Partial discharge detection device, partial discharge detection method, and partial discharge detection system

Abstract

Provided is a partial discharge detection device that can reduce estimation error of the direction of arrival of a surface current and improve estimation accuracy, even when noise is superimposed.　A partial discharge detection device (200) comprises: a surface current sensor (300) that is disposed on the surface of a housing of electric power equipment (100), the surface current sensor (300) including an upper electrode (1), a lower electrode (2) provided in the vicinity of the surface of the housing of the electric power equipment (100), an insulating spacer (3) provided between the upper electrode (1) and the lower electrode (2), and three or more signal terminals (4) provided on the lower electrode (2) and connected via the upper electrode (1) and a coupling line (7); a surface current detection circuit (25) that determines whether or not a surface current has been generated on the surface of the housing of the electric power equipment (100) on the basis of the intensity of a signal outputted from each signal terminal (4); an direction-of-arrival estimation circuit (26) that calculates a computation value by dividing an output voltage difference between two signal terminals (4) by an output voltage of a maximum output terminal, which is a signal terminal (4) having the greatest output voltage, and estimates the direction of arrival of the surface current generated on the surface of the housing of the electric power equipment (100) using the calculated computation value and direction-of-arrival association information indicating the association between preliminarily obtained computation values and directions of arrival of surface currents, the two signal terminals (4) being respectively closest to locations having an angle of 90 degrees and an angle of -90 degrees among angles between a straight line connecting the maximum output terminal with the center of the lower electrode (2), and straight lines connecting the signal terminals (4) other than the maximum output terminal with the center of the lower electrode (2); and an internal discharge determination circuit (27) that determines the presence or absence of partial discharge inside the electric power equipment (100) on the basis of the determination result from the surface current detection circuit (25) and the estimation result from the direction-of-arrival estimation circuit (26).

Description

Partial discharge detection device, partial discharge detection method, and partial discharge detection system

[0001] The present disclosure relates to a partial discharge detection device, a partial discharge detection method, and a partial discharge detection system.

[0002] Since high reliability is required for electric power equipment, there is a strong demand for diagnosing abnormalities inside the equipment, which are hidden by metal casings. For this reason, diagnostic methods that utilize electromagnetic waves generated inside the equipment are commonly used for diagnosing such electric power equipment, and in particular, surface current sensors that have good sensitivity when installed outside the equipment are often used.

[0003] A surface current sensor measures electromagnetic waves (hereinafter referred to as surface current) that leak onto the surface of the housing of an electric power device due to partial discharge from the electric power device. However, it is difficult to determine whether the surface current measured by the surface current sensor is due to partial discharge from the electric power device or electromagnetic noise (external electromagnetic field) outside the electric power device. For this reason, as a technology for determining surface current, for example, Patent Document 1 discloses a partial discharge detection device that estimates the direction of arrival of the surface current using the ratio of output voltages of multiple signal terminals provided on the surface current sensor.

[0004] International Publication No. 2021 / 260820

[0005] The partial discharge detection device estimates the direction of arrival of the surface current using the ratio of the output voltages of multiple signal terminals provided in the surface current sensor, and can suppress fluctuations in detection sensitivity regardless of the installation environment of the surface current sensor. On the other hand, the output of the signal terminal becomes small depending on the direction of arrival of the surface current, and if noise is superimposed on the signal terminal with a small output voltage, the estimation error of the direction of arrival of the surface current becomes large.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a partial discharge detection device that can reduce estimation errors in the direction of arrival of surface currents and improve estimation accuracy even when noise is superimposed.

[0007] The partial discharge detection device according to the present disclosure includes a surface current sensor arranged on the surface of the housing of the electric power equipment, the surface current sensor having an upper electrode, a lower electrode provided close to the surface of the housing of the electric power equipment, an insulating spacer provided between the upper electrode and the lower electrode, and three or more signal terminals connected to the upper electrode via bonding wires and provided on the lower electrode; a surface current detection circuit that determines whether a surface current has occurred on the surface of the housing of the electric power equipment based on the intensity of the signal output of the signal terminal; an arrival direction estimation circuit that calculates a calculated value by dividing the output voltage difference between two signal terminals that are closest to positions where the angles formed by a line connecting the center of the maximum output terminal and the lower electrode and a line connecting the centers of the signal terminals other than the maximum output terminal and the lower electrode are 90 degrees and -90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of the surface current occurring on the surface of the housing of the electric power equipment using the calculated value and arrival direction correspondence information that indicates a correspondence between the previously acquired calculated value and the arrival direction of the surface current; and an internal discharge determination circuit that determines whether a partial discharge has occurred inside the electric power equipment based on the determination result of the surface current detection circuit and the estimation result of the arrival direction estimation circuit.

[0008] Furthermore, the partial discharge detection method according to the present disclosure includes the steps of: determining whether or not a surface current has occurred on the surface of the housing of the electric power equipment based on the strength of the signal output of the signal terminal provided in the surface current sensor; calculating a calculated value by dividing the output voltage difference between the two signal terminals that are closest to the positions where the angles formed by the line connecting the center of the maximum output terminal, which is the signal terminal with the highest output voltage, and the center of the lower electrode and the line connecting the centers of the signal terminals other than the maximum output terminal and the lower electrode are 90 degrees and -90 degrees, respectively, by the output voltage of the maximum output terminal; and estimating the arrival direction of the surface current occurring on the surface of the housing of the electric power equipment using arrival direction correspondence information that indicates the correspondence between the previously acquired calculated value and the arrival direction of the surface current and the calculated calculated value; and determining whether or not a partial discharge has occurred inside the electric power equipment based on the determination result of the step of determining whether or not a surface current has occurred and the estimation result of the step of estimating the arrival direction of the surface current.

[0009] According to the partial discharge detection device of the present disclosure, the difference in output voltage between the two signal terminals that are closest to the positions where the angles between the line connecting the center of the maximum output terminal, which is the signal terminal with the highest output voltage, and the center of the lower electrode and the line connecting the centers of the signal terminals other than the maximum output terminal and the lower electrode are 90 degrees and -90 degrees, respectively, is divided by the output voltage of the maximum output terminal.This has the effect of reducing the estimation error in the direction of arrival of the surface current and improving the estimation accuracy even when noise is superimposed on the output of the surface current sensor.

[0010] Furthermore, according to the partial discharge detection method of the present disclosure, the difference in output voltage between the two signal terminals that are closest to the positions where the angles between the line connecting the center of the maximum output terminal, which is the signal terminal with the highest output voltage, and the center of the lower electrode and the line connecting the centers of the signal terminals other than the maximum output terminal and the lower electrode are 90 degrees and -90 degrees are used, by dividing the difference in output voltage between the two signal terminals by the output voltage of the maximum output terminal. This has the effect of reducing the estimation error in the direction of arrival of the surface current and improving the estimation accuracy even when noise is superimposed on the output of the surface current sensor.

[0011] 1 is a configuration diagram of a partial discharge detection system according to a first embodiment. FIG. 2 is a hardware configuration diagram of a partial discharge detection device according to a first embodiment. FIG. 3 is a vertically downward cross-sectional view taken along line A-A' in FIG. 3 of the partial discharge detection device according to the first embodiment. FIG. 4 is a diagram showing a modified example of the surface current sensor of the partial discharge detection device according to the first embodiment. FIG. 5 is a diagram showing a lower electrode of the surface current sensor of the partial discharge detection device according to the first embodiment as viewed from above. FIG. 6 is an equivalent circuit diagram of the surface current sensor of the partial discharge detection device according to the first embodiment. FIG. 7 is a diagram showing a relationship between an output signal of each signal terminal in an arithmetic processing unit of the partial discharge detection device according to the first embodiment and an arrival direction of a surface current. FIG. 8 is a configuration diagram of an arithmetic processing unit of the partial discharge detection device according to the first embodiment. FIG. 9 is a processing flow diagram in an arrival direction estimation circuit of the arithmetic processing unit of the partial discharge detection device according to the first embodiment. FIG. 10 is a diagram showing arrival direction correspondence information showing a correspondence relationship between a calculated value and an arrival direction of a surface current. FIG. 11 is a configuration diagram of a partial discharge detection system according to a second embodiment. FIG. 12 is a cross-sectional view of a partial schematic diagram of a partial discharge detection device according to the second embodiment. FIG. 13 is a configuration diagram of an arithmetic processing unit of the partial discharge detection device according to the second embodiment. Fig. 1 is a configuration diagram of a partial discharge detection system according to a third embodiment. Fig. 2 is a partial schematic diagram of a partial discharge detection device according to a third embodiment. Fig. 3 is a configuration diagram of an arithmetic processing unit of a partial discharge detection device according to a third embodiment. Fig. 4 is a configuration diagram of a partial discharge detection system according to a fourth embodiment. Fig. 5 is a partial schematic diagram of a partial discharge detection device according to a fourth embodiment. Fig. 6 is a configuration diagram of an arithmetic processing unit of a partial discharge detection device according to a fourth embodiment.

