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 relates to an insulation resistance monitoring device capable of confirming the normal operation of an applied type measuring instrument for monitoring the insulation resistance of a measurement object.

Background Art

[0002] Patent Document 1 describes an applied type measuring instrument for monitoring the insulation resistance of a measurement object, which includes a set of a plurality of power lines for supplying power from upstream to downstream and a load device operated by the power supplied from the power lines. This applied type measuring instrument is connected to a grounded (earthed) grounding part and the measurement object, and applies a voltage between the grounding part and the measurement object. This voltage is divided by the insulation resistance of the measurement object and a reference resistance inside the applied type measuring instrument, and the applied type measuring instrument calculates the insulation resistance of the measurement object with respect to the grounding part by measuring the voltage applied to the reference resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a need for an insulation resistance monitoring device capable of confirming the normal operation of an applied type measuring instrument.

[0005] The present invention has been made to meet this requirement, and an object thereof is to provide an insulation resistance monitoring device capable of confirming the normal operation of an applied type measuring instrument.

Means for Solving the Problems

[0006] To achieve this object, the insulation resistance monitoring device of the present invention monitors the insulation resistance between a measurement object and a grounded grounding portion, and includes an applied type measuring instrument connected to the measurement object and the grounding portion respectively. The applied type measuring instrument applies a voltage between the measurement object and the grounding portion with the measurement object being disconnected from the grounding portion except for the connection through the insulation resistance of the measurement object and the applied type measuring instrument, and measures the current generated according to the insulation resistance of the measurement object or the voltage obtained by converting the current. The device includes a voltage application unit that applies a positive voltage to the grounding portion, Electricity a measurement unit that measures a current or a voltage, a standard resistor having a predetermined resistance value disposed between the measurement unit and the grounding portion, In a first state where the grounding part is not connected to the measuring part via the standard resistor the measurement unit to the measurement object be connection caused, and through the standard resistor and the measurement unit to the grounding portion be connection caused, a second state a switching unit that switches the connection, and the measurement unit measures, based on the voltage applied by the voltage application unit, a current or a voltage generated according to the resistance value of the standard resistor instead of the current or the voltage generated according to the insulation resistance of the measurement object in a state switched by the switching unit. In the first state, measure the current or voltage generated according to the insulation resistance of the object to be measured by the voltage applied by the voltage application part by the switching unit The second In this state, instead of the current or voltage generated according to the insulation resistance of the measurement object based on the voltage applied by the voltage application unit, the measurement unit measures the current or voltage generated according to the resistance value of the standard resistor.

[0007] In addition, the insulation resistance monitoring device of the present invention monitors the insulation resistance between an object to be measured and a grounded grounding part, and includes an applied type measuring instrument connected to the object to be measured and the grounding part respectively. The applied type measuring instrument disconnects the object to be measured from the grounding part except for the connection between the insulation resistance of the object to be measured and the grounding part via the applied type measuring instrument, and applies a voltage between the object to be measured and the grounding part to measure the current generated according to the insulation resistance of the object to be measured or the voltage obtained by converting the current. The device includes a voltage application part for applying a positive voltage to the grounding part, a measuring part connected to the object to be measured for measuring the current or voltage generated on the object to be measured side by the voltage applied by the voltage application part, a standard resistor having a predetermined resistance value disposed between the measuring part and the grounding part, and a switching part for switching the connection between the measuring part and the object to be measured to the connection between the measuring part and the grounding part via the standard resistor. The measuring part measures the current or voltage generated according to the resistance value of the standard resistor instead of the current or voltage generated according to the insulation resistance of the object to be measured based on the voltage applied by the voltage application part in a state where the connection between the measuring part and the grounding part is switched by the switching part via the standard resistor

[0008] Note that the "grounding portion" includes not only a portion electrically connected to the ground (for example, the housing of a load device), but also the ground itself. Further, connecting to a large conductor such as a vehicle frame, a ship hull, or an aircraft frame that is not connected to the ground is also referred to as "grounding", and the grounded "grounding portion" includes a large conductor such as a frame and those connected to the conductor.

Advantages of the Invention

[0009] According to the insulation resistance monitoring device described in claim 1, the applied-type measuring instrument connected to the object to be measured and the grounding part applies a voltage between the object to be measured and the grounding part with the object to be measured being in a state of being disconnected from the grounding part, excluding the connection between the insulation resistance of the object to be measured and the grounding part through the applied-type measuring instrument. Due to the application of this voltage, a current corresponding to the insulation resistance of the object to be measured connected to the applied-type measuring instrument is generated, and this current is input into the applied-type measuring instrument. By measuring this input current or the voltage obtained by converting this current with the applied-type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured.

[0010] In a first state where the object to be measured is connected to the measuring part without connecting the grounding part to the measuring part via the standard resistor When a positive voltage is applied to the grounding part by the voltage application part of the applied-type measuring instrument , measure The measuring part measures the object to be measured by the voltage applied by the voltage application part generated according to the insulation resistance of to measure current or voltage . Switch by the conversion part From the first state through the standard resistance and the measuring part to the grounding part be connection caused, a second state is switched. In the state thus switched, the measuring part measures, based on the voltage applied by the voltage application part, the current or voltage generated according to the resistance value of the standard resistance instead of the current or voltage generated according to the insulation resistance of the object to be measured. Thereby, for example, by comparing the resistance value calculated from the measured current or voltage with the resistance value of the predetermined standard resistance, the normal operation of the applied-type measuring instrument can be confirmed.

[0011] According to the insulation resistance monitoring device described in claim 2, the applied type measuring instrument connected to the object to be measured and the grounding part applies a voltage between the object to be measured and the grounding part in a state where the object to be measured is disconnected from the grounding part, excluding the connection between the insulation resistance of the object to be measured and the grounding part through the applied type measuring instrument. Due to the application of this voltage, a current corresponding to the insulation resistance of the object to be measured connected to the applied type measuring instrument is generated, and this current is input into the applied type measuring instrument. By measuring this input current or the voltage obtained by converting this current with the applied type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured. When a positive voltage is applied to the grounding part by the voltage application part of the applied type measuring instrument, the measuring part connected to the object to be measured measures the current or voltage generated on the object to be measured side by the voltage applied by the voltage application part. The connection between this measuring part and the object to be measured is switched by the switching part to the connection between the measuring part via the standard resistance and the grounding part. In the state thus switched, the measuring part measures the current or voltage generated according to the resistance value of the standard resistance instead of the current or voltage generated according to the insulation resistance of the object to be measured based on the voltage applied by the voltage application part. Thereby, for example, the normal operation of the applied 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 resistance.

