JP6845732B2 - Voltage measuring device, voltage measuring method - Google Patents

Description

The present invention relates to a voltage measuring device and a voltage measuring method capable of measuring the voltage of an object to be measured in a non-contact manner.

Patent Document 1 discloses a voltage measuring device 400 capable of measuring the voltage V1 of the measurement object 404 in a non-contact manner as shown in FIG. 7. In the voltage measuring device 400, the detection electrode 412 of the probe unit 402 is arranged 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. Has been done.

In the voltage measuring device 400, when the variable capacitance element 413 is driven by the AC signal S1 from the main body 403, 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 object to be measured 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 an 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, and at this time, the shield voltage V4 becomes the same voltage as the voltage V1 of the measurement object 404. Therefore, the voltage V1 of the object to be measured 404 can be measured by measuring the shield voltage V4 with the voltmeter 426.

JP-A-2007-132926

In the voltage measuring device 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, it is necessary to design a high insulation around the shield case and take measures to prevent electric shock due to damage. Therefore, the cost of the voltage measuring device 400 is increased.

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

In order to solve the above problems, the voltage measuring device according to the first aspect of the present invention is a voltage measuring device that measures an AC voltage of a first frequency, and is connected to an electrode and the electrode to use a first voltage. A variable frequency oscillating unit that outputs a fixed second frequency AC signal, a current detecting unit that detects a current flowing between the electrode and the variable frequency oscillating unit, and the first frequency from the detected current. The difference extraction unit that extracts and outputs a value corresponding to the difference between the size of the component and the size of the second frequency component, and the variable frequency oscillation unit so that the output of the difference extraction unit becomes 0. It is characterized by including a frequency adjusting unit that changes two frequencies and a calculation unit that calculates an AC voltage of the first frequency based on the first voltage, the first frequency, and the second frequency. To do.
Here, the calculation unit can calculate the AC voltage of the first frequency by multiplying the value obtained by dividing the first voltage by the first frequency by the second frequency.
Further, the electrode and the variable frequency oscillator may be connected via a capacitor.
Further, the variable frequency oscillator may be capable of switching the value of the first voltage.
In order to solve the above problems, the voltage measuring method according to the second aspect of the present invention is a voltage measuring method for measuring the AC voltage of the first frequency, and is a measurement target to which the AC voltage of the first frequency is applied. Regarding the current flowing through the capacitance when an AC voltage of the second frequency fixed by the first voltage is applied to the object, the magnitude of the first frequency component and the magnitude of the second frequency component are The second frequency is adjusted in the same manner, and the 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 non-contact measurement of a high voltage without incurring a high cost.

It is a figure explaining the measurement principle of the voltage measuring instrument of this invention. It is a figure which shows the structure of 1st Example of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 2nd Example of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 3rd Example of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 4th Example of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 5th Example of the voltage measuring instrument 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 diagram illustrating a measurement principle of the voltage measuring instrument of the present invention. In the voltage measuring instrument of the present invention, an AC voltage is a measurement target, and in this figure, an AC voltage Vx having a frequency fx is a measurement target. It is assumed that the frequency fx is known. The AC voltage Vx is, for example, about several hundred V to several kV.

A variable frequency oscillator 110 capable of changing the frequency fs is provided on the measurement side. The output voltage of the variable frequency oscillator 110 is fixed at the voltage Vs. A capacitance C1 exists between the measurement target and the measurement side. The capacity C1 may be unknown.

The current of the frequency fx flowing through the capacitance C1 due to the voltage Vx to be measured is defined as Ix, and the current of the frequency fs flowing through the capacitance C1 due to the voltage Vs of the variable frequency oscillator 110 is defined as Is. In reality, the current obtained by superimposing the current Ix and the current Is will flow through the capacitance 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 does not have to 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 adjusting unit 140 changes the output frequency fs of the variable frequency oscillating unit 110 so that the output of the difference extracting unit 130 becomes 0, that is, the magnitude of the current Is is equal to the magnitude of the current Ix.

The frequency measuring unit 150 measures the output frequency fs of the variable frequency oscillating unit 110. The calculation unit 160 calculates and outputs the voltage Vx to be measured based on the measurement result of the frequency fs in the frequency measurement unit 150. The output of the voltage Vx can be a 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 capacitance C1 with respect to the current Ix is Xcx and the impedance of the capacitance C1 with respect to the current Is is Xcs, the current Ix and the current Is can be expressed as follows.

here,

Therefore, [Equation 5] is obtained.