[0012] The following describes embodiments in detail with reference to the accompanying drawings. Note that the embodiments described below are merely examples. The embodiments can be implemented in appropriate combination.

[0013] First Embodiment. Fig. 1 is a configuration diagram of a partial discharge detection system according to a first embodiment. Fig. 2 is a hardware configuration diagram of a partial discharge detection device according to the first embodiment. Fig. 3 is an external perspective view of a surface current sensor of the partial discharge detection device according to the first embodiment. Fig. 4 is a cross-sectional view of the surface current sensor of the partial discharge detection device according to the first embodiment. Fig. 5 is a diagram showing a modified example of the surface current sensor of the partial discharge detection device according to the first embodiment. Fig. 6 is a diagram showing a top view of the lower electrode of the surface current sensor of the partial discharge detection device according to the first embodiment. Fig. 7 is an equivalent circuit diagram of the surface current sensor of the partial discharge detection device according to the first embodiment. Fig. 8 is a diagram showing the relationship between the output signals of each signal terminal in the arithmetic processing unit of the partial discharge detection device according to the first embodiment and the direction of arrival of the surface current. Fig. 9 is a configuration diagram of the arithmetic processing unit of the partial discharge detection device according to the first embodiment. Fig. 10 is a processing flow diagram of an arrival direction estimation circuit of the arithmetic processing unit of the partial discharge detection device according to the first embodiment. Fig. 11 is a diagram showing arrival direction correspondence information showing the correspondence relationship between calculated values ​​and the arrival directions of the surface currents.

[0014] 1, a partial discharge detection system 1000 according to this embodiment is configured with an electric power device 100 and a partial discharge detection device 200. The partial discharge detection system 1000 includes the partial discharge detection device 200 that detects the presence or absence of internal discharge, and the electric power device 100 with the partial discharge detection device 200 arranged on the surface of the housing.

[0015] The electric power device 100 is covered with a metal or resin housing and is kept at a ground potential. When the electric power device 100 is covered with a resin housing, it is preferable to apply a conductive coating or the like to keep the ground potential. Note that the electric power device 100 in this embodiment may be, for example, an oil-filled transformer, a gas-insulated transformer, a molded transformer, a gas-insulated switchgear, a cubicle-type gas-insulated switchgear, a generator, a rotating machine, a voltage transformer, or a voltage transformer, but is not limited to these.

[0016] Next, a description will be given of the partial discharge detection device 200. The partial discharge detection device 200 includes a surface current sensor 300, a calculation processing unit 400, and a display unit 500.

[0017] 2 is a hardware configuration diagram of a partial discharge detection device 200 according to the present disclosure. The partial discharge detection device 200 is configured to include a processor 10 such as a CPU (Central Processing Unit), a memory 11 such as a RAM (Random Access Memory), a display 12, and an input interface (I / F) 13. The calculation processing unit 400 is realized by the processor 10 executing a program stored in the memory 11. However, these may also be realized by, for example, a plurality of processors 10 working together.

[0018] The surface current sensor 300 is disposed on the surface of the housing of the electric power equipment 100 and detects the electromagnetic field generated by the surface current generated on the surface of the housing of the electric power equipment 100. Specifically, the surface current generated on the surface of the housing appears when electromagnetic waves generated due to partial discharge inside the electric power equipment 100 leak out to the surface of the housing of the electric power equipment 100 through electrical openings. Therefore, the surface current sensor 300 detects the electromagnetic field generated by the surface current flowing on the surface of the housing of the electric power equipment 100. Here, the electrical opening refers to a portion formed of resin or the like that draws in high voltage, and is generally provided in the electric power equipment 100.

[0019] Furthermore, since the electromagnetic field generated by the surface current flowing on the housing surface of the electric power device 100 is stronger the closer it is to the housing surface, the detection sensitivity of the surface current sensor 300 decreases if the surface current sensor 300 is installed away from the housing surface of the electric power device 100. Therefore, when installing the surface current sensor 300, a flat surface with few irregularities is selected, and the surface is placed in close contact with the housing surface of the electric power device 100 in a position close to the electrical opening, thereby enabling high-sensitivity detection of the electromagnetic field generated by the surface current.

[0020] Note that what the surface current sensor 300 actually detects is the electromagnetic field generated by the surface current. However, since the purpose of the surface current sensor 300 is to detect the surface current, unless there is a particular need to distinguish between them, it will be appropriately described as the surface current sensor 300 detecting the surface current. The principle of detection of the electromagnetic field generated by the surface current by the surface current sensor 300 will be described in detail later.

[0021] Next, the structure and function of the surface current sensor 300 will be explained using Figures 3 and 4. Figure 3 is an external perspective view of the surface current sensor 300. Figure 4 is a cross-sectional view taken along the line A-A' in Figure 3, cut vertically downward. Note that the power equipment 100 is not shown in Figure 3. The vertically downward direction here refers to the direction in which gravity acts.

[0022] As shown in Figures 3 and 4, the surface current sensor 300 is arranged on the surface of the housing of the power equipment 100, and includes an upper electrode 1, a lower electrode 2, an insulating spacer 3, a bonding wire 7 and a signal terminal 4.

[0023] The upper electrode 1 and the lower electrode 2 are provided so as to be stacked on the surface of the housing of the electric power device 100. That is, the lower electrode 2 is provided close to the surface of the housing of the electric power device 100, and the upper electrode 1 is provided above the lower electrode 2. Here, the upper electrode 1 and the lower electrode 2 may be made of, for example, a metal, but are not limited to this and may be made of any conductive material.

[0024] The term "close" here refers to the position where the surface of the housing of the electric power device 100 and the lower electrode 2 are close to each other, and for example, as shown in Fig. 4, the surface of the housing of the electric power device 100 and the lower electrode 2 may be provided with a gap between them. Alternatively, the surface of the housing of the electric power device 100 and the lower electrode 2 may be provided in close contact with each other. By providing the lower electrode 2 in close contact with the surface of the housing of the electric power device 100, it is possible to increase the voltage generated between the upper electrode 1 and the lower electrode 2 due to the electric field generated by the surface current.

[0025] The insulating spacer 3 is made of insulating resin and is provided between the upper electrode 1 and the lower electrode 2 to maintain insulation. While Fig. 4 shows an example in which the insulating spacer 3 is provided with a gap between the upper electrode 1 and the lower electrode 2, this is not limiting, and a space may be provided by cutting out a portion of the insulating spacer 3. By cutting out a portion of the insulating spacer 3 in this way to provide a space, the dielectric constant of the insulating spacer 3 can be changed and the weight of the surface current sensor 300 can be reduced.

[0026] The coupling wire 7 has one end connected to the upper electrode 1 and the other end connected to the signal terminal 4. The coupling wire 7 is a conductor that transmits the potential of the upper electrode 1 to the core wire 6 of the cable 5 externally attached to the signal terminal 4 via the signal line of the signal terminal 4. The outer sheath of the coupling wire 7 is arranged to be in contact with the lower electrode 2. Note that, although an L-shaped coupling wire 7 is shown in FIG. 4 as an example, the shape is not limited to this.

[0027] The signal terminal 4 is connected to the upper electrode 1 via a bonding wire 7. Three or more signal terminals 4 are provided on the lower electrode 2. For example, the surface current sensor 300 shown in FIG. 3 has four signal terminals 4, i.e., signal terminals 4a, 4b, 4c, and 4d, each of which is provided at one corner of the lower electrode 2, in the shape of a square prism.

[0028] 3 has a cubic shape in which the distance between adjacent signal terminals 4 is equal and the distance is also equal to the height of the surface current sensor 300 when the surface current sensor 300 is installed on the surface of the housing of the power equipment 100. The number of signal terminals 4 provided on the lower electrode 2 of the surface current sensor 300 is not limited as long as it is three or more, but the greater the number of signal terminals 4, the better the accuracy of estimating the direction of arrival of the surface current.

[0029] One end of the signal wire of the signal terminal 4 is connected to the coupling wire 7 of the surface current sensor 300, and the other end is connected to the core wire 6 of the cable 5. The cable 5 is an externally attached electric wire for transmitting the potential of the upper electrode 1 to the arithmetic processing unit 400. For example, cables 5a, 5b, 5c, and 5d are connected to the four signal terminals 4a, 4b, 4c, and 4d of the surface current sensor 300 shown in FIG. 3, respectively.

[0030] Here, the core wire 6 of the cable 5 refers to a signal wire for electrically connecting to the signal wire of the signal terminal 4. The type of the signal terminal 4 is generally a BNC (Bayonet-Neill-Concelman) connector or an SMA (SubMiniature version A) connector, but is not limited to these.

[0031] Regarding the shape of the surface current sensor 300, Figure 3 shows an example in which the shape of the surface current sensor 300 is cubic, but it does not necessarily have to be angular, and the corners may be chamfered to match the signal terminal 4 as shown in Figure 3.

