JP2017194419A - Voltage measuring device - Google Patents

Abstract

A voltage measuring apparatus capable of measuring a voltage to be measured such as a power line with high accuracy without contact is provided. A detection unit 3 that outputs a detection signal whose amplitude changes according to a potential difference between a voltage to be measured and a reference potential, a demodulation unit 4a that extracts and outputs a frequency component of the voltage to be measured from the detection signal, Based on the output signal of the demodulator 4a, a voltage generator 4b that changes and outputs a reference potential within a predetermined range, and a data processor 4c that identifies a reference potential when the potential difference becomes a predetermined value or less as a voltage to be measured. In the voltage measuring apparatus having the above, the detection unit 3 causes the current flowing through the coupling capacitance between the measurement object and the detection electrode 2 to be higher than the frequency of the voltage to be measured by turning on / off the switching elements 311 and 312. And a transformer 32 that generates the detection signal from the output thereof, and the switching elements 311 and 312 and the transformer 32 are connected in series or in parallel. [Selection] Figure 1

Description

  The present invention relates to a voltage measurement device that measures a voltage applied to a measurement target such as a power line in a non-contact state with the measurement target.

2. Description of the Related Art Conventionally, a voltage measuring apparatus that measures a voltage applied to a power line in a non-contact manner using a coupling capacitance between the core of the power line and an electrode in a detection probe is known.
In this type of voltage measuring apparatus, the coupling capacitance changes due to the positional relationship of the detection probe with respect to the power line, the material of the insulation coating of the power line, the difference in dielectric constant depending on the surrounding environment such as temperature and humidity, and this becomes a measurement error. Therefore, there is a case where the voltage of the power line cannot be measured with high accuracy.
For this reason, the prior art described in patent documents 1-3 is known as a voltage measuring device which solves the above-mentioned problem.

The voltage measuring device described in Patent Documents 1 and 2 includes a detection electrode, a variable capacitance circuit including a capacitance changing function body such as a diode and a capacitor, and a driving circuit thereof, a current detector, an amplifier circuit, a synchronous detection circuit, an integration circuit, A voltage generation circuit and the like are provided.
In these voltage measuring devices, the capacitance of the capacitance changing function body is changed, and the current flowing through the measurement target, for example, the coupling capacitance between the power line and the detection electrode, is changed according to the operating frequency of the capacitance changing function body. Has been. The current is converted into a voltage via a current detector, and a signal corresponding to the voltage of the power line is generated via a synchronous detection circuit, an amplifier circuit, an integration circuit, etc., and this signal is amplified by the voltage generation circuit. .

And, by connecting the detection electrode, capacitance change function body, current detector, and voltage generation circuit in series, the output of the voltage generation circuit is connected to the current detector side so that the current flowing through the current detector is reduced to zero. And the output voltage of the voltage generation circuit is controlled to be equal to the voltage of the power line.
According to this prior art, feedback control is performed so that the output voltage of the voltage generation circuit becomes equal to the voltage to be measured, so that it is possible to suppress the influence when the coupling capacitance between the measurement target and the detection electrode varies.

  In the voltage measuring device described in Patent Document 3, the voltage generation circuit generates a reference potential signal that gradually changes from a preset minimum voltage value to a maximum voltage value, and the voltage of the power line and the reference potential are generated from the probe unit. A detection signal whose amplitude changes according to the potential difference from the signal is output, and the voltage of the reference potential signal when the potential difference becomes zero is detected as the voltage of the power line.

JP 2007-163415 A (paragraphs [0036] to [0054], FIG. 1, etc.) JP 2009-162608 A (paragraphs [0037] to [0051], FIG. 1, etc.) JP 2008-14644 (paragraphs [0018] to [0033], FIG. 1, etc.)

In the voltage measuring devices according to Patent Documents 1 and 2, this voltage is matched with the voltage of the power line by controlling the output voltage of the voltage generation circuit fed back to the current detector side. However, because feedback control has a characteristic that a deviation based on proportional control occurs, the output voltage of the voltage generation circuit cannot be completely matched with the power line voltage, and as a result, the power line voltage is measured with high accuracy. I couldn't.
On the other hand, since the voltage measurement device according to Patent Document 3 does not perform feedback control, a measurement error due to deviation due to feedback control does not occur.

