Inspection equipment and methods.

Abstract

The present invention comprises: a leakage current detection unit 11 for detecting a leakage current flowing to a star-connected electric line to be measured; a voltage detection unit 12 for detecting a voltage applied to the electric line to be measured; a phase angle detection unit 13 for detecting a phase angle on the basis of the leakage current detected by the leakage current detection unit 11 and the voltage detected by the voltage detection unit 12; a determination unit 14 for determining whether the phase angle detected by the phase angle detection unit 13 belongs to any of a first angle range, a second angle range, or a third angle range; and a calculation unit 15 for calculating a resistance component leakage current caused by ground insulation resistance that is included in the leakage current flowing to the electric line to be measured, on the basis of the angle range to which the phase angle belongs, the phase angle detected by the phase angle detection unit 13, and the leakage current detected by the leakage current detection unit 11.

Description

Inspection device, inspection method, and inspection program

[0001] The present disclosure relates to an inspection device, an inspection method, and an inspection program for inspecting or monitoring the insulation resistance value and leakage current value of a three-phase star power circuit.

[0002] The insulation performance of electrical systems, including load equipment of electrical facilities, is extremely important for preventing electric shock, fire, etc. However, the insulation performance can be impaired due to aging deterioration of electrical facilities or construction work, etc., and leakage current (hereinafter referred to as "Io") can occur in electric lines. It is important to predict the occurrence of Io or detect Io that is actually occurring, and prevent accidents before they occur, or at an early stage.

[0003] For this reason, a test device is provided on the ground wire of the secondary circuit of the power receiving transformer to test Io, which includes a leakage current due to capacitance to earth (hereinafter referred to as "Ioc") and a leakage current due to insulation resistance to earth (hereinafter referred to as "Ior"), which is directly related to insulation resistance.

[0004] For example, Patent Document 1 discloses a leakage current measuring device that measures the leakage current Ior of the insulation resistance of any two distribution lines in a three-phase, three-wire distribution line configured with a star connection, and that includes a voltage detection unit that detects the phase-to-phase voltage between the two distribution lines, a current detection unit that detects a composite current of the currents flowing through the two distribution lines, and a processing unit that calculates the phase angle θ between the phase-to-phase voltage and the composite current, as well as the current value Io of the composite current, and measures the leakage current Ior based on the following formula: Ior = |2 × Io × sin θ|

[0005] JP 2011-27449 A

[0006] Here, when deterioration of the insulation resistance occurs in any two distribution lines in a three-phase three-wire distribution line, Ior is expressed as the scalar sum of the two phases, but unless it is known to what extent Ior occurs in the two phases, it is difficult to identify the problem area of ​​Ior (the location where Ior is occurring), the cause of occurrence, changes during periodic inspections, etc.

[0007] The present disclosure aims to provide an inspection device, an inspection method, and an inspection program that can accurately calculate Ior occurring in each phase when Ior occurs in one or both of two phases, and can inspect or monitor a star-connected electric line under test.