[0032] In this embodiment, the surface current sensor 300 is described as having a rectangular prism shape in which four signal terminals 4 are provided at each of the four corners of the lower electrode 2, but is not limited to this. For example, it may have a polygonal prism shape or a cylindrical shape as shown in FIG.

[0033] Fig. 5 shows an example of a cylindrical surface current sensor 300. In the case of the cylindrical surface current sensor 300 shown in Fig. 5, it is preferable to provide the signal terminals 4 at positions rotated 90 degrees in the direction of arrangement of the signal terminals 4 with respect to a central axis that passes through the center of the lower electrode 2 and is perpendicular to the surface of the housing of the electric power device 100, but this is merely an example and is not limiting. Details will be described using Fig. 6.

[0034] 6 is a view of the lower electrode 2 of the surface current sensor 300 shown in FIG. 3 as seen from above, i.e., from the upper electrode 1 side. The arrow indicates the arrangement direction of the signal terminals 4, and shows a clockwise rotation as an example. The center of the lower electrode 2 is also shown. The center of the lower electrode 2 refers to the center of gravity of the lower electrode 2.

[0035] As shown in Fig. 6, signal terminals 4a, 4b, 4c, and 4d are provided in the square of the lower electrode 2 so that adjacent signal terminals 4 are equally spaced in the arrangement direction of the signal terminals 4. For example, if the direction of the arrow shown in Fig. 6 is positive, Fig. 6 shows an example in which the angle between the line connecting the center of the signal terminal 4a and the lower electrode 2 and the line connecting the center of the signal terminal 4b and the lower electrode 2 is 90 degrees. That is, in this case, the angle between the line connecting the center of the signal terminal 4a and the lower electrode 2 and the line connecting the center of the signal terminal 4d and the lower electrode 2 is -90 degrees.

[0036] Here, the arrangement direction of the signal terminal 4 in this embodiment refers to the direction in which the signal terminal 4 is arranged with respect to the central axis of the lower electrode 2 of the surface current sensor 300, i.e., the rotation direction when the central axis of the lower electrode 2 is rotated in the direction in which the adjacent signal terminal 4 is located around the axis. Also, the central axis of the lower electrode 2 refers to the axis that passes through the center of the lower electrode 2 in Figure 6 and extends in the depth direction, i.e., the axis that passes through the center of the lower electrode 2 and is perpendicular to the surface of the housing of the electric power equipment 100 when the surface current sensor 300 is arranged on the surface of the housing of the electric power equipment 100.

[0037] As described above, the surface current sensor 300 is configured such that the signal terminals 4 are arranged at equal intervals in the arrangement direction of the lower electrode 2, thereby making it possible to equalize the interlinkage surfaces of the magnetic flux, thereby making it possible to make the estimation accuracy uniform regardless of the direction of the surface current arrival. The interlinkage surfaces of the magnetic flux referred to here will be explained later.

[0038] Furthermore, the signal terminals 4 arranged on the lower electrode 2 of the surface current sensor 300 do not have to be provided at the corners, and the number of corners does not have to be the same as the number of signal terminals 4. For example, in the case of a surface current sensor 300 having a rectangular prism shape, the sensor may have a configuration in which signal terminals 4 are provided at the four corners of the lower electrode 2 and between each corner, for a total of eight signal terminals 4.

[0039] Next, a description will be given of the principle of detecting an electromagnetic field by the surface current sensor 300. The principle of detecting an electromagnetic field will be described with reference to FIG.

[0040] Partial discharges caused by poor insulation inside the electric power equipment 100 pass through electrical openings and generate surface currents on the surface of the housing of the electric power equipment 100, which generates an electromagnetic field. Specifically, the surface currents flowing on the surface of the housing of the electric power equipment 100 generate electric fields in a direction perpendicular to the surface of the housing of the electric power equipment 100. Furthermore, the surface currents generate magnetic fields in a direction parallel to the surface of the housing of the electric power equipment 100 and perpendicular to the propagation direction of the surface currents.

[0041] The electric field generated by the surface current generates a voltage between the upper electrode 1 and the lower electrode 2, and this voltage propagates, for example, through the cable 5a, signal terminal 4a, signal terminal 4c, and cable 5c in that order. The magnetic field generated by the surface current interlinks the plane surrounded by the upper electrode 1, the lower electrode 2, and the coupling wires 7a and 7c, i.e., the magnetic flux interlinkage plane, and causes electromagnetic induction.

[0042] According to the input impedance of the cables 5a, 5c viewed from the signal terminals 4a, 4c, a voltage is generated between the signal lines of the signal terminals 4a, 4c and the outer sheaths of the cables 5a, 5c. That is, a signal consisting of two superimposed voltages, one caused by the electric field generated by the surface current and the other caused by the magnetic field generated by the surface current, propagates through the cables 5a, 5c. In this way, the surface current sensor 300 detects the electric field and magnetic field, i.e., the electromagnetic field, generated by the surface current.

[0043] Next, the signals detected by the surface current sensor 300 will be described with reference to Fig. 7. Fig. 7 is an equivalent circuit diagram of the surface current sensor 300. In Fig. 7, the resistances of the signal terminal 4a and the bonded wire 7 and the signal terminal 4c and the bonded wire 7 are R1 and R2, the inductances of the signal terminal 4a and the bonded wire 7a and the signal terminal 4c and the bonded wire 7c are L1 and L2, the electrostatic capacitance of the insulating spacer 3 is C, and the input impedances of the signal terminals 4a and 4c are Z1 and Z2.

[0044] 7, resistances R1 and R2 and inductances L1 and L2 are generated in a bond line 7, one end of which is connected to the upper electrode 1 and the other end of which is connected to the signal terminal 4. Capacitance C is the electrostatic capacitance of the insulating spacer 3. Input impedances Z1 and Z2 of the signal terminals 4a and 4c are also connected to both ends of the equivalent circuit.

[0045] As explained above, the electromagnetic field generated by the surface current includes an electric field and a magnetic field. Therefore, the electric field generates a voltage across the capacitance C, and the magnetic field generates a voltage across the inductances L1 and L2. The voltage generated by the electric field and the magnetic field generates a voltage oscillation according to the circuit constant LCR, and the terminal voltage generated across the equivalent circuit shown in Figure 7 becomes the signal output of the surface current sensor 300.

[0046] The equivalent circuit of FIG. 7 is a circuit that is linearly symmetrical about the capacitance C, and is a closed circuit in which the input impedances Z1 and Z2 of the signal terminals 4a and 4c are connected in series to the series circuits of the LCRs.

[0047] Since the composite impedance of the LCR decreases at the LC resonant frequency, the voltages applied to the input impedances Z1 and Z2 of the signal terminals 4 a and 4 c increase. Therefore, the voltages generated at the signal terminals 4 a and 4 c of the surface current sensor 300 are the largest for the components of the incoming surface current and the electromagnetic field generated by the surface current that match the LC resonant frequency.

[0048] On the other hand, among the frequency components of the incoming surface current and the electromagnetic field generated by the surface current, those with frequency components lower than the LC resonance frequency increase the impedance of capacitance C, thereby decreasing the voltage generated at signal terminals 4a and 4c. Also, among the frequency components of the incoming surface current and the electromagnetic field generated by the surface current, those with frequency characteristics higher than the LC resonance frequency increase the impedance of inductances L1 and L2, thereby decreasing the voltage generated at signal terminals 4a and 4c.

[0049] Here, the directivity exhibited by the surface current sensor 300 will be explained. Fig. 8 is a diagram showing the relationship between the direction of arrival of the surface current detected at each signal terminal 4 and the output signal, with the horizontal axis representing angles and the vertical axis representing arbitrary units. In Fig. 8, the solid line represents a waveform showing the relationship between the direction of arrival of the surface current at signal terminal 4a and the output signal, the dotted line represents a waveform showing the relationship between the direction of arrival of the surface current at signal terminal 4c and the output signal, the dashed-dotted line represents a waveform showing the relationship between the direction of arrival of the surface current at signal terminal 4b and the output signal, and the dashed-two-dotted line represents a waveform showing the relationship between the direction of arrival of the surface current at signal terminal 4d and the output signal.

[0050] Here, the output signal on the vertical axis in Fig. 8 refers to an output voltage normalized so that the maximum is 1. For example, if the vertical axis in Fig. 8 represents the output voltage, the amplitude of the waveform shown in Fig. 8 will vary depending on the strength of the partial discharge, the size of the surface current sensor 300, etc. For this reason, in Fig. 8, the vertical axis represents the normalized output voltage, for which fluctuations in the amplitude of the waveform do not need to be taken into consideration, and the vertical axis is expressed in arbitrary units.

[0051] The arrival direction on the horizontal axis indicates the arrival direction of the surface current detected by each signal terminal 4 of the surface current sensor 300, and the direction from signal terminal 4c to signal terminal 4a of the surface current sensor 300 shown in Fig. 3 is set to 0 degrees, i.e., the initial position, and the surface current sensor 300 is rotated clockwise around the central axis of the lower electrode 2 in the direction of arrangement of the signal terminals 4. In other words, for example, an arrival direction of 90 degrees in Fig. 8 means that the surface current sensor 300 shown in Fig. 3 is rotated clockwise by 90 degrees in the direction of arrangement of the signal terminals 4 around the central axis of the lower electrode 2.

