Partial discharge diagnostic device and partial discharge diagnostic method

Abstract

To provide a partial discharge diagnostic device and a partial discharge diagnostic method that can obtain information about tree-related deterioration.SOLUTION: A pulse identification unit identifies timings at which multiple pulses occur from a signal related to partial discharge generated in the electrical equipment to be diagnosed. A pulse group extraction unit extracts a pulse group generated due to treeing based on the timings at which the multiple pulses occur.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a partial discharge diagnostic device and a partial discharge diagnostic method. [Background technology]

[0002] A known method for diagnosing the deterioration state of electrical equipment due to partial discharge involves obtaining parameters such as the discharge occurrence frequency n, discharge charge amount q, and discharge occurrence phase φ from partial discharge signals detected by sensors, electrodes, etc., and diagnosing partial discharge based on the distribution of the obtained parameters (e.g., φ-q distribution or φ-qn distribution).

[0003] Partial discharges in electrical equipment can be caused by voids in insulating materials or tree-like breakdowns in insulating materials. When partial discharges burn the insulating material, the resin carbonizes. Because the carbonized area is conductive, further partial discharges cause the carbonization to progress gradually from the tip of the carbonized area toward the ground surface, resulting in the carbonized area growing in a tree-like pattern. Hereinafter, deterioration caused by treeing will also be referred to as tree-related deterioration. Tree-related deterioration occurs in the final stages of deterioration in electrical equipment. When treeing reaches the ground surface of the insulating material, a ground fault occurs, so technology to detect tree-related deterioration is needed to prevent equipment failure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-34696 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-128699 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-156239 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-33538 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-180747 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a partial discharge diagnostic device and a partial discharge diagnostic method that can obtain information about tree-related deterioration. [Means for solving the problem]

[0006] The partial discharge diagnostic device according to the embodiment includes a pulse identifying unit and a pulse group extracting unit. The pulse identifying unit identifies the timing of occurrence of multiple pulses from a signal related to partial discharge generated in the electrical equipment to be diagnosed. The pulse group extracting unit extracts a pulse group generated due to treeing based on the timing of occurrence of the multiple pulses. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a configuration for detecting partial discharge from inside boxes arranged side by side using a partial discharge diagnostic device according to an embodiment; [Figure 2] FIG. 1 is a first diagram showing the results of an experiment according to an embodiment. [Figure 3] FIG. 10 is a second diagram showing the results of an experiment according to the embodiment. [Figure 4] FIG. 2 is a functional block diagram showing the functional configuration of the partial discharge diagnostic device according to the embodiment. [Figure 5] 3 is a flowchart showing a diagnostic process of the partial discharge diagnostic device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a partial discharge diagnostic device and a partial discharge diagnostic method according to an embodiment will be described with reference to the drawings.

[0009] (First embodiment) FIG. 1 is a schematic diagram showing a configuration for detecting partial discharge from inside boxes arranged side by side using a partial discharge diagnostic device 100 of the first embodiment. In the first embodiment, the configuration is made up of a plurality of boxes 10 arranged side by side. The plurality of boxes 10 are arranged in a substantially straight line. A predetermined power supply system for supplying power to electrical equipment is provided in these boxes 10. Each box 10 is a box capable of housing electrical equipment such as switchgear. Each box 10 houses electrical equipment such as a circuit breaker or main circuit conductor. The electrical equipment generates partial discharge due to aging and other factors. An electrode 110 is fixed to the front of each box 10 so as to be in contact with the front of the box 10.

[0010] The electrode 110 detects the surface potential of the box 10. The electrode 110 outputs the detected surface potential as an electrical signal to the partial discharge diagnostic device 100. The electrode 110 may be provided, for example, in a state of semi-permanently contacting the box 10. The electrode 110 may also be provided in a form that temporarily contacts the box 10 only while an inspector or the like is performing an operation to determine whether or not partial discharge has occurred in the box 10. In the configuration shown in FIG. 1 , one electrode 110 is provided on the box 10, but multiple electrodes 110 may be provided on one box 10. By providing multiple electrodes 110 on one box 10, the partial discharge diagnostic device 100 can detect the surface potential of the box 10 with higher accuracy. This allows the partial discharge diagnostic device 100 to diagnose the state of the electrical equipment with higher accuracy.

[0011] A common ground bus 20 is disposed at the bottom of the box 10. The ground bus 20 is connected to a ground electrode 30. The box 10 is composed of a front panel, a ceiling panel, a rear panel, a floor panel, and side panels. These front panel, ceiling panel, rear panel, floor panel, and side panels are collectively referred to as the constituent panels of the box 10. In the example shown in FIG. 1, the electrode 110 is fixed in contact with the front panel, but the electrode 110 may also be fixed in contact with any of the other constituent panels. The constituent panels are connected to the ground bus 20.