[0008] In order to achieve the above object, the present disclosure is configured as follows: (1) A leakage current detector that detects a leakage current flowing in a measured electric line in which a first phase, a second phase, and a third phase are star-connected, or in which a first phase, a second phase, a third phase, and a neutral are star-connected, a voltage detector that detects a voltage applied to the measured electric line, a phase angle detector that detects a phase angle based on the leakage current detected by the leakage current detector and the voltage detected by the voltage detector, and a phase angle detector that detects a phase angle between the first phase and the second phase. a determination unit that determines whether the phase angle belongs to a first angle range defined by the phase angle detection unit, a second angle range defined by the phase angle detection unit, or a third angle range defined by the phase angle detection unit, and a calculation unit that calculates a resistance component leakage current caused by ground insulation resistance, which is included in the leakage current flowing through the electric line under test, based on the angle range to which the phase angle belongs, the phase angle detected by the phase angle detection unit, and the leakage current detected by the leakage current detection unit. (2) The inspection device according to (1), wherein the calculation unit calculates a composite value of the resistive component leakage currents flowing in the first phase and the second phase and each resistive component leakage current flowing in each of the phases when the angle range to which the phase angle belongs is the first angle range, calculates a composite value of the resistive component leakage currents flowing in the second phase and the third phase and each resistive component leakage current flowing in each of the phases when the angle range to which the phase angle belongs is the second angle range, and calculates a composite value of the resistive component leakage currents flowing in the first phase and the third phase and each resistive component leakage current flowing in each of the phases when the angle range to which the phase angle belongs is the third angle range. (3) The inspection device according to (1) or (2), wherein, with respect to the voltage of the first phase as a reference, the first angle range is a 120° angle range between the first phase and the second phase, the second angle range is a 120° angle range between the second phase and the third phase, and the third angle range is a 120° angle range between the third phase and the first phase.(4) The voltage detection unit detects the line voltage of any two of three ungrounded wires, detects the voltage between any two of the grounded wires or neutral wires, detects the voltage between any one of the three ungrounded wires and the grounded wire or neutral wire, or detects the voltage between all of the three ungrounded wires and the grounded wire or neutral wire, or between all of the wires including the grounded wire and the neutral wire. (5) The inspection device according to any one of (1) to (3), further comprising: a leakage current detection step of detecting a leakage current flowing in a measured electric line in which a first phase, a second phase, and a third phase are star-connected, or in which a first phase, a second phase, a third phase, and a neutral wire are star-connected; a voltage detection step of detecting a voltage applied to the measured electric line; a phase angle detection step of detecting a phase angle based on the leakage current detected in the leakage current detection step and the voltage detected in the voltage detection step; an inspection method comprising: a determination step of determining whether the phase angle belongs to a first angle range, a second angle range that is an angle range between the second phase and the third phase, or a third angle range that is an angle range between the third phase and the first phase; and a calculation step of calculating a resistance component leakage current caused by ground insulation resistance, which is included in the leakage current flowing through the electric line under test, based on the angle range to which the phase angle belongs, the phase angle detected in the phase angle detection step, and the leakage current detected in the leakage current detection step.(6) A computer includes a leakage current detection step for detecting a leakage current flowing in a test electric line in which a first phase, a second phase, and a third phase are star-connected, or a first phase, a second phase, a third phase, and a neutral wire are star-connected; a voltage detection step for detecting a voltage applied to the test electric line; a phase angle detection step for detecting a phase angle based on the leakage current detected by the leakage current detection step and the voltage detected by the voltage detection step; and a detection step for detecting a phase angle based on the leakage current detected by the leakage current detection step and the voltage detected by the voltage detection step. a determination step of determining whether the phase angle belongs to a first angle range defined by the phase angle detection step, a second angle range defined by the phase angle between the second and third phases, or a third angle range defined by the phase angle between the third and first phases; and a calculation step of calculating a resistance component leakage current caused by ground insulation resistance, which is included in the leakage current flowing through the electric line under test, based on the angle range to which the phase angle belongs, the phase angle detected by the phase angle detection step, and the leakage current detected by the leakage current detection step.

[0009] According to the present disclosure, when Ior occurs in one or both of two phases, it is possible to accurately calculate the Ior occurring in each phase and inspect or monitor the star-connected electric line under test.

[0010] FIG. 1 is a diagram showing the configuration of an inspection device. FIG. 2 is a diagram showing a schematic diagram of an angle range. FIG. 3 is a diagram explaining the vector representation of a leakage current due to capacitance to the ground and a leakage current due to insulation resistance to the ground. FIG. 4 is a diagram showing a schematic diagram of the scalar sum of Ior(r) and Ior(t). FIG. 5 is a diagram showing a case where the phase angle belongs to a first angle range R1. FIG. 6 is a diagram showing a case where the phase angle belongs to a second angle range R2. FIG. 7 is a diagram showing a case where the phase angle belongs to a third angle range R3. FIG. 8 is a flowchart showing the procedure of an inspection method. FIG. 9 is a block diagram showing a first configuration example of a computer. FIG. 10 is a block diagram showing a second configuration example of a computer.

