JP4284668B2 - Insulation resistance measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an insulation resistance measuring device that measures the insulation resistance of an electric circuit to be measured, and more particularly to an insulation resistance measuring device that can easily perform an accuracy test that is periodically performed in the insulation resistance device.
[0002]
[Prior art]
Conventionally, in order to check the measurement accuracy of insulation resistance measuring devices, regular accuracy tests, in other words, calibration processing has been obliged due to safety standards issues and notifications from the Ministry of International Trade and Industry. . This accuracy test may be performed once a year or once every six months for a measuring device that is not frequently used, but once a month for a measuring device that is frequently used like a manufacturing plant. In some cases, the accuracy test is taught in degrees or less. Hereinafter, an accuracy test in the conventional insulation resistance measuring apparatus will be described with reference to FIG. In FIG. 4, a conventional insulation resistance measuring device is connected to the circuit to be measured. A breaker 2 that can cut both ends of the transformer 1 and its secondary side is installed in the circuit to be measured. The insulation resistance values between the secondary side of the circuit to be measured and the ground are defined as insulation resistances (R1) 3 and (R2) 4. 4 includes a current transformer 8 that detects the displacement of the leakage current from the transformer 1, an amplifier 9 that amplifies the detected displacement of the current, and a high-frequency component from the detected displacement of the current. The low-frequency pass filter 10 for removing the noise, the analog / digital converter 11 for converting the detected analog amount of the displacement of the current into a digital amount, the alarm display lamp 13 and the low-frequency oscillator 5 which will be described later are controlled and input. CPU 12 for determining the digital amount, a low frequency oscillator 5 for generating a voltage having a frequency lower than that of commercial AC for measuring insulation resistance, an amplifier 6 for amplifying the low frequency voltage for measuring insulation resistance, and a transformer 1 It comprises a low frequency voltage application transformer 7 for applying a low frequency voltage for measuring insulation resistance to the next side. One output on the secondary side of the low frequency voltage applying transformer 7 is connected to one output on the secondary side of the transformer 1 in the circuit to be measured, and a current transformer 8 is installed in the middle of the connection line. . The calibration measurement resistor (Rt) 14 is connected between one output on the secondary side of the transformer 1 to which the low frequency voltage application transformer 7 is connected and the current transformer 8.
[0003]
In the insulation resistance measuring apparatus of FIG. 4, first, in a normal insulation resistance measurement operation, a low frequency voltage signal generated by a low frequency oscillator 5 as a low frequency voltage application means is amplified by an amplifier 6 and applied with a low frequency voltage. Further, a low frequency voltage signal is applied from the low frequency voltage application transformer 7 between the measured circuit and the ground. The current transformer 8 detects the displacement of the current of the low frequency voltage applied between the circuit to be measured and the ground, amplifies it by the amplifier 9, removes the commercial AC component by the low frequency pass filter 10, and analog / Digital converter 11 converts it into a digital quantity and outputs it to CPU 12 that controls each part of the insulation resistance measuring device. In the CPU 12, when the detection result of the current transformation detecting means receives a value converted into a digital quantity and exceeds a preset input value, the measured insulation resistances (R1) 3 and (R2) It is determined that the value of 4 does not satisfy the set value, and the alarm display lamp 13 is turned on by energizing to notify the operator of the insulation resistance measuring device that the insulation resistance value is insufficient. When performing an accuracy test on this conventional insulation resistance measuring device, first, the breaker 2 of the circuit to be measured is cut to avoid the influence of the insulation resistances (R1) 3 and (R2) 4 of the circuit to be measured. Thus, the low frequency voltage signal applied to the secondary side of the circuit to be measured is prevented from flowing. Then, a measurement resistor (Rt) 14 having a predetermined insulation resistance value is inserted between the connection end connecting the circuit to be measured and the insulation resistance measuring device and the ground, and the low frequency generated by the low frequency oscillator 5 is inserted. A frequency voltage signal is applied to the measurement resistor (Rt) 14 via the low frequency voltage application transformer 7, and the current transformer 8 detects the current flowing through the current transformer 8 and sends it to the CPU 12. The CPU 12 determines whether or not the current transformation is greater than or equal to a preset value that is input in advance. If the current transformation determination result is greater than or equal to the preset value, the CPU 12 prompts the accuracy tester by lighting the alarm display lamp 13. The insulation resistance measuring device is notified that it is operating normally (maintaining accuracy). That is, the accuracy tester can confirm that the insulation resistance measuring device is operating normally by turning on the alarm display lamp 13 of the insulation resistance measuring device during the accuracy test. In addition, by making the measurement resistance (Rt) 14 a variable resistance, the resistance level of the measurement resistance when the alarm display lamp 13 is lit can be known. Therefore, the resistance level of the measurement resistance and the value indicated by the insulation resistance measuring device. It is possible to confirm the accuracy in detail.