[0012] Switch The switching unit includes a plurality of switches that individually connect and disconnect between the measurement unit and the object to be measured, and between the measurement unit and the ground through a standard resistor. The applied-type measuring instrument includes a prohibiting means that prohibits the control of closing the switches when the measurement unit measures current or voltage by applying a positive voltage to the ground by the voltage application unit in a state where all of the plurality of switches are controlled to be opened. This can reduce the possibility that the applied-type measuring instrument or the object to be measured fails due to an unintended voltage.

[0013] According to the insulation resistance monitoring device described in claim 3, the applied type measuring instrument connected to the object to be measured and the grounding part applies a voltage between the object to be measured and the grounding part in a state where the object to be measured is disconnected from the grounding part, excluding the connection between the insulation resistance of the object to be measured and the grounding part through the applied type measuring instrument. Due to the application of this voltage, a current corresponding to the insulation resistance of the object to be measured connected to the applied type measuring instrument is generated, and this current is input into the applied type measuring instrument. By measuring this input current or the voltage obtained by converting this current with the applied type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured. When a positive voltage is applied to the ground part by the voltage application part of the Inca type measuring instrument, the measuring part connected to the object to be measured measures the current or voltage generated on the object to be measured side by the voltage applied by the voltage application part. The connection between this measuring part and the object to be measured is switched by the switching part to the connection between the measuring part via the standard resistor and the ground part. In the state switched in this way, the measuring part measures the current or voltage generated according to the resistance value of the standard resistor instead of the current or voltage generated according to the insulation resistance of the object to be measured based on the voltage applied by the voltage application part. Thereby, for example, the normal operation of the applied 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.

[0014] Seal The resistance value of the standard resistor is calculated from the measurement result of the measurement unit in a state where the switching unit switches the connection between the measurement unit and the ground through the standard resistor by the calculation means of the applied-type measuring instrument. In the comparison means of the applied-type measuring instrument, the resistance value calculated by this calculation means is compared with the original resistance value of the standard resistor determined in advance. By this comparison, if the two almost match, it can be determined that the applied-type measuring instrument is operating normally.

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[0020]

[0021]

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[0023]

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0025] Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. First, with reference to FIG. 1, an insulation resistance monitoring device 20 and a measurement object in the first embodiment will be described. FIG. 1 is a circuit diagram schematically showing an insulation resistance monitoring device 20 and an electric circuit of a measurement object. The measurement object includes a set of three AC power lines 11, 12, and 13 constituting a three-phase three-wire AC circuit, and a load device 14 connected to the set of three AC power lines 11 to 13.

[0026] The AC power lines 11 to 13 are power supply lines that supply three-phase power (load power) from an upstream pole-mounted transformer or the like to the downstream load device 14. The three-phase power is three-phase AC power, and the three-phase AC is obtained by shifting the phases of three single-phase ACs of the same voltage flowing through the AC power lines 11 to 13 by 120° each.

[0027] The load device 14 is an electric circuit that operates on three-phase power supplied from a set of AC power lines 11 to 13. Examples of the load device 14 include a three-phase induction motor. The load device 14 is housed in a housing 14a that is grounded (earthed) by type D earthing via a grounding wire 18. The load device 14 is directly connected to the AC power lines 11 to 13 within the housing 14a.

[0028] Note that the grounding wire 18 is a wire connected to a grounding electrode embedded in the ground. The grounding wire 18 connected to the housing 14a, the insulation transformers 21, 22 and the applied type measuring instrument 30 described later may be the same wire, or may be separate wires connected to each other via the ground.

[0029] The insulation resistance monitoring device 20 is for monitoring the insulation resistance between the grounding parts such as the grounding wire 18, the housing 14a, the ground, etc. and the object to be measured. The insulation resistance monitoring device 20 includes insulation transformers 21, 22 arranged in the middle of the AC power lines 11 to 13, synthetic resistance parts 23, 24 connected to the AC power lines 11 to 13, and an applied type measuring instrument 30 connected between the synthetic resistance parts 23, 24 and the grounding wire 18.

[0030] The insulation transformer 22 is arranged on the AC power lines 11 to 13 on the downstream side of the insulation transformer 21. The insulation transformer 21 includes a primary winding 21a connected to the AC power lines 11 to 13 on the upstream side of its arrangement position, a secondary winding 21b connected to the AC power lines 11 to 13 on the downstream side of its arrangement position, a 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 core.

[0031] Similarly, the insulation transformer 22 includes a primary winding 22a, a secondary winding 22b, a core (not shown), and a housing 22c. In order to discharge leakage current and the like generated in the insulation transformers 21, 22 to the ground, the housings 21c, 22c are connected to the grounding wire 18 and grounded.

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

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

[0034] Note that the insulation transformer 21 can transform the voltage on the primary winding 21a side and transmit it to the secondary winding 21b side by making the number of turns of the primary winding 21a different from the number of turns of the secondary winding 21b. However, it is not necessary to perform voltage transformation with the insulation transformer 21 by making the number of turns of the primary winding 21a the same as the number of turns of the secondary winding 21b. Similarly, voltage transformation may or may not be performed with the insulation transformer 22.

[0035] Also, the intermediate wires 11b to 13b and the downstream wires 11c to 13c on the downstream side of the insulation transformers 21 and 22 are all maintained in a state of not being connected to a grounding portion such as the grounding wire 18. That is, the downstream side of the insulation transformers 21 and 22 is not grounded in type B.

[0036] The combined resistance portion 23 includes a resistor 23a having one end connected to the intermediate wire 11b, a resistor 23b having one end connected to the intermediate wire 12b, and a resistor 23c having one end connected to the intermediate wire 13b. The other ends of these three resistors 23a to 23c are combined with each other. The other ends of the combined resistors 23a to 23c and the applied type measuring instrument 30 are connected by a combined wire 23d.

[0037] The three resistors 23a to 23c have the same resistance value. As a result, the graphs of the time variations of the currents generated in the three resistors 23a to 23c respectively by the three-phase power supplied from the intermediate lines 11b to 13b are in a similar relationship with the graphs of the time variations of the voltages of the intermediate lines 11b to 13b (graphs in which the phases of single-phase alternating currents of the same voltage are shifted by 120° each).