  However, in the voltage measuring devices according to Patent Documents 1 to 3, since the capacitance changing function body that changes the impedance in order to modulate the detection signal is connected in series between the detection electrode and the current detector, the capacitance change The drive signal (drive current) of the functional body may be detected as a noise component by the current detector, which may affect the measurement accuracy. As a countermeasure, in these voltage measuring devices, the capacitance changing function body is configured by a bridge made of a diode or the like so that the drive signal component is not detected by the current detector, but the equilibrium state of the bridge is strictly controlled. There is a risk that manufacturing or adjustment costs may increase.

  Therefore, a problem to be solved by the present invention is to provide a voltage measuring apparatus that can measure a voltage to be measured such as a power line with high accuracy at low cost.

In order to solve the above-mentioned problem, the invention according to claim 1 is a voltage measuring device that measures a voltage to be measured applied to a measurement object in a non-contact state with respect to the measurement object. A detection unit that outputs a detection signal whose amplitude changes according to a potential difference between the detection unit, a demodulation unit that extracts and outputs a frequency component of the voltage to be measured from the detection signal, and an output signal of the demodulation unit is input in advance. A voltage generation unit that outputs the reference potential by changing the reference potential within a predetermined voltage range that is set, and a data processing unit that identifies the reference potential as the voltage to be measured when the potential difference becomes a predetermined value or less. Voltage measuring device,
The detector is
A modulation circuit that modulates a current flowing through a coupling capacitor between the measurement object and the detection electrode to a frequency higher than the frequency of the voltage to be measured by turning on / off a switching element, and the detection signal from the output of the modulation circuit And a switching circuit and the current detection circuit connected in series.

The invention according to claim 2 is a voltage measurement device that measures a voltage to be measured applied to a measurement object in a non-contact state with respect to the measurement object, and the amplitude is in accordance with a potential difference between the voltage to be measured and a reference potential. A detection unit that outputs a detection signal that changes, a demodulation unit that extracts and outputs a frequency component of the voltage to be measured from the detection signal, and a predetermined voltage range that is set in advance by receiving the output signal of the demodulation unit A voltage measuring device comprising: a voltage generating unit that changes and outputs the reference potential; and a data processing unit that identifies the reference potential as the measured voltage when the potential difference falls below a predetermined value. ,
The detector is
A modulation circuit that modulates a current flowing through a coupling capacitor between the measurement object and the detection electrode to a frequency higher than the frequency of the voltage to be measured by turning on / off a switching element, and the detection signal from the output of the modulation circuit And a switching circuit and the current detection circuit connected in parallel.

  According to a third aspect of the present invention, in the voltage measuring device according to the first or second aspect, the current detection circuit includes a primary winding excited by a current flowing through the switching element, and a second winding connected to the demodulation unit. A transformer having a next winding.

  According to a fourth aspect of the present invention, in the voltage measuring device according to any one of the first to third aspects, the voltage generation unit boosts the signal voltage input to the primary winding from the demodulation unit, and boosts the voltage. A step-up transformer that outputs the subsequent voltage as the reference potential from the secondary winding is provided.

  According to a fifth aspect of the present invention, in the voltage measuring device according to any one of the first to fourth aspects, a MOSFET is used as the switching element.

According to the present invention, since a measurement error due to a deviation that occurs during feedback control does not occur, a voltage to be measured such as a power line can be measured with high accuracy.
In addition, since the detection signal is modulated by turning on / off the switching element instead of the capacitance change function body configured by the bridge circuit, manufacturing or adjustment without requiring strict management of the bridge equilibrium state The above cost can be reduced.
Furthermore, the reference potential can be set over a wide range simply by changing the turns ratio of the step-up transformer in the voltage generation unit, and it is possible to accurately measure various voltages to be measured.

