AC signal of second frequency that is fixed with a fist voltage; a current detection unit for detecting a current flowing between the electrode and the variable frequency oscillation unit; a difference extraction unit for extracting, from the detected current, a value equivalent to a difference between the magnitude of the first frequency and the magnitude of the second frequency and outputting it; a frequency adjustment unit for varying the second frequency of the variable frequency oscillation unit so that the output of the difference extraction unit becomes 0; and a computation unit for calculating an AC voltage of the first frequency on the basis of the first voltage, the first frequency and the second frequency.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a voltage measuring device and a voltage measuring method capable of contactlessly measuring the voltage of an object to be measured.

  Patent Document 1 discloses a voltage measuring apparatus 400 capable of contactlessly measuring the voltage V1 of the measurement object 404 as shown in FIG. In the voltage measuring device 400, the detection electrode 412 of the probe unit 402 is disposed in the vicinity of the measurement object 404 in a non-contact state, and a capacitance C0 is formed between the detection electrode 412 and the measurement object 404 It is done.

  In the voltage measurement device 400, when the variable capacitance element 413 is driven from the main body 403 by the alternating current signal S1, an alternating current i flows due to a change in 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 object to be measured 404 and the voltage V4 of the shield case of the probe unit 402. The current i is measured as the AC voltage V2 by the detection resistor 415, and the 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 measurement device 400 is controlled so that the current i becomes 0, and at this time, the shield voltage V4 becomes the same voltage as the voltage V1 of the measurement object 404. Therefore, by measuring the shield voltage V4 with the voltmeter 426, the voltage V1 of the object to be measured 404 can be measured.

JP 2007-132926 A

  In the voltage measurement 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 apparatus, it is necessary to have a high insulation design around the shield case and measures to prevent electric shock due to breakage or the like. For this reason, cost increase of the voltage measurement apparatus 400 is caused.

  Therefore, an object of the present invention is to provide a voltage measurement technique that can perform high-voltage non-contact measurement without increasing the cost.

In order to solve the above-mentioned subject, the voltage measuring device which is the 1st mode of the present invention is a voltage measuring device which measures the exchange voltage of the 1st frequency, and it connects with an electrode and the electrode, and uses the 1st voltage. The first frequency from the variable frequency oscillating unit outputting the alternating current signal of the fixed second frequency, the current detecting unit detecting the current flowing between the electrode and the variable frequency oscillating unit, and the detected current A difference extracting unit that extracts and outputs a value corresponding to the difference between the magnitude of the component and the magnitude of the second frequency component, and the output of the difference extracting unit becomes 0, A frequency adjustment unit that changes two frequencies; and an operation unit that calculates an AC voltage of the first frequency based on the first voltage, the first frequency, and the second frequency. Do.
Here, the calculation unit may calculate an alternating current voltage of the first frequency by multiplying the second frequency by a value obtained by dividing the first voltage by the first frequency.
Furthermore, the electrode and the variable frequency oscillation unit may be connected via a capacitor.
Further, the variable frequency oscillation unit may be capable of switching the value of the first voltage.
In order to solve the above-mentioned subject, the voltage measuring method which is the 2nd mode of the present invention is a voltage measuring method which measures the alternating current voltage of the 1st frequency, and the measurement object to which the alternating current voltage of the 1st frequency was applied The magnitude of the first frequency component and the magnitude of the second frequency component of the current flowing through the capacitor when an AC voltage of the second frequency fixed at the first voltage via the capacitor is applied to the object The second frequency is adjusted to be the same, and an AC voltage of the first frequency is calculated based on the first voltage, the first frequency, and the second frequency at that time. .

  According to the present invention, there is provided a voltage measurement technique capable of high-voltage non-contact measurement without increasing cost.

It is a figure explaining the measurement principle of the voltage measuring device of this invention. 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 instrument.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a view 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 to be measured, and in the figure, an AC voltage Vx of frequency fx is to be measured. It is assumed that the frequency fx is known. The alternating voltage Vx is, for example, about several hundred volts to several kilovolts.