[0038] Therefore, at any time, the sum of the currents flowing through the resistors 23a to 23c is approximately 0 A. Thus, the current flowing through the combined wire 23d formed by combining these currents is approximately 0 A, and the voltage combined by the combined wire 23d is also approximately 0 V. Note that the currents and voltages based on the three-phase power are set to approximately 0 because a small amount of current and voltage may be generated in the combined wire 23d when the balance of the voltages between the intermediate lines 11b to 13b is disrupted.

[0039] Also, the "same resistance value" includes cases where the respective resistance values differ within a range of ±5%. Even when the resistance values of the three resistors 23a to 23c are slightly different, a small amount of current and voltage may be generated in the combined wire 23d.

[0040] Similar to the combined resistance section 23, the combined resistance section 24 includes resistors 24a to 24c each having one end connected to the downstream lines 11c to 13c respectively. The other ends of the resistors 24a to 24c combined with each other and the applied type measuring instrument 30 are connected by a combined wire 24d. Since the resistors 24a to 24c have the same resistance value, the current flowing through the combined wire 24d based on the three-phase power is approximately 0 A, and the voltage combined by the combined wire 24d is also approximately 0 V.

[0041] In this way, by connecting the applied type measuring instrument 30 to the AC wires 11 to 13 via the combined resistance sections 23 and 24, it becomes difficult to input the currents and voltages based on the three-phase power to the applied type measuring instrument 30. As a result, operations such as removing the applied type measuring instrument 30 from the AC wires 11 to 13 during the supply of the three-phase power and electromagnetic switches for attaching and detaching it can be made unnecessary.

[0042] Even when the electromagnetic switch is provided, if the electromagnetic switch fails to open due to problems such as welding, the synthetic resistance units 23 and 24 can make it difficult for the current and voltage based on three-phase power to be input to the applied-type measuring instrument 30. Therefore, by using the synthetic resistance units 23 and 24, the applied-type measuring instrument 30 can be kept connected to the AC power lines 11 to 13 even during the supply of three-phase power.

[0043] The applied-type measuring instrument 30 includes a terminal E connected to the ground wire 18, a terminal a connected to the neutral lines 11b to 13b via the synthetic wire 23d and the synthetic resistance unit 23, and a terminal b connected to the downstream lines 11c to 13c via the synthetic wire 24d and the synthetic resistance unit 24.

[0044] The applied-type measuring instrument 30 applies a voltage between the terminal E and the terminal a or the terminal b to generate a current according to the insulation resistance of the measurement object (AC power lines 11 to 13, load device 14) connected to the terminal a or the terminal b. The applied-type measuring instrument 30 measures the voltage obtained by converting this current, calculates the insulation resistance from the voltage, and monitors it.

[0045] Note that the current generated in the AC power lines 11 to 13 by the voltage application of the applied-type measuring instrument 30 does not flow beyond the insulation transformers 21 and 22. Therefore, when the applied-type measuring instrument 30 applies a voltage between the terminal E and the terminal a, it can measure the voltage generated according to the insulation resistance of the measurement object a, which includes the neutral lines 11b to 13b, the secondary winding 21b, and the primary winding 22a connected to the terminal a. Similarly, when the applied-type measuring instrument 30 applies a voltage between the terminal E and the terminal b, it can measure the voltage generated according to the insulation resistance of the measurement object b, which includes the downstream lines 11c to 13c, the secondary winding 22b, and the load device 14 connected to the terminal b.

[0046] In this way, the insulation resistance monitoring device 20 can monitor the insulation resistance of the measurement objects a and b on the downstream side of the insulation transformers 21 and 22 by means of the insulation transformers 21 and 22 located upstream of the connection positions of the terminals a and b. Further, the insulation resistance monitoring device 20 can monitor the insulation resistance of the measurement object a on the upstream side of the insulation transformer 22 by means of the insulation transformer 22 located downstream of the connection position of the terminal a.

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

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

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

[0050] Here, assuming the insulation resistance value of the object to be measured a is R1, the resistance value of the combined resistance section 23 (the value obtained by combining the resistance values of the three resistors 23a, 23b, and 23c) is R2, and the resistance value of the reference resistor 40 is R3, the equation V1 = V0×R1 / (R1 + R2 + R3) holds. Since the voltage V0 and the resistance values R2 and R3 are known in advance, by measuring the voltage V1, the insulation resistance value R1 of the object to be measured a can be calculated.

[0051] Similarly, when measuring the insulation resistance of the object to be measured b (such as the downstream lines 11c to 13c, etc.) connected to the terminal b, the applied type measuring instrument 30 applies a voltage V0 between the terminal E and the terminal b, measures the voltage V1 across the reference resistor 40, and calculates the insulation resistance value R1 of the object to be measured b from the measurement result. In this case, the resistance value of the combined resistance section 24 (the value obtained by combining the resistance values of the three resistors 24a, 24b, and 24c) is taken as R2.

[0052] The applied type measuring instrument 30 is operated by the storage battery 25 instead of the three-phase power supplied from the AC power lines 11 to 13. Furthermore, since the applied type measuring instrument 30 measures the voltage corresponding to the insulation resistance using the voltage (the power of the storage battery 25) it applies itself, the insulation resistances of the objects to be measured a and b can be monitored even when the three-phase power is not supplied.

[0053] Also, to measure the insulation resistances of the objects to be measured a and b with the applied type measuring instrument 30, it is necessary to disconnect the objects to be measured a and b from the grounding part such as the grounding wire 18. However, the objects to be measured a and b including the neutral lines 11b to 13b and the downstream lines 11c to 13c are maintained in a state of being disconnected from the grounding wire 18 due to the absence of type B grounding. Therefore, when measuring with the applied type measuring instrument 30, the operation and process of disconnecting the objects to be measured a and b from the grounding wire 18 can be made unnecessary. Thus, the measurement by the applied type measuring instrument 30 can be simplified.

[0054] In addition, when disconnecting the AC power lines 11 to 13 from the ground line 18 during measurement by the applied-type measuring instrument 30, it is preferable to stop the supply of three-phase power by the AC power lines 11 to 13 and then disconnect them in order to prevent malfunction of the load device 14 or the like. However, due to the unnecessary disconnection, there is no need to stop the supply of three-phase power by the AC power lines 11 to 13 during measurement by the applied-type measuring instrument 30.

