Partial discharge detection system and method of cable

Abstract

The invention discloses a cable partial discharge detection method and system, and the method comprises the steps: installing sampling sensor groups on a detected cable at a preset interval, and each group at least comprises a current sensor and an ultrasonic sensor; synchronously sampling and preprocessing the high-frequency current signal and the ultrasonic signal; extracting current waveform characteristics and a first time stamp of arrival of the first pulse, and extracting sound wave pulses in the ultrasonic signals and a second time stamp of arrival of the sound wave pulses; and calculating a time difference, if the time difference is smaller than a preset threshold value and the waveform amplitude similarity is within a preset range, determining that no failure partial discharge exists, otherwise, positioning a failure position. According to the method, the acoustoelectric signals are acquired cooperatively through multiple sensors, interference is eliminated in combination with time difference and waveform similarity criteria, the detection reliability and the positioning precision are effectively improved, and the method is suitable for cable insulation state monitoring and fault early warning.

Description

Technical Field

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

[0002] Cables are critical infrastructure for power transmission. Aging or defects in their insulation systems can lead to partial discharge (PD). PD not only accelerates insulation degradation and causes cable breakdown, but can also cause large-scale power outages, severely impacting the safety and reliability of power systems. Therefore, accurate detection and location of PD in cables is a core technical requirement for preventing cable failures and enabling condition-based maintenance.

[0003] Existing techniques analyze the high-frequency current signals generated by partial discharge in cables. However, these signals are susceptible to external electromagnetic interference and difficult to distinguish between internal discharge and external interference. Positioning accuracy relies on the signal propagation model, resulting in significant errors in complex cable layouts. Alternatively, positioning can be performed using acoustic signals generated by partial discharge. However, acoustic waves significantly attenuate in the cable dielectric, leading to a significant decrease in detection sensitivity with increasing distance. Furthermore, these signals cannot directly reflect the electrical characteristics of the discharge and are susceptible to interference from ambient vibration and noise.

[0004] Time-difference positioning methods based on a single signal (such as current or sound waves) fail to account for signal attenuation and environmental factors. Over long cable runs or in scenarios with uneven material quality, positioning errors can reach several meters or even higher. This lack of comprehensive compensation for factors like cable material degradation, temperature, and humidity fluctuations leads to significant deviations between the attenuation model and actual transmission characteristics, making it impossible to accurately identify the correlation between discharge locations and insulation defects. Summary of the Invention

[0005] In view of the above problems, the present invention provides a partial discharge detection system and method for cables.

[0006] The purpose of the present invention is achieved by adopting the following technical solutions: In a first aspect, a method for detecting partial discharge of a cable is provided, comprising the following steps: S1. Install sampling sensor groups at preset intervals on the cable to be tested, each sampling sensor group including at least one current sensor and one ultrasonic sensor; S2. For each sampling sensor group, synchronously sample the high-frequency current signal and the ultrasonic signal, and perform preprocessing on the high-frequency current signal and the ultrasonic signal; S3, extracting current waveform features from the high-frequency current signal, recording a first timestamp of the first pulse arrival, extracting an acoustic pulse corresponding to a partial discharge from the ultrasonic signal, and recording a second timestamp of the acoustic pulse arrival; S4, calculating the signal reception time difference based on the first timestamp and the second timestamp; If the signal reception time difference is less than a preset time threshold and the waveform amplitude similarity of the two is within a preset range, it is determined that there is no failure partial discharge; Otherwise, proceed to the next step; S5. Locate the failed partial discharge position to obtain the failed position.

[0007] As a preferred embodiment, the step S5 specifically includes the following steps: When a discharge event occurs, Calculating a pulse energy ratio of current pulses detected by two adjacent sampling sensor groups for the same discharge event, and converting the energy ratio into a first decibel attenuation; Calculating the second decibel attenuation of the acoustic pulse detected by two adjacent sampling sensor groups for the same discharge event; Calculating an acoustic-electrical comprehensive attenuation curve obtained by a proportional relationship between a first decibel attenuation and a second decibel attenuation of two adjacent sampling sensor groups; Obtaining the theoretical signal strength when the current pulse reaches each sampling sensor group in the lossless cable, calculating the average rate of change of the signal strength attenuating with the transmission distance and establishing an attenuation model; Based on the pulse energy data sets detected by all sensor groups, the spatial variation gradient of the energy distribution curve is calculated, and the point where the energy gradient reaches the maximum value is determined as the failure position.