[0012] In the present embodiment, a method of detecting a surface potential by the electrode 110 is described as a method of detecting a partial discharge signal, but the present invention is not limited to this. For example, the partial discharge diagnostic device 100 according to another embodiment may detect electromagnetic waves instead of the surface potential. In this case, the partial discharge diagnostic device 100 acquires an electrical signal from an antenna instead of the electrode 110. The antenna detects electromagnetic waves. The antenna outputs an electrical signal to the partial discharge diagnostic device 100 based on the detected electromagnetic waves. Furthermore, the partial discharge diagnostic device 100 according to another embodiment may detect a ground current instead of the surface potential. In this case, the partial discharge diagnostic device 100 acquires an electrical signal from a sensor such as a high-frequency CT (Current Transformer) instead of the electrode 110. The sensor detects the ground current. The sensor outputs an electrical signal to the partial discharge diagnostic device 100 based on the detected ground current. The partial discharge diagnostic device 100 may acquire other signals resulting from partial discharge in an electrical device. For example, the partial discharge diagnostic device 100 may acquire signals of a ground potential, electromagnetic waves, a ground wire current, vibration, sound, etc.

[0013] The partial discharge diagnostic device 100 according to the first embodiment diagnoses whether or not tree-related degradation has occurred in the electrical equipment inside the box 10, based on the electrical signals acquired from the electrodes 110. The reason why the presence or absence of tree-related degradation can be diagnosed from the electrical signals will be described below.

[0014] FIG. 2 is a first diagram showing the results of an experiment according to an embodiment. The inventors conducted an experiment to verify the difference between partial discharges caused by voids and partial discharges caused by trees. In the experiment, needle electrodes were placed on a first insulating resin sample having voids and a second insulating resin sample having trees, and partial discharges were generated by applying a voltage to the needle electrodes. Electrical signals were measured from the first insulating resin sample, and frequency analysis of the electrical signals was performed to create a spectrogram G1. Electrical signals were measured from the second insulating resin sample, and frequency analysis of the electrical signals was performed to create a spectrogram G2. The inventors compared spectrogram G1, which represents partial discharges caused by voids, with spectrogram G2, which represents partial discharges caused by trees. As shown in FIG. 2, the inventors found that, immediately after the occurrence of partial discharges caused by trees, frequency components above 100 MHz were strongly present, whereas frequency components above 100 MHz were hardly present in partial discharges caused by voids.

[0015] FIG. 3 is a second diagram showing the results of an experiment according to an embodiment. Furthermore, the inventors extracted frequency components above 100 MHz from the obtained electrical signal to obtain a high-frequency waveform and compared the high-frequency waveform of partial discharge caused by voids with the high-frequency waveform of partial discharge caused by treeing. As a result, the inventors found that, as shown in FIG. 3, multiple pulses occur within 5 μs in the high-frequency waveform of partial discharge caused by treeing. In particular, the inventors found that two pulses occur within 1 μs. When voltage occurs at the tree root, current flows through multiple branches of the tree. The length of the current route varies depending on the branch, and this is thought to result in a time difference in the timing of partial discharge pulse generation. Note that partial discharge caused by voids usually occurs at intervals of several tens of μs to several milliseconds at the rise or fall of the operating voltage, and multiple pulses do not occur within 5 μs.

[0016] Therefore, the partial discharge diagnostic device 100 can diagnose the presence or absence of tree-related degradation by determining the presence or absence of a group of pulses that occur in a short period of time in the high-frequency waveform.

[0017] FIG. 4 is a functional block diagram showing the functional configuration of a partial discharge diagnostic device 100 according to the first embodiment. The partial discharge diagnostic device 100 is an information processing device such as a PC, a smartphone, or a tablet computer. The partial discharge diagnostic device 100 diagnoses the state of an electrical device to be diagnosed based on an electrical signal received from an electrode 110. Specifically, the partial discharge diagnostic device 100 diagnoses the progress of a partial discharge and the type of the discharge source. The partial discharge diagnostic device 100 includes a communication unit 101, an input unit 102, an output unit 103, an electrical signal storage unit 104, a diagnostic information storage unit 105, and a control unit 106.

[0018] The communication unit 101 is a network interface that communicates with external devices via a network.

