JP7173805B2 - Current measuring device and current measuring method - Google Patents

Description

The present invention relates to a current measuring device and a current measuring method. The invention particularly relates to the measurement of intermittent earth leakage.

There is intermittent earth leakage as an earth leakage phenomenon. In many cases, this intermittent leakage current is temporary even if it occurs, and when the occurrence of leakage current is detected and leakage detection is performed, it returns to a healthy state and the leakage phenomenon has already disappeared. . Even if the earth leakage monitoring device detects the occurrence of earth leakage, the earth leakage phenomenon disappears at the time of earth leakage investigation, so it is necessary to detect the occurrence of an intermittent earth leakage event and store the phenomenon in memory for earth leakage investigation. .
As such a technique for storing intermittent leakage currents, a predetermined threshold value is set as the leakage current, and information on the timing at which the leakage current exceeding this threshold occurs, the leakage current value, and the There is a technique for storing intermittent leakage information by storing information on the timing of restoration to a healthy state.
Patent Documents 1 and 2 are known as technologies for storing and searching for such intermittent earth leakage.

Japanese Patent No. 2821904 Japanese Patent Application Laid-Open No. 2006-343170

Referring to FIG. 5, the recording operation of the leakage phenomenon in the intermittent leakage detection will be described.
As shown in FIG. 5, a trigger level for ground leakage detection is set in advance as a threshold value. This trigger level is set each time an earth leakage detection is performed, and is set with reference to the detected amount from the earth leakage current detection standard required in the standards for electrical equipment.
A clamp sensor is clamped to the wire to be measured, and a clamp meter or the like is used to measure the effective value of the current flowing through the wire to be measured at a predetermined sampling interval.
When an electric leakage phenomenon occurs, the effective current value exceeds the set trigger level. Therefore, the date and time information when the effective current value exceeds the trigger level is stored in the memory as the "leakage start time". After the electric leakage starts, the effective current value falls below the trigger level, so the date and time information when it fell below the trigger level is stored in the memory as "electric leakage end time". Also, the maximum value of the effective current value during the leakage period is stored as the "maximum value".
In this way, a set of "leakage start time", "leakage end time", and "maximum value" is stored in the memory until the measurement is completed. In addition, a plurality of sets of intermittent leakage currents occurring during the measurement period are stored.

In the memory of the intermittent leakage described above, the leakage period is from the timing when the current effective value exceeds the trigger level to the timing when it falls below the trigger level.
However, as shown in the graph of FIG. 5, the leakage starts when the current value starts to increase before the current value reaches the trigger level, but after it exceeds the trigger level. Assuming the leakage start time, the timing at which the current value begins to increase cannot be grasped. For this reason, it was not possible to accurately grasp the true start time of the electric leakage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a current measuring apparatus and method that can more accurately measure the timing of the start of earth leakage and more accurately investigate the phenomenon of intermittent earth leakage. and

A first aspect of the present invention includes comparison means for periodically sampling a wire to be measured and comparing the obtained current value with a preset threshold value, and storage means for storing the obtained current value and its timing information. In the current measuring device comprising If it is lower than the current value acquired at the timing, the low measurement value and its timing information are stored, and if the acquired current value exceeds the threshold value and is larger than the current value acquired at the previous timing Means for storing the measured value as the maximum current value, and storing the current value and timing information when the acquired current value falls below the threshold value after exceeding the threshold value. characterized by comprising

In the present invention, when the acquired current value falls below the threshold value after exceeding the threshold value, it is determined whether or not the current value has stabilized. In this case, the stable current value and its timing information can be stored.

A second aspect of the present invention is a current measurement in which a current value obtained by periodically sampling a wire to be measured is compared with a preset threshold value, and the obtained current value and its timing information are stored in a storage means. The method, wherein if the acquired current value is below the threshold value and is lower than the current value acquired at the previous timing, the storage means stores the low measured value and its timing information; However, when the acquired current value exceeds the threshold value and is larger than the current value acquired at the previous timing, the measured value is stored as the maximum current value, and the storage means stores the acquired current value as the maximum current value. When the current value falls below the threshold value from the state of exceeding the threshold value, the current value and the timing information thereof are stored.