  On the measurement side, a variable frequency oscillating unit 110 capable of changing the frequency fs is provided. The output voltage of variable frequency oscillation unit 110 is fixed at voltage Vs. A capacitance C1 exists between the measuring object and the measuring side. The capacity C1 may be unknown.

  The current of frequency fx flowing through the capacitor C1 due to the voltage Vx to be measured is Ix, and the current of frequency fs flowing through the capacitor C1 due to the voltage Vs of the variable frequency oscillating unit 110 is Is. In practice, a current obtained by superposing the current Ix and the current Is flows through the capacitor C1.

  On the measurement side, a current detection unit 120, a difference extraction unit 130, a frequency adjustment unit 140, a frequency measurement unit 150, and a calculation unit 160 are provided. The grounding of the measurement target and the measurement side may not be common.

  The current detection unit 120 detects the current in which the current Ix and the current Is are superimposed. The difference extraction unit 130 extracts and outputs a value corresponding to the difference between the magnitude of the current Ix and the magnitude of the current Is from the detection result of the current detection unit 120. The frequency adjustment unit 140 changes the output frequency fs of the variable frequency oscillation unit 110 so that the output of the difference extraction unit 130 becomes 0, that is, the magnitude of the current Is becomes equal to the magnitude of the current Ix.

  The frequency measurement unit 150 measures the output frequency fs of the variable frequency oscillation unit 110. Arithmetic unit 160 calculates and outputs voltage Vx to be measured based on the measurement result of frequency fs in frequency measurement unit 150. The output of the voltage Vx can be display on a display device, data output to another device, or the like.

ここで、

が成り立つので、［数５］が得られる。

差分抽出部１３０と周波数調整部１４０により、Ｉｘ＝Ｉｓとなるように電圧Ｖｓが調整されるため、［数１］［数２］より、

そして、［数５］［数６］より［数７］が得られる。

したがって、演算部１６０は、可変周波数発振部１１０の既知の固定出力電圧Ｖｓを測定対象交流電圧の既知の固定周波数ｆｘで割って得られた固定値に、周波数測定部１５０の測定値ｆｓを乗じる演算を行なうことで、測定対象電圧Ｖｘを算出し、測定結果として出力することができる。 In this configuration, assuming that 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.

here,

Since it holds, [Equation 5] is obtained.

Since the voltage Vs is adjusted by the difference extraction unit 130 and the frequency adjustment unit 140 so that Ix = Is, according to [Equation 1] [Equation 2],

Then, [Equation 7] is obtained from [Equation 5] and [Equation 6].

Therefore, operation unit 160 multiplies measurement value fs of frequency measurement unit 150 by a fixed value obtained by dividing known fixed output voltage Vs of variable frequency oscillation unit 110 by known fixed frequency fx of the AC voltage to be measured. By performing the calculation, the voltage Vx to be measured can be calculated and output as the measurement result.

  For example, assuming that the frequency fx of the voltage to be measured is 50 Hz of a commercial power supply, if the measured frequency fs is 50 kH, a value obtained by multiplying the voltage Vs by 1000 becomes the voltage Vx to be measured. That is, by setting the voltage Vs to several volts, even if the voltage to be measured is several kilovolts, measurement can be performed at a voltage of several volts. In this case, if the voltage Vs is 1 V, the voltage Vx to be measured is measured as 1 kV.

  The fixed output voltage Vs of the variable frequency oscillation unit 110 may be selected from a plurality of values. As a result, the measurement range can be switched according to the voltage to be measured, and the measurement range can be expanded by performing the calculation according to the fixed output voltage Vs to which the calculation unit 160 is switched.

  For example, assuming that the variable band of the variable frequency oscillation unit 110 is 25 kHz to 50 kHz, when the fixed output voltage Vs is 1 V, the AC voltage Vx of 50 Hz can be measured in the range of 0.5 kV to 1 kV. Assuming that the fixed output voltage Vs is switched between 1 V and 0.5 V, the voltage Vx can be measured in the range of 0.25 kV to 1 kV.

  As described above, according to the present invention, since the measurement side can perform measurement at a voltage much lower than the voltage to be measured, expensive high withstand voltage components are not required for the components of the voltage measuring device. In addition, since high voltage is not generated inside the voltage measuring instrument, high insulation design and measures against electric shock are not necessary. Therefore, the cost increase as in the prior art can be prevented, and the voltage measuring instrument can be configured inexpensively.

