Insulation resistance monitoring device

Abstract

To provide an insulation resistance monitoring device preventing power for operating a load device from being easily input to an application type measuring instrument for monitoring insulation resistance of a measurement object including the load device.SOLUTION: A measurement object includes: AC electric wires 11 to 13 for supplying three-phase power; and a load device 14 operated by the three-phase power. One ends of three resistors 24a to 24c are individually connected to the three AC electric wires 11 to 13, and the other ends of the resistors 24a to 24c are composited mutually. An application type measuring instrument 30 connected to the other ends monitors insulation resistance of a measurement object. Since the three resistors 24a to 24c have the same resistance value, the total current generated in each of the three resistors 24a to 24c by three-phase power becomes nearly 0 A, and voltage composited in the other end sides of the resistors 24a to 24c also becomes nearly 0 V. Therefore, inputting current and voltage based on three-phase power to the application type measuring instrument 30 is made difficult.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention , total An application-type measuring instrument that monitors the insulation resistance of an object being measured Check that the device is working properly The present invention relates to an insulation resistance monitoring device. [Background technology]

[0002] Patent Document 1 describes an application-type measuring instrument that monitors the insulation resistance of an object to be measured, which includes a set of multiple power lines that supply power from upstream to downstream, and a load device that operates with the power supplied from the power lines. This application-type measuring instrument is connected to a grounded (earthed) part and the object to be measured, and applies a voltage between the grounded part and the object to be measured. This voltage is divided by the insulation resistance of the object to be measured and a reference resistor inside the application-type measuring instrument, and the application-type measuring instrument calculates the insulation resistance of the object to be measured with respect to the grounded part by measuring the voltage applied to the reference resistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-173176 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for an insulation resistance monitoring device that can verify the normal operation of an application-type measuring instrument.

[0005] The present invention Responding to this demand It was made for the purpose of ,mark Additive Measuring Instrument Check that the device is working properly The object of the present invention is to provide an insulation resistance monitoring device that can [Means for solving the problem]

[0006] To achieve this object, the insulation resistance monitoring device of the present invention comprises: A measurement object; Grounded ground part WithThe insulation resistance between the The measurement object and the ground portion are connected to each other. The voltage application type measuring instrument includes: The measurement object , excluding the insulation resistance of the object to be measured and the connection to the ground via the application type measuring instrument In a state where the ground part is not connected, The measurement object and the ground portion, a current generated according to the insulation resistance of the measurement object or a voltage converted from the current is measured. the measurement unit includes a voltage application unit that applies a positive voltage to the ground unit, a measurement unit that is connected to the object to be measured and that measures a current or voltage generated on the object to be measured by the voltage applied by the voltage application unit, a standard resistor having a predetermined resistance value that is arranged between the measurement unit and the ground unit, and a switching unit that switches the connection between the measurement unit and the object to be measured to a connection between the measurement unit and the ground unit via the standard resistor, and in a state where the measurement unit is switched by the switching unit to a connection between the measurement unit and the ground unit via the standard resistor, the measurement unit measures a current or voltage generated in response to the resistance value of the standard resistor, instead of a current or voltage generated in response to the insulation resistance of the object to be measured, based on the voltage applied by the voltage application unit.

[0007]

[0008] Note that "grounded part" includes not only parts that are electrically connected to the earth (such as the housing of a load device), but also the earth itself. Furthermore, connection to a large conductor that is not connected to the earth, such as the frame of a vehicle, ship, or airplane, is also called "grounding," and a grounded "grounded part" includes large conductors such as frames and things connected to those conductors. Effect of the Invention

[0009] According to the insulation resistance monitoring device of claim 1, Measurement target The applied measuring instruments connected to the and ground parts are , total Measurement object excluding the insulation resistance of the object being measured and the connection to the ground via the application-type measuring instrument. When not connected to the ground, Measurement target A voltage is applied between the resistor and the ground. ,mark A current corresponding to the insulation resistance of the object to be measured that is connected to the additive type measuring instrument is generated, and this current is input to the application type measuring instrument. By measuring this input current or the voltage converted from this current with the application type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured.

[0010] When a positive voltage is applied to the ground by the voltage application unit of the application-type measuring instrument, the measuring unit connected to the measurement object measures the current or voltage generated on the measurement object side by the voltage applied by the voltage application unit. The connection between this measuring unit and the measurement object is switched by the switching unit to a connection between the measuring unit and the ground portion via the standard resistor. In this switched state, the measuring unit measures the current or voltage generated according to the resistance value of the standard resistor based on the voltage applied by the voltage application unit, instead of the current or voltage generated according to the insulation resistance of the measurement object. As a result, for example, the normal operation of the application-type measuring instrument can be confirmed by comparing the resistance value calculated from the measured current or voltage with the resistance value of the predetermined standard resistor.

[0011]

[0012] According to the insulation resistance monitoring device of claim 2, in addition to the effects achieved by the insulation resistance monitoring device of claim 1, the following effects are achieved. The switching unit includes a plurality of switches that individually open and close between the measurement unit and the object to be measured, and between the measurement unit and the ground via the standard resistor. The application-type measuring instrument includes a prohibition means that prohibits the control to close the switches when the measurement unit measures a current or voltage by applying a positive voltage to the ground by the voltage application unit while controlling all of the plurality of switches to be open. This reduces the possibility of the application-type measuring instrument or the object to be measured being damaged by an unintended voltage.

[0013]

[0014] According to the insulation resistance monitoring device of claim 3, in addition to the effects achieved by the insulation resistance monitoring device of claim 1 or 2, the following effects are achieved. The calculation means of the application type measuring instrument calculates the resistance value of the standard resistor from the measurement result of the measuring unit in a state where the switching unit switches the connection between the measuring unit and the ground unit via the standard resistor. The comparison means of the application type measuring instrument compares the resistance value calculated by the calculation means with the original resistance value of the standard resistor that is determined in advance. If the two values ​​are almost the same as a result of this comparison, it can be determined that the application type measuring instrument is operating normally.

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] [Brief description of the drawings]

[0024] [Figure 1] 1 is a circuit diagram showing a schematic diagram of an insulation resistance monitoring device and an electric circuit of a measurement object in a first embodiment. [Diagram 2] FIG. 2 is a block diagram showing the electrical configuration of an application-type measuring instrument. [Diagram 3] 13 is a flowchart of a periodic measurement process executed by a CPU of the application-type measuring instrument. [Figure 4] 1 is a graph showing changes over time in insulation resistance measurement results and predictions for the future. [Diagram 5] FIG. 11 is a circuit diagram showing a schematic diagram of an insulation resistance monitoring device and an electric circuit of an object to be measured according to a second embodiment. [Figure 6] FIG. 11 is a block diagram showing the electrical configuration of an application-type measuring instrument in a second embodiment. [Figure 7] 13 is a flowchart of a periodic measurement process in the second embodiment. [Figure 8]FIG. 11 is a circuit diagram showing a schematic diagram of an insulation resistance monitoring device and an electric circuit of an object to be measured according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Preferred embodiments will now be described with reference to the accompanying drawings. First, an insulation resistance monitoring device 20 and a measurement object in a first embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram showing a schematic diagram of an electrical circuit of the insulation resistance monitoring device 20 and the measurement object. The measurement object includes a set of three AC electric wires 11, 12, and 13 that constitute a three-phase three-wire AC circuit, and a load device 14 connected to the set of three AC electric wires 11-13.

