Electric leakage monitoring device and leakage current detection method

Abstract

To provide an electric leakage monitoring device and a leakage current detection method capable of widening an object capable of monitoring a leakage current.SOLUTION: A pair of two individual current transformers 21, 22 (an individual measuring instrument) of an electric leakage measuring instrument 20 (an electric leakage monitoring device) individually measure a current flowing through a pair of positive electrode wire 12 and a negative electrode wire 13. A total of the measured current indicates a value of a leakage current generated on a downstream side of the individual current transformers 21, 22. In particular, according to the individual current transformers 21, 22, even when the positive electrode line 12 and the negative electrode line 13 are separated from each other, a total of the current flowing through the positive electrode line 12 and the negative electrode line 13 can be calculated, and the leakage current can be monitored. As a result, the range of targets that can be monitored for the leakage current by the electric leakage measuring instrument 20 can be widened.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a leakage current monitoring device and leakage current detection method for monitoring leakage current in an electric circuit, and more particularly to a leakage current monitoring device and leakage current detection method capable of monitoring a wide range of objects for leakage current. [Background technology]

[0002] An electric circuit supplies DC or AC power from an upstream power source to downstream load equipment via a set of multiple power lines, and the load equipment is operated by the supplied power. A leakage current monitor is known that measures this electric circuit as a measurement object and monitors leakage current from the measurement object to the ground, etc.

[0003] In the leakage current monitoring device disclosed in Patent Document 1, a set of three power lines are passed through a current transformer, and the current transformer measures the total current flowing through those power lines. If there is no leakage current downstream of the current transformer, basically, all of the current passing through the current transformer toward the load device passes through the current transformer again and returns from the load device to the upstream side. Therefore, in this case, the measurement result by the current transformer (the total current flowing through one set of power lines) is basically about 0 A. In contrast, if a leakage current occurs downstream so as to bypass the current transformer, the current transformer measures a current of the same magnitude but in the opposite direction to the leakage current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4159590 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional leakage current monitoring device, for example, if the positions of a pair of power lines are far apart, it may be impossible to pass the pair of power lines through one current transformer together. In this case, the leakage current of the measurement object cannot be measured by the leakage current monitoring device using the current transformer. In other words, the conventional leakage current monitoring device has a problem that the objects that can be monitored for leakage current are limited.

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a leakage current monitoring device and leakage current detection method that can monitor a wide range of objects for leakage current. [Means for solving the problem]

[0007] To achieve this objective, the leakage current monitoring device of the present invention monitors the leakage current of a measurement object comprising a set of multiple power lines that supply load power from upstream to downstream, and a load device that operates using the load power supplied from the set of power lines, and has one or more measuring units capable of monitoring the leakage current generated within a specified range of the measurement object, one of which is formed by a set of multiple individual measuring instruments that individually measure the current flowing through each of the set of multiple power lines.

[0008] The "load power" may be DC power or AC power, and the AC power may be single-phase or three-phase. Furthermore, "monitoring leakage current" does not only mean calculating the leakage current generated in the measurement object by the leakage current monitoring device, but also means transmitting the measurement results required for calculating the leakage current from the leakage current monitoring device to an external control device, etc., so that the leakage current can be calculated on the external control device.

[0009] As another means for achieving the above-mentioned object, the leakage current monitoring device of the present invention monitors the leakage current of a measurement object having a set of multiple power lines that supply load power from upstream to downstream, and a load device that operates with the load power supplied from the set of power lines, and is equipped with an upstream measuring instrument that measures the current flowing through one of the power lines, and a downstream measuring instrument that measures the current flowing through the power line downstream of the measurement position of the upstream measuring instrument on the power line whose current is measured by the upstream measuring instrument.

[0010] The leakage current detection method of the present invention is a method for detecting leakage current in a measurement object having a set of multiple power lines that supply load power from upstream to downstream and a load device that operates with the load power supplied from the set of power lines, and includes an individual measurement step of individually measuring the current flowing through each of the set of multiple power lines using a measuring instrument, a summation step of summing the multiple currents individually measured in the individual measurement step, and a detection step of detecting the leakage current of the measurement object based on the current summed in the summation step.

[0011] Another leakage current detection method of the present invention is a leakage current detection method for detecting a leakage current of a measurement object having a set of multiple power lines supplying load power from upstream to downstream and a load device operated by the load power supplied from the set of power lines, and includes a measurement step of measuring individually the current flowing at two different points on the power line using a measuring instrument, a difference step of calculating the difference between the currents measured at the two points in the measurement step, and a detection step of detecting the leakage current of the measurement object based on the current difference calculated in the difference step. Effect of the Invention

[0012] The leakage current monitoring device described in claim 1 monitors leakage current occurring within a predetermined range of a measurement object that operates a load device by load power supplied from a set of multiple power lines using one or more measurement units. One of the measurement units is formed by a set of multiple individual measuring instruments. The set of individual measuring instruments individually measures the current flowing through each of the set of multiple power lines of the measurement object.

[0013] For example, if there is no leakage current in the object being measured, basically all of the current that passes through one part of a pair of power lines toward the load equipment returns upstream from the load equipment through another part of the pair of power lines, so the total current measured by one pair of individual measuring instruments (total current flowing through one pair of power lines) is approximately 0 A. Note that the "total current measured by one pair of individual measuring instruments" is the sum of the current flowing upstream as a positive value and the current flowing downstream as a negative value.

[0014] On the other hand, similar to the conventional technology, when leakage current occurs downstream of the measurement position of an individual meter (the position where the current is measured by the individual meter), the sum of the currents measured by a set of individual meter indicates the value of that leakage current. In this way, the leakage current monitoring device can monitor leakage current occurring downstream of the measurement position of the individual meter using a set of individual meter (measurement unit).

[0015] In particular, in the leakage current monitoring device of the present invention, the current flowing through each of a pair of power lines is measured individually by an individual measuring device, so that even if the power lines are separated from each other, the total current flowing through the pair of power lines can be calculated and the leakage current can be monitored. As a result, the leakage current monitoring device can monitor a wide range of objects.

[0016] The leakage current monitoring device according to claim 2 has the following effect in addition to the effect of the leakage current monitoring device according to claim 1. When the sum of the currents measured by a set of individual measuring instruments is calculated as the leakage current, the sum is affected by the voltage occurring between the set of power lines at the measurement positions of the individual measuring instruments. Therefore, this voltage is measured by a reference detection unit. Furthermore, this measured voltage is related to the current measured by the individual measuring instruments at the time of measurement by a reference relating means. This makes it possible to calculate the value of the leakage current by correcting the sum of the currents measured by the set of individual measuring instruments based on the voltage, thereby widening the range in which the detection accuracy of the leakage current can be ensured.

[0017] Note that associating "A" (e.g., the total current measured by a set of individual measuring devices) with "B" (e.g., the voltage measured by a reference detection unit) may mean, for example, storing "A" and "B" in a mutually associated state in the same memory, or storing "A" and "B" in separate memories and associating the two based on the measurement dates and times of "A" and "B." Furthermore, calculating a specific value using "A" and "B" may also be referred to as associating "B" with "A." Furthermore, it is not necessary to associate "B" with "A" itself, but "B" may also be associated with a value calculated using "A."

[0018] The leakage current monitoring device according to claim 3 achieves the following effects in addition to those achieved by the leakage current monitoring device according to claim 1. The operating state of the load equipment (the control state of the load equipment, the time, the outside temperature, the humidity, etc.) is acquired by an acquisition means. Furthermore, this acquired operating state is associated by a state association means with the current measured by the individual measuring instruments at the time of acquisition. As a result, for example, if the value of the leakage current calculated from the sum of the currents measured by a set of individual measuring instruments becomes large only in a specific operating state, it can be presumed that a leakage current is occurring in a part through which current flows in that specific operating state. This makes it easier to analyze the cause of the leakage current.

[0019] The earth leakage monitoring device according to claim 4 achieves the following effects in addition to those achieved by the earth leakage monitoring device according to claim 1. The sum calculation means calculates the sum of the currents measured by a set of individual measuring devices. The memory determination means determines whether to store data relating to the sum in the memory unit based on the sum calculated by the sum calculation means. When the memory determination means determines to store the data, the memory execution means stores the data relating to the sum in the memory unit. This makes it possible, for example, to select data effective for analyzing leakage current from the data relating to the sum and store it in the memory unit, thereby reducing the amount of data stored in the memory unit per given time, and making it easier to miniaturize and reduce costs of the earth leakage monitoring device.

[0020] Note that data relating to "X" (e.g., the total current measured by a set of individual measuring devices) may be data for "X" itself, data for calculating "X" (e.g., the current from each individual measuring device), or data for a value calculated using "X" (e.g., the average value obtained by averaging multiple totals).

[0021] According to the leakage current monitoring device of claim 5, in addition to the effects of the leakage current monitoring device of claim 1, the following effects are achieved. Two or more measuring units are provided separately on the upstream and downstream sides of a pair of power lines, and monitor the leakage current generated in the measurement object downstream of the position where each measuring unit is disposed. This makes it possible to measure the leakage current generated between the upstream measuring unit and the downstream measuring unit, for example, from the difference between the measurement results of the upstream measuring unit and the downstream measuring unit. This makes it easier to analyze the cause of the leakage current.

[0022] The leakage current monitoring device according to claim 6 has the following effect in addition to the effect of the leakage current monitoring device according to claim 5. One of the measuring units is formed by a zero-phase measuring instrument that collectively measures the magnetic field generated in each of a set of power lines by the passage of current and measures the total current flowing through those power lines based on the magnetic field. This makes it possible to measure the total current at a position where, for example, each of a set of power lines is bundled together and it is difficult to measure the current with an individual measuring instrument, using the zero-phase measuring instrument. As a result, the degree of freedom in arranging the measuring unit can be improved, making it easier to analyze the cause of leakage current.

[0023] According to the leakage current monitoring device of claim 7, in addition to the effects of the leakage current monitoring device of claim 5 or 6, the following effects are achieved. The set of power lines includes a set of main electric wires on the upstream side and a plurality of sets of branch electric wires each branching off from the set of main electric wires. A plurality of load devices are connected to each set of branch electric wires. A measuring unit arranged on the set of main electric wires upstream of the plurality of sets of branch electric wires can easily monitor (measure or calculate) the total of the leakage currents of the load devices connected to the plurality of sets of branch electric wires. In addition, since another measuring unit is arranged on the set of branch electric wires, the leakage current of the load devices connected to the set of branch electric wires can be monitored without being affected by the leakage currents of the load devices connected to the other branch electric wires. Furthermore, by comparing the measurement results of the measuring unit on the main electric wire side and the measuring unit on the branch electric wire side, the cause of the leakage current can be easily analyzed.

[0024] According to the leakage current monitoring device of claim 8, in addition to the effects of the leakage current monitoring device of claim 1, the following effects are achieved. The measurement object comprises a housing in which a load device is housed, and a ground wire that grounds the housing. One of the two or more measurement units is formed by a ground side measuring instrument that measures the current flowing through the ground wire. This ground side measuring instrument can measure the leakage current occurring between the load device and the housing. By comparing this measurement result with the measurement result by a set of individual measuring instruments (leakage current occurring downstream of the measurement position of the individual measuring instruments), it is possible to easily analyze the cause of the leakage current.

[0025] The leakage current monitoring device described in claim 9 monitors the leakage current of a measurement object that operates a load device by load power supplied from a set of multiple power lines. An upstream measuring instrument measures the current flowing through one of the set of multiple power lines. Furthermore, a downstream measuring instrument measures the current flowing through the one power line whose current is measured by the upstream measuring instrument downstream of the measurement position of the upstream measuring instrument. In this way, if there is a difference between the measurement results of the upstream measuring instrument and the downstream measuring instrument, it can be determined that a leakage current has occurred between them. In this way, the leakage current monitoring device can monitor the leakage current without measuring the current of each of the set of multiple power lines, so that the objects that can be monitored for leakage current can be expanded.

