JPH0980105A - Clamp sensor connection determination method - Google Patents

Abstract

(57) An object of the present invention is to make it possible to accurately determine the correctness of the connection state of the clamp sensor with respect to the measured electric circuit without being affected by noise and waveform distortion even though the configuration is simple. SOLUTION: When grasping a measured electric circuit with a clamp sensor to detect a current, the connection determination of the clamp sensor is judged from the relationship between the current phase and the voltage phase of the clamp sensor for correctness of the connection direction with respect to the measured electric circuit. In the method, a voltage input unit 10 to which a voltage signal is input, a first fundamental wave output unit 30 that extracts and outputs the fundamental wave from the voltage signal, and a current signal converted into a voltage by a clamp sensor and detected. The input current input unit 20 and the second fundamental wave output unit 40 that extracts and outputs the fundamental wave from the same current signal, and the first and second fundamental wave output units 30 and 4
And a multiplying unit 50 that calculates active power by multiplying each fundamental wave output from 0. When active power ≧ 0, the connection state of the clamp sensor to the measured electric circuit is set to “positive”, and in other cases Determines that the connection state of the clamp sensor to the measured electric circuit is "erroneous".

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a wire connection of a clamp sensor, and more specifically, when measuring active power and the like using a clamp sensor and a voltage sensor, the relationship between the current phase and the voltage phase is measured. The present invention relates to a connection determination method for a clamp sensor, which determines whether the clamp sensor is correct or incorrect in a connection direction with respect to a measured electric circuit.

[0002]

2. Description of the Related Art A clamp sensor has a clamp portion composed of a pair of openable and closable magnetic cores, and by opening (opening) and inserting (grasping) the measured electric circuit into the magnetic core, the clamp sensor remains in a live state. It is known as a kind of voltage output type current sensor capable of detecting the current.

When this clamp sensor is connected (wired) to a single-phase two-wire live wire circuit by opening the magnetic core as described above, if the clamps are connected to the hot wire circuit in the opposite direction, the clamp will be clamped. The phase of the output of the sensor is + 180 ° with respect to the voltage of the live line electric circuit. Therefore,
For example, in measurements in which phase is a problem, such as power measurement and harmonic measurement, incorrect connection of clamps directly affects the measurement result.

Therefore, conventionally, the configuration shown in FIG. 4, for example, is used to determine whether the connection state of the clamp sensor with respect to the measured electric path is correct or incorrect. According to this, the voltage signal is input to one input channel ch1, and the current signal from the clamp sensor is input to the other input channel ch2. Although the clamp sensor actually outputs a current signal after converting it into a voltage, the current signal will be described here for convenience.

The voltage signal and the current signal are amplified by the amplifiers 1a and 2
a after each predetermined amplification in a, the peak detection unit 1
b, 2b. And this peak detection unit 1
In b and 2b, the time indicating the peak value of each of the voltage signal and the current signal is measured, and the peak time difference detection unit 3 in the next stage is measured.
The time difference between voltage and current is calculated at.

In parallel with this, one cycle is detected by the cycle detecting section 4 from the voltage waveform or current waveform passing through the amplifiers 1a and 2a. The output (one cycle signal) of the cycle detection unit 4 is input to the phase angle detection unit 5 together with the output (time difference signal) from the peak time difference detection unit 3, and the same phase angle detection unit 5 causes the deviation of the voltage and the current to the phase. Calculated as a corner.

This phase angle is determined by a determination unit 6 including a CPU and the like.
Then, the correctness of the connection state of the clamp sensor to the measured electric circuit is determined. That is, the phase angle θ
If is within the range of −90 ° ≦ θ ≦ + 90 °, it is determined that the connection is correct.

[0008]

According to the above conventional example,
There is no noise or distortion in the voltage waveform or current waveform, and if their peak values can be taken accurately, there is no problem in accuracy, but
In the case where noise is superimposed on the voltage waveform or the current waveform, or when the inverter current waveform or the distortion waveform is used, the peak value may not be accurately obtained, and there is a risk of erroneous connection determination.
Also, it requires a relatively large number of parts in terms of configuration.

The present invention has been made in order to solve such a conventional problem, and its object is a clamp for an electric circuit to be measured without being affected by noise and waveform distortion, though having a simple structure. It is an object of the present invention to provide a method for determining a wire connection of a clamp sensor, which can accurately determine whether the wire connection state of the sensor is correct.

[0010]

In order to achieve the above-mentioned object, the invention according to claim 1 regards the current phase and the voltage phase of the electric current to be measured when the electric current to be measured is held by a clamp sensor. In the connection determination method of the clamp sensor that determines the correctness of the connection direction of the clamp sensor with respect to the measured circuit from the relationship, the voltage input section to which the voltage signal detected by the predetermined voltage sensor is input and the fundamental wave from the voltage signal A first fundamental wave output section for extracting and outputting
A current input section to which a current signal converted into a voltage and detected by the clamp sensor is input, and a second fundamental wave output section that extracts and outputs the fundamental wave from the current signal, and the first and second fundamentals And a multiplication unit for calculating active power by multiplying each fundamental wave output from the wave output unit, and when the active power ≧ 0, the connection state of the clamp sensor to the measured electric circuit is set to “positive”, and In other cases, the connection state of the clamp sensor with respect to the measured electric circuit is determined to be "wrong".