[0026] The AC electric wires 11-13 are power supply lines that supply three-phase power (power for load) from an upstream pole transformer or the like to a downstream load device 14. Three-phase power is three-phase AC power, and three-phase AC is three single-phase AC of the same voltage flowing through the AC electric wires 11-13, each shifted in phase by 120°.

[0027] The load device 14 is an electric circuit that operates with three-phase power supplied from a set of AC electric wires 11-13. An example of the load device 14 is a three-phase induction motor. The load device 14 is housed in a housing 14a that is class D grounded (earthed) via a ground wire 18. The load device 14 is directly connected to the AC electric wires 11-13 within the housing 14a.

[0028] The ground wire 18 is an electric wire connected to a ground electrode embedded in the earth. The ground wire 18 connected to the housing 14a, the isolation transformers 21 and 22, and the voltage application type measuring instrument 30, which will be described later, may be the same electric wire or may be separate electric wires connected to each other via the earth.

[0029] The insulation resistance monitoring device 20 is for monitoring the insulation resistance between a grounding part such as the ground wire 18, the housing 14a, or the earth and an object to be measured. The insulation resistance monitoring device 20 includes insulating transformers 21, 22 disposed midway along the AC electric wires 11-13, composite resistance units 23, 24 connected to the AC electric wires 11-13, and an application-type measuring instrument 30 connected between the composite resistance units 23, 24 and the ground wire 18.

[0030] An isolation transformer 22 is disposed on the AC electric wires 11-13 downstream of the isolation transformer 21. The isolation transformer 21 includes a primary winding 21a connected to the AC electric wires 11-13 upstream of its own arrangement position, a secondary winding 21b connected to the AC electric wires 11-13 downstream of its own arrangement position, an iron core (not shown) around which the primary winding 21a and the secondary winding 21b are wound, and a housing 21c that houses the primary winding 21a, the secondary winding 21b, and the iron core.

[0031] Similarly, the isolation transformer 22 includes a primary winding 22a, a secondary winding 22b, an iron core (not shown), and a housing 22c. Note that the housings 21c and 22c are connected to a ground wire 18 and grounded in order to allow leakage currents and the like generated within the isolation transformers 21 and 22 to escape to the earth.

[0032] Here, of the AC electric wires 11 to 13, the portions connected to the primary winding 21a of the isolation transformer 21 are referred to as upstream wires 11a to 13a, the portions connecting the secondary winding 21b of the isolation transformer 21 and the primary winding 22a of the isolation transformer 22 are referred to as intermediate wires 11b to 13b, and the portions connected to the secondary winding 22b of the isolation transformer 22 are referred to as downstream wires 11c to 13c.

[0033] The isolation transformer 21 transmits three-phase power from the upstream lines 11a-13a to the intermediate lines 11b-13b by electromagnetic induction while insulating the upstream lines 11a-13a from the intermediate lines 11b-13b. Similarly, the isolation transformer 22 transmits three-phase power from the intermediate lines 11b-13b to the downstream lines 11c-13c by electromagnetic induction while insulating the intermediate lines 11b-13b from the downstream lines 11c-13c.

[0034] In addition, by making the number of turns of the primary winding 21a and the secondary winding 21b different, the isolation transformer 21 can transform the voltage on the primary winding 21a side and transmit it to the secondary winding 21b side. However, the number of turns of the primary winding 21a and the number of turns of the secondary winding 21b may be the same, and the voltage may not be transformed by the isolation transformer 21. Similarly, the isolation transformer 22 may or may not perform the transformation.

[0035] Further, the intermediate wires 11b to 13b and the downstream wires 11c to 13c on the downstream side of the isolation transformers 21, 22 are all maintained in a state of being unconnected to a grounded portion such as the ground wire 18. In other words, the downstream sides of the isolation transformers 21, 22 are not grounded to type B.

[0036] The combined resistor section 23 includes a resistor 23a having one end connected to the intermediate line 11b, a resistor 23b having one end connected to the intermediate line 12b, and a resistor 23c having one end connected to the intermediate line 13b. The other ends of these three resistors 23a to 23c are combined with each other. The other end of this combined resistor 23a to 23c is connected to the application-type meter 30 by a combined electric wire 23d.

[0037] The three resistors 23a to 23c have the same resistance value. As a result, a graph of the time change in the current generated in each of the three resistors 23a to 23c by the three-phase power supplied from the intermediate lines 11b to 13b is similar to a graph of the time change in the voltage of the intermediate lines 11b to 13b (a graph in which the phases of single-phase AC of the same voltage are shifted by 120°).

[0038] Therefore, at any time, the sum of the currents flowing through resistors 23a to 23c is approximately 0 A. Thus, the current flowing through composite electric wire 23d in which these currents are combined is approximately 0 A, and the voltage combined in composite electric wire 23d is also approximately 0 V. The reason why the currents and voltages based on the three-phase power are approximately 0 is that when the balance of the voltages between intermediate wires 11b to 13b is lost, a small amount of current and voltage may also be generated in composite electric wire 23d.

[0039] In addition, "the same resistance value" includes cases where the resistance values ​​differ within a range of ±5%. Even if the resistance values ​​of the three resistors 23a to 23c differ slightly, a small amount of current and voltage may be generated in the composite electric wire 23d.

[0040] Similar to the combining resistor unit 23, the combining resistor unit 24 includes resistors 24a to 24c, one end of which is connected to each of the downstream lines 11c to 13c. The other ends of the combined resistors 24a to 24c are connected to the application-type meter 30 by a combining electric wire 24d. Since the resistors 24a to 24c have the same resistance value, the current flowing through the combining electric wire 24d based on the three-phase power is approximately 0 A, and the voltage combined by the combining electric wire 24d is also approximately 0 V.

[0041] In this way, by connecting application-type meter 30 to AC electric wires 11-13 via composite resistance units 23, 24, it is possible to make it difficult for the current and voltage based on the three-phase power to be input to application-type meter 30. As a result, it is possible to eliminate the need to disconnect application-type meter 30 from AC electric wires 11-13 when supplying three-phase power, and to eliminate the need for an electromagnetic switch or the like for connecting and disconnecting it.

[0042] Furthermore, even when the electromagnetic switch is provided, if the electromagnetic switch cannot be opened due to a malfunction such as welding, the combining resistance units 23, 24 can make it difficult for the current and voltage based on the three-phase power to be input to the application-type meter 30. Therefore, by using the combining resistance units 23, 24, the application-type meter 30 can be kept connected to the AC electric wires 11-13 even when three-phase power is being supplied.

[0043] The application-type measuring instrument 30 has a terminal E connected to the ground wire 18, a terminal a connected to the intermediate wires 11b to 13b via the composite wire 23d and the composite resistance section 23, and a terminal b connected to the downstream wires 11c to 13c via the composite wire 24d and the composite resistance section 24.

[0044] The application-type measuring instrument 30 applies a voltage between the terminal E and the terminal a or b, thereby generating a current according to the insulation resistance of the measurement object (AC electric wires 11-13, load device 14) connected to the terminal a or b. The application-type measuring instrument 30 measures the voltage converted from this current, and calculates and monitors the insulation resistance from the voltage.