[0011] The present embodiment will be described below. Note that the present embodiment described below does not unduly limit the content of the present disclosure described in the claims. Furthermore, not all of the configurations described in the present embodiment are necessarily essential components of the present disclosure.

[0012] 1 is a diagram showing the configuration of an inspection device 1. The inspection device 1 includes a leakage current detection unit 11, a voltage detection unit 12, a phase angle (phase) detection unit 13, a determination unit 14, and a calculation unit 15.

[0013] The leakage current detector 11 detects leakage current flowing in a test electric line in which the first, second, and third phases are star-connected. Hereinafter, the first phase will be referred to as the R phase, the second phase as the T phase, and the third phase as the S phase, but the names are not limited to these. Hereinafter, the leakage current measured by the leakage current detector 11 will be referred to as "Io," but the names are not limited to these.

[0014] Furthermore, the inspection device 1 will be described as inspecting or monitoring a three-phase, four-wire electric line under test in which three phases (R phase, S phase, T phase) are star-connected and a neutral point is drawn out. However, the invention is not limited to this configuration, and the inspection device 1 may also inspect or monitor a three-phase, three-wire electric line under test in which three phases (R phase, S phase, T phase) are star-connected and no neutral wire is drawn out.

[0015] A zero-phase-sequence current transformer (ZCT) 10 is connected to the leakage current detection unit 11. The zero-phase-sequence current transformer 10 is configured to clamp the entire electric line. For example, the zero-phase-sequence current transformer 10 may be a handy split-type zero-phase-sequence current transformer, which can be easily installed on the electric line by a worker on-site. The zero-phase-sequence current transformer 10 may also be configured to clamp the Class B ground wire, as shown by the dotted line in FIG. 1.

[0016] The leakage current detector 11 detects (calculates) the leakage current (Io) flowing through the electric line under test from the signal measured by the zero-phase-sequence current transformer 10 .

[0017] The voltage detection unit 12 detects the voltage applied to the electric line under test. The electric line under test can have a variety of configurations, and multiple configurations are possible for the voltage detection unit 12 to detect the voltage. For example, the following configurations are possible for the voltage detection unit 12 to detect the voltage. In the present disclosure, an appropriate configuration is adopted as appropriate depending on the configuration of the electric line under test that is actually being inspected or monitored. Note that the configurations for detecting the voltage by the voltage detection unit 12 are not limited to the following. Configuration 1: A configuration for detecting the line-to-line voltage of any two of the three ungrounded lines. Configuration 2: A configuration for detecting the voltage between any two-phase grounded or neutral line. Configuration 3: A configuration for detecting the voltage between any one of the three ungrounded lines and the grounded or neutral line. Configuration 4: A configuration for detecting the voltage between all three ungrounded lines and the grounded line (type D grounded line), or between the neutral line or the grounded line (type D grounded line) and all lines including the neutral line.

[0018] The phase angle detection unit 13 detects a phase angle (θ) based on the leakage current (Io) detected by the leakage current detection unit 11 and the voltage detected by the voltage detection unit 12. Specifically, the phase angle detection unit 13 detects the waveform of the leakage current (Io) detected by the leakage current detection unit 11 and the voltage (for example, the line voltage (V) between the R phase and the T phase) detected by the voltage detection unit 12. Ｔ－Ｒ ) is used as a reference voltage) to calculate and process the waveform of the reference voltage (V Ｔ－Ｒ ) and the zero crossing point of the leakage current (Io), the reference voltage (V Ｔ－Ｒ The phase angle (θ) between the leakage current (Io) and the voltage drop (Vp) is detected. The calculation process for calculating the phase angle may be performed using synchronous detection or DFT (Discrete Fourier Transform).

