JPH08122373A - Insulation resistance-measuring apparatus - Google Patents

Abstract

PURPOSE: To measure an insulation resistance value with high reliability, by providing a means for impressing a measuring voltage, a means for extracting a current value, a means for extracting an average current value, a means for obtaining the insulation resistance value and a display means, thereby automatizing the measurement work for the insulation resistance value and eliminating irregularities in measuring values by individual persons and measuring errors due to erroneous reading. CONSTITUTION: A measuring voltage is impressed by 16 to a resistor Ri of an insulating part, and a current running in the insulating part is AD converted at 17 and obtained as a current value. Current values obtained a plurality of the number of times in a fixed time are averaged to obtain art average current value. Moreover, a value of the measuring voltage is divided by the average current value to obtain an insulation resistance value of the insulating part. The insulation resistance value is displayed at 24, 25. Even when an indicated value varies due to a change of the current running in the insulating part at the measuring time, the insulation resistance value is measured automatically, thus preventing the occurrence of irregularities in measuring values by differences of measuring persons and reading errors. A measuring result of high reliability is accordingly obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation resistance measuring device for measuring insulation resistance of electric equipment and the like.

[0002]

2. Description of the Related Art In electrical equipment such as transformers, in order to prevent accidents due to electrical leakage when the electrical equipment is in operation, the manufacturing factory side conducts a product inspection at the time of shipment and the user side conducts a regular inspection. Sometimes I measure the insulation resistance of the electrical equipment.

For example, a general-purpose insulation resistance meter is used to measure the insulation resistance at a voltage according to the standard of the electric device to be inspected, and the quality is judged based on the measured value.

FIG. 7 shows the structure of a conventional insulation resistance meter. In FIG. 7, the high voltage generator 2 uses the battery 1 as an input power source,
This is boosted to generate a high voltage, which is connected between the probe 5 and the clip 4 via the resistor R and the meter 3.
A high voltage is applied to the insulation to be measured. Since the high voltage generated by the high voltage generator 2 is constant, the current flowing through the insulating portion is inversely proportional to the insulation resistance of the insulating portion. Instrument 3
The insulation resistance value corresponding to the current flowing through the insulation part is graduated in advance, and the measurer reads the insulation resistance value from the instruction of the meter 3.

[0005]

However, the high voltage generator inside the insulation resistance tester inputs the DC input power supply voltage to the primary side of the converter transformer and switches it.
Since a high voltage is obtained by rectifying and smoothing the secondary voltage boosted by the converter transformer,
After turning on the power switch of the insulation resistance meter, the charging voltage of the capacitor that constitutes the smoothing circuit rises, the voltage generated by the high-voltage generator stabilizes, and the specified time until the indicated value of the meter stabilizes. It takes. Therefore, conventionally, the measurer waits until the indication of the meter is stabilized after turning on the switch of the insulation resistance meter, and then reads the indication value after the stabilization. Also, the insulation resistance value may fluctuate depending on the condition of the insulation part to be measured, and the indicated value of the instrument may fluctuate accordingly, so the measurer should read the average value and use it as the measured value. I was there. Under these circumstances, even for the same object to be measured, the measured insulation resistance value may vary due to the habit of the measurer, and there is a possibility that a measurement error may occur due to an incorrect reading of the indicated value. there were.

An object of the present invention is to automate the work of measuring the insulation resistance value and solve the problem of measurement error caused by variations in measurement values due to individual differences and reading errors.
An object of the present invention is to provide an insulation resistance measuring device capable of measuring the insulation resistance value with high reliability.

[0007]

According to the present invention, even if the indicated value fluctuates due to the fluctuation of the current flowing through the insulating portion at the time of measurement, the measurement of the insulation resistance value is automated, and the variation of the insulation resistance value depends on the measurer. In order to obtain a measurement result without any noise, as described in claim 1, a measuring voltage applying means for applying a measuring voltage to the insulating portion and a current flowing through the insulating portion are AD-converted to obtain a current value. A current value extracting means for obtaining, an average current value extracting means for obtaining an average current value by averaging current values obtained by the current value extracting means a plurality of times in a constant time, and a value of the measuring voltage as the average current value And a means for displaying the obtained insulation resistance value.