[0045] The current generated in the AC electric wires 11-13 by the application of the voltage by the application-type measuring instrument 30 does not flow beyond the insulating transformers 21, 22. Therefore, when the application-type measuring instrument 30 applies a voltage between the terminals E and a, it can measure the voltage generated according to the insulation resistance of the intermediate wires 11b-13b, the secondary winding 21b, and the primary winding 22a (hereinafter referred to as "measurement object a") connected to the terminal a among the measurement objects when the application-type measuring instrument 30 applies a voltage between the terminals E and a terminal. Similarly, when the application-type measuring instrument 30 applies a voltage between the terminals E and b, it can measure the voltage generated according to the insulation resistance of the downstream wires 11c-13c, the secondary winding 22b, and the load device 14 (hereinafter referred to as "measurement object b") connected to the terminal b among the measurement objects.

[0046] In this way, the insulation resistance monitoring device 20 can monitor the insulation resistance of the measurement objects a and b downstream of the isolation transformers 21 and 22, which are located upstream of the connection position of the terminals a and b, by using the isolation transformers 21 and 22. Also, the insulation resistance monitoring device 20 can monitor the insulation resistance of the measurement object a upstream of the isolation transformer 22, by using the isolation transformer 22 located downstream of the connection position of the terminal a.

[0047] Conventionally, in order to partially monitor the insulation resistance of a measurement object including the AC electric wires 11-13, it was necessary to disconnect the AC electric wires 11-13 midway. However, in the insulation resistance monitoring device 20 of this embodiment, by providing the insulating transformers 21 and 22, it is possible to partially monitor the insulation resistance of the measurement object without disconnecting the AC electric wires 11-13 midway. In other words, in the insulation resistance monitoring device 20, it is not necessary to disconnect the AC electric wires 11-13 and stop the supply of three-phase power in order to monitor the insulation resistance of the measurement object.

[0048] Specifically, a method for calculating the insulation resistance of the measurement object a (intermediate lines 11b-13b, etc.) connected to terminal a using the application-type measuring instrument 30 will be described. First, when a predetermined voltage V0 (e.g., 250-1000V) is applied between terminal E and terminal a, a current corresponding to the insulation resistance of the measurement object a is generated. The application-type measuring instrument 30 converts this current into a voltage V1 using a reference resistor 40 (see FIG. 2) provided inside the application-type measuring instrument 30, and measures this voltage V1.

[0049] This will be explained from another perspective. Voltage V0 applied between terminal E and terminal a by application-type measuring instrument 30 is divided mainly among the insulation resistance of measurement object a, resistors 23a-23c, and reference resistor 40. Application-type measuring instrument 30 measures voltage V1 applied to reference resistor 40 out of this divided voltage.

[0050] Here, if the insulation resistance value of the measurement object a is R1, the resistance value of the combined resistance unit 23 (the combined value of the resistance values ​​of the three resistors 23a, 23b, and 23c) is R2, and the resistance value of the reference resistor 40 is R3, then the formula V1=V0×R1 / (R1+R2+R3) holds. Because the voltage V0 and the resistance values ​​R2 and R3 are known in advance, the insulation resistance value R1 of the measurement object a can be calculated by measuring the voltage V1.

[0051] Similarly, when measuring the insulation resistance of the measurement object b (downstream lines 11c-13c, etc.) connected to terminal b, the application-type measuring instrument 30 applies a voltage V0 between terminal E and terminal b, measures a voltage V1 across the reference resistor 40, and calculates an insulation resistance value R1 of the measurement object b from the measurement result. In this case, the resistance value of the combined resistance unit 24 (a combined value of the resistance values ​​of the three resistors 24a, 24b, 24c) is R2.

[0052] The application-type measuring instrument 30 is operated by the storage battery 25, not by the three-phase power supplied from the AC power lines 11-13. Furthermore, the application-type measuring instrument 30 measures a voltage corresponding to the insulation resistance by using a voltage applied by itself (power of the storage battery 25), and therefore can monitor the insulation resistance of the measurement objects a and b even when three-phase power is not being supplied.

[0053] Furthermore, to measure the insulation resistance of the measurement objects a and b using the application-type measuring instrument 30, the measurement objects a and b need to be disconnected from the grounded parts such as the ground wire 18. However, the measurement objects a and b including the intermediate wires 11b-13b and the downstream wires 11c-13c are maintained in a state of being disconnected from the ground wire 18 due to the absence of type B grounding. Therefore, when performing measurement using the application-type measuring instrument 30, the work or process of disconnecting the measurement objects a and b from the ground wire 18 can be eliminated. This simplifies the measurement using the application-type measuring instrument 30.

[0054] When disconnecting the AC electric wires 11-13 from the ground wire 18 during measurement with the application-type measuring instrument 30, it is preferable to disconnect them after stopping the supply of three-phase power through the AC electric wires 11-13 in order to prevent malfunction of the load equipment 14, etc. However, since there is no need for such disconnection, there is no need to stop the supply of three-phase power through the AC electric wires 11-13 during measurement with the application-type measuring instrument 30.

[0055] In addition, the combined resistance units 23, 24 make it difficult for the current and voltage based on the three-phase power to be input to the application-type measuring instrument 30. As a result, even when the load device 14 is operating on three-phase power, the application-type measuring instrument 30 can measure a voltage corresponding to the insulation resistance of the measurement objects a, b while suppressing the effect of the three-phase power on the measurement results. Therefore, the insulation resistance monitoring device 20 can accurately monitor the insulation resistance of the measurement objects a, b even when the load device 14 is operating.

[0056] Next, the control of the application-type measuring instrument 30 will be described in more detail with reference to Figures 2 to 4. Figure 2 is a block diagram showing the electrical configuration of the application-type measuring instrument 30. The application-type measuring instrument 30 has a CPU 31, a flash ROM 32, and a RAM 33 which is a memory for rewritably storing various work data, flags, etc. when the program of the CPU 31 is executed, and these are each connected to an input / output port 35 via a bus line 34.

[0057] Further connected to the input / output port 35 are a communication device 36, a measurement unit 37, a voltage application unit 38, and a switching unit 39, which are connected to the external control device 26. The external control device 26 is a device that analyzes the measurement results of the insulation resistance of the measurement object obtained from the insulation resistance monitoring device 20 (voltage application type measuring instrument 30) and controls the operation of the load device 14 and the like.

[0058] The CPU 31 is a calculation device that controls each part connected by a bus line 34. The flash ROM 32 is a rewritable non-volatile memory that stores programs executed by the CPU 31, fixed value data, etc., and is provided with an application monitoring program 32a. When the application monitoring program 32a is executed by the CPU 31, the periodic measurement process of FIG. 3 is performed.

[0059] The measuring unit 37 is a device that measures the voltage applied to a reference resistor 40 built into the application-type measuring instrument 30. The reference resistor 40 is a load having a predetermined resistance value that serves as a reference, with one end connected to the switching unit 39 and the other end connected to a ground 41. The voltage application unit 38 is a device that applies a positive DC voltage from terminal E to the ground wire 18, using the ground 41 as a reference potential.

