Partial discharge detection method and system

Abstract

The present invention discloses a partial discharge detection method and system, wherein the method comprises: detecting a power frequency sinusoidal AC signal and a partial discharge signal at a target part of a power system; the partial discharge signal is a discrete pulse signal superimposed within a power frequency period; obtaining a square wave signal containing high and low level information and the same frequency as the power frequency sinusoidal AC signal, and calculating the power frequency phase information according to the square wave signal; obtaining the position information of the power frequency phase where the partial discharge is located according to the partial discharge signal; and performing partial discharge detection and analysis according to the power frequency phase information and the position information. The present application simplifies the circuit structure of the power frequency phase information detection device, reduces the device cost, ensures the accuracy and real-time performance of phase detection, and improves the accuracy and efficiency of partial discharge detection.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a partial discharge detection method and system. Background Art

[0002] Partial discharge is one of the main causes of insulation degradation. In the power system, partial discharge detection is required for some key parts, such as transformers, GIS platforms, cables and switch cabinets. When partial discharge occurs, the charge migration directly generates high-frequency pulse current, accompanied by interference signals caused by factors such as ultrasound, electromagnetic radiation, optics or chemical reactions. By analyzing the power frequency correlation of the detection signal, that is, judging whether the detection signal is related to the power frequency signal, it is helpful to eliminate the interference signal in the partial discharge detection signal. The power frequency correlation mainly detects the power frequency phase.

[0003] At present, the detection method of power frequency phase is to collect the real-time AC signal of the target part by the current transformer, input the real-time AC signal into the conditioning circuit for processing, and then convert the conditioned real-time AC signal into a digital signal through the analog-to-digital converter. Finally, the processor calculates the digital signal to obtain the power frequency phase information of the target part. The hardware system of this power frequency phase detection method is relatively complex, and the accuracy and real-time performance of phase detection are limited by the processing power of the processor. The key data in the partial discharge detection and analysis of power frequency phase information directly affects the accuracy and reliability of the partial discharge detection system. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a partial discharge detection method and system.

[0005] The partial discharge detection method provided in the first aspect includes:

[0006] Detecting the power frequency sinusoidal AC signal and partial discharge signal at the target part of the power system; the partial discharge signal is a discrete pulse signal superimposed on the power frequency cycle;

[0007] Acquire a square wave signal containing high and low level information and having the same frequency as the industrial frequency sinusoidal AC signal, and calculate the industrial frequency phase information according to the square wave signal;

[0008] According to the partial discharge signal, obtaining position information of the power frequency phase where the partial discharge is located;

[0009] Partial discharge detection and analysis is performed based on the power frequency phase information and the position information.

[0010] The partial discharge detection system provided in the second aspect includes:

[0011] The power frequency phase detection unit detects the power frequency sinusoidal AC signal and the partial discharge signal at the target part of the power system, wherein the partial discharge signal is a discrete pulse signal superimposed on the power frequency period; obtains a square wave signal containing high and low level information and the same frequency as the power frequency sinusoidal AC signal, and calculates the power frequency phase information according to the square wave signal;

[0012] The processing unit is used to execute: obtaining the position information of the power frequency phase where the partial discharge is located according to the partial discharge signal; and performing partial discharge detection and analysis according to the power frequency phase information and the position information.

[0013] The present application first detects the industrial frequency sinusoidal AC signal and partial discharge signal of the target part of the power system. The target part is, for example, a cable. The industrial frequency sinusoidal AC signal is used for industrial frequency phase detection, and the partial discharge signal is used for subsequent partial discharge detection. The present application converts the industrial frequency sinusoidal AC signal into a square wave signal of the same frequency. The square wave signal contains high and low level information, so as to distinguish whether each signal point in the waveform is high level or low level. Generally, the high level is set to 1 and the low level is set to 0, so as to convert the sinusoidal AC analog signal into a square wave signal. The square wave signal is a digital signal and has the same frequency as the industrial frequency sinusoidal AC signal. Therefore, the square wave signal can be used to obtain the industrial frequency phase information required for partial discharge analysis, and the digital square wave signal can be detected to obtain the industrial frequency phase information. Then, according to the partial discharge signal, the position information of the industrial frequency phase where the partial discharge is located is obtained, and then combined with the industrial frequency phase information, the relevant detection and analysis process of the partial discharge can be carried out to obtain the required detection results. The present application simplifies the circuit structure of the industrial frequency phase information detection device, reduces the device cost, ensures the accuracy and real-time performance of phase detection, and improves the accuracy and efficiency of partial discharge detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be accessed in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 The structural schematic diagram of the partial discharge detection system is shown as an example;

[0016] Figure 2 The structural schematic diagram of the power frequency phase detection unit is exemplarily shown in FIG.