It is a lineblock diagram of the voltage measuring device concerning a 1st embodiment of the present invention. It is a specific block diagram of the modulation circuit in each embodiment of the present invention. Voltage v ₁ of the power line in the first embodiment of the present _invention, is a waveform diagram of the analog signal S ₅ and the reference potential signal S _7. It is a block diagram of the detection part in 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a voltage measuring apparatus according to a first embodiment of the present invention.
This voltage measuring device includes a detection electrode 2 and a measuring device main body 5 and measures an AC voltage v ₁ applied to a core wire 1 a of a power line 1 by a system power supply G in a non-contact manner. C ₀ indicates a coupling capacitance formed between the core wire 1 a and the detection electrode 2 when the detection electrode 2 is attached to the power line 1. Here, the detection electrode 2 is configured to be tightly wound around the outer peripheral surface of the power line 1.
Hereinafter, the voltage (measured voltage) v ₁ of the core wire 1 a is described as being synonymous with “voltage of the power line 1”.

The measurement apparatus main body 5 includes a detection unit 3 that functions as a sensor together with the detection electrode 2, and a measurement unit 4 that processes an output signal of the detection unit 3, and the detection unit 3 is a modulation circuit 31 connected to the detection electrode 2. And an insulating transformer 32 as a current detection circuit.
The modulation circuit 31 includes two switching elements 311 and 312 connected in series in opposite directions between the detection electrode 2 and the primary winding of the transformer 32, and a drive circuit that drives the switching elements 311 and 312. And a transformer 313.

FIG. 2 is a detailed circuit diagram of the modulation circuit 31. In the modulation circuit 31, n-type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are used as the switching elements 311 and 312. Reference numeral 314 denotes a resistor connected in parallel to the secondary winding of the transformer 313.
The n-type MOSFET is turned on when the drive signal S ₁ applied to the primary winding of the transformer 313 is at “High” level, but the input signal from the core line 1 a of the power line 1 is a signal of both positive and negative polarity. The two n-type MOSFETs have their source terminals connected to each other, and a current flows through a reverse-biased MOSFET side via a built-in body diode.

Returning to FIG. 1, the oscillation circuit 40 in the demodulation unit 4 a provided in the measurement unit 4 is connected to the primary side of the transformer 313. The oscillation circuit 40 outputs, for example, a rectangular-wave drive signal S ₁ having a frequency (several hundreds [kHz] to several [MHz]) sufficiently higher than the voltage v _{1 of a} commercial frequency (50 or 60 [Hz]), The switching elements 311 and 312 are turned on / off via the transformer 313.

For this reason, the current flowing through the switching elements 311 and 312 via the coupling capacitor C ₀ is modulated by the frequency of the drive signal S ₁ . Thus, in proportion to the magnitude of the current flowing through the switching element 311 and 312, and the detection signal S ₂ of the high frequency is transmitted to the measuring unit 4 via the transformer 32, in the measuring section 4, the voltage of the power line 1 v ₁ of the commercial frequency component is demodulated and amplified.
One end of the primary winding of the transformer 32 is connected to the switching element 312 and the other end of the primary winding is connected to the output side of the step-up transformer 45 in the voltage generator 4b described later.

  The measurement unit 4 includes a demodulation unit 4a, a voltage generation unit 4b, and a data processing unit 4c. The demodulation unit 4a includes a detection circuit 41, an amplification circuit 42, and a filter circuit 43 in addition to the oscillation circuit 40 described above. .

Detection circuit 41 at a timing transformer 32 in synchronization with the driving signals S ₁ from the oscillation circuit 40 is energized, and detects the detection signal S ₂ example envelope. Analog signal S ₃ after detection is amplified by a preset appropriate amplification factor by the amplifier circuit 42, it is output as the detection signal S _4.

The filter circuit 43 passes only the commercial frequency component of the voltage v ₁ by filtering the frequency component of the detection signal S ₄ . Here, the detection unit 3 detects the voltage v ₁ by turning on / off the switching elements 311 and 312, and the phase of the detection signal S ₄ is advanced by 90 ° from the phase of the voltage v ₁ . For this reason, as a configuration of the filter circuit 43, for example, after passing through a secondary active low-pass (high frequency band removal) filter, passing through a primary high-pass (low frequency band removal) filter, the voltage v ₁ is obtained. It generates an analog signal S ₅ the combined phases.