[0026] According to the leakage current detection method of claim 10, similar to the effect achieved by the leakage current monitoring device of claim 1, by individually measuring the current flowing through a set of multiple power lines, the leakage current of the measurement object can be detected based on the sum of the currents, thereby expanding the range of objects for which leakage current can be monitored.

[0027] According to the leakage current detection method recited in claim 11, similar to the effect achieved by the leakage current monitoring device recited in claim 9, it is possible to detect the leakage current of the object to be measured without measuring the current of each of a set of multiple power lines, thereby expanding the range of objects for which leakage current can be monitored. [Brief description of the drawings]

[0028] [Figure 1] 1 is a circuit diagram showing a schematic diagram of an electric circuit of a leakage current monitoring device (leakage current measuring instrument) and an object to be measured in a first embodiment. [Diagram 2] Graph (a) is a graph showing the change over time in the current measured in an individual current transformer and a zero-phase current transformer, and graph (b) is a graph showing the change over time in the leakage current. [Diagram 3] FIG. 2 is a block diagram showing the electrical configuration of the earth leakage measuring device. [Figure 4] 4 is a flowchart of a main process executed by a CPU of the earth leakage measuring device. [Diagram 5]13 is a flowchart of a peak detection process. [Figure 6] 13 is a flowchart of an average detection process. [Figure 7] 13 is a flowchart of a cycle collection process. [Figure 8] 11 is a circuit diagram showing a schematic diagram of an electric circuit of a leakage current monitor and an object to be measured in a second embodiment. FIG. [Figure 9] 1 is a graph showing changes in leakage current over time. [Figure 10] FIG. 2 is a block diagram showing the electrical configuration of a vehicle that is an object to be measured. [Figure 11] 4 is a flowchart of main processing executed by a CPU of the vehicle control device. [Figure 12] 13 is a circuit diagram showing a schematic diagram of an electric circuit of a leakage current monitor and an object to be measured in a third embodiment. FIG. [Figure 13] FIG. 13 is a circuit diagram showing a schematic diagram of an electric circuit of a leakage current monitor and an object to be measured in a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. First, a leakage current measuring device 20 and a measurement object 10 as a leakage current monitoring device in a first embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram showing a schematic diagram of an electric circuit of the leakage current measuring device 20 and the measurement object 10.

[0030] The measurement object 10 includes a battery 11 that outputs DC power (load power), a positive line 12 connected to the positive electrode of the battery 11, a negative line 13 connected to the negative electrode of the battery 11, and a load device 14 that operates with the DC power supplied from the battery 11 via the positive line 12 and the negative line 13. Examples of the measurement object 10 include automobiles, industrial vehicles, railroad cars, aircraft, and ships that are driven by electricity. Other examples of the measurement object 10 include indoor and outdoor wiring or electrical equipment, electrical appliances, etc. in homes, facilities, factories, etc.

[0031] Battery 11 is a DC power supply that outputs DC power of a predetermined voltage (for example, about 800 V). Positive line 12 and negative line 13 are a pair of power lines for supplying DC power from upstream battery 11 to downstream load device 14, and are each connected to load device 14. Current flows from positive line 12 to load device 14, and current flows from load device 14 to negative line 13. Note that in this specification, rather than the direction of current, the power supply side of battery 11, etc. is referred to as "upstream" and the power consumption side of load device 14, etc. is referred to as "downstream."

[0032] The load device 14 is an electric circuit that operates by DC power. Examples of the load device 14 include a DC motor and an inverter. The load device 14 is housed in a housing 14a that is grounded (earthed) via a ground wire 18.

[0033] The ground wire 18 is an electric wire connected to a ground electrode embedded in the ground. However, when the measurement target 10 is a vehicle or the like, the term "ground" 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 ground.

[0034] In this embodiment, not only the housing 14a but also the negative electrode line 13 is grounded via a ground wire 18. The ground wire 18 connected to the housing 14a and the negative electrode line 13 may be the same electric wire, or may be separate electric wires connected to each other via the earth.

[0035] In such a measurement object 10, leakage current may occur due to deterioration of insulation resistance of each part. Regardless of the occurrence of leakage current, an electric circuit is formed so that the current flowing out of the positive electrode side of the battery 11 is basically the same as the current flowing in from the negative electrode side. Therefore, for example, if leakage current occurs from the load device 14 to the housing 14a, the leakage current returns to the battery 11 from the negative electrode line 13 via the ground wire 18.

[0036] A leakage current measuring instrument 20 for monitoring such leakage current is provided in the measurement object 10. The leakage current measuring instrument 20 includes an individual current transformer 21 through which the positive electrode line 12 passes, an individual current transformer 22 through which the negative electrode line 13 passes, a zero-phase current transformer 23 through which the positive electrode line 12 and the negative electrode line 13 pass together, and a reference detection unit 24 that measures the voltage (potential difference) between the positive electrode line 12 and the negative electrode line 13.

[0037] The individual current transformers (individual measuring instruments) 21, 22 and the zero-phase current transformer (zero-phase measuring instrument) 23 are each a measuring instrument composed of a ring-shaped current transformer through which the electric wire to be measured passes, and measure the value of the current flowing through the pass-through portion. More specifically, a current transformer measures a magnetic field generated at the pass-through portion of the electric wire by current flow, and measures (calculates) the value of the current based on the magnetic field. The individual current transformers 21, 22 and the zero-phase current transformer 23 in this embodiment are configured to be able to measure a DC current value, but since the configuration is known, a description thereof will be omitted. Furthermore, of the currents thus measured, those moving from upstream to downstream are considered to have positive values, and those moving from downstream to upstream are considered to have negative values.

[0038] The individual current transformer 21 passes through the upstream side of the positive wire 12 and measures the current A1 at the position where it is passed through. The individual current transformer 22 passes through the downstream side (load device 14 side) of the position where the negative wire 13 is connected to the ground wire 18 and measures the current A2 at the position where it is passed through. The positive wire 12 and the negative wire 13 at the positions where they pass through these individual current transformers 21, 22 are separated by an amount that makes it difficult to pass through one current transformer together.

[0039] The zero-phase current transformer 23 passes through the positive and negative wires 12 and 13 downstream of the positions where they pass through the individual current transformers 21 and 22, and measures a total current A3 obtained by adding up the current in the positive wire 12 and the current in the negative wire 13 at the positions where they pass through. Since the current in the positive wire 12 and the current in the negative wire 13 flow in opposite directions, the total current A3 is the difference between the absolute values ​​of these currents. Similarly, the sum of the currents A1 and A2 is the difference between the absolute value of the currents A1 and A2. The positive and negative wires 12 and 13 at the positions where they pass through the zero-phase current transformer 23 are close enough to each other to maintain insulation from each other.

[0040] The reference detection unit 24 is a known voltmeter, and is connected to the positive electrode line 12 and the negative electrode line 13 so as to measure the voltage V1 of the battery 11. Since the positive electrode line 12 and the negative electrode line 13 have no branches, the voltage V1 of the battery 11 is essentially substantially the same as the voltage between the positive electrode line 12 and the negative electrode line 13 at the positions where the individual current transformers 21, 22 are disposed. In other words, the reference detection unit 24 measures the voltage V1 at the positions of the individual current transformers 21, 22.

[0041] A method for monitoring leakage current (leakage current detection method) using such leakage current measuring instrument 20 will be described with reference to Fig. 1 and Fig. 2. Fig. 2(a) is a graph showing the time-dependent changes in currents A1, A2 and total current A3 measured by individual current transformers 21, 22 and zero-phase current transformer 23. Fig. 2(b) is a graph showing the time-dependent changes in leakage current value L1 calculated according to currents A1, A2 (hereinafter abbreviated as "leakage value L1") and leakage current value L2 calculated according to total current A3 (hereinafter abbreviated as "leakage value L2"), respectively.

[0042] The vertical axis of the graphs in Fig. 2(a) and Fig. 2(b) is the absolute value of the current [A]. The horizontal axis of the graphs in Fig. 2(a) and Fig. 2(b) is the time [s]. In addition, in the graph in Fig. 2(a), the change over time of the current A1 of the individual current transformer 21 is shown by a solid line, the change over time of the current A2 of the individual current transformer 22 is shown by a dashed line, and the change over time of the total current A3 of the zero-phase current transformer 23 is shown by a two-dot chain line. In the graph in Fig. 2(b), the change over time of the leakage current value L1 is shown by a solid line, and the change over time of the leakage current value L2 is shown by a two-dot chain line. Furthermore, in the graphs in Fig. 2(a) and Fig. 2(b), the lines that actually overlap are shown slightly shifted from each other in order to make the graphs easier to read.

[0043] When no leakage current is occurring in the measurement object 10, basically, all of the current that flows from the battery 11 through the positive electrode line 12 (individual current transformer 21) to the load device 14 returns from the load device 14 through the negative electrode line 13 (individual current transformer 22) to the battery 11. Therefore, during a time when no leakage current is occurring, the absolute values ​​of the currents A1 and A2 of the individual current transformers 21 and 22 are the same in the graph of Fig. 2(a), and the leakage value L1 is 0 A in the graph of Fig. 2(b).

[0044] On the other hand, for example, when only leakage current occurs from the load device 14 to the housing 14a and no other leakage current occurs, the leakage current passes through the ground wire 18, bypasses the individual current transformer 22 and the zero-phase current transformer 23, and returns to the battery 11 from the negative pole line 13. In other words, the current that passes through the individual current transformer 21 and the zero-phase current transformer 23 toward the load device 14 is divided into a normal route that passes through the individual current transformer 22 and the zero-phase current transformer 23, and a leakage current route that returns to the battery 11 without passing through them.

[0045] As a result, in the graph of Fig. 2(a), during the time when only the leakage current of the load device 14 occurs, the current A2 of the individual current transformer 22 decreases relative to the current A1 of the individual current transformer 21. Therefore, in the graph of Fig. 2(b), during the same time, the leakage value L1 occurring in the measurement object 10 downstream of the individual current transformers 21, 22 is shown based on the sum (difference in absolute values) of the currents A1 and A2. Similarly, during the time when the leakage current occurs, the total current A3 of the zero-phase current transformer 23 increases, and based on that total current A3, the leakage value L2 occurring in the measurement object 10 downstream of the zero-phase current transformer 23 is shown.

[0046] As shown in Fig. 2(a), when the currents A1 and A2 of the individual current transformers 21 and 22 fluctuate, the sum of them also fluctuates slightly. Similarly, when the currents of the positive electrode line 12 and the negative electrode line 13 passing through the zero-phase current transformer 23 fluctuate, the total current A3 obtained by summing them also fluctuates slightly. These currents A1 and A2 and the total current A3 fluctuate mainly according to the voltage V1 of the battery 11. In Fig. 2(a), the voltage V1 at the time when the currents A1 and A2 were acquired is shown above the graphs of the currents A1 and A2. The voltage V1 of the battery 11 changes depending on the remaining charge of the battery 11, deterioration over time, etc.

[0047] The graph in Fig. 2(b) shows the corrected (converted) leakage current values ​​L1 and L2 when the voltage V1 is 800 V. Specifically, when the voltage V1 is 800 V, the sum of the currents A1 and A2 is taken as the corrected leakage current value L1, and the total current A3 is taken as the corrected leakage current value L2.