[0004]
[Problems to be solved by the invention]
However, in the accuracy test of the conventional insulation resistance measuring device, in order to avoid the influence of the insulation resistance of the circuit to be measured, the circuit to be measured is cut with a breaker and the insulation resistance measuring device is further connected to the circuit to be measured. Since it is necessary to insert a measuring resistor between the connecting end for connection and the ground, the work is complicated, and the connecting end is connected to the potential of the circuit to be measured (generally a high potential that is dangerous to the human body). In many cases, the work of inserting and removing the measuring resistor is a dangerous work. In view of the above problems, an object of the present invention is to provide an insulation resistance measuring apparatus that can perform an accuracy test with a simple operation without the need for an operation involving a risk of insertion or removal of a measurement resistor.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, in the insulation resistance measuring apparatus according to the first aspect of the present invention, low-frequency voltage applying means for applying a low-frequency voltage to the circuit to be measured, and the low-frequency voltage flow through the circuit. A current transformer for extracting a current leakage component, and an insulation resistance measuring device for measuring an insulation resistance of a circuit under measurement based on a value extracted by the current transformer,
An accuracy test circuit for applying the low frequency voltage directly to the current transformer through a measurement resistor when performing an accuracy test of the insulation resistance measuring device, and the accuracy as an output destination of the low frequency voltage application means An applied voltage switching means for selecting either a test circuit or the measured circuit;
The output destination of the low frequency voltage application means is set on the measured circuit side during operation of measuring the insulation resistance of the measured circuit by the applied voltage switching unit, and the low frequency voltage is used when performing an accuracy test. It is characterized by switching the output destination of the application means to the accuracy test circuit side, and it becomes possible to perform an accuracy test just by switching the applied voltage switching means, so there is no need for work involving the danger of insertion or removal of measurement resistance, etc. The accuracy test can be carried out with simple work.
[0006]
In the insulation resistance measuring device of the present invention according to claim 2, the accuracy test circuit includes a low frequency voltage application unit installed in the current transformer to directly apply the low frequency voltage to the current transformer, A measurement resistance circuit unit including the measurement resistance, at least,
The measurement resistance circuit unit is located between the low-frequency voltage application unit and the application voltage switching unit, and is configured to be detachable via a connector, and the accuracy test circuit unit is used only during an accuracy test. Can be connected.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the insulation resistance measuring apparatus according to the first embodiment of the present invention. In FIG. 1, parts having the same functions as those in the conventional apparatus shown in FIG. The insulation resistance measuring device of the embodiment of FIG. 1 is also connected to the circuit to be measured in the same manner as the conventional insulation resistance measuring device. The electric circuit to be measured has a transformer 21. Note that a breaker capable of cutting both ends on the secondary side of the transformer 21 is not particularly required. 1 differs from the conventional insulation resistance measuring apparatus of FIG. 4 in that a switching relay 38 as an applied voltage switching means is provided at the output terminal of the low frequency oscillator, and one output terminal of the switching relay 38 is provided. Is connected to the low-frequency applying transformer 27 via the amplifier 26, while the other output end is connected to the resistor Ro35 via the amplifier 34, and a line connecting the other end of the resistor Ro35 and the ground is a current transformer. It is in the place penetrated by 28. In the insulation resistance measuring apparatus having the configuration shown in FIG. 1, first, when performing a normal insulation resistance measurement operation, the low frequency voltage signal generated by the low frequency oscillator 25 as the low frequency voltage application means is changed over to the switching relay control line 37. Is input to the switching