[0060] The switching unit 39 is a circuit that connects one of the measurement objects a, b connected to the terminals a, b to the reference resistor 40 and the measurement unit 37, making it possible to calculate the insulation resistance of the measurement object a or b connected to the measurement unit 37.

[0061] The electrical path between terminal a and the measuring unit 37 is connected openably and closably by a switch SW1, and the electrical path between terminal b and the measuring unit 37 is connected openably and closably by a switch SW2. The switches SW1 and SW2 are switches that open and close an electrical circuit in response to an instruction from the CPU 31, and maintain an open state when not energized.

[0062] Furthermore, the switching unit 39 includes a standard resistor 42 connected to an electric wire branched off from between the terminal E and the voltage application unit 38, and a switch SW3 that opens and closes the standard resistor 42 and the measurement unit 37. The standard resistor 42 is a load having a predetermined resistance value. The switch SW3 may be provided between the standard resistor 42 and the electric wire branched off from between the terminal E and the voltage application unit 38.

[0063] Next, the periodic measurement process executed by the CPU 31 of the application-type measuring instrument 30 will be described with reference to Fig. 3. Fig. 3 is a flowchart of the periodic measurement process of the application-type measuring instrument 30. The periodic measurement process of the application-type measuring instrument 30 is executed periodically (e.g., every 10 minutes) while the power of the application-type measuring instrument 30 is turned on.

[0064] In the periodic measurement process of the application-type measuring instrument 30, first, n=1 is set to calculate the insulation resistance of the measurement object a (S11). Next, the switch SWn (n: integer) is closed (S12). In the process of S12 immediately after the process of S11 where n=1 is set, the switch SW1 is closed to connect the measurement object a to the measuring unit 37.

[0065] As a result, a circuit for calculating the insulation resistance of the measurement object a is formed, and the voltage application unit 38 applies a positive voltage from terminal E to the ground wire 18 (S13). Next, it is confirmed whether a predetermined time has elapsed since the application of the voltage (S14), and if the predetermined time has not elapsed (S14: No), the measurement value of the voltage generated according to the insulation resistance of the measurement object a is not stable, so the process of S14 is looped.

[0066] On the other hand, if a predetermined time has passed since the application of the voltage (S14: Yes), it is confirmed whether n≦2 (S15) to confirm whether it is time to calculate the insulation resistance of the measurement object a or b. If n≦2 (S15: Yes), it is time to calculate the insulation resistance of the measurement object a or b, so the voltage applied to the reference resistor 40 is measured by the measurement unit 37, and the insulation resistance of the measurement object a is calculated from the measurement result as described above (S16).

[0067] Next, the measurement result, the measurement target (measurement target a in the first process after the process of S11), and the measurement date and time are transmitted to the external control device 26 (S18). The external control device 26 accumulates and analyzes the measurement result, as will be described later with reference to FIG.

[0068] After the process of S18, switch SWn is opened for the next measurement (S19). In the first process after the process of S11, switch SW1 is opened in S19 to separate the measurement target a from the measurement unit 37. To confirm this separation, it is confirmed that the voltage corresponding to the insulation resistance is no longer detected by the measurement unit 37 (S20).

[0069] If no voltage is detected in the process of S20 (S20: Yes), it is determined that the switch SW1 that was instructed to open in the process of S19 was opened without any problem. Therefore, the voltage application by the voltage application unit 38 is terminated (S21), and n=n+1 is set for the next measurement (S22).

[0070] Next, it is confirmed whether n≧4 (S23), and if n<4 (S23: No), there are still unmeasured items remaining, so the processes from S12 onwards are executed again. Specifically, if n=2 in the process of S22, the switch SW2 is opened and closed in the processes of S12 and S19, and the insulation resistance of the measurement object b is calculated in the process of S16.

[0071] Furthermore, if n=3 in the process of S22, the switch SW3 is closed in the process of S12, thereby connecting the voltage application unit 38 to the measurement unit 37 and the reference resistor 40 via the standard resistor 42. Furthermore, since n>2 in the process of S15 (S15: No), the process of S17 is executed instead of the process of S16.

[0072] In the process of S17, the voltage applied to the standard resistor 40 is measured by the measurement unit 37, and the resistance value of the standard resistor 42 is calculated from the measurement result (S17). Since the voltage V0 applied by the voltage application unit 38 is divided between the standard resistor 42 and the reference resistor 40, if the resistance value of the standard resistor 42 is R4, the voltage applied to the standard resistor 40 is V1, and the resistance value of the standard resistor 40 is R3, then the formula V1=V0×R4 / (R3+R4) holds. By substituting each value into this formula, the resistance value R4 of the standard resistor 42 is calculated.

[0073] The measurement result calculated in the process of S17 is sent to the external control device 26 in the process of S18, with the standard resistor 42 as the measurement target. The external control device 26 compares the resistance value R4 calculated by the application-type measuring instrument 30 with the predetermined original resistance value of the standard resistor 42, and if the two are almost identical, it can be determined that the application-type measuring instrument 30 is operating normally.

[0074] Also, a signal for calibrating the application-type measuring instrument 30 can be sent from the external control device 26 to the application-type measuring instrument 30 so that the resistance value R4 calculated by the application-type measuring instrument 30 approaches the predetermined resistance value of the standard resistor 42. Note that the determination of normal operation and calibration may be performed by the application-type measuring instrument 30 instead of the external control device 26.

[0075] After the process of S18 where n=3, switch SW3 is opened in the process of S19, and the processes of S20 to S23 are executed. In the process of S23, n=4 due to the process of S22 just before (S23: Yes), and all measurements have been completed, so the periodic measurement process is terminated.

[0076] Furthermore, regardless of the value of n, if the measurement unit 37 detects a voltage in the process of S20 (S20: No), it can be determined that the switch SWn instructed to open in the process of S19 did not actually open due to welding, etc. In this case, error information that the switch SWn did not open is transmitted to the external control device 26 (S24), the application of voltage by the voltage application unit 38 is terminated (S25), and the periodic measurement process is terminated.

[0077] For example, if switch SW1 does not open due to welding, causing an error, and the periodic measurement process is not terminated, and the process from S12 onwards is executed again to close switch SW2 to measure the insulation resistance of measurement object b, measurement object a and measurement object b will be connected. If three-phase power is supplied or voltage is applied by voltage application unit 38 in this state, the application-type measuring instrument 30 and each part of measurement objects a and b may be damaged by the unintended voltage.

[0078] In contrast, if an error occurs in the process of S20 such that a voltage is detected (S20: No), the periodic measurement process is terminated, thereby preventing a plurality of measurement objects a, b from being connected to each other via the switching unit 39. As a result, it is possible to reduce the possibility that each part of the application-type measuring instrument 30 or the measurement objects a, b will break down due to an unintended voltage.

[0079] Furthermore, the periodic measurement process may be controlled not to be executed until the error is resolved, which further reduces the possibility that the application-type measuring instrument 30 or each part of the measurement objects a and b will be damaged by an unintended voltage.

[0080] 4, an analysis of the measurement result of the insulation resistance of the measurement object a by the application-type measuring instrument 30 will be described among the analyses executed by the external control device 26. The same analysis is also performed on the measurement result of the insulation resistance of the measurement object b.