[0019] The input unit 102 is configured using an input device such as a touch panel, a mouse, and a keyboard. The input unit 102 may be an interface for connecting the input device to the partial discharge diagnostic apparatus 100. In this case, the input unit 102 generates input data from an input signal input to the input device and inputs the input data to the partial discharge diagnostic apparatus 100. The input data may be, for example, instruction information indicating an instruction to switch the electrical signal acquired by the partial discharge diagnostic apparatus 100 to another electrode 110.

[0020] The output unit 103 is an output device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, an organic EL (Electro Luminescence) display, etc. The output unit 103 may be an interface for connecting the output device to the partial discharge diagnostic apparatus 100. In this case, the output unit 103 generates a video signal from the video data and outputs the video signal to the video output device connected to itself.

[0021] The electric signal storage unit 104 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device. The electric signal storage unit 104 stores the date and time when the electric signal is acquired by the electrode 110 in association with the intensity of the electric signal. When the partial discharge diagnostic device 100 acquires electric signals from multiple electrodes 110, the electric signal storage unit 104 stores identification information of the electrode 110 in association with the date and time and the intensity. The identification information is information for identifying the electrode 110.

[0022] The diagnostic information storage unit 105 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device. The diagnostic information storage unit 105 stores a plurality of performance data. The performance data is information that associates the φ-q distribution of the electrical equipment with the degradation state. Details of the performance data will be described later.

[0023] The control unit 106 controls the operation of each unit of the partial discharge diagnostic apparatus 100. The control unit 106 is executed by a device including a processor such as a CPU (Central Processing Unit) and a RAM (Random Access Memory). The control unit 106 executes a partial discharge diagnostic program to function as an electric signal acquiring unit 161, a filter unit 162, a pulse identifying unit 163, a pulse group extracting unit 164, and a partial discharge diagnostic unit 165.

[0024] The electric signal acquiring unit 161 acquires an electric signal from the electrode 110. The electric signal acquiring unit 161 acquires a time series of the intensity of the electric signal, i.e., a signal waveform. The electric signal acquiring unit 161 associates waveform data representing the signal waveform with the acquisition time of the waveform data and records it in the electric signal storage unit 104. Note that if the partial discharge diagnostic device 100 has a plurality of electrodes 110, the electric signal acquiring unit 161 associates the waveform data with the acquisition time and identification information of the electrode 110 and records it in the electric signal storage unit 104.

[0025] The filter unit 162 removes low-frequency noise contained in the signal waveform acquired by the electrical signal acquisition unit 161 to obtain a high-frequency signal waveform. The filter unit 162 may be a high-pass filter that passes a frequency band that includes the partial discharge signal. The inventors have found through the above-mentioned experiment that extracting signal components of 100 MHz or higher is effective in capturing pulses of partial discharge caused by treeing, as shown in Figure 2.

[0026] The pulse identifying unit 163 identifies the timing and intensity of a pulse associated with partial discharge based on the high-frequency signal waveform obtained by the filter unit 162. For example, the pulse identifying unit 163 extracts a portion of the high-frequency signal waveform where the absolute value of the intensity exceeds a threshold, identifies the timing of the maximum or minimum of that portion as the timing of pulse generation, and identifies the intensity at that timing as the pulse generation intensity.

[0027] The pulse group extraction unit 164 extracts a pulse group generated due to tree structure from the multiple pulses identified by the pulse identification unit 163. Specifically, the pulse group extraction unit 164 extracts a continuous pulse group whose pulse generation interval is within 5 μs as a pulse group generated due to tree structure. Alternatively, the pulse group extraction unit 164 extracts multiple pulses contained within a time range of 5 μs as a pulse group generated due to tree structure. Note that a single pulse not extracted as a pulse group may be a pulse generated due to, for example, a void. The pulse group extracted by the pulse group extraction unit 164 is a pulse group consisting of multiple pulses generated from multiple branches of the tree structure.

[0028] The partial discharge diagnosis unit 165 diagnoses the presence or absence of tree-related degradation based on the extraction result of the pulse group extraction unit 164. Specifically, the partial discharge diagnosis unit 165 may diagnose that tree-related degradation has occurred in the electrical equipment when the pulse group extraction unit 164 extracts more than a predetermined number of pulse groups. The number of extracted pulses that serves as a threshold for determining the presence or absence of tree-related degradation may be one or more. Furthermore, the partial discharge diagnosis unit 165 may diagnose that tree-related degradation has occurred in the electrical equipment based on the ratio between the total number of extracted pulses and the number of pulses that make up a pulse group. Furthermore, when the partial discharge diagnostic unit 165 determines that tree-related degradation has occurred, it diagnoses the degree of degradation based on the φ-q distribution generated from the extracted pulse group and the performance data related to tree-related discharge stored in the diagnostic information storage unit 105. When the partial discharge diagnostic unit 165 determines that tree-related degradation has not occurred, it diagnoses the degree of degradation based on the φ-q distribution generated from the extracted pulse group and the performance data related to void-related discharge stored in the diagnostic information storage unit 105.