destination amplifier 26 determined by the switching relay 38 that has received the instruction from the CPU 32 transmitted by. The low frequency voltage signal amplified by the amplifier 26 is applied between the measured circuit and the ground by the low frequency voltage application transformer 27. The current transformer 28 detects the displacement of the current of the low frequency voltage applied between the circuit to be measured and the ground, amplifies it by the amplifier 29, removes the commercial AC component by the low frequency pass filter 30, and analog / A digital value is converted by the digital converter 31 and output to the CPU 32 that controls each part of the insulation resistance measuring device. In the CPU 32, when the detection result of the above-described current transformation detecting means receives a value converted into a digital quantity by the analog / digital converter 31, and the digital quantity exceeds a preset value inputted in advance, measurement is performed. Since the values of the insulation resistances (R1) 23 and (R2) 24 that have been set do not satisfy the set values, it is confirmed that the insulation resistance value is insufficient by energizing and lighting the alarm display lamp 33. Notify the operator.
[0008]
When performing an accuracy test in the insulation resistance measurement device according to the first embodiment, first, an accuracy test performer of the insulation resistance measurement device presses an accuracy test start switch 36 installed in the CPU 32. Then, the CPU 32 generates a signal for switching the switching relay 38 and switches the switching relay 38 to the circuit on the accuracy test side via the switching relay control line 37. Then, the low frequency voltage signal generated by the low frequency oscillator 25 is amplified by the amplifier 34 and applied to the measuring resistor (Ro) 35, and the current displacement in that case is detected by the current transformer 28. The current detected by the current transformer 28 is amplified by the amplifier 29, the commercial AC component is removed by the low frequency filter 31, converted into a digital quantity by the analog / digital converter 31, and input to the CPU 32. In the CPU 32, if the input digital quantity is equal to or greater than a preset set value, the measured resistance (Ro) is a resistance value lower than a predetermined insulation resistance value, so that the current value Io is equal to or greater than the set value. In other words, since the alarm display lamp 13 is lit, it can be confirmed that the alarm display lamp 13 operates normally (maintaining accuracy). The measured resistance (Ro) in this case is a value at which the resistance value calculated by the CPU 32 from the current value Io detected by the current transformer 28 satisfies the insulation resistance defined by the Ministry of International Trade and Industry notification and safety standards. It is set in advance so that the value becomes slightly lower than the above. For example, when the insulation resistance measuring device of the present embodiment is mass-produced in a factory, the current value Io detected by the current transformer 28 of the insulation resistance measuring device at the time of factory shipment is adjusted to the above-described value. To ship. As described above, this embodiment enables an accuracy test only by switching the applied voltage switching device by pressing an accuracy test start switch installed in the insulation resistance measuring device, so that the measurement resistor can be inserted or removed. It is possible to provide an insulation resistance measuring apparatus that can perform an accuracy test with a simple operation without requiring a dangerous operation.
[0009]
FIG. 2 is a block diagram showing a configuration of an insulation resistance measuring apparatus according to the second embodiment of the present invention. In FIG. 2, parts having the same functions as those of the insulation resistance measuring apparatus according to the first embodiment shown in FIG. In FIG. 2, a low frequency voltage output connector 43 is installed at the output of the amplifier 26, and a connector 44 that can be connected to the connector 43 is installed at the input of the low frequency voltage application transformer 27. The current transformer 28 is provided with a low frequency voltage application unit 49 for applying a low frequency voltage, and connectors 47 and 48 are provided at the end of the low frequency voltage application unit 49. The measurement resistance circuit section 40 is provided with connectors 42, 45, 46 for connecting to the connectors 43, 47, 48, and has a measurement resistance (Ro) 35 and a transformer 41 inside . In the present embodiment, the connectors 42 to 44 are the first connector means, and the connectors 45 to 48 are the second connector means.