[0081] As shown in Fig. 4, the external control device 26 generates and displays a graph with the past insulation resistance measurement results on the vertical axis and the date and time on the horizontal axis for the measurement object a. In the graph in Fig. 4, the change over time of the past measurement results (actual values) is shown by a solid line, and the change over time of future measurement results (predicted values) is shown by a two-dot chain line, which is an extension of a straight line that approximates the actual measurement values ​​using the least squares method. The graph in Fig. 4 also shows a threshold value at which degradation of the insulation resistance is suspected by a dashed line.

[0082] When the past measurement result is below the threshold value, the external control device 26 notifies the administrator of the external control device 26 that the insulation resistance of the measurement object a is suspected to have deteriorated. At this time, the notification may be given to the worker or operator who operates the load device 14. Note that when the insulation resistance is measured by the application-type measuring instrument 30, the temperature and humidity at the time of measurement may also be acquired, and the insulation resistance may be corrected or the threshold value may be changed based on this information.

[0083] In the external control device 26, the date and time when the future measurement result will be equal to or lower than the threshold value is predicted based on the time-dependent change in the future measurement result (predicted value) and the threshold value, and the predicted date and time is displayed in the graph of Fig. 4. Therefore, the manager of the external control device 26 can plan a schedule for maintenance of the measurement object a based on the date and time when the future measurement result will be equal to or lower than the threshold value, and can also plan the ordering of devices and parts that need to be replaced.

[0084] Next, a second embodiment will be described with reference to Fig. 5 to Fig. 7. In the first embodiment, a case where the downstream side of the insulating transformer 22 is not grounded by type B has been described. In contrast, in the second embodiment, a case where the downstream side of the insulating transformer 22 is grounded by type B has been described. Note that the same parts as those in the first embodiment are given the same reference numerals, and the following description will be omitted.

[0085] 5 is a circuit diagram showing a schematic diagram of an insulation resistance monitoring device 60 and an electric circuit of an object to be measured in the second embodiment. The object to be measured in the second embodiment is the same as the object to be measured in the first embodiment except that the upstream side of the isolation transformer 22 is omitted.

[0086] The insulation resistance monitoring device 60 includes an isolation transformer 22, a type B grounding wire 66 that connects the downstream side of the isolation transformer 22 to type B ground, an electromagnetic switch 67 provided on the type B grounding wire 66, a composite resistance unit 24, and an application-type measuring instrument 61 connected between the composite resistance unit 24 and the grounding wire 18.

[0087] The class B ground wire 66 is an electric wire branched off from the downstream line 13c in the vicinity of the isolation transformer 22, and is connected to the ground wire 18 of the housing 22c of the isolation transformer 22. This provides class B grounding to the downstream side of the isolation transformer 22. Note that the class B ground wire 66 may be directly connected to the earth to ground the downstream line 13c.

[0088] The electromagnetic switch 67 is a normally closed type switch that opens and closes the class B ground wire 66. When the electromagnetic switch 67 is not energized, the electromagnetic switch 67 closes (energizes) the class B ground wire 66 to ground the downstream line 13c, and when the electromagnetic switch 67 is energized, it opens (cuts off) the class B ground wire 66 to switch the downstream line 13c to an ungrounded state.

[0089] As shown in Fig. 6, the application-type measuring instrument 61 differs from the application-type measuring instrument 30 (see Fig. 2) in the first embodiment in that the switching unit 39 and terminal b are omitted, and terminal a connected to the combined resistance unit 24 is directly connected to the measuring unit 37 and the reference resistor 40. Furthermore, the flash ROM 32 of the application-type measuring instrument 61 is provided with an application monitoring program 62 that is different from that in the first embodiment. The rest of the configuration of the application-type measuring instrument 61 is the same as that of the application-type measuring instrument 30 in the first embodiment.

[0090] An application-type measuring instrument 61, a load device 14, and an electromagnetic switch 67 are connected to the external control device 26. The external control device 26 transmits the operating state of the load device 14 and the open / close state of the electromagnetic switch 67 to the application-type measuring instrument 61, and transmits a switching signal from the application-type measuring instrument 61 to the electromagnetic switch 67.

[0091] Next, the processing when the application monitoring program 62 is executed by the CPU 31 of the application-type measuring instrument 61 will be described with reference to Fig. 7. Fig. 7 is a flowchart of the periodic measurement processing executed by the CPU 31 by the application monitoring program 62. The periodic measurement processing of the application-type measuring instrument 61 is executed periodically (for example, every 10 minutes) while the power of the application-type measuring instrument 61 is turned on.

[0092] The periodic measurement process of the application-type measuring instrument 61 first checks whether the power supply to the load device 14 is off (S41) to determine whether it is possible to open the electromagnetic switch 67. If the electromagnetic switch 67 is opened to unground the downstream line 13c when the power supply to the load device 14 is on, for example, noise generated when the load device 14 is operating cannot be released to the ground from the class B ground wire 66, which may cause the load device 14 to malfunction.

[0093] When the power supply of the load device 14 is off (S41: Yes), opening the electromagnetic switch 67 will not cause the load device 14 to malfunction, so the electromagnetic switch 67 is opened (S42). Specifically, in the process of S42, a signal to open the electromagnetic switch 67 is sent to the electromagnetic switch 67 via the external control device 26, and the electromagnetic switch 67 opens when it receives the signal.

[0094] After the process of S42, the processes of S13, S14, S16, S18, and S21 are executed as in the first embodiment, the insulation resistance of the measurement object connected to terminal a is calculated, and is transmitted to the external control device 26. Next, the electromagnetic switch 67 is closed to ground the downstream line 13c again (S43) so that the load device 14 operates normally when the power is turned on, and the periodic measurement process is terminated.

[0095] On the other hand, in the process of S41, if the power supply of the load device 14 is on (S41: No), the electromagnetic switch 67 is left closed to prevent the load device 14 from malfunctioning when the electromagnetic switch 67 is opened, and the periodic measurement process is terminated. If the voltage application unit 38 applies a voltage to the ground wire 18 with the electromagnetic switch 67 left closed, a current corresponding to the voltage flows directly from the ground wire 18 and the class B ground wire 66 to the downstream wire 13c without passing through the insulation resistance, and the current is input to the measurement unit 37. In this case, there is a risk that the insulation resistance of the measurement object cannot be accurately measured from the measurement result of the measurement unit 37.

[0096] In contrast, the application-type meter 61 measures the voltage with the measurement unit 37 in a state where the electromagnetic switch 67 is open and no three-phase power is supplied to the load device 14, so that the voltage corresponding to the insulation resistance of the object to be measured can be accurately measured by the measurement unit 37. As a result, the application-type meter 61 can accurately calculate the insulation resistance of the object to be measured from the measurement result of the measurement unit 37.

[0097] Next, a third embodiment will be described with reference to Fig. 8. In the first and second embodiments, the insulation resistance monitoring devices 20, 60 that monitor the insulation resistance of a measurement object including three-phase three-wire AC electric wires 11-13 have been described. In contrast, in the third embodiment, an insulation resistance monitoring device 90 that monitors the insulation resistance of a measurement object that supplies DC power from a battery 81 to a load device 86 will be described. Note that the same parts as those in the first and second embodiments are given the same reference numerals and the following description will be omitted.