[0052] Here, the arrival direction of the surface current in this embodiment refers to the direction in which the surface current arrives, i.e., the direction in which the surface current flows. In Fig. 8, the arrival direction of the surface current itself does not change, but because the surface current sensor 300 is rotated clockwise around the central axis of the lower electrode 2 in the arrangement direction of the signal terminals 4, the arrival direction of the surface current detected by each signal terminal 4 changes. For this reason, Fig. 8 illustrates waveforms that represent the relationship between the arrival direction and the output signal of each signal terminal 4, with the horizontal axis representing the arrival direction.

[0053] As described above, for the magnetic field generated by the surface current, the plane surrounded by the upper electrode 1, the lower electrode 2, and the coupling lines 7a and 7c is the interlinkage plane of the magnetic flux, and the voltage generated on this plane is proportional to the area of ​​this plane.

[0054] The magnetic field generated by the surface current is formed in a direction perpendicular to the propagation direction of the surface current. Therefore, the interlinkage magnetic flux penetrating the magnetic flux interlinkage surface changes depending on the angle at which the surface current sensor 300 is placed. As a result, the voltage due to the magnetic field generated at the signal terminals 4a and 4c changes depending on the angle at which the surface current sensor 300 is placed, and describes a sine function as shown in FIG. 8. This is the basic principle of the directivity exhibited by the surface current sensor 300. In the present disclosure, this principle is used to estimate the arrival direction of the surface current, which will be described later.

[0055] For example, when the surface current sensor 300 is positioned so that the interlinkage plane of the magnetic flux is parallel to the direction of the surface current, the absolute value of the voltage generated by the magnetic field at the signal terminals 4 a and 4 c becomes the largest. On the other hand, it is necessary to take into account that a voltage is generated at the signal terminals 4 a and 4 c due to the electric field.

[0056] Since a voltage due to the electric field is also generated in the signal terminals 4a and 4c, the polarity of the voltage due to the magnetic field is different between the signal terminals 4a and 4c in the surface current sensor 300 shown in Figure 4, and the ratio of the voltages at the signal terminals 4a and 4c is the largest value.

[0057] Furthermore, when the surface current sensor 300 is positioned so that the interlinkage plane of the magnetic flux is perpendicular to the direction of the surface current, the absolute value of the voltage generated by the magnetic field at the signal terminals 4 a and 4 c is smallest. At this time, the voltages at the signal terminals 4 a and 4 c are equivalent, and the ratio of the voltages at the signal terminals 4 a and 4 c is close to 1.

[0058] A signal detected by the surface current sensor 300 is input to the calculation processing unit 400 via the cables 5a and 5c. The cables 5a and 5c are arranged along the surface of the housing of the electric power device 100. At this time, due to the influence of the electromagnetic field, a potential vibration occurs in the outer sheath of the cables 5a and 5c relative to the surface of the housing of the electric power device 100, which is at ground potential. This potential vibration propagates through the cables 5a and 5c and is input to the surface current sensor 300. Furthermore, this potential vibration propagates from the outer sheath of the cables 5a and 5c to the outer sheath of the signal terminals 4a and 4c and to the lower electrode 2 in this order.

[0059] Here, since the lower electrode 2 is provided close to the surface of the housing of the electric power device 100, the impedance between the lower electrode 2 and the surface of the housing of the electric power device 100 is extremely small compared to the impedance between the upper electrode 1 and the lower electrode 2. Therefore, the potential vibration generated in the lower electrode 2 does not affect the upper electrode 1.

[0060] In particular, when estimating the direction of arrival of a surface current, an error in direction estimation occurs if a voltage due to the influence of an external electromagnetic field is superimposed on the voltage received by the cable 5. However, by providing the lower electrode 2 close to the surface of the housing of the electric power device 100 and arranging the cable 5 of the signal terminal 4 along the surface of the housing of the electric power device 100, the influence of the electromagnetic field received by the cable 5 can be suppressed.

[0061] Next, the configuration and operation of the arithmetic processing unit 400 will be described with reference to Fig. 9. Fig. 9 is a configuration diagram of the arithmetic processing unit 400 of the partial discharge detection device 200 according to this embodiment. In Fig. 8, "PT" represents the protection circuit 21, "FL" represents the filter 22, "AMP" represents the signal amplification circuit 23, "A / D" represents the A / D converter 24, "SCD" represents the surface current detection circuit 25, "DLE" represents the direction of arrival estimation circuit 26, and "IDJ" represents the internal discharge determination circuit 27.

[0062] The arithmetic processing unit 400 includes a protection circuit 21, a filter 22, a signal amplifier circuit 23, an A / D (Analog to Digital) converter 24, a surface current detection circuit 25, a direction of arrival estimation circuit 26, and an internal discharge determination circuit 27. As shown in Fig. 9, the protection circuit 21, the filter 22, the signal amplifier circuit 23, and the A / D converter 24 are provided for signals from each of the signal terminals 4a, 4b, 4c, and 4d. Note that while Fig. 9 shows a configuration diagram of the arithmetic processing unit 400 of the surface current sensor 300 having four signal terminals 4 shown in Fig. 3, the configuration is not limited to this, and the protection circuit 21, the filter 22, the signal amplifier circuit 23, and the A / D converter 24 are provided according to the number of signal terminals 4 of the surface current sensor 300.

[0063] The protection circuit 21 is a circuit for preventing breakdowns due to the intrusion of high-voltage signals. The protection circuit 21 uses elements such as diodes and arresters to remove voltages above a predetermined value. The predetermined value varies depending on the withstand voltage of the elements used in the protection circuit 21, but is generally around 100 V.

[0064] The filter 22 is a bandpass filter for extracting only signals of a specific frequency of the electromagnetic field caused by partial discharges generated inside the power device 100 to be diagnosed. Here, the specific frequency of the electromagnetic field caused by partial discharges refers to frequency components that are prominently observed in the electromagnetic field caused by partial discharges. Since signals of frequency components outside this frequency band are caused by external electromagnetic fields, by using the filter 22 to extract only the specific frequency, it is possible to suppress the influence of external electromagnetic fields.

[0065] The signal amplifier circuit 23 is a circuit for amplifying the signal from which only the specific frequency has been extracted by the filter 22, and generally uses an operational amplifier. The signal amplified by the signal amplifier circuit 23 is output to an A / D converter 24 and a surface current detection circuit 25.

[0066] The A / D converter 24 converts the signal input from the signal amplifier circuit 23 into a digital signal and outputs it to the direction of arrival estimation circuit 26 .

[0067] The surface current detection circuit 25 determines whether a surface current has occurred on the surface of the housing of the electric power device 100 based on the strength of the signal output of each signal terminal 4 input from the signal amplifier circuit 23. The surface current detection circuit 25 is a comparator, and determines that a surface current has occurred due to partial discharge occurring inside the electric power device 100 when, for example, the strength of the signal output of the signal terminal 4 exceeds a preset threshold. Here, the strength of the signal output refers to, for example, amplitude.

[0068] The preset threshold is set to a value higher than the signal strength obtained by the external electromagnetic field in the installation environment of the electric power device 100. This makes it possible to prevent erroneous determination. The preset threshold and the determination result of the surface current detection circuit 25 may be stored in a storage unit (not shown).

[0069] The direction-of-arrival estimation circuit 26 estimates the direction of arrival of the surface current from the output voltage of each signal terminal 4. The procedure for estimating the direction of arrival of the surface current in the direction-of-arrival estimation circuit 26 will be described below with reference to Figs. 10 and 11. Fig. 10 is a processing flow diagram in the direction-of-arrival estimation circuit 26 of the calculation processing unit 400. Fig. 11 is a diagram showing direction-of-arrival correspondence information indicating the correspondence between the calculated value and the direction of arrival of the surface current.

[0070] 10 and 11, the procedure for estimating the direction of arrival of the surface current will be described using the surface current sensor 300 shown in Fig. 3 as an example. The output voltages of the signal terminals 4a, 4b, 4c, and 4d are Va, Vb, Vc, and Vd, respectively.

[0071] 10, in step S1, the direction-of-arrival estimation circuit 26 compares the output voltages of the signal terminals 4 of the surface current sensor 300 and extracts the signal terminal 4 that exhibits the maximum output voltage. In the following description, the signal terminal 4 that exhibits the maximum output voltage will be referred to as the maximum output terminal.

[0072] The following steps S2 to S5 vary depending on the signal terminal 4 extracted in step S1. If signal terminal 4a is extracted as the maximum output terminal, proceed to step S2. If signal terminal 4b is extracted as the maximum output terminal, proceed to step S3. If signal terminal 4c is extracted as the maximum output terminal, proceed to step S4. If signal terminal 4d is extracted as the maximum output terminal, proceed to step S5.