Next, the voltage generation unit 4 b includes a voltage generation circuit 44, a step-up transformer 45, and a voltage dividing circuit 46.
Voltage generating circuit 44 gradually increases the voltage value in the range up to a maximum voltage value from the predetermined minimum voltage value, the reference signal S ₆ repeating decreasing, generated based on the analog signal S _5. In this embodiment, the voltage generating circuit 44 generates a reference signal S ₆ having a predetermined amplitude and frequency. Note that the voltage generation circuit 44 may generate an AC signal having a continuous waveform having a predetermined shape, such as a triangular wave signal or a sawtooth wave signal.

The step-up transformer 45 is an insulating transformer, and there is a relationship of n ₂ > n ₁ between the number of turns n ₁ of the primary winding and the number of turns n ₂ of the secondary winding. Primary winding and secondary winding of the step-up transformer 45, one ends are commonly connected to the other end of the primary winding, the reference signal S ₆ is applied from the voltage generating circuit 44. Thus, the step-up transformer 45 boosts the reference signal S ₆ which is applied to the primary winding, the positive peak value (maximum voltage value) + V _a [V], the negative peak value (minimum voltage value) There -V _a reference sine wave signal of amplitude 2V _a a [V] voltage signal S _{7 (a} voltage that the V _r, see also referred to the potential V _r in the following) and outputs from the other end of the secondary winding . The reference potential signal S ₇ is applied to the subsequent voltage dividing circuit 46 and the other end of the primary winding of the transformer 32 in the detection unit 3.
Voltage divider circuit 46, the reference potential V _r, and outputs a voltage signal S ₈ are divided by a preset division ratio.

The voltage signal S ₈ output an analog signal S ₅ output from the aforementioned filter circuit 43 from the voltage dividing circuit 46 are input to the data processing unit 4c, by the data processing unit 4c, the voltage of the power line 1 v ₁ data processing for obtaining the runs.
Hereinafter, the measurement operation of the voltage v ₁ in the present embodiment will be described together with the configuration and operation of the data processing unit 4 c.

First, when measuring the voltage v ₁ , the coupling electrode C ₀ is formed between the core wire 1 a and the detection electrode 2 by attaching the detection electrode 2 to the core wire 1 a of the power line 1 in a non-contact state.
Then, the activation state of the measurement unit 4, the voltage generating unit 4b, the voltage generating circuit 44 starts the generation of the reference signal S _6, the reference potential V _r of the step-up transformer 45 is obtained by boosting the reference signal S ₆ The voltage is applied to the primary winding of the transformer 32 in the detection unit 3. Further, the voltage generating unit 4b, and the voltage signal S ₈ to the voltage divider circuit 46 is obtained by dividing the reference voltage V _r min, and outputs to the sample-and-hold circuit 49 of the data processing unit 4c.

On the other hand, the demodulation unit 4a, the oscillation circuit 40 is output to the modulation circuit 31 generates a driving signal S _1. Trans 313 of the modulation circuit 31 outputs an ON / OFF signal (pulse signal) from the secondary side on the basis of the drive signals S ₁ input to the primary side, thereby the switching elements 311, 312 on / off.

At this time, the primary winding of the transformer 32 is excited when the switching elements 311 and 312 are turned on, and a detection signal S ₂ having a phase advanced by 90 ° with respect to the voltage v ₁ of the power line 1 is output from the secondary winding. Is done. Further, when the switching elements 311 and 312 are off, the primary winding of the transformer 32 is in a non-excited state, and as a result, the transformer 32 is reverse-excited and inverted by 90 ° phase with respect to the voltage v ₁ of the power line 1. signal _{S 2} is outputted.

Detection circuit 41, the detection signal S ₂ output by detecting for example the envelope from the transformer 32, the analog signal S ₃ after detection is the detection signal S ₄ is amplified by the amplifier circuit 42. Accordingly, the detection signal S ₂ from the frequency of the driving signals S ₁ can be demodulated as signals behave independently.