[0098] 8 is a circuit diagram showing a schematic diagram of an insulation resistance monitoring device 90 and an electric circuit of an object to be measured in the third embodiment. The object to be measured in the third embodiment includes a battery 81 that outputs DC power (power for load), a positive wire 84 connected to the positive electrode of the battery 81, a negative wire 85 connected to the negative electrode of the battery 81, and a load device 86 that operates with the DC power supplied from the battery 81 via the positive wire 84 and the negative wire 85. Examples of the object to be measured include automobiles, industrial vehicles, railroad cars, aircraft, ships, and other electric devices that use electricity as a power source.

[0099] The battery 81 is a power source that outputs DC power of a predetermined voltage (for example, about 400 V) and has an internal resistance 82. However, the resistance value of this internal resistance 82 is low enough to allow the battery 81 to be regarded as a conductor similar to an electric wire, relative to the insulation resistance of the object to be measured.

[0100] The positive wire 84 and the negative wire 85 are a pair of power lines for supplying DC power from the upstream battery 81 to the downstream load device 86. The load device 86 is an electric circuit that operates with the DC power. The load device 86 is housed in a housing 86a that is D-grounded via a ground wire 18. When the object to be measured is a vehicle or the like, the term "grounding" refers to connection to a large conductor such as the frame of the vehicle, and the large conductor does not necessarily have to be connected to the earth.

[0101] The insulation resistance monitoring device 90 includes an application-type measuring instrument 30 connected between the negative electrode wire 85 and the ground wire 18. Terminal E of the application-type measuring instrument 30 is connected to the ground wire 18, and terminal a is connected only to the negative electrode wire 85. The application-type measuring instrument 30 applies a voltage between terminals E and a, measures a voltage corresponding to the insulation resistance of the measurement object connected to terminal a, and calculates the insulation resistance from the voltage.

[0102] As described above, since the battery 81 is regarded as a low-resistance conductor, the application-type measuring instrument 30 can measure a voltage corresponding to the insulation resistance of not only the negative wire 85, the battery 81, and the load device 86 among the measurement objects, but also the positive wire 84, even if the terminal a is not directly connected to the positive wire 84. Therefore, the insulation resistance monitoring device 90 can monitor the insulation resistance of the positive wire 84, the negative wire 85, the battery 81, and the load device 86 based on the measurement results of the application-type measuring instrument 30.

[0103] In addition, the potential of negative line 85 relative to ground line 18 is close to 0V regardless of whether the two are connected or not. Therefore, even while DC power is being supplied from battery 81 to load device 86, it is possible to prevent a current or voltage based on the DC power from being input from negative line 85 to application-type meter 30. As a result, it is possible to eliminate the need to disconnect application-type meter 30 from negative line 85 when DC power is being supplied from battery 81, and to eliminate the need for an electromagnetic switch for connecting and disconnecting it. Therefore, application-type meter 30 can be kept connected to negative line 85 even when DC power is being supplied.

[0104] In some cases, the negative wire 85 is grounded by connecting it to the ground wire 18 or a grounded portion such as the vehicle frame to prevent noise from the load device 86, but in this embodiment, the negative wire 85 is maintained in a disconnected state from the ground wire 18. This makes it possible to eliminate the need for a task or process (for example, opening and closing the electromagnetic switch 67 as in the second embodiment) of disconnecting the negative wire 85 from the ground wire 18 when making a measurement using the application-type measuring instrument 30. This simplifies the measurement using the application-type measuring instrument 30.

[0105] Furthermore, since there is no need to disconnect the negative wire 85 from the ground wire 18 when making a measurement with the application-type measuring instrument 30, there is no need to stop the supply of DC power through the negative wire 85 and the positive wire 84. In addition, since a current or voltage based on DC power is unlikely to be input to the application-type measuring instrument 30 connected to the negative wire 85, even when the load device 86 is operating on DC power, the application-type measuring instrument 30 can measure a voltage corresponding to the insulation resistance of the object to be measured while suppressing the effect of the DC power on the measurement results. Therefore, the insulation resistance monitoring device 90 can accurately monitor the insulation resistance of the object to be measured even when the load device 86 is operating.

[0106] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-mentioned embodiments, and it can be easily assumed that various improvements and modifications are possible within the scope of the present invention. For example, the voltage applied by the voltage application unit 38, the magnitude of the output voltage of the battery 81, the interval at which the periodic measurement process is performed, the number of the load devices 14, 86, etc. may be appropriately changed. In addition, the external control device 26 may be omitted, and the control performed by the external control device 26 may be performed by the voltage application type measuring devices 30, 61.

[0107] In the above embodiment, the application type measuring instruments 30 and 61 have been described as applying a voltage from the voltage application unit 38 to generate a current according to the insulation resistance of the object to be measured, and then measuring the voltage converted from that current with the measurement unit 37. Alternatively, the reference resistor 40 may be omitted and the measurement unit 37 may be an ammeter, so that the measurement unit 37 may measure the current generated according to the insulation resistance of the object to be measured when the voltage application unit 38 applies a voltage.

[0108] Furthermore, the present invention is not limited to the case where a positive voltage is applied from voltage application unit 38 to ground wire 18 via terminal E. For example, a positive voltage may be applied from voltage application unit 38 to terminal a or b, and a current or voltage generated in response to the insulation resistance due to the application of that voltage may be input from terminal E to application-type measuring instrument 30, 61. In this case, the current or voltage generated in response to the insulation resistance is measured by measuring unit 37 connected to terminal E.

[0109] However, it is preferable to apply a positive voltage to terminal E (ground wire 18) from voltage application unit 38. In this case, the insulation resistance measurement result is more likely to be lower than when a positive voltage is applied to terminals a and b, making it easier to determine the deterioration of the insulation resistance at an early stage.

[0110] In the above first embodiment, the case where terminals a and b are connected to objects to be measured that are insulated from each other has been described. The number of terminals may be appropriately increased according to the number of objects to be measured that are insulated from each other, and the multiple terminals may be selectively connected to the measurement unit 37 and the reference resistor 40 by the switching unit 39. Furthermore, the switching unit 39 and multiple terminals may be applied to the above second and third embodiments. Also, the switching unit 39 may be omitted, and multiple application-type measuring instruments provided with only the terminal a may be connected to multiple objects to be measured that are insulated from each other, respectively.

[0111] In the above embodiment, the insulating transformers 21, 22 are disposed in the AC electric wires 11-13, but these insulating transformers 21, 22 may be omitted. In this case, when monitoring the insulation resistance of a part of the AC electric wires 11-13 with the application-type measuring instruments 30, 61, it is sufficient to separate the part of the AC electric wires 11-13 from the other parts and to separate the part from a ground part such as the ground wire 18.

[0112] Moreover, the combined resistance units 23 and 24 in the above embodiment may be omitted, and one of the AC electric wires 11 to 13 may be directly connected to the terminals a and b. In this case, however, in order to disconnect the AC electric wires 11 to 13 from the measurement unit 37 when three-phase power is supplied, it is preferable to provide switches SW1 and SW2 or an electromagnetic switch between them.