[0055] In addition to this, it is difficult for the currents and voltages based on three-phase power to be input into the applied-type measuring instrument 30 by the synthetic resistance units 23 and 24. As a result, even while the load device 14 is operating with three-phase power, the applied-type measuring instrument 30 can measure the voltage corresponding to the insulation resistance of the measurement objects a and b while suppressing the influence on the measurement result by the three-phase power. Therefore, the insulation resistance monitoring device 20 can accurately monitor the insulation resistance of the measurement objects a and b even while the load device 14 is operating.

[0056] Next, with reference to FIGS. 2 to 4, the control of the applied-type measuring instrument 30 will be described in more detail. FIG. 2 is a block diagram showing the electrical configuration of the applied-type measuring instrument 30. The applied-type measuring instrument 30 includes a CPU 31, a flash ROM 32, and a RAM 33 which is a memory for storing various work data, flags, etc. in a rewritable manner during the execution of the program of the CPU 31. These are respectively connected to the input / output port 35 via a bus line 34.

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

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

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

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

[0061] The circuit between the terminal a and the measuring unit 37 is connected so as to be openable and closable by the switch SW1, and the circuit between the terminal b and the measuring unit 37 is connected so as to be openable and closable by the switch SW2. The switches SW1 and SW2 are switches that open and close the electric 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 a wire branched from between the terminal E and the voltage application unit 38, and a switch SW3 that connects the standard resistor 42 and the measuring unit 37 so as to be openable and closable. The standard resistor 42 is a load having a predetermined resistance value. Note that the switch SW3 may be provided between the wire branched from between the terminal E and the voltage application unit 38 and the standard resistor 42.

[0063] Next, referring to FIG. 3, the periodic measurement process executed by the CPU 31 of the applied type measuring instrument 30 will be described. FIG. 3 is a flowchart of the periodic measurement process of the applied type measuring instrument 30. The periodic measurement process of the applied type measuring instrument 30 is executed periodically (for example, every 10 minutes) while the power of the applied type measuring instrument 30 is turned on.

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

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

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

[0067] Next, the measurement result, the measurement object (in the first process after the process of S11, the measurement object a), and the measured date and time are transmitted to the external control device 26 (S18). In the external control device 26, as described later with reference to FIG. 4, this measurement result is accumulated and analyzed.

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

[0069] If the voltage is not detected in the process of S20 (S20: Yes), it can be seen that the switch SW1 instructed to open in the process of S19 has opened without problems. Therefore, the application of the voltage by the voltage application unit 38 is terminated (S21), and n = n + 1 is performed for the next measurement (S22).

[0070] Next, it is confirmed whether n ≥ 4 (S23). If n < 4 (S23: No), since there are still unmeasured ones, the processes below S12 are executed again. Specifically, when 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] Also, when n = 3 in the process of S22, by closing the switch SW3 in the process of S12, the voltage application unit 38, the measurement unit 37, and the reference resistor 40 are connected via the standard resistor 42. Further, since n > 2 in the process of S15 (S15: No), instead of the process of S16, the process of S17 is executed.

[0072] In the process of S17, the voltage across the reference 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 across the reference resistor 40 is V1, and the resistance value of the reference resistor 40 is R3, the equation V1 = V0 × R4 / (R3 + R4) holds. By substituting each value into this equation, the resistance value R4 of the standard resistor 42 is calculated.

[0073] The measurement results calculated in the process of S17 are transmitted to the external control device 26 in the process of S18 with the measurement target being the standard resistor 42. In the external control device 26, the resistance value R4 calculated by the applied type measuring instrument 30 is compared with the original resistance value of the predetermined standard resistor 42. If the two are almost the same, it can be determined that the applied type measuring instrument 30 is operating normally.

[0074] Also, a signal for calibrating the applied type measuring instrument 30 can be sent from the external control device 26 to the applied type measuring instrument 30 so that the resistance value R4 calculated by the applied type measuring instrument 30 approaches the predetermined resistance value of the standard resistor 42. Note that the external control device 26 may not execute the determination of these normal operations and calibration, but the applied type measuring instrument 30 may execute it.

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

[0076] Also, regardless of the value of n, in the process of S20, if a voltage is detected by the measurement unit 37 (S20: No), it can be determined that the switch SWn instructed to be opened in the process of S19 was not actually opened due to welding or the like. In this case, error information indicating that the switch SWn was not opened 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] Here, for example, if the switch SW1 is not opened due to welding and an error occurs, and the periodic measurement process is not terminated but the processes of S12 and below are executed again, and the switch SW2 is closed for measuring the insulation resistance of the measurement object b, the measurement object a and the measurement object b will be connected. If three-phase power is supplied or a voltage is applied by the voltage application unit 38 in this state, each part of the applied type measuring instrument 30 and the measurement objects a and b may malfunction due to an unintended voltage.

[0078] On the other hand, when there is an error in detecting the voltage in the process of S20 (S20: No), by ending the periodic measurement process, it is possible to prevent the plurality of measurement objects a and b from being connected to each other via the switching unit 39. As a result, the possibility that each part of the application type measuring instrument 30 and the measurement objects a and b fails due to an unintended voltage can be reduced.

[0079] Furthermore, until the error is resolved, the control may be such that the periodic measurement process is not executed. Thereby, the possibility that each part of the application type measuring instrument 30 and the measurement objects a and b fails due to an unintended voltage can be further reduced.

[0080] Referring to FIG. 4, among the analyzes executed by the external control device 26, the analysis of the measurement result of the insulation resistance of the measurement object a by the application type measuring instrument 30 will be described. Note that the same analysis is performed on the measurement result of the insulation resistance of the measurement object b.

[0081] In the external control device 26, as shown in FIG. 4, for the measurement object a, a graph is generated and displayed with the past measurement results of the insulation resistance on the vertical axis and the date and time on the horizontal axis. In the graph of FIG. 4, the change over time of the past measurement results (measured values) is shown by a solid line, and the change over time of the future measurement results (predicted values) by the extension of the straight line approximated by the least squares method of the measured values is shown by a two-dot chain line. Further, in the graph of FIG. 4, a threshold value at which deterioration of the insulation resistance is suspected is shown by a broken 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 deterioration of the insulation resistance of the measurement object a is suspected. At this time, it may also be notified to the operator or the operator who operates the load device 14. Note that when measuring the insulation resistance with the application type measuring instrument 30, the temperature and humidity at the time of measurement are also 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, based on the change over time of future measurement results (predicted values) and the threshold value, the date and time when the future measurement results will be equal to or less than the threshold value are predicted, and that date and time are displayed in the graph of FIG. 4. Therefore, the administrator of the external control device 26 can plan the schedule for maintenance of the measurement object a etc. using the date and time when the future measurement results will be equal to or less than the threshold value as a guide, 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 FIGS. 5 to 7. In the first embodiment, the case where the downstream side of the isolation transformer 22 is not grounded in type B was described. In contrast, in the second embodiment, the case where the downstream side of the isolation transformer 22 is grounded in type B will be described. For parts that are the same as those in the first embodiment, the same reference numerals are given and the following description is omitted.

