Partial discharge positioning method and system based on multi-point synchronous distributed detection, and medium

Abstract

The invention relates to the technical field of high-voltage cable online monitoring, in particular to a partial discharge positioning method and system based on multi-point synchronous distributed detection and a medium. The method comprises the following steps: firstly, initially determining the position of a partial discharge source by using a multi-point synchronous distributed sensor, and then providing a high-precision partial discharge signal positioning method based on a phase difference algorithm. According to the partial discharge signal time delay estimation based on the phase difference, the time difference of arrival of the partial discharge signals is estimated by calculating the phase difference of the cross-correlation density functions of the two partial discharge signals from the same source in the frequency domain, so that the estimation of the time of arrival of the partial discharge signals and the influence of noise in the environment are effectively avoided; the method effectively solves the problems of uncertainty of partial discharge signal wave velocity and low positioning precision, and can still have high positioning precision even in a low signal-to-noise ratio environment.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage cable online monitoring, and in particular to a local discharge positioning method, system and medium based on multi-point synchronous distributed detection. Background Art

[0002] High-voltage cables occupy an increasingly large proportion in urban power transmission networks, and their operating status directly affects the reliability of the power supply network of the power system. High-voltage cables are prone to cable insulation breakdown accidents under factors such as external force damage, latent defects at the factory, and long-term high-current operation. Their insulation conditions directly affect the reliability and stability of the power system. Partial discharge (PD) is an important manifestation of the initial degradation and internal defects of cable insulation. Therefore, PD detection technology is an important means to effectively evaluate the operating status of high-voltage cable insulation. The location of discharge defects has important guiding significance for the evaluation of insulation defects and efficient fault repair. At present, due to the complex propagation attenuation of discharge signals in cable lines and the influence of refraction and reflection, the accuracy of existing PD positioning methods still cannot meet actual engineering needs.

[0003] The existing methods for detecting partial discharge in high-voltage cables mainly include high-frequency current method, capacitive coupling method, ultrasonic inspection and ultra-high frequency method. Almost all detection methods require the installation of sensors in the high-voltage cable, which means that the measurement of partial discharge signals can only be performed at a limited number of points. In theory, partial discharge faults in high-voltage cables may exist at any position (the middle joint or body of the high-voltage cable). This leads to the problems of low positioning accuracy and uncertain wave velocity of partial discharge signals in existing partial discharge detection methods for high-voltage cables. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a partial discharge positioning method, system and medium based on multi-point synchronous distributed detection. By utilizing the multi-point synchronous distributed partial discharge detection technology, a high-precision partial discharge signal positioning method based on a phase difference algorithm is proposed, which effectively solves the problems of uncertainty in the wave velocity of the partial discharge signal and low positioning accuracy, and can still have high positioning accuracy even in a low signal-to-noise ratio environment.

[0005] In order to solve the technical problem, the technical solution adopted by the present invention is: a partial discharge locating method based on multi-point synchronous distributed detection, comprising the following steps: S01. Installing sensors on the cable, the sensors include a high-frequency current transformer installed at the middle joint of the cable and a built-in current sensor installed in the cable body, and the sensors are used to detect partial discharge pulses; S02, receiving the partial discharge pulses detected by each sensor, selecting the two sensors with the largest and second largest partial discharge pulses, and preliminarily locating the partial discharge source between the two sensors. The two sensors are respectively denoted as A1 and A2, and the distance between them is denoted as , then the distance between the partial discharge source and sensor A1 The calculation formula is: (1), in is the time difference between the sensors A1 and A2 detecting the partial discharge signal. is the propagation speed of the partial discharge pulse in the high voltage cable; S03, calculate the phase difference of the cross-correlation density function of the two partial discharge signals from the partial discharge source in the frequency domain, and estimate the time difference between the sensors A1 and A2 detecting the partial discharge signals based on the relationship between the phase difference and the arrival time difference of the partial discharge signals. , the estimated time difference between the detection of partial discharge signals by sensors A1 and A2 Substitute into formula (1) to calculate the location of the partial discharge source.

[0006] Furthermore, step S03 is specifically as follows: S31, select the partial discharge signal in the time window T and , after Fourier transform, we get the partial discharge signal in the frequency domain , : , Where f is the frequency of the partial discharge signal, and n is the number of partial discharge signal acquisitions; S32. Calculate the cross-spectral density function of the two partial discharge signals. The formula is: , in for The optimal solution of S33, the cross spectral density function Written as a complex expression, the formula is: , in Indicates partial discharge signal , The phase difference is calculated according to the formula ; S34, Time difference of arrival with partial discharge signal The relationship formula is: ; Then the location of the partial discharge source is: .