[0019] The determination unit 14 determines to which angle range the phase angle detected by the phase angle detection unit 13 belongs: a first angle range R1 which is the angle range between the R phase and the T phase, a second angle range R2 which is the angle range between the T phase and the S phase, or a third angle range R3 which is the angle range between the S phase and the R phase.

[0020] FIG. 2 is a diagram showing a schematic diagram of the angle ranges. Here, when the R-phase voltage is used as a reference, the angle range of 120° between the R-phase and the T-phase is the first angle range R1, the angle range of 120° between the T-phase and the S-phase is the second angle range R2, and the angle range of 120° between the S-phase and the R-phase is the third angle range R3. Specifically, the line voltage (V Ｔ－Ｒ ) is used as a reference voltage, and when this voltage is set to 0 degrees, if the current flowing through the R phase occurs at a position of 30 degrees, the first angle range R1 is "30°≦θ<150°," the second angle range R2 is "150°≦θ<270°," and the third angle range R3 is "270°≦θ<30°." Furthermore, generalizing the angle ranges, if the R phase voltage occurs at a position of X degrees, the first angle range R1 is "X°≦θ<(X°+120°)," the second angle range R2 is "(X°+120°)≦θ<(X°+240°)," and the third angle range R3 is "(X°+240°)≦θ<X°."

[0021] The calculation unit 15 calculates the resistance component leakage current caused by the ground insulation resistance contained in the leakage current flowing through the measured electric line based on the angle range to which the phase angle belongs, the phase angle detected by the phase angle detection unit 13, and the leakage current detected by the leakage current detection unit 11.

[0022] Specifically, when the angle range to which the phase angle detected by the phase angle detection unit 13 belongs is a first angle range R1, the calculation unit 15 calculates a composite value of the resistive component leakage currents flowing in the R phase and the T phase, and each resistive component leakage current flowing in each phase. When the angle range to which the phase angle detected by the phase angle detection unit 13 belongs is a second angle range R2, the calculation unit 15 calculates a composite value of the resistive component leakage currents flowing in the T phase and the S phase, and each resistive component leakage current flowing in each phase. When the angle range to which the phase angle detected by the phase angle detection unit 13 belongs is a third angle range R3, the calculation unit 15 calculates a composite value of the resistive component leakage currents flowing in the S phase and the R phase, and each resistive component leakage current flowing in each phase.

[0023] In this way, the inspection device 1 calculates the composite value of Ior flowing in each phase and the individual Ior flowing in each phase based on the angle range to which the phase angle (phase difference) detected by the phase angle detection unit 13 belongs.Therefore, when Ior occurs in one or both of the two phases, the Ior occurring in each phase can be accurately calculated, and the star-connected electric line under test can be inspected or monitored.

[0024] (Regarding Vector Representation of Io, Ioc, and Ior) Here, the vector representation of the leakage current (Io) due to capacitance to earth (hereinafter sometimes referred to as "Ioc") and the leakage current (Ior) due to insulation resistance to earth, which is directly related to insulation resistance, will be explained using Fig. 3. Fig. 3 is a diagram that schematically shows the state when Ior and Ioc of each phase are expressed as vectors.

[0025] When the reference voltage is set to 0 degrees and the resistive component leakage current (hereinafter sometimes referred to as "Ior(r)") flowing through the R phase is expressed as a vector and occurs at 30 degrees, the resistive component leakage current (hereinafter sometimes referred to as "Ior(t)") flowing through the T phase occurs at 150 degrees, and the resistive component leakage current (hereinafter sometimes referred to as "Ior(s)") flowing through the S phase occurs at 270 degrees. Note that hereinafter, the vector Ior(r) will be simply referred to as Ior(r), the vector Ior(t) will be simply referred to as Ior(t), and the vector Ior(s) will be simply referred to as Ior(s). In this embodiment, the line voltage between the R phase and the T phase is used as the reference voltage, and this voltage is set to 0 degrees.