[0113] In the second embodiment, the B-type ground wire 66 branches off from the downstream wire 13c, but the B-type ground wire 66 may branch off from the downstream wire 11c or the downstream wire 12c. In addition, one of the intermediate wires 11b to 13b in the first embodiment, one of the downstream wires 11c to 13c, or the negative electrode wire 85 in the third embodiment may be connected to the ground wire 18 by the B-type ground wire 66 in the second embodiment. In this case, the measurement is performed by the application-type measuring instrument 30 with the electromagnetic switch 67 provided on the B-type ground wire 66 open. Conversely, in the second embodiment, the B-type ground wire 66 may be omitted.

[0114] In the above embodiment, the case has been described where normal operation of the application-type measuring instrument 30 is confirmed by measuring the resistance value of the standard resistor 42 with the application-type measuring instrument 30. For purposes other than this confirmation of normal operation, the switch SW3 may be closed to connect each part of the measuring unit 37 and the switching unit 39 to the ground line 18 via the standard resistor 42. In this case, residual voltage and electrostatic capacitance parasitic in the application-type measuring instrument 30 can be discharged using the standard resistor 42.

[0115] In the above embodiment, the electromagnetic switch 67 is a normally closed type switch, but a normally open type switch that opens when de-energized and closes when energized may be used for the electromagnetic switch 67. Also, a latch type switch that maintains an open / closed state when de-energized and opens / closes in response to an electrical signal may be used for the electromagnetic switch 67. <Other> Japanese Patent Application Publication No. 2017-173176 describes an application-type measuring instrument that monitors the insulation resistance of a measurement object that includes a set of multiple power lines that supply power from upstream to downstream and a load device that operates with the power supplied from the power lines. This application-type measuring instrument is connected to a grounded (earthed) part and the measurement object, and applies a voltage between the grounded part and the measurement object. This voltage is divided by the insulation resistance of the measurement object and a reference resistor inside the application-type measuring instrument, and the application-type measuring instrument calculates the insulation resistance of the measurement object relative to the grounded part by measuring the voltage applied to the reference resistor. However, in conventional technology, there was a risk that power to operate the load equipment of the object to be measured would be input to an application-type measuring instrument connected to the object to be measured in order to monitor the insulation resistance of the object to be measured. The present technical idea has been made to solve the above-mentioned problems, and aims to provide an insulation resistance monitoring device that can make it difficult for power for operating a load device to be input to an application-type measuring instrument. <Means> The insulation resistance monitoring device of technical idea 1 monitors the insulation resistance between a grounded part and a measurement object that includes a set of three AC wires that form a three-phase three-wire circuit and supply three-phase power from upstream to downstream, and a load device that operates with the three-phase power supplied from the set of three AC wires. The device comprises three resistors having the same resistance value, one end of which is individually connected to the three AC wires and the other ends of which are combined together, and an application-type measuring instrument that is connected to the combined other ends of the three resistors and to the ground part, respectively, and measures a current generated in response to the insulation resistance of the measurement object, or a voltage obtained by converting that current, by applying a voltage between the other ends and the ground part while the measurement object to which the resistors are connected is disconnected from the ground part. The insulation resistance monitoring device of technical idea 2 is the insulation resistance monitoring device of technical idea 1, in which all of the three AC wires to which the resistors are connected are maintained in a non-connected state with the ground portion. The insulation resistance monitoring device of technical idea 3 is an insulation resistance monitoring device of technical idea 1 or 2, which is provided with an upstream transformer that is arranged on the three AC electric wires upstream of the position where one end of each of the three resistors is connected, and transmits the three-phase power from the upstream side to the downstream side by electromagnetic induction while insulating the AC electric wires on the upstream and downstream sides of the arrangement position. The insulation resistance monitoring device of technical idea 4 is an insulation resistance monitoring device of any of technical ideas 1 to 3, which is provided with a downstream transformer that is arranged on the three AC electric wires downstream of the position where one end of each of the three resistors is connected, and transmits the three-phase power from the upstream side to the downstream side by electromagnetic induction while insulating the AC electric wires on the upstream and downstream sides of the arrangement position. The insulation resistance monitoring device of technical idea 5 is an insulation resistance monitoring device of any of technical ideas 1 to 4, wherein the application-type measuring instrument comprises a voltage application unit that applies a positive voltage to the grounded portion, a measurement unit that is connected to the other end and measures a current or voltage generated at the other end by the voltage applied by the voltage application unit, a standard resistor having a predetermined resistance value that is arranged between the measurement unit and the grounded portion, and a switching unit that switches the connection between the measurement unit and the other end to a connection between the measurement unit and the grounded portion via the standard resistor, and when the measurement unit is switched by the switching unit to a connection between the measurement unit and the grounded portion via the standard resistor, the measurement unit measures a current or voltage generated in response to the resistance value of the standard resistor, instead of a current or voltage generated in response to the insulation resistance of the object to be measured, based on the voltage applied by the voltage application unit. The insulation resistance monitoring device of Technical Idea 6 monitors the insulation resistance between a grounded part and a measurement object including a battery that outputs DC power, a positive wire connected to the positive electrode of the battery, a negative wire connected to the negative electrode of the battery, and a load device that operates with DC power supplied from the battery via the positive and negative wires, and includes an application-type measuring instrument that is connected to the negative wire and the ground part while being disconnected from the positive wire, and that measures the current generated in response to the insulation resistance of the measurement object, or the voltage converted from that current, by applying a voltage between the negative wire and the ground part while the negative wire is disconnected from the ground part. The insulation resistance monitoring device of technical concept 7 is the insulation resistance monitoring device of technical concept 6, wherein the negative electrode wire is maintained in a state of being disconnected from the ground portion. <Effects> According to the insulation resistance monitoring device of Technical Idea 1, one end of each of three resistors is connected to three AC electric wires, and the other ends of the three resistors are combined together. An application-type measuring instrument, which is connected to the combined other end and a ground, applies a voltage between the combined other end and the ground while the object to be measured (load equipment, AC electric wire) to which the resistors are connected is not connected to the ground. This application of voltage generates a current according to the insulation resistance of the object to be measured, which is connected to the application-type measuring instrument via the resistors, and this current is input to the application-type measuring instrument. By measuring this input current or a voltage converted from this current with the application-type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured. Since the three resistors provided between the three AC wires and the application-type meter have the same resistance, the total current generated in each of the three resistors by the three-phase power supplied from the three-phase three-wire AC wire is approximately 0 A, and the combined voltage at the other end of the resistors is also approximately 0 V. This makes it difficult for the current and voltage based on the three-phase power for operating the load equipment to be input to the application-type meter. Note that "the same resistance value" includes cases where the resistance values ​​differ within a range of ±5%. The insulation resistance monitoring device of Technical Idea 2 has the following effect in addition to the effect of the insulation resistance monitoring device of Technical Idea 1. Since all three AC electric wires to which resistors are connected are maintained in a state of being disconnected from the ground, the task or process of disconnecting those AC electric wires from the ground when measuring with an application-type measuring instrument is not required. This simplifies the measurement using the application-type measuring instrument. When disconnecting the AC wire from the ground during measurement with an application-type measuring instrument, it is preferable to disconnect the wire after stopping the supply of three-phase power that operates the load equipment in order to prevent malfunction of the load equipment. However, since there is no need to disconnect the wire, there is no need to stop the supply of three-phase power during measurement with an application-type measuring instrument. In addition, since the three resistors make it difficult for the current and voltage based on the three-phase power to be input to the application-type measuring instrument, the application-type measuring instrument can measure the current or voltage corresponding to the insulation resistance of the measurement object even while the load equipment is operating with three-phase power. Therefore, the insulation resistance monitoring device can monitor the insulation resistance of the measurement object even while the load equipment is operating. The insulation resistance monitoring device of Technical Idea 3 has the following effect in addition to the effects of the insulation resistance monitoring device of Technical Idea 1 or 2. An upstream transformer is disposed on the three AC electric wires upstream of the positions where one ends of the three resistors are connected. This upstream transformer transmits three-phase power from the upstream side to the downstream side by electromagnetic induction while insulating the AC electric wires on the upstream side and downstream side of its own position. Therefore, the application-type measuring instrument can measure the current or voltage generated by applying a voltage according to the insulation resistance of the measurement object downstream of the upstream transformer. As a result, the insulation resistance monitoring device can monitor the insulation resistance downstream of the upstream transformer without having to cut off the AC electric wire midway to stop the supply of three-phase power in order to monitor the insulation resistance of a part of the AC electric wire. The insulation resistance monitoring device of Technical Idea 4 has the following effect in addition to the effect of any one of the insulation resistance monitoring devices of Technical Ideas 1 to 3. A downstream transformer is disposed on the three AC electric wires downstream of the position where one end of each of the three resistors is connected. This downstream transformer transmits three-phase power from the upstream side to the downstream side by electromagnetic induction while insulating the AC electric wires on the upstream side and downstream side of its own position. Therefore, the application-type measuring instrument can measure the current or voltage generated by applying a voltage according to the insulation resistance of the measurement object on the upstream side of the downstream transformer. As a result, the insulation resistance monitoring device can monitor the insulation resistance on the upstream side by providing a downstream transformer without having to cut off the AC electric wire midway to stop the supply of three-phase power in order to monitor the insulation resistance of a part of the AC electric wire. According to the insulation resistance monitoring device of Technical Concept 5, in addition to the effects of the insulation resistance monitoring device of any one of Technical Concepts 1 to 4, the following effects are achieved. When a positive voltage is applied to the ground by the voltage application unit of the application type measuring instrument, the measurement unit connected to the other end of the combined three resistors measures the current or voltage generated on the other end of the resistor by the voltage applied by the voltage application unit. The connection between this measurement unit and the other end of the resistor is switched by the switching unit to a connection between the measurement unit and the ground via the standard resistor. In this switched state, the measurement unit measures the current or voltage generated according to the resistance value of the standard resistor based on the voltage applied by the voltage application unit, instead of the current or voltage generated according to the insulation resistance of the measurement object. As a result, for example, the normal operation of the application type measuring instrument can be confirmed by comparing the resistance value calculated from the measured current or voltage with the resistance value of the predetermined standard resistor. According to the insulation resistance monitoring device of Technical Idea 6, an application-type measuring instrument, which is disconnected from the positive wire but connected to the negative wire and ground, applies a voltage between the negative wire and ground while the negative wire is disconnected from the ground. This application of voltage generates a current corresponding to the insulation resistance of the object to be measured connected to the application-type measuring instrument, and this current is input to the application-type measuring instrument. By measuring this input current or a voltage converted from this current with the application-type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured. Since the battery is considered to be a low-resistance conductor, the positive and negative wires connected via the battery are considered to be a single wire. This allows the insulation resistance monitoring device to measure the current or voltage according to the insulation resistance of not only the negative wire but also the positive wire with an application-type meter, and to monitor the insulation resistance of the positive and negative wires. In addition, since the potential of the negative wire with respect to the ground is close to 0V, even while DC power is being supplied to the load device, it is difficult for the current or voltage based on that DC power to be input from the negative wire to the application-type measuring instrument. The insulation resistance monitoring device of Technical Idea 7 has the following effect in addition to the effect of the insulation resistance monitoring device of Technical Idea 6. Since the negative wire is maintained in a state of being disconnected from the ground, the task or process of disconnecting the negative wire from the ground when measuring with an application-type measuring instrument is not required. This simplifies the measurement with the application-type measuring instrument. When disconnecting the negative wire from the ground during measurement with an application-type measuring instrument, it is preferable to disconnect the negative wire from the ground after stopping the supply of DC power that operates the load equipment in order to prevent malfunction of the load equipment. However, since there is no need to disconnect the negative wire, there is no need to stop the supply of DC power during measurement with an application-type measuring instrument. In addition, since it is difficult for a current or voltage based on DC power to be input to an application-type measuring instrument connected to the negative wire, the application-type measuring instrument can measure a current or voltage corresponding to the insulation resistance of the object to be measured even while the load equipment is operating with DC power. Therefore, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured even while the load equipment is operating. [Explanation of symbols]

