Inspection device and inspection method

Abstract

To provide an inspection device and inspection method, which enable appropriate partial discharge inspection..SOLUTION: An inspection device (1) is provided, comprising a voltage application unit (11) for applying an AC voltage amplitude-modulated to include an increase and decrease in peak voltage to a device, and a detection unit (151) for detecting partial discharge occurring in the device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inspection apparatus and an inspection method for inspecting partial discharge.

Background Art

[0002] Non-Patent Document 1 describes an inspection method for measuring the partial discharge start voltage and the partial discharge extinction voltage in a partial discharge test.

Prior Art Document

Non-Patent Document

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional inspection method, the determination of the partial discharge start voltage is performed by applying a continuous sinusoidal inspection voltage with a constant amplitude (constant peak voltage) to the device to be inspected for a predetermined period. If no partial discharge occurs, the amplitude is increased and the sinusoidal inspection voltage is applied to the device to be inspected again for a predetermined period. If partial discharge occurs, the amplitude of the inspection voltage applied at that time is specified as the partial discharge start voltage.

[0005] However, in the conventional inspection method, an inspection voltage with a certain amplitude at which partial discharge can occur is continuously applied for a certain period. Therefore, once partial discharge occurs during the inspection, partial discharge may continue to occur, which may damage the device to be inspected.

[0006] One aspect of the present invention aims to provide an inspection apparatus and an inspection method capable of appropriately inspecting partial discharge.

Means for Solving the Problems

[0007] To solve the above problems, an inspection apparatus according to one aspect of the present invention includes a voltage application unit that applies an alternating voltage whose amplitude is modulated so as to include an increase and a decrease in peak voltage to a device, and a detection unit that detects partial discharge generated in the device.

[0008] To solve the above problems, an inspection method according to one aspect of the present invention includes a voltage application step of applying an alternating voltage whose amplitude is modulated so as to include an increase and a decrease in peak voltage to a device, and a detection step of detecting partial discharge generated in the device.

Advantages of the Invention

[0009] According to one aspect of the present invention, it is possible to appropriately perform an inspection of partial discharge.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0011] Hereinafter, Embodiment 1 and Embodiment 2 embodying the present invention will be described in detail with reference to the drawings. The same or equivalent components and members shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0012] [Embodiment 1] [Configuration of Inspection Device 1] The configuration of the inspection device 1 according to Embodiment 1 of the present disclosure will be described with reference to FIG. 1. FIG. 1 is a block diagram showing the configuration of the main part of the inspection device 1 according to Embodiment 1. As shown in FIG. 1, the inspection device 1 includes a voltage application unit 11, an applied waveform acquisition unit 12, a partial discharge measurement unit 13, an A / D conversion unit 14, and a control unit 15. The control unit 15 includes a detection unit 151, a voltage specifying unit 152, a determination unit 153, and a notification unit 154.

[0013] The voltage application unit 11 applies, as an inspection voltage, an alternating voltage whose amplitude is modulated to include an increase and a decrease in the peak voltage, to the device to be inspected. Hereinafter, one period in which the amplitude of the peak voltage of the inspection voltage is modulated is referred to as "one modulation period". The voltage application unit 11 applies, to the device, an inspection voltage whose amplitude is modulated such that the peak voltage changes periodically. The device to be inspected includes, for example, an electrical element such as a capacitor, a transformer, a switch, or an electrical device including at least one electrical element. The voltage application unit 11 is composed of, for example, a function generator and a high-voltage amplifier.

[0014] The voltage application unit 11 generates an alternating voltage whose amplitude is modulated according to the frequency of the alternating voltage, the minimum peak voltage, the maximum peak voltage, the time from the minimum peak voltage to reach the maximum peak voltage, the time from the maximum peak voltage to reach the minimum peak voltage, one modulation period of the peak voltage, the number of repetitions of the inspection voltage, and the standby time until the next inspection voltage is applied, which are instructed from the control unit 15, and applies it to the device as an inspection voltage. Here, the peak voltage refers to the maximum value of the voltage on the positive side.

[0015] The Inca waveform acquisition unit 12 acquires the voltage waveform of the inspection voltage applied by the voltage application unit 11 to the device and outputs it to the A / D conversion unit 14.

[0016] The partial discharge measurement unit 13 measures a physical quantity indicating partial discharge (for example, a quantity corresponding to the charge flowing due to partial discharge or a pulse voltage generated by partial discharge) generated in the device to which the inspection voltage is applied. For example, the partial discharge measurement unit 13 detects the voltage waveform of the minute pulse voltage generated by the partial discharge of the device to which the inspection voltage is applied and outputs it to the A / D conversion unit 14. The partial discharge measurement unit 13 is composed of, for example, an amplifier and a high-pass filter that amplify the minute pulse voltage generated at the grounded terminal of the device. The high-pass filter allows, for example, components in a frequency band of 15 kHz or higher to pass through.

[0017] The A / D conversion unit 14 samples the analog voltage signal, which is the voltage waveform of the inspection voltage input from the applied waveform acquisition unit 12, at a predetermined sampling frequency and outputs it to the control unit 15 as time-series digital data of the inspection voltage. Also, the A / D conversion unit 14 samples the analog signal, which is the voltage waveform of the band-limited pulse voltage input from the partial discharge measurement unit 13, at a predetermined sampling frequency and outputs it to the control unit 15 as time-series digital data of the pulse voltage due to partial discharge.

[0018] The control unit 15 comprehensively controls each unit. The control unit 15 is composed of, for example, a personal computer or the like. The control unit 15 outputs, to the voltage application unit 11, the frequency of the alternating voltage, the minimum peak voltage, the maximum peak voltage, the time from the minimum peak voltage to reaching the maximum peak voltage, the time from the maximum peak voltage to reaching the minimum peak voltage, the time of one modulation period of the peak voltage, the number of repetitions, and the standby time until the next inspection voltage is applied, which specify the voltage waveform of the inspection voltage. The control unit 15 sets the voltage waveform of the inspection voltage in one modulation period, the period during which the inspection voltage is applied, and the standby time until the next inspection voltage is applied.

[0019] The detection unit 151 detects partial discharges generated in the device based on the time-series digital data of the pulse voltage due to partial discharges input from the A / D conversion unit 14. For example, when the time-series digital data of the pulse voltage due to partial discharges is equal to or higher than a predetermined pulse voltage threshold, the detection unit 151 determines that a partial discharge has occurred in the device. Alternatively, the detection unit 151 calculates the partial discharge charge amount based on the time-series digital data of the pulse voltage due to partial discharges input from the A / D conversion unit 14, and when the partial discharge charge amount is equal to or higher than a predetermined charge amount threshold, determines that a partial discharge has occurred in the capacitor. Note that the predetermined pulse voltage threshold and the predetermined charge amount threshold are stored in advance in a storage unit (not shown) of the control unit 15.

[0020] The voltage specifying unit 152 specifies the partial discharge start voltage from the maximum peak voltage of the inspection voltage when a partial discharge is detected in the device. For example, based on the time-series digital data of the inspection voltage input from the A / D conversion unit 14, the voltage specifying unit 152 specifies the maximum peak voltage of the inspection voltage when a partial discharge is detected in the device as the partial discharge start voltage and stores it in a storage unit (not shown).

[0021] The determination unit 153 determines whether partial discharges continue to occur during a period in which the peak voltage of the inspection voltage gradually decreases from the maximum peak voltage, based on the time-series digital data of the inspection voltage and the pulse voltage due to partial discharges input from the A / D conversion unit 14. That is, the determination unit 153 determines whether partial discharges continuously occur near the minimum peak voltage during a period in which the peak voltage of the inspection voltage gradually decreases from the maximum peak voltage. Then, the determination unit 153 determines the quality of the device based on whether partial discharges continue to occur during a period in which the peak voltage of the inspection voltage gradually decreases from the maximum peak voltage.

[0022] The notification unit 154 notifies the user that partial discharge of the device has been detected via the detection unit 151. Further, when partial discharge of the device is detected, the notification unit 154 notifies the user of the partial discharge start voltage specified by the voltage specification unit 152. Further, when partial discharge continuously occurs during a period in which the peak voltage of the inspection voltage gradually decreases from the maximum peak voltage, the notification unit 154 notifies the user of the quality of the device determined by the determination unit 153. As a method of notifying the user, the notification unit 154 may be performed by any method such as displaying on a display (not shown). For example, the notification unit 154 may display the voltage waveform of the inspection voltage and the pulse voltage of the partial discharge on a display (not shown) in an overlapping manner.

[0023] [Partial discharge detection process] Next, a partial discharge detection process for detecting partial discharge occurring in a device executed by the control unit 15 of the inspection apparatus 1 configured as described above will be described with reference to FIGS. 2 to 6. FIG. 2 is a flowchart showing an example of the operation of the partial discharge test of the inspection apparatus 1. Note that the device to which the inspection voltage is applied is assumed to be a capacitor as an example.

[0024] As shown in FIG. 2, in step S11, the control unit 15 performs initial settings. Specifically, the control unit 15 reads out the frequency of the AC voltage constituting the inspection voltage whose peak voltage changes periodically, the minimum peak voltage, the maximum peak voltage, the time from the minimum peak voltage to reach the maximum peak voltage, the time from the maximum peak voltage to reach the minimum peak voltage, the time for one modulation period of the peak voltage, the number of repetitions of the inspection voltage, and the standby time until the next inspection voltage is applied from a storage unit (not shown), and outputs it to the voltage application unit 11. Thereafter, the control unit 15 proceeds to the process of step S12.

[0025] As a result, the voltage application unit 11 performs an initial setting of the inspection voltage for one modulation period based on the frequency of the alternating voltage, the minimum peak voltage, the maximum peak voltage, the time from the minimum peak voltage to reach the maximum peak voltage, the time from the maximum peak voltage to reach the minimum peak voltage, and the time for one modulation period of the peak voltage input from the control unit 15. Note that the minimum peak voltage may be equal to or less than half of the maximum peak voltage.

[0026] Here, an example of the inspection voltage will be described with reference to FIG. 3. FIG. 3 is a diagram showing an example of one modulation period of the inspection voltage. Here, the frequency 50 [Hz] that is the basis of the alternating voltage is called the fundamental frequency, its period is called the fundamental period, and the time 400 [ms] for one modulation period of the peak voltage that changes periodically is called the modulation period. As shown in FIG. 3, the inspection voltage 21 includes waveforms in a period where the peak voltage gradually increases and a period where it gradually decreases in one modulation period. For example, in the period where the peak voltage gradually increases, the envelope of the peak voltage may increase linearly, and in the period where the peak voltage gradually decreases, the envelope of the peak voltage may decrease linearly. For example, over a time of at least twice the fundamental period, the peak voltage gradually increases by at least twice, or gradually decreases to less than half.

[0027] As shown in FIG. 2, in step S12, after the control unit 15 instructs the voltage application unit 11 to apply the inspection voltage, the process proceeds to the process of step S13. As a result, the voltage application unit 11 applies the inspection voltage to the capacitor, which is the device, the number of times of "repetition of the inspection voltage" input in step S11.

[0028] Here, an example of applying the inspection voltage at the initial setting will be described based on the inspection voltage 22 shown in the upper part of FIG. 4. FIG. 4 is a diagram showing an example in which the maximum peak voltage is boosted after applying the inspection voltage 22 at the initial setting. In step S11, the control unit 15 outputs, to the voltage application unit 11, a frequency of the alternating voltage of 50 [Hz], a minimum peak voltage of 0.1 [kV], a maximum peak voltage of 5 [kV], a time from the minimum peak voltage to reach the maximum peak voltage of 200 [ms], a time from the maximum peak voltage to reach the minimum peak voltage of 200 [ms], a time for one modulation period of the peak voltage of 400 [ms], and the number of repetitions of the inspection voltage of 3 [times].

[0029] Also, the control unit 15 outputs, to the voltage application unit 11, for example, 0.4 [s] as a standby time until the next inspection voltage is applied. Note that the number of repetitions of the inspection voltage may be 3 or more. For example, the number of repetitions of the inspection voltage may be 4 to 10 times. The number of repetitions of the inspection voltage may be 1 to 2 times or 11 or more times. By applying the inspection voltage over a plurality of modulation periods, stable partial discharge detection results can be obtained.

[0030] As shown in the upper part of FIG. 4, in the inspection voltage 22, from 0 [ms] to 200 [ms] within one modulation period, the peak voltage of 50 [Hz] gradually increases from 0.1 [kV] to reach 5 [kV]. Then, in the inspection voltage 22, from 200 [ms] to 400 [ms], the peak voltage of 50 [Hz] gradually decreases from 5 [kV] to reach 0.1 [kV]. And the inspection voltage 22 is applied repeatedly 3 times.

[0031] As shown in FIG. 2, in step S13, the control unit 15 determines whether or not partial discharge generated in the capacitor as a device is detected via the detection unit 151. If the control unit 15 determines that no partial discharge generated in the capacitor as a device is detected via the detection unit 151 (S13: NO), the process proceeds to the process of step S14.

[0032] In step S14, the control unit 15 determines whether the maximum peak voltage of the inspection voltage applied to the capacitor is equal to or higher than the voltage threshold. For example, the voltage threshold is 20 [kV]. The control unit 15 stores in a storage unit (not shown) in advance the voltage threshold of the maximum peak voltage. Then, when the control unit 15 determines that the maximum peak voltage of the inspection voltage applied to the capacitor is not equal to or higher than the voltage threshold (S14: NO), the process proceeds to the process of step S15.

[0033] In step S15, the control unit 15 increases the maximum peak voltage by a predetermined voltage, for example, 1 [kV] to 2 [kV], that is, after setting the inspection voltage increased, the control unit 15 executes again the processes after step S11. Specifically, the control unit 15 instructs the voltage application unit 11 to increase the peak voltage of the inspection voltage by 1 [kV] to 2 [kV], that is, to increase, and then executes again the processes after step S11. At this time, the control unit 15 may also change other parameters such as the minimum peak voltage, the time from the minimum peak voltage to reaching the maximum peak voltage, the time from the maximum peak voltage to reaching the minimum peak voltage, the time for one modulation period of the peak voltage, and the number of repetitions of the inspection voltage. For example, the control unit 15 may increase the maximum peak voltage and also increase the time for one modulation period of the peak voltage.

[0034] Here, an example of the inspection voltage obtained by increasing the maximum peak voltage at the time of initial setting by a predetermined voltage, for example, 2 [kV], will be described based on the inspection voltage 23 shown in the lower part of FIG. 4. The voltage application unit 11 waits for the "waiting time until the next inspection voltage is applied", for example, 0.4 [s], input in step S11 from the end of the application of the previous inspection voltage, and then applies the inspection voltage 23 to the device to be inspected.

[0035] As shown in the lower part of FIG. 4, during one modulation period, from 0 [ms] to 200 [ms], the inspection voltage 23 has a peak voltage of 50 [Hz] gradually increasing from 0.1 [kV] to reach 7 [kV]. Then, from 200 [ms] to 400 [ms], the inspection voltage 22 has a peak voltage of 50 [Hz] gradually decreasing from 7 [kV] to reach 0.1 [kV]. And the inspection voltage 23 is applied repeatedly 3 times (for 3 modulation periods).

[0036] On the other hand, as shown in FIG. 2, in step S14 above, when the control unit 15 determines that the maximum peak voltage of the inspection voltage applied to the capacitor is equal to or higher than the voltage threshold (S14: YES), it proceeds to the process of step S16. In step S16, the control unit 15 determines that the quality of the capacitor as a device is "A". That is, the control unit 15 determines that the capacitor as a device is a "good product" in which partial discharge has not occurred, stores the determination result in a storage unit (not shown), and then proceeds to the process of step S17.

[0037] In step S17, the control unit 15 notifies the user that there is "no partial discharge" via the notification unit 154, and then ends the partial discharge detection process. For example, the control unit 15 displays "No partial discharge. It is a good product." on a display (not shown) to notify the user that no partial discharge has occurred in the capacitor and it is a good product.

[0038] On the other hand, in step S13 above, when the control unit 15 determines that it has detected partial discharge occurring in the capacitor as a device via the detection unit 151 (S13: YES), it proceeds to the process of step S18. In step S18, the control unit 15 specifies, via the voltage specifying unit 152, the maximum peak voltage of the inspection voltage applied in step S12 as the partial discharge start voltage, stores it in a storage unit (not shown) as the partial discharge start voltage, and then proceeds to the process of step S19.

[0039] Here, an example of partial discharge occurring in the capacitor will be described with reference to FIG. 5. FIG. 5 is a diagram showing an example where the partial discharge does not continue. As shown in FIG. 5, during the period when the maximum peak voltage of the test voltage 25 gradually decreases from 8.3 [kV], partial discharges 26A to 26E of 1.0 [nC] or more, which is the charge threshold, occur at the maximum peak voltage of 8.3 [kV] and the second highest peak voltage of 7.7 [kV].

[0040] On the other hand, after the third highest peak voltage, the partial discharge has disappeared. That is, after the third highest peak voltage, the insulation between the electrodes of the capacitor is maintained. Therefore, the control unit 15 specifies 8.3 [kV] of the maximum peak voltage as the partial discharge start voltage via the voltage specifying unit 152 and stores it in a storage unit (not shown) as the partial discharge start voltage. Also, after the third highest peak voltage, since the partial discharge has disappeared, damage such as destruction of the capacitor dielectric due to the partial discharge can be prevented.

[0041] As shown in FIG. 2, in step S19, the control unit 15 determines, via the determination unit 153, whether or not the partial discharge occurring in the capacitor as a device continues to occur. That is, the control unit 15 determines, via the determination unit 153, whether or not the partial discharge continuously occurs up to near the minimum peak voltage during the period when the peak voltage of the test voltage gradually decreases from the maximum peak voltage.

[0042] Then, when the control unit 15 determines, via the determination unit 153, that the partial discharge occurring in the capacitor as a device does not continue to occur (S19: NO), the process proceeds to the process of step S20. For example, as shown in FIG. 5, when the partial discharge has disappeared after the third highest peak voltage of the test voltage 25, the determination unit 153 determines that the partial discharge occurring in the capacitor as a device does not continue to occur.

[0043] For example, if, within one modulation period, partial discharge occurs after a period exceeding a predetermined period from the occurrence of partial discharge, the determination unit 153 may determine that partial discharge is continuously occurring; if no partial discharge occurs, it may determine that partial discharge is not continuously occurring. The predetermined period may be obtained by multiplying the basic period by a predetermined coefficient. The predetermined period is shorter than half of the modulation period. Alternatively, during the period when the peak voltage is decreasing, if partial discharge occurs after exceeding a predetermined timing, the determination unit 153 may determine that partial discharge is continuously occurring; if no partial discharge occurs, it may determine that partial discharge is not continuously occurring. The predetermined timing is after the timing at which the maximum peak voltage is applied. For example, the predetermined timing may be at least one basic period after the timing at which the maximum peak voltage is applied. Note that partial discharge is likely to occur at the timing when the inspection voltage crosses zero. If partial discharge continuously occurs over several basic periods, even if there is a period when no partial discharge occurs, it can be regarded as "partial discharge is continuously occurring".

[0044] In step S20, the control unit 15 determines, via the determination unit 153, that the quality of the capacitor as a device is "B". That is, the control unit 15 determines, via the determination unit 153, that although partial discharge has occurred in the capacitor as a device, the oil, which is the dielectric between the electrodes, has not been decomposed and it is a usable product, stores the determination result in a storage unit (not shown), and then proceeds to the process of step S22.

[0045] In step S22, after the control unit 15 notifies the user, via the notification unit 154, of "partial discharge exists. The quality is B." and the partial discharge start voltage, the partial discharge detection process ends. For example, the control unit 15 displays on a display (not shown) "partial discharge exists. The quality is B. The partial discharge start voltage is 8.3 [kV]" to notify the user that partial discharge has occurred in the capacitor and the quality is "B", that is, it is a usable product.

[0046] On the other hand, in step S19, when the control unit 15 determines via the determination unit 153 that partial discharge has continuously occurred in the capacitor as a device (S19: YES), the process proceeds to the process of step S21.

[0047] Here, an example in which partial discharge continuously occurs in the capacitor will be described with reference to FIG. 6. FIG. 6 is a diagram showing an example in which partial discharge continuously occurs. As shown in FIG. 6, during the period in which the maximum peak voltage of the inspection voltage 25 gradually decreases from 8.3 [kV], partial discharges 27A to 27C with a charge amount threshold of 1.0 [nC] or more occur at the maximum peak voltage of 8.3 [kV] and the second highest peak voltage of 7.7 [kV].

[0048] Furthermore, after the third highest peak voltage, partial discharges 27D to 27I with a partial discharge charge amount of approximately 2.2 [nC] continuously occur up to the second lowest peak voltage for each of the peak voltages. That is, during the period in which the maximum peak voltage of the inspection voltage 25 gradually decreases from 8.3 [kV], partial discharges with a partial discharge charge amount of approximately 2.2 [nC] or more continuously occur from the maximum peak voltage to the second lowest peak voltage.

[0049] Therefore, the control unit 15 specifies 8.3 [kV] of the maximum peak voltage as the partial discharge start voltage via the voltage specifying unit 152 and stores it as the partial discharge start voltage in a storage unit (not shown).

[0050] As shown in FIG. 2, in step S21, the determination unit 153 determines that the quality of the capacitor as a device is "C". In a capacitor with oil encapsulated as the dielectric between the electrodes, the oil between the electrodes may be decomposed to generate gas due to excessive current, for example, partial discharge over a long period. When gas is generated, the dielectric strength decreases, and partial discharge continuously occurs through the bubbles even at a low voltage. Also, in a capacitor with bubbles present due to inappropriate oil encapsulation in the first place, partial discharge continuously occurs even at a low voltage. The determination unit 153 determines that the quality of such a capacitor is "C". That is, the determination unit 153 determines that the capacitor as a device is a defective product, stores the determination result in a storage unit (not shown), and then proceeds to the process of step S22.

[0051] In step S22, the control unit 15 notifies the user of "Partial discharge is continuously occurring. The quality is C." and the partial discharge start voltage via the notification unit 154, and then ends the partial discharge detection process. For example, the control unit 15 displays on a display (not shown) "Partial discharge is continuously occurring. The quality is C. The partial discharge start voltage is 8.3 [kV].", and notifies the user that partial discharge continuously occurs in the capacitor and the quality is "C", that is, it is a defective product.

[0052] In the conventional inspection method, a continuous sinusoidal inspection voltage with a constant amplitude is applied. In the conventional inspection voltage, when viewed over a long period, the peak voltage gradually increases until partial discharge occurs, but the peak voltage does not decrease. Also, the peak voltage is constant for a certain period and does not change periodically. Therefore, when the inspection voltage reaches the partial discharge start voltage of the device, partial discharge continuously occurs. The operation of detecting the occurrence of partial discharge and stopping the application of the inspection voltage cannot be performed immediately.

[0053] On the other hand, in the inspection apparatus 1 according to Embodiment 1, the control unit 15 applies an inspection voltage, whose peak voltage periodically and gradually increases within one modulation period to reach the maximum peak voltage and then gradually decreases, to the capacitor as a device a set number of times. Then, when the detection unit 151 does not detect partial discharge, the control unit 15 gradually raises the maximum peak voltage of the inspection voltage to confirm the occurrence of partial discharge at the next maximum peak voltage.

[0054] Thereby, after partial discharge occurs at the maximum peak voltage of the inspection voltage, the peak voltage gradually decreases and the partial discharge disappears, so that damage to the capacitor dielectric of the capacitor as a device can be prevented, and the inspection of partial discharge can be appropriately performed.

[0055] In addition, the control unit 15 can determine whether the partial discharge occurring in the capacitor occurs in oil or in the gas in which the oil is decomposed, depending on whether the partial discharge continuously occurs. The control unit 15 can discriminate a manufacturing defect of the capacitor. Thus, the control unit 15 can identify the cause of the occurrence of partial discharge according to the manner of occurrence of partial discharge.

[0056] [Embodiment 2] Next, the inspection apparatus 31 according to Embodiment 2 will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram showing an example of one modulation period of the second inspection voltage 33 according to Embodiment 2. FIG. 8 is a diagram showing an example in which the partial discharge generated by the second inspection voltage does not continue. For convenience of explanation, members having the same functions as the members described in Embodiment 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

[0057] The inspection apparatus 31 according to Embodiment 2 has substantially the same configuration as the inspection apparatus 1 according to Embodiment 1 and substantially the same control. However, the control unit 15 of the inspection apparatus 31 is different in that in step S11, instead of the inspection voltage according to Embodiment 1, a second inspection voltage whose peak voltage gradually decreases from the maximum peak voltage in one modulation period of the peak voltage is initially set.

[0058] Specifically, in step S11, the control unit 15 reads out from a storage unit (not shown) the frequency of the alternating voltage that constitutes the second inspection voltage whose peak voltage changes periodically, the maximum peak voltage at the start of application, the minimum peak voltage at the final application, the time for one modulation period from when the maximum peak voltage gradually decreases until it reaches the minimum peak voltage, the number of repetitions of the second inspection voltage, and the standby time until the next second inspection voltage is applied, and outputs the same to the voltage application unit 11. Thereafter, the control unit 15 proceeds to the process of step S12.

[0059] As a result, the voltage application unit 11 performs initial setting of the second inspection voltage for one modulation period based on the frequency of the alternating voltage input from the control unit 15, the maximum peak voltage at the start of application, the minimum peak voltage at the final application, and the time for one modulation period from when the maximum peak voltage gradually decreases until it reaches the minimum peak voltage. Note that the minimum peak voltage may be equal to or less than half of the maximum peak voltage.

[0060] Here, an example of the second inspection voltage will be described with reference to FIG. 7. As shown in FIG. 7, in the second inspection voltage 33, the frequency of the alternating voltage is 50 [Hz], the maximum peak voltage at the start of application is 15 [kV], the minimum peak voltage at the final application is 6 [kV], and the time for one modulation period from when the maximum peak voltage gradually decreases until it reaches the minimum peak voltage corresponds to 200 [ms]. Therefore, in the second inspection voltage 33, within one modulation period, from 0 [ms] to 200 [ms], the peak voltage of 50 [Hz] gradually decreases from 15 [kV] until it reaches 6 [kV].

[0061] Then, in step S12, after the control unit 15 instructs the voltage application unit 11 to apply the inspection voltage, the control unit 15 proceeds to the process of step S13. As a result, the voltage application unit 11 applies the second inspection voltage to the capacitor, which is a device, the number of times equal to the "number of repetitions of the second inspection voltage" input in step S11. For example, the number of repetitions of the second inspection voltage may be 3 to 10 times.

[0062] Next, a second test voltage is applied to the capacitor, and an example of partial discharge occurring in the capacitor will be described with reference to FIG. 8. The second test voltage 33 has a peak voltage that gradually decreases in one modulation period. The second test voltage 35 is continuously applied a plurality of times, and the peak voltage gradually decreases over one modulation period and then sharply increases at the start of the subsequent second test voltage 35 (near 200 [ms] in FIG. 8). For example, in one basic period, the peak voltage sharply increases by more than twice.

[0063] As shown in FIG. 8, in the period when the maximum peak voltage of the second test voltage 35 gradually decreases from 7.5 [kV], partial discharges 36A to 36E of 1.0 [nC] or more, which is the charge threshold, occur at the maximum peak voltage of 7.5 [kV] and the second highest peak voltage of 6.8 [kV].

[0064] On the other hand, after the third highest peak voltage, the partial discharge disappears. That is, after the third highest peak voltage, oil enters between the electrodes of the capacitor, and the insulation of the oil is maintained. Therefore, in step S18 above, the control unit 15 specifies 7.5 [kV] of the maximum peak voltage as the partial discharge start voltage via the voltage specifying unit 152 and stores it in a storage unit (not shown) as the partial discharge start voltage. Also, after the third highest peak voltage, since the partial discharge has disappeared, damage such as destruction of the capacitor dielectric due to the partial discharge can be prevented.

[0065] As described in detail above, in the inspection device 31 according to Embodiment 2, the control unit 15 applies, as a device, the second test voltage whose peak voltage periodically decreases gradually from the maximum peak voltage to reach the minimum peak voltage in one modulation period to the capacitor a set number of times. Then, when the control unit 15 does not detect partial discharge via the detection unit 151, it gradually increases the maximum peak voltage of the test voltage to confirm the occurrence of partial discharge at the next maximum peak voltage.

[0066] As a result, after partial discharge occurs at the maximum peak voltage of the second inspection voltage, the peak voltage gradually decreases and the partial discharge disappears. Therefore, damage to the capacitor dielectric of the capacitor as a device can be prevented, and the partial discharge can be appropriately inspected.

[0067] Further, similar to the inspection device 1 according to the first embodiment, the control unit 15 can determine whether the partial discharge occurring in the capacitor occurs in the oil or in the gas obtained by decomposing the oil, depending on whether the partial discharge continuously occurs. As a result, the control unit 15 can discriminate the quality or manufacturing defect of the capacitor.

[0068] 〔Example of Realization by Software〕 The control unit 15 (particularly, the detection unit 151, the voltage specifying unit 152, the determination unit 153, and the notification unit 154) of the inspection device 1 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

[0069] In the latter case, the inspection device 1 includes a computer that executes instructions of a program that is software for realizing each function. This computer includes, for example, one or more processors and a computer-readable recording medium that stores the above program. Then, in the above computer, the above object of the present invention is achieved by the above processor reading and executing the above program from the above recording medium.

[0070] As the above-mentioned processor, for example, a CPU (Central Processing Unit) can be used. As the above-mentioned recording medium, a "non-transitory tangible medium", for example, in addition to a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, etc. can be used. Further, it may further include a RAM (Random Access Memory) for expanding the above-mentioned program. Further, the above-mentioned program may be supplied to the above-mentioned computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. Note that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above-mentioned program is embodied by electronic transmission.