Further, according to the present invention, in order to measure the insulation resistance in a state where the current flowing through the insulating portion is stable after the measuring voltage is applied to the insulating portion, it is preferable that the insulating resistance is measured. In addition, the average current value extraction means averages the current value obtained by the current value extraction means after a lapse of a fixed time after the measurement voltage application means starts applying voltage to the insulating portion.

Further, according to the present invention, in order to appropriately reject a measurement value that may be erroneous, as described in claim 3, the average current value extraction means averages the current values. At this time, the singular value is excluded from the current value.

[0010]

In the insulation resistance measuring device according to the first aspect of the present invention, the measuring voltage is applied to the insulating portion, and the current flowing through the insulating portion is AD-converted to obtain the current value. Then, an average voltage value is obtained by averaging the voltage values obtained a plurality of times in a certain period of time, and further, the value of the measurement voltage is divided by an average current value to obtain an insulation resistance value of the insulating portion. Will be displayed. Since the measurement work is automatically performed in this manner, variations in measurement values due to individual differences and reading errors do not occur, and highly reliable measurement results can be obtained.

In the insulation resistance measuring device according to the second aspect, since the average value of the current value after a lapse of a fixed time after the voltage is applied to the insulating portion is obtained, the current flowing through the insulating portion is stable. The insulation resistance is measured and the insulation resistance value with high measurement accuracy is obtained.

In the insulation resistance measuring apparatus according to the third aspect, when the current values are averaged, for example, singular values such as maximum and minimum current values and values that are far from the average value are removed.
Incorrect measurement values are properly rejected, and insulation resistance values with high measurement accuracy are automatically obtained.

[0013]

1 to 5 show the structure of an insulation resistance measuring apparatus according to a first embodiment of the present invention.

FIG. 1 is a diagram showing the structure of the measuring voltage generator. In FIG. 1, reference numeral 12 includes a switching transistor and a control circuit for on / off controlling the switching transistor. The battery power source 1 is used as an input power source. It is a switching circuit for switching. Tr is a converter transformer. 2 of this converter transformer Tr
On the next side are diodes D1, D2 and capacitors C1,
A rectifying / smoothing booster circuit composed of C2 is connected. With this configuration, a predetermined measurement voltage is output from both ends of the capacitors C1 and C2. Further, in the figure, 11 is a relay contact as a power switch, and the exciting coil 1 of the relay
1'turns on / off the contact 11 in response to the a signal. The resistor R1 is connected to the capacitors C1 and C2 after the measurement is completed.
A discharging resistor for discharging the charging voltage of 13 and a relay contact 13 which is turned on at the time of discharging. Relay coil 13 '
Turns on / off the relay contact 13 according to the signal b. R
i is the symbol indicating the insulation resistance of the insulation part to be measured.

FIG. 2 is a block diagram of the main body of the insulation resistance measuring device. The insulation resistance measuring device main body 100 and the measuring voltage generator 101 shown in FIG. 1 are connected via signals a, b, c and d. In FIG. 2, the CPU 20 is the ROM 21
The program previously written in is executed to perform various processes described later. At that time, the RAM 22 is used as a working area such as a temporary storage area for the current value. Timer circuit 2
3 waits for a certain period of time and measures the certain period of time when performing a predetermined process. The display control circuit 24 comprises a display memory and a circuit for generating a display signal to the display 25 in accordance with the contents of the memory. The CPU 20 displays the insulation resistance value on the display 25 by writing predetermined display data in the display memory in the display control circuit 24. The key 27 is composed of various keys such as a ten key, a threshold value setting key and a measurement start key, and the key control circuit 26 reads these key operations. The AD converter 17 inputs the current indicated by the signals c and d, and converts the current value into a digital value. The contact signal output port 18 is shown in FIG.
The exciting coils 11 'and 13' of the relay shown in FIG. The CPU 20 outputs a predetermined value to the contact output port 18 to control ON / OFF of the relay contacts 11 and 13 shown in FIG.