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

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

Therefore, the calculation unit 160 multiplies the fixed value obtained by dividing the known fixed output voltage Vs of the variable frequency oscillation unit 110 by the known fixed frequency fx of the AC voltage to be measured by the measured value fs of the frequency measurement unit 150. By performing the calculation, the measurement target voltage Vx 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 the commercial power supply, if the measured frequency fs is 50 kHz, the value obtained by multiplying the voltage Vs by 1000 is the voltage Vx to be measured. That is, by setting the voltage Vs to several Vs, even if the measurement target voltage is several kV, it is possible to measure with a voltage of several Vs. In this case, if the voltage Vs is 1V, the voltage Vx to be measured is measured as 1 kV.

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

For example, assuming that the variable band of the variable frequency oscillator 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 can be switched between 1V and 0.5V, the voltage Vx can be measured in the range of 0.25kV to 1kV.

As described above, in the present invention, the measuring side can measure at a voltage much lower than the voltage to be measured, so that expensive high withstand voltage components are not required for the components of the voltage measuring instrument. In addition, since high voltage is not generated inside the voltage measuring instrument, high insulation design and electric shock prevention measures are not required. Therefore, it is possible to prevent the cost increase as in the prior art, and it is possible to construct the voltage measuring instrument at low cost.

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

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

The voltage measuring device 100 of the first embodiment includes an electrode 101, a current detecting unit 120, a difference extracting unit 130, a constant voltage variable frequency sine wave oscillating unit 104, a frequency measuring unit 150, and a calculation unit 160.

The electrode 101 is attached to the covered electric 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. The first AC-DC conversion unit 133 that converts to DC, the second AC-DC conversion unit 134 that smoothes the signal of frequency fs that has passed through the second filter unit 132 and converts it to DC, and the first AC-DC conversion unit 133. A differential amplifier 135 is provided for extracting the difference between the signal Vrx corresponding to the magnitude of the current Ix output by and the signal Vrs corresponding to the magnitude of the current Is output by the second AC-DC converter 134.

The constant voltage variable frequency sine wave oscillating unit 104 is a circuit that outputs a sine wave having a frequency corresponding to the voltage signal output by the difference extraction unit 130 at a fixed voltage Vs, and is a voltage-controlled oscillator and a voltage frequency. A converter (Voltage to Frequency Converter) or the like can be used. The constant voltage variable frequency sine wave oscillating unit 104 functions as a frequency adjusting unit 140 and a variable frequency oscillating unit 110.

The constant voltage variable frequency sine wave oscillator 104 increases the output frequency when Vrx> Vrs. As a result, Is increases and Vrs increases. On the other hand, when Vrx <Vrs, the output frequency is lowered. As a result, Is decreases and Vrs decreases.

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

The frequency measuring unit 150 can use various methods. For example, a method of measuring the number of times the input signal and the reference voltage intersect in a fixed measurement time, a method of measuring the time (cycle) at which the input signal and the reference voltage intersect, and 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 voltage drop Vrx due to the current Ix and the voltage drop Vrs due to the current Is generated in the resistor R121 are taken into consideration, and the above [Equation 3] [Number] In addition to [4], [Equation 8] and [Equation 9] are obtained.

Therefore,

Will be.

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 so that Ix = Is by the difference extraction unit 130 and the constant voltage variable frequency sine wave oscillator 104, Vrx and Vrs become equal, and if this is Vr, it is assumed.

Is obtained. -Vr ² is small, so if you ignore it,

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

The current detection unit 120 is composed of the resistor R121 and the instrumentation amplifier 122, but the present invention is not limited to this configuration, and various methods capable of acquiring a signal corresponding 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 a current and output a voltage proportional to the current. Further, a capacitor, a coil, or a combination thereof may be used instead of the resistor R121.

The first filter unit 131 and the second filter unit 132 include a VCVS (salen key) type of an active bandpass filter, a multiple feedback type, a state variable type, an LC bandpass filter of a passive bandpass filter, and an RLC bandpass. Various methods such as a filter can be used.

The second filter unit 132 needs to cover the variable range of the variable frequency fs as a transmission band. Therefore, there may be a case where 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 oscillator 104.

In this case, for example, the second filter unit 132 may be configured by a switched capacitor filter, and a signal having a frequency obtained by multiplying the output of the constant voltage variable frequency sine wave oscillator 104 by N times by a PLL or the like 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.

Further, as the first AC-DC conversion unit 133 and the second AC-DC conversion unit 134, various types such as an RMS-DC converter (effective value detection), a full-wave average or half-wave average average value detection, and a peak hold circuit are used. Method can be used.

Next, a second embodiment of the voltage measuring instrument 100 of the present invention will be described with reference to FIG. In the second embodiment, the difference extraction unit 130 is configured by using a synchronous detection circuit. The synchronous detection circuit is a circuit that converts the magnitude of an input signal having the same frequency component as the reference signal into a DC voltage and outputs the signal.

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 by 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 a signal having a frequency fs is obtained. The voltage measuring instrument 100 of the second embodiment includes a sinusoidal oscillator 138 having a frequency of fx for the reference signal of the first synchronous detection unit 136. As the reference signal of the second synchronous detection unit 137, the output signal of the constant voltage variable frequency sine wave oscillation unit 104 having a frequency fs is used.