[0026] Furthermore, the capacitive leakage current flowing through the R phase (hereinafter sometimes referred to as "Ioc(r)") occurs at 120 degrees, which is 90 degrees (π / 2) ahead of Ior(r). The capacitive leakage current flowing through the T phase (hereinafter sometimes referred to as "Ioc(t)") occurs at 240 degrees, which is 90 degrees (π / 2) ahead of Ior(t). The capacitive leakage current flowing through the S phase (hereinafter sometimes referred to as "Ioc(s)") occurs at 0 degrees (360 degrees), which is 90 degrees (π / 2) ahead of Ior(s).

[0027] In the following, the vector Ioc(r) will be simply referred to as Ioc(r), the vector Ioc(t) will be simply referred to as Ioc(t), and the vector Ioc(s) will be simply referred to as Ioc(s).

[0028] When Ioc(r), Ioc(s), and Ioc(t) are in balance, the vector Ioc obtained by combining Ioc(r), Ioc(s), and Ioc(t) does not occur because each component cancels out.

[0029] Next, the synthesis (scalar sum) of Ior generated in two phases (for example, R phase and T phase) will be described.

[0030] Ior is calculated by substituting the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (1): Ior=Io×sin θ / cos 60° (1)

[0031] Ior calculated by equation (1) is the scalar sum (Ior(r)+Ior(t)).

[0032] 4 is a diagram schematically showing the scalar sum of Ior(r) and Ior(t). In FIG. 4, Ioc(r), Ioc(t), and Ioc(s) are assumed to be in a balanced state and not to cancel each other out. In FIG. 4, Ior(t) is moved to the R-phase axis (Ior(t) after the movement is shown as Ior(t)') and is shown as the composite sum with Ior(r) (scalar sum: Ior(r) + Ior(t)').

[0033] Furthermore, since Ior calculated by equation (1) is a composite (scalar sum) of two phases, it is not possible to know, as it is, whether the leakage current caused by the earth insulation resistance is occurring only in the R phase, only in the T phase, or in both the R and T phases. Therefore, the inspection device 1 calculates the composite value of Ior flowing in each phase and each Ior flowing in each phase based on the angle range to which the phase angle (phase) detected by the phase angle detection unit 13 belongs.

[0034] (When the phase angle falls within the first angle range R1) Fig. 5 is a diagram schematically illustrating a case where the phase angle falls within the first angle range R1. When the phase angle falls within the first angle range R1, the calculation unit 15 substitutes the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (2) to calculate a combined (scalar sum: Ior(rt)) of Ior generated in two phases (R phase and T phase): Ior(rt) = Io × sin θ / cos 60° (2)

[0035] The calculation unit 15 also substitutes the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (3) to calculate Ior(r) generated in the R phase: Ior(r)=Io×sin(150°−θ) / cos30° (3)

[0036] The calculation unit 15 also substitutes Ior(rt) calculated by equation (2) and Ior(r) calculated by equation (3) into equation (4) to calculate Ior(t) generated in the T phase: Ior(t)=Ior(rt)−Ior(r) (4)

[0037] For example, when Ior(t) is "0", "Ior(rt) = Ior(r)", and it is clear that the leakage current due to earth insulation resistance flows only in the R phase. Also, when Ior(r) is "0", "Ior(rt) = Ior(t)", and it is clear that the leakage current due to earth insulation resistance flows only in the T phase. When Ior(t) and Ior(r) are other than "0", it is clear that the leakage current due to earth insulation resistance flows in both the R phase and the T phase, and by using equations (3) and (4), it is possible to quantitatively calculate how much leakage current due to earth insulation resistance flows in the R phase and the T phase.

[0038] (When the phase angle falls within the second angle range R2) Fig. 6 is a diagram schematically illustrating a case where the phase angle falls within the second angle range R2. In Fig. 6, Ior(s) is moved to the T-phase axis (the moved Ior(s) is shown as Ior(s)') and is shown as a composite sum with Ior(t) (scalar sum: Ior(t) + Ior(s)').