[0017] FIG3( a ) shows a simplified schematic diagram of a comparator;

[0018] FIG3( b ) shows a simplified schematic diagram of a non-inverting comparator;

[0019] FIG3( c ) shows a simplified schematic diagram of an inverting comparator;

[0020] Figure 4 exemplarily shows a waveform diagram of a square wave signal obtained by a non-inverting comparator;

[0021] Figure 5 exemplarily shows a waveform diagram of a square wave signal obtained by an inverse comparator;

[0022] Figure 6 Schematic diagram of PRPSA spectrum is exemplarily shown in FIG.

[0023] Figure 7 Schematic diagram of PRPD spectrum is shown as an example;

[0024] Figure 8 exemplarily shows a partial discharge distribution diagram of surface partial discharge;

[0025] Fig. 9 A schematic diagram of a first typical discharge spectrum is shown as an example;

[0026] Fig.10 A schematic diagram of a second typical discharge spectrum is shown as an example;

[0027] Fig.11 A schematic diagram of a third typical discharge spectrum is shown as an example;

[0028] Fig.12 A schematic diagram of a fourth typical discharge spectrum is shown as an example;

[0029] Fig.13 A schematic diagram of a fifth typical discharge spectrum is shown as an example;

[0030] Fig.14 A flow chart of a partial discharge detection method is shown in FIG. DETAILED DESCRIPTION

[0031] In order to make the purpose, implementation mode and advantages of the present application clearer, the exemplary implementation mode of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0032] Based on the exemplary embodiments described in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the claims attached to this application. In addition, although the disclosure in this application is introduced according to one or several exemplary examples, it should be understood that each aspect of the disclosure can also constitute a complete implementation method separately.

[0033] It should be noted that the brief description of terms in this application is only for the convenience of understanding the embodiments described below, and is not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their common and usual meanings.

[0034] In addition, the terms "include" and "have" and any variations thereof are intended to cover but not exclude inclusion, for example, a product or device comprising a list of components is not necessarily limited to those components expressly listed but may include other components not expressly listed or inherent to such products or devices.

[0035] In some embodiments, Figure 1 The structure of the partial discharge detection system is exemplarily shown, including a power frequency phase detection unit 100 , a collection unit 200 and a processing unit 300 .

[0036] In some embodiments, Figure 2 As shown, the power frequency phase detection unit 100 includes a current transformer 101, a comparator 102 and a field programmable logic gate array 103 which are connected in series in sequence.

[0037] Among them, the current transformer 101 is the initial link, connected to the target part of the power system, and is used to detect the partial discharge signal and the industrial frequency sinusoidal AC signal when partial discharge occurs at the target part. Among them, the partial discharge signal is a discrete pulse signal superimposed on the industrial frequency period, which can be used for subsequent partial discharge detection and analysis; the industrial frequency sinusoidal AC signal is used for the industrial frequency phase detection of partial discharge. When the current transformer is detected, the partial discharge signal and the industrial frequency sinusoidal AC signal will be collected at the same time. The partial discharge signal and the industrial frequency sinusoidal AC signal can be regarded as two manifestations of the same detection signal.

[0038] The current transformer 101 can convert the real-time AC high voltage collected at the target part into a low voltage, and finally output an analog signal in the form of industrial frequency sinusoidal AC. The target part can be a part of power equipment such as a transformer and a cable where partial discharge is prone to occur, which is not specifically limited in this application. The industrial frequency described in this application is generally 50Hz.

[0039] The comparator 102 is a high-gain comparator. First, the preset gain of the comparator 102 amplifies the industrial frequency sinusoidal AC signal to obtain an amplified signal. The level of the amplified signal Vi With reference level V ref After comparison, a square wave signal containing high and low level information and having the same frequency / period as the industrial frequency sinusoidal AC signal is output.

[0040] Specifically, as shown in the simplified diagram of the comparator in FIG3(a), the input end of the comparator 102 includes a positive pin (+) and a negative pin (-), the positive pin (+) input is V1, the negative pin (-) input is V2, one of the positive pin (+) and the negative pin (-) inputs the amplified signal, and the other inputs the reference level V ref After the two are compared, a square wave signal is output from the output end.