[0085] FIG. 5 is a circuit diagram schematically showing the insulation resistance monitoring device 60 and the electrical circuit of the measurement object in the second embodiment. The measurement object in the second embodiment is obtained by omitting the upstream side of the isolation transformer 22 from the measurement object in the first embodiment.

[0086] The insulation resistance monitoring device 60 includes an isolation transformer 22, a type B grounding wire 66 that grounds the downstream side of the isolation transformer 22 in type B, an electromagnetic switch 67 provided on the type B grounding wire 66, a synthetic resistance section 24, and an applied type measuring instrument 61 connected between the synthetic resistance section 24 and the grounding wire 18.

[0087] The type B grounding wire 66 is a wire branched from the downstream wire 13c in the vicinity of the isolation transformer 22, and is connected to the grounding wire 18 of the housing 22c of the isolation transformer 22. Thereby, the downstream side of the isolation transformer 22 is grounded in type B. Note that the type B grounding wire 66 may be directly connected to the ground to ground the downstream wire 13c.

[0088] The electromagnetic switch 67 is a normally closed switch that opens and closes the type B grounding wire 66. When the electromagnetic switch 67 is de-energized, the type B grounding wire 66 is closed (energized) to ground the downstream wire 13c. When the electromagnetic switch 67 is energized, the type B grounding wire 66 is opened (cut off) to switch the downstream wire 13c to non-grounded.

[0089] As shown in FIG. 6, the applied type measuring instrument 61 is different from the applied type measuring instrument 30 (see FIG. 2) in the first embodiment in that the switching unit 39 and the terminal b are omitted, and the terminal a connected to the combined resistance unit 24 is directly connected to the measuring unit 37 and the reference resistance 40. Further, a different applied voltage monitoring program 62 is provided in the flash ROM 32 of the applied type measuring instrument 61. The configurations of the other parts of the applied type measuring instrument 61 are the same as those of the applied type measuring instrument 30 in the first embodiment.

[0090] The external control device 26 is connected to the applied type measuring instrument 61, the load device 14, and the electromagnetic switch 67, respectively. The external control device 26 transmits the operating state of the load device 14 and the open / closed state of the electromagnetic switch 67 to the applied type measuring instrument 61, and transmits the switching signal from the applied type measuring instrument 61 to the electromagnetic switch 67.

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

[0092] In the periodic measurement process of the applied type measuring instrument 61, first, in order to determine whether the electromagnetic switch 67 can be opened, it is confirmed whether the power of the load device 14 is off (S41). If the power of the load device 14 is on and the electromagnetic switch 67 is opened to make the downstream wire 13c non-grounded, for example, the noise during the operation of the load device 14 cannot escape from the type B grounding wire 66 to the ground, and the load device 14 may malfunction.

[0093] When the power supply of the load device 14 is off (S41: Yes), since the load device 14 will not malfunction even if the electromagnetic switch 67 is opened, 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, in the same manner as in the first embodiment, the processes of S13, S14, S16, S18, and S21 are executed, the insulation resistance of the object to be measured connected to the terminal a is calculated and sent to the external control device 26. Then, so that the load device 14 operates normally when the power supply is turned on, the electromagnetic switch 67 is closed to ground the downstream line 13c again (S43), and the periodic measurement process ends.

[0095] On the other hand, in the process of S41, when the power supply of the load device 14 is on (S41: No), in order to suppress the malfunction of the load device 14 when the electromagnetic switch 67 is opened, the electromagnetic switch 67 is kept closed and the periodic measurement process ends. When a voltage is applied to the ground wire 18 by the voltage application unit 38 with the electromagnetic switch 67 kept closed, a current corresponding to the voltage flows directly from the ground wire 18 and the type B ground wire 66 to the downstream line 13c without passing through the insulation resistance, and the current is input to the measurement unit 37. In this case, there is a possibility that the insulation resistance of the object to be measured cannot be accurately measured from the measurement result of the measurement unit 37.

[0096] In contrast, since the applied type measuring instrument 61 measures the voltage by the measuring unit 37 with the electromagnetic switch 67 opened without supplying three-phase power to the load device 14, the measuring unit 37 can accurately measure the voltage corresponding to the insulation resistance of the object to be measured. As a result, the applied type measuring instrument 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 and 60 for monitoring the insulation resistance of a measurement object including three-phase three-wire AC power lines 11 to 13 were described. In contrast, in the third embodiment, an insulation resistance monitoring device 90 for monitoring 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 denoted by the same reference numerals, and the following description thereof will be omitted.

[0098] FIG. 8 is a circuit diagram schematically showing the insulation resistance monitoring device 90 and the electrical circuit of the measurement object in the third embodiment. The measurement object in the third embodiment includes a battery 81 that outputs DC power (power for load), a positive electrode line 84 connected to the positive electrode of the battery 81, a negative electrode line 85 connected to the negative electrode of the battery 81, and a load device 86 that operates by the DC power supplied from the battery 81 via the positive electrode line 84 and the negative electrode line 85. Examples of this measurement object include automobiles, industrial vehicles, railway vehicles, aircraft, ships, and other electrical devices that use electricity as a driving 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 that the battery 81 can be regarded as a conductor similar to an electric wire with respect to the insulation resistance of the measurement object.

[0100] The positive electrode line 84 and the negative electrode line 85 are a pair of two 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 by the DC power. The load device 86 is housed in a housing 86a that is grounded in type D via a ground line 18. Note that when the measurement object is a vehicle or the like, connecting to a large conductor such as the vehicle frame is referred to as "grounding", and it is not necessary for the large conductor to be connected to the ground.