[0116] 11,12,13 AC wire (Part of the object to be measured) 14,86 Load equipment (Part of the object to be measured) 14a, 21c, 22c, 86a Housing (grounding part) 18 Ground wire (ground part) 20,60,90 Insulation resistance monitoring device Place 3 0,61 Applied Measuring Instrument 37 Measurement section 38 Voltage application section 39 Switching section 42 Standard Resistor 81 Battery (Part of the object to be measured) 84 Positive Wire (Part of the object to be measured) 85 Negative Wire (Part of the object to be measured) SW1, SW2, SW3 switches

Claims

1. An insulation resistance monitoring device for monitoring insulation resistance between a measurement object and a grounded part, comprising: an application-type measuring instrument connected to the object to be measured and the ground portion, The applied type measuring instrument is A voltage is applied between the object to be measured and the ground in a state where the object to be measured is not connected to the ground except for the insulation resistance of the object to be measured and the connection to the ground via the application-type measuring instrument, thereby measuring a current generated according to the insulation resistance of the object to be measured, or a voltage obtained by converting the current, A voltage application unit that applies a positive voltage to the ground unit; a measurement unit that is connected to the object to be measured and measures a current or a voltage generated on the object to be measured by a voltage applied by the voltage application unit; a standard resistor having a predetermined resistance value, the standard resistor being disposed between the measurement unit and the ground unit; a switching unit that switches a connection between the measurement unit and the object to be measured to a connection between the measurement unit and the ground unit via the standard resistor, an insulation resistance monitoring device characterized in that, when the switching unit switches the connection between the measurement unit and the ground unit via the standard resistor, the measurement unit measures a current or voltage generated in response to the resistance value of the standard resistor, instead of a current or voltage generated in response to the insulation resistance of the measurement object, based on the voltage applied by the voltage application unit.

2. The switching unit includes a plurality of switches for individually opening and closing connections between the measurement unit and the object to be measured, and between the measurement unit and the ground unit via the standard resistor, The insulation resistance monitoring device according to claim 1, characterized in that the application-type measuring instrument is provided with a prohibition means for prohibiting control to close the switches when the measuring unit measures a current or voltage by applying a positive voltage to the grounding unit by the voltage application unit while controlling all of the multiple switches to be open.

3. The voltage application type measuring instrument, a calculation means for calculating a resistance value of the standard resistor from a measurement result of the measurement unit in a state in which the measurement unit and the ground unit are switched to a connection via the standard resistor by the switching unit; 3. The insulation resistance monitoring device according to claim 1, further comprising a comparison means for comparing the resistance value calculated by the calculation means with a predetermined original resistance value of the standard resistor.

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