[0041] As shown in FIG. 3( b ), when the amplified signal is input from the positive pin (+) of the comparator 102, that is, V1 = V i , V2=V ref This situation belongs to the same direction comparator, that is, the signal point in the waveform of the amplified signal that is greater than the reference level is output as a high level, and the signal point in the waveform of the amplified signal that is less than the reference level is output as a low level. According to the level state of all signal points in the waveform of the amplified signal, the amplified signal can be converted into a square wave signal. The waveform of the square wave signal is as follows Figure 4 As shown in the figure, if the high level is set to 1 and the low level is set to 0, the converted square wave signal is a typical digital signal, which is convenient for subsequent FPGA calculations.

[0042] As shown in FIG. 3( c ), when the amplified signal is input from the negative pin (-) of the comparator 102 , that is, V1 = V ref , V2=V i This situation belongs to the reverse comparator, that is, the signal points in the waveform of the amplified signal that are greater than the reference level are output as low levels, and the signal points in the waveform of the amplified signal that are less than the reference level are output as high levels. According to the level states of all signal points in the waveform of the amplified signal, the amplified signal can be converted into a square wave signal, thereby obtaining the waveform of the square wave signal as shown in the figure. Figure 5 As shown, its waveform state is similar to Figure 4 Quite the contrary.

[0043] The comparator 102 may be provided with a corresponding interface to modify and adjust the preset gain and the reference level V ref The size of the reference level V ref The duty cycle of the square wave signal can be adjusted to make the output square wave signal of higher quality. The comparator 102 can be selected according to actual needs, such as selecting a zero-crossing comparator, a voltage comparator, etc., which is not specifically limited in this embodiment. The comparator 102 can synchronously complete the conversion of the analog signal to the digital signal, and the obtained square wave signal has a consistent frequency / period with the industrial frequency sinusoidal AC signal, so that the square wave signal can be used to accurately obtain the industrial frequency phase information in the partial discharge.

[0044] Field Programmable Gate Array (FPGA) 103 is a customizable circuit in a dedicated integrated circuit, and is a programmable logic array. The basic structure may include input and output units (I / O), configurable logic blocks, digital clock management modules, embedded block RAM, wiring resources, embedded dedicated hard cores, and bottom embedded functional units, etc. It has the advantages of rich wiring resources, reprogrammable, and high integration. The relevant structure, functional configuration, and working mechanism of FPGA can refer to the description of the prior art, and will not be repeated in this embodiment.

[0045] In some embodiments, the comparator 102 outputs the square wave signal to the FPGA, and the FPGA collects the waveform of the square wave signal, detects the rising edge or falling edge of the square wave, uses its own clock as the time reference point for timing, and records the time interval between two adjacent rising edges or falling edges. The time interval is the period T of the square wave signal and the industrial frequency sinusoidal AC signal. The corresponding frequency f can be obtained by taking the inverse of the period T. According to the frequency f of the square wave signal, the industrial frequency phase information corresponding to the industrial frequency sinusoidal AC signal at any time can be obtained.

[0046] For the power frequency phase detection unit 100 provided above, the current transformer is first used to detect the power frequency sinusoidal AC signal of the target part of the power system, such as the cable, etc. After the power frequency sinusoidal AC signal is amplified with high gain by a comparator, the amplified signal is compared with the preset reference level to distinguish whether each signal point in the waveform is high level or low level. Generally, the high level is set to 1 and the low level is set to 0, so as to convert the sinusoidal AC analog signal into a square wave signal. The square wave signal is a digital signal and has the same frequency as the power frequency sinusoidal AC signal. Therefore, the square wave signal can be used to obtain the power frequency phase information required for partial discharge analysis. The present application uses FPGA to detect the digital square wave signal, and the power frequency phase information can be obtained quickly and accurately. The present application simplifies the circuit structure of the power frequency phase information detection unit, reduces the cost of the detection structure, ensures the accuracy and real-time performance of the power frequency phase detection, and thus improves the accuracy and efficiency of partial discharge detection.

[0047] The acquisition unit 200 is used to acquire the partial discharge signal detected by the current transformer 101, and to acquire the power frequency phase information output by the power frequency phase detection unit 100, and to send the partial discharge signal and the power frequency phase information to the processing unit 300. It should be noted that when the acquisition unit 200 acquires the partial discharge signal, it generally also acquires the power frequency sinusoidal AC signal synchronously, but the partial discharge signal is mainly used in the partial discharge analysis and detection.

[0048] The processing unit 300 is used to execute the following program steps:

[0049] Step (A), obtaining position information of the power frequency phase where the partial discharge is located according to the partial discharge signal.