[0039] When the phase angle falls within the second angle range R2, the calculation unit 15 substitutes the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (5) to calculate the combined (scalar sum: Ior(ts)) of Ior generated in two phases (T phase and S phase): Ior(ts)=Io×sin(θ−120°) / cos 60° (5)

[0040] The calculation unit 15 also substitutes the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (6) to calculate Ior(t) generated in the T phase: Ior(t)=Io×sin(270°−θ) / cos30° (6)

[0041] The calculation unit 15 also substitutes Ior(ts) calculated by equation (5) and Ior(t) calculated by equation (6) into equation (7) to calculate Ior(s) generated in the S phase: Ior(s)=Ior(ts)−Ior(t) (7)

[0042] For example, when Ior(s) is "0", Ior(ts) = Ior(t), which means that the leakage current due to ground insulation resistance flows only in the T phase. Also, when Ior(t) is "0", Ior(ts) = Ior(s), which means that the leakage current due to ground insulation resistance flows only in the S phase. When Ior(s) and Ior(t) are other than "0", it is clear that the leakage current due to ground insulation resistance flows in both the S phase and the T phase, and by using equations (6) and (7), it is possible to quantitatively calculate how much leakage current due to ground insulation resistance flows in the T phase and the S phase.

[0043] (When the phase angle falls within the third angle range R3) Fig. 7 is a diagram schematically illustrating a case where the phase angle falls within the third angle range R3. In Fig. 7, Ior(r) is moved to the S-phase axis (the moved Ior(r) is shown as Ior(r)') and is shown as a composite sum with Ior(s) (scalar sum: Ior(s) + Ior(r)').

[0044] When the phase angle falls within the third angle range R3, the calculation unit 15 substitutes the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (8) to calculate the combined (scalar sum: Io(sr)) of Io generated in two phases (S phase and R phase): Io(sr)=Io×sin(θ−240°) / cos 60° (8)

[0045] The calculation unit 15 also substitutes the phase angle θ detected by the phase angle detection unit 13 and the leakage current Io detected by the leakage current detection unit 11 into equation (9) to calculate Ior(s) generated in the S phase: Ior(s)=Io×sin(30°−θ) / cos30° (9)

[0046] The calculation unit 15 also substitutes Ior(sr) calculated by equation (8) and Ior(s) calculated by equation (9) into equation (10) to calculate Ior(r) occurring in the R phase. Ior(r)=Ior(sr)−Ior(s) (10)

[0047] For example, when Ior(r) is "0", "Ior(sr) = Ior(s)" holds, and it is clear that the leakage current due to ground insulation resistance flows only in the S phase. Also, when Ior(s) is "0", "Ior(sr) = Ior(r)" holds, and it is clear that the leakage current due to ground insulation resistance flows only in the R phase. When Ior(r) and Ior(s) are other than "0", it is clear that the leakage current due to ground insulation resistance flows in both the S phase and the R phase, and by using equations (9) and (10), it is possible to quantitatively calculate how much leakage current due to ground insulation resistance flows in the S phase and the R phase.

[0048] In this way, when the phase angle range falls within the first angle range R1, the inspection device 1 can accurately calculate the Ior occurring in the R phase and the T phase using equations (2), (3), and (4). When the phase angle range falls within the second angle range R2, the inspection device 1 can accurately calculate the Ior occurring in the T phase and the S phase using equations (5), (6), and (7). When the phase angle range falls within the third angle range R3, the inspection device 1 can accurately calculate the Ior occurring in the S phase and the R phase using equations (8), (9), and (10). The calculated Ior can be used to inspect or monitor the star-connected electric line under test.

[0049] (Inspection Method) Here, a description will be given of an inspection method using the inspection device 1. Fig. 8 is a flowchart illustrating the procedure of the inspection method.