[0010]
In the second embodiment, when measuring the insulation resistance, the connector 43 and the connector 44 are connected, and the measurement resistance circuit unit 40 is not connected. When performing an accuracy test, the connectors 47 and 48 provided at the end of the low frequency voltage application unit 49 and the connectors 45 and 46 provided in the measurement resistance circuit unit 40 are connected to each other, and further, a low frequency voltage output is performed. Connector 43 and connector 42 installed in measurement resistance circuit section 40 are connected. When performing an accuracy test in the second embodiment, the accuracy tester who performs the test during the accuracy test first removes the connector 43 connected to the connector 44 and is provided on the measurement resistance circuit unit 40. Connect with the connector 42. Next, the connectors 45 and 46 provided on the measurement resistance circuit unit 40 and the connectors 47 and 48 provided at the end of the low frequency voltage application unit 49 are connected to each other. Thereafter, the accuracy test start switch 36 connected to the CPU 32 is pressed. The basic operation in the second embodiment is the same as that shown in the first embodiment, but the measurement resistance circuit unit 40 is provided separately as in this embodiment, and the connectors 42, 43, 45 to 48 are provided. By connecting the measurement resistance circuit unit 40 to the insulation resistance measurement device, the following special actions and effects different from those of the first embodiment can be obtained.
[0011]
When the accuracy test circuit is built in the insulation resistance measuring apparatus as in the first embodiment, the operator who performs the test at the time of the accuracy test has an effect that the test can be easily performed only by switching the switch. Once the accuracy test is performed, the measurement resistance circuit unit 40 is kept on standby in the insulation resistance measurement device without being energized until the next accuracy test is performed. It will be left in place until the next accuracy test. In an electronic device, it is inevitable that aging (deterioration) will occur in the components inside the device. Therefore, when performing an accuracy test such as once every six months or once using the first embodiment, There is a possibility that the accuracy test result will be distorted due to the deterioration of the amplifier 34 or the measurement resistor 35 or the like . In the case of the second embodiment, since the measurement resistance circuit unit 40 is separate, it is confirmed that there is no deterioration in the set value of the measurement resistance 35 in the measurement resistance circuit unit 40 alone. The measurement resistance circuit unit 40 can be connected to the connectors 42, 43, 45 to 48 to perform an accuracy test. Therefore, in the case of the second embodiment, it is considered suitable for accurate periodic calibration such as once every several months or once a year. Further, as described above, in the second embodiment, the accuracy test can be performed only by changing the application destination of the voltage by executing the connection changing process of the connectors 42 to 48, and thus the same as in the first embodiment. In addition, it is possible to provide an insulation resistance measuring apparatus that can perform an accuracy test with a simple operation without the need for an operation involving the risk of insertion or removal of the measurement resistor.