[0073] In step S1, when extracting the signal terminal 4 showing the maximum output voltage, two maximum output terminals may be extracted. For example, in the arrival direction of 45 degrees shown in FIG. 8, signal terminals 4a and 4b have the maximum output signal, and signal terminals 4a and 4b are extracted as the maximum output terminals. In such a case, it is sufficient to extract either one of the signal terminals 4 and execute the subsequent processing flow. It does not matter which signal terminal 4 is extracted as the maximum output terminal, and the estimation result of the arrival direction of the surface current does not change depending on which signal terminal 4 is extracted.

[0074] Steps S2 to S5 will be described. In steps S2 to S5, the direction-of-arrival estimation circuit 26 calculates a calculated value by dividing the difference in output voltages of the two signal terminals 4 that are closest to the positions where the angle between the line connecting the maximum output terminal, which is the signal terminal 4 with the maximum output voltage, and the center of the lower electrode 2 and the line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 is 90 degrees and -90 degrees, respectively, by the output voltage of the maximum output terminal. Note that in steps S2 to S5, the calculation method for the calculated value differs depending on the signal terminal 4 extracted in step S1, but the rest is the same. Therefore, step S2 will be described, and a description of steps S3 to S5 will be omitted.

[0075] 10 , in step S1, direction-of-arrival estimation circuit 26 extracts the signal terminal 4 that exhibits the maximum output voltage, i.e., the maximum output terminal, and proceeds to step S2 if signal terminal 4a is extracted as the maximum output terminal. In step S2, signal terminal 4b and signal terminal 4d are the two signal terminals 4 that are closest to the positions where the angles formed by the line connecting the maximum output terminal, i.e., signal terminal 4a, which is the signal terminal 4 with the maximum output voltage, and the center of lower electrode 2 and the line connecting signal terminals 4 other than the maximum output terminal, i.e., signal terminals 4b, 4c, and 4d, and the center of lower electrode 2, are 90 degrees and −90 degrees, respectively. That is, a calculated value is calculated by dividing the output voltage difference between signal terminal 4b and signal terminal 4d by the output voltage of signal terminal 4a.

[0076] Another method for calculating the calculated value in step S2 will be described below using the central axis of the lower electrode 2. In step S2, the direction-of-arrival estimation circuit 26 calculates the calculated value by dividing the output voltage difference between the signal terminal 4 closest to a position rotated 90 degrees in the arrangement direction of the signal terminal 4 around the central axis of the lower electrode 2 with the signal terminal 4a, which is the maximum output terminal, as the reference, and the signal terminal 4 closest to a position rotated −90 degrees in the arrangement direction of the signal terminal 4, i.e., signal terminal 4b, by the output voltage of the signal terminal 4a, which is the maximum output terminal.

[0077] Further explanation will be given using FIG. 6 . In FIG. 6 , the line connecting the signal terminal 4b and the center of the lower electrode 2 is closest to the position where the angle between the maximum output terminal 4a and the line connecting the center of the lower electrode 2 is 90 degrees. Similarly, the line connecting the signal terminal 4d and the center of the lower electrode 2 is closest to the position where the angle between the maximum output terminal 4a and the line connecting the center of the lower electrode 2 is −90 degrees. From the above, in step S2, the calculated value is calculated using the following equation (1), which divides the output voltage difference between the signal terminals 4b and 4d by the output voltage of the signal terminal 4a. Similarly, in steps S3 to S5, the calculated value is calculated using the following equations (2) to (4), respectively.

[0078] (Math. 1) (Vb-Vd) / Va Formula (1)

[0079] (Math. 2) (Vc-Va) / Vb Formula (2)

[0080] (Math. 3) (Vd-Vb) / Vc Equation (3)

[0081] (Math. 4) (Va-Vc) / Vd Equation (4)

[0082] In equations (1) to (4), the output voltage difference between the two signal terminals 4 is calculated by subtracting the output voltage of the signal terminal 4 located at -90 degrees from the maximum output terminal in the direction of arrangement of the signal terminals 4 from the output voltage of the signal terminal 4 located at 90 degrees from the maximum output terminal in the direction of arrangement of the signal terminals 4, with the clockwise direction of arrangement of the signal terminals 4 relative to the central axis of the lower electrode 2 as the axis, as positive. However, this is not limited to this. The output voltage difference may also be calculated with the counterclockwise direction of arrangement of the signal terminals 4 as positive. In that case, taking equation (1) as an example, the calculated value is calculated using the following equation (5). The same applies to equations (2) to (4), so explanations will be omitted.

[0083] (Math. 5) (Vd-Vb) / Va Equation (5)

[0084] However, when calculating the calculated value, it is necessary to decide in advance which of the arrangement directions of the signal terminals 4 is to be used as the positive side for calculating the output voltage difference between the two signal terminals 4. Furthermore, it is necessary to decide in advance which of the arrangement directions of the signal terminals 4 is to be used as the positive side for calculating the output voltage difference, also when acquiring the arrival direction correspondence information described later.

[0085] 3 , the calculated value is calculated by dividing the output voltage difference between two signal terminals 4 at which the angle formed by the line connecting the maximum output terminal (the signal terminal 4 with the highest output voltage) and the center of the lower electrode 2 with the line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 is 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal. However, this is not limited to this. For example, as in the surface current sensor 300 having five signal terminals 4, the signal terminals 4 may not necessarily be located at positions at which the angle formed by the line connecting the maximum output terminal (the signal terminal 4 with the highest output voltage) and the center of the lower electrode 2 with the line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 is 90 degrees and −90 degrees. In such a case, the calculated value may be calculated by dividing the output voltage difference between the two signal terminals 4 closest to the positions at which the angle formed by the line connecting the maximum output terminal (the signal terminal 4 with the highest output voltage) and the center of the lower electrode 2 with the line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 is 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal.

[0086] In step S6, the arrival direction of the surface current generated on the housing surface of the electric power device 100 is estimated using arrival direction correspondence information indicating the correspondence relationship between the previously acquired calculation value and the arrival direction of the surface current and the calculation value calculated in steps S2 to S5. Details will be described with reference to FIG.

[0087] 11 is a diagram showing arrival direction correspondence information that indicates the correspondence relationship between the calculated value and the arrival direction of the surface current. The horizontal axis is in degrees, and the vertical axis is in arbitrary units. Note that the horizontal axis ranges from -45 degrees (315 degrees) to 45 degrees, at which the output signal from signal terminal 4a is at its maximum, as shown in FIG. 8, for example.

[0088] In step S6, the arrival direction of the surface current generated on the surface of the housing of the electric power device 100 is estimated using the arrival direction correspondence information shown in Figure 11 and the calculated value calculated in steps S2 to S5. For example, if the calculated value is calculated to be -0.5, referring to the arrival direction correspondence information, it is found that the arrival direction is approximately 27 degrees. In this way, even if noise is superimposed on the output of the surface current sensor 300 and causes variations in the calculated value, it is possible to reduce the estimation error in the arrival direction of the surface current.

[0089] The arrival direction correspondence information used in estimating the arrival direction of the surface current is acquired in advance by a calibration test or the like. Here, the criterion for calculating the output voltage difference between the two signal terminals 4 based on whether the clockwise or counterclockwise arrangement direction of the signal terminals 4 is considered positive when acquiring the arrival direction correspondence information must be the same as the criterion for calculating the calculated values ​​in steps S2 to S5. If the calculated value was calculated based on the clockwise arrangement direction of the signal terminals 4 being positive in the calibration test performed when acquiring the arrival direction correspondence information, the calculated value should also be calculated based on the clockwise arrangement direction of the signal terminals 4 being positive when calculating the calculated value in steps S2 to S5.

[0090] The arrival direction correspondence information acquired in advance may be stored in a storage unit, etc. The storage unit may be provided in the partial discharge detection device 200 or may be located outside the partial discharge detection device 200.

[0091] The internal discharge determination circuit 27 determines whether or not a partial discharge has occurred inside the electric power device 100 based on the direction of arrival of the surface current estimated by the direction of arrival estimation circuit 26 .

[0092] The internal discharge determination circuit 27 determines whether or not a partial discharge has occurred inside the electric power equipment 100 based on the determination result of whether or not a surface current has occurred determined by the surface current detection circuit 25 and the estimation result of the direction of arrival of the surface current estimated by the direction of arrival estimation circuit 26.

[0093] Specifically, the internal discharge determination circuit 27 compares a preset range of the arrival direction of the surface current due to partial discharge inside the electric power equipment 100 to be inspected with the estimation result of the arrival direction of the surface current estimated by the arrival direction estimation circuit 26. If the arrival direction of the surface current estimated by the arrival direction estimation circuit 26 is within the preset range of arrival directions of the surface current and the determination result of the surface current detection circuit 25 indicates the occurrence of a surface current, the internal discharge determination circuit 27 determines that a partial discharge has occurred inside the electric power equipment 100. If such a determination result is obtained, it can be estimated that, for example, poor electrical insulation has occurred inside the electric power equipment 100.