[0008] As a preferred method, the spatial variation gradient of the energy distribution curve is calculated from the pulse energy data set detected by all sensor groups, and the point where the energy gradient reaches the maximum value is determined as the failure position, which specifically includes the following steps: Comparing the difference between the acoustic-electrical comprehensive attenuation curve and the attenuation model, wherein the attenuation model includes multiple sets of attenuation benchmark data of the lossless cable at different temperatures and humidities; When the slope of the acoustic-electrical integrated attenuation curve deviates from the preset ratio of the attenuation benchmark data of the current temperature and humidity, or the slope has a preset mutation point, it is determined that there is a failure caused by material degradation; Calculate the abnormal attenuation distance from the mutation point or slope offset position to the nearest sampling sensor group according to the acoustic absorption coefficient of the cable material; Establish the acoustic and electrical joint attenuation equation: ΔA=k1⋅α⋅d+k2⋅δ(f)⋅Δf Where ΔA is the measured attenuation, α is the acoustic absorption coefficient, d is the transmission distance, k1 and k2 are material calibration coefficients, δ(f) is the linear relationship between the skin effect depth δ of the electrical signal and the frequency, and Δf is the pulse frequency offset; Solve the least squares solution of the equation along the cable axis and take the attenuation mutation point as the candidate failure location point As a preferred embodiment, the process of establishing the acoustic-electrical integrated attenuation curve specifically includes the following steps: For each pair of adjacent sampling sensor groups, extract the peak voltage value of the pulse signal detected by the current sensor of the group and convert it into a standard decibel value as a first basic attenuation index; Extract the sound wave pulse pressure values detected by the ultrasonic sensors in the same group and convert them into standard decibel values as the second basic attenuation index. Calculate the decibel attenuation change of the current group relative to the upstream adjacent group to generate an attenuation data sequence distributed along the cable axis. At the same axial position point, the proportional relationship between the first basic attenuation index and the second basic attenuation index is defined as the acoustic-electric attenuation factor. The acoustic-electric attenuation factors connecting all sampling points are fitted using the cubic spline interpolation algorithm to form a continuous and conductive acoustic-electric comprehensive attenuation curve.

[0009] As a preferred embodiment, the process of establishing the acoustic-electrical integrated attenuation curve further includes the following steps: During the period when no discharge occurs in the cable, the background electrical noise intensity of the current sensor channel is measured and converted into a standard decibel measurement value. The ambient vibration noise intensity of the ultrasonic sensor channel is also measured and converted into a standard decibel measurement value. Calculate the ratio of the two background noise decibel values as the acoustic and electrical attenuation benchmark coefficient under background conditions; When the deviation between the acoustic and electrical attenuation coefficient of the measured discharge event and the background reference coefficient exceeds a specific ratio, it is adopted as a valid data point. All data points that do not meet this condition are deleted, and the curve is reconstructed using the interpolation calculation results of adjacent valid data points.

[0010] As a preferred method, for the candidate failure location, the phase-resolved spectrum of the partial discharge pulse at the abnormal point is measured; When the graph presents a floating potential discharge feature and the repetition rate is higher than a preset value, the failure position candidate point is confirmed to be a failure position.

[0011] In a second aspect, a partial discharge detection system for a cable is provided, comprising: a sensor array distributed at equal intervals along the cable, comprising a plurality of sampling sensor groups; a data receiving module configured to receive high-frequency current signals and ultrasonic signals from the sampling sensor group; The data processing module is configured to receive the data from the data receiving module and perform pre-processing to determine the failure location.

[0012] The beneficial effects of the present invention are: The present invention establishes a complementary mechanism for the attenuation of acoustic and electric dual-mode signals to synchronously offset signal propagation distortion; constructs a dynamic reference coefficient based on the proportional relationship between the background electric noise intensity and the ambient vibration noise intensity, and uses the strong correlation of noise in the dual channels to remove interference signals; captures the correlation characteristics of insulation degradation through the acoustic and electric attenuation factor and combines the anisotropic calibration of sound waves in cable insulation materials to eliminate the wavefront distortion caused by inhomogeneous media, thereby solving propagation distortion, interference aliasing and degradation identification from the principle level, and realizing the precise positioning and early warning of cable local discharge sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative effort.