The detection signal S ₄ amplified by the amplifier circuit 42 includes high-frequency noise that is generated when the switching elements 311 and 312 are turned on / off due to the influence of the leakage inductance of the transformer 32.
Therefore, as described above, if the filter circuit 43 is composed of a secondary active low-pass filter and a primary high-pass filter, high-frequency noise can be removed and only the commercial frequency band is allowed to pass through the filter circuit 43 as a whole. By configuring the band-pass filter, an analog signal (a signal having the same phase as the voltage v ₁ of the power line 1) S ₅ having a phase delayed by 90 ° from the detection signal S ₂ can be obtained.

FIG. 3 is a waveform diagram showing the voltage v ₁ , the analog signal S _5, and the reference potential signal S ₇ (reference potential V _r ) of the power line 1. Since the frequency of the voltage v ₁ is extremely lower than the frequencies of the analog signal S ₅ and the reference potential signal S ₇ , the waveform of the voltage v ₁ is shown in a substantially linear shape in FIG.

If caught reference potential signal S ₇ as a voltage v ₁ and signal combined time axis, the analog signal S ₅ output from the filter circuit 43 is synchronized with the voltage v _1, and in proportion to the voltage v ₁ change Signal. The A / D conversion circuit 47 in FIG. 1 converts the analog signal S ₅ into digital data D ₁ and outputs it to the control circuit 48.
The control circuit 48 repeatedly executes the zero detection process of the input data. The zero detection process, based on the digital data D ₁ input, as shown in FIG. 3, the voltage value of the analog signal S ₅ detects a 0 [V] to become timing (zero-cross timing) t _z.

A / D conversion circuit 47, because it has generally the sampling period, strictly speaking, the digital data can not be confirmed zero crossing of the analog signal S _5, which is input to approximately, to the control circuit 48 practically be detected zero-cross timing t _z on the basis of the polarity of the D ₁ is inverted, no problem. The reason is that the voltage v ₁ of the power line 1 is in the commercial frequency band, whereas the sampling frequency of the A / D conversion circuit 47 can be set to a sufficiently high frequency such as 100 [kHz].

When the control circuit 48 detects the zero-cross timing t _z, it generates a trigger signal S ₉ in synchronism with the timing t _z, and outputs the sample-and-hold circuit 49. In this case, since the digital data _{D 1} is a value based on the potential difference _(v 1 -V _r), the control circuit 48 detects the zero-cross timing _{t z is, (v} 1 -V _r) is 0 [V], That is, the timing at which the reference potential V _r matches the voltage v ₁ of the power line 1 is detected. Thereby, the zero cross detection process is completed.

The sample hold circuit 49 holds the voltage value of the voltage signal S ₈ in synchronization with the trigger signal S ₉ output from the control circuit 48 and outputs data D ₂ indicating this voltage value to the control circuit 48. The control circuit 48, when the data D ₂ is inputted from the sample hold circuit 49 after performing the zero-cross detection processing is performed a voltage calculation process. In this voltage calculation process, the control circuit 48 calculates the reference potential V _r based on the input data D ₂ and the voltage dividing ratio by the voltage dividing circuit 46 of the voltage generating unit 4 b, and uses the value as the voltage v of the power line 1. Identified as ₁ .

Thus, in the voltage measuring device according to the present embodiment, the voltage generator 4b is within a predetermined voltage range (the voltage range of −V _a [V] to + V _a [V]) including the voltage v ₁ of the power line 1. The reference potential V _r is changed, and the reference potential V when the analog signal S ₅ indicating the potential difference (v ₁ −V _r ) detected by the control circuit 48 based on the detection signal S ₂ becomes 0 [V]. _r is calculated as the voltage v ₁ of the power line 1.
According to this voltage measurement device, it is possible to reduce measurement errors caused by deviations caused by feedback control, and as a result, it is possible to measure the voltage v ₁ of the power line ₁ with high accuracy. In addition, as described in Patent Documents 1 to 3, by not using a bridge configuration capacity change function body, it is not necessary to manage the equilibrium state of the bridge, and there is no risk of increasing manufacturing or adjustment costs. .