[0050] In some embodiments, a more specific implementation of step (A) is: generating a partial discharge voltage waveform from the partial discharge signal, time-synchronizing the partial discharge voltage waveform with the power frequency phase information, and obtaining position information of the power frequency phase where the partial discharge is located.

[0051] By analyzing the power frequency correlation of the detection signal of the current transformer, it is determined whether the detection signal is correlated with the power frequency signal. If it is correlated, it means that the detection signal is sent under the power frequency environment, and it is very likely to be a partial discharge signal. Of course, it is not ruled out that it may be caused by interference from the power system, such as interference from the air conditioner, meter cabinet, and secondary circuit; but if it is not correlated, the detection signal does not have power frequency correlation, and it mostly comes from interference signals such as electromagnetic radiation and ultrasound. It can be seen that analyzing the power frequency correlation is conducive to eliminating interference signals in partial discharge detection signals. The power frequency correlation is mainly to detect the power frequency phase information.

[0052] After receiving the partial discharge signal, the processing unit 300 can obtain the corresponding local voltage waveform, which is a low-voltage waveform output by the current transformer when partial discharge occurs at the target location. The low-voltage waveform carries the partial discharge signal and may also carry an interference signal. Therefore, the partial discharge voltage waveform and the power frequency phase are first synchronized in time to locate the position of the power frequency phase in the partial discharge voltage waveform, thereby obtaining the position information of the power frequency phase where the partial discharge is located.

[0053] Step (B), performing partial discharge detection and analysis based on the power frequency phase information and the position information.

[0054] In some embodiments, step (B) may specifically include the following sub-steps:

[0055] Step (B1): obtaining a pulse sequence phase distribution analysis spectrum and a partial discharge phase distribution spectrum according to the power frequency phase information and the position information.

[0056] Among them, after the position information is determined, the position of the power frequency phase in the local voltage waveform is known, that is, the signal point with power frequency correlation is determined, and the interference signals that do not have power frequency correlation are filtered out. These signal points with power frequency correlation are most likely local discharge signals, but some interference signals may still exist. Therefore, the source of the interference signal can be identified, and corresponding interference suppression measures can be taken in a targeted manner to eliminate the interference signal, thereby accurately obtaining the phase position of the local discharge, so as to more accurately obtain the pulse sequence phase distribution analysis (Phase Resolved Pulse Sequence Analysis, PRPSA) and local discharge phase distribution (Phase Resolved Partial Discharge, PRPD).

[0057] For example, the sources of interference signals include: interference from the power supply, interference from the grounding system, external interference such as other high-voltage tests or electromagnetic radiation, contact noise caused by poor contact in the test circuit or sample, etc. For interference from the power supply, a filter can be used in the power supply to suppress it; for interference from the grounding system, it can be eliminated by connecting the test circuit to an appropriate grounding point alone; for external interference, such as static electricity or magnetic induction caused by high-voltage tests, nearby switch operations, radio transmissions, etc., and electromagnetic radiation, they can all be coupled and introduced by the partial discharge test circuit, and thus mistakenly regarded as partial discharge pulses. Such signals can be suppressed by shielding; for noise interference, it can be eliminated by denoising. The source of the interference signal and its suppression method are not limited to those described in this embodiment.

[0058] Then, based on the power frequency phase information and position information, the PRPSA spectrum and PRPD spectrum are drawn by superimposing the local discharge information of multiple power frequency cycles. PRPSA and PRPD are two mode recognitions of local discharge.

[0059] Among them, PRPSA displays each partial discharge pulse with a phase mark in chronological order, and the chronological order is generally processed according to the cycle number. This mode is the most basic partial discharge mode and contains all the information of partial discharge detection. The PRPSA mode can generally be recorded as q s (t s ,u(t s )), that is, according to the output of partial discharge detection, the power frequency phase t of each partial discharge is counted s and its corresponding amplitude information u(t s ), Figure 6 An example of a PRPSA profile is shown.

[0060] PRPD is also called mode, which requires the construction of the power frequency phase where partial discharge occurs The relationship between the discharge amplitude q and the number of discharges n. Among them, the widely used three-dimensional map is Mode, coming soon and q are divided into several small intervals, in the plane Several grids are formed on the surface, and the number of discharges in each grid is counted to obtain Graph of statistical patterns. Compared with the PRPSA model, the PRPD model loses information about the time dimension. Figure 7 An example of a PRPD spectrum is shown. The relevant contents of the PRPSA mode and the PRPD mode, as well as the drawing methods of the PRPSA spectrum and the PRPD spectrum can refer to the prior art, and will not be described in detail in this embodiment.

[0061] Step (B2), obtaining a local discharge distribution map according to the pulse sequence phase distribution analysis map and the local discharge phase distribution map, and determining the type and hazard level of the local discharge through the local discharge distribution map.

[0062] If there are gaps, bubbles, impurities, trauma, etc. inside the insulation of high-voltage electrical equipment, or defects on the insulation surface, local discharge will occur when the electric field strength reaches a certain value. The heat and active gases generated by this local discharge will corrode the local insulation, causing the gradual aging of the insulation medium performance. Due to the cumulative effect, it may even lead to insulation breakdown and flashover. Through the partial discharge test of electrical equipment, the type and characteristics of partial discharge can be analyzed and distinguished, the discharge intensity can be tested, and the hazard level of partial discharge can be evaluated. Partial discharge may occur in the cavities of solid insulation, in the bubbles of liquid insulation, between insulation layers with different dielectric properties, or at the edges and corners of metal surfaces. Therefore, the types of partial discharge can be summarized into three categories, namely, internal partial discharge of insulating materials, surface partial discharge, and corona discharge.

[0063] Internal partial discharge: If the insulating material contains air gaps, impurities, oil gaps, etc., discharge may occur inside the medium or between the medium and the electrode. The discharge characteristics are related to the medium properties and the shape, size and position of the inclusions.

[0064] Surface partial discharge: If there is a field strength component parallel to the dielectric surface in the electric field, when the field strength component reaches the breakdown field strength, surface discharge may occur. This may occur at the bushing flange, the cable terminal, or at the surface of the conductor and the dielectric bend. In some cases, the waveform of surface partial discharge is related to the electrode shape. For example, when the electrode is asymmetric, the partial discharge amplitude of the positive and negative half cycles is not equal. Figure 8As shown, when the electrode generating surface partial discharge is at a high potential, the discharge pulses appearing in the negative half cycle are larger and sparser, while the discharge pulses appearing in the positive half cycle are denser but smaller in amplitude.

[0065] Corona discharge: Corona discharge often occurs in areas with high electric field strength in non-uniform electric fields, such as around high-voltage wires, near the tip of a charged body, etc. In places where the radius of curvature of the conductor shell is small, especially at the tip, the charge density is very large. In areas close to the surface of the charged body, the electric field is proportional to the charge density, so the field strength is very strong at the tip of the conductor. Therefore, when the conductor potential around the air increases, corona discharge may occur at these tips.

[0066] According to the characteristics and information carried in the PRPSA spectrum and the PRPD spectrum, the corresponding partial discharge distribution map is generated, that is, the actual partial discharge waveform spectrum output by the entire partial discharge detection system. For example, Figure 8 In the example, the partial discharge distribution diagram is approximately elliptical as a whole. There are discharge pulses distributed in the elliptical area, and the distribution position, density, pulse amplitude and other information of the discharge pulses can be obtained, which is convenient for analyzing the distribution characteristics and pulse intensity of the discharge pulses and evaluating the hazard level of partial discharge.

[0067] In some embodiments, a partial discharge spectrum database can be set up, in which all typical partial discharge waveform spectra (i.e., the typical discharge spectrum described in the present application) can be recorded, and the partial discharge types corresponding to these typical discharge spectra can be marked. By matching the partial discharge distribution map output by the partial discharge detection system with the typical discharge spectrum in the database, for example, by using the spectrum similarity association matching method, the target typical discharge spectrum with the highest similarity to the partial discharge distribution map output by the system can be screened out from the database, so that according to the correspondence between the typical discharge spectrum and the partial discharge type in the database, the partial discharge type corresponding to the target typical discharge spectrum can be queried, and the most likely partial discharge type can be located. Among them, the typical discharge spectrum can be obtained according to conventional partial discharge tests or by collecting waveform spectra under known partial discharge types.

[0068] Fig. 9 The typical discharge spectrum shown in the figure belongs to the capacitive discharge waveform, which can occur in bubbles of oil-paper insulation or solid insulation, in oil-immersed capacitors, or in paper-wrapped insulation and plastic-filled insulation. The pulse amplitude and number of pulses of the discharge increase with the increase of voltage.

[0069] Fig.10 It is a typical discharge spectrum of local discharge inside the interlayer dielectric, which may occur in the discharge of insulating cardboard and creeping discharge of tree branches.

[0070] Fig.11This is a typical discharge pattern between the metal and dielectric surfaces. It may be caused by an air gap between the metal and the dielectric, or uneven surface conductivity.

[0071] Fig.12 It is a typical discharge spectrum of metal electrode surface discharge. This type of local discharge may occur when there is discharge between the exposed metal surface and the medium, when there are bubbles between the metal and the medium, or when the bubbles in the medium may contain impurities such as metal or carbon.

[0072] Fig.13 It is a typical discharge spectrum of corona discharge, including three states (a), (b) and (c) from top to bottom. Corona discharge generally occurs at the metal tip or the edge electric field concentration area. The corona discharge starts only within half a cycle of the test voltage and is symmetrically distributed on both sides of the voltage peak, as shown in Figure (a). As the voltage increases, the number of pulses (width) increases symmetrically, as shown in Figure (b). If the discharge tip electrode is at a high potential, the corona discharge pulse appears in the negative half cycle of the test voltage; if the discharge tip electrode is at a low potential, the corona discharge pulse appears in the positive half cycle. For a certain electrode, the corona initially appears in one half cycle, but when the voltage rises much higher than the starting voltage, local discharge with a larger amplitude and a smaller number of pulses will also appear in the other half cycle, as shown in Figure (c). This application only illustrates five typical discharge spectra. In practical applications, typical discharge spectra are not limited to those shown in this embodiment, and they will not be described one by one in the specification of this application.

[0073] In some embodiments, for various typical discharge spectra in the partial discharge spectrum database, each typical discharge spectrum can also include refined spectra of different danger levels / grades. For example, the database stores typical discharge spectra in the form of a table, and typical discharge spectra of different partial discharge types are stored in different rows. The same row can include multiple columns, and different columns in the same row represent refined spectra of different danger levels / grades under a partial discharge type. Obtain the refined spectra of different danger levels included in the partial discharge type queried in the aforementioned embodiment, and analyze and compare them with the partial discharge distribution map to obtain the danger level corresponding to the partial discharge distribution map. The storage method of the database in this embodiment can determine the partial discharge type and the danger level / grade corresponding to the partial discharge type. The danger level / grade can be set according to the actual application.

[0074] In the above embodiment, through the partial discharge map database, the type and hazard level of partial discharge can be automatically matched according to the partial discharge distribution map output by the system, and the automatic generation and output of the partial discharge waveform map, as well as the automatic analysis of the map and the report of the analysis results are completed, which can improve the efficiency of partial discharge testing and detection. In other embodiments, the analysis of the type and hazard level of partial discharge is not limited to the solution provided in this application. For example, after the system outputs and displays the layout discharge distribution map, the operator can view the waveform map and determine the type of partial discharge and evaluate the hazard level based on empirical knowledge.

[0075] like Fig.14 As shown, a partial discharge detection method is also provided, comprising:

[0076] Step S10, detecting a power frequency sinusoidal AC signal and a partial discharge signal at a target location of the power system; the partial discharge signal is a discrete pulse signal superimposed on a power frequency cycle;

[0077] Step S20, obtaining a square wave signal including high and low level information and having the same frequency as the industrial frequency sinusoidal AC signal, and calculating the industrial frequency phase information according to the square wave signal;

[0078] Step S30, obtaining position information of the power frequency phase where the partial discharge is located according to the partial discharge signal;

[0079] Step S40: performing partial discharge detection and analysis according to the power frequency phase information and the position information.

[0080] In some embodiments, the square wave signal is obtained according to the following steps:

[0081] Amplifying the industrial frequency sinusoidal AC signal according to a preset gain using a comparator to obtain an amplified signal;

[0082] The level of the amplified signal is compared with a reference level, and the square wave signal is output.

[0083] In some embodiments, the method further comprises:

[0084] When the amplified signal is input from the positive pin of the comparator, if the level of the signal point in the waveform of the amplified signal is greater than the reference level, the signal point is output as a high level; if the level of the signal point in the waveform of the amplified signal is less than the reference level, the signal point is output as a low level; or, when the amplified signal is input from the negative pin of the comparator, if the level of the signal point in the waveform of the amplified signal is greater than the reference level, the signal point is output as a low level; if the level of the signal point in the waveform of the amplified signal is less than the reference level, the signal point is output as a high level;

[0085] The amplified signal is converted into the square wave signal according to the level states of all signal points in the waveform of the amplified signal.

[0086] In some embodiments, calculating the power frequency phase information includes:

[0087] The waveform of the square wave signal is collected by using a field programmable logic gate array, and the interval time between two adjacent rising edges or falling edges is recorded with the clock as the time reference point to obtain the frequency of the square wave signal;

[0088] According to the frequency of the square wave signal, the power frequency phase information corresponding to the partial discharge signal at any time is obtained.

[0089] In some embodiments, performing partial discharge detection analysis includes:

[0090] According to the power frequency phase information and the position information, a pulse sequence phase distribution analysis spectrum and a partial discharge phase distribution spectrum are obtained;

[0091] A partial discharge distribution map is obtained according to the pulse sequence phase distribution analysis map and the partial discharge phase distribution map, and the type and hazard level of the partial discharge are determined through the partial discharge distribution map.

[0092] In some embodiments, obtaining the position information of the power frequency phase where the partial discharge is located includes:

[0093] A partial discharge voltage waveform is generated from the partial discharge signal, and the partial discharge voltage waveform is time-synchronized with the power frequency phase information to obtain position information of the power frequency phase where the partial discharge is located.

[0094] In some embodiments, the type of partial discharge is determined as follows:

[0095] Screening out a target typical discharge spectrum with the highest similarity to the local discharge distribution map from a local discharge spectrum database; wherein the local discharge spectrum database records typical discharge spectra and their corresponding local discharge types;

[0096] The local discharge type corresponding to the target typical discharge spectrum is queried.

[0097] In some embodiments, each row in the partial discharge spectrum database stores a typical discharge spectrum corresponding to a partial discharge type, and the typical discharge spectrum includes refined spectra corresponding to different hazard levels in the same row but different columns. The hazard level of the partial discharge is determined according to the following steps:

[0098] Obtaining a detailed map of different hazard levels included in the queried partial discharge type;

[0099] The local discharge distribution map is analyzed and compared with the refined maps of different hazard levels to obtain the hazard level corresponding to the local discharge distribution map.

[0100] For the partial discharge detection method described in this embodiment, the execution subject of each step and the specific description and development of each step can correspond to the description of the system embodiment, and this embodiment will not be repeated here.

[0101] Those skilled in the art can clearly understand that the technology in the embodiments of the present invention can be implemented by means of software plus a necessary general hardware platform. In a specific implementation, the present invention also provides a computer storage medium, wherein the computer storage medium can store a program, and when the computer storage medium is located in a partial discharge detection system, the program can include the program steps involved in the partial discharge detection method when executed. The computer storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0102] In this specification, the same or similar parts between the system embodiments and the method embodiments may be referenced to each other, and the related contents will not be repeated here.

[0103] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The description and examples are to be considered merely as exemplary and do not constitute limitations on the scope of protection of the present invention. The true scope and spirit of the present invention are indicated by the appended claims.

Claims

1. A partial discharge detection system, characterized in that: include: Power frequency phase detection unit and processing unit; The power frequency phase detection unit includes: a current transformer, a comparator, and a field programmable logic gate array; wherein the current transformer is connected to a target part of the power system, the comparator is connected to the current transformer, and the field programmable logic gate array is connected to the comparator; The current transformer in the power frequency phase detection unit is used to: detect the power frequency sinusoidal AC signal and partial discharge signal at the target part of the power system, the partial discharge signal is a discrete pulse signal superimposed on the power frequency cycle, and convert the real-time AC high voltage collected at the target part into a low voltage to output an analog signal in the form of power frequency sinusoidal AC; The comparator and the field programmable logic gate array in the power frequency phase detection unit are used to: obtain a square wave signal containing high and low level information and the same frequency as the power frequency sinusoidal AC signal, so as to convert the analog signal into a digital signal, and calculate the power frequency phase information according to the square wave signal; The processing unit is used to execute: obtaining the position information of the power frequency phase where the partial discharge is located according to the partial discharge signal; wherein the obtaining the position information of the power frequency phase where the partial discharge is located comprises: generating a partial discharge voltage waveform from the partial discharge signal, performing time synchronization on the partial discharge voltage waveform and the power frequency phase information, locating the position of the power frequency phase where the partial discharge is located in the partial discharge voltage waveform, and obtaining the position information of the power frequency phase where the partial discharge is located; and performing partial discharge detection and analysis according to the power frequency phase information and the position information.

2. The system according to claim 1, characterized in that Also includes acquisition unit: The acquisition unit is used to acquire the partial discharge signal detected by the current transformer, and to acquire the power frequency phase information output by the power frequency phase detection unit, and to send the partial discharge signal and the power frequency phase information to the processing unit.

3. The system according to claim 1, characterized in that The comparator adopts a high-gain comparator, and the comparator obtains the square wave signal according to the following steps: Amplifying the industrial frequency sinusoidal AC signal according to a preset gain to obtain an amplified signal; Comparing the level of the amplified signal with a reference level, and outputting the square wave signal; The preset gain and the reference level are modified and adjusted by using the corresponding interface of the comparator, so as to adjust the duty cycle of the square wave signal by modifying the reference level, so as to improve the quality of the output square wave signal.

4. The system according to claim 3, characterized in that The input end of the comparator includes a positive pin and a negative pin. When the amplified signal is input from the positive pin of the comparator, if the level of the signal point in the waveform of the amplified signal is greater than the reference level, the signal point output is a high level; If the level of the signal point in the waveform of the amplified signal is less than the reference level, the signal point is output as a low level; Alternatively, when the amplified signal is input from the negative pin of the comparator, if the level of the signal point in the waveform of the amplified signal is greater than the reference level, the signal point is output as a low level; If the level of the signal point in the waveform of the amplified signal is less than the reference level, the signal point is output as a high level; The amplified signal is converted into the square wave signal according to the level states of all signal points in the waveform of the amplified signal.

5. The system according to claim 1, characterized in that The calculating of the power frequency phase information comprises: The waveform of the square wave signal is collected by using a field programmable logic gate array, and the interval time between two adjacent rising edges or falling edges is recorded with the clock as the time reference point to obtain the frequency of the square wave signal; According to the frequency of the square wave signal, the power frequency phase information corresponding to the partial discharge signal at any time is obtained.

6. The system according to claim 1, characterized in that The partial discharge detection and analysis comprises: According to the power frequency phase information and the position information, a pulse sequence phase distribution analysis spectrum and a partial discharge phase distribution spectrum are obtained; A partial discharge distribution map is obtained according to the pulse sequence phase distribution analysis map and the partial discharge phase distribution map, and the type and hazard level of the partial discharge are determined through the partial discharge distribution map.

7. The system according to claim 6, characterized in that To determine the type of partial discharge, proceed as follows: Screening out a target typical discharge spectrum with the highest similarity to the local discharge distribution map from a local discharge spectrum database; wherein the local discharge spectrum database records typical discharge spectra and their corresponding local discharge types; The local discharge type corresponding to the target typical discharge spectrum is queried.

8. The system according to claim 7, characterized in that Each row in the partial discharge spectrum database stores a typical discharge spectrum corresponding to a partial discharge type, and the typical discharge spectrum includes refined spectra corresponding to different hazard levels in the same row but different columns. The hazard level of partial discharge is determined according to the following steps: Obtaining a detailed map of different hazard levels included in the queried partial discharge type; The local discharge distribution map is analyzed and compared with the refined maps of different hazard levels to obtain the hazard level corresponding to the local discharge distribution map.

9. The system according to claim 6, characterized in that The system is used to identify the source of the interference signal and take corresponding interference suppression measures to eliminate the interference signal; wherein, For interference from the power supply, the system is used to suppress it by using a filter in the power supply; For interference from the grounding system, the system is used to eliminate it by connecting the test circuit separately to a suitable grounding point; The system is used to suppress external interference by shielding, and the external interference includes high voltage test, nearby switch operation, static electricity or magnetic induction caused by radio transmission, and electromagnetic radiation; For noise-type interference, the system is used to eliminate it by denoising.

10. A partial discharge detection method, characterized in that: The partial discharge detection system as claimed in claim 1 comprises: Detect the power frequency sinusoidal AC signal and partial discharge signal at the target part of the power system; the partial discharge signal is a discrete pulse signal superimposed on the power frequency cycle, and the real-time AC high voltage collected at the target part is converted into a low voltage to output an analog signal in the form of power frequency sinusoidal AC; Acquire a square wave signal containing high and low level information and having the same frequency as the power frequency sinusoidal AC signal to convert the analog signal into a digital signal, and calculate the power frequency phase information according to the square wave signal; According to the partial discharge signal, position information of the power frequency phase where the partial discharge is located is obtained, wherein obtaining the position information of the power frequency phase where the partial discharge is located includes: Generate a partial discharge voltage waveform from the partial discharge signal, synchronize the partial discharge voltage waveform with the power frequency phase information, locate the position of the power frequency phase where the partial discharge is located in the partial discharge voltage waveform, and obtain the position information of the power frequency phase where the partial discharge is located; Partial discharge detection and analysis is performed based on the power frequency phase information and the position information.

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