[0014] Figure 1 It is a structural block diagram of a system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] In a first aspect of an embodiment of the present disclosure, a method for detecting partial discharge of a cable is provided, comprising the following steps: S1. Install sampling sensor groups at preset intervals on the cable to be tested, each sampling sensor group including at least one current sensor and one ultrasonic sensor; S2. For each sampling sensor group, synchronously sample the high-frequency current signal and the ultrasonic signal, and perform preprocessing on the high-frequency current signal and the ultrasonic signal; S3, extracting current waveform features from the high-frequency current signal, recording a first timestamp of the first pulse arrival, extracting an acoustic pulse corresponding to a partial discharge from the ultrasonic signal, and recording a second timestamp of the acoustic pulse arrival; S4, calculating the signal reception time difference based on the first timestamp and the second timestamp; If the signal reception time difference is less than a preset time threshold and the waveform amplitude similarity of the two is within a preset range, it is determined that there is no failure partial discharge; Otherwise, proceed to the next step; S5. Locate the failed partial discharge position to obtain the failed position.

[0017] As a preferred embodiment, the step S5 specifically includes the following steps: When a discharge event occurs, Calculating a pulse energy ratio of current pulses detected by two adjacent sampling sensor groups for the same discharge event, and converting the energy ratio into a first decibel attenuation; Calculating the second decibel attenuation of the acoustic wave pulse detected by two adjacent sampling sensor groups for the same discharge event; Calculating an acoustic-electrical comprehensive attenuation curve obtained by a proportional relationship between a first decibel attenuation and a second decibel attenuation of two adjacent sampling sensor groups; Obtaining the theoretical signal strength when the current pulse reaches each sampling sensor group in the lossless cable, calculating the average rate of change of the signal strength attenuating with the transmission distance and establishing an attenuation model; Based on the pulse energy data sets detected by all sensor groups, the spatial variation gradient of the energy distribution curve is calculated, and the point where the energy gradient reaches the maximum value is determined as the failure position.

[0018] As a preferred method, the spatial variation gradient of the energy distribution curve is calculated from the pulse energy data set detected by all sensor groups, and the point where the energy gradient reaches the maximum value is determined as the failure position, which specifically includes the following steps: Comparing the difference between the acoustic-electrical comprehensive attenuation curve and the attenuation model, wherein the attenuation model includes multiple sets of attenuation benchmark data of the lossless cable at different temperatures and humidities; When the slope of the acoustic-electrical integrated attenuation curve deviates from the preset ratio of the attenuation benchmark data of the current temperature and humidity, or the slope has a preset mutation point, it is determined that there is a failure caused by material degradation; Calculate the abnormal attenuation distance from the mutation point or slope offset position to the nearest sampling sensor group according to the acoustic absorption coefficient of the cable material; Establish the acoustic and electrical joint attenuation equation: ΔA=k1⋅α⋅d+k2⋅δ(f)⋅Δf Where ΔA is the measured attenuation, α is the acoustic absorption coefficient, d is the transmission distance, k1 and k2 are material calibration coefficients, δ(f) is the linear relationship between the skin effect depth δ of the electrical signal and the frequency, and Δf is the pulse frequency offset; Solve the least squares solution of the equation along the cable axis and take the attenuation mutation point as the candidate failure location point As a preferred embodiment, the process of establishing the acoustic-electrical integrated attenuation curve specifically includes the following steps: For each pair of adjacent sampling sensor groups, extract the peak voltage value of the pulse signal detected by the current sensor of the group and convert it into a standard decibel value as a first basic attenuation index; Extract the sound wave pulse pressure values detected by the ultrasonic sensors in the same group and convert them into standard decibel values as the second basic attenuation index. Calculate the decibel attenuation change of the current group relative to the upstream adjacent group to generate an attenuation data sequence distributed along the cable axis. At the same axial position point, the proportional relationship between the first basic attenuation index and the second basic attenuation index is defined as the acoustic-electric attenuation factor. The acoustic-electric attenuation factors connecting all sampling points are fitted using the cubic spline interpolation algorithm to form a continuous and conductive acoustic-electric comprehensive attenuation curve.

[0019] As a preferred embodiment, the process of establishing the acoustic-electrical integrated attenuation curve further includes the following steps: During the period when no discharge occurs in the cable, the background electrical noise intensity of the current sensor channel is measured and converted into a standard decibel measurement value. The ambient vibration noise intensity of the ultrasonic sensor channel is also measured and converted into a standard decibel measurement value. Calculate the ratio of the two background noise decibel values as the acoustic and electrical attenuation benchmark coefficient under background conditions; When the deviation between the acoustic and electrical attenuation coefficient of the measured discharge event and the background reference coefficient exceeds a specific ratio, it is adopted as a valid data point. All data points that do not meet this condition are deleted, and the curve is reconstructed using the interpolation calculation results of adjacent valid data points.