Further, since the obtained reference potential V _r by boosting the reference signal S ₆ the step-up transformer 45 which is generated by the voltage generating circuit 44, the output of only the reference potential V _r to change the turns ratio of the step-up transformer 45 The range can be changed. Therefore, it is possible to freely set the measurement range for various voltages to be measured, and as a result, it is possible to accurately measure a wide range of voltages.

Next, FIG. 4 is a configuration diagram of a detection unit in the second embodiment of the present invention.
In the detection unit 3A of the present embodiment, a series circuit of switching elements 311 and 312 is connected in parallel to a series circuit of a primary winding of a transformer 32 serving as a current detection circuit and a resistor 315. Other configurations are the same as those of the detection unit 3 in the first embodiment.
According to this embodiment, since the transformer 32 is energized when the switching element 311 and 312 is off, the detection signal by setting the detection timing based on a signal obtained by inverting the drive signals S ₁ In the detection circuit 41 detection of S ₂ is possible.

  The voltage measuring device of the present invention may be used alone, or a power measuring device can be configured by combining this voltage measuring device and a known current measuring device.

G: System power supply 1: Power line 1a: Core wire 2: Detection electrode 3, 3A: Detection unit 31: Modulation circuit 311, 312: Switching element 313: Transformer (drive circuit)
314, 315: resistor 32: transformer (current detection circuit)
4: Measurement unit 4a: Demodulation unit 4b: Voltage generation unit 4c: Data processing unit 40: Oscillation circuit 41: Detection circuit 42: Amplification circuit 43: Filter circuit 44: Voltage generation circuit 45: Step-up transformer 46: Voltage division circuit 47: A / D conversion circuit 48: control circuit 49: sample hold circuit 5: measuring device main body

Claims (5)

A voltage measurement device that measures a voltage to be measured applied to a measurement object in a non-contact state with the measurement object, and detects a detection signal whose amplitude changes according to a potential difference between the voltage to be measured and a reference potential And a demodulator that extracts and outputs a frequency component of the voltage to be measured from the detection signal, and an output signal of the demodulator is input, and the reference potential is changed within a predetermined voltage range set in advance. A voltage measuring device comprising: a voltage generating unit that outputs; and a data processing unit that identifies the reference potential as the voltage to be measured when the potential difference becomes a predetermined value or less,
The detector is
A modulation circuit that modulates a current flowing through a coupling capacitor between the measurement object and the detection electrode to a frequency higher than the frequency of the voltage to be measured by turning on / off a switching element, and the detection signal from the output of the modulation circuit And a current detection circuit for generating
The voltage measuring device, wherein the switching element and the current detection circuit are connected in series. A voltage measurement device that measures a voltage to be measured applied to a measurement object in a non-contact state with the measurement object, and detects a detection signal whose amplitude changes according to a potential difference between the voltage to be measured and a reference potential And a demodulator that extracts and outputs a frequency component of the voltage to be measured from the detection signal, and an output signal of the demodulator is input, and the reference potential is changed within a predetermined voltage range set in advance. A voltage measuring device comprising: a voltage generating unit that outputs; and a data processing unit that identifies the reference potential as the voltage to be measured when the potential difference becomes a predetermined value or less,
The detector is
A modulation circuit that modulates a current flowing through a coupling capacitor between the measurement object and the detection electrode to a frequency higher than the frequency of the voltage to be measured by turning on / off a switching element, and the detection signal from the output of the modulation circuit And a current detection circuit for generating
A voltage measuring apparatus, wherein the switching element and the current detection circuit are connected in parallel. In the voltage measuring device according to claim 1 or 2,
The voltage measuring device, wherein the current detection circuit is a transformer having a primary winding excited by a current flowing through the switching element and a secondary winding connected to the demodulator. In the voltage measuring device according to any one of claims 1 to 3,
The voltage generator includes a step-up transformer that boosts the signal voltage input to the primary winding from the demodulator and outputs the boosted voltage from the secondary winding as the reference potential. measuring device. In the voltage measuring device according to any one of claims 1 to 4,
A voltage measuring apparatus using a MOSFET as the switching element.

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