  Next, an embodiment of a voltage measuring device using the above measurement principle will be described. FIG. 2 is a diagram showing the configuration of the first embodiment of the voltage measuring device 100 of the present invention.

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

  The voltage measuring instrument 100 according to the first embodiment includes an electrode 101, a current detection unit 120, a difference extraction unit 130, a constant voltage variable frequency sine wave oscillation unit 104, a frequency measurement unit 150, and an operation unit 160.

  The electrode 101 is attached to the coated wire 300. Therefore, the conductor 310 and the electrode 101 are not in contact with each other, and an unknown parasitic capacitance C1 exists between the conductor 310 and the electrode 101.

  The current detection unit 120 includes a resistor R121 and an instrumentation amplifier 122 that detects a voltage generated in the resistor R121.

  The difference extraction unit 130 smoothes the signal of the frequency fx that has passed through the first filter unit 131 that passes the signal of the frequency fx, the second filter unit 132 that passes the variable signal band of the frequency fs, and the first filter unit 131. A first alternating current to direct current conversion unit 133 for converting into direct current, a second alternating current to direct current conversion unit 134, and a first alternating current to direct current conversion unit 133 for smoothing the signal of frequency fs passed through the second filter unit 132 and converting it into direct current. The differential amplifier 135 extracts the difference between the signal Vrx corresponding to the magnitude of the current Ix output by the second AC and the signal Vrs corresponding to the magnitude of the current Is output from the second AC-DC converter 134.

  The constant voltage variable frequency sine wave oscillation unit 104 is a circuit that outputs a sine wave of a frequency according to the voltage signal output from the difference extraction unit 130 as the fixed voltage Vs, and a voltage controlled oscillator (voltage controlled oscillator), a voltage frequency A converter (Voltage to Frequency Converter) or the like can be used. The constant voltage variable frequency sine wave oscillation unit 104 functions as a frequency adjustment unit 140 and a variable frequency oscillation unit 110.

  The constant voltage variable frequency sine wave oscillation unit 104 raises the output frequency when Vrx> Vrs. This causes Is to increase and Vrs to increase. On the other hand, when Vrx <Vrs, the output frequency is lowered. This reduces Is and reduces Vrs.

  Frequency measurement unit 150 measures the output frequency fs of constant voltage variable frequency sine wave oscillation unit 104, operation unit 160 calculates voltage Vx based on the measurement result of frequency fs in frequency measurement unit 150, and as the measurement result Output.

  The frequency measurement unit 150 can use various methods. For example, a method of measuring the number of times the input signal crosses the reference voltage at a constant measurement time, a method of measuring the time (period) of crossing the input signal and the reference voltage, or the like can be used.

したがって、

となる。 In the first embodiment, since the resistor R121 is used for the current detection unit 120, the above [Equation 3] [number] is taken into consideration in consideration of the voltage drop Vrx due to the current Ix generated by the resistor R121 and the voltage drop Vrs due to the current Is. In addition to 4], [Equation 8] [Equation 9] is obtained.

Therefore,

It becomes.

が得られる。−Ｖｒ^２は小さいので無視すると、

となる。さらに、抵抗Ｒ１２１が、容量Ｃ１と周波数ｆｓとで決まるリアクタンスよりも十分小さければ、Ｖｒ^２を無視することができる。このため、電流検出用の抵抗Ｒ１２１を小さい値とすることで、Ｖｘ＝Ｖｓ×ｆｓ／ｆｘが得られることになる。したがって、演算部１６０は、周波数測定部１５０の測定結果ｆｓを（Ｖｓ／ｆｘ）倍する演算を行なうことで、測定対象電圧Ｖｘを算出し、出力することができる。もちろん、Ｖｒ（ＶｒｓあるいはＶｒｘ）を別途測定し、［数１２］にしたがって、測定対象電圧Ｖｘを算出し、出力してもよい。 Here, since the frequency fs is adjusted by the difference extraction unit 130 and the constant voltage variable frequency sine wave oscillation unit 104 so that Ix = Is, Vrx and Vrs become equal, and let this be Vr,

Is obtained. -If Vr ² is small, ignore it.