[0094] The predetermined range of the direction of arrival of the surface current is determined based on the positions of the electrical openings of the electric power device 100 and the positions of the surface current sensors 300, and the determined range of the direction of arrival is preferably stored in a memory unit. The determination result of the internal discharge determination circuit 27 is also stored in a memory unit. In this way, by comparing the predetermined range of the direction of arrival of the surface current with the estimation result of the direction of arrival of the surface current estimated by the direction of arrival estimation circuit 26, it is possible to prevent erroneous determination by determining the presence or absence of a partial discharge inside the electric power device 100.

[0095] The display unit 500 receives the determination results of the surface current detection circuit 25 and the internal discharge determination circuit 27 in the arithmetic processing unit 400 and displays them on a display. If necessary, it also issues an alarm signal indicating that an electrical insulation defect has occurred inside the electric power device 100. The display unit 500 may be an information processing terminal such as a PC (personal computer).

[0096] In addition, Figure 9 shows an example in which the surface current detection circuit 25, the arrival direction estimation circuit 26, and the internal discharge determination circuit 27 are provided inside the calculation processing unit 400, but this is not limited to this, and the processing performed in the surface current detection circuit 25, the arrival direction estimation circuit 26, and the internal discharge determination circuit 27 may be performed inside the display unit 500.

[0097] As described above, the partial discharge detection device 200 according to this embodiment includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of the surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates the correspondence between the calculated value and the arrival direction of the surface current, which has been acquired in advance. With this configuration, even when noise is superimposed on the output of the surface current sensor 300 and causes variations in the calculated value, it is possible to reduce estimation errors in the arrival direction of the surface current and improve estimation accuracy.

[0098] The partial discharge detection method according to the present embodiment also includes the steps of: calculating a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal; and estimating the direction of arrival of the surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates the correspondence relationship between the calculated value and the direction of arrival of the surface current, which has been acquired in advance. With this configuration, even when noise is superimposed on the output of the surface current sensor 300 and causes variations in the calculated value, it is possible to reduce estimation errors in the direction of arrival of the surface current and improve estimation accuracy.

[0099] Embodiment 2 This embodiment will be described with reference to Fig. 12 to Fig. 14. Fig. 12 is a configuration diagram of a partial discharge detection system according to this embodiment. Fig. 13 is a cross-sectional view of a partial discharge detection device according to this embodiment. Fig. 14 is a configuration diagram of a calculation processing unit of the partial discharge detection device according to this embodiment.

[0100] In the first embodiment, the partial discharge detection device 200 is shown, which includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of a surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that shows the correspondence between the calculated value and the arrival direction of the surface current, which has been acquired in advance. In the second embodiment, the partial discharge detection device 201 is shown, in which a calibrator 40 is disposed on the surface of the housing of the electric power device 100 and a sensitivity calibration circuit 28 is newly provided in the calculation processing unit 400. Other configurations are the same as in the first embodiment, and the same components as in the first embodiment are assigned the same numbers and description thereof will be omitted.

[0101] 12, a partial discharge detection system 1001 according to this embodiment is composed of an electric power device 100 and a partial discharge detection device 201. The partial discharge detection system 1001 includes the partial discharge detection device 201 that detects the presence or absence of internal discharge, and the electric power device 100 having the partial discharge detection device 201 arranged on the surface of the housing.

[0102] The partial discharge detection device 201 in this embodiment includes a surface current sensor 300, a calculation processing unit 401, a display unit 500, and a calibrator 40. The calibrator 40 is disposed on the surface of the housing of the electric power device 100.

[0103] As in the first embodiment, the partial discharge detection device 201 in the present embodiment includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the centers of the signal terminals 4 excluding the maximum output terminal and the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of the surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates the correspondence between the calculated value and the arrival direction of the surface current obtained in advance. With this configuration, even when noise is superimposed on the output of the surface current sensor 300 and causes variations in the calculated value, it is possible to reduce estimation errors in the arrival direction of the surface current and improve estimation accuracy.

[0104] Next, the calibrator 40 of the partial discharge detection device 201 according to this embodiment will be described.

[0105] 13 is a cross-sectional view of the surface current sensor 300 and the calibrator 40 provided on the surface of the housing of the electric power device 100. As shown in FIG. 13, the calibrator 40 includes an AC voltage source 41 and a ground electrode 42.

[0106] One end of the AC voltage source 41 is connected to the upper electrode 1 of the surface current sensor 300, and the other end is connected to the ground electrode 42. The AC voltage source 41 applies a voltage between the upper electrode 1 and the ground electrode 42 of the surface current sensor 300. The oscillation frequency of the AC voltage source 41 is not particularly important, but it is desirable that the frequency be the same as that of the electromagnetic field caused by partial discharge, for example, within the range of 10 MHz to 10 GHz.

[0107] Furthermore, at least one AC voltage source 41 may be provided on the surface of the housing of the power device 100, but this is not limitative and multiple AC voltage sources 41 may be provided. By providing multiple AC voltage sources 41, the output sensitivity of the surface current sensor 300 can be calibrated with higher accuracy.

[0108] The ground electrode 42 is provided on the surface of the housing of the electric power device 100. When providing the ground electrode on the surface of the housing of the electric power device 100, it is desirable to provide it in close contact with the housing of the electric power device 100 so as to be electrically conductive. If the housing of the electric power device 100 is covered with a coating or the like, making electrical conductivity difficult, it is advisable to select a location with few irregularities and provide the ground electrode in close contact with the surface of the housing of the electric power device 100.

[0109] It is also preferable to make the ground area of ​​the ground electrode 42 larger than the ground area of ​​the lower electrode 2 of the surface current sensor 300. This makes it possible to reduce measurement errors caused by unevenness on the surface of the housing of the electric power device 100.

[0110] 14 is a configuration diagram of a processing unit 401 of a partial discharge detection device 201 according to this embodiment. The processing unit 401 is the processing unit 400 of the first embodiment, to which a sensitivity calibration circuit 28 is newly added.

[0111] The sensitivity calibration circuit 28 calibrates the output sensitivity of the surface current sensor 300 from the output voltage due to the surface current generated by the AC voltage source 41 of the calibrator 40. Specifically, the sensitivity calibration circuit 28 calibrates the fluctuation in the output sensitivity to the electric field component corresponding to the inclination of the surface current sensor 300 from the output of each signal terminal 4 provided on the surface current sensor 300 when the AC voltage source 41 applies a voltage between the upper electrode 1 and the ground electrode 42 of the surface current sensor 300. Here, the inclination of the surface current sensor 300 refers to the inclination of the surface current sensor 300 due to the unevenness on the housing surface of the electric power equipment 100.

[0112] The processing by the sensitivity calibration circuit 28 of the partial discharge detection device 201 in this embodiment is referred to as step S7. In step S7, the sensitivity calibration circuit 28 calibrates the fluctuation in output sensitivity to the electric field component corresponding to the inclination of the surface current sensor 300 from the output of each signal terminal 4 when the AC voltage source 41 applies a voltage to the surface current sensor 300. After the output sensitivity of the surface current sensor 300 is calibrated in step S7, the process proceeds to steps S1 to S6, which are steps in the processing flow by the direction-of-arrival estimation circuit 26 shown in Figure 10. Note that steps S1 to S6 are the same as those in embodiment 1, and therefore description thereof will be omitted.

[0113] As described above, the partial discharge detection device 201 according to this embodiment has the calibrator 40 disposed on the surface of the housing of the electric power equipment 100, and the calculation processing unit 401 includes the sensitivity calibration circuit 28 that calibrates the output sensitivity of the surface current sensor 300. With this configuration, even when noise is superimposed on the output of the surface current sensor 300, causing variations in the calculated values, it is possible to reduce errors in estimating the direction of arrival of the surface current and improve the estimation accuracy. Furthermore, even when the surface of the housing of the electric power equipment 100 is uneven and the surface current sensor 300 is tilted, the sensitivity calibration circuit 28 calibrates the output sensitivity of the surface current sensor 300, so that the direction of arrival of the surface current can be estimated without degrading the estimation accuracy.

[0114] Embodiment 3 This embodiment will be described with reference to Fig. 15 to Fig. 17. Fig. 15 is a configuration diagram of a partial discharge detection system according to this embodiment. Fig. 16 is a partial schematic diagram of a partial discharge detection device according to this embodiment. Fig. 17 is a configuration diagram of an arithmetic processing unit of the partial discharge detection device according to this embodiment.

[0115] In the first embodiment, the partial discharge detection device 200 is shown, which includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of a surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates a correspondence relationship between the calculated value and the arrival direction of the surface current, which has been acquired in advance. In the third embodiment, the partial discharge detection device 202 is shown, which includes a plurality of surface current sensors 300 arranged on the surface of the housing of the electric power device 100 and a calculation processing unit 402 that is newly provided with a two-dimensional discharge occurrence position identification circuit 29. Other configurations are the same as those in the first embodiment, and the same components as those in the first embodiment are assigned the same numbers, and descriptions thereof will be omitted.