[0048] When the voltage V1 is 600V, the sum of the currents A1 and A2 is multiplied by approximately 1.33 (=800V / 600V) to obtain the corrected leakage value L1, and the total current A3 multiplied by approximately 1.33 is the corrected leakage value L2. When the voltage V1 is 900V, the sum of the currents A1 and A2 is multiplied by approximately 0.89 (=800V / 900V) to obtain the corrected leakage value L1, and the total current A3 multiplied by approximately 0.89 is the corrected leakage value L2. Therefore, for example, when determining whether the leakage values ​​L1 and L2 exceed the threshold value, the determination can be prevented from being affected by the fluctuation of the voltage V1. That is, the range in which the detection accuracy of the leakage current can be ensured can be widened by such correction by the voltage V1.

[0049] In addition, since the individual current transformers 21, 22 and the zero-phase current transformer 23 are separated on the upstream and downstream sides, the cause of the leakage current can be easily analyzed by comparing the leakage current values ​​L1, L2 according to the measurement results.

[0050] 2(b), the leakage current value L1 occurring in the object to be measured 10 downstream of the individual current transformers 21 and 22 is the same as the leakage current value L2 occurring in the object to be measured 10 downstream of the zero-phase current transformer 23. From this, it is presumed that the leakage current has occurred in the object to be measured 10 only downstream of the zero-phase current transformer 23.

[0051] 2(b), only leakage current L1 occurs, and leakage current L2 does not occur. From this, it is estimated that leakage current occurs from the negative electrode wire 13 upstream of the zero-phase current transformer 23 and downstream of the individual current transformer 22 to the ground or the like.

[0052] According to the two peaks (parts P3 and P4) on the right side of the graph in Fig. 2(b), the leakage current L2 is smaller than the leakage current L1. From this, it is estimated that the leakage current L2 occurs downstream of the zero-phase current transformer 23, and that the leakage current occurring in the negative electrode wire 13 between the zero-phase current transformer 23 and the individual current transformer 22 is the difference between the leakage current L1 and the leakage current L2. That is, it is estimated that the leakage current occurs in at least two places in this case.

[0053] The route of the leakage current changes depending on the location where the leakage current occurs, and the way in which the currents A1 and A2 (leakage value L1) and the total current A3 (leakage value L2) fluctuate also changes. For example, it is possible that the current A2 fluctuates according to the voltage V1 regardless of whether or not a leakage current occurs, and when a leakage current occurs, only the current A1 increases relative to the current A2 by the amount of the leakage current.

[0054] Furthermore, when both currents A1 and A2 fluctuate according to voltage V1 and current A2 drops relative to current A1, it can be estimated from the measurement results of leakage current meter 20 that a leakage current has occurred downstream of individual current transformers 21 and 22 at the point when current A2 drops, without having to calculate leakage current value L1.

[0055] As described above, the earth leakage measuring instrument 20 can monitor (calculate) the leakage current occurring downstream of the individual current transformers 21, 22 from the measurement results by the individual current transformers 21, 22, and can monitor the leakage current occurring downstream of the zero-phase current transformer 23 from the measurement results by the zero-phase current transformer 23. That is, in the earth leakage measuring instrument 20, one measurement unit capable of monitoring the leakage current is configured by one pair of the individual current transformers 21, 22, and another measurement unit capable of monitoring the leakage current is configured by one zero-phase current transformer 23.

[0056] In particular, with the measurement unit using individual current transformers 21 and 22, since positive electrode line 12 and negative electrode line 13 each pass through them individually, even if positive electrode line 12 and negative electrode line 13 are separated from each other, the sum of currents A1 and A2 flowing therethrough can be calculated, thereby making it possible to monitor the leakage current. As a result, the objects for which leakage current can be monitored by leakage current measuring instrument 20 can be expanded.

[0057] Furthermore, the number of current transformers can be reduced by using the zero-phase current transformer 23 instead of the individual current transformers 21, 22. Furthermore, even in a position where the positive electrode wire 12 and the negative electrode wire 13 are bundled together and cannot be individually passed through the individual current transformers 21, 22, the total current at that position can be measured by the zero-phase current transformer 23. As a result, the degree of freedom in the placement of the measuring unit that monitors the leakage current can be improved, making it easier to analyze the cause of the leakage current.

[0058] Next, the control of the earth leakage measuring instrument 20 will be described in more detail with reference to Fig. 3 to Fig. 7. Fig. 3 is a block diagram showing the electrical configuration of the earth leakage measuring instrument 20. The earth leakage measuring instrument 20 has a CPU 25, a flash ROM 26, and a RAM 27, which are each connected to an input / output port 29 via a bus line 28. The input / output port 29 is further connected to a communication device 30, individual current transformers 21 and 22, a zero-phase current transformer 23, and a reference detection unit 24, respectively.

[0059] The communication device 30 is connected to an external control device 40, and transmits and receives information to and from the external control device 40. The external control device 40 is a device that analyzes the cause of leakage current based on the measurement results of the individual current transformers 21, 22, the zero-phase current transformer 23, and the reference detection unit 24. Furthermore, a load device 14 is connected to the external control device 40, and it is configured so that the cause of leakage current can be analyzed using the operating state of the load device 14, etc.

[0060] The CPU 25 is a calculation device that controls each part connected by a bus line 28. The flash ROM 26 is a rewritable non-volatile memory that stores programs executed by the CPU 25, fixed value data, etc., and includes a monitoring program 26a, a unique number memory 26b, a peak detection memory 26c, a short-term change detection memory 26d, a long-term change detection memory 26e, and a cycle collection memory 26f. Note that instead of the flash ROM 26, a storage device such as an SSD or HDD may be used.

[0061] When the monitoring program 26a is executed by the CPU 25, the main process of Fig. 4 is executed. The unique number memory 26b is a memory in which the unique number of the earth leakage measuring instrument 20 is stored. This unique number is part of the information for identifying the measurement object 10 whose leakage current is monitored by the earth leakage measuring instrument 20. This unique number is necessary when there are multiple earth leakage measuring instruments 20 connected to the external control device 40. On the other hand, when there is only one earth leakage measuring instrument 20, there is no need to identify the measurement object 10 by the unique number, and so the unique number memory 26b may be omitted.

[0062] The peak detection memory 26c, the short-term change detection memory 26d, the long-term change detection memory 26e, and the cycle collection memory 26f are all memories for storing data relating to the leakage current values ​​L1, L2 until the data is transmitted to the external control device 40. That is, each of these memories 26c to 26f stores data that is permitted to be transmitted to the external control device 40.

[0063] The RAM 27 is a memory for rewritably storing various work data, flags, etc. when the CPU 25 is executing a program, and is provided with an upstream ring buffer 27a, a downstream ring buffer 27b, an upstream average ring buffer 27c, a downstream average ring buffer 27d, and a voltage ring buffer 27e.

[0064] The upstream ring buffer 27a is configured as a known ring buffer and stores the leakage current value L1 calculated every 1 ms for the past minute by correcting the sum of the currents A1 and A2 with the voltage V1. Specifically, the upstream ring buffer 27a stores (overwrites) the latest leakage current value L1 at the latest position of multiple storage areas. This latest position is a storage area in which the leakage current value L1 from one minute ago is stored, and the multiple storage areas correspond to the latest positions in order. Furthermore, the upstream ring buffer 27a is configured to make the latest position the current time and to know the time when each leakage current value L1 was stored (the time when the leakage current value L1 was calculated).

[0065] Each of the ring buffers 27b to 27e is configured the same as the upstream ring buffer 27a, except for the contents of the data stored and the storage capacity. The downstream ring buffer 27b stores the leakage current value L2 calculated every 1 ms by correcting the total current A3 with the voltage V1 for the past minute. The upstream average ring buffer 27c stores the average value M1 obtained by averaging all leakage current values ​​L1 measured during one minute for the past 10 minutes. The downstream average ring buffer 27d stores the average value M2 obtained by averaging all leakage current values ​​L2 measured during one minute for the past 10 minutes. The voltage ring buffer 27e stores the voltage V1 measured by the reference detection unit 24 every 1 ms for the past 10 minutes.

[0066] Next, main processing executed by the CPU 25 of the earth leakage measuring instrument 20 will be described with reference to Fig. 4 to Fig. 7. Fig. 4 is a flowchart of the main processing of the earth leakage measuring instrument 20. Fig. 5 is a flowchart of the peak detection processing S20. Fig. 6 is a flowchart of the average detection processing S21. Fig. 7 is a flowchart of the cycle collection processing S22.

[0067] The main processing of the earth leakage measuring instrument 20 is executed every 1 ms while the power of the earth leakage measuring instrument 20 is on. The peak detection process S20, the average detection process S21, and the cycle collection process S22 are executed during the main processing of the earth leakage measuring instrument 20.

[0068] 4, the main process first acquires a current A1 measured by the individual current transformer 21 (S11). Next, a current A2 measured by the individual current transformer 22 is acquired (S12). Next, a total current A3 measured by the zero-phase current transformer 23 is acquired (S13). Next, a voltage V1 measured by the reference detection unit 24 is acquired, and the voltage V1 is stored in the voltage ring buffer 27e (S14).

[0069] In addition, in the series of steps S11 to S14, the currents A1 and A2, the total current A3, and the voltage V1 are measured at the same timing. This is to accurately calculate the leakage current values ​​L1 and L2 that occurred during the measurements. However, the timings at which the currents A1 and A2, the total current A3, and the voltage V1 are measured in the steps S12 to S14 may be different from each other.

[0070] After the process of S14, the reference voltage Vs, which is the reference value of the voltage V1, is set to 800 V (S15). The reference voltage Vs may be set according to the voltage of the battery 11 in the normal state. For example, if the normal voltage is 350 to 450 V, the reference voltage Vs is set to 400 V in the process of S15.

[0071] After the process of S15, the sum (difference in absolute value) of current A1 and current A2 is corrected to the value at reference voltage Vs to calculate leakage current value L1=(A1+A2)·Vs / V1 based on these values ​​(S16). This calculated leakage current value L1 is temporarily stored in the latest position of the upstream ring buffer 27a (S17).

[0072] Next, the total current A3 is corrected to the value at the reference voltage Vs to calculate a leakage current value L2=A3·Vs / V1 (S18). This calculated leakage current value L2 is temporarily stored in the latest position of the downstream ring buffer 27b (S19).

[0073] Thereafter, based on the temporarily stored leakage current values ​​L1, L2, a peak detection process S20, an average detection process S21, and a cycle collection process S22 are sequentially executed to determine whether or not to store data relating to the leakage current values ​​L1, L2 so that the data can be transmitted to the external control device 40.

[0074] The peak detection process S20 in Fig. 5 will be described with reference to Fig. 2(b). The peak detection process S20 is a process for storing the leakage current value L1 temporarily stored in the upstream ring buffer 27a in the peak detection memory 26c for analysis by the external control device 40 when the leakage current value L1 is a value suspected of being abnormal or a value requiring a caution or warning. Basically, since the leakage current value L2 is equal to or less than the leakage current value L1, the peak detection process S20 does not use the leakage current value L2 to determine whether or not storage is required, and when the leakage current value L1 is stored in the peak detection memory 26c, the leakage current value L2 at the same time is also stored in the peak detection memory 26c.

[0075] In the peak detection process S20, first, it is determined whether the leakage current value L1 stored in the latest position of the upstream ring buffer 27a has changed from less than the threshold to more than the threshold, i.e., whether the leakage current value L1 at the previous position is less than the threshold and the leakage current value L1 at the latest position is more than the threshold (S41). An example of this threshold is 1 mA. If the leakage current value L1 is more than the threshold, it is suspected that an abnormal leakage current is occurring in the measurement object 10 monitored by the leakage current meter 20. However, in order to prevent the occurrence of an abnormal leakage current, a value smaller than a value that is determined to be abnormal may be set as the threshold. A value larger than 1 mA may also be set as the threshold.

[0076] In the process of S41, if the leakage current value L1 at the latest position goes from less than the threshold to equal to or greater than the threshold (S41: Yes), it is confirmed whether the start position S (see FIG. 2(b)) for specifying the range to be stored in the peak detection memory 26c has not been set (S42). Note that if the leakage current value L1 remains less than the threshold for 15 seconds or more, the start position S is not set (cleared).