It becomes. Furthermore, the resistance R121 is sufficiently smaller than the reactance determined by the capacitance C1 and the frequency fs, it is possible to ignore the Vr ^2. Therefore, Vx = Vs × fs / fx can be obtained by setting the current detection resistor R121 to a small value. Therefore, the calculation unit 160 can calculate and output the measurement target voltage Vx by performing calculation to multiply the measurement result fs of the frequency measurement unit 150 by (Vs / fx). Of course, Vr (Vrs or Vrx) may be separately measured, and the voltage Vx to be measured may be calculated and output according to [Equation 12].

  The current detection unit 120 is configured of the resistor R 121 and the instrumentation amplifier 122. However, the present invention is not limited to this configuration, and various methods capable of acquiring a signal according to the current can be adopted. For example, a Hall sensor, a current transformer circuit or the like may be used to detect a magnetic field due to current, and a voltage proportional to the current may be output. Also, instead of the resistor R121, a capacitor, a coil, or a combination of these may be used.

  In addition, as the first filter unit 131 and the second filter unit 132, an active band pass filter of VCVS (salen key) type, multiple feedback type, state variable type, passive band pass filter LC band pass filter, RLC band pass Various systems such as filters can be used.

  The second filter unit 132 needs to cover the variable range of the variable frequency fs as a transmission band. For this reason, a case may occur in which noise other than the frequency fs is transmitted. Therefore, the cutoff frequency may be set according to the output frequency of the constant voltage variable frequency sine wave oscillation unit 104.

  In this case, for example, the second filter unit 132 may be configured as a switched capacitor filter, and a signal of a frequency obtained by multiplying the output of the constant voltage variable frequency sine wave oscillating unit 104 by N times by PLL may be input as the clock. . As a result, the cutoff frequency can be set to 1 / n of the frequency fs, and noise mixing can be suppressed.

  Also, as the first alternating current to direct current conversion unit 133 and the second alternating current to direct current conversion unit 134, various kinds such as RMS to DC converter (effective value detection), average value detection of full wave average or half wave average, peak hold circuit, etc. The following scheme 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 difference extraction unit 130 is configured using a synchronous detection circuit. The synchronous detection circuit is a circuit that converts the magnitude of a signal having the same frequency component as the reference signal among the input signals into a DC voltage and outputs the DC voltage.

  In the example of this figure, the DC voltage Vrx corresponding to the magnitude of the signal of the frequency fx is obtained from the output signal of the current detection unit 120 using the first synchronous detection unit 136, and the second synchronous detection unit 137 is used. A DC voltage Vrs corresponding to the magnitude of the signal of frequency fs is obtained. The voltage measuring device 100 of the second embodiment includes a sine wave oscillator 138 of frequency fx for the reference signal of the first synchronous detection unit 136. The reference signal of the second synchronous detection unit 137 uses the output signal of the constant voltage variable frequency sine wave oscillation unit 104 of 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 digital signal processing unit 170 is provided, and processing other than the current detection unit 120 configured by the resistor R 121 and the instrumentation amplifier 122 is performed by digital signal processing.

  For this reason, an A / D conversion unit 177 for converting an output signal of the current detection unit 120 into digital data is provided. The A / D conversion unit 177 can use various methods such as a flash type, successive approximation type, integral type, and delta sigma type.

  The digital signal processing unit 170 separates a signal of frequency fx and extracts Vrx, a frequency separator (fx) 172 which separates signals of frequency fs and extracts Vrs, and Vrx And Vrs, and the level comparison unit 173 that changes the frequency control value based on the comparison result, the digital direct synthesis oscillator 175 that outputs an analog sine wave of the voltage Vs and the frequency fs, and the output of the digital direct synthesis oscillator 175 An arithmetic unit 176 is provided which calculates and outputs the voltage Vx to be measured by performing an operation of multiplying the frequency fs by (Vs / fx).

  The frequency separators 171 and 172 and the level comparison unit 173 function as the difference extraction unit 130. The digital direct synthesis oscillator 175 functions as a variable frequency oscillation unit 110, a frequency adjustment unit 140, and a frequency measurement unit 150.