[0050] In step ST1, the leakage current detection unit 11 detects a leakage current flowing in a test electric line in which R-phase, S-phase, and T-phase are star-connected (leakage current detection step).

[0051] In step ST2, the voltage detection unit 12 detects the voltage applied to the electric line under test (voltage detection step).

[0052] In step ST3, the phase angle detection unit 13 detects a phase angle based on the leakage current detected in the leakage current detection step and the voltage detected in the voltage detection step (phase angle detection step).

[0053] In step ST4, the determination unit 14 determines whether the phase angle detected in the phase angle detection step belongs to a first angle range R1, which is the angle range between the first and second phases, a second angle range R2, which is the angle range between the second and third phases, or a third angle range R3, which is the angle range between the third and first phases (determination step). If the phase angle is in the first angle range R1, the process proceeds to step ST5. If the phase angle is in the second angle range R2, the process proceeds to step ST6. If the phase angle is in the third angle range R3, the process proceeds to step ST7.

[0054] In step ST5, the calculation unit 15 calculates a resistance component leakage current due to the ground insulation resistance included in the leakage current flowing through the electric line under test, based on the phase angle detected in the phase angle detection step and the leakage current detected in the leakage current detection step (calculation step). Specifically, the calculation unit 15 calculates Ior (scalar sum: Ior(rt)) obtained by combining Ior generated in two phases (R phase and T phase) using the above-mentioned equation (2), calculates Ior(r) generated in the R phase using the above-mentioned equation (3), and calculates Ior(t) generated in the T phase using the above-mentioned equation (4).

[0055] In step ST6, the calculation unit 15 calculates a resistance component leakage current due to the ground insulation resistance included in the leakage current flowing through the electric line under test, based on the phase angle detected in the phase angle detection step and the leakage current detected in the leakage current detection step (calculation step). Specifically, the calculation unit 15 calculates Ior (scalar sum: Ior(ts)) by combining Ior generated in two phases (T phase and S phase) using the above-mentioned equation (5), calculates Ior(t) generated in the T phase using the above-mentioned equation (6), and calculates Ior(s) generated in the S phase using the above-mentioned equation (7).

[0056] In step ST7, the calculation unit 15 calculates a resistance component leakage current due to the ground insulation resistance included in the leakage current flowing through the electric line under test, based on the phase angle detected in the phase angle detection step and the leakage current detected in the leakage current detection step (calculation step). Specifically, the calculation unit 15 calculates Ior (scalar sum: Ior(sr)) by combining Ior generated in two phases (S phase and R phase) using the above-mentioned equation (8), calculates Ior(s) generated in the S phase using the above-mentioned equation (9), and calculates Ior(r) generated in the R phase using the above-mentioned equation (10).

[0057] In this way, in the inspection method, when the phase angle range falls within the first angle range R1, the Ior generated in the R phase and the T phase can be accurately calculated using equations (2), (3), and (4). When the phase angle range falls within the second angle range R2, the Ior generated in the T phase and the S phase can be accurately calculated using equations (5), (6), and (7). When the phase angle range falls within the third angle range R3, the Ior generated in the S phase and the R phase can be accurately calculated using equations (8), (9), and (10). The calculated Ior can be used to inspect or monitor the star-connected electric line under test.

[0058] (Regarding the Inspection Program) When Ior occurs in one or both of the two phases, the inspection program accurately calculates the Ior occurring in each phase and inspects or monitors the star-connected electric line under test. The inspection program is mainly composed of the following steps and is executed by computer 500 (hardware).

[0059] Step 1: Detecting a leakage current flowing in a measured electric line having R, S, and T phases connected in a star connection; Step 2: Detecting a voltage applied to the measured electric line; Step 3: Detecting a phase angle based on the leakage current detected in Step 1 and the voltage detected in Step 2; Step 4: Determining whether the phase angle detected in Step 3 belongs to a first angle range R1 between the first and second phases, a second angle range R2 between the second and third phases, or a third angle range R3 between the third and first phase; Step 5: Calculating a resistance component leakage current due to ground insulation resistance contained in the leakage current flowing in the measured electric line based on the angle range to which the phase angle determined in Step 4 belongs, the phase angle detected in Step 3, and the leakage current detected in Step 1.

