JP4686000B2 - Power meter waveform judgment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for determining a waveform of a wattmeter , and more specifically, waveform determination that does not respond to fluctuations in the level of a signal under measurement and can detect sudden phenomena caused by superposition of harmonics and the like. It is about the method.
[0002]
[Prior art]
For example, when a voltage waveform is observed over a long period of time, in order to facilitate analysis of when an abnormality has occurred, conventionally, as shown in FIG. From the reference voltage waveform Vref, an upper limit value U and a lower limit value L for the determination are set, and this is used as a determination area to monitor the voltage to be measured.
[0003]
This determination area is appropriately set as, for example, a ± 5% width of the measurement range or a ± 5 V width of the reference voltage waveform Vref. In any case, one cycle of the reference voltage waveform Vref is set for each sampling point. The upper limit value U and the lower limit value L are stored in, for example, a memory of a microcomputer (abbreviation: microcomputer).
[0004]
At the time of measurement, the microcomputer reads the upper limit value U and the lower limit value L from the memory, and monitors whether there is a portion outside the determination area in the voltage waveform to be measured by the comparator function, which is illustrated in FIG. Thus, when there is a portion outside the determination area range in the measured voltage waveform V, it is determined as NG (abnormal).
[0005]
[Problems to be solved by the invention]
According to this, as shown in FIG. 7, not only when a whisker-like sudden waveform as shown in FIG. 6 appears due to impulse noise or harmonics superimposed on the voltage waveform to be measured V, but as shown in FIG. Even if a part of the voltage waveform V to be measured falls outside the determination area range due to the fluctuation, the determination is NG.
[0006]
In the case of a commercial power supply, the level fluctuation of the voltage waveform V to be measured is strongly influenced by the time zone. As an example, in supermarkets and convenience stores, but in such overall is less, for example, nighttime power consumption is stable at around 100V, is in full operation sometimes voltage of each piece of equipment, such as air conditioning and heating facilities and food refrigeration equipment lighting equipment to it It may drop to around 97-98V.
[0007]
You may want to monitor waveforms with such level fluctuations and detect abnormalities only when the shape of the waveform is truly corrupted by impulse or harmonic superposition. However, the above-mentioned conventional technology also detects level fluctuations. Therefore, the abnormal waveform phenomenon that should be detected may be missed.
[0008]
[Means for Solving the Problems]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a wattmeter that can detect only waveform abnormality due to impulse or harmonic superposition regardless of waveform level fluctuations. The object is to provide a waveform determination method.
[0009]
In order to achieve the above object, the present invention provides an A / D converter that samples a signal under measurement at a predetermined time interval, and a measurement control means that performs various calculations using the digital signal and obtains a measurement value of the signal under measurement. The measurement control means sets a determination area (allowable maximum value and allowable minimum value) of a predetermined width for each sampling of at least one period of the reference waveform previously acquired, and the signal under measurement In the wattmeter waveform determination method for making a predetermined determination by comparing each sampling data and the determination area, the measurement control means is configured to determine whether the reference waveform is effective when setting the determination area from the reference waveform. thereby calculating the value a, and stored in memory by setting the judgment area J1 seeking the maximum allowed value of the reference waveform and the allowable minimum value, the measuring Change No. of In measuring, determined by calculation effective value B of the measured signal for each one cycle, the values of the allowable maximum value and the minimum allowable upper Symbol judgment area J1 B / A times to The waveform of the signal under measurement is determined by the changed determination area J2 .
[0010]
As described above, according to the present invention, the width of the determination area is changed by the ratio obtained by multiplying the effective value A of the reference waveform by the effective value B of the measured signal by B / A. Regardless of the level fluctuation, it is possible to detect only the abnormal waveform that should originally be obtained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, an example explains the present invention . FIG. 1 shows a greatly simplified block diagram of a power meter according to this embodiment .
[0013]
The input terminal 1 is supplied with a voltage signal of a commercial power source measured by a voltmeter (not shown) at a superstore, for example. The voltage signal is converted into a digital signal (voltage data) at a predetermined sampling interval by the A / D converter 2 and given to the microcomputer (or CPU) 3 at the next stage.
[0014]
In addition to calculating its effective value from the voltage data, the microcomputer 3 has a function of calculating active power, reactive power, phase angle, etc. from the voltage data and current data input from another input system (not shown). The measured value is displayed on a display 5 such as a display.
[0015]
Further, the microcomputer 3 has a determination function. That is, the microcomputer 3 compares the determination reference value input from the operation unit 4 with the signal under measurement, determines whether there is an abnormality, and displays the determination result on the display 5.
[0016]
According to the present invention, the waveform determination is performed as follows. As shown in the flowchart of FIG. 2, first, a determination area is created based on a reference waveform (step ST1). As a reference waveform, for example, a stable voltage waveform of 50 Hz and 100 V is digitally converted by the A / D converter 2 at a predetermined sampling interval to obtain voltage data for one cycle.
[0017]
Assuming that the judgment reference value is input in advance to the microcomputer 3 from the operation unit 4 as ± 5% of the range or ± 5 V, for example, the microcomputer 3 determines the maximum allowable value for each voltage data for one cycle. A value and an allowable minimum value are obtained, and the determination area J1 is stored in the memory. Further, the microcomputer 3 calculates the level of the reference waveform (in this case, the effective value) from each voltage data, and also stores this in the memory (step ST2). Here, the effective value of the reference waveform is A.
[0018]
Next, the voltage waveform to be measured is taken in and digitally converted at a predetermined sampling interval by the A / D converter 2 as in the case of the reference waveform to obtain voltage measurement data for one cycle (step ST3). The microcomputer 3 also stores each measured voltage data in the memory, and calculates the level (effective value) of the measured voltage waveform from each measured voltage data (step ST4).
[0019]
When the effective value of the voltage waveform to be measured is B, the microcomputer 3 changes the allowable maximum value and the allowable minimum value of the determination area J1 set previously according to the effective value B of the voltage waveform to be measured (step ST5). . This is the determination area J2 used for actual determination. In the present invention, the determination area J2 is obtained by multiplying the allowable maximum value and allowable minimum value of the determination area J1 by B / A.
[0020]
For easy understanding, FIG. 3 shows an example of the determination area J2 that is changed when the effective value B of the measured voltage waveform is larger than the effective value A of the reference waveform, and FIG. 4 shows the effective value of the measured voltage waveform. An example of the determination area J2 changed when the value B is smaller than the effective value A of the reference waveform is shown. In the figure, U is an allowable maximum value and L is an allowable minimum value.
[0021]
In this manner, after the determination area J2 is created, the voltage waveform to be measured V is determined by the determination area J2 (step ST6). That is, measured voltage data for one cycle is read from the memory, and it is determined whether each measured voltage data is within the determination area J2 (step ST7). If it is outside the range of the determination area J2, “waveform abnormality” is displayed on the display 5 as NO (step ST8).
[0022]
If all the measured voltage data are within the determination area J2, the waveform is returned to step ST3 as normal, and steps ST3 to ST7 are repeated for each cycle of the measured voltage waveform. In the case of NO determination in step ST7, it is optional to end the measurement after displaying “waveform abnormality” in step ST8 or to return to step ST3 and continue the measurement. In addition, it is optional whether or not to store voltage data to be measured that has been determined.
[0023]
【The invention's effect】
As described above, according to the present invention, the allowable maximum value and the allowable minimum value of the determination area according to the ratio obtained by multiplying the effective value A of the reference waveform and the effective value B of the signal under measurement by B / A. By changing these values, it is possible to detect only an abnormal waveform that should be originally obtained by superimposing impulses or harmonics, regardless of the level fluctuation of the signal under measurement.
[Brief description of the drawings]
Schematic block diagram showing an actual施例of the present invention; FIG.
FIG. 2 is a flowchart for explaining a waveform determination method of the present invention.
FIG. 3 is a waveform diagram showing a determination area changed according to the present invention.
FIG. 4 is another waveform diagram showing a determination area changed according to the present invention.
FIG. 5 is a waveform diagram for explaining a general waveform determination area.
FIG. 6 is a waveform diagram for explaining a detection state of a sudden abnormal waveform in the waveform determination area.
FIG. 7 is a waveform diagram showing an example in which an abnormal waveform is detected due to a level fluctuation in relation to a waveform determination area.

Claims (1)

An A / D converter that samples the signal under measurement at a predetermined time interval; and a measurement control means that performs various calculations using the digital signal and obtains a measurement value of the signal under measurement. For at least one period of the captured reference waveform, a predetermined width judgment area (allowable maximum value and allowable minimum value) is set for each sampling, and each sampling data of the signal under measurement is compared with the judgment area. In the wattmeter waveform determination method for performing a predetermined determination,
The measurement control means calculates an effective value A of the reference waveform when setting the determination area from the reference waveform, and obtains an allowable maximum value and an allowable minimum value of the reference waveform to determine the determination area J1. set stored in the memory, the in measuring the signal to be measured, determined by calculation effective value B of the measured signal for each one cycle, the upper Symbol the allowable maximum value and the minimum allowable value of the determination area J1 A method for determining a waveform of a wattmeter, characterized in that the waveform of the signal under measurement is determined based on the changed determination area J2 .

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