Next, a third embodiment of the voltage measuring instrument 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 composed of the resistor R121 and the instrumentation amplifier 122 is performed by digital signal processing.

Therefore, an A / D conversion unit 177 for converting the 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, a sequential comparison type, an integral type, and a delta sigma type.

The digital signal processing unit 170 includes a frequency separator (fx) 171 that separates the frequency fx signal and extracts Vrx, a frequency separator (fs) 172 that separates the frequency fs signal and extracts Vrs, and Vrx. And Vrs are compared, 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 voltage Vs and frequency fs, and the output of the digital direct synthesis oscillator 175. It is provided with a calculation unit 176 that calculates and outputs the measurement target voltage Vx by performing a calculation 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 oscillator 110, a frequency adjustment unit 140, and a frequency measurement unit 150.

The frequency separators 171 and 172 can be configured by using a digital filter or a synchronous detection circuit. The frequency separator (fs) 172 may be configured to 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 instrument 100 of the present invention will be described with reference to FIG. The fourth embodiment is a configuration that can be applied even when the exact frequency of the measurement target is not known. Although the description will be given based on the configuration of the first embodiment, it may be applied to other embodiments.

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 an accurate frequency fx to be measured. The calculation unit calculates the measurement target voltage Vx by multiplying the measurement frequency fs of the frequency measurement unit 150 by (Vs / fx). For fx, the measured value of the frequency measuring unit 180 is used. The first filter unit 131 uses a filter that includes the approximate frequency of the measurement target in the pass band.

The frequency measuring unit 180 can use various methods like the frequency measuring unit 150. For example, a method of measuring the number of times the input signal and the reference voltage intersect in a fixed measurement time, a method of measuring the time (cycle) at which the input signal and the reference voltage intersect, and the like can be used.

Next, a fifth embodiment of the voltage measuring instrument 100 of the present invention will be described with reference to FIG. The fifth embodiment has a configuration in which the voltage can be measured not only in the non-contact state with the measurement object but also in the contact state. Although the description will be given based on the configuration of the first embodiment, it may be applied to other embodiments.

In the voltage measuring instrument 100 of the fifth embodiment, an actual capacitor 102 is connected between the electrode 101 and the current detecting unit 120. Therefore, even when the electrode 101 is in contact with the lead wire 330, the capacitor 102 plays the role of the capacitance C1, so that the measurement target voltage Vx can be measured. Further, when measuring the coated electric wire 300, since the parasitic capacitance and the combined capacitance of the capacitor 102 play the role of the capacitance C1, the measurement target voltage Vx can be measured. That is, the measurement target voltage Vx can be measured both in non-contact and in contact.

100 Voltage measuring instrument 101 Electrode 102 Capacitor 104 Constant voltage variable frequency sine wave oscillator 110 Variable frequency oscillator 120 Current detector 121 Resistance R
122 Instrumentation amplifier 130 Difference extraction unit 131 1st filter unit 132 2nd filter unit 133 1st AC-DC conversion unit 134 2nd AC-DC conversion unit 135 Differential amplifier 136 1st synchronous detection unit 137 2nd synchronous detection unit 138 Sine wave oscillator 140 Frequency adjustment unit 150 Frequency measurement unit 160 Calculation unit 170 Digital signal processing unit 171 Frequency separator 172 Frequency separator 173 Level comparison unit 175 Digital direct synthesis oscillator 176 Calculation unit 177 A / D conversion unit 180 Frequency measurement unit 300 Covered wire 310 Conductor 320 Insulation coated 330 Conductor

Claims (3)

A voltage measuring device that measures the AC voltage of the first frequency.
With electrodes
A variable frequency oscillator that is connected to the electrode and outputs a second frequency AC signal fixed by the first voltage,
A current detection unit that detects the current flowing between the electrode and the variable frequency oscillation unit, and
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 adjusting unit that changes the second frequency of the variable frequency oscillating unit so that the output of the difference extracting unit becomes 0.
A calculation unit that calculates the AC voltage of the first frequency based on the first voltage, the first frequency, and the second frequency.
A voltage measuring device characterized by being equipped with. The voltage measurement according to claim 1, wherein the calculation unit calculates an AC voltage of the first frequency by multiplying the value obtained by dividing the first voltage by the first frequency by the second frequency. apparatus. It is a voltage measuring method for measuring the AC voltage of the first frequency.
Regarding the current flowing through the capacitance when the AC voltage of the second frequency fixed at the first voltage is applied to the measurement object to which the AC voltage of the first frequency is applied.
The second frequency is adjusted so that the size of the first frequency component and the size of the second frequency component are the same.
A voltage measuring method characterized in that an AC 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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