3 to 5 are flowcharts showing the processing procedure of the CPU 20 shown in FIG. First, as shown in FIG. 3, the key is read and, for example, the numeric keypad (10
When the (key) is operated, it is registered in the register X. After that, when the threshold value setting key is operated, the entered value is stored as an abnormality determination threshold value RM described later. If the measurement start key is operated, the process proceeds to the flowchart shown in FIG.

As shown in FIG. 4, first, the relay contact 11 shown in FIG. 1 is turned on to wait for a predetermined time t1. After that, when the loop counter i is 1 to n, A
The converted value of the D converter is read, the converted value is multiplied by a proportional constant to obtain a current value, which is sequentially stored as I (1) to I (n). This proportional constant corresponds to the reciprocal of the ratio of the AD conversion value to the input current value of the AD converter. After the sampling of n times is completed, the maximum value and the minimum value are extracted from I (1) to I (n), respectively, and the average value Im1 of I (1) to I (n) excluding the maximum value and the minimum value is extracted. To calculate. By excluding the maximum value and the minimum value from the n sampled current values in this way, data that is highly likely to be erroneous is rejected, and the reliability of the average value is improved. When the value of n is relatively large, n pieces of current value data are sorted, and m pieces from the beginning and m pieces from the end (m <m <
(n-2m) in the central part excluding the data of n / 2)
The individual data may be averaged to obtain the average current value.

After that, a predetermined fixed time t2 is waited, n current values are sampled again by the same process, and the maximum and minimum values are removed from the data I (1) to I (n). Averaging is performed to calculate the average value Im2.

Thereafter, as shown in FIG. 5, Im1-Im
The value of 2 is obtained as d, and the magnitude of the predetermined threshold dmax for power supply capacity determination and the above d are compared. d ≧ d
If it is max, it is considered that the capacity of the battery 1 shown in FIG. 1 has decreased, and the warning is displayed. That is,
If the average current value Im2 obtained for the second time is lower than a certain value (dmax) compared to the average current value Im1 obtained for the first time, that phenomenon ends the measurement twice after the power is turned on. The decrease in the power supply capacity is detected by assuming that it is due to the decrease in the voltage of the battery 1 shown in FIG. 1 and the decrease in the measurement voltage applied to the insulating part. In this way, since the decrease in the power supply capacity is detected along with the measurement of the insulation resistance value, the battery capacity as the power supply is below the allowable limit, and the insulation resistance value is actually below the reference value. Regardless, the danger that the apparent insulation resistance value is high is eliminated.

If d <dmax, the average value Im of Im1 and Im2 is calculated, and the constant measurement voltage Vcc is divided by the average current value Im to calculate the insulation resistance value R, which is displayed. Then, the insulation resistance value R obtained by the measurement is compared with a predetermined abnormality determination threshold value RM. R <
If the relationship of RM, that is, the insulation resistance value is smaller than a predetermined value, it is considered that there is an abnormality in the insulating portion, and an abnormality alarm is displayed. If not, normal display is performed. After that, the discharge relay 13 shown in FIG. 1 is turned on for a predetermined time t3 and turned off again. As a result, the electric charges of the capacitors C1 and C2 are discharged through the discharging resistor R1.

In the example shown in FIGS. 4 and 5, A
An example of calculating the insulation resistance value from the relationship between the value Vcc of the measurement voltage and the average current value Im after obtaining the current value by multiplying the D conversion value by the proportional constant and averaging the values has been shown. The value is proportional to the current value, and the measuring voltage is constant, so
The insulation resistance value R may be calculated by averaging the D-converted values without converting the current value and multiplying the reciprocal of the obtained average value by a predetermined constant. The constant to be multiplied at that time is determined by the ratio of the AD conversion value to the input current value of the AD converter and the value of the measuring voltage.