[0007] Furthermore, the phase difference between the partial discharge signals is obtained through the relationship between frequency and phase in the cross-spectral density function. When the actual phase values ​​exceed this range, they will be "folded back" Within the range, this causes discontinuous phase jumps at the boundary, so it is considered that the phase is folded. The phase unwrapping algorithm is used to eliminate the phase folding phenomenon to obtain the optimal phase difference. , and the optimal phase difference is obtained The process is: A. Calculation The difference between the second point and the previous point; B. If the absolute value difference is less than , the two point values ​​will not be changed; C. If the absolute value difference is greater than or equal to , then increase the value at one of the points , until the absolute value difference is less than ; D. Repeat the above steps until all .

[0008] Furthermore, the formula for determining the time window T is: , in , are the starting sampling points and the ending sampling points respectively. is the compensation coefficient, is the sampling rate.

[0009] Furthermore, , in is the distance between sensor A3 and sensor A1. Sensor A3 is another sensor adjacent to sensor A2. It is the time difference between sensors A2 and A3 detecting the partial discharge signal.

[0010] Furthermore, A1 and A3 are high-frequency current transformers installed at the middle joint of the cable, and A2 is a built-in current sensor located between A1 and A3.

[0011] The present invention also discloses a local discharge locating system based on multi-point synchronous distributed detection, comprising a processor and a memory storing program instructions, wherein the processor is configured to execute the local discharge locating method based on multi-point synchronous distributed detection as described above when running the program instructions.

[0012] The present invention also discloses a storage medium storing program instructions, which, when running, execute the above-mentioned local discharge locating method based on multi-point synchronous distributed detection.

[0013] Beneficial effects of the present invention: The present invention adopts distributed means to realize long-distance high-voltage cable fault monitoring, and can more accurately and timely discover the safety hazards existing in the operation of high-voltage cables, which has important engineering practical value for preventing accidents. The phase difference-based partial discharge signal delay estimation realizes the estimation of the arrival time difference of the partial discharge signal by calculating the phase difference of the cross-correlation density function of two partial discharge signals from the same source in the frequency domain, which effectively avoids the estimation of the arrival time of the partial discharge signal and the influence of environmental noise. Multi-point synchronous partial discharge positioning technology is a fault positioning method that does not require the prior determination of the traveling wave velocity or the use of empirical wave velocity, and effectively solves the problem of cable partial discharge wave velocity uncertainty caused by cable structure and signal characteristic factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of installing the sensor in Example 1; Figure 2 This is a flow chart of partial discharge positioning in Example 1; In the figure, 1 represents the cable, 2 represents the partial discharge source, 3 represents the middle joint of the cable, A2 represents the built-in sensor, and A1 and A3 represent the high-frequency current transformers located at the middle joint of the cable. DETAILED DESCRIPTION

[0015] In order to be able to understand the features and technical contents of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, to simplify the drawings, well-known structures and devices can be simplified for display.

[0016] The terms "first", "second", etc. in the embodiments of the present disclosure are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so as to describe the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0017] Unless otherwise stated, the term "plurality" means two or more.

[0018] In the embodiment of the present disclosure, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B indicates: A or B.

[0019] The term "and / or" is a description of the association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0020] The term "correspondence" may refer to an association relationship or a binding relationship. The correspondence between A and B means that there is an association relationship or a binding relationship between A and B.

[0021] Example 1 This embodiment discloses a partial discharge locating method based on multi-point synchronous distributed detection. The multi-point synchronous partial discharge locating technology is a fault locating method that does not require the prior determination of the traveling wave velocity or the use of empirical wave velocity, and effectively solves the problem of cable partial discharge wave velocity uncertainty caused by cable structure and signal characteristic factors.

[0022] This method first performs multi-sensor installation, such as Figure 1 As shown, the sensor includes high-frequency current transformers A1 and A3 installed at the middle joint 3 of the cable 1 and a built-in current sensor A2 installed in the cable body. The sensor is used to detect partial discharge pulses. The distance between A1 and A3 is L2, and the distance between A1 and A2 is In practice, there are multiple cables 1 with intermediate connectors 3. Figure 1 A portion of it is shown in .