[0029] Here, a description will be given of the performance data stored in the diagnostic information storage unit 105. The diagnostic information storage unit 105 stores performance data relating to void discharge and performance data relating to tree discharge. The performance data related to void discharges is data that associates the φ-q distribution of pulses due to partial discharges generated from electrical equipment whose degradation state is known with the degradation state of the electrical equipment. The performance data related to tree discharges is data that associates the φ-q distribution of pulse groups due to partial discharges generated from electrical equipment whose degradation state is known with the degradation state of the electrical equipment. The φ-q distribution of a pulse group represents, for example, the φ-q distribution of a representative pulse of the pulse group. The representative pulse may be the first pulse to occur, the pulse with the highest power, the average of multiple pulses, etc.

[0030] The partial discharge diagnosis unit 165 compares the φ-q distribution of the electric equipment to be diagnosed with the φ-q distribution related to the actual data, identifies the degradation state corresponding to the closest φ-q distribution, and diagnoses the degradation state of the electric equipment to be diagnosed. For example, the partial discharge diagnosis unit 165 may identify the degradation state using a trained model that has been trained using actual data related to void discharge as a training data set. In this case, the trained model is trained using the φ-q distribution related to the actual data as input samples and the degradation state as output samples. Furthermore, for example, the partial discharge diagnosis unit 165 may diagnose that there is a high possibility of a malfunction when the average value of the voltage phase φ falls within a predetermined range or when the average value of the discharge charge amount q exceeds a threshold value.

[0031] 5 is a flowchart showing the diagnostic processing of the partial discharge diagnostic device 100 according to the first embodiment. The electrical signal acquiring unit 161 of the partial discharge diagnostic device 100 acquires electrical signals from the electrodes 110 while the electric power equipment is operating, and records waveform data representing the signal waveforms of the electrical signals in association with time in the electrical signal storage unit 104. As a result, the waveform data is accumulated in the electrical signal storage unit 104.

[0032] When the partial discharge diagnostic device 100 starts diagnostic processing in response to an instruction from an administrator or the like, the filter unit 162 extracts a high-frequency signal waveform related to a frequency component of 100 MHz or higher from the waveform data recorded in the electrical signal storage unit 104 (step S1). The pulse identification unit 163 identifies the occurrence timing and occurrence intensity of a pulse related to partial discharge based on the high-frequency signal waveform (step S2). The pulse group extraction unit 164 extracts a continuous pulse group whose pulse occurrence interval is within 5 μsec from the multiple pulses identified by the pulse identification unit 163. As a result, the pulse group extraction unit 164 classifies the multiple pulses identified in step S2 into single pulses and pulse groups (step S3).

[0033] The partial discharge diagnostic unit 165 determines whether the pulse group extraction unit 164 extracted a pulse group exceeding the threshold value in step S3 (step S4). If the partial discharge diagnostic unit 165 determines that a pulse group exceeding the threshold value has not been extracted (step S4: NO), the partial discharge diagnostic unit 165 generates a φ-q distribution based on the pulses classified as single pulses in step S3 (step S5). The partial discharge diagnostic unit 165 diagnoses the degradation state of the electric power equipment based on the generated φ-q distribution and the performance data related to void discharge stored in the diagnostic information storage unit 105 (step S6). The partial discharge diagnostic unit 165 causes the output unit 103 to output the degradation state of the electric power equipment (step S7). The information output from the output unit 103 includes the fact that no tree degradation has occurred in the electric power equipment and the degradation state diagnosed in step S6.

[0034] If the partial discharge diagnostic unit 165 determines that a pulse group exceeding the threshold value has been extracted (step S4: YES), it generates a φ-q distribution based on the multiple pulse groups extracted in step S3 (step S8). The partial discharge diagnostic unit 165 diagnoses the degradation state of the electric power equipment based on the generated φ-q distribution and performance data related to tree discharge stored in the diagnostic information storage unit 105 (step S9). The partial discharge diagnostic unit 165 causes the output unit 103 to output the degradation state of the electric power equipment (step S10). The information output from the output unit 103 includes the occurrence of tree degradation in the electric power equipment and the degradation state diagnosed in step S9.