Next, FIG. 6 shows the structure of an insulation resistance measuring apparatus according to the second embodiment of the present invention. Unlike the first embodiment, in the second embodiment, the value of the measurement voltage applied to the insulating portion can be switched. In FIG. 6, a key 27 is provided with a measuring voltage setting key,
The measurer operates the ten keys and the measurement voltage setting key to apply the measurement voltage according to the object to be measured, and selects one of the predetermined measurement voltages. CPU
The numeral 20 reads the operation of the ten-key pad and the measuring voltage setting key, and outputs the data for generating the selected measuring voltage to the I / O port 19. The measurement voltage generation circuit 16 generates a predetermined measurement voltage according to the data set in the I / O port 19, and applies the measurement voltage to the resistance Ri of the insulating portion via the resistance R2. The current-voltage conversion circuit 15 uses the resistance R2 when a current flows through the resistance Ri of the insulating portion.
It is a circuit that inputs a potential difference generated at both ends of and generates a voltage signal. The AD converter 17 converts this voltage,
Find a value proportional to the current value. The relay contact 14 is a relay contact that is turned on when a measurement voltage is applied to the insulating portion, 1
Reference numeral 3 is a relay contact that is turned on when the voltage charged in the output part of the measurement voltage generation circuit 16 is discharged at the end of measurement. Other configurations in FIG. 6 are the same as those shown in FIG. 2 as the first embodiment.

[0023]

According to the insulation resistance measuring device of the first aspect of the present invention, the measurement of the insulation resistance value is automated even if the indication value fluctuates due to the fluctuation of the current flowing through the insulation part during the measurement. As a result, there is no variation in measured values or misreading due to individual differences among measurers, and highly reliable measurement results can be obtained.

According to the insulation resistance measuring device of the second aspect, after the measurement voltage is applied to the insulation part, the insulation resistance is measured with the current flowing through the insulation part being stable. Insulation resistance with high measurement accuracy is required.

According to the insulation resistance measuring device of the third aspect, since the abnormal measurement value is appropriately rejected, the insulation resistance value with high measurement accuracy is automatically obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a measurement voltage generator in an insulation resistance measuring apparatus according to a first embodiment.

FIG. 2 is a diagram showing a configuration of an insulation resistance measuring device main body according to the first embodiment.

FIG. 3 is a flowchart showing a processing procedure of a CPU 20 shown in FIG.

FIG. 4 is a flowchart showing a processing procedure of a CPU 20 shown in FIG.

5 is a flowchart showing a processing procedure of a CPU 20 shown in FIG.

FIG. 6 is a diagram showing a configuration of an insulation resistance measuring device according to a second embodiment.

FIG. 7 is a diagram showing a configuration of a conventional insulation resistance meter.

[Explanation of symbols]

 R1-Discharge resistance Ri-Insulation resistance 100-Insulation resistance measuring device main body 101-Measurement voltage generator

Claims (3)

[Claims] 1. A measuring voltage applying unit for applying a measuring voltage to an insulating unit, a current value extracting unit for AD-converting a current flowing in the insulating unit to obtain a current value, and a plurality of times for obtaining a current value. Average current value extraction means for averaging the obtained current values to obtain an average current value, means for obtaining the insulation resistance value of the insulation part by dividing the value of the measurement voltage by the average current value, and the insulation An insulation resistance measuring device comprising: means for displaying a resistance value. 2. The insulation resistance according to claim 1, wherein the average current value extracting means averages the current value after a lapse of a fixed time after the measuring voltage applying means starts applying voltage to the insulating portion. measuring device. 3. The insulation resistance measuring device according to claim 1, wherein the average current value extracting means removes a singular value from the current value when averaging the current values.