[0077] If the start position S has not been set (S42: Yes), the start position S is set to the position 15 seconds before the most recent position where the leakage current value L1 became equal to or greater than the threshold value among the multiple memory positions in the upstream ring buffer 27a (S43), and the peak detection process S20 is terminated.

[0078] In the process of S41, if the leakage current value L1 at the latest position has not changed from less than the threshold value to greater than or equal to the threshold value (S41: No), it is determined whether the leakage current value L1 stored at the latest position of the upstream ring buffer 27a has changed from greater than or equal to the threshold value to less than the threshold value (S45).If the leakage current value L1 has changed from greater than or equal to the threshold value to less than the threshold value (S45: Yes), since the start position S has already been set in the process of S43, the end position E (see FIG. 2(b)) corresponding to the start position S is set (S46), and the peak detection process S20 is terminated.

[0079] Specifically, in the process of S46, among the multiple memory positions of the upstream ring buffer 27a, the position 15 seconds after the latest position where the leakage current value L1 became less than the threshold value is set as the end position E. The range from the start position S to the end position E in the upstream ring buffer 27a is the range to be stored in the peak detection memory 26c.

[0080] At the start of the peak detection process S20, if the leakage current value L1 at the latest position does not cross the threshold (S41: No and S45: No), it is confirmed whether a new leakage current value L1 has been stored at the end position E of the upstream ring buffer 27a (S47). That is, in the process of S47, it is confirmed whether 15 seconds have passed since the leakage current value L1 became less than the threshold while remaining less than the threshold.

[0081] In the process of S47, if a new leakage value L1 is stored at the end position E (S47: Yes), all the leakage values ​​L1 within the range to be stored in the peak detection memory 26c are now stored in the peak detection memory 26c (S48). Furthermore, in the process of S48, the time corresponding to the leakage value L1, and the leakage value L2 and voltage V1 at that time are stored in the peak detection memory 26c in association with the leakage value L1. These leakage values ​​L2 and voltage V1 are stored in the upstream ring buffer 27a and the voltage ring buffer 27e, respectively.

[0082] Although not shown, the peak detection memory 26c specifically includes a time memory in which the time is stored, an L1 memory in which the leakage current value L1 is stored, an L2 memory in which the leakage current value L2 is stored, and a voltage memory in which the voltage V1 is stored.

[0083] The time stored in the time memory is the time when the currents A1 and A2 for calculating the leakage value L1 were measured (acquired), the time when the total current A3 for calculating the leakage value L2 was measured, and the time when the voltage V1 was measured. That is, the leakage value L1, the leakage value L2, and the voltage V1 are stored in the peak detection memory 26c in association with each other by time. This makes it possible to analyze the cause of the leakage value L1 (the value of the leakage current) becoming so large that an abnormality is suspected, by comparing the leakage values ​​L1 and L2 with each other and with the voltage V1.

[0084] After the process of S48, the settings of the start position S and the end position E are cleared (S49) so that a new start position S can be set in the processes of S41 to S43, and the peak detection process S20 is terminated.

[0085] Here, a case will be described in which after the start position S is set in the process of S43, the leakage current value L1 falls below the threshold value (S45: Yes), and the end position E is set in the process of S46, the leakage current value L1 at the latest position goes from below the threshold value to equal to or above the threshold value (S41: Yes) before the leakage current value L1 is stored at the end position E. That is, a method for setting the end position will be described in which, for example, peaks P3 and P4 occur in succession within a short period of time as shown in Fig. 2(b).

[0086] In this case, when the process proceeds to S42, both the start position S and the end position E have already been set (S42: No), so the start position S is not reset in the process of S43, and only the end position E is cleared so that it can be reset (S44, see the dashed line in FIG. 2(b)), and the peak detection process S20 ends. Thereafter, if the latest leakage value L1 again goes from being equal to or greater than the threshold to being less than the threshold (S45: Yes), the end position E is reset (S46), and the leakage value L1 from the start position S to the end position E can be stored in the peak detection memory 26c by the processes of S47 and S48.

[0087] In this way, even if the leakage current value L1 is equal to or greater than the threshold value consecutively in a short period of time, the leakage current value L1 for a plurality of consecutive ranges equal to or greater than the threshold value and for 15 seconds before and after the ranges can be stored in the peak detection memory 26c. That is, it is possible to avoid a situation in which some of the ranges in which the leakage current value L1 is equal to or greater than the threshold value are not stored in the peak detection memory 26c. In addition, compared to a case in which the start position S and the end position E are individually set for the plurality of ranges in which the leakage current value L1 is equal to or greater than the threshold value, the peak detection process S20 can be simplified and duplicated data can be prevented from being stored in the peak detection memory 26c.

[0088] If the process of S47 does not store a new leakage value L1 at the end position E (S47: No), it is confirmed whether the position at which the leakage value L1 is to be stored next in the upstream ring buffer 27a is the start position S (S50). If the position at which the leakage value L1 is to be stored next is not the start position S (S50: No), the peak detection process S20 is terminated.

[0089] On the other hand, if the next position to be stored is the start position S (S50: Yes), the leakage values ​​L1, L2 to be stored in the peak detection memory 26c will be erased in order from the oldest due to the new leakage values ​​L1, L2 being stored in the upstream ring buffer 27a and the downstream ring buffer 27b from the next time onwards. Therefore, just before the old leakage values ​​L1, L2 are erased (S50: Yes), all leakage values ​​L1 stored in the upstream ring buffer 27a, the times corresponding to those leakage values ​​L1, and the leakage values ​​L2 and voltages V1 at those times are stored in the peak detection memory 26c in association with each other (S51).

[0090] In the peak detection process S20 after the process of S51, if a new leakage current value L1 is stored at the end position E (S47: Yes), in the process of S48, the leakage current value L1 stored in the upstream ring buffer 27a immediately after the process of S51 is set as a new start position S, and the leakage current value L1 after the process of S51 and the like are stored in the peak detection memory 26c. Therefore, by the processes of S50 and S51, the leakage current value L1 that is equal to or greater than the threshold, the leakage current values ​​L1 for 15 seconds before and after that, and the leakage current value L2 at the same time can all be stored in the peak detection memory 26c without increasing the capacity of the upstream ring buffer 27a and the downstream ring buffer 27b.

[0091] Next, the average detection process S21 will be described with reference to Fig. 6. The average detection process S21 is a process for storing an average value M1 (an average value of all leakage values ​​L1 measured within one minute) and an average value M2 (an average value of all leakage values ​​L2 measured within one minute) in the short-term change detection memory 26d and the long-term change detection memory 26e in order to analyze the short-term or long-term increase trend of the leakage values ​​L1 and L2 by the external control device 40 while eliminating the influence of the leakage values ​​L1 and L2 that momentarily increase due to noise, etc. In the average detection process S21, similarly to the peak detection process S20, the average value M2 based on the leakage value L2 is not used to determine whether or not storage is required, and when the average value M1 is stored in the short-term change detection memory 26d and the long-term change detection memory 26e, the average value M2 at the same time is also stored in each memory 26d, 26e.

[0092] As shown in Fig. 6, in the average detection process S21, first, it is confirmed whether one minute has passed since the calculation of the previous average values ​​M1, M2, that is, whether all the values ​​in the upstream ring buffer 27a and the downstream ring buffer 27b that respectively store the leakage values ​​L1, L2 for the past minute have been updated (S61). Immediately after the power supply of the leakage measuring instrument 20 is turned on, invalid values ​​are stored in each memory of the upstream ring buffer 27a and the downstream ring buffer 27b, and in the process of S61 immediately after turning on, it is confirmed whether all the invalid values ​​have been updated with the leakage values ​​L1, L2. In the process of S61, if one minute has not passed since the calculation of the previous average values ​​M1, M2 or the power supply was turned on (S61: No), the average detection process S21 is terminated and one minute is awaited.

[0093] On the other hand, if one minute has passed since the previous calculation of the average values ​​M1 and M2 or the power was turned on (S61: Yes), the values ​​in the upstream ring buffer 27a and the downstream ring buffer 27b have all been updated, so the leakage values ​​L1 for the most recent minute stored in the upstream ring buffer 27a are averaged to calculate an average value M1, and the average value M1 is stored in the upstream average ring buffer 27c (S62). Similarly, the leakage values ​​L2 for the most recent minute stored in the downstream ring buffer 27b are averaged to calculate an average value M2, and the average value M2 is stored in the downstream average ring buffer 27d (S63).

[0094] Next, the rate of change of the average value M1 for the most recent minute relative to the average value M1 from 2 to 1 minute ago stored in upstream average ring buffer 27c (the average value M1 calculated in the process of S62 1 minute ago, which is the average of the multiple leakage values ​​L1 calculated from 2 to 1 minute ago) is calculated as the short-term rate of change (S64). Specifically, it is calculated as (short-term rate of change)=((average value M1 for the most recent minute)-(average value M1 from 2 to 1 minute ago)) / (average value M1 from 2 to 1 minute ago).

[0095] It is then confirmed whether the calculated short-term change rate is equal to or greater than a change threshold value (S65). Note that the change threshold value is set to, for example, 1.1 in order to eliminate noise, but may be changed as long as it is a number equal to or greater than 1.

[0096] If the short-term change rate is greater than or equal to the change threshold in the processing of S65 (S65: Yes), the average values ​​M1 for the most recent two minutes stored in the upstream average ring buffer 27c (all average values ​​M1 calculated in the processing of S62 for the most recent two minutes), the time corresponding to these average values ​​M1, and the average value M2 and voltage V1 at that time are stored in association with each other in the short-term change detection memory 26d (S66), and the processing proceeds to S67.

[0097] The average value M2 at the time corresponding to the average value M1 for the most recent two minutes is the average value M2 for the most recent two minutes stored in downstream average ring buffer 27d (all average values ​​M2 calculated in the process of S63 for the most recent two minutes). The voltage V1 at the time corresponding to the average value M1 for the most recent two minutes is the voltage V1 for the most recent two minutes stored in voltage ring buffer 27e.

[0098] Although not shown, the short-term change detection memory 26d specifically includes a time memory in which time is stored, an M1 memory in which an average value M1 is stored, an M2 memory in which an average value M2 is stored, and a voltage memory in which a voltage V1 is stored. That is, the short-term change detection memory 26d is obtained by replacing the L1 memory and the L2 memory of the peak detection memory 26c with the M1 memory and the M2 memory. The M1 memory and the M2 memory store the average values ​​M1 and M2 in a manner that corresponds to the time when the oldest leakage values ​​L1 and L2 used in calculating the average values ​​M1 and M2 were calculated.

[0099] If the short-term change rate is less than the change threshold in the process of S65 (S65: No), the process skips the process of S66 and proceeds to the process of S67. This makes it possible to analyze the increasing trend of the short-term average value M1 while excluding cases where the short-term change rate is decreasing or where the short-term change rate is only slightly increased due to noise or the like.

[0100] In the process of S67, the rate of change of the average value M1 for the most recent minute relative to the average value M1 for 10 to 9 minutes ago stored in the upstream average ring buffer 27c (the average value M1 calculated in the process of S62 9 minutes ago, which is the average of the multiple leakage values ​​L1 calculated for 10 to 9 minutes ago) is calculated as the long-term rate of change. Specifically, it is calculated as (long-term rate of change)=((average value M1 for the most recent minute)-(average value M1 for 10 to 9 minutes ago)) / (average value M1 for 10 to 9 minutes ago).