[0116] 15, a partial discharge detection system 1002 according to this embodiment is composed of an electric power device 100 and a partial discharge detection device 202. The partial discharge detection system 1002 includes the partial discharge detection device 202 that detects the presence or absence of internal discharge, and the electric power device 100 having the partial discharge detection device 202 disposed on the surface of the housing.

[0117] The partial discharge detection device 202 in this embodiment includes two or more surface current sensors 300 , a calculation processing unit 402 , and a display unit 500 .

[0118] As in the first embodiment, the partial discharge detection device 202 in the present embodiment includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the centers of the signal terminals 4 excluding the maximum output terminal and the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of the surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates the correspondence between the calculated value and the arrival direction of the surface current obtained in advance. With this configuration, even when noise is superimposed on the output of the surface current sensor 300 and causes variations in the calculated value, it is possible to reduce estimation errors in the arrival direction of the surface current and improve estimation accuracy.

[0119] Next, the arithmetic processing unit 402 of the partial discharge detection device 202 according to this embodiment will be described with reference to Figs. 16 and 17. Fig. 16 is a partial schematic diagram of the partial discharge detection device according to this embodiment. Fig. 17 is a configuration diagram of the arithmetic processing unit 402 of the partial discharge detection device 202 according to this embodiment. Note that Fig. 16 indicates the location of partial discharge occurrence with a cross. Here, the location of partial discharge occurrence refers to the location where electromagnetic waves, etc., generated due to partial discharge inside the electric power equipment 100 have leaked out onto the surface of the housing of the electric power equipment 100 through an electrical opening.

[0120] As shown in Fig. 16, two surface current sensors 300 are provided on the surface of the housing of the electric power device 100 of the partial discharge detection system 1002 according to this embodiment. Note that, although Fig. 16 shows two surface current sensors, 300a and 300b, as an example, the number of surface current sensors 300 is not limited as long as it is two or more.

[0121] The calculation processing unit 402 of the partial discharge detection device 202 according to this embodiment is newly provided with a two-dimensional discharge occurrence position specifying circuit 29 as shown in Fig. 17. The two-dimensional discharge occurrence position specifying circuit 29 calculates and specifies the occurrence position of a partial discharge based on the estimated arrival direction of the surface currents input from the arrival direction estimation circuit 26.

[0122] A method for identifying the location of a partial discharge in the two-dimensional discharge occurrence location identifying circuit 29 will be described in detail using Figure 16. As shown in Figure 16, the surface of the housing of the electric power device 100 is defined as an xy plane, the origin is the center of the lower electrode 2 of each of the two surface current sensors 300a and 300b, D is the distance between the two surface current sensors 300a and 300b, and θ1 and θ2 are the estimated directions estimated by the direction-of-arrival estimation circuit 26. The two-dimensional discharge occurrence location identifying circuit 29 calculates and identifies the location of a partial discharge using the estimated results of the direction of arrival of the surface current, i.e., θ1 and θ2, input from the direction-of-arrival estimation circuit 26, using the following equations (6) and (7). Here, the x-coordinate of the location of the partial discharge occurrence is defined as xd and the y-coordinate is defined as yd.

[0123] (Math. 6) xd=D*(tan(θ1)+tan(θ2)) / (2*(tan(θ1)−tan(θ2)) Equation (6)

[0124] (Math. 7) yd=D / (tan(θ1)−tan(θ2)) Equation (7)

[0125] In this way, the two-dimensional discharge occurrence position identification circuit 29 calculates the occurrence position of the partial discharge and outputs the discharge occurrence position estimation result using the arrival direction estimation results of the surface currents input from the arrival direction estimation circuit 26. Therefore, it is possible to identify the position on the housing surface of the electric power device 100 where the partial discharge is occurring.

[0126] As described above, the partial discharge detection device 202 according to this embodiment has a plurality of surface current sensors 300 arranged on the surface of the housing of the electric power equipment 100, and the calculation processing unit 402 includes a two-dimensional discharge occurrence position identification circuit 29. With this configuration, even when noise is superimposed on the output of the surface current sensor 300, causing variations in the calculated values, it is possible to reduce errors in estimating the direction of arrival of the surface current and improve estimation accuracy. In addition, it is possible to identify the location of partial discharge occurrence on the surface of the housing of the electric power equipment 100, which can be utilized for maintenance of the electric power equipment 100.

[0127] In the partial discharge detection device 202 according to this embodiment, an example has been shown in which two surface current sensors 300 are arranged on the surface of the housing of the electric power equipment 100, but if there are three or more surface current sensors 300, it is preferable to arbitrarily select two surface current sensors 300 and perform the method described in this embodiment. This makes it possible to identify the location of partial discharge occurrence in the same way as when two surface current sensors 300 are arranged on the surface of the housing of the electric power equipment 100.

[0128] Embodiment 4 This embodiment will be described with reference to Fig. 18 to Fig. 20. Fig. 18 is a configuration diagram of a partial discharge detection system according to this embodiment. Fig. 19 is a partial schematic diagram of a partial discharge detection device according to this embodiment. Fig. 20 is a configuration diagram of an arithmetic processing unit of the partial discharge detection device according to this embodiment.

[0129] In the first embodiment, the partial discharge detection device 200 is shown, which includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the signal terminals 4 other than the maximum output terminal and the center of the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of a surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates the correspondence between the calculated value and the arrival direction of the surface current, which has been acquired in advance. In the fourth embodiment, the partial discharge detection device 203 is shown, which includes two or more surface current sensors 300 arranged on the surface of the housing of the electric power device 100, and a calculation processing unit 403 that is newly provided with an estimated time difference calculation circuit 30 and a three-dimensional discharge occurrence position identification circuit 31. Other configurations are the same as those in the first embodiment, and the same components as those in the first embodiment are assigned the same numbers, and descriptions thereof will be omitted.

[0130] 18, a partial discharge detection system 1003 according to this embodiment is composed of an electric power device 100 and a partial discharge detection device 203. The partial discharge detection system 1003 includes the partial discharge detection device 203 that detects the presence or absence of internal discharge, and the electric power device 100 with the partial discharge detection device 203 arranged on the surface of the housing.

[0131] The partial discharge detection device 203 in this embodiment includes two or more surface current sensors 300 , a calculation processing unit 403 , and a display unit 500 .

[0132] As in the first embodiment, the partial discharge detection device 203 in the present embodiment includes an arrival direction estimation circuit 26 that calculates a calculated value by dividing the difference in output voltages of two signal terminals 4 that are closest to positions where the angles formed by a line connecting the maximum output terminal, which is the signal terminal 4 with the highest output voltage, and the center of the lower electrode 2 and a line connecting the signal terminals 4 excluding the maximum output terminal and the center of the lower electrode 2 are 90 degrees and −90 degrees, respectively, by the output voltage of the maximum output terminal, and estimates the arrival direction of the surface current generated on the surface of the housing of the electric power device 100 using arrival direction correspondence information that indicates the correspondence between the calculated value and the arrival direction of the surface current, which has been acquired in advance. With this configuration, even when noise is superimposed on the output of the surface current sensor 300 and causes variations in the calculated value, it is possible to reduce estimation errors in the arrival direction of the surface current and improve estimation accuracy.

[0133] Next, the arithmetic processing unit 403 of the partial discharge detection device 203 according to this embodiment will be described with reference to Fig. 19 and Fig. 20. Fig. 19 is a partial schematic diagram of the partial discharge detection device according to this embodiment. Fig. 20 is a configuration diagram of the arithmetic processing unit 403 of the partial discharge detection device 203 according to this embodiment. Note that Fig. 19 indicates the location of partial discharge occurrence with a cross. Here, the location of partial discharge occurrence refers to the location where electromagnetic waves, etc., generated due to partial discharge inside the electric power equipment 100 have leaked out onto the surface of the housing of the electric power equipment 100 through an electrical opening.

[0134] As shown in Fig. 19, two surface current sensors 300 are provided on the surface of the housing of the electric power device 100 of the partial discharge detection system 1002 according to this embodiment. Note that, although Fig. 19 shows two surface current sensors, 300a and 300b, as an example, the number of surface current sensors 300 is not limited as long as it is two or more.

[0135] 20 , the calculation processing unit 403 of the partial discharge detection device 203 according to this embodiment newly includes an estimated time difference calculation circuit 30 and a three-dimensional discharge occurrence position identification circuit 31. The estimated time difference calculation circuit 30 calculates an estimated time difference from the time required for the arrival direction of each surface current to be estimated by the arrival direction estimation circuit 26. The estimated time difference calculation circuit 30 outputs the calculated estimated time difference to the three-dimensional discharge occurrence position identification circuit 31.

[0136] The three-dimensional discharge occurrence position identification circuit 31 calculates and identifies the occurrence position of the partial discharge using the estimated arrival direction results of the surface currents input from the arrival direction estimation circuit 26 and the estimated time difference input from the estimated time difference calculation circuit 30.