[0020] As a preferred method, for the candidate failure location, the phase-resolved spectrum of the partial discharge pulse at the abnormal point is measured; When the graph presents a floating potential discharge feature and the repetition rate is higher than a preset value, the failure position candidate point is confirmed to be a failure position.

[0021] In a second aspect, a partial discharge detection system for a cable is provided, such as Figure 1 Shown, including: a sensor array distributed at equal intervals along the cable, comprising a plurality of sampling sensor groups; a data receiving module configured to receive high-frequency current signals and ultrasonic signals from the sampling sensor group; The data processing module is configured to receive the data from the data receiving module and perform pre-processing to determine the failure location.

[0022] The disclosed embodiments establish a complementary mechanism for attenuation of acoustic and electrical dual-mode signals to simultaneously offset signal propagation distortion; construct a dynamic reference coefficient based on the proportional relationship between the background electrical noise intensity and the ambient vibration noise intensity, and use the strong correlation of noise in the dual channels to remove interference signals; capture the correlation characteristics of insulation degradation through the acoustic and electrical attenuation factor and combine it with the anisotropic calibration of sound waves in cable insulation materials to eliminate wavefront distortion caused by inhomogeneous media, thereby solving propagation distortion, interference aliasing and degradation identification at the principle level, and realizing accurate positioning and early warning of cable partial discharge sources.

[0023] The above description and the accompanying drawings sufficiently illustrate the embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural, logical, electrical, process and other changes. The embodiments represent only possible variations. Unless expressly required, individual components and functions are optional, and the order of operations may vary. Portions and features of some embodiments may be included in or replace portions and features of other embodiments. Moreover, the terms used in this application are only used to describe the embodiments and are not used to limit the claims. As used in the description of the embodiments and claims, the singular forms "a", "an" and "the" are intended to also include the plural forms unless the context clearly indicates otherwise. Similarly, the term "and / or" as used in this application means any and all possible combinations of one or more of the associated listings. In addition, when used in this application, the term "comprise" and its variations "comprises" and / or comprising refer to the presence of stated features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or groups thereof. In the absence of further restrictions, an element defined by the sentence "comprising a..." does not exclude the presence of other identical elements in the process, method or device that includes the element. In this article, each embodiment may focus on the differences from other embodiments, and the same and similar parts between the various embodiments can be referenced to each other. For the methods, products, etc. disclosed in the embodiments, if they correspond to the method part disclosed in the embodiments, then the relevant parts can be referred to the description of the method part.

[0024] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these effects are performed in hardware or software may depend on the specific application and design constraints of the technical solution. The technicians may use different methods for each specific application to implement the described effects, but such implementations should not be considered to exceed the scope of the embodiments of the present disclosure. The technicians will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0025] The flowcharts and block diagrams in the accompanying drawings show the possible architectures, functions and operations of the devices, methods and computer program products according to the embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, program segment or part of the code, and the module, program segment or part of the code contains one or more executable instructions for implementing the specified logical functions. In some alternative implementations, the functions marked in the boxes can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed in parallel, or they can sometimes be executed in the opposite order, which can depend on the functions involved. In the descriptions corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in an order different from that disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps can actually be executed in parallel, or they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by dedicated hardware-based devices that perform the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

Claims

1. A method for detecting partial discharge of a cable, characterized in that: The steps include: S1. Install sampling sensor groups at preset intervals on the cable to be tested, each sampling sensor group including at least one current sensor and one ultrasonic sensor; S2. For each sampling sensor group, synchronously sample the high-frequency current signal and the ultrasonic signal, and perform preprocessing on the high-frequency current signal and the ultrasonic signal; S3, extracting current waveform features from the high-frequency current signal, recording a first timestamp of the first pulse arrival, extracting an acoustic pulse corresponding to a partial discharge from the ultrasonic signal, and recording a second timestamp of the acoustic pulse arrival; S4, calculating the signal reception time difference based on the first timestamp and the second timestamp; If the signal reception time difference is less than a preset time threshold and the waveform amplitude similarity of the two is within a preset range, it is determined that there is no failure partial discharge; Otherwise, proceed to the next step; S5. Locate the failed partial discharge position to obtain the failed position.