[0101] It is then confirmed whether the calculated long-term change rate is equal to or greater than a change threshold value (e.g., 1.1) (S68). If the long-term change rate is equal to or greater than the change threshold value (S68: Yes), the average values ​​M1 for the most recent 10 minutes stored in the upstream average ring buffer 27c (all average values ​​M1 calculated in the process of S63 for the most recent 10 minutes), the time corresponding to these average values ​​M1, and the average value M2 and voltage V1 at that time are stored in the long-term change detection memory 26e in association with each other (S69), and the average detection process S21 is terminated.

[0102] The average value M2 at the time corresponding to the average value M1 for the most recent 10 minutes is the average value M2 for the most recent 10 minutes stored in downstream average ring buffer 27d (all average values ​​M2 calculated in the process of S63 for the most recent 10 minutes). The voltage V1 at the time corresponding to the average value M1 for the most recent 10 minutes is the voltage V1 for the most recent 10 minutes stored in voltage ring buffer 27e. In addition, long-term change detection memory 26e is configured in the same way as short-term change detection memory 26d.

[0103] If the long-term change rate is less than the change threshold in the process of S68 (S68: No), the process of S69 is skipped and the average detection process S21 is terminated. This makes it possible to analyze the increasing trend of the long-term average value M1 while excluding cases where the long-term change rate is decreasing or where the long-term change rate is only slightly increased due to noise or the like.

[0104] Next, the cycle collection process S22 will be described with reference to Fig. 7. The cycle collection process S22 is a process for periodically storing the leakage current values ​​L1 and L2 in the cycle collection memory 26f even if there is no abnormality, in order to analyze fluctuations in the leakage current values ​​L1 and L2 over an extremely long period, such as several months or several years.

[0105] 7, in the cyclic collection process S22, first, it is confirmed whether a regular collection timing has arrived (S71). In this embodiment, the regular collection timing is set to every hour, but the collection timing may be changed as appropriate.

[0106] If the periodic collection timing has not arrived (S71: No), the cycle collection process S22 is terminated and the arrival of the collection timing is awaited. On the other hand, if the periodic collection timing has arrived (S71: Yes), all leakage values ​​L1 (for the most recent minute) stored in the upstream ring buffer 27a, all leakage values ​​L2 (for the most recent minute) stored in the downstream ring buffer 27b, the time corresponding to the leakage values ​​L1 and L2, and the voltage V1 at that time are stored in the cycle collection memory 26f in association with each other (S72), and the cycle collection process S22 is terminated. Note that in the process of S72, the voltage V1 at the time corresponding to the leakage values ​​L1 and L2 is the voltage V1 for the most recent minute stored in the voltage ring buffer 27e.

[0107] By periodically acquiring the leakage current value L1, it is possible to analyze the tendency of the leakage current to increase over a very long period, such as several months or several years. For example, the change over time of the actual measured leakage current value L1 in the past can be approximated by the least squares method, and the change over time of the predicted value of the leakage current value L1 in the future can be calculated. From the change over time of the predicted value, it is possible to analyze the approximate date and time when the leakage current value L1 will exceed a threshold value (e.g., 1 mA). This makes it possible to plan a schedule for the maintenance of the measurement object 10, as well as to plan the ordering of devices and parts that need to be replaced. Furthermore, by acquiring the leakage current value L1 and the leakage current value L2 and the voltage V1 at the same time, it is possible to analyze the location of the devices and parts that need to be replaced based on these values.

[0108] Returning to Fig. 4, after the cycle collection process S22, the unsent data stored in the peak detection memory 26c, the short-term change detection memory 26d, the long-term change detection memory 26e, and the cycle collection memory 26f, and the unique number stored in the unique number memory 26b are transmitted to the external control device 40 (S23).

[0109] When the external control device 40 receives each of these data, it stores each of the data in a memory provided for each unique number (measurement target 10). The memories of the external control device 40 are substantially the same as the memories 26c to 26f of the earth leakage measuring instrument 20. The external control device 40 uses each of the data received from the earth leakage measuring instrument 20 to perform an analysis of the cause of the leakage current, etc. It is preferable to use AI data analysis for this analysis.

[0110] The data of each of the memories 26c to 26f transmitted in the process of S23 is data including the leakage current values ​​L1, L2 themselves or data including average values ​​M1, M2 obtained by averaging the leakage current values ​​L1, L2, and is data permitted to be transmitted to and stored in the external control device 40. Therefore, the processes of S41 to S47, S50 in Fig. 5, the processes of S64, S65, S67, S68 in Fig. 6, and the process of S71 in Fig. 7, which determine whether each data should be transmitted to (stored in) the external control device 40, can be said to be processes for determining whether each data should be transmitted to (stored in) the external control device 40.

[0111] In particular, the processes of S41 to S47, and S50 in Fig. 5 and the processes of S64, S65, S67, and S68 in Fig. 6 can be said to be processes for determining, based on the leakage value L1, whether data relating to the leakage values ​​L1 and L2 should be transmitted to (stored in) the external control device 40. Also, the processes of S48 and S51 in Fig. 5, the processes of S66 and S69 in Fig. 6, and the process of S72 in Fig. 7 can be said to be processes for making each piece of data that has been determined to be transmitted (stored) to the external control device 40 transmittable (storable) to the external control device 40.

[0112] This makes it possible to select data effective for analyzing leakage current from data relating to the leakage values ​​L1 and L2 and transmit (store) it to the external control device 40, thereby reducing the frequency and amount of transmission from the leakage measuring instrument 20 to the external control device 40. Furthermore, it is possible to reduce the amount of data stored in the leakage measuring instrument 20 and the external control device 40 per given time, making it easier to reduce the size and cost of the leakage measuring instrument 20 and the external control device 40.

[0113] After the process of S23, other processes are executed (S24), and the main process of the earth leakage measuring instrument 20 is terminated. The process of S24 may include a process for changing the reference voltage Vs, a process for changing the threshold value used in the peak detection process S20, and a process based on a signal received from the external control device 40. For example, if an operation for changing the threshold value used in the peak detection process S20 is performed by the external control device 40 and the earth leakage measuring instrument 20 receives a signal of the change from the external control device 40 via the communication device 30, the process of S24 executes a process for changing the threshold value according to the received signal.

[0114] Next, a second embodiment will be described with reference to Figs. 8 to 11. In the first embodiment, a leakage current meter 20 (leakage monitoring device) that measures leakage current of a measurement object 10 having one load device 14 is described. In contrast, in the second embodiment, a leakage current monitoring device that measures leakage current of a measurement object (vehicle 19) having three load devices 15 to 17 is described. Note that the same parts as in the first embodiment are given the same reference numerals and the following description will be omitted.

[0115] 8 is a circuit diagram showing a schematic diagram of an electric circuit of the earth leakage monitoring device and the object to be measured in the second embodiment. The earth leakage monitoring device in the second embodiment is composed of an earth leakage measuring instrument 50 and a control device 60 of the object to be measured (see FIG. 10).

[0116] The measurement target in the second embodiment is a vehicle 19 (e.g., a pile driver) that is driven by electricity, and a vehicle body 19b is supported by a plurality of wheels 19a so that the vehicle can run. Since the vehicle body 19b is a large conductor, "grounding" in the second embodiment refers to electrically connecting to the vehicle body 19b as described above.

[0117] Vehicle 19 is equipped with a battery 11 that outputs DC power (load power), a positive electrode line 12 connected to the positive electrode of battery 11, a negative electrode line 13 connected to the negative electrode of battery 11, and a number of load devices 15, 16, and 17 that each operate using DC power supplied from battery 11 via the positive electrode line 12 and negative electrode line 13.

[0118] The positive line 12 and the negative line 13 are a pair of power lines for supplying DC power from the upstream battery 11 to the downstream load devices 15 to 17. The positive line 12 includes a main electric line 12a connected to the battery 11, and a plurality of branch electric lines 12b, 12c, and 12d each branching off from the main electric line 12a. Similarly, the negative line 13 includes a main electric line 13a connected to the battery 11, and a plurality of branch electric lines 13b, 13c, and 13d each branching off from the main electric line 13a.

[0119] The main electric wires 12a and 13a are similarly configured as a pair to collect the upstream sides of a pair of power lines branching out toward a plurality of load devices 15 to 17. The branch electric wires 12b and 13b are connected to the load device 15, respectively, to configure a pair of the power lines on the downstream side. Similarly, the branch electric wires 12c and 13c are connected to the load device 16, respectively, to configure a pair of the power lines on the downstream side, and the branch electric wires 12d and 13d are connected to the load device 17, respectively, to configure a pair of the power lines on the downstream side. In this manner, the pair of power lines in this embodiment branches out from the pair on the upstream side into multiple pairs on the downstream side.

[0120] Examples of the load devices 15-17 include an inverter, a control device 60 (see FIG. 10), a DC motor, etc. The load devices 15-17 are housed in housings 15a, 16a, and 17a, respectively, which are grounded via a ground wire 18. When a leakage current occurs from the load devices 15-17 to the housings 15a-17a, the leakage current returns to the negative electrode of the battery 11, for example, from the ground wire 18 through the vehicle body 19b, the surface of the housing of the battery 11, etc., even if the negative electrode wire 13 is not grounded.

[0121] In the second embodiment, similarly to the first embodiment, the negative electrode line 13 may be grounded by the ground wire 18. In this case, the leakage current is likely to return to the negative electrode line 13 through the ground wire 18, and the route of the leakage current is likely to be determined, making it easier to analyze the cause of the leakage current. Therefore, information on whether the negative electrode line 13 is grounded or not may be included in the operating state data described later.

[0122] The earth leakage measuring instrument 50 is a device for monitoring a leakage current occurring in the vehicle 19, which is a measurement target, and is mounted on the vehicle 19. The earth leakage measuring instrument 50 includes an individual current transformer 21 through which the trunk electric wire 12a passes, an individual current transformer 22 through which the trunk electric wire 13a passes, an individual current transformer 51 through which the branch electric wire 12b passes, an individual current transformer 52 through which the branch electric wire 13b passes, an individual current transformer 53 through which the branch electric wire 12c passes, an individual current transformer 54 through which the branch electric wire 13c passes, an individual current transformer 55 through which the branch electric wire 12d passes, an individual current transformer 56 through which the branch electric wire 13d passes, and a reference detection unit 24 that measures the voltage between the positive electrode wire 12 and the negative electrode wire 13. Each of the individual current transformers (individual measuring instruments) 51 to 56 is a measuring instrument constituted by a ring-shaped current transformer through which the electric wire to be measured passes, and measures the value of the current flowing through the passing portion.

[0123] As described in the first embodiment, the set of individual current transformers 21 and 22 constitutes one measurement unit capable of monitoring (calculating) a leakage current in a predetermined range by summing up the currents A1 and A2 that are the respective measurement results. Furthermore, the set of individual current transformers 51 and 52, the set of individual current transformers 53 and 54, and the set of individual current transformers 55 and 56 each constitute one measurement unit capable of monitoring (calculating) a leakage current in a predetermined range by summing up the currents that are the measurement results, similar to the set of individual current transformers 21 and 22.

[0124] The measurement unit using the individual current transformers 21 and 22 can easily calculate the sum of the leakage current value L1 occurring downstream of itself, which is the leakage current value L2 to L4 occurring in the load devices 15 to 17, and the value of the leakage current occurring between the individual current transformers 21 and 22 and the individual current transformers 51 to 56. The measurement unit using the individual current transformers 51 and 52 can calculate the leakage current value L2 occurring downstream of itself, which is the leakage current value L2 occurring in the load device 15, without being affected by the leakage current values ​​L3 and L4 of the other load devices 16 and 17.

[0125] Similarly, the measurement unit using individual current transformers 53 and 54 can calculate leakage current value L3 occurring in load device 16 without being affected by leakage current values ​​L2 and L4. Furthermore, the measurement unit using individual current transformers 55 and 56 can calculate leakage current value L4 occurring in load device 17 without being affected by leakage current values ​​L2 and L3.