In the present invention, since the leakage start time can be detected more accurately, intermittent leakage can be investigated more accurately and quickly.

It is a figure showing an example of composition of a clamp meter which is an embodiment of the invention. 4 is a flow chart for explaining a memory operation of an electric leakage phenomenon in the embodiment of the present invention; 4 is a flow chart for explaining a memory operation of an electric leakage phenomenon in the embodiment of the present invention; 4 is a graph for explaining the triggering of the earth leakage phenomenon of the present invention; 2 is a graph for explaining triggering of an earth leakage phenomenon in the prior art;

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a clamp meter according to an embodiment of the invention. In the present embodiment, it is assumed that a clamp meter is attached to an electric wire to be measured to detect and store an intermittent leakage phenomenon.

This clamp meter includes a current sensor 10 and a measuring device main body 20, and the current sensor 10 is selected and connected to the measuring device main body 20 according to the measurement application. The current sensor 10 includes a magnetic core that forms a closed magnetic path that is annularly arranged around the wire to be measured, and a magnetic sensor that includes a Hall element and a detection coil for detecting the magnetism of the magnetic core. There are also cable-type flexible current sensors.

The measurement device main body 20 includes an amplifier 21 to which the output of the current sensor 10 is input, a low-pass filter (LPF) 22 that removes signals with a frequency higher than the commercial frequency from the signal of this amplifier 21, and an analog conversion of the output of the amplifier 21. an analog-to-digital converter 24 for converting the output of the low-pass filter 22 into an analog-to-digital converter; and a CPU (Central Processing Unit) 26 to which the output of the analog-to-digital converter 24 and the output of the analog-to-digital converter 25 are input. , a memory 27 , an operation unit 31 connected to the CPU 26 via an interface (I/0) 28 , a communication unit 32 , a display unit (LCD) 33 , and an audio output unit 34 .

The operation of the measuring device shown in FIG. 1 will be described.
The signal output from the current sensor 10 is amplified by the amplifier 21 , and one branched signal is input to the analog-to-digital converter 24 to be converted into a digital signal and output to the CPU 26 . The other branched signal is input to the analog-to-digital converter 25 through the low-pass filter 22, converted to a digital signal, and output to the CPU 26. FIG. The low-pass filter 22 has a cutoff frequency of 150 Hz or 180 Hz, for example, and is a filter that passes commercial frequency components and removes high frequency components mixed in with the commercial frequency.

Based on the program stored in the memory 27, the CPU 26 computes the periodically sampled signal to compute the current value of the wire to be measured. This output is displayed on the display unit 33 via the interface 28, and the calculated measured value is also stored in the memory 27. FIG. Also, the input signal is stored in the memory 27 in order to calculate the measured value. The operation unit 31 inputs various settings and operations. The communication unit 32 makes it possible to output information such as measured values to the outside, for example, via Bluetooth (registered trademark). Also, the sound output unit 34 can output sound of various operations and the like.

The CPU 26 also has a clock function, and can store the acquired measured value and its time information in the memory 27 . The CPU 26 has a function of comparing the acquired measured value with a set threshold, which is a trigger level for detecting electric leakage, and a function of comparing the previously acquired measured value with the acquired measured value. . Based on the result of comparison by this comparison function, the measured value and time information to be stored are updated, and the data of the current value and time information required for leakage detection are stored and stored.

A memory storage operation of an intermittent earth leakage using the clamp meter of the present embodiment will be described with reference to the flow charts of FIGS. 2 and 3 and the graph of FIG.
First, before starting measurement, a threshold value is set (step S10). The setting of this threshold value is input from the operation unit 31 . The threshold value is set by the operator according to the leakage phenomenon to be detected based on the standards indicated in the electrical equipment technical standards, the leakage current value detected by the leakage monitoring device or the like.
After setting the threshold value, clamp the clamp meter to the wire to be measured and instruct the start of measurement.