[0035] As described above, the partial discharge diagnostic device 100 according to the first embodiment executes the following processes. The pulse identifying unit 163 identifies the timing of occurrence of multiple pulses from a signal related to partial discharge generated in the electrical equipment to be diagnosed. The pulse group extracting unit 164 extracts a pulse group generated due to treeing based on the timing of occurrence of the multiple pulses. As described above, the inventors have discovered that when tree-related degradation occurs in electrical equipment, multiple pulses are generated consecutively within a short period of time. From this discovery, the partial discharge diagnostic device 100 according to the first embodiment can obtain a pulse group that is useful for determining whether tree-related degradation exists.

[0036] Furthermore, the partial discharge diagnostic device 100 according to the first embodiment can obtain an appropriate φ-q distribution that represents the state of an electrical device suffering from tree-related degradation by creating a φ-q distribution based on the representative value of a pulse group caused by treeing. It is presumed that one pulse group represents the characteristics of the same tree, and if all pulses of the pulse group are applied to φ-q in the φ-q distribution, the influence of the number of pulses constituting the pulse group will be excessive, making it impossible to perform an appropriate diagnosis.

[0037] Although the partial discharge diagnostic device 100 according to the above embodiment diagnoses the state of the electrical equipment based on the φ-q distribution, this is not limiting. For example, the partial discharge diagnostic device 100 according to other embodiments may diagnose the state of the electrical equipment based on the φ-qn distribution, or may diagnose the state of the electrical equipment based only on the voltage phase φ or the discharge charge amount q. In other words, the partial discharge diagnostic device 100 diagnoses the state of the electrical equipment based on at least one piece of information on the pulse generation intensity, generation time, and generation phase.

[0038] The partial discharge diagnostic device 100 according to the first embodiment diagnoses power receiving and distribution equipment such as a switchgear housed in the box 10, but is not limited to this. For example, the partial discharge diagnostic device 100 according to other embodiments may diagnose other electrical equipment such as electrical equipment having a molded coil (molded transformer, rotating machine, generator, motor, etc.). In this case as well, by attaching the electrode 110 to a grounded portion of the housing that houses the electrical equipment to be diagnosed, the partial discharge diagnostic device 100 can diagnose the state of the electrical equipment.

[0039] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0040] 10...Box body 100...Partial discharge diagnostic device 101...Communication unit 102...Input unit 103...Output unit 104...Electrical signal storage unit 105...Diagnosis information storage unit 106...Control unit 110...Electrode 161...Electrical signal acquisition unit 162...Filter unit 163...Pulse identification unit 164...Pulse group extraction unit 165...Partial discharge diagnostic unit 20...Grounding bus bar 30...Grounding electrode

Claims

1. a pulse identifying unit that identifies timings at which a plurality of pulses are generated from a signal related to partial discharge generated from the electrical equipment to be diagnosed; a pulse group extracting unit that extracts a pulse group generated due to treeing based on the generation timings of the plurality of pulses; A partial discharge diagnostic device comprising:

2. the pulse group extraction unit extracts the pulse group consisting of a plurality of pulses generated from a plurality of branches of the tree; The partial discharge diagnostic device according to claim 1 .

3. the pulse group extraction unit extracts the pulse group consisting of two or more pulses generated within 5 μsec from the plurality of pulses; The partial discharge diagnostic device according to claim 1 .

4. the pulse group extraction unit extracts the pulse group consisting of pulses whose occurrence intervals are within 5 μsec from the plurality of pulses; The partial discharge diagnostic device according to claim 1 .

5. a diagnostic unit that diagnoses a state of the electrical equipment based on the group of pulses; The partial discharge diagnostic device according to claim 1 , comprising:

6. the diagnosing unit diagnoses the state of the electrical device based on the number of pulses constituting the pulse group or the ratio of the number of pulses constituting the pulse group to the number of the plurality of pulses. The partial discharge diagnostic device according to claim 5.

7. the diagnosing unit diagnoses the state of the electrical equipment based on at least one piece of information regarding an intensity, a time of occurrence, and a phase of occurrence of a representative value of the pulse group. The partial discharge diagnostic device according to claim 5.

8. the diagnosing unit diagnoses the state of the electrical equipment based on performance data representing a relationship between a state of the known electrical equipment and at least one piece of information regarding an intensity, a time of occurrence, and a phase of occurrence related to a representative value of a pulse group obtained from the known electrical equipment, and based on at least one piece of information regarding the intensity, the time of occurrence, and the phase of occurrence related to the electrical equipment to be diagnosed; The partial discharge diagnostic device according to claim 7.

9. Identifying timings of occurrence of a plurality of pulses from a signal related to partial discharge generated from the electrical equipment to be diagnosed; extracting a group of pulses generated due to treeing based on the generation timings of the plurality of pulses; A partial discharge diagnostic method comprising:

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