[0126] In this way, the leakage current meter 50 can calculate the leakage current values ​​L1 to L4 at a plurality of locations, and by comparing these values, it is possible to easily analyze the cause of the leakage current occurring in the vehicle 19. This analysis method will be described with reference to FIG.

[0127] Fig. 9 is a graph showing the change over time of leakage current values ​​L1 to L4. The vertical and horizontal axes of this graph are the same as those of the graph of Fig. 2(b) described in the first embodiment. In the graph of Fig. 9, the change over time of leakage current value L1 is shown by a solid line, the change over time of leakage current value L2 by a dashed line, the change over time of leakage current value L3 by a dashed line, and the change over time of leakage current value L4 by a dashed line. Furthermore, in this graph, the lines in the overlapping parts are shown slightly shifted from each other in order to make the graph easier to read.

[0128] According to the leftmost peak (part P5) of the graph in Fig. 9, the leakage current value L1 due to individual current transformers 21 and 22 is the same as the leakage current value L2 due to individual current transformers 51 and 52, and the leakage current value L3 due to individual current transformers 53 and 54 and the leakage current value L4 due to individual current transformers 55 and 56 are 0 A. From this, it is estimated that a leakage current has occurred in vehicle 19 only downstream of individual current transformers 51 and 52 (at load device 15).

[0129] According to the peak (part P6) in the center of the left and right of the graph in Fig. 9, leakage current L2 is 0 A, and the sum of leakage current values ​​L3 and L4 is equal to leakage current value L1. From this, it is estimated that leakage current has occurred in vehicle 19 on the downstream side of individual current transformers 53 and 54 (load device 16) and on the downstream side of individual current transformers 55 and 56 (load device 17).

[0130] According to the rightmost peak (part P7) of the graph in Figure 9, leakage current L1 increases in two stages toward the right. In the first stage, the sum of leakage current L2 and L3 is equal to leakage current L1, and leakage current L4 is 0A. In the second stage, leakage current L2 and L3 remain unchanged from the first stage, and leakage current L4 increases. From this, it can be inferred that while leakage current is occurring in vehicle 19 downstream of individual current transformers 51 and 52 and downstream of individual current transformers 53 and 54, further leakage current is beginning to occur downstream of individual current transformers 55 and 56.

[0131] In addition, not only when the sum of leakage current values ​​L2, L3, and L4 matches leakage current value L1, but also when they do not match, it is presumed that leakage current has occurred in vehicle 19 downstream of individual current transformers 21, 22 and upstream of individual current transformers 51-56.

[0132] Next, the control device 60 constituting a part of the earth leakage monitoring device will be described in more detail with reference to Fig. 10. Fig. 10 is a block diagram showing the electrical configuration of a measurement object (vehicle 19) equipped with the control device 60. The control device 60 has a CPU 61, an HDD 62, and a RAM 63, which are each connected to an input / output port 65 via a bus line 64. The input / output port 65 is further connected to the battery 11, a cab 66, a traveling device 67, a position detection device 68, a speed sensor 69, a temperature sensor 70, a humidity sensor 71, an earth leakage meter 50, a forecast lamp 72, and an alarm lamp 73.

[0133] The CPU 61 is a computing device that controls each part connected by a bus line 64. The HDD 62 is a rewritable non-volatile memory that stores programs executed by the CPU 61 and various data, and includes a control program 62a, a leakage data memory 62b, and an operating state memory 62c. Note that a storage device such as a flash ROM or SSD may be used instead of the HDD 62.

[0134] When the control program 62a is executed by the CPU 61, the main process of Fig. 11 is executed. The earth leakage data memory 62b is a memory for storing each data received from the earth leakage measuring instrument 50. The operating state memory 62c is a memory for storing operating state data described later.

[0135] The cab 66 is a device operated by an operator to operate the vehicle 19, and is disposed in the cab. The traveling device 67 is a device that causes the vehicle 19 to travel based on the operation of the cab 66. The cab 66 and the traveling device 67 correspond to a part of the load devices 15 to 17.

[0136] The position detection device 68 is a device that detects the current position of the vehicle 19, and in this embodiment, is configured with a GPS receiver that acquires the current position of the vehicle 19 using a GPS. The position detection device 68 is not limited to a GPS receiver, and it is of course possible to adopt other position detection devices. Examples of other position detection devices include a signal receiver that detects the position using a signal emitted from a signal device installed on the ground.

[0137] The speed sensor 69 is a sensor for detecting the traveling speed of the vehicle 19. The position detection device 68 may also function as the speed sensor 69 by calculating the traveling speed of the vehicle 19 from the position information of the position detection device 68. The temperature sensor 70 is a sensor for detecting the temperature (air temperature) around the vehicle 19. The humidity sensor 71 is a sensor for detecting the humidity around the vehicle 19. The temperature sensor 70 and the humidity sensor 71 do not have to be mounted on the vehicle 19.

[0138] The forecast lamp 72 is a device that emits yellow light to advise an operator to perform maintenance on the vehicle 19. The warning lamp 73 is a device that emits red light to notify an operator that maintenance is required on the vehicle 19. The forecast lamp 72 and the warning lamp 73 are disposed in the driver's cab of the vehicle 19.

[0139] The earth leakage measuring instrument 50 of the second embodiment executes substantially the same processes as those of the first embodiment shown in Figs. 4 to 7. The following describes in detail the processes of the earth leakage measuring instrument 50 that differ from those of the first embodiment. First, instead of the process of S13 in Fig. 4, the currents measured by the individual current transformers 51 to 56 are acquired. Instead of the processes of S18 and S19, the earth leakage values ​​L2 to L4 are calculated, and the earth leakage values ​​L2 to L4 are stored in ring buffers provided individually for the earth leakage values ​​L2 to L4. In the process of S23, untransmitted data is transmitted to the control device 60 instead of the external control device 40.

[0140] Furthermore, in the processes of S48 and S51 in Fig. 5, in addition to the leakage values ​​L1 and L2 and the voltage V1, the leakage values ​​L3 and L4 are also stored in the peak detection memory 26c. Instead of the process of S63 in Fig. 6, the leakage values ​​L2 to L4 for the most recent minute are averaged to calculate average values ​​M2 to M4, and the average values ​​M2 to M4 are stored in ring buffers provided individually for the average values ​​M2 to M4. In the processes of S66 and S69, in addition to the average values ​​M1 and M2 and the voltage V1, the average values ​​M3 and M4 are also stored in the short-term change detection memory 26d or the long-term change detection memory 26e. In the process of S72 in Fig. 7, in addition to the leakage values ​​L1, L2 and the voltage V1, the leakage values ​​L3 and L4 are also stored in the cycle collection memory 26f.

[0141] Next, a main process executed by the CPU 61 of the control device 60 will be described with reference to Fig. 11. Fig. 11 is a flowchart of the main process of the control device 60. The main process of the control device 60 is executed when the power of the control device 60 of the vehicle 19 is turned on.

[0142] As shown in Fig. 11, the main process first obtains various operating state data and stores them in the operating state memory 62c (S81). The operating state data includes the control state of the load devices 15 to 17 (the driver's cab 66 and the traveling device 67), the current position of the vehicle 19 detected by the position detection device 68, the traveling speed of the vehicle 19 detected by the speed sensor 69, the temperature detected by the temperature sensor 70, the humidity detected by the humidity sensor 71, the time when these were detected, etc. Note that the operating state data is not limited to these data, and weather information and worker information obtained from an external device may also be used.

[0143] After the process of S81, the unreceived data stored in the peak detection memory 26c, the short-term change detection memory 26d, the long-term change detection memory 26e, and the cycle collection memory 26f of the earth leakage measuring instrument 50 are acquired from the earth leakage measuring instrument 50, and stored in the earth leakage data memory 62b (S82). Note that this unreceived data is the data transmitted by the earth leakage measuring instrument 50 in the process of S23 in FIG. 4.

[0144] After the process of S82, the latest leakage value L1 is obtained from the leakage meter 50 to determine whether it is necessary to turn on the forecast lamp 72 or the warning lamp 73 (S83). Next, judgment values ​​a and b for comparison with the leakage value L1 are set (S84). The judgment value a is set to 0.8 mA, for example. The judgment value b is set to a value larger than the judgment value a, for example, 1 mA. These judgment values ​​a and b may be changed as appropriate.

[0145] After the process of S84, the leakage current value L1 is compared with the judgment values ​​a and b (S85). If the leakage current value L1 is less than the judgment values ​​a and b (S85: less than a, b), the leakage current value L1 is sufficiently small and there is no need to turn on the forecast lamp 72 and the warning lamp 73, so other processes are executed (S88) and the processes from S81 onwards are repeated. The processes of S88 include various processes for operating the vehicle 19 and processes for changing the judgment values ​​a and b set in the process of S84.

[0146] In the process of S85, if the leakage current value L1 is equal to or greater than the judgment value a and less than the judgment value b (S85: equal to or greater than a and less than b), the leakage current value L1 is on the rise, so the warning lamp 72 is turned on (S86) and the process proceeds to S88. By turning on the warning lamp 72, the operator in the cab is advised to perform maintenance on the vehicle 19.

[0147] In the process of S85, if the leakage current value L1 is equal to or greater than the judgment values ​​a and b (S85: equal to or greater than a and b), there is a possibility that an abnormal leakage current is occurring in the vehicle 19, so the warning lamp 73 is turned on (S87) and the process proceeds to S88. By turning on the warning lamp 73, the operator in the cab is notified that maintenance of the vehicle 19 is required.

[0148] When the warning lamp 73 is turned on, for example, some of the functions of the vehicle 19 may be restricted, or the power supply to the vehicle 19 may be disabled. This makes it possible to prevent the vehicle 19 from breaking down and becoming unable to move due to leakage current while traveling or during work.

[0149] As described above, the leakage current monitoring device constituted by the control device 60 and the leakage current meter 50 can monitor the leakage current value L1 to notify an operator of the timing of maintenance of the vehicle 19 or of any abnormality in the vehicle 19, thereby enabling the safe operation of the vehicle 19. When performing maintenance on the vehicle 19, the leakage current values ​​L1 to L4 and the voltage V1 stored in the leakage current data memory 62b in association with each other can be analyzed by an external device or the like to facilitate the identification of the cause of the leakage current.

[0150] Furthermore, the leakage values ​​L1 to L4 and voltage V1 stored in the leakage data memory 62b and the operating state data stored in the operating state memory 62c are associated with each other by time. By analyzing each of these data using an external device, it becomes easier to identify the cause of the leakage current. For example, if the leakage value L1 becomes equal to or exceeds the judgment values ​​a and b only when the brakes are applied, it can be assumed that there is an abnormality in the electric circuit related to the brakes.

[0151] The operating state data also includes the temperature and humidity outside the vehicle 19. The insulation resistance values ​​of the various parts of the vehicle 19 vary depending on the temperature and humidity, and the leakage current values ​​L1 to L4, which depend on the insulation resistance values, also vary depending on the temperature and humidity. Therefore, by comparing the temperature and humidity with the leakage current values ​​L1 to L4, it is possible to estimate whether the variation in the leakage current values ​​L1 to L4 is due to the temperature and humidity or due to some other change.

[0152] Next, a third embodiment will be described with reference to Fig. 12. In the first embodiment, a leakage current meter 20 (leakage monitoring device) that monitors leakage current of a measurement object 10 equipped with a load device 14 that operates on DC power is described. In contrast, in the third embodiment, a leakage current meter 90 (leakage monitoring device) that monitors leakage current of a measurement object 80 equipped with a load device 85 that operates on AC power is 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.

[0153] 12 is a circuit diagram showing a schematic diagram of an electric circuit of a leakage current meter 90 as a leakage current monitoring device in the third embodiment and a measurement object 80. The measurement object 80 includes an AC power source 81 that outputs three-phase AC power (load power), a set of three power lines 82, 83, and 84 connected to the AC power source 81, and a load device 85 connected to the power lines 82 to 84.

[0154] The AC power supply 81 is a three-phase, four-wire generator that supplies three-phase AC power to power lines 82-84. A neutral line 81a extending from a neutral point of the AC power supply 81 is grounded. Single-phase AC currents with the same voltage but shifted in phase by 120° from the neutral line 81a flow through the power lines 82-84, respectively. Therefore, if no leakage current is occurring in the measurement object 80, the total current of the power lines 82-84 is basically approximately 0A.

[0155] The load device 85 is an electric circuit that operates by three-phase AC power supplied from the AC power source 81 via the power lines 82 to 84. Examples of the load device 85 include a three-phase motor and a converter. The load device 85 is housed in a housing 85a that is grounded via a ground wire 18. For example, if a leakage current occurs between the load device 85 and the housing 85a, the leakage current passes through the ground wire 18 and the neutral wire 81a, and the total current passing through the power lines 82 to 84 becomes unbalanced by the amount of the leakage current.

[0156] The earth leakage measuring instrument 90 is a device for monitoring this leakage current. The earth leakage measuring instrument 90 includes three individual current transformers 91, 92, and 93 through which each of the three power supply lines 82 to 84 passes, and a ground side current transformer 94 through which the ground wire 18 passes.

[0157] Each of the individual current transformers (individual measuring instruments) 91-93 and the ground side current transformer (ground side measuring instrument) 94 is a measuring instrument configured as a ring-shaped current transformer through which the electric wire to be measured passes, and measures the value of the current flowing through the pass-through part. The individual current transformers 91-93 and the ground side current transformer 94 in this embodiment are configured to be able to measure the value of an AC current, but since the configuration is known, a description thereof will be omitted.

[0158] As in the first and second embodiments, one set of the individual current transformers 91-93 constitutes one measurement unit capable of monitoring (calculating) a predetermined range of leakage current by summing up the currents that are the respective measurement results. Specifically, the measurement unit made up of the individual current transformers 91-93 can calculate the value of leakage current (leakage value L1) occurring downstream (on the load device 85 side) of itself. In contrast, the ground side current transformer 94 is a measurement unit that directly monitors (measures) the value of leakage current passing through the ground wire 18.

[0159] In this way, the leakage current measuring instrument 90 can easily analyze the cause of leakage current in the measurement object 80 by comparing the value of leakage current by the individual current transformers 91-93 with the value of leakage current by the ground side current transformer 94. For example, if the value of leakage current by the individual current transformers 91-93 and the value of leakage current by the ground side current transformer 94 are the same, it can be presumed that leakage current occurs mainly between the load device 85 and the housing 85a, and that the insulation resistance between them has deteriorated. Also, if the value of leakage current by the individual current transformers 91-93 and the value of leakage current by the ground side current transformer 94 are different, it can be presumed that leakage current occurs not only between the load device 85 and the housing 85a.

[0160] Next, a fourth embodiment will be described with reference to Fig. 13. In the first to third embodiments, the leakage current measuring instruments 20, 50, 90 (leakage monitoring devices) that calculate leakage current from the sum of currents flowing through a set of multiple power lines (a set of two positive and negative lines 12 and 13, or a set of three power lines 82-84) have been described. In contrast, in the fourth embodiment, a leakage current measuring instrument 100 (leakage monitoring device) that calculates leakage current by comparing the currents on the upstream and downstream sides of one power line 82 out of a set of power lines 82-84 will be described. Note that the same reference numerals are used for the same parts as in the first to third embodiments, and the following description will be omitted.

[0161] 13 is a circuit diagram showing a schematic diagram of an electric circuit of a leakage current measuring instrument 100 as a leakage current monitoring device in the fourth embodiment and an object to be measured 80. The leakage current measuring instrument 100 includes an upstream current transformer 101 through which one power line 82 passes, and a downstream current transformer 102 through which the downstream side of the upstream current transformer 101 of the power line 82 passes. Both the upstream current transformer (upstream measuring instrument) 101 and the downstream current transformer (downstream measuring instrument) 102 are measuring instruments constituted by annular current transformers through which the electric wire to be measured passes, and measure the value of the current flowing through the pass-through part.

[0162] The current measured by the upstream current transformer 101 is compared with the current measured by the downstream current transformer 102, and if there is no difference between them, it can be determined that no leakage current has occurred between the upstream current transformer 101 and the downstream current transformer 102. On the other hand, if there is a difference between the currents measured by the upstream current transformer 101 and the downstream current transformer 102, it can be determined that a leakage current has occurred between the upstream current transformer 101 and the downstream current transformer 102.

[0163] In this way, the earth leakage measuring instrument 100 can monitor the leakage current without measuring the current of each of the three power lines 82 to 84, so that the objects for which leakage current can be monitored can be expanded. In particular, the earth leakage measuring instrument 100 can monitor the leakage current occurring in one power line 82 without being affected by the leakage current occurring between the load device 85 and the housing 85a. As a result, for example, by combining the earth leakage measuring instrument 100 with the earth leakage measuring instrument 90 in the third embodiment, it becomes easier to analyze the cause of the leakage current occurring in the measurement object 80 by comparing the respective measurement results.

[0164] 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 output from the battery 11 or the AC power source 81 may be appropriately changed, the battery 11 may be changed to a DC power source such as a DC generator or a converter, and the AC power source 81 may be changed to an inverter or a transformer. Furthermore, the power line or electric wire in this specification is not limited to a flexible linear conductor, but may be a rod-shaped or plate-shaped conductor such as a bus bar (copper bar), or a combination of these conductors.

[0165] Also, the intervals for acquiring the currents A1, A2, etc. (intervals for executing the main process), the intervals for acquiring the operating state data, the intervals for calculating the average values ​​M1, M2, etc. of the leakage values ​​L1, L2, the ranges of the currents A1, A2 used to calculate the average values ​​M1, M2, the storage capacities of the ring buffers 27a to 27e, the ranges stored in the peak detection memory 26c when the leakage value L1, etc. exceeds a threshold value, etc. may be changed as appropriate. Also, the average value M1 before the change used to calculate the short-term change rate and the long-term change rate in the average detection process S21 of Fig. 6 may be changed as appropriate. Specifically, for example, the rate of change of the average value M1 for the most recent minute relative to the average value M1 from 5 to 4 minutes ago (the average value of the multiple leakage values ​​L1 calculated from 5 to 4 minutes ago) may be used as the short-term change rate and the long-term change rate.

[0166] Some of the configurations of the above embodiments may be combined with each other, or some of the configurations may be omitted. For example, the measurement unit using the zero-phase current transformer 23 in the first embodiment may be replaced with at least one of the measurement units using the individual current transformers 21, 22, and 51-56 in the second embodiment, or with the measurement unit using the individual current transformers 91-93 in the third embodiment. In addition, the measurement unit using the individual current transformers 21 and 22 in the first embodiment may be replaced with the measurement unit using the zero-phase current transformer 23, or the measurement unit using the zero-phase current transformer 23 in the first embodiment may be replaced with the measurement unit using the individual current transformers 21 and 22.

[0167] Furthermore, the measurement unit using the ground-side current transformer 94 in the third embodiment may be provided in the earth leakage measuring instruments 20, 50, 100 in the first, second, and fourth embodiments. One or more of the measurement units in each embodiment may be omitted, or the number of measurement units may be further increased. Furthermore, one set of power lines 82-84 in the third and fourth embodiments may be branched into multiple sets on the downstream side as in the second embodiment, and the measurement unit may be provided on at least one of the upstream and downstream sides of the branch.

[0168] In the above first, third and fourth embodiments, the earth leakage measuring instruments 20, 90 and 100 are earth leakage monitoring devices, and in the above second embodiment, an earth leakage monitoring device is configured by the earth leakage measuring instrument 50 and the control device 60. However, the present invention is not limited to this, and an earth leakage monitoring device may be configured by combining some or all of the earth leakage measuring instruments 20, 50, 90 and 100 in multiple combinations, and the earth leakage monitoring device may be configured by further combining the control device 60 and the external control device 40 with them.

[0169] In the above third embodiment, the leakage current of the measurement object 80 equipped with the AC power supply 81 that outputs three-phase AC power is monitored by the leakage current meter 90, but the present invention is not limited to this. The AC power supply 81 may be replaced with a power supply that outputs single-phase AC power. In this case, the power supply line 84 and the individual current transformer 93 may be omitted, and the sum of the currents measured by the two individual current transformers 91, 92 may be regarded as the value of the leakage current.

[0170] Furthermore, in a three-phase four-wire system, single-phase AC power may be supplied to a single-phase AC device from, for example, the power line 82 and the neutral line 81a. In this case, the value of the leakage current can be calculated by summing the currents of the individual current transformer 91 of the power line 82 and the individual current transformer through which the neutral line 81a passes. Also, the neutral line 81a may be omitted and the AC power supply 81 may be a three-phase three-wire power supply. In this case, it is preferable to ground any one of the power lines 82 to 84 upstream of the individual current transformers 91 to 93.

[0171] In the third and fourth embodiments, the earth leakage measuring instruments 90, 100 are described as not having the reference detection unit 24 that measures the voltage V1, but this is not limited to the above. For example, the earth leakage measuring instruments 90, 100 may be provided with a reference detection unit that detects voltage cross points between the phases of the power lines 82 to 84 through which three-phase AC flows, and the leakage current may be corrected based on the measurement results of the reference detection unit.

[0172] Specifically, in the leakage current measuring instrument 90, the leakage current Igr may be calculated as the corrected leakage current from the sum of the currents from the individual current transformers 91-93 and the cross point of the voltage from the reference detection unit. A known method may be used to calculate the leakage current Igr, for example, the method disclosed in Japanese Patent No. 4945727. The leakage current generated in the measurement object 80 through which AC flows includes the leakage current Igc caused by the capacitance to the ground and the leakage current Igr caused by the insulation resistance to the ground.

[0173] The reference detection unit 24 of the leakage current measuring instruments 20, 50 in the first and second embodiments may be omitted, and the sum of the currents A1, A2 may be used as the leakage current value L1 as is, for example. In addition, when the reference detection unit 24 is provided, it is not limited to being built into the leakage current measuring instruments 20, 50, but if a voltmeter for measuring the voltage of the battery 11 or the like is mounted on the measurement target 10 or the like, the voltmeter may be used as the reference detection unit 24.

[0174] In the above embodiment, the leakage current measuring instruments 20, 50, 90 sum up the currents A1, A2, etc. measured by the individual current transformers 21, 22, 51-56, 91-93 to calculate the leakage current values ​​L1-L4, but the present invention is not limited to this. For example, the leakage current values ​​L1-L4 may be calculated by the external control device 40 or the control device 60 instead of by the leakage current measuring instruments 20, 50, 90. That is, the leakage current measuring instruments 20, 50, 90 may be configured to transmit the measurement results of the individual current transformers 21, 22, 51-56, 91-93, the zero-phase current transformer 23, the ground side current transformer 94, and the reference detection unit 24 directly to the external control device 40 or the control device 60. The analysis using the leakage current values ​​L1-L4 and the voltage V1 may be performed by the leakage current measuring instruments 20, 50, 90 instead of the external control device 40, etc.

[0175] Also, the leakage data memory 62b and the operating state memory 62c may be provided in the leakage measuring instrument 50, and the processes of S81 to S87 in the main process of the control device 60 shown in Fig. 11 may be executed by the leakage measuring instrument 50. In this case, the leakage data memory 62b may be omitted, and the data capacities of the peak detection memory 26c, the short-term change detection memory 26d, the long-term change detection memory 26e, and the cycle collection memory 26f may be increased. Also, these memories 26c to 26f may be integrated into a single memory.

[0176] Moreover, each data in the leakage data memory 62b and the operating state memory 62c may be transmitted from the control device 60 of the vehicle 19, which is the measurement target, to an external control device provided outside the vehicle 19, and the processes of S83 to S87 may be executed by the external control device. In this case, instead of turning on the forecast lamp 72 and the alarm lamp 73, a message may be displayed on the display device of the external control device, requesting that maintenance of the vehicle 19 be performed.

[0177] Furthermore, in the first, third and fourth embodiments, operating status data like that of the second embodiment may be acquired by leakage current measuring instruments 20, 90, 100 or external control device 40, etc., and the operating status data may be used to analyze the cause of leakage current in the measurement object 10, 80.

[0178] In the above embodiment, the memories 26c to 26f storing data permitted to be transmitted to the external control device 40 store the leakage current values ​​L1 and L2 themselves as data related to the leakage current values ​​L1 and L2 (the sum of the currents A1 and A2, the total current A3), or store average values ​​M1 and M2 obtained by averaging a plurality of leakage current values ​​L1 and L2, respectively. However, the present invention is not limited to this. The currents A1 and A2 and the total current A3 may be stored in the memories 26c to 26f as data related to the leakage current values ​​L1 and L2, and the currents A1 and A2 and the total current A3 selected based on the leakage current values ​​L1 and L2 may be transmitted to the external control device 40.

[0179] In the above embodiment, the data permitted to be transmitted to the external control device 40 is temporarily stored in each of the memories 26c to 26f, but this is not limiting. The data permitted to be transmitted may be transmitted directly to the external control device 40 without being stored in each of the memories 26c to 26f. This can be done when the earth leakage measuring instrument 20 and the external control device 40 are capable of communicating with each other, and when communication between them is not possible, temporary storage in each of the memories 26c to 26f is necessary.

[0180] In the above embodiment, the currents A1, A2, etc. measured by the individual current transformers 21, 22 are digitized and acquired by the CPU 25 of the earth leakage measuring instrument 20, but this is not limited thereto. For example, the measured currents A1, A2 may be summed as analog signals, and the sum may be digitized and acquired by the CPU 25. When the measurement results of the individual current transformers 21, 22, 51-56, 91-93, the zero-phase current transformer 23, the ground side current transformer 94, and the reference detection unit 24 are digitized, the digitizing converters and the input / output port 29 may communicate wirelessly.

[0181] In the above embodiment, the case where the earth leakage measuring instrument 20 executes the peak detection process S20, the average detection process S21, and the cycle collection process S22 has been described, but this is not limited to the above. For example, at least one of the peak detection process S20, the average detection process S21, and the cycle collection process S22 may be executed, and the other processes may not be executed.

[0182] In the above embodiment, the case where the leakage current value L1 from the start position S to the end position E is stored in the peak detection memory 26c in the peak detection process S20 has been described, but this is not limited to the above. For example, when the leakage current value L1 at the latest position of the upstream ring buffer 27a changes from less than the threshold value to equal to or greater than the threshold value, the leakage current value L1 from 15 seconds before to the latest position may be stored in the peak detection memory 26c, and a newly calculated leakage current value L1 at the latest position may be stored in the peak detection memory 26c in each peak detection process S20 until 15 seconds have passed since the leakage current value L1 changed from equal to or greater than the threshold value to less than the threshold value.

[0183] In the above embodiment, the leakage value L2 is stored in the peak detection memory 26c together with the leakage value L1 in the processes of S48 and S51 of the peak detection process S20, but this is not limited thereto. The leakage value L2 may not be stored in the processes of S48 and S51. In this case, the peak detection process for the leakage value L2 is executed separately from the peak detection process S20 for the leakage value L1. In the peak detection process for the leakage value L2, the leakage value L1 in each process of S41 to S51 may be replaced with the leakage value L2, and the upstream ring buffer 27a may be replaced with the downstream ring buffer 27b. The same is true for the average detection process S21, and in the average detection process S21 for the leakage value L2, the average value M1 in each process of S64 to S69 may be replaced with the average value M2.

[0184] In the above-described first embodiment, a leakage current detection method has been described that includes an individual measurement step (processing of S11, S12) for measuring currents A1, A2 individually by individual current transformers 21, 22, a summing step (part of processing of S16) for summing the multiple currents A1, A2 measured in the individual measurement step, and a detection step (e.g., part of processing of S16) for detecting leakage current L1 of measurement object 10 based on the current "A1+A2" summed in the summing step. This method is similar to the above-described second and third embodiments, as described above.

[0185] In the individual measurement step, for example, individual current transformer 22 may be omitted, and after measuring current A1 of positive wire 12 with individual current transformer 21, negative wire 13 may be passed through individual current transformer 21 removed from positive wire 12, and current A2 of negative wire 13 may be measured with individual current transformer 21. Similarly, individual current transformer 21 may be omitted, and currents A1 and A2 may be measured individually with individual current transformer 22. Furthermore, each of the measurement points by individual current transformers 51 to 56 and 91 to 93 may be measured in sequence with one individual current transformer. In addition, in the detection step, for example, the sum of currents "A1+A2" may be detected as leakage current L1 as it is.

[0186] In contrast to the leakage current detection methods of the first to third embodiments, the above fourth embodiment has described a leakage current detection method that includes a measurement step in which the upstream current transformer 101 and the downstream current transformer 102 individually measure the currents flowing at two points on the power line 82, a difference step in which the difference between the currents measured at the two points in the measurement step is calculated, and a detection step in which the leakage current of the measurement object 80 is detected based on the current difference calculated in the difference step.

[0187] In this measurement step, for example, the downstream current transformer 102 may be omitted, and after the upstream current transformer 101 measures the current on the upstream side of the power line 82, the moved upstream current transformer 101 may measure the current on the downstream side of the power line 82. Similarly, the upstream current transformer 101 may be omitted, and the downstream current transformer 102 may measure the currents at two points of the power line 82 individually. In addition, in the detection step in the above fourth embodiment, the current difference calculated in the difference step is detected as the leakage current as it is, but the current difference may be corrected by the voltage of the power line 82 or the like to detect the leakage current value.

[0188] In the above embodiment, the individual current transformers 21, 22, 51-56, 91-93, the zero-phase current transformer 23, the ground side current transformer 94, the upstream current transformer 101, and the downstream current transformer 102 are each configured as an annular current transformer through which the electric wire to be measured passes, and are measuring instruments that measure the value of the current flowing through the passing part. However, these current transformers may be replaced with other measuring instruments that can measure the value of the current flowing through the electric wire to be measured. An example of the other measuring instruments is a non-annular one that measures the magnetic field generated in the electric wire by the passage of current and measures the value of the current based on the magnetic field. Also, an example of the other measuring instruments is limited to those that individually measure the current of one electric wire, and is one that uses a shunt resistor. [Explanation of symbols]

[0189] 10,80 Measurement object 12 Positive wire (power wire) 12a,13a Main power line 12b~12d, 13b~13d Branch wires 13 Negative wire (power wire) 14~17,85 Load equipment 14a~17a,85a case 18 Ground wire 19 Vehicle (measurement object) 20,90,100 Earth leakage measuring instrument (earth leakage monitoring device) 21, 22, 51-56, 91-93 Individual current transformers (measuring section, individual measuring instruments) 23 Zero-phase current transformer (measurement section, zero-phase measuring instrument) 24 Reference detection section 26c Peak detection memory (storage section) 26d Short-term change detection memory (storage section) 26e Long-term change detection memory (storage section) 50 Earth leakage measuring instrument (part of earth leakage monitoring device) 60 Control device (part of leakage current monitoring device) 82~84 Power line 94 Earth side current transformer (measurement section, earth side measuring instrument) 101 Upstream current transformer (upstream measuring instrument) 102 Downstream current transformer (downstream measuring instrument) S16, S18: Criterion correlation means, total calculation means S41~S47,S50,S64,S65,S67,S68 Memory judgment means S48, S51, S66, S69 Memory execution means S81 Acquisition method S82 State association means

Claims

1. A leakage current monitoring device for monitoring a leakage current of a measurement object including a set of multiple power lines that supplies load power from upstream to downstream and a load device that operates by the load power supplied from the set of power lines, one or more measuring units capable of monitoring leakage current occurring within a predetermined range of the measurement object; One of the measuring sections is formed by a set of multiple individual measuring devices that individually measure the current flowing through each of the set of multiple power lines.

2. a reference detection unit that measures a voltage occurring between a pair of the power lines at a measurement position of the pair of the individual measuring devices; a reference correlation means for correlating the voltage measured by the reference detection unit with the current measured by the individual measuring device at the time of the measurement; 2. The earth leakage monitoring device according to claim 1, further comprising:

3. An acquisition means for acquiring an operation state of the load device; a state relating means for relating the operating state obtained by the obtaining means to a current measured by the individual measuring device at the time of obtaining the operating state; 2. The earth leakage monitoring device according to claim 1, further comprising:

4. A memory unit capable of storing data relating to a total of currents measured by a set of the individual measuring devices; A total calculation means for calculating a total of the currents; a storage determination means for determining whether or not to store data relating to the total calculated by the total calculation means in the storage unit; a storage execution means for storing the data in the storage unit when the storage determination means determines that the data should be stored; 2. The earth leakage monitoring device according to claim 1, further comprising:

5. The leakage current monitoring device according to claim 1, characterized in that two or more measuring units are provided at a distance from each other on the upstream and downstream sides of a pair of the power supply lines, and each measuring unit monitors the leakage current generated in the measurement object downstream of the position at which it is located.

6. The leakage current monitoring device according to claim 5, characterized in that one of the measuring units is formed by a zero-phase measuring instrument that collectively measures the magnetic fields generated in each of a set of the power lines when a current is passed through them, and measures the sum of the currents flowing through those power lines based on the magnetic fields.

7. The set of power lines includes: One upstream pair of main conductors; and a plurality of sets of branch electric wires each branching off from the one set of trunk electric wires, The load device is provided in plurality and connected to each of the sets of branch electric wires, The leakage current monitoring device according to claim 5 or 6, characterized in that the measuring unit is arranged in one set of the main electric wire upstream of a plurality of sets of the branch electric wires, and another measuring unit is arranged in one set of the branch electric wires.

8. the measurement target comprises a housing in which the load device is housed and a ground wire that grounds the housing, The measuring unit is provided in two or more units, 2. The earth leakage monitoring device according to claim 1, wherein one of said measuring sections is formed by a ground side measuring instrument for measuring a current flowing through said ground wire.

9. A leakage current monitoring device for monitoring a leakage current of a measurement object including a set of multiple power lines that supplies load power from upstream to downstream and a load device that operates by the load power supplied from the set of power lines, an upstream measuring device that measures a current flowing through one of the power lines; A leakage current monitoring device characterized by comprising: a downstream meter that measures the current flowing through the power line downstream of the measurement position of the upstream meter on the power line whose current is measured by the upstream meter.

10. A leakage current detection method for detecting a leakage current of a measurement object having a set of multiple power lines that supplies load power from upstream to downstream and a load device that operates by the load power supplied from the set of power lines, comprising: an individual measuring step of measuring a current flowing through each of the set of a plurality of power lines by a measuring instrument; a summing step of summing the multiple currents individually measured in the individual measurement steps; a detection step of detecting a leakage current of the measurement object based on the current summed in the summing step; A leakage current detection method comprising:

11. A leakage current detection method for detecting a leakage current of a measurement object having a set of multiple power lines that supplies load power from upstream to downstream and a load device that operates by the load power supplied from the set of power lines, comprising: a measuring step of measuring currents flowing through two different points of one power line by a measuring instrument; A difference step for calculating the difference between the two currents measured in the measurement step; a detection step of detecting a leakage current of the measurement object based on the difference in the current calculated in the difference step; A leakage current detection method comprising:

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