  The frequency separators 171 and 172 can be configured using a digital filter or a synchronous detection circuit. The frequency separator (fs) 172 may adjust the transmission frequency band based on the frequency control value of the level comparison unit 173 or the output frequency fs of the digital direct synthesis oscillator 175.

  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 even when the exact frequency of the object to be measured is not known. Although it demonstrates based on the structure of 1st Example, you may apply to another Example.

  In the fourth embodiment, the frequency measuring unit 180 is used to measure the frequency of the signal that has passed through the first filter unit 131 to obtain the accurate frequency fx of the measurement target. The calculation unit calculates the voltage Vx to be measured by multiplying the measurement frequency fs of the frequency measurement unit 150 by (Vs / fx). fx uses the measurement value of the frequency measurement unit 180. The first filter unit 131 uses a filter that includes the approximate frequency to be measured in the pass band.

  The frequency measuring unit 180 can use various methods as the frequency measuring unit 150 does. For example, a method of measuring the number of times the input signal crosses the reference voltage at a constant measurement time, a method of measuring the time (period) of crossing the input signal and the reference voltage, or 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 voltage can be measured not only in contact with the object to be measured but also in contact. Although it demonstrates based on the structure of 1st Example, you may apply to another Example.

  In the voltage measuring instrument 100 of the fifth embodiment, an actual capacitor 102 is connected between the electrode 101 and the current detection unit 120. Therefore, even in the state where the electrode 101 is in contact with the conducting wire 330, the capacitor 102 plays a role of the capacitance C1, so that the voltage Vx to be measured can be measured. In addition, when measuring the coated wire 300, since the parasitic capacitance and the combined capacitance of the capacitor 102 play a role of the capacitance C1, the voltage Vx to be measured can be measured. That is, the voltage Vx to be measured can be measured without contact or with contact.

Reference Signs List 100 voltage measuring instrument 101 electrode 102 capacitor 104 constant voltage variable frequency sine wave oscillation unit 110 variable frequency oscillation unit 120 current detection unit 121 resistance R
122 instrumentation amplifier 130 difference extraction unit 131 first filter unit 132 second filter unit 133 first AC-DC converter 134 second AC-DC converter 135 differential amplifier 136 first synchronous detector 137 second synchronous detector 138 Sine Wave Oscillator 140 Frequency Adjustment Unit 150 Frequency Measurement Unit 160 Operation Unit 170 Digital Signal Processing Unit 171 Frequency Separator 172 Frequency Separator 173 Level Comparison Unit 175 Digital Direct Combining Oscillator 176 Operation Unit 177 A / D Conversion Unit 180 Frequency Measurement Unit 300 coated wire 310 conductor 320 insulation coating 330 conductor

Claims (3)

A voltage measuring device for measuring an alternating voltage at a first frequency, the voltage measuring device comprising:
An electrode,
A variable frequency oscillating unit connected to the electrode and outputting an AC signal of a second frequency fixed at a first voltage;
A current detection unit that detects a current flowing between the electrode and the variable frequency oscillation unit;
A difference extraction unit that extracts and outputs a value corresponding to the difference between the magnitude of the first frequency component and the magnitude of the second frequency component from the detected current;
A frequency adjustment unit that changes a second frequency of the variable frequency oscillation unit such that an output of the difference extraction unit becomes 0;
An arithmetic unit that calculates an alternating current voltage of the first frequency based on the first voltage, the first frequency, and the second frequency;
A voltage measuring apparatus comprising:   The voltage measurement according to claim 1, wherein the calculation unit calculates an AC voltage at the first frequency by multiplying the second frequency by a value obtained by dividing the first voltage by the first frequency. apparatus. A voltage measurement method for measuring an AC voltage of a first frequency, comprising:
Regarding the current flowing through the capacitance when the alternating voltage of the second frequency fixed at the first voltage is applied to the object to be measured to which the alternating voltage of the first frequency is applied,
Adjusting the second frequency such that the magnitude of the first frequency component and the magnitude of the second frequency component are the same;
An alternating voltage of the first frequency is calculated based on the first voltage, the first frequency, and the second frequency at that time.

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