[0137] The method for identifying the location of a partial discharge in the three-dimensional discharge location identifying circuit 31 will be described in detail with reference to Fig. 19. As shown in Fig. 19, the surface of the housing of the electric power device 100 is defined as an xyz plane, the origin is the center of the lower electrode 2 of each of the two surface current sensors 300a and 300b, D is the distance between the two surface current sensors 300a and 300b, and θ1 and θ2 are the directions estimated by the direction-of-arrival estimation circuit 26, respectively.

[0138] The three-dimensional discharge occurrence position identification circuit 31 uses the estimated surface current arrival direction results θ1 and θ2 input from the arrival direction estimation circuit 26 and the estimated time difference input from the estimated time difference calculation circuit 30 to calculate and identify the occurrence position of the partial discharge using the following equations (8) to (10). Here, the x-coordinate of the partial discharge occurrence position is defined as xd, the y-coordinate as yd, and the z-coordinate as zd. Furthermore, the estimated time difference calculated by the estimated time difference calculation circuit 30 is defined as td, and the propagation speed of the electromagnetic wave is defined as c.

[0139] (Math. 8) xd=D*(tan(θ1)+tan(θ2)) / (2*(tan(θ1)−tan(θ2)) Equation (8)

[0140] (Equation 9) yd=D / (tan(θ1)−tan(θ2)) Equation (9)

[0141] (Math. 10) c*td=(zd^2+(yd / sin(θ1))^2)^0.5-(zd^2+(yd / sin(θ2))^2)^0.5 Formula (10)

[0142] In this way, the three-dimensional discharge occurrence position identification circuit 31 calculates the occurrence position of the partial discharge using the estimated arrival direction of the surface current and the estimated time difference, and outputs the discharge occurrence position estimation result. Therefore, compared to the partial discharge detection device 202 according to the third embodiment, the partial discharge detection device 203 according to this embodiment can calculate up to the z coordinate, and therefore can identify the occurrence position of the partial discharge more accurately.

[0143] As described above, the partial discharge detection device 203 according to this embodiment has a plurality of surface current sensors 300 arranged on the surface of the housing of the electric power equipment 100, and the calculation processing unit 403 includes an estimated time difference calculation circuit 30 and a three-dimensional discharge occurrence position identification circuit 31. With this configuration, even when noise is superimposed on the output of the surface current sensor 300, causing variations in the calculated values, it is possible to reduce the estimation error in the direction of arrival of the surface current and improve the estimation accuracy. In addition, it is possible to identify the location of partial discharge occurrence in three dimensions, which can be utilized for the maintenance of the electric power equipment 100.

[0144] In the partial discharge detection device 203 according to this embodiment, an example has been shown in which two surface current sensors 300 are arranged on the surface of the housing of the electric power equipment 100, but if there are three or more surface current sensors 300, it is preferable to arbitrarily select two surface current sensors 300 and perform the method described in this embodiment. This makes it possible to identify the location of partial discharge occurrence in the same way as when two surface current sensors 300 are arranged on the surface of the housing of the electric power equipment 100.

[0145] REFERENCE SIGNS LIST 1 Upper electrode, 2 Lower electrode, 3 Insulating spacer, 4, 4a, 4b, 4c, 4d Signal terminal, 5, 5a, 5b, 5c, 5d Cable, 6 Core wire, 7, 7a, 7c Bonding wire, 10 Processor, 11 Memory, 12 Display, 13 Input interface, 21 Protection circuit, 22 Filter, 23 Signal amplifier circuit, 24 A / D converter, 25 Surface current detection circuit, 26 Direction of arrival estimation circuit, 27 Internal discharge determination circuit, 28 Sensitivity calibration circuit, 29 Two-dimensional discharge occurrence location identification circuit, 30 Estimated time difference calculation circuit, 31 Three-dimensional discharge occurrence location identification circuit, 40 Calibrator, 41 AC voltage source, 42 Ground electrode, 100 Power equipment, 200, 201, 202, 203 Partial discharge detection device, 300, 300a, 300b Surface current sensor, 400, 401, 402, 403 Processing unit, 500 Display unit, 1000, 1001, 1002, 1003 Partial discharge detection system

Claims

1. a surface current sensor disposed on a surface of a housing of the electric power device, the surface current sensor having an upper electrode, a lower electrode provided in the vicinity of the surface of a housing of the electric power device, an insulating spacer provided between the upper electrode and the lower electrode, and three or more signal terminals provided on the lower electrode, the signal terminals being connected to the upper electrode via bonding wires; a surface current detection circuit that determines whether or not a surface current is generated on a surface of a housing of the electric power device based on the intensity of the signal output of the signal terminal; an arrival direction estimation circuit that calculates a calculation value by dividing an output voltage difference between two of the signal terminals that are closest to a position where an angle between a line connecting a maximum output terminal, which is the signal terminal having the maximum output voltage, and the center of the lower electrode and a line connecting the signal terminals other than the maximum output terminal and the center of the lower electrode is 90 degrees and -90 degrees, respectively, by an output voltage of the maximum output terminal, and estimates the arrival direction of the surface current generated on the surface of a housing of the electric power device using arrival direction correspondence information that indicates a correspondence relationship between the calculation value obtained in advance and the arrival direction of the surface current and the calculated calculation value; an internal discharge determination circuit that determines whether or not a partial discharge exists inside the electric power device based on a determination result of the surface current detection circuit and an estimation result of the direction of arrival estimation circuit; A partial discharge detection device comprising:

2. 2. The partial discharge detection device according to claim 1, wherein the signal terminals of the surface current sensor are provided at equal intervals in an arrangement direction in which adjacent signal terminals are located on the lower electrode.

3. 2. The partial discharge detection device according to claim 1, wherein the surface current sensor is in the shape of a quadrangular prism with the four signal terminals provided at the four corners of the lower electrode.

4. 4. The partial discharge detection device according to claim 3, wherein the surface current sensor is cubic in shape.

5. The partial discharge detection device according to claim 1 , wherein the surface current sensor is disposed on a surface of a housing of the electric power device near an electrical opening.

6. 2. The partial discharge detection device according to claim 1, wherein the insulating spacer of the surface current sensor is provided with a part cut out.

7. 2. The partial discharge detection device according to claim 1, wherein the internal discharge determination circuit compares a preset range of the arrival direction of the surface current with the estimation result of the arrival direction estimation circuit to determine the presence or absence of a partial discharge inside the electric power equipment.

8. a calibrator disposed on a surface of a housing of the electric power device, the calibrator including an AC voltage source connected to the upper electrode and a ground electrode provided on the surface of a housing of the electric power device; a sensitivity calibration circuit that calibrates an output sensitivity of the surface current sensor from the output voltage due to the surface current generated by the AC voltage source of the calibrator; The partial discharge detection device according to claim 1 .

9. The partial discharge detection device according to claim 8 , wherein the grounding area of ​​the calibrator is larger than the grounding area of ​​the lower electrode of the surface current sensor.

10. The partial discharge detection device according to claim 1, further comprising a two-dimensional discharge occurrence location identification circuit that identifies the occurrence location of the partial discharge based on the surface current arrival direction estimation results of the surface currents estimated by the arrival direction estimation circuit, wherein the surface current sensors are arranged in plurality on the surface current housing surface of the electric power equipment.

11. 2. The partial discharge detection device according to claim 1, further comprising: a plurality of surface current sensors arranged on a surface of a housing of the electric power equipment; an estimated time difference calculation circuit that calculates an estimated time difference from the time required for each of the direction of arrival estimation circuits to estimate the direction of arrival of the surface current; and a three-dimensional discharge occurrence position identification circuit that identifies the occurrence position of the partial discharge using the surface current arrival direction estimation results estimated by each of the direction of arrival estimation circuits and the estimated time difference calculated by the estimated time difference calculation circuit.

12. determining whether or not a surface current has been generated on the surface of a housing of the electric power device based on the intensity of a signal output from a signal terminal provided on the surface current sensor; a step of calculating a calculated value by dividing an output voltage difference between two of the signal terminals that are closest to a position where an angle between a line connecting the center of the lower electrode and a maximum output terminal, which is the signal terminal having the maximum output voltage, and a line connecting the center of the lower electrode and the signal terminals other than the maximum output terminal is 90 degrees and -90 degrees, by an output voltage of the maximum output terminal, and estimating an arrival direction of the surface current generated on a housing surface of the electric power device using arrival direction correspondence information that indicates a correspondence relationship between the calculated value and the arrival direction of the surface current obtained in advance and the calculated calculated value; determining whether or not a partial discharge has occurred inside the electric power device based on a result of the determination in the step of determining whether or not a surface current has occurred and a result of the estimation in the step of estimating the direction of arrival of the surface current; A partial discharge detection method comprising:

13. The partial discharge detection device according to any one of claims 1 to 11, which detects the presence or absence of internal discharge; an electric power device having the partial discharge detection device disposed on a surface of a housing thereof; A partial discharge detection system comprising: