Measuring device, measuring method, and program

Abstract

To enable an evaluation of adequacy of a second voltage value such as partial discharge extinction voltage or repeated partial discharge extinction voltage.SOLUTION: A measuring apparatus 1 is configured to: control an impulse voltage to gradually increase each time the impulse voltage is repeatedly applied to a measuring object 2 a plurality of times; and control the impulse voltage to gradually drop when rise control is stopped according to a state index showing a generation state of partial discharge detected at each value of the impulse voltage. The measuring apparatus 1 is further configured to: acquire the number of times that the partial discharge is detected by each value of the impulse voltage thus dropped; acquire, as a second voltage value, a value of the impulse voltage when a ratio thereof first becomes less than a second threshold value; and acquire, as a related voltage value related to the second voltage value, the smallest voltage value from among a plurality of impulse voltages at which the ratio becomes less than the second threshold value when the impulse voltage at which the ratio becomes equal to or larger than the second threshold value is lowered by one step.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a measuring device, a measuring method, and a program for measuring a voltage related to the occurrence of partial discharge.

Background Art

[0002] Patent Document 1 discloses a measurement system that observes an applied voltage signal representing an impulse voltage applied to a measurement object while gradually increasing the impulse voltage each time a predetermined number of impulse voltages are applied. This measurement system obtains the peak value of the voltage from the applied voltage signal as, for example, the second voltage value of the partial discharge extinction voltage or the repetitive partial discharge extinction voltage in the first cycle in which the number of partial discharges is less than the specified number.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the occurrence of partial discharge is a probabilistic phenomenon, the occurrence frequency and occurrence intensity of partial discharge may accidentally become relatively high or low. In such a situation, the second voltage value as described above may be measured higher than the original value, and in such a case, the measurement object may be evaluated higher than its original performance.

[0005] For example, if the second voltage value is measured higher, a voltage exceeding the original partial discharge resistance of the measurement object may be applied to the measurement object, which may affect the performance of the measurement object.

[0006] The present invention has been made paying attention to such problems, and an object thereof is to enable evaluation of the validity of the second voltage value. [Means for solving the problem]

[0007] According to one aspect of the present invention, a measuring device for measuring a voltage related to the occurrence of partial discharge in an object to be measured, which is composed of one or more coils, includes: an application circuit that repeatedly applies an impulse voltage to the object to be measured multiple times; and a detection circuit that detects a partial discharge occurring in the object to be measured based on a voltage signal generated in the object by the application circuit. The measuring device also includes a boost control means that controls the operation of the application circuit so that the impulse voltage increases in steps each time the impulse voltage is repeatedly applied to the object to be measured; and a stop means that stops the boost control means from controlling the increase of the impulse voltage based on a state index indicating the occurrence state of the partial discharge detected for each value of the impulse voltage. Furthermore, the measuring device includes a buck control means that controls the operation of the application circuit so that the impulse voltage decreases in steps when the increase control is stopped by the stop means; and a processing means that acquires the number of times a partial discharge was detected in the object to be measured out of the multiple times for each value of the impulse voltage. The processing means determines the ratio of the number of times for each value of the impulse voltage by the step-down control means, obtains the value of the impulse voltage when the ratio first falls below the second threshold as the second voltage value, and when the impulse voltage at which the ratio is equal to or greater than the second threshold is lowered by the step-down control means, obtains the smallest voltage value among the multiple impulse voltages at which the ratio falls below the second threshold as the associated voltage value related to the second voltage value. [Effects of the Invention]

[0008] According to this embodiment, by comparing the second voltage value with the related voltage value, it is possible to infer whether the acquired second voltage value is the voltage value when the partial discharge weakens regularly in accordance with the decrease in the impulse voltage, the voltage value when a weak partial discharge occurs accidentally, or the voltage value in a situation where the degree of decrease in the discharge ratio increases or decreases rapidly.

[0009] In this way, by obtaining related voltage values ​​in addition to the second voltage value, it becomes possible to evaluate the validity of the second voltage value. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram showing the functional configuration of a measuring device in an embodiment of the present invention. [Figure 2] Figure 2 is a block diagram showing an example of the functional configuration of the processing unit in a measuring device. [Figure 3] Figure 3 is a conceptual diagram showing an example of measurement results when the voltage control of the impulse voltage is switched from upward control to downward control based on the frequency of partial discharge in the object being measured. [Figure 4] Figure 4 is a conceptual diagram showing an example of measurement results when the voltage control of the impulse voltage is switched from upward control to downward control based on the intensity of partial discharge in the object being measured. [Figure 5] Figure 5 is a conceptual diagram showing an example of measurement results for reference RPDEV and reference PDEV to assess the validity of RPDEV and PDEV. [Figure 6] Figure 6 shows an example of an image displaying the measurement results from the measuring device. [Figure 7] Figure 7 is a flowchart showing the measurement method in this embodiment. [Figure 8] Figure 8 is a flowchart showing an example of the processing procedure for the PDIV measurement process included in the measurement method. [Figure 9] Figure 9 is a flowchart showing an example of the processing procedure for the repetitive measurement process included in the PDIV measurement process. [Figure 10] Figure 10 is a flowchart showing an example of the processing procedure for the RPDIV measurement process included in the measurement method. [Figure 11] Figure 11 is a flowchart showing an example of the processing procedure for the reverse measurement process included in the measurement method. [Figure 12] Figure 12 is a flowchart showing an example of the processing steps for the RPDEV measurement process included in the measurement method. [Figure 13] FIG. 13 is a flowchart showing an example of the processing procedure of the PDEV measurement process included in the measurement method. [Figure 14] FIG. 14 is a flowchart showing an example of the processing procedure of the reference voltage update process included in the PDEV measurement process. [Figure 15] FIG. 15 is a flowchart showing an example of the processing procedure of the result output process included in the measurement method.

MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] FIG. 1 is a block diagram showing the functional configuration of the measuring device in the present embodiment.

[0013] The measuring device 1 is a partial discharge measuring device that measures the voltage related to the partial discharge (PD) of the measurement object 2 composed of one or more coils. Examples of the measurement object 2 include an electric motor, a converter, an inverter, a solenoid valve, and a rectifier circuit.

[0014] The measurement object 2 in the present embodiment is a three-phase electric motor composed of three coils L1 to L3, and the measuring device 1 measures the indexes defined in IEC61934TS as the voltage related to the partial discharge of two phases in the three-phase electric motor.

[0015] Hereinafter, the indexes defined in IEC61934TS will be referred to as PD indexes. Examples of PD indexes include partial discharge inception voltage, repetitive partial discharge inception voltage, partial discharge extinction voltage, and repetitive partial discharge extinction voltage. Hereinafter, these will be referred to as PDIV, RPDIV, PDEV, and RPDEV, respectively.

[0016] The measuring device 1 measures at least one of the boost indicators of PDIV and RPDIV and at least one of the buck indicators of PDEV and RPDEV. In this embodiment, the measuring device 1 measures at least four PD voltage indicators: PDIV, RPDIV, PDEV, and RPDEV.

[0017] The measuring device 1 is a computer, and consists of a processor, ROM (Read Only Memory), RAM (Random Access Memory), input / output interfaces, and buses that connect these components to each other.

[0018] The measuring device 1 comprises a display unit 10, an operation unit 20, a processing unit 30, an application circuit 40, a detection circuit 50, and a storage unit 60.

[0019] The display unit 10 is composed of an LED (Light Emitting Diode) display, a liquid crystal panel, or a touch panel for displaying images. The display unit 10 displays the measurement conditions and measurement results for the voltage related to partial discharge in the object being measured. In other words, the display unit 10 functions as an output means for outputting the results obtained by the processing unit 30.

[0020] The operation unit 20 is composed of a plurality of push buttons provided around the display screen that constitutes the display unit 10, a touch sensor placed within the display screen, or a keyboard and mouse, etc. The operation unit 20 receives input operations from the user, who is the user of the measuring device 1, and generates an operation signal indicating the content of the received input operation.

[0021] Input operations include, for example, pressing the power button, setting measurement conditions, instructing the execution of the measurement process, and instructing the stopping of the measurement process.

[0022] When the operation unit 20 receives an input operation from the user to set measurement conditions, it outputs the operation signal indicating the measurement conditions to the processing unit 30 in order to record it in the storage unit 60. Also, when the operation unit 20 receives an input operation from the user instructing the execution of a measurement process, it outputs an operation signal indicating the content of that input operation to the processing unit 30.

[0023] The processing unit 30 is comprised of a processor. Examples of processors include a CPU (Central Processing Unit) or an MPU (Micro Processor Unit).

[0024] The processing unit 30 performs a measurement process to measure the voltage related to the partial discharge of the object to be measured 2. In this embodiment, the processing unit 30 controls the operation of the application circuit 40 and the detection circuit 50 to obtain the PD index of the object to be measured 2.

[0025] As a specific example, the processing unit 30 repeatedly applies the same impulse voltage from the application circuit 40 to the object to be measured 2 and detects the state of partial discharge in the object to be measured 2 based on the output signal of the detection circuit 50. Then, each time the impulse voltage output from the application circuit 40 is repeatedly applied to the object to be measured 2, the processing unit 30 gradually increases the value of the impulse voltage, and then gradually decreases the value of the impulse voltage.

[0026] In this embodiment, the processing unit 30 controls the operation of the application circuit 40 in accordance with the method specified in IEC61934TS. The processing unit 30 then obtains the PD index of the object to be measured 2 by measuring the frequency and intensity of partial discharge in the object to be measured 2 for each impulse voltage value based on the voltage signal output from the detection circuit 50. The processing unit 30 records the obtained PD voltage index as a measurement result in the storage unit 60.

[0027] The application circuit 40 is a pulse supply circuit that repeatedly applies a pulsed impulse voltage to the object to be measured 2. In this embodiment, the output terminals of the application circuit 40 are connected to two terminals of any two phases of the three-phase motor, which is the object to be measured 2. Alternatively, the output terminals of the application circuit 40 may be connected to two terminals from among the terminals of each phase and the neutral point terminal.

[0028] The application circuit 40 applies the same impulse voltage to two terminals of any two phases of the three-phase motor, repeating this 10 times at predetermined time intervals. The application circuit 40 also changes the value of the impulse voltage repeatedly applied to the object to be measured 2 in steps according to the control signal from the processing unit 30. The number of times the application circuit 40 applies the impulse voltage may be less than 10 or more than 10.

[0029] The detection circuit 50 is a discharge detection circuit that detects partial discharge occurring in the object to be measured 2 based on the voltage signal generated in the object to be measured 2 by the application circuit 40. In this embodiment, both terminals of any two phases of the three-phase motor, which is the object to be measured 2, are connected to the pair of terminals of the detection circuit 50.

[0030] The detection circuit 50 detects the voltage generated between both terminals of the three-phase motor each time an impulse voltage is applied from the application circuit 40. The detection circuit 50 outputs a voltage signal indicating the magnitude of the detected voltage to the processing unit 30.

[0031] When a partial discharge occurs in the object 2 to be measured to which an impulse voltage is applied, a pulsed voltage is superimposed on the voltage signal output from the detection circuit 50. Therefore, by extracting the pulse component of the output signal of the detection circuit 50 and measuring the peak value of the extracted pulse component, it is possible to detect the partial discharge of the object 2. For example, a filter circuit is provided between the detection circuit 50 and the processing unit 30 to extract the pulse component of the output signal of the detection circuit 50. Alternatively, digital filtering may be performed in the processing unit 30 instead of a filter circuit.

[0032] The storage unit 60 is composed of RAM and ROM. The storage unit 60 stores information related to the measurement process performed by the processing unit 30. The storage unit 60 records measurement conditions and measurement results as information related to the measurement process.

[0033] The measurement conditions include the sweep range of the impulse voltage applied to the object 2, the frequency and intensity of partial discharges occurring in the object 2, and threshold values.

[0034] Furthermore, the storage unit 60 stores a program for the processing unit 30 to execute the measurement process in this embodiment. In other words, the storage unit 60 is a computer-readable storage medium that stores a program for controlling each part of the measuring device 1.

[0035] The communication unit 70 is composed of a communication circuit that communicates with an external device of the measuring device 1. For example, the communication unit 70 can receive measurement conditions and transmit measurement results to an external device wirelessly or via wired connection through a network such as the Internet or a telephone network. In other words, the communication unit 70 functions as an output means that outputs the results obtained by the processing unit 30.

[0036] Next, an example of the configuration of the processing unit 30 in the measuring device 1 will be described with reference to Figure 2.

[0037] Figure 2 is a block diagram showing the functional configuration of the processing unit 30 in this embodiment. The processing unit 30 comprises a control unit 30A and an arithmetic unit 30B.

[0038] The control unit 30A controls the operation of the application circuit 40 to apply the same impulse voltage to the object to be measured 2 multiple times. The control unit 30A then gradually increases the peak value of the impulse voltage output from the application circuit 40 from the starting voltage value of the sweep range, and then gradually decreases the peak value of the impulse voltage to the ending voltage value of the sweep range.

[0039] In this embodiment, the control unit 30A sets a predetermined initial value as the starting voltage value in the application circuit 40, and applies an impulse voltage representing that value to the object to be measured 2, repeating this 10 times.

[0040] The control unit 30A comprises a boost control unit 31, a buck control unit 32, and a circuit control unit 33.

[0041] The boost control unit 31 functions as a boost control means that controls the operation of the application circuit 40 so that the impulse voltage increases in steps each time the impulse voltage is repeatedly applied to the object to be measured 2.

[0042] In this embodiment, the boost control unit 31 increases the peak value of the impulse voltage output from the application circuit 40 by a predetermined amount each time an equivalent impulse voltage is applied 10 times. The predetermined amount is a value set in advance, for example, to 10[V].

[0043] The step-down control unit 32 functions as a step-down control means that controls the operation of the application circuit 40 so that the impulse voltage decreases in steps relative to the peak value of the impulse voltage when the boost control by the boost control unit 31 is stopped.

[0044] In this embodiment, the step-down control unit 32 reduces the peak value of the impulse voltage output from the application circuit 40 by a predetermined amount each time an equivalent impulse voltage is applied 10 times. The predetermined reduction amount is a predetermined value and may be the same as or different from the predetermined increase amount. The predetermined reduction amount is set to, for example, 10[V].

[0045] The circuit control unit 33 functions as a stopping means that stops the boost control unit 31's control of increasing the impulse voltage based on a state index indicating the occurrence state of partial discharge detected for each value of the impulse voltage by the boost control unit 31.

[0046] Examples of indicators for the partial discharge state include the discharge ratio, which shows the ratio of the number of times partial discharge was detected in the object 2 out of 10 measurements, and the discharge peak value, which shows the peak value of the pulse component caused by partial discharge in the output signal of the detection circuit 50.

[0047] In this embodiment, the circuit control unit 33 determines whether the discharge ratio described above is smaller than the switching threshold. The switching threshold is a threshold for switching the impulse voltage raising / lowering control from raising control to lowering control. The switching threshold is obtained from the operation unit 20 or the communication unit 70 and is stored in advance in the storage unit 60.

[0048] In this embodiment, the switching threshold is set to a value greater than the voltage boost threshold for the discharge ratio required to obtain RPDIV, for example, 100%. This makes it possible to obtain the discharge ratio at an impulse voltage higher than RPDIV, and by understanding this discharge ratio, it becomes possible to determine the validity of RPDIV.

[0049] If the circuit control unit 33 determines that the discharge ratio of the partial discharge is less than the switching threshold, it continues the impulse voltage increase control by the boost control unit 31. If it determines that the discharge ratio has reached the switching threshold, it stops the impulse voltage increase control. This switches the impulse voltage control from increase control to decrease control.

[0050] Furthermore, when the impulse voltage is being gradually reduced by the step-down control unit 32, the circuit control unit 33 determines whether the magnitude of the range of impulse voltages in which the discharge ratio is continuously 0% is greater than a predetermined value. If the magnitude of the range of impulse voltages is less than or equal to the predetermined value, the circuit control unit 33 continues to step down the impulse voltage.

[0051] On the other hand, if the range of the impulse voltage is greater than a predetermined value, the circuit control unit 33 stops the step-down control of the impulse voltage. This makes it possible to end the measurement before the impulse voltage drops to the termination voltage value mentioned above, thus shortening the measurement time.

[0052] The calculation unit 30B calculates a PD index and a reference PD index for determining the validity of the PD index based on the voltage signal output from the detection circuit 50. The calculation unit 30B includes a state index calculation unit 30C equipped with a PD intensity detection unit 34 and a PD frequency acquisition unit 35, a PD index acquisition unit 36, and a reference PD index acquisition unit 37.

[0053] The state index calculation unit 30C calculates a state index that indicates the state of partial discharge occurring in the object 2 when an impulse voltage is applied to the object 2. In this embodiment, the state index calculation unit 30C detects the intensity and frequency of partial discharge occurring in the object 2 as state indexes for partial discharge in the object 2.

[0054] The PD intensity detection unit 34 detects the magnitude, i.e., the intensity, of the partial discharge generated in the object to be measured 2. Specifically, each time a single impulse voltage is applied to the object to be measured 2 from the application circuit 40, the PD intensity detection unit 34 detects the peak-to-peak value of the voltage signal output from the detection circuit 50.

[0055] In this embodiment, the PD intensity detection unit 34 has, for example, a high-pass filter (HPF), and each time a single impulse voltage is applied to the object to be measured 2, it extracts the pulse component of the voltage signal output from the detection circuit 50 and measures the peak value of that pulse component. When the measured peak value exceeds the detection threshold for detecting partial discharge, the PD intensity detection unit 34 outputs the measured peak value as the peak value of partial discharge to the PD frequency acquisition unit 35.

[0056] The PD frequency acquisition unit 35 detects the frequency of partial discharges occurring in the object being measured 2. Specifically, the PD frequency acquisition unit 35 acquires the number of times or the ratio of times partial discharges are detected out of the number of times the device is repeatedly applied.

[0057] In this embodiment, the PD frequency acquisition unit 35 acquires a discharge ratio that indicates the ratio of the number of times partial discharge is detected out of 10 for each impulse voltage value. The PD frequency acquisition unit 35 then outputs the discharge ratio acquired for each impulse voltage value to the PD index acquisition unit 36.

[0058] The PD index acquisition unit 36 ​​acquires a PD index for the object to be measured 2 based on the discharge ratio acquired for each impulse voltage value by the boost control unit 31 and the buck control unit 32.

[0059] The PD index acquisition unit 36 ​​functions as a processing means that determines the discharge ratio for each value of the impulse voltage from the boost control unit 31 and acquires a first voltage value that indicates the magnitude of the impulse voltage when the discharge ratio exceeds a first threshold.

[0060] In this embodiment, the PD index acquisition unit 36 ​​acquires a PDIV, which indicates the magnitude of the impulse voltage when the discharge ratio becomes equal to or greater than the starting threshold among the various impulse voltage values ​​set by the boost control unit 31. This PDIV corresponds to the first voltage value.

[0061] The aforementioned starting threshold is the ratio when the number of partial discharge detections is 1, and corresponds to the first threshold. In this embodiment, this starting threshold is set to 10%, which is 1 / 10, when the impulse voltage is applied 10 times, and is stored in the memory unit 60 beforehand. The starting threshold may also be set by an input operation of the operation unit 20, or it may be obtained from an external device via the communication unit 70.

[0062] The PD index acquisition unit 36 ​​then acquires RPDIV, which represents the magnitude of the impulse voltage when the discharge ratio exceeds the boost threshold, among the various impulse voltage values ​​set by the boost control unit 31. RPDIV also corresponds to the first voltage value.

[0063] The boost threshold described above is a discharge ratio that indicates a state in which partial discharge is occurring to a moderate degree, and corresponds to the first threshold. In this embodiment, this boost threshold is set to 50% and is pre-stored in the storage unit 60. The boost threshold may be set by an input operation on the operation unit 20, or it may be obtained from an external device via the communication unit 70.

[0064] Furthermore, the PD index acquisition unit 36 ​​functions as a processing means for acquiring a third voltage value that indicates the magnitude of the impulse voltage when the boost control is stopped by the circuit control unit 33. This third voltage value is the maximum value of the boosted impulse voltage and will be referred to as the aliasing voltage below.

[0065] Furthermore, the PD index acquisition unit 36 ​​functions as a processing means that calculates the discharge ratio for each value of the impulse voltage from the step-down control unit 32 and acquires a second voltage value that indicates the magnitude of the impulse voltage when the discharge ratio falls below a second threshold.

[0066] In this embodiment, the PD index acquisition unit 36 ​​acquires RPDEV, which indicates the magnitude of the impulse voltage at which the discharge ratio first falls below the step-down threshold among the impulse voltages set by the step-down control unit 32. This RPDEV corresponds to the second voltage value.

[0067] The step-down threshold mentioned above is a discharge ratio that indicates a state in which partial discharge is occurring to a moderate degree, and corresponds to the second threshold. In this embodiment, the step-down threshold is set to 50% and is pre-stored in the memory unit 60.

[0068] This step-down threshold may be set by an input operation on the control unit 20, or it may be obtained from an external device via the communication unit 70. Furthermore, the step-down threshold may be the same value as the step-up threshold or a different value.

[0069] Furthermore, the PD index acquisition unit 36 ​​acquires the PDEV, which indicates the magnitude of the impulse voltage when the discharge ratio first falls below the extinction threshold among the impulse voltage values ​​set by the step-down control unit 32. This RPDEV corresponds to the second voltage value.

[0070] The extinction threshold described above is the discharge ratio when partial discharge occurs once, and corresponds to the second threshold. In this embodiment, this extinction threshold is set to 10%, which is 1 / 10, when the impulse voltage is applied 10 times, and is stored in the memory unit 60 in advance. The extinction threshold may be set by an input operation on the operation unit 20, or it may be obtained from an external device via the communication unit 70.

[0071] In this way, the PD index acquisition unit 36 ​​acquires PDIV, RPDIV, the aliased voltage value indicating the maximum value of the impulse voltage, PDEV, and RPDEV as PD indices related to the object to be measured 2. The PD index acquisition unit 36 ​​then outputs the acquired PD indices as measurement results to the storage unit 60.

[0072] Furthermore, the PD index acquisition unit 36 ​​outputs the discharge ratio corresponding to each value of the impulse voltage in the upward control and the discharge ratio corresponding to each value of the impulse voltage in the downward control to the reference PD index acquisition unit 37.

[0073] The reference PD index acquisition unit 37 functions as a processing means for acquiring a reference PD index to determine the validity of the PD index based on the discharge ratio acquired for each impulse voltage value by the step-down control unit 32.

[0074] Reference PD indices include a reference RPDEV for assessing the validity of RPDEV, and a reference PDEV for assessing the validity of PDEV. Reference RPDEV and reference PDEV correspond to the relevant voltage values.

[0075] The reference PD index acquisition unit 37 acquires the lowest voltage value among multiple impulse voltages whose discharge ratio falls below the step-down threshold when the step-down control unit 32 reduces an impulse voltage whose discharge ratio is above the step-down threshold by one step, as the reference RPDEV associated with the RPDEV.

[0076] In this embodiment, the reference PD index acquisition unit 37 acquires the value of the impulse voltage when the discharge ratio falls below the step-down threshold after the impulse voltage, when the discharge ratio is above the step-down threshold during the impulse voltage step-down process, as a candidate value for the reference RPDEV. The reference PD index acquisition unit 37 then selects the lowest voltage value from the acquired candidate values ​​and sets the selected voltage value as the reference RPDEV.

[0077] Furthermore, the reference PD index acquisition unit 37 acquires the lowest voltage value among multiple impulse voltages whose discharge ratio falls below the extinction threshold when the step-down control unit 32 reduces the impulse voltage in which the discharge ratio is above the extinction threshold by one step, as the reference PDEV associated with the PDEV.

[0078] In this embodiment, the reference PD index acquisition unit 37 acquires the value of the impulse voltage at which the discharge ratio falls below the step-down threshold when the impulse voltage at which the discharge ratio is above the extinction threshold is lowered by one step, as a candidate value for the reference PDEV, while the impulse voltage is decreasing in steps. The reference PD index acquisition unit 37 then selects the lowest voltage value from the acquired candidate values ​​and sets the selected voltage value as the reference PDEV.

[0079] In this way, the reference PD index acquisition unit 37 acquires reference RPDEV and reference PDEV as reference PD indices. The reference PD index acquisition unit 37 then outputs the acquired reference PD indices as measurement results to the storage unit 60.

[0080] Similarly, the reference PD index acquisition unit 37 outputs the discharge ratio corresponding to each value of the impulse voltage in the upward control and the discharge ratio corresponding to each value of the impulse voltage in the downward control as measurement results to the storage unit 60.

[0081] The memory unit 60 stores the measurement results and measurement conditions described above. Examples of measurement conditions include the opening start threshold, boost threshold, switching threshold or tolerance value, buck threshold, extinction threshold, start voltage value, end voltage value, etc.

[0082] In this embodiment, the reference PD index acquisition unit 37 is provided in the calculation unit 30B, but the reference PD index acquisition unit 37 may be omitted.

[0083] Next, the measurement results of the PD index obtained by the measuring device 1 will be explained with reference to Figures 3 to 6.

[0084] Figure 3 is a conceptual diagram showing an example of the measurement results in this embodiment.

[0085] Figure 3(a) shows the measurement results when the voltage control of the impulse voltage is switched from upward control to downward control based on the discharge ratio of the object being measured 2. Figure 3(b) shows, as a comparative example, the measurement results when the voltage control of the impulse voltage is switched from upward control to downward control when the impulse voltage reaches a predetermined upper limit.

[0086] In this example, an impulse voltage with a starting voltage value Vs is repeatedly applied to the object being measured 2 10 times. After each 10 applications, the impulse voltage is increased by 10[V], and then decreased by 10[V] until it reaches the ending voltage value Ve.

[0087] Furthermore, the start threshold T1 for obtaining PDIV and the extinction threshold T2 for obtaining PDEV are both the same value, and are set to 10%, which is the ratio in which a partial discharge occurs once out of 10 impulse voltage applications.

[0088] Furthermore, the boost threshold T1r for obtaining RPDIV and the buck threshold T2r for obtaining RPDEV are both the same value, set to 50%. Also, the start voltage value Vs and the end voltage value Ve of the impulse voltage are both set to the same value.

[0089] Furthermore, in the example shown in Figure 3(a), the switching threshold Tsw for switching the impulse voltage control from upward control to downward control is set to 100%. On the other hand, in the example shown in Figure 3(b), the upper limit for switching the impulse voltage control from upward control to downward control is set to 920[V].

[0090] As shown in Figure 3(b), in the method of switching the voltage control of the impulse voltage to a downward control when the impulse voltage reaches the upper limit voltage Vt, the impulse voltage may continue to increase even after the discharge ratio reaches 100%, depending on how the upper limit is set or individual differences in the object being measured 2. As a result, an excessive voltage is continuously applied to the object being measured 2, which may damage the object being measured 2.

[0091] In contrast, in this embodiment, as shown in Figure 3(a), the control of increasing the impulse voltage is stopped according to the magnitude of the discharge ratio, so that the influence of the applied voltage on the object being measured 2 can be suppressed.

[0092] In addition, in this embodiment, the switching threshold Tsw is set to a value greater than the boost threshold T1r. This makes it possible to set the aliasing voltage to a voltage value greater than RPDIV. By making the aliasing voltage greater than RPDIV, the user can understand the validity of RPDIV.

[0093] For example, the voltage value of RPDIV may be estimated based on the relationship between the discharge ratio of PDIV and the discharge ratio of aliasing voltage, and the validity of the measurement results may be determined by comparing the estimated value of RPDIV with the measured value.

[0094] Figure 4 is a conceptual diagram showing an example of measurement results when the voltage control of the impulse voltage is switched based on the discharge peak value instead of the discharge ratio. In Figure 4, the start threshold T1, extinction threshold T2, boost threshold T1r, buck threshold T2r, start voltage value Vs, and end voltage value Ve are the same as those shown in Figure 3.

[0095] Figure 4(a) shows the measurement results when the voltage control of the impulse voltage is switched from upward control to downward control based on the discharge peak of object 2 being measured. Figure 4(b), similar to Figure 3(b), shows the measurement results when the voltage control of the impulse voltage is switched from upward control to downward control based on the upper limit of the impulse voltage, as a comparative example.

[0096] In Figures 4(a) and 4(b), the discharge ratio is shown by a thick line and the discharge peak value is shown by a thin line for each impulse voltage value.

[0097] Furthermore, in the example shown in Figure 4(a), an allowable value To is set for switching the impulse voltage control from upward control to downward control. On the other hand, in the example shown in Figure 4(b), the upper limit is set to 920[V], similar to Figure 3(b).

[0098] As shown in Figure 4(b), in the method of switching the voltage control of the impulse voltage to a downward control when the impulse voltage reaches the upper limit, the impulse voltage will continue to increase even if the discharge peak value becomes extremely large due to the way the upper limit is set or individual differences in the object being measured 2. As a result, an excessive voltage will continue to be applied to the object being measured 2, which may damage the object being measured 2.

[0099] In contrast, the method shown in Figure 4(a) stops controlling the rise of the impulse voltage according to the magnitude of the discharge peak value, thereby suppressing the effect of the applied voltage on the object being measured 2.

[0100] Furthermore, in the example shown in Figure 4(a), the discharge peak value suddenly increases at a voltage value greater than the RPDIV, but a similar phenomenon can occur at voltage values ​​lower than the RPDIV.

[0101] In such cases, continuously increasing the impulse voltage until RPDIV is acquired may adversely affect object 2. Therefore, by stopping the impulse voltage increase control according to the magnitude of the discharge peak value, it is possible to avoid applying an excessive voltage to object 2.

[0102] Figure 5 illustrates the measurement results of the reference RPDEV and reference PDEV. In Figure 5, the start threshold T1, extinction threshold T2, boost threshold T1r, and buck threshold T2r are the same as those shown in Figure 3. On the other hand, the start voltage value Vs and end voltage value Ve are different from those shown in Figure 3.

[0103] Figure 5(a) shows ideal measurement results where the discharge ratio increases regularly and monotonically until the impulse voltage reaches the aliasing voltage, and then decreases regularly and monotonically beyond the aliasing voltage. On the other hand, Figure 5(b) shows measurement results where there are fluctuations in the frequency and magnitude of partial discharge.

[0104] As shown in Figure 5(a), when the discharge ratio changes regularly as the impulse voltage is swept, RPDEV and reference RPDEV will have the same voltage value, and PDEV and reference PDEV will have the same voltage value.

[0105] However, since the occurrence of partial discharge is a probabilistic phenomenon, the frequency and intensity of partial discharge may randomly become relatively high or low. In such situations, RPDEV and PDEV may be measured at an overestimation. When RPDEV and PDEV are used as indicators of the partial discharge resistance of the object being measured 2, if these indicators are overestimated, there is a risk of inducing damage to the object being measured 2 due to the application of a voltage exceeding its partial discharge resistance.

[0106] As a countermeasure, in this embodiment, in addition to RPDEV and PDEV, reference PD indices called reference RPDEV and reference PDEV are obtained.

[0107] As shown in Figure 5(b), the reference RPDEV is set to the smallest voltage value among the impulse voltages when the discharge ratio falls below the step-down threshold T2r, after the impulse voltage when the discharge ratio is above the step-down threshold T2r has been lowered by one step.

[0108] More specifically, the measuring device 1 acquires as a reference candidate value the value of the impulse voltage at which the discharge ratio falls below the step-down threshold T2r when the impulse voltage is reduced by one step while the impulse voltage at which the discharge ratio is equal to or greater than the step-down threshold T2r is reduced. In the example shown in Figure 5(b), the reference candidate values ​​are 1160[V] and 1140[V].

[0109] The measuring device 1 then sets the smallest voltage value among the acquired reference candidate values ​​as the reference RPDEV. In the example shown in Figure 5(b), 1140[V] is set as the reference RPDEV as the smallest voltage value among 1160[V] and 1140[V].

[0110] By setting the reference RPDEV in this way, the reference RPDEV takes into account the randomness of partial discharge, and therefore, in the actual measurement process, it will be estimated to be lower than the RPDEV.

[0111] Similarly, the reference PDEV is set to the smallest voltage value among the impulse voltage values ​​when the discharge ratio falls below the extinction threshold T2, while the impulse voltage when the discharge ratio is above the extinction threshold T2 is lowered by one step.

[0112] More specifically, the measuring device 1 acquires each value of the impulse voltage at which the discharge ratio falls below the extinction threshold T2 when the impulse voltage is reduced by one step while the impulse voltage is being reduced from one step where the discharge ratio is equal to or greater than the extinction threshold T2, as a reference candidate value. The measuring device 1 then sets the smallest voltage value among the acquired reference candidate values ​​as the reference PDEV.

[0113] By setting a reference PDEV in this way, the reference PDEV will be estimated lower than the PDEV because, like the reference RPDEV, it takes into account the randomness of partial discharge.

[0114] Here, we have described an example where the smallest voltage value among the candidate reference values ​​for the impulse voltage is stored in the reference PDEV. However, instead, a voltage value smaller than the largest voltage value among multiple candidate reference values, such as the second or third smallest voltage value, may be selected as the reference PDEV. Alternatively, the average or median of multiple candidate reference values ​​may be used. The same applies to the reference RPDEV.

[0115] As described above, by measuring the reference PDEV and reference RPDEV, it becomes possible to compare them with the PDEV and RPDEV. Therefore, users can judge the validity of the PDEV and RPDEV.

[0116] For example, the measuring device 1 may calculate an evaluation value for the validity of PDEV and RPDEV based on the difference between reference PDEV and PDEV and the difference between reference RPDEV and RPDEV. Specifically, the measuring device 1 may decrease the evaluation value for the validity of PDEV as the difference between reference PDEV and PDEV increases.

[0117] Alternatively, the measuring device 1 may reset the reference PDEV and the average of the PDEVs to PDEV, and the reference RPDEV and the average of the RPDEVs to RPDEV, or it may reset the reference RPDEV to PDEV and the reference RPDEV to RPDEV.

[0118] Figure 6 shows an example of a display image 11 of the measurement results from the measuring device 1.

[0119] In display image 11, the voltage values ​​and discharge ratios for each PD index, PDIV, RPDIV, aliasing voltage, RPDEV, reference RPDEV, PDEV, and reference PDEV, are displayed.

[0120] This allows users to, for example, compare the midpoint of PDIV and aliasing voltage with the measured value of RPDIV, or compare the midpoint of aliasing voltage and PDEV with the measured value of RPDEV, thereby enabling them to understand the magnitude of fluctuations in partial discharge.

[0121] In this example, since the voltage values ​​of RPDEV and reference RPDEV are different, the voltage value of reference RPDEV is displayed in bold and underlined to indicate this. The same applies to reference PDEV. Furthermore, the evaluation results of the validity of PDEV and RPDEV are displayed as supplementary information.

[0122] In this way, by using the measured values ​​of reference RPDEV and reference PDEV, it is possible to avoid overestimating the partial discharge resistance of the object being measured 2.

[0123] Next, the operation of the measuring device 1 in this embodiment will be described with reference to Figures 7 to 15.

[0124] Figure 7 is a flowchart showing an example of a measurement method performed by the measuring device 1.

[0125] In step S1, the measuring device 1 performs a PDIV measurement process to measure the PDIV of the object to be measured 2 while gradually increasing the impulse voltage applied to the object to be measured 2. The PDIV measurement process will be described later with reference to Figure 8.

[0126] In step S2, the measuring device 1 performs an RPDIV measurement process to measure the RPDIV of the object to be measured 2 while gradually increasing the impulse voltage. The RPDIV measurement process will be described later with reference to Figure 10.

[0127] In step S3, the measuring device 1 determines whether the voltage control of the impulse voltage was switched from upward control to downward control in either step S1 or step S2.

[0128] In this example, a boost stop flag is used to indicate whether or not the boost control has been stopped in order to switch the voltage control of the impulse voltage to a downward control. This boost stop flag is set to "TRUE" if the boost control has been stopped in step S1 or S2, and to "FALSE" if the boost control has not been stopped.

[0129] Then, if the boost stop flag indicates "FALSE", the measuring device 1 maintains the boost control and proceeds to step S4. If the boost stop flag indicates "TRUE", the device switches to the lowering control and skips step S4, proceeding to step S5.

[0130] In step S4, the measuring device 1 performs a reverse measurement process to switch the voltage control of the impulse voltage from upward control to downward control while measuring the discharge ratio of the object to be measured 2. The reverse measurement process will be described later with reference to Figure 11.

[0131] In step S5, the measuring device 1 determines whether or not there is a voltage value in the PDIV in order to determine whether or not to measure RPDEV and PDEV. In step S1, it is also possible that the control of the rise of the impulse voltage is stopped before the impulse voltage reaches the PDIV. In such a case, no voltage value is set in the PDIV, and the measurement of RPDEV and PDEV is omitted.

[0132] Therefore, if PDIV shows "No Data," measurement of RPDEV and PDEV is impossible, and the measuring device 1 skips steps S6 and S7 and proceeds to step S8. On the other hand, if a voltage value has already been set for PDIV, the measuring device 1 determines that RPDEV and PDEV can be measured and proceeds to step S6.

[0133] In step S6, the measuring device 1 performs an RPDEV measurement process to measure the RPDEV of the object to be measured 2 while gradually decreasing the impulse voltage. The RPDEV measurement process will be described later with reference to Figure 12.

[0134] In step S7, the measuring device 1 performs a PDEV measurement process to acquire the PDEV of the object to be measured 2 while gradually decreasing the impulse voltage. The PDEV measurement process will be described later with reference to Figure 13.

[0135] In step S8, the measuring device 1 performs result output processing to output measurement results including PDIV, RPDIV, RPDEV, and PDEV for the object to be measured 2. The result output processing will be described later with reference to Figure 15.

[0136] Once step S8 is completed, the series of processes for the measurement method described above is finished.

[0137] Figure 8 is a flowchart showing an example of the processing procedure for the PDIV measurement process performed in step S1.

[0138] In step S11, the measuring device 1 sets the starting voltage value Vs to the impulse voltage Vin. In this embodiment, the initial value V1 is used as the starting voltage value Vs.

[0139] In step S12, the measuring device 1 sets the boost stop Flag to "FALSE" in order to start controlling the increase of the impulse voltage Vin.

[0140] In step S13, the measuring device 1 performs a repetitive discharge measurement process. This allows the measuring device 1 to repeatedly apply the set impulse voltage Vin to the object 2 to determine the discharge ratio Rd, which indicates the frequency of partial discharge in the object 2. This repetitive discharge measurement process will be described later with reference to Figure 9.

[0141] In step S14, the measuring device 1 determines whether the boost stop condition for stopping the rise control of the impulse voltage Vin has been met.

[0142] In this embodiment, the boost stop condition is determined by whether or not the discharge ratio Rd has reached the switching threshold Tsw. This switching threshold Tsw is a threshold for switching the voltage control of the impulse voltage Vin from upward control to downward control, and is set to, for example, 100%.

[0143] If the discharge ratio Rd reaches the switching threshold Tsw, the measuring device 1 determines that the boost stop condition has been met and proceeds to step S15. If the discharge ratio Rd has not reached the switching threshold Tsw, it proceeds to step S16.

[0144] In step S15, the measuring device 1 sets the boost stop Flag to "TRUE," which means that the boost stop condition has been met.

[0145] In step S16, the measuring device 1 determines whether the discharge ratio Rd exceeds 0%. That is, the measuring device 1 determines whether the discharge ratio Rd is equal to or greater than the above-mentioned starting threshold T1. This starting threshold T1 represents the discharge ratio when partial discharge is detected only once.

[0146] If the discharge ratio Rd exceeds 0%, the measuring device 1 proceeds to step S19, and if the discharge ratio Rd is 0%, it proceeds to step S17.

[0147] In step S17, the measuring device 1 determines whether the boost stop Flag indicates "TRUE," which means that the control of increasing the impulse voltage Vin is stopped.

[0148] If the boost stop flag indicates "TRUE", the measurement device 1 terminates the PDIV measurement process and returns to the processing procedure of the measurement method shown in Figure 7, because the voltage control of the impulse voltage Vin has been switched to a decrease control. On the other hand, if the boost stop flag indicates "FALSE", the measurement device 1 maintains the increase control and proceeds to step S18.

[0149] In step S18, the measuring device 1 sets a new value for the impulse voltage Vin by adding an increase amount ΔV to the value set for the impulse voltage Vin. The measuring device 1 then increases the value of the impulse voltage Vin, which is repeatedly applied to the object to be measured 2, until the discharge ratio Rd exceeds 0% or the boost stop condition is met.

[0150] In other words, steps S13 to S18 correspond to a boost control step in which the impulse voltage Vin is gradually increased each time the impulse voltage Vin is repeatedly applied to the object to be measured 2.

[0151] In step S19, the measuring device 1 sets the value of the impulse voltage Vin when the discharge ratio Rd exceeds 0% to PDIV. That is, the measuring device 1 obtains PDIV, which represents the value of the impulse voltage Vin when the discharge ratio Rd first becomes equal to or greater than the starting threshold T1.

[0152] Once the processing in step S19 is complete, the process returns to the measurement method shown in Figure 7, and the PDIV measurement process in step S1 of the measurement method is completed.

[0153] In this embodiment, one of the conditions for stopping the boost in step S14 is to determine whether the discharge ratio Rd has reached the switching threshold Tsw. Alternatively, the condition may be to determine whether the discharge peak value exceeds a predetermined allowable value To.

[0154] In this case, if the discharge peak value exceeds the allowable value To, the boost stop flag is set to "TRUE" and the control of the impulse voltage Vin rise is stopped.

[0155] Alternatively, when the discharge ratio Rd reaches the switching threshold Tsw, or when the discharge peak value exceeds the allowable value To, the boost stop Flag may be set to "TRUE" and the control of the impulse voltage Vin increase may be stopped.

[0156] Figure 9 is a flowchart showing an example of the processing procedure for the repeated discharge measurement process performed in step S13.

[0157] In step S131, the measuring device 1 applies the same impulse voltage Vin to the object to be measured 2 multiple times. In other words, step S131 corresponds to an application step in which the impulse voltage Vin is applied to the object to be measured 2 multiple times.

[0158] In step S132, the measuring device 1 detects the discharge peak value caused by partial discharge occurring in the object to be measured 2 from the voltage signal generated in the object to be measured 2 for each impulse voltage Vin. In other words, step S132 corresponds to a detection step in which partial discharge occurs in the object to be measured 2 based on the voltage signal generated in the object to be measured 2 in step S131.

[0159] In step S133, the measuring device 1 determines the discharge ratio Rd, which is the ratio of the number of times the discharge peak value was detected out of the number of times the impulse voltage Vin was repeatedly applied. In other words, step S133 corresponds to a processing step that acquires the number of times a partial discharge was detected in the object to be measured 2 for each value of the impulse voltage Vin.

[0160] Once step S133 is completed, the process returns to the PDIV measurement procedure shown in Figure 8, and the repeated discharge measurement process of step S13 in the PDIV measurement process is completed.

[0161] Next, the RPDIV measurement process in step S2 of the measurement method shown in Figure 7 will be explained with reference to Figure 10.

[0162] Figure 10 is a flowchart showing an example of the processing procedure for the RPDIV measurement process performed in step S2.

[0163] In step S21, the measuring device 1 determines whether the boost stop condition for stopping the rise control of the impulse voltage Vin has been met.

[0164] In this embodiment, if the discharge ratio Rd reaches the switching threshold Tsw, the measuring device 1 determines that the boost-stop condition has been met and proceeds to step S22. If the discharge ratio Rd has not reached the switching threshold Tsw, it skips step S22 and proceeds to step S23. Alternatively, the measuring device 1 may determine that the boost-stop condition has been met if the discharge peak value exceeds a predetermined allowable value To.

[0165] In step S22, the measuring device 1 sets the boost stop Flag to "TRUE," which means that the boost stop condition has been met.

[0166] In step S23, the measuring device 1 determines whether the discharge ratio Rd is equal to or greater than the above-mentioned boost threshold T1r. If the discharge ratio Rd is less than the boost threshold T1r, the measuring device 1 proceeds to step S24.

[0167] In step S24, the measuring device 1 determines whether the boost stop Flag indicates "TRUE," which means that the boost control of the impulse voltage Vin is stopped.

[0168] Then, if the boost stop flag indicates "TRUE", the measurement device 1 terminates the RPDIV measurement process and returns to the processing procedure of the measurement method shown in Figure 7, because the voltage control of the impulse voltage Vin has been switched to a decrease control. On the other hand, if the boost stop flag indicates "FALSE", the measurement device 1 maintains the increase control and proceeds to step S25.

[0169] In step S25, the measuring device 1 sets a new impulse voltage Vin by adding an increase amount ΔV to the value set for the impulse voltage Vin. That is, the measuring device 1 performs the boost control operation 31 to increase the impulse voltage Vin.

[0170] In step S13, the measuring device 1 performs the repeated discharge measurement process shown in Figure 9.

[0171] Thus, the measuring device 1 increases the impulse voltage Vin applied multiple times to the object to be measured 2 until the discharge ratio Rd becomes equal to or greater than the boost threshold T1r, or until the boost stop condition is met. In other words, steps S21 to S25 correspond to a boost control step in which the impulse voltage Vin is gradually increased each time the impulse voltage Vin is repeatedly applied to the object to be measured 2.

[0172] If the discharge ratio Rd becomes equal to or greater than the boost threshold T1r in step S23, the measuring device 1 proceeds to step S26.

[0173] In step S26, the measuring device 1 sets the value of the impulse voltage Vin when the discharge ratio Rd becomes equal to or greater than the boost threshold T1r as RPDIV. That is, the measuring device 1 obtains RPDIV, which represents the value of the impulse voltage Vin when the discharge ratio Rd first becomes equal to or greater than the boost threshold T1r.

[0174] Once the processing in step S26 is completed, the process returns to the measurement method shown in Figure 7, and the RPDIV measurement process in step S2 of the measurement method is completed.

[0175] Figure 11 is a flowchart showing an example of the processing procedure for the loopback measurement process performed in step S4.

[0176] In step S41, the measuring device 1 sets a new impulse voltage Vin by adding an increase amount ΔV to the value set for the impulse voltage Vin, similar to step S14 shown in Figure 8. That is, the measuring device 1 performs the boost control operation 31 to increase the impulse voltage Vin.

[0177] In step S13, the measuring device 1 performs the repeated discharge measurement process shown in Figure 9.

[0178] In step S42, the measuring device 1 determines whether the boost stop condition for stopping the rise control of the impulse voltage Vin has been met. In this embodiment, a switching threshold Tsw related to the discharge ratio Rd is set as the boost stop condition. For example, the switching threshold Tsw is set to a value greater than the boost threshold T1r.

[0179] In this embodiment, if the discharge ratio Rd has not reached the switching threshold Tsw, the measuring device 1 returns to step S41 and increases the value of the impulse voltage Vin that is repeatedly applied to the object to be measured 2 until the discharge ratio Rd reaches the switching threshold Tsw. Alternatively, the measuring device 1 may return to step S41 if the impulse voltage Vin has not reached a predetermined upper limit voltage Vt and the discharge ratio Rd has not reached the switching threshold Tsw.

[0180] In other words, steps S41, S13, and S42 correspond to boost control steps that gradually increase the impulse voltage Vin each time the impulse voltage Vin is repeatedly applied to the object to be measured 2.

[0181] If the discharge ratio Rd reaches the switching threshold Tsw in step S42, the measuring device 1 determines that the boost-stop condition has been met and proceeds to step S43. Alternatively, the measuring device 1 may determine that the boost-stop condition has been met when the discharge peak value exceeds a predetermined allowable value To.

[0182] In step S43, the measuring device 1 stops controlling the impulse voltage Vin to rise when the discharge ratio Rd reaches the switching threshold Tsw, and switches to controlling the impulse voltage Vin to fall.

[0183] In other words, steps S42 and S43 correspond to stopping the control of increasing the impulse voltage Vin based on a state index indicating the occurrence state of partial discharge detected for each value of the impulse voltage Vin.

[0184] Once the processing in step S43 is completed, the process returns to the measurement method shown in Figure 7, and the reverse measurement process in step S4 of the measurement method is completed.

[0185] Figure 12 is a flowchart showing an example of the processing procedure for the RPDEV measurement process performed in step S6.

[0186] In step S61, the measuring device 1 determines whether the impulse voltage Vin falls below a predetermined lower limit. This lower limit is set to the initial value V1 plus a reduction amount ΔV (V1+ΔV) so that when the impulse voltage Vin is reduced by one step, it does not fall below the initial value V1.

[0187] If the impulse voltage Vin falls below the lower limit (V1+ΔV), the measuring device 1 returns to the processing procedure of the measurement method shown in Figure 7 and completes the RPDEV measurement process in step S6 of the measurement method. On the other hand, if the impulse voltage Vin is equal to or greater than the lower limit (V1+ΔV), the measuring device 1 proceeds to step S62.

[0188] In step S62, the measuring device 1 sets a new impulse voltage Vin to a voltage value obtained by subtracting the reduction amount ΔV from the value set for the impulse voltage Vin. That is, the measuring device 1 performs a downward control of the impulse voltage Vin by the step-down control unit 32.

[0189] In step S13, the measuring device 1 performs the repeated discharge measurement process shown in Figure 9.

[0190] In step S63, the measuring device 1 determines whether the discharge ratio Rd has fallen below the above-mentioned step-down threshold T2r.

[0191] Then, if the discharge ratio Rd is greater than or equal to the step-down threshold T2r, the measuring device 1 lowers the value of the impulse voltage Vin that is repeatedly applied to the object to be measured 2 until the discharge ratio Rd falls below the step-down threshold T2r.

[0192] In other words, steps S62, S13, and S63 correspond to step-down control steps that gradually decrease the impulse voltage Vin each time the impulse voltage Vin is repeatedly applied to the object to be measured 2.

[0193] If the discharge ratio Rd is less than the step-down threshold T2r in step S63, the measuring device 1 proceeds to step S64.

[0194] In step S64, the measuring device 1 sets the value of the impulse voltage Vin when the discharge ratio Rd falls below the step-down threshold T2r as RPDEV. That is, the measuring device 1 obtains RPDEV, which represents the value of the impulse voltage Vin when the discharge ratio Rd first becomes equal to or greater than the step-down threshold T2r.

[0195] In step S65, the measuring device 1 sets the value of the impulse voltage Vin when the discharge ratio Rd falls below the step-down threshold T2r as the reference RPDEV for determining the validity of the RPDEV.

[0196] Once step S65 is completed, the measuring device 1 returns to the processing procedure of the measurement method shown in Figure 7 and completes the RPDEV measurement process of step S6 in the measurement method.

[0197] Figure 13 is a flowchart showing an example of the processing procedure for the PDEV measurement process performed in step S7.

[0198] First, in step S71, the measuring device 1 determines whether the impulse voltage Vin is below the initial value V1. If the impulse voltage Vin is below the initial value V1, the measuring device 1 returns to the processing procedure of the measurement method shown in Figure 7 and completes the PDEV measurement process in step S7 of the measurement method. On the other hand, if the impulse voltage Vin is equal to or greater than the initial value V1, the measuring device 1 proceeds to step S72.

[0199] In step S72, the measuring device 1 determines whether the discharge ratio Rd has become 0% in order to measure PDEV.

[0200] In other words, the measuring device 1 determines whether the discharge ratio Rd has fallen below the extinction threshold T2. This extinction threshold T2 represents the discharge ratio when only one partial discharge is detected during the number of repeated applications. If the discharge ratio Rd becomes 0%, the measuring device 1 proceeds to step S73.

[0201] In step S73, the measuring device 1 determines whether or not there is a voltage value in PDEV in order to identify the value of the impulse voltage Vin when the discharge ratio Rd first becomes 0% during descent control.

[0202] If PDEV shows "No Data", the measuring device 1 determines that the value of the impulse voltage Vin is the voltage value when the discharge ratio Rd first became 0%, and proceeds to step S74. On the other hand, if a voltage value has already been set in PDEV, the number of times the discharge ratio Rd has become 0% is two or more, so the measuring device 1 skips step S74 and proceeds to step S75.

[0203] In step S74, the measuring device 1 sets the value of the impulse voltage Vin at the time the discharge ratio Rd first becomes 0% as the PDEV. That is, the measuring device 1 obtains the PDEV which represents the value of the impulse voltage Vin at the time the discharge ratio Rd first falls below the extinction threshold T2.

[0204] In step S75, the measuring device 1 performs a reference voltage update process to update the reference PDEV voltage value set in step S73 and the reference RPDEV voltage value set in step S65 of Figure 12 as needed. This reference voltage update process will be described later with reference to Figure 14.

[0205] In step S76, the measuring device 1 sets a new value for the impulse voltage Vin by subtracting the decrease amount ΔV from the value set for the impulse voltage Vin. In other words, the measuring device 1 performs a downward control of the impulse voltage Vin.

[0206] In step S77, the measuring device 1 determines whether the impulse voltage Vin has decreased to the termination voltage value Ve. The termination voltage value Ve may be the same as the starting voltage value Vs, or it may be a different value.

[0207] In this embodiment, the initial value V1 from step S11 in Figure 8 is used as the termination voltage value Ve. If the impulse voltage Vin is greater than or equal to the initial value V1, the measuring device 1 proceeds to step S13.

[0208] In step S13, the measuring device 1 performs the repeated discharge measurement process shown in Figure 9.

[0209] In step S78, the measuring device 1 determines whether the non-discharge voltage reduction amount, which indicates the magnitude of the voltage range of the impulse voltage Vin in which the discharge ratio Rd is continuously 0%, is greater than the stop threshold Ts. The stop threshold Ts is a predetermined value, and is set, for example, to the voltage amount when the impulse voltage Vin is reduced five times (=ΔV × 5).

[0210] Then, if the non-discharge voltage reduction amount is greater than the stop threshold Ts, the measuring device 1 stops the control of the impulse voltage Vin to decrease. In other words, the circuit control unit 33 in the measuring device 1 stops the control of the impulse voltage to decrease if the non-discharge voltage reduction amount is greater than a predetermined value when the impulse voltage Vin is being gradually reduced by the voltage reduction control unit 32.

[0211] On the other hand, if the non-discharge voltage reduction amount is less than or equal to the stop threshold Ts, the measuring device 1 repeats the process of steps S71 to S77 until the non-discharge voltage reduction amount exceeds the stop threshold Ts, or until the impulse voltage Vin drops to the initial value V1.

[0212] If the non-discharge voltage reduction amount exceeds the stop threshold Ts in step S78, or if the impulse voltage Vin falls below the initial value V1 in step S76, the measuring device 1 returns to the processing procedure of the measurement method shown in Figure 7 and completes the PDEV measurement process in step S7 of the measurement method.

[0213] In this embodiment, the process in step S77 is performed in order to shorten the measurement time, but the process in step S78 may be omitted.

[0214] Figure 14 is a flowchart showing an example of the processing procedure for the reference voltage update process performed in step S75.

[0215] In step S751, the measuring device 1 checks whether the discharge ratio Rd has become 0% in order to determine whether the reference RPDEV needs to be updated. That is, the measuring device 1 determines whether the discharge ratio Rd has fallen below the above-mentioned extinction threshold T2. If the discharge ratio Rd has exceeded the threshold, the measuring device 1 proceeds to step S742.

[0216] In step S752, the measuring device 1 erases the voltage value in the reference PDEV in order to record that the discharge ratio Rd has exceeded 0%. That is, the measuring device 1 resets the reference PDEV.

[0217] On the other hand, if the discharge ratio Rd becomes 0% in step S751, the measuring device 1 proceeds to step S753.

[0218] In step S753, the measuring device 1 determines whether the discharge ratio Rd has become 0% when the impulse voltage Vin is lowered by one step when the discharge ratio Rd is above 0%, by determining whether there is a voltage value in the reference PDEV.

[0219] If PDEV shows "No Data", the measuring device 1 determines that the discharge ratio Rd has become 0% when the impulse voltage Vin, which is used when the discharge ratio Rd is above 0%, is lowered by one step, and proceeds to step S744. On the other hand, if a voltage value has already been set for PDEV, the measuring device 1 skips step S744 and proceeds to step S745.

[0220] In step S754, the measuring device 1 sets the value of the impulse voltage Vin when the discharge ratio Rd becomes 0% as the reference PDEV, after lowering the impulse voltage Vin by one step when the discharge ratio Rd is above 0%.

[0221] Thus, the measuring device 1 updates the voltage value of the reference PDEV when the discharge ratio Rd falls below the extinction threshold T2, with the impulse voltage Vin lowered by one step when the discharge ratio Rd becomes 0%.

[0222] Ultimately, the smallest voltage value of the impulse voltage Vin when the discharge ratio Rd falls below the extinction threshold T2, after lowering the impulse voltage Vin by one step when the discharge ratio Rd is equal to or greater than the extinction threshold T2, is stored in the reference PDEV.

[0223] In step S755, the measuring device 1 determines whether the discharge ratio Rd has fallen below the step-down threshold T2r. If the discharge ratio Rd is equal to or greater than the step-down threshold T2r, the measuring device 1 proceeds to step S756.

[0224] In step S756, the measuring device 1 erases the voltage value in the reference PDEV in order to record that the discharge ratio Rd has become equal to or greater than the step-down threshold T2r.

[0225] On the other hand, if the discharge ratio Rd falls below the step-down threshold T2r in step S745, the measuring device 1 proceeds to step S757.

[0226] In step S757, the measuring device 1 determines whether the discharge ratio Rd falls below the step-down threshold T2r when the impulse voltage Vin, which is greater than or equal to the step-down threshold T2r, is lowered, in order to determine whether the discharge ratio Rd falls below the step-down threshold T2r.

[0227] Then, if the reference RPDEV shows "No Data", the measuring device 1 determines that the discharge ratio Rd has fallen below the step-down threshold T2r when the impulse voltage Vin, which would otherwise be greater than or equal to the step-down threshold T2r, is lowered, and proceeds to step S748.

[0228] In step S758, the measuring device 1 sets the value of the impulse voltage Vin when the discharge ratio Rd falls below the step-down threshold T2r, after lowering the impulse voltage Vin by one step when the discharge ratio Rd is equal to or greater than the step-down threshold T2r, as reference RPDEV.

[0229] Thus, when the impulse voltage Vin, which is lowered by one step when the discharge ratio Rd becomes equal to or greater than the step-down threshold T2r, is lowered, the voltage value of the reference RPDEV is updated.

[0230] Ultimately, the smallest voltage value of the impulse voltage Vin when the discharge ratio Rd falls below the step-down threshold T2r, after the impulse voltage Vin is lowered by one step when the discharge ratio Rd is greater than or equal to the step-down threshold T2r, is stored in the reference RPDEV.

[0231] When the processing in step S756 or S758 is completed, or when the reference RPDEV indicates a voltage value in step S757, the measuring device 1 returns to the PDEV measurement process shown in Figure 13 and completes the reference voltage update process in step S75 of the PDEV measurement process.

[0232] Next, the result output processing of step S8 in the measurement method shown in Figure 7 will be explained with reference to Figure 15.

[0233] Figure 15 is a flowchart showing an example of the processing procedure for the result output processing performed in step S8.

[0234] In step S81, the measuring device 1 records the measurement results obtained in steps S1 to S7 in the storage unit 60.

[0235] The measurement results include the discharge ratio Rd, partial discharge peak value, PDIV, RPDIV, aliasing voltage value, PDEV, RPDEV, reference PDEV, and reference RPDEV obtained for each value of the impulse voltage Vin.

[0236] In step S82, the measuring device 1 displays the above measurement results on the screen of the display unit 10. For example, the display unit 10 displays the number of discharges or the discharge ratio Rd among the number of repeated applications of the impulse voltage Vin for each of PDIV, RPDIV, aliasing voltage value, PDEV, and RPDEV.

[0237] In step S83, the measuring device 1 determines whether the voltage values ​​of both the reference RPDEV and the RPDEV are equal. If the voltage values ​​are equal, the measuring device 1 proceeds to step S84; otherwise, it skips step S84 and proceeds to step S85.

[0238] In step S84, the measuring device 1 displays on the screen of the display unit 10 that there is a difference between the reference RPDEV and the voltage value of the RPDEV. This allows the user to determine the validity of the RPDEV voltage value by referring to the voltage value of the reference RPDEV.

[0239] For example, if there is a large difference between the voltage value of the reference RPDEV and the voltage value of the RPDEV, the user can understand the trend of the discharge ratio Rd during the step-down of the impulse voltage Vin and then treat the voltage value of the reference RPDEV as the RPDEV.

[0240] In step S85, the measuring device 1 determines whether the voltage values ​​of both the reference PDEV and the PDEV are equal. If the voltage values ​​of both are equal, the measuring device 1 proceeds to step S85.

[0241] In step S86, the measuring device 1 displays on the screen of the display unit 10 that there is a difference between the reference PDEV and the voltage value of the PDEV. This allows the user to determine the validity of the voltage value of the PDEV by referring to the voltage value of the reference PDEV.

[0242] For example, if there is a large difference between the voltage value of the reference PDEV and the voltage value of the PDEV, the user may treat the voltage value of the reference PDEV as the PDEV after understanding the trend of the discharge ratio Rd during the step-down of the impulse voltage Vin.

[0243] If the process in step S86 is completed, or if the voltage values ​​of both the reference PDEV and PDEV are equal in step S85, the measuring device 1 returns to the measurement method shown in Figure 7, completes the result output processing in step S8, and ends the series of processing steps for the measurement method.

[0244] The effects and advantages of this embodiment will be described in detail below.

[0245] In this embodiment, the measuring device 1 measures the voltage involved in the occurrence of partial discharge in an object to be measured 2, which is composed of one or more coils L1 to L3. The measuring device 1 includes an application circuit 40 that repeatedly applies an impulse voltage Vin to the object to be measured 2, and a detection circuit 50 that detects the partial discharge occurring in the object to be measured 2 based on the voltage signal generated in the object to be measured 2 by the application circuit 40. Furthermore, the measuring device 1 includes a calculation unit 30B, a boost control unit 31, a buck control unit 32, and a circuit control unit 33.

[0246] The boost control unit 31 functions as a boost control means that controls the operation of the application circuit 40 so that the impulse voltage Vin increases in steps each time the impulse voltage Vin is repeatedly applied to the object to be measured 2. The circuit control unit 33 functions as a stop means that stops the boost control unit 31's control of increasing the impulse voltage Vin based on a state index indicating the occurrence state of partial discharge detected for each value of the impulse voltage Vin.

[0247] The step-down control unit 32 functions as a step-down control means that controls the operation of the application circuit 40 so that the impulse voltage Vin decreases in steps when the step-up control is stopped by the circuit control unit 33. The calculation unit 30B functions as a processing means that acquires the number of times partial discharge is detected in the object to be measured 2 out of multiple attempts for each value of the impulse voltage Vin.

[0248] Furthermore, in this embodiment, the measurement method for measuring the voltage related to the occurrence of partial discharge in the object to be measured 2 includes steps S18, S25 and S41, steps S42 and S43, steps S62 and S76, and steps S131 to S133.

[0249] Step S131 corresponds to an application step in which an impulse voltage is repeatedly applied to the object to be measured 2, and step S132 corresponds to a detection step in which a partial discharge occurring in the object to be measured 2 is detected based on the voltage signal generated in the object to be measured 2 by step S131. Steps S18, S25, and S41 correspond to boost control steps in which the impulse voltage Vin is gradually increased each time the impulse voltage Vin is repeatedly applied to the object to be measured 2.

[0250] Furthermore, steps S42 and S43 correspond to a stop step in which the control of increasing the impulse voltage Vin is stopped based on a state index indicating the occurrence state of partial discharge detected for each value of the impulse voltage Vin. Steps S62 and S76 correspond to a step-down control step in which the impulse voltage Vin is gradually decreased when the control of increasing the impulse voltage is stopped by steps S42 and S43. In addition, step S133 corresponds to a processing step in which the number of times partial discharge was detected in the object being measured 2 out of multiple times for each value of the impulse voltage Vin is obtained.

[0251] In this embodiment, the program is executed on a computer that controls the application circuit 40 and the detection circuit 50 to measure the voltage involved in the occurrence of partial discharge in the object to be measured 2. This program includes steps S18, S25, and S41, steps S42 and S43, steps S62 and S76, and step S133.

[0252] Steps S18, S25, and S41 correspond to boost control steps that control the operation of the application circuit 40 so that the impulse voltage Vin increases in stages each time the impulse voltage Vin is repeatedly applied to the object to be measured 2. Steps S42 and S43 correspond to stop steps that stop the impulse voltage increase control based on a state index indicating the occurrence state of partial discharge detected for each value of the impulse voltage Vin.

[0253] Furthermore, steps S62 and S76 correspond to step-down control steps that control the operation of the application circuit 40 so that the impulse voltage Vin decreases in stages when the rise control is stopped by steps S42 and S43. Step S133 corresponds to a processing step that acquires the number of times partial discharge is detected in the object to be measured 2 out of multiple attempts for each value of the impulse voltage Vin.

[0254] With these configurations, the upward control of the impulse voltage Vin applied to the object being measured 2 is stopped using a state index that indicates the state of partial discharge in the object being measured 2. Therefore, it is possible to stop the upward control of the impulse voltage Vin when the state of partial discharge in the object being measured 2 is a state that adversely affects the characteristics of the object being measured 2.

[0255] Therefore, it is possible to suppress the application of excessive voltage depending on the characteristics of the object being measured 2. As a result, even when controlling the decrease of the impulse voltage Vin, it is possible to measure the voltage related to the partial discharge of the object being measured 2 while suppressing the effect of excessive applied voltage on the object being measured 2.

[0256] Therefore, it is possible to measure the state of partial discharge in the object being measured 2 while suppressing the application of excessive voltage according to the characteristics of the object being measured 2.

[0257] Furthermore, in this embodiment, the calculation unit 30B determines the discharge ratio Rd for each value of the impulse voltage Vin from the boost control unit 31, and obtains a first voltage value that indicates the magnitude of the impulse voltage when the discharge ratio Rd becomes equal to or greater than a first threshold. Examples of the first voltage value include PDIV, which indicates the partial discharge initiation voltage, and RPDIV, which indicates the repeated partial discharge initiation voltage. If the first voltage value corresponds to PDIV, the first threshold corresponds to the initiation threshold T1 described above, and if the first voltage value corresponds to RPDIV, the first threshold corresponds to the boost threshold T1r described above.

[0258] Then, when the impulse voltage Vin rises to a value greater than the first voltage value by the boost control unit 31, the circuit control unit 33 stops controlling the rise of the impulse voltage Vin based on the partial discharge state index in the object being measured 2.

[0259] This configuration makes it possible to understand the upward trend of the discharge ratio Rd when the impulse voltage Vin is higher than the first voltage value. This allows the user to confirm whether the acquired first voltage value represents a situation where the discharge ratio Rd is increasing monotonically, a situation where the discharge ratio Rd is increasing suddenly, or a situation where the degree of increase in the discharge ratio Rd is increasing rapidly or gradually.

[0260] Furthermore, by using an index of the partial discharge state in the object being measured 2, it is possible to avoid continuously applying an excessive impulse voltage to the object being measured 2. Therefore, it is possible to determine the validity of the acquired first voltage value while suppressing the application of excessive voltage to the object being measured 2.

[0261] Furthermore, the PD frequency acquisition unit 35 of the calculation unit 30B in this embodiment acquires the discharge ratio Rd for each value of the impulse voltage Vin by the boost control unit 31 as the above-mentioned state indicator, and the circuit control unit 33 stops the control of increasing the impulse voltage Vin when the discharge ratio Rd reaches a predetermined threshold Tsw which is greater than the first threshold.

[0262] In this configuration, the discharge ratio Rd is used as a state indicator to determine whether or not to stop the control of the increase in the impulse voltage Vin. Since the discharge ratio Rd is a state indicator that shows the average state of partial discharge, noise components caused by the accidentality of partial discharge are reduced.

[0263] Therefore, it is possible to accurately determine the effect of the applied voltage on the object being measured 2. Consequently, it is possible to avoid situations where the control of the increase in the impulse voltage Vin is stopped due to a partially discharge that occurs accidentally.

[0264] Furthermore, in this embodiment, the PD frequency acquisition unit 35 measures the peak voltage signal caused by partial discharge of the object being measured 2 for each value of the impulse voltage Vin controlled by the boost control unit 31, as a state indicator. The circuit control unit 33 then stops the control of increasing the impulse voltage Vin when the discharge peak value, which indicates the peak voltage signal caused by partial discharge, exceeds the allowable value To.

[0265] In this configuration, the discharge peak value is used as a state indicator to determine whether or not to stop the control of the rise in the impulse voltage Vin. The discharge peak value is a state indicator that shows the individual occurrence state of partial discharge, and can directly detect the risk of damage to the object being measured 2 due to the applied voltage.

[0266] Therefore, it is possible to accurately determine the adverse effects of the applied voltage on the object being measured 2. Consequently, it is possible to avoid dielectric breakdown or damage to the object being measured 2 caused by the applied voltage.

[0267] Furthermore, the calculation unit 30B in this embodiment acquires the value of the impulse voltage when the discharge ratio Rd first falls below the second threshold as the second voltage value. Examples of the second voltage value include PDEV, which represents the partial discharge extinction voltage, and RPDEV, which represents the repeated partial discharge extinction voltage. If the second voltage value corresponds to PDEV, the second threshold corresponds to the extinction threshold T2 mentioned above, and if the second voltage value corresponds to RPDEV, the second threshold corresponds to the step-down threshold T2r mentioned above.

[0268] The calculation unit 30B then acquires the lowest voltage value among multiple impulse voltages when the discharge ratio Rd falls below the second threshold, in a state where the impulse voltage Vin, which is lowered by one step when the discharge ratio Rd is above the second threshold, is lowered by the step-down control unit 32, as the associated voltage value related to the second voltage value.

[0269] With this configuration, by comparing the second voltage value with the related voltage value, it is possible to infer whether the acquired second voltage value is the voltage value when partial discharge weakens regularly as the impulse voltage decreases, the voltage value when a weak partial discharge occurs accidentally, or the voltage value when the degree of decrease in the discharge ratio Rd increases or decreases rapidly. In other words, the validity of the second voltage can be evaluated.

[0270] Furthermore, the measuring device 1 in this embodiment further includes a display unit 10 as a display means for displaying the second voltage value and the related voltage value. This allows the user to understand the validity of the second voltage value.

[0271] Furthermore, the second voltage value in this embodiment is the RPDEV (Repeated Partial Discharge Extinction Voltage). Therefore, the aforementioned related voltage value corresponds to the reference RPDEV, and the user can determine the validity of the RPDEV by comparing the reference RPDEV with the RPDEV.

[0272] Furthermore, the second voltage value in this embodiment is the PDEV (partial discharge extinction voltage). Therefore, the aforementioned related voltage value corresponds to the reference PDEV, and the user can determine the validity of the PDEV by comparing it with the reference PDEV.

[0273] Furthermore, in this embodiment, the measuring device 1 includes a display unit 10 as an output means for outputting the results obtained by the calculation unit 30B. The calculation unit 30B acquires a third voltage value, which is a folded voltage value indicating the magnitude of the impulse voltage Vin when the circuit control unit 33 stops controlling the rise of the impulse voltage Vin. For each of the first to third voltage values ​​acquired by the calculation unit 30B, the display unit 10 displays the number of discharges or the discharge ratio Rd among the number of repeated applications of the impulse voltage Vin.

[0274] With this configuration, the number of discharges or the discharge ratio Rd at the first to third voltage values ​​obtained by the calculation unit 30B is displayed, so that the user can understand their validity based on, for example, the symmetry between the first and third voltage values.

[0275] Furthermore, in this embodiment, the circuit control unit 33 determines whether the magnitude of the voltage range of the impulse voltage Vin in which the discharge ratio Rd is continuously 0 percent (for example, the amount of voltage reduction mentioned above) is greater than a predetermined value when the impulse voltage Vin is being gradually reduced by the step-down control unit 32. If the magnitude of the voltage range of the impulse voltage Vin in which the discharge ratio Rd is continuously 0 percent is greater than a predetermined value, the circuit control unit 33 stops the step-down control of the impulse voltage Vin.

[0276] This configuration makes it possible to complete the measurement process without lowering the impulse voltage Vin to the end voltage value of the sweep range. Therefore, it is possible to shorten the measurement time while avoiding the unnecessary application of the impulse voltage Vin to the object being measured 2.

[0277] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0278] For example, it is conceivable that the impulse voltage Vin when the boost control unit 31 stops increasing the impulse voltage Vin may be equivalent to RPDEV. In such a case, the circuit control unit 33 controls the operation of the application circuit 40 so that the impulse voltage Vin becomes a predetermined voltage value greater than RPDEV, and the PD index acquisition unit 36 ​​acquires the discharge ratio Rd at that predetermined voltage value. By acquiring the discharge ratio Rd at a predetermined voltage value, the validity of RPDEV can be evaluated to some extent.

[0279] Furthermore, in this embodiment, the boost stop condition in steps S14, S21, and S41 was determined by whether or not the discharge ratio Rd reached the switching threshold Tsw. However, the boost stop condition in this embodiment is not limited to this. For example, at least one of the following determinations may be made: whether or not the impulse voltage Vin has reached a predetermined upper limit voltage Vt, and whether or not the discharge ratio Rd has reached the switching threshold Tsw. In this case, the measuring device 1 determines that the boost stop condition has been met and stops controlling the increase of the impulse voltage Vin when either the determination that the impulse voltage Vin has reached a predetermined upper limit voltage Vt, or the determination that the discharge ratio Rd has reached the switching threshold Tsw, is made.

[0280] Alternatively, as a condition for stopping the boost, at least one of the following judgments may be made: whether the impulse voltage Vin has reached a predetermined upper limit voltage Vt, and whether the discharge peak value has exceeded a predetermined allowable value To. In this case, the measuring device 1 determines that the boost stop condition has been met and stops controlling the increase of the impulse voltage Vin when either the determination that the impulse voltage Vin has reached a predetermined upper limit voltage Vt, or the determination that the discharge peak value has exceeded a predetermined allowable value To, is made.

[0281] As other boost stop conditions, both a determination as to whether or not the discharge ratio Rd has reached the switching threshold value Tsw and a determination as to whether or not the discharge peak value has exceeded a predetermined allowable value To may be made. In this case, when either the determination that the discharge ratio Rd has reached the switching threshold value Tsw or the determination that the discharge peak value has exceeded the predetermined allowable value To is made, the measuring device 1 determines that the boost stop condition is satisfied and stops the control for increasing the impulse voltage Vin.

[0282] Also, in this embodiment, the measuring device 1 is provided with the display unit 10, the operation unit 20, the storage unit 60, and the communication unit 70, but all or at least one of the display unit 10, the operation unit 20, the storage unit 60, and the communication unit 70 may be omitted from the measuring device 1.

Description of Reference Numerals

[0283] 1 Measuring device 2 Object to be measured 10 Display unit (output means, display means) 30B Arithmetic unit (processing means) 31 Boost control unit (boost control means) 32 Buck control unit (buck control means) 33 Circuit control unit (stop means) 40 Application circuit 50 Detection circuit T1 Start threshold value (first threshold value) T1r Boost threshold value (first threshold value) T2 Extinction threshold value (second threshold value) T2r Buck threshold value (second threshold value) Tsw Switching threshold value To Allowable value

Claims

1. A measuring device for measuring the voltage involved in the occurrence of partial discharge in an object to be measured, which is composed of one or more coils, An application circuit that applies an impulse voltage to the object to be measured multiple times, A detection circuit that detects partial discharge occurring in the object to be measured based on a voltage signal generated in the object by the application circuit, A boost control means controls the operation of the application circuit so that the impulse voltage increases in steps each time the impulse voltage is repeatedly applied to the object to be measured, A stopping means for stopping the boost control means's control of increasing the impulse voltage based on a state index indicating the occurrence state of the partial discharge detected for each value of the impulse voltage, A step-down control means controls the operation of the application circuit so that the impulse voltage decreases in steps when the upward control is stopped by the stopping means, The processing means includes a method for obtaining the number of times a partial discharge was detected in the object being measured out of the multiple times for each value of the impulse voltage, The processing means is The ratio of the number of times is determined for each value of the impulse voltage by the step-down control means, and the value of the impulse voltage when the ratio first falls below the second threshold is obtained as the second voltage value. When the impulse voltage at which the ratio is equal to or greater than the second threshold is reduced by the step-down control means, the smallest voltage value among the multiple impulse voltages at which the ratio falls below the second threshold is acquired as the associated voltage value related to the second voltage value. Measuring device.

2. A measuring device according to claim 1, The system further includes a display means for displaying the second voltage value and the associated voltage value. Measuring device.

3. A measuring device according to claim 1 or claim 2, The aforementioned second voltage value is the repeated partial discharge extinction voltage. Measuring device.

4. A measuring device according to claim 1 or claim 2, The aforementioned second voltage value is the partial discharge extinction voltage. Measuring device.

5. A measuring device according to claim 1, The system further includes an output means for outputting the results obtained by the processing means, The processing means acquires a third voltage value indicating the magnitude of the impulse voltage when the upward control is stopped by the stopping means, The output means displays the number of times or the ratio of the number of times for each of the second voltage value and the third voltage value. Measuring device.

6. A measuring device according to any one of claims 1 to 5, The stopping means stops the step-down control of the impulse voltage when the impulse voltage is being gradually reduced by the step-down control means, if the magnitude of the voltage range in which the ratio of the number of times is continuously 0 percent is greater than a predetermined value. Measuring device.

7. A measurement method for measuring the voltage involved in the occurrence of partial discharge in an object to be measured, which is composed of one or more coils, An application step of repeatedly applying an impulse voltage to the object to be measured multiple times, A detection step for detecting a partial discharge occurring in the object to be measured based on the voltage signal generated in the object to be measured by the application step, A boost control step is performed to gradually increase the impulse voltage each time the impulse voltage is applied to the object to be measured multiple times. A stop step that stops the boost control step from raising the impulse voltage based on a state index indicating the occurrence state of the partial discharge detected for each value of the impulse voltage, A step-down control step that gradually lowers the impulse voltage when the upward control is stopped by the stop step, The process includes a step of obtaining the number of times a partial discharge was detected in the object being measured out of the multiple times for each value of the impulse voltage, The processing step described above is: The ratio of the number of times is determined for each value of the impulse voltage obtained in the step down control, and the value of the impulse voltage when the ratio first falls below the second threshold is obtained as the second voltage value. When the impulse voltage at which the ratio is equal to or greater than the second threshold is reduced by the step-down control, the smallest voltage value among the multiple impulse voltages at which the ratio falls below the second threshold is acquired as the associated voltage value related to the second voltage value. Measurement method.

8. A computer controls an application circuit that repeatedly applies an impulse voltage to an object to be measured, which is composed of one or more coils, and a detection circuit that detects a partial discharge occurring in the object to be measured based on the voltage signal generated in the object by the application circuit, in order to measure the voltage related to the occurrence of a partial discharge in the object to be measured. A boost control step controls the operation of the application circuit so that the impulse voltage increases in steps each time the impulse voltage is repeatedly applied to the object to be measured. A stop step that stops the boost control step from raising the impulse voltage based on a state index indicating the occurrence state of the partial discharge detected for each value of the impulse voltage, A step-down control step controls the operation of the application circuit so that the impulse voltage decreases in stages when the upward control is stopped by the stop step, A program for causing a process to execute a processing step of obtaining the number of times a partial discharge was detected in the object to be measured out of the multiple times for each value of the impulse voltage, The processing step described above is: The ratio of the number of times is determined for each value of the impulse voltage obtained in the step down control, and the value of the impulse voltage when the ratio first falls below the second threshold is obtained as the second voltage value. When the impulse voltage at which the ratio is equal to or greater than the second threshold is reduced by the step-down control, the smallest voltage value among the multiple impulse voltages at which the ratio falls below the second threshold is acquired as the associated voltage value related to the second voltage value. program.

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