[0071] [Summary] The inspection device according to Aspect 1 of the present invention includes a voltage application unit that applies an alternating voltage whose amplitude is modulated so as to include an increase and a decrease in peak voltage to a device, and a detection unit that detects partial discharge generated in the device.

[0072] The inspection device according to Aspect 2 of the present invention is, in the above Aspect 1, the voltage application unit applies the alternating voltage whose amplitude is modulated so that the peak voltage changes periodically to the device.

[0073] The inspection device according to Aspect 3 of the present invention is, in the above Aspect 2, the alternating voltage has a waveform in which the peak voltage gradually decreases in one cycle of the peak voltage.

[0074] The inspection device according to Aspect 4 of the present invention is, in the above Aspect 2, the alternating voltage has a waveform in which the peak voltage gradually increases in one cycle of the peak voltage.

[0075] The inspection device according to Aspect 5 of the present invention is, in any one of the above Aspects 1 to 4, the voltage application unit applies the alternating voltage with the maximum peak voltage increased to the device if the partial discharge is not detected.

[0076] The inspection device according to aspect 6 of the present invention includes, in any one of aspects 1 to 5 above, a voltage specifying unit that specifies a partial discharge start voltage from the maximum peak voltage of the AC voltage when the partial discharge is detected.

[0077] The inspection device according to aspect 7 of the present invention includes, in any one of aspects 1 to 6 above, the voltage application unit applies the AC voltage with its amplitude modulated to the device such that the minimum peak voltage in the AC voltage is half or less of the maximum peak voltage.

[0078] The inspection device according to aspect 8 of the present invention includes, in aspect 3 above, a determination unit that determines whether or not the partial discharge continuously occurs during a period in which the peak voltage gradually decreases.

[0079] The inspection device according to aspect 9 of the present invention includes, in aspect 8 above, the determination unit determines the quality of the device based on whether or not the partial discharge continuously occurs during a period in which the peak voltage gradually decreases.

[0080] The inspection method according to aspect 10 of the present invention includes a voltage application step of applying an AC voltage with its amplitude modulated to include an increase and a decrease in peak voltage to a device, and a detection step of detecting partial discharge generated in the device.

[0081] 〔Supplementary Notes〕 The present disclosure is not limited to the above-described embodiments and each modification example, various changes are possible within the scope shown in the claims, and embodiments obtained by appropriately combining the technical means disclosed in each of the embodiments and modification examples are also included in the technical scope of the present disclosure.

Description of Reference Numerals

[0082] 1, 31 Inspection device 11 Voltage application unit 12 Applied waveform acquisition unit 13 Partial discharge measurement unit 15 Control unit 151 Detection unit 152 Voltage determination unit 153 Judgment unit

Claims

1. A voltage application unit that applies an alternating voltage whose amplitude is modulated to include an increase and a decrease in peak voltage to a device, A detection unit that detects partial discharge generated in the device, and an inspection device comprising the same.

2. The inspection device according to claim 1, wherein the voltage application unit applies the alternating voltage whose amplitude is modulated such that the peak voltage changes periodically to the device.

3. The inspection device according to claim 2, wherein the alternating voltage has a waveform in which the peak voltage gradually decreases in one period of the peak voltage.

4. The inspection device according to claim 2, wherein the alternating voltage has a waveform in which the peak voltage gradually increases in one period of the peak voltage.

5. The inspection device according to claim 1, wherein the voltage application unit applies the alternating voltage with an increased maximum peak voltage to the device if no partial discharge is detected.

6. The inspection device according to claim 1, further comprising a voltage specifying unit that specifies a partial discharge start voltage from the maximum peak voltage of the alternating voltage when the partial discharge is detected.

7. The inspection device according to claim 1, wherein the voltage application unit applies the alternating voltage whose amplitude is modulated such that the minimum peak voltage in the alternating voltage is half or less of the maximum peak voltage to the device.

8. The inspection device according to claim 3, further comprising a determination unit that determines whether or not the partial discharge continuously occurs during a period in which the peak voltage gradually decreases.

9. The inspection device according to claim 8, wherein the determination unit determines the quality of the device based on whether or not the partial discharge continuously occurs during a period in which the peak voltage gradually decreases.

10. A voltage application step of applying an alternating voltage whose amplitude is modulated to include an increase and a decrease in peak voltage to a device, A detection step of detecting partial discharge generated in the device, and a partial discharge inspection method including the same.

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