The electric wire to be measured is sampled by the current sensor 2 at regular intervals, for example, at intervals of one second, the current effective value is calculated, and the current effective value and the current date and time are recorded in the memory 27 (step S11). The obtained measured value is compared with the measured value immediately before (step S12), and if the obtained measured value is lower than the previous measured value, the obtained measured value is set as the "earth leakage start measured value". , and overwrites the sampling time at which the measured value is acquired as the "earth leakage start date and time" (step S13). Similarly, when the acquired measurement value is the same as the previously acquired measurement value, the acquired measurement value and the date and time are overwritten as the "earth leakage start measurement value" and "earth leakage start date and time". If the measured value is higher than the previously obtained measured value, the measured value is compared to the set threshold without overwriting (step S14).
If the obtained measured value is smaller than the threshold in the comparison with the threshold value in step S14, the operation returns to the memorizing operation of the start of electric leakage, and the next obtained measured value and the previously obtained measured value are stored. The process shifts to comparison (step S11).
By such operation, the measured value and the time information of date and time at the time points #1→#2→#3 in FIG.

As a result of comparing the obtained measured value with a set threshold value, if it exceeds the threshold value, the measured value and the current date and time are obtained (step S15), and compared with the stored maximum leakage current value (step S16). If it is greater than the stored maximum leakage current, the measured value is overwritten as the "maximum leakage current" and stored (step S17). It should be noted that the time information of the date and time when this "maximum earth leakage value" was acquired may be stored. When the measured value exceeds the threshold value and is larger than the previous measured value and the measured value increases, the maximum leakage current value is updated. In addition, when the measured value decreases from the maximum value, the measured value is not overwritten, so the maximum leakage current value is stored as it is. Once the measured value decreases and then increases to exceed the stored leakage maximum value, the measured value is stored as the leakage maximum value.

Here, if the acquired measurement value is smaller than the previous measurement value, the measurement value of the past 5 data is set to A, and the minimum value of the measurement values of the past 5 data is set to B (step S18), and A is the threshold value. is smaller and the absolute value of AB is smaller than 0.1 mA (step S19). This determination is to determine whether or not the measured value has fallen below the threshold value used as the criterion for judging electric leakage, the measured value has stabilized, and the electric leakage has ended. In order to determine whether the measured value is stable, in this flowchart, the maximum and minimum values of the past five data are detected, and if the difference between the maximum and minimum values is 0.1 mA or less, the measurement I think the value is stable.
If the measured value is not stable, the next measured value is acquired, and if it is determined that the measured value is stable, the "earth leakage end measured value" and "earth leakage end date and time" are stored (step S20). .
When the electric leakage ends, a set of "earth leakage start measurement value", "earth leakage start date and time", "earth leakage maximum value", "earth leakage end measurement value", and "earth leakage end date and time" is stored in the memory 27 as the n-th earth leakage information. (step S21).

With this operation, when the measured value is lower than the set trigger level threshold and lower than the previous measured value, the measured value and the date and time are set as the "earth leakage start measurement value" and "earth leakage start date and time". Since it is stored, in the graph of FIG. 4, the measured value and date and time at #1, the measured value and date and time at #2, and the measured value and date and time at #3 are overwritten in order, and finally , #3 are stored and stored. When the measured value exceeds the threshold value, the maximum leakage value is updated until the maximum leakage value reaches the peak value, and the maximum leakage value is stored. When the measured value falls below the threshold value and it is determined that the measured value has stabilized, the measured value and the date and time at #4 in FIG. be done.

The measured value of #4 in FIG. 4 represents the value obtained without determining whether or not the measured value is stable. shall be determined whether has stabilized.
Intermittent earth leakage occurs due to deterioration of insulation or weather changes. It is more preferable to set the point of time when the electric leakage is stabilized and falls below the set trigger level for electric leakage detection as the electric leakage end point.

Since such a set of data is stored in the memory 27 of the clamp meter during the measurement period, when the measurement is completed, this data can be read out to determine when the leakage started and ended, its leakage period, and the leakage period. By checking the current value, it is possible to investigate and investigate the location of the leakage, the cause of the leakage, and the like. In the present invention, since the true earth leakage phenomenon from the time when the earth leakage starts to the time when the earth leakage ends before the measured current effective value exceeds the set threshold value is recorded and saved, earth leakage detection and investigation can be facilitated. can do.

If the date and time information of the maximum electric leakage value is also stored, it can be useful for further investigation of the electric leakage phenomenon.
Although the acquired measured value is explained as the effective current value acquired each time sampling, it is also possible to calculate a moving average and compare it with the moving average of the measured values at the previous time. Also, the comparison between the measured value and the threshold value may be compared with a moving average of the measured values. If the measured value fluctuates each time sampling is performed, it is possible to obtain more accurate leakage period data by comparing moving averages even if the measured value fluctuates.

In the above-described embodiment, the leakage data is recorded and saved by clamping the clamp meter to the electric wire to be measured. Alternatively, a multi-channel clamp meter and recorder capable of detecting and storing electric leakage in a plurality of wires to be measured by clamping a clamp sensor, which is a current sensor, to a plurality of wires to be measured may be used.

10 current sensor 20 measuring device body 21 amplifier (AMP)
22 low pass filter (LPF)
24, 25 analog-to-digital converter (A/D)
26 CPUs
27 memory 28 interface (I/O)
31 operation unit 32 communication unit 33 display unit (LCD)
34 sound output section

Claims (3)

A current measuring device comprising a comparison means for periodically sampling a wire to be measured and comparing the acquired current value with a preset threshold value, and a storage means for storing the acquired current value and its timing information,
The comparison means includes comparison means for comparing the acquired current value with the current value acquired at the previous timing,
The storage means
Only when the acquired current value is less than the threshold value and lower than or the same current value as the current value acquired at the previous timing, the current value that is lower or the same current value is used as the leakage start measurement value, The timing information when the ground leakage start measurement value is acquired is stored as the ground leakage start date and time,
when the acquired current value exceeds the threshold value and is greater than the stored maximum leakage current value, storing the current value as the maximum leakage current value ;
When the acquired current value falls below the threshold value after exceeding the threshold value, the current value that has fallen below is the earth leakage end measured value , and the timing information when the earth leakage end measured value is acquired. as the earth leakage end date and time. The current measuring device according to claim 1,
When the obtained current value falls below the threshold value after exceeding the threshold value, the difference between the maximum value and the minimum value of the current value obtained at a predetermined number of timings is within a predetermined range. When the current value becomes stable, it is determined that the current value is stable, and the current value determined to be stable is stored as the earth leakage end measurement value , and the timing information is stored as the earth leakage end date and time. Device. A current measuring method for periodically sampling a wire to be measured, comparing the acquired current value with a preset threshold value, and storing the acquired current value and its timing information in a storage means,
Only when the acquired current value is less than the threshold value and lower than or the same current value acquired at the previous timing, the current value stored in the memory means is the same or lower than the current value. storing the start measured value and the timing information when the leak start measured value is acquired as the leak start date and time;
when the acquired current value exceeds the threshold value and is greater than the stored maximum leakage current value, causing the storage means to store the current value as the maximum leakage leakage current;
When the acquired current value falls below the threshold value after exceeding the threshold value in the storage means , the current value that has fallen below is acquired as an earth leakage end measurement value , and the earth leakage end measurement value is acquired. Memorize the timing information at the time as the earth leakage end date and time
A current measurement method characterized by:

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