[0012]
FIG. 3 is a block diagram showing the configuration of the insulation resistance measuring apparatus according to the third embodiment of the present invention. In FIG. 3 as well, parts having the same functions as those of the insulation resistance measuring apparatus of the second embodiment shown in FIG. In FIG. 3, a switching relay 50 as an applied voltage switching means is provided at the output end of the low frequency oscillator 25 in the insulation resistance measuring device (the output side end of the amplifier 26). 51 is installed, and the output for measuring the insulation resistance in the switching relay 50 is connected to the low-frequency applying transformer 27. In the present embodiment, the connector 51 and the connector 42 are first connector means, and the connectors 45 to 48 are second connector means. The basic operation in the third embodiment is the same as that shown in the second embodiment. However, by providing the switching relay 50 as in this embodiment, the following differences from the second embodiment are provided. Such special actions and effects can be obtained. When performing an accuracy test in the third embodiment, an accuracy tester who performs the test during the accuracy test first connects the connector 51 and the connector 42 provided on the measurement resistance circuit unit 40. Next, the connectors 45 and 46 provided on the measurement resistance circuit unit 40 and the connectors 47 and 48 provided at the end of the low frequency voltage application unit 49 are connected to each other. Thereafter, the accuracy test start switch 36 connected to the CPU 32 is pressed. Then, the CPU 32 generates a signal for switching the switching relay 50 and switches the switching relay 50 to a circuit on the accuracy test side via a switching relay control line (not shown). Therefore, when changing from the connection state at the time of insulation resistance measurement to the connection state at the time of the accuracy test, or conversely, when changing from the connection state of the accuracy test to the connection state at the time of measurement of the insulation resistance, as in the second embodiment. Since it is not necessary to reconnect the connector at the output end of the low-frequency oscillator 25 and the connection state can be changed by switching the switching relay 50, an accuracy test can be easily performed. As described above, also in the third embodiment, the accuracy test can be performed only by changing the application destination of the voltage by the connection changing process of the connectors 42 to 48, and thus, similarly to the first embodiment. It is possible to provide an insulation resistance measuring apparatus that can perform an accuracy test by a simple operation without requiring a work that involves a risk of insertion or removal of a measurement resistor. In each of the above-described embodiments (first to third embodiments), the accuracy test start switch 36 is installed so as to be connected to the CPU 32. However, the switch does not necessarily have to be connected to the CPU. The alarm display lamp 33 may be operated directly, or another notification device may be used.
[0013]
【The invention's effect】
As described above, according to the present invention of claim 1, since the accuracy test can be performed only by switching the applied voltage switching device, there is no need for a risky operation such as insertion or removal of the measuring resistor, and the accuracy can be achieved with a simple operation. It is possible to provide an insulation resistance measuring device capable of performing a test. According to the second aspect of the present invention, it is possible to provide an insulation resistance measuring apparatus capable of performing an accuracy test without being affected by aging deterioration by performing connector connection with the accuracy test section as a separate body. According to the third aspect of the present invention, the accuracy test in the insulation resistance measuring apparatus according to the second aspect can be more easily performed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an insulation resistance measuring apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an insulation resistance measuring apparatus according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an insulation resistance measuring apparatus according to a third embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a conventional insulation resistance measuring apparatus.
[Explanation of symbols]
1, 2, 41, ... Transformer, 2 ... Breaker, 3, 4, 23, 24 ... Insulation resistance, 5, 25 ... Low frequency oscillator, 6, 9, 26, 29, 34 ...・ Amplifiers 7 and 27... Low frequency voltage application transformers 8 and 28... Current transformers 10 and 30... Low frequency pass filters 11 and 31. 32 ... CPU, 13, 33 ... alarm indicator lamp, 14,35 ... measurement resistance, 36 ... accuracy test start switch, 37 ... switching relay control line, 38,50 ... switching relay, 40 ... measurement resistance circuit part, 42～48,51 ... connector

Claims (2)

Comprising a low-frequency voltage applying means for applying a voltage of low frequency to the measured circuit, and a current transformer to extract the leakage component of the current flowing through the electric path by the voltage of the low frequency, was extracted by the current transformer In an insulation resistance measuring device that measures the insulation resistance of the circuit under test based on the value,
An accuracy test circuit for applying the low frequency voltage directly to the current transformer through a measurement resistor when performing an accuracy test of the insulation resistance measuring device, and the accuracy as an output destination of the low frequency voltage application means An applied voltage switching means for selecting either a test circuit or the measured circuit ; and
The output destination of the low frequency voltage application means is set on the measured circuit side during operation of measuring the insulation resistance of the measured circuit by the applied voltage switching unit, and the low frequency voltage is used when performing an accuracy test. An insulation resistance measuring apparatus , wherein the output destination of the applying means is switched to the accuracy test circuit side . The accuracy test circuit includes at least a low frequency voltage application unit installed in the current transformer to directly apply the low frequency voltage to the current transformer, and a measurement resistance circuit unit including the measurement resistance. And
2. The insulation resistance according to claim 1, wherein the measurement resistance circuit unit is positioned between the low-frequency voltage application unit and the application voltage switching unit and is configured to be detachable via a connector. measuring device.

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