As described above, since each fundamental wave is extracted from the voltage signal and the current signal, the respective fundamental waves are multiplied to obtain active power, and the connection state of the clamp sensor is determined from the value. It is possible to accurately determine the correctness of the connection state of the clamp sensor without relying on the peak value as in the conventional case.

In this case, the invention of claim 2 is characterized in that each of the first and second fundamental wave output sections comprises a band-pass filter that passes only the fundamental wave. In the invention of claim 3, the voltage input section and the current input section each include an A / D converter,
Each of the first and second fundamental wave output sections has a corresponding A / D.
It is characterized by including FFT calculation means for calculating the effective value and phase of the fundamental wave from the digital data converted by the converter.

As described above, according to the present invention, each fundamental wave can be extracted from the voltage waveform and the current waveform both in terms of hardware and software. Further, as compared with the conventional example, the period detection unit, the phase angle detection unit, and the like are unnecessary, which is also advantageous in terms of configuration. When obtaining the effective value and the phase of the fundamental wave by the FFT calculation means, as described in claim 4, the phase difference between the voltage input and the current input is θ, and whether cos θ ≧ 0 is satisfied or not. Accordingly, it may be possible to determine whether the connection state of the clamp sensor is correct.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, in order to better understand the technical idea of the present invention, its embodiments will be specifically described.

Basically, the present invention extracts a fundamental wave from a voltage input section 10 and a current input section 20 and a voltage signal of the voltage input section 10 and outputs the fundamental wave, as shown in FIG. The fundamental wave output unit 30 and the second fundamental wave output unit 40 that extracts and outputs the fundamental wave from the current signal of the current input unit 20.
And a multiplication unit 50 that multiplies each of the fundamental waves to calculate an active power value, and a connection determination unit 60 that determines whether the connection state of the clamp sensor is correct based on the active power value.

The voltage input section 10 receives the voltage signal of the measured electric circuit from the input channel ch1 via a predetermined voltage sensor (not shown). Further, the current input section 20 receives the current signal of the measured electric circuit detected by the clamp sensor (not shown) from the input channel ch2. Since the clamp sensor is a voltage output type, the current signal is actually converted into a voltage and the input channel ch
2 is input, but for convenience of explanation, it will be treated as the current signal as it is.

FIG. 2 shows an example of a circuit for digitally processing a voltage signal and a current signal. That is, according to this example, the voltage input unit 10 and the current input unit 20 both digitally output the amplifiers 11 and 21 that amplify the respective input signals in a predetermined manner, and the respective input signals amplified by the amplifiers 11 and 21 respectively. And A / D converters 12 and 22 for converting to.

In this connection, the first fundamental wave output section 30 and the second fundamental wave output section 40 are composed of FFT (Fast Fourier Transform) operation sections 31, 41. Each FFT
In the arithmetic units 31 and 41, the effective values and the phases of the fundamental waves of the voltage signal and the current signal are calculated based on the digital data from the A / D converters 12 and 22.

Then, in the multiplication section 50 at the next stage, the effective power value P is obtained from the effective value and phase of the fundamental wave. That is, in the multiplication unit 50, the effective value of the voltage is V, the effective value of the current detected by the clamp sensor is I, and the phase difference of the current input with respect to the voltage input is θ.
The calculation of I × cos θ is performed to calculate the active power value P.

Then, the active power value P is sent to the final-stage connection determination unit 60, where it is compared with "0" as a reference value. That is, in the connection determination unit 60, P ≧ 0
If the condition of is satisfied, the connection (connection) state of the clamp sensor to the measured electric circuit is determined to be "positive", and otherwise, that is, if P <0, it is determined to be "wrong" connection. . In the case of incorrect connection, it is preferable to positively inform the user by, for example, a buzzer or a display. Note that the correctness of the connection state of the clamp sensor can be determined more simply by whether cos θ ≧ 0 or not, without calculating the active power value P as described above.

On the other hand, FIG. 3 shows an example of a circuit for processing a voltage signal and a current signal in an analog manner. In this case, both the voltage input section 10 and the current input section 20 have an amplifier 1 for amplifying the respective input signals in a predetermined manner.
The first and second fundamental wave output units 30 and 40 include bandpass filters 32 and 42 that pass only the fundamental wave of each input signal.

The fundamental waves of the voltage signal and the current signal that have passed through the bandpass filters 32 and 42 are input to a multiplier 51 as a multiplication unit 50. The multiplier 51 is composed of, for example, an integrating circuit and a smoothing circuit, and the multiplier 51 outputs an analog signal corresponding to the active power value P to the connection determination unit 60.

The connection determination unit 60 is composed of a comparator 61, and the analog signal as the active power value P is input to its + side input terminal. In this case, the comparator 61
The side input terminal is connected to the ground potential (0 potential). Therefore, the comparator 61 determines whether P ≧ 0 as in the case of the digital processing.

The present invention is not limited to the power measurement using the clamp sensor, but at least the measurement in which the phase is a problem, for example, the flow direction in the harmonic analysis,
That is, it can be applied to the measurement of the inflow and outflow directions of harmonics with respect to the load to be measured.

[0025]

As described above, according to the present invention,
The following effects are obtained. That is, when the current to be measured is grasped by the clamp sensor and the current is detected, a predetermined voltage sensor is used to determine the correctness of the connection direction of the clamp sensor to the measured circuit from the relationship between the current phase and the voltage phase. Voltage input section to which the detected voltage signal is input, the first fundamental wave output section that extracts and outputs the fundamental wave from the voltage signal, and the current signal that is detected by being converted into a voltage by the clamp sensor is input. The current input section and the second fundamental wave output section that extracts and outputs the fundamental wave from the same current signal and the respective fundamental waves output from the first and second fundamental wave output sections are multiplied to obtain active power. And a multiplication unit for calculating, and when the active power is ≧ 0, the connection state of the clamp sensor to the measured electric circuit is set to “positive”, and in other cases, the connection state of the clamp sensor to the measured electric circuit is determined. According to the invention as set forth in claim 1, which determines that the error is "erroneous", noise is superimposed on the measured waveform or the inverter is not dependent on the peak values of the voltage and current waveforms as in the conventional case. Even if the waveform is distorted, such as a current waveform, it is possible to accurately determine whether the connection state of the clamp sensor is correct.

In this case, according to the invention of claim 2, wherein the first and second fundamental wave output sections are bandpass filters which pass only the fundamental wave respectively, in addition to the effect of claim 1, the analog processing is performed. However, there is an effect that the structure can be simplified.

Further, input signals are respectively A / D-converted at the voltage input section and the current input section, and the digital data thereof are subjected to FFT operation to calculate the effective value and phase of the fundamental wave of each input signal. According to the third aspect of the invention, the respective fundamental waves can be extracted from the voltage waveform and the current waveform in terms of software as well, which also eliminates the need for a cycle detection unit, a phase angle detection unit, etc., as compared with the conventional example. Therefore, it is structurally advantageous.

Further, the phase difference between the voltage input and the current input obtained by the FFT calculation means is θ, and cos θ
According to the invention described in claim 4, wherein it is determined whether or not ≧ 0, the correctness of the connection state of the clamp sensor can be determined very simply without calculating the active power value.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a block diagram showing an embodiment of digital processing according to the present invention.

FIG. 3 is a block diagram showing another embodiment of the analog processing of the present invention.

FIG. 4 is a block diagram for explaining a conventional example.

[Explanation of symbols]

 10 voltage input section 11,21 amplifier 12,22 A / D converter 20 current input section 30 first fundamental wave output section 31,41 FFT calculation section 32,42 bandpass filter 50 multiplication section 51 multiplier 60 connection determination section 61 comparator

Claims (4)

[Claims] 1. A clamp sensor wire connection for determining whether the clamp sensor wire is connected to the wire under test from the relationship between the current phase and the voltage phase when gripping the wire under test with the clamp sensor to detect a current. In the determination method, a voltage input unit to which a voltage signal detected by a predetermined voltage sensor is input, a first fundamental wave output unit that extracts and outputs the fundamental wave from the voltage signal, and a voltage is output by the clamp sensor. A current input section to which the converted and detected current signal is input, a second fundamental wave output section that extracts and outputs the fundamental wave from the current signal, and a first fundamental wave output section and a second fundamental wave output section that output the fundamental wave. And a multiplying unit for calculating active power by multiplying each fundamental wave. When the active power ≧ 0, the connection state of the clamp sensor to the measured electric circuit is set to “positive”, and In other cases, the connection determination method for the clamp sensor is characterized in that the connection state of the clamp sensor with respect to the measured electric circuit is determined as "wrong". 2. The method according to claim 1, wherein each of the first and second fundamental wave output sections includes a bandpass filter that passes only the fundamental wave. 3. The voltage input section and the current input section each include an A / D converter, and each of the first and second fundamental wave output sections includes digital data converted by each A / D converter. 2. The clamp sensor wire connection determination method according to claim 1, further comprising FFT calculation means for calculating an effective value and a phase of the fundamental wave. 4. The phase difference between the voltage input and the current input obtained by the FFT calculation means is defined as θ, and co
When sθ ≧ 0, the connection state of the clamp sensor to the measured electric circuit is determined to be “positive”, and in other cases, the connection state of the clamp sensor to the measured electric circuit is determined to be “erroneous”. The connection determination method for the clamp sensor according to claim 3.