[0060] Here, the configuration and operation of the computer 500 will be described with reference to the drawings. As shown in Fig. 9, the computer 500 is configured by connecting a processor 501, a memory 502, a storage 503, an input / output I / F 504, and a communication I / F 505 via a bus A, and these components work together to realize the functions and / or methods described in this disclosure.

[0061] The input / output I / F 504 is connected to, for example, a display that displays various information and a touch panel that accepts user operations. The touch panel is located in front of the display. Thus, the user can perform intuitive operations by touching icons displayed on the display with their fingers. The touch panel does not have to be located in front of the display. Furthermore, a configuration in which a pointing device such as a keyboard and a mouse is connected to the input / output I / F 504 instead of or together with the touch panel may also be used. Furthermore, a speaker that outputs sound to the outside and a microphone that inputs sound from the outside may also be connected to the input / output I / F 504.

[0062] The display is configured by a liquid crystal display or an organic EL (Electro Luminescence) display, and displays various information under the control of the processor 501 .

[0063] The memory 502 is configured by a RAM (Random Access Memory). The RAM is configured by a volatile memory or a non-volatile memory.

[0064] The storage 503 is configured with a read-only memory (ROM). The ROM is configured with a non-volatile memory, and is realized by, for example, a hard disk drive (HDD) or a solid state drive (SSD). The storage 503 stores various programs, such as the inspection programs realized in the above-described steps 1 to 5.

[0065] For example, the processor 501 controls the overall operation of the computer 500. The processor 501 is an arithmetic unit that loads an operating system and various programs that realize various functions from the storage 503 into the memory 502 and executes instructions included in the loaded programs.

[0066] Specifically, when processor 501 receives a user operation, it reads a program (e.g., an inspection program) stored in storage 503, loads the read program into memory 502, and executes the program. Furthermore, by processor 501 executing the inspection program, the functions of leakage current detection unit 11, voltage detection unit 12, phase angle detection unit 13, determination unit 14, and calculation unit 15 are realized.

[0067] Here, we will explain the configuration of the processor 501. The processor 501 is realized by, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), various other arithmetic devices, or a combination of these.

[0068] Furthermore, in order to realize the functions and / or methods described in the present disclosure, some or all of the functions of the processor 501, memory 502, storage 503, etc. may be configured in a processing circuit 601, which is dedicated hardware, as shown in Fig. 10. The processing circuit 601 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0069] Furthermore, although the processor 501 has been described as a single component, the present invention is not limited to this and may be configured as a set of multiple physically separate processors. In this specification, a program described as being executed by the processor 501 or instructions included in the program may be executed by a single processor 501, or may be executed in a distributed manner by multiple processors. Furthermore, a program executed by the processor 501 or instructions included in the program may be executed by multiple virtual processors.

[0070] The communication I / F 505 is an interface that complies with a predetermined communication standard, and communicates with external devices via wire or wirelessly.

[0071] In this way, when the inspection program is executed by the computer 500, if the phase angle range falls within the first angle range R1, the Ior generated in the R phase and the T phase can be accurately calculated using equations (2), (3), and (4). If the phase angle range falls within the second angle range R2, the Ior generated in the T phase and the S phase can be accurately calculated using equations (5), (6), and (7). If the phase angle range falls within the third angle range R3, the Ior generated in the S phase and the R phase can be accurately calculated using equations (8), (9), and (10). The calculated Ior can be used to inspect or monitor the star-connected electric line under test.

[0072] REFERENCE SIGNS LIST 1 Inspection device 10 Zero-phase current transformer 11 Leakage current detection unit 12 Voltage detection unit 13 Phase angle detection unit 14 Determination unit 15 Calculation unit

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