[0101] The insulation resistance monitoring device 90 includes an applied-type measuring instrument 30 connected between the negative electrode line 85 and the ground line 18. The terminal E of the applied-type measuring instrument 30 is connected to the ground line 18, and the terminal a is connected only to the negative electrode line 85. The applied-type measuring instrument 30 measures a voltage corresponding to the insulation resistance of the measurement object connected to the terminal a by applying a voltage between the terminal E and the 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 applied-type measuring instrument 30 can measure a voltage corresponding to the insulation resistance of not only the negative electrode line 85, the battery 81, and the load device 86 but also the positive electrode line 84 among the measurement objects, even if the terminal a is not directly connected to the positive electrode line 84. Therefore, the insulation resistance monitoring device 90 can monitor the insulation resistance of the positive electrode line 84, the negative electrode line 85, the battery 81, and the load device 86 based on the measurement result of the applied-type measuring instrument 30.

[0103] Also, the potential of the negative electrode line 85 with respect to the ground line 18 approaches 0V regardless of the presence or absence of their connection. Therefore, even while DC power is being supplied from the battery 81 to the load device 86, it is possible to make it difficult for current or voltage based on the DC power to be input from the negative electrode line 85 to the applied-type measuring instrument 30. As a result, operations such as disconnecting the applied-type measuring instrument 30 from the negative electrode line 85 when DC power is supplied from the battery 81, and electromagnetic switches for attaching and detaching it can be made unnecessary. Therefore, the applied-type measuring instrument 30 can be kept connected to the negative electrode line 85 even when DC power is being supplied.

[0104] For noise countermeasures of the load device 86 and the like, the negative electrode line 85 may be connected to a ground portion such as the ground line 18 or the vehicle frame to be grounded. However, in this embodiment, the negative electrode line 85 is maintained in a state of being disconnected from the ground line 18. Thereby, operations and processes (for example, opening and closing of the electromagnetic switch 67 as in the second embodiment) for disconnecting the negative electrode line 85 from the ground line 18 during measurement by the applied-type measuring instrument 30 can be made unnecessary. Therefore, the measurement by the applied-type measuring instrument 30 can be simplified.

[0105] Furthermore, when measuring with the applied type measuring instrument 30, there is no need to disconnect the negative electrode wire 85 from the ground wire 18, so there is also no need to stop the supply of DC power by the negative electrode wire 85 and the positive electrode wire 84. In addition, since it is difficult for a current or voltage based on DC power to be input to the applied type measuring instrument 30 connected to the negative electrode wire 85, even while the load device 86 is operating with DC power, the applied type measuring instrument 30 can measure the voltage corresponding to the insulation resistance of the object to be measured while suppressing the influence on the measurement result by the DC power. Therefore, the insulation resistance monitoring device 90 can accurately monitor the insulation resistance of the object to be measured even while the load device 86 is operating.

[0106] As described above, the present invention has been described based on the embodiments. However, it can be easily inferred that the present invention is not limited to the above-described embodiments at all, and various improvements and modifications can be made without departing from the spirit 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 executed, the number of load devices 14, 86, etc. may be appropriately changed. Also, the external control device 26 may be omitted, and the control executed by the external control device 26, etc. may be executed by the applied type measuring instruments 30, 61.

[0107] In the applied type measuring instruments 30, 61 in the above embodiment, the case where a voltage is applied by the voltage application unit 38 to generate a current according to the insulation resistance of the object to be measured and the voltage obtained by converting the current is measured by the measurement unit 37 has been described. On the other hand, the reference resistance 40 may be omitted, and by using the measurement unit 37 as an ammeter, the measurement unit 37 may measure the current generated according to the insulation resistance of the object to be measured when the voltage is applied by the voltage application unit 38.

[0108] Also, it is not limited to the case where a positive voltage is applied from the voltage application unit 38 to the ground wire 18 via the terminal E. For example, a positive voltage may be applied from the voltage application unit 38 to the terminal a or b, and the current or voltage generated according to the insulation resistance due to the application of the voltage may be input from the terminal E to the applied type measuring instruments 30, 61. In this case, the measurement unit 37 connected to the terminal E measures the current or voltage generated according to the insulation resistance.

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

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

[0111] In the above embodiment, the case where the insulation transformers 21 and 22 are arranged in the middle of the AC power lines 11 to 13 has been described, but these insulation transformers 21 and 22 may be omitted. At this time, when monitoring a part of the insulation resistance of the AC power lines 11 to 13 with the application type measuring instruments 30 and 61, a part of the AC power lines 11 to 13 may be separated from the other part and also separated from the grounding part such as the ground wire 18.

[0112] Also, the synthetic resistance parts 23 and 24 in the above embodiment may be omitted, and one of the AC power lines 11 to 13 may be directly connected to the terminals a and b. However, in this case, in order to disconnect the AC power lines 11 to 13 from the measurement unit 37 during the supply of three-phase power, it is preferable to provide switches SW1 and SW2 or electromagnetic switches between them.

[0113] In the second embodiment described above, the case where the type-B ground wire 66 branches off from the downstream wire 13c has been explained. However, the type-B ground wire 66 may also branch off from the downstream wire 11c or the downstream wire 12c. Further, 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 type-B ground wire 66 in the second embodiment. In this case, measurement is performed by the applied-type measuring instrument 30 with the electromagnetic switch 67 provided in the type-B ground wire 66 open. Conversely, in the second embodiment, the type-B ground wire 66 may be omitted.