2. The cable partial discharge detection method according to claim 1, characterized in that: The S5 specifically includes the following steps: When a discharge event occurs, Calculating a pulse energy ratio of current pulses detected by two adjacent sampling sensor groups for the same discharge event, and converting the energy ratio into a first decibel attenuation; Calculating the second decibel attenuation of the acoustic wave pulse detected by two adjacent sampling sensor groups for the same discharge event; Calculating an acoustic-electrical comprehensive attenuation curve obtained by a proportional relationship between a first decibel attenuation and a second decibel attenuation of two adjacent sampling sensor groups; Obtaining the theoretical signal strength when the current pulse reaches each sampling sensor group in the lossless cable, calculating the average rate of change of the signal strength attenuating with the transmission distance and establishing an attenuation model; Based on the pulse energy data sets detected by all sensor groups, the spatial variation gradient of the energy distribution curve is calculated, and the point where the energy gradient reaches the maximum value is determined as the failure position.

3. The cable partial discharge detection method according to claim 2, characterized in that: Based on the pulse energy data sets detected by all sensor groups, the spatial variation gradient of the energy distribution curve is calculated, and the point where the energy gradient reaches the maximum value is determined as the failure location. The specific steps include the following: Comparing the difference between the acoustic-electrical comprehensive attenuation curve and the attenuation model, wherein the attenuation model includes multiple sets of attenuation benchmark data of the lossless cable at different temperatures and humidities; When the slope of the acoustic-electrical comprehensive attenuation curve deviates from the preset ratio of the attenuation benchmark data of the current temperature and humidity, or the slope has a preset mutation point, it is determined that there is failure caused by material degradation; Calculate the abnormal attenuation distance from the mutation point or slope offset position to the nearest sampling sensor group according to the acoustic absorption coefficient of the cable material; Establish the acoustic and electrical joint attenuation equation: ΔA=k1⋅α⋅d+k2⋅δ(f)⋅Δf Where ΔA is the measured attenuation, α is the acoustic absorption coefficient, d is the transmission distance, k1 and k2 are material calibration coefficients, δ(f) is the linear relationship between the skin effect depth δ of the electrical signal and the frequency, and Δf is the pulse frequency offset; The least square solution of the equation is obtained along the cable axis, and the attenuation mutation point is taken as the candidate failure location.

4. The cable partial discharge detection method according to claim 1, characterized in that: The process of establishing the acoustic-electrical comprehensive attenuation curve specifically includes the following steps: For each pair of adjacent sampling sensor groups, extract the peak voltage value of the pulse signal detected by the current sensor of the group and convert it into a standard decibel value as a first basic attenuation index; Extract the sound wave pulse pressure values detected by the ultrasonic sensors in the same group and convert them into standard decibel values as the second basic attenuation index. Calculate the decibel attenuation change of the current group relative to the upstream adjacent group to generate an attenuation data sequence distributed along the cable axis. At the same axial position point, the proportional relationship between the first basic attenuation index and the second basic attenuation index is defined as the acoustic-electric attenuation factor. The acoustic-electric attenuation factors connecting all sampling points are fitted using the cubic spline interpolation algorithm to form a continuous and conductive acoustic-electric comprehensive attenuation curve.

5. The cable partial discharge detection method according to claim 4, characterized in that: The process of establishing the acoustic-electrical comprehensive attenuation curve also includes the following steps: During the period when no discharge occurs in the cable, the background electrical noise intensity of the current sensor channel is measured and converted into a standard decibel measurement value. The ambient vibration noise intensity of the ultrasonic sensor channel is also measured and converted into a standard decibel measurement value. Calculate the ratio of the two background noise decibel values as the acoustic and electrical attenuation benchmark coefficient under background conditions; When the deviation between the acoustic and electrical attenuation coefficient of the measured discharge event and the background reference coefficient exceeds a specific ratio, it is adopted as a valid data point. All data points that do not meet this condition are deleted, and the curve is reconstructed using the interpolation calculation results of adjacent valid data points.

6. The cable partial discharge detection method according to claim 3, characterized in that: For the candidate failure location, measure the phase-resolved spectrum of the partial discharge pulse at the abnormal point; When the graph presents a floating potential discharge feature and the repetition rate is higher than a preset value, the failure position candidate point is confirmed to be a failure position.

7. A cable partial discharge detection system, suitable for implementing the method according to any one of claims 1 to 6, characterized in that: include: a sensor array distributed at equal intervals along the cable, comprising a plurality of sampling sensor groups; a data receiving module configured to receive high-frequency current signals and ultrasonic signals from the sampling sensor group; The data processing module is configured to receive the data from the data receiving module and perform pre-processing to determine the failure location.

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