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

[0115] In the above embodiment, the case where the electromagnetic switch 67 is a normally closed switch has been explained. However, a normally open switch that opens when not energized and closes when energized may be used as the electromagnetic switch 67. Further, a latch-type switch that maintains the open / closed state when not energized and opens / closes in response to an electrical signal may be used as the electromagnetic switch 67. <Others> Japanese Patent Application Laid-Open No. 2017-173176 describes an applied-type measuring instrument for monitoring the insulation resistance of a measurement object including a set of a plurality of power supply lines for supplying power from upstream to downstream and a load device operated by the power supplied from the power supply lines. This applied-type measuring instrument is connected to a grounded ground portion and the measurement object, and applies a voltage between the ground portion and the measurement object. This voltage is divided by the insulation resistance of the measurement object and a reference resistor inside the applied-type measuring instrument, and the applied-type measuring instrument calculates the insulation resistance of the measurement object with respect to the ground portion by measuring the voltage applied to the reference resistor. However, in the prior art, there was a risk that power for operating the load device of the object to be measured would be input to the applied-type measuring instrument connected to the object to be measured in order to monitor the insulation resistance of the object to be measured. This technical idea was made to solve the above-described problems, and an object thereof is to provide an insulation resistance monitoring device that can make it difficult for power for operating a load device to be input to an applied-type measuring instrument. <Means> The insulation resistance monitoring device of Technical Idea 1 monitors the insulation resistance between a grounded grounding part and the object to be measured for an object to be measured including a set of three AC power lines that form a three-phase three-wire circuit and supply three-phase power from upstream to downstream, and a load device that operates by the three-phase power supplied from the set of three AC power lines. The device includes three resistors having one end individually connected to the three AC power lines and the other ends combined with each other to have the same resistance value, and is connected to the combined other ends of the three resistors and the grounding part, respectively. An applied-type measuring instrument that measures a current generated according to the insulation resistance of the object to be measured or a voltage obtained by converting the current by applying a voltage between the other end and the grounding part in a state where the object to be measured to which the resistor is connected is disconnected from the grounding part. The insulation resistance monitoring device of Technical Idea 2 is the insulation resistance monitoring device of Technical Idea 1, wherein the three AC power lines to which the resistors are connected are all maintained in a state of being disconnected from the grounding part. The insulation resistance monitoring device of Technical Idea 3 is the insulation resistance monitoring device of Technical Idea 1 or 2, and includes an upstream transformer that is arranged on the three AC power lines upstream of the positions where one ends of the three resistors are respectively connected, and transmits the three-phase power by electromagnetic induction from the upstream side to the downstream side while insulating the AC power lines on the upstream side and the downstream side of the arrangement position. The insulation resistance monitoring device of Technical Idea 4 is the insulation resistance monitoring device according to any one of Technical Ideas 1 to 3, and includes a downstream transformer that is arranged on the three AC power lines downstream of the positions where one ends of the three resistors are respectively connected, and transmits the three-phase power by electromagnetic induction from the upstream side to the downstream side while insulating the AC power lines on the upstream side and the downstream side of the arrangement position. The insulation resistance monitoring device of Technical Idea 5 is an insulation resistance monitoring device of any one of Technical Ideas 1 to 4. In the applied type measuring instrument, a voltage application unit that applies a positive voltage to the grounding part, a measuring unit that is connected to the other end and measures the current or voltage generated on the other end side by the voltage applied by the voltage application unit, a standard resistor having a predetermined resistance value disposed between the measuring unit and the grounding part, and a switching unit that switches the connection between the measuring unit and the other end to the connection between the measuring unit and the grounding part via the standard resistor. The measuring unit measures the current or voltage generated according to the resistance value of the standard resistor instead of the current or voltage generated according to the insulation resistance of the object to be measured based on the voltage applied by the voltage application unit in a state where the switching unit switches the connection between the measuring unit and the grounding part via the standard resistor. The insulation resistance monitoring device of Technical Idea 6 monitors the insulation resistance between a grounded grounding part and a measurement object including a battery that outputs DC power, a positive electrode wire connected to the positive electrode of the battery, a negative electrode wire connected to the negative electrode of the battery, and a load device that operates by the DC power supplied from the battery via the positive electrode wire and the negative electrode wire. An applied type measuring instrument that measures the current generated according to the insulation resistance of the measurement object or the voltage obtained by converting the current by applying a voltage between the negative electrode wire and the grounding part while being disconnected from the positive electrode wire and connected to the negative electrode wire and the grounding part respectively and then disconnecting the negative electrode wire from the grounding part is provided. The insulation resistance monitoring device of Technical Idea 7 is the insulation resistance monitoring device of Technical Idea 6, in which the negative electrode wire is maintained in a state of being disconnected from the grounding part. <Effect> According to the insulation resistance monitoring device of Technical Idea 1, one end of three resistors is individually connected to three AC power lines, and the other ends of these three resistors are combined with each other. An applied type measuring instrument connected to the combined other end and the grounding part applies a voltage between the combined other end and the grounding part in a state where the measurement object (load device, AC power line) to which the resistor is connected is disconnected from the grounding part. Due to the application of this voltage, a current corresponding to the insulation resistance of the measurement object connected to the applied type measuring instrument via the resistor is generated, and this current is input into the applied type measuring instrument. By measuring this input current or the voltage obtained by converting this current with the applied type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the measurement object. Since the three resistors provided between the three AC power lines and the applied type measuring instrument have the same resistance value, the sum of the currents generated in the three resistors respectively by the three-phase power supplied from the three-phase three-wire AC power line becomes approximately 0 A, and the voltage combined on the other end side of the resistors also becomes approximately 0 V. Therefore, it is possible to make it difficult for the current and voltage based on the three-phase power for operating the load device to be input into the applied type measuring instrument. Note that the "same resistance value" includes cases where the respective resistance values differ within the range of ±5%. According to the insulation resistance monitoring device of Technical Idea 2, in addition to the effects achieved by the insulation resistance monitoring device of Technical Idea 1, the following effects are achieved. Since the three AC power lines to which the resistors are connected are all maintained in a state of being disconnected from the grounding part, the operation and process of disconnecting these AC power lines from the grounding part during measurement by the applied type measuring instrument can be made unnecessary. Therefore, the measurement by the applied type measuring instrument can be simplified. Note that when disconnecting the AC power line from the grounding part during measurement by the applied type measuring instrument, in order to prevent malfunction of the load device or the like, it is preferable to stop the supply of the three-phase power for operating the load device and then disconnect. However, due to the unnecessity of this disconnection, there is no need to stop the supply of the three-phase power during measurement by the applied type measuring instrument. In addition to this, since it is difficult for the current and voltage based on the three-phase power to be input into the applied type measuring instrument by the three resistors, even during the operation of the load device by the three-phase power, the applied type measuring instrument can measure the current or voltage corresponding to the insulation resistance of the measurement object. Therefore, the insulation resistance monitoring device can monitor the insulation resistance of the measurement object even during the operation of the load device. According to the insulation resistance monitoring device of Technical Idea 3, in addition to the effects achieved by the insulation resistance monitoring devices of Technical Ideas 1 or 2, the following effects are achieved. An upstream transformer is arranged on three AC power lines upstream of the positions where one ends of three resistors are respectively connected. This upstream transformer insulates the AC power lines on the upstream side and the downstream side from its arranged position, and transmits three-phase power from the upstream side to the downstream side by electromagnetic induction. Therefore, the applied-type measuring instrument can measure the current or voltage generated according to the insulation resistance of the object to be measured on the downstream side of the upstream transformer due to the application of voltage. As a result, the insulation resistance monitoring device can monitor the insulation resistance on the downstream side by providing an upstream transformer without disconnecting the AC power line in the middle and stopping the supply of three-phase power in order to monitor the insulation resistance of a part of the AC power line. According to the insulation resistance monitoring device of Technical Idea 4, in addition to the effects achieved by any of the insulation resistance monitoring devices of Technical Ideas 1 to 3, the following effects are achieved. A downstream transformer is arranged on three AC power lines downstream of the positions where one ends of three resistors are respectively connected. This downstream transformer insulates the AC power lines on the upstream side and the downstream side from its arranged position, and transmits three-phase power from the upstream side to the downstream side by electromagnetic induction. Therefore, the applied-type measuring instrument can measure the current or voltage generated according to the insulation resistance of the object to be measured on the upstream side of the downstream transformer due to the application of voltage. As a result, the insulation resistance monitoring device can monitor the insulation resistance on the upstream side by providing a downstream transformer without disconnecting the AC power line in the middle and stopping the supply of three-phase power in order to monitor the insulation resistance of a part of the AC power line. According to the insulation resistance monitoring device of Technical Idea 5, in addition to the effects achieved by the insulation resistance monitoring devices of any of Technical Ideas 1 to 4, the following effects are achieved. When a positive voltage is applied to the grounding part by the voltage application part of the applied type measuring instrument, the measuring part connected to the other end of the combined three resistors measures the current or voltage generated on the other end side of the resistor due to the voltage applied by the voltage application part. The connection between this measuring part and the other end of the resistor is switched by the switching part to the connection between the measuring part via the standard resistor and the grounding part. In the state switched in this way, the measuring part measures the current or voltage generated according to the resistance value of the standard resistor instead of the current or voltage generated according to the insulation resistance of the object to be measured based on the voltage applied by the voltage application part. Thereby, for example, by comparing the resistance value calculated from the measured current or voltage with the resistance value of the predetermined standard resistor, the normal operation of the applied type measuring instrument can be confirmed. According to the insulation resistance monitoring device of Technical Idea 6, the applied type measuring instrument connected to the negative electrode line and the grounding part while being disconnected from the positive electrode line applies a voltage between the negative electrode line and the grounding part with the negative electrode line disconnected from the grounding part. Due to the application of this voltage, a current corresponding to the insulation resistance of the object to be measured connected to the applied type measuring instrument is generated, and this current is input into the applied type measuring instrument. By measuring this input current or the voltage obtained by converting this current with the applied type measuring instrument, the insulation resistance monitoring device can monitor the insulation resistance of the object to be measured. Since the battery is regarded as a low-resistance conductor, the positive electrode line and the negative electrode line connected via the battery are regarded as a single electric wire. Thereby, the insulation resistance monitoring device can measure, with the applied type measuring instrument, the current or voltage corresponding to the insulation resistance not only of the negative electrode line but also of the positive electrode line, and can monitor the insulation resistances of the positive electrode line and the negative electrode line. Also, since the potential of the negative electrode line with respect to the grounding part approaches 0V, it is possible to make it difficult for the current or voltage based on the DC power to be input from the negative electrode line to the applied type measuring instrument even while DC power is being supplied to the load device. According to the insulation resistance monitoring device of Technical Idea 7, in addition to the effects achieved by the insulation resistance monitoring device of Technical Idea 6, the following effects can be achieved. Since the negative electrode wire is maintained in a state of non-connection with the grounding part, the operation and process of disconnecting the negative electrode wire from the grounding part during measurement by the applied type measuring instrument can be made unnecessary. Therefore, the measurement by the applied type measuring instrument can be simplified. In addition, when disconnecting the negative electrode wire from the grounding part during measurement by the applied type measuring instrument, in order to prevent malfunction of load equipment etc., it is preferable to disconnect after stopping the supply of DC power for operating the load equipment. However, due to the unnecessity of such disconnection, there is no need to stop the supply of DC power during measurement by the applied type measuring instrument. In addition to this, since it is difficult for current or voltage based on DC power to be input to the applied type measuring instrument connected to the negative electrode wire, even while the load equipment is operating with DC power, the applied type measuring instrument can measure the current or voltage corresponding to the insulation resistance of the object to be measured. 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 Reference Signs

[0116] 11, 12, 13 AC power line (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 Grounding wire (grounding part) 20, 60, 90 Insulation resistance monitoring device 30, 61 Applied type measuring instrument 37 Measuring section 38 Voltage application section 39 Switching section 42 Standard resistance 81 Battery (part of the object to be measured) 84 Positive electrode wire (part of the object to be measured) 85 Negative electrode wire (part of the object to be measured) SW1, SW2, SW3 Switch

Claims

1. An insulation resistance monitoring device for monitoring insulation resistance between a measurement object and a grounded part, 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 measures a current or a voltage; 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 between a first state in which the measurement object is connected to the measurement unit without connecting the ground unit to the measurement unit via the standard resistor, and a second state in which the ground unit is connected to the measurement unit via the standard resistor, The measurement unit is measuring a current or a voltage generated in response to an insulation resistance of the measurement object by a voltage applied by the voltage application unit in the first state; an insulation resistance monitoring device for measuring a current or voltage generated in response to a 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, in the second state switched from the first state by the switching unit.

2. An insulation resistance monitoring device for monitoring the 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 measurement object 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 a resistance value of the standard resistor, instead of a current or voltage generated in response to an insulation resistance of the measurement object, based on a voltage applied by the voltage application unit, in a state in which the measurement unit is switched to a connection between the measurement unit and the ground unit via the standard resistor by the switching unit; the switching unit includes a plurality of switches for individually opening and closing a connection 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 is characterized in that the application-type measuring instrument is equipped with a prohibition means for prohibiting control to close the switch when the measuring unit measures a current or voltage by applying a positive voltage to the ground unit by the voltage application unit while controlling all of the multiple switches to be open.

3. An insulation resistance monitoring device for monitoring the 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 measurement object 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 a resistance value of the standard resistor, instead of a current or voltage generated in response to an insulation resistance of the measurement object, based on a voltage applied by the voltage application unit, in a state in which the measurement unit is switched to a connection between the measurement unit and the ground unit via the standard resistor by the switching unit; The voltage application type measuring instrument includes: 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; 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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