[0023] Receive the partial discharge pulses detected by each sensor, select the two sensors with the largest and second largest partial discharge pulses, and preliminarily locate the partial discharge source between the two sensors. Assuming that the partial discharge source 2 is located between sensors A1 and A2, the distance between the partial discharge source and sensor A1 is The calculation formula is: (1), in is the time difference between the sensors A1 and A2 detecting the partial discharge signal. is the propagation speed of the partial discharge pulse in the high voltage cable.

[0024] The arrival time difference of the partial discharge signals detected by sensors A2 and A3 is calculated synchronously: , find the speed for: .

[0025] This embodiment uses the phase difference method of partial discharge positioning to calculate the time difference between two partial discharge signals. , calculate the phase difference of the cross-correlation density function of the two partial discharge signals from the partial discharge source in the frequency domain, and estimate the time difference when sensors A1 and A2 detect the partial discharge signals based on the relationship between the phase difference and the arrival time difference of the partial discharge signals , the estimated time difference between the detection of partial discharge signals by sensors A1 and A2 Substitute into formula (1) to calculate the location of the partial discharge source.

[0026] In this embodiment, the phase difference method for partial discharge positioning is specifically: S31, select the partial discharge signal in the time window T and , after Fourier transform, we get the partial discharge signal in the frequency domain , : , Where f is the frequency of the partial discharge signal, and n is the number of partial discharge signal acquisition times.

[0027] S32. Calculate the cross-spectral density function of the two partial discharge signals. The formula is: , in for The optimal solution of .

[0028] S33, the cross spectral density function Written as a complex expression, the formula is: , in Indicates partial discharge signal , The phase difference is calculated according to the formula ; S34, Time difference of arrival with partial discharge signal The relationship formula is: ; Then the location of the partial discharge source is: .

[0029] The phase difference between the partial discharge signals is obtained by the relationship between frequency and phase in the cross-spectral density function. When the calculated partial discharge signal phase value range is not When the actual phase values ​​exceed this range, they will be "folded back" Within the range, this causes discontinuous phase jumps at the boundary, so it is considered that the phase is folded. The phase unwrapping algorithm is used to eliminate the phase folding phenomenon to obtain the optimal phase difference. , and the optimal phase difference is obtained : A. Calculation The difference between the second point and the previous point (because there are n partial discharge signal collection points, there are also multiple ); B. If the absolute value difference is less than , the two point values ​​will not be changed; C. If the absolute value difference is greater than or equal to , then increase the value at one of the points , until the absolute value difference is less than ; D. Repeat the above steps until all .

[0030] In order to ensure complete coverage of partial discharge pulses, a method for selecting the time window T based on the partial discharge signal energy is proposed. According to Parseval's theorem, the partial discharge energy is expressed as follows: ; in Represents the partial discharge signal, and n is the number of partial discharge signal acquisition times.

[0031] By adjusting the value of n, the local energy per unit length can be calculated. Since the energy of the partial discharge signal is high, the unit increment of the energy of the measurement signal containing the partial discharge signal will reach the maximum.

[0032] The formula for determining the time window T is: , in , are the starting sampling points and the ending sampling points respectively. is the compensation coefficient, is the sampling rate.

[0033] The specific process of the method described in this embodiment is as follows Figure 2 As shown, this method can realize long-distance high-voltage cable fault monitoring by distributed means, and can more accurately and timely discover the safety hazards existing in the operation of high-voltage cables, which has important engineering practical value for preventing accidents. Compared with the prior art, the method of the present invention effectively solves the problems of uncertainty of partial discharge signal wave velocity and low positioning accuracy, improves the anti-interference ability, and can locate the position of the defective section of the high-voltage cable with high precision, which provides convenience for the maintenance and repair of the equipment.

[0034] Example 2 This embodiment discloses a partial discharge location system based on multi-point synchronous distributed detection, including a processor and a memory. Optionally, the device may also include a communication interface and a bus 3. The processor, the communication interface, and the memory communicate with each other through the bus. The communication interface is used for information transmission. The processor 3 calls the logic instructions in the memory to execute the partial discharge location method based on multi-point synchronous distributed detection of the above-mentioned embodiment 1.

[0035] In addition, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product.

[0036] The memory, as a computer-readable storage medium, can be used to store software programs and computer executable programs, such as program instructions / modules corresponding to the method in the embodiment of the present disclosure. The processor executes the function application and data processing by running the program instructions / modules stored in the memory, that is, the partial discharge location method based on multi-point synchronous distributed detection in the above embodiment is realized.

[0037] The memory includes a program storage area and a data storage area, wherein the program storage area can store an operating system and an application required for at least one function; the data storage area can store data created according to the use of the terminal device, etc. In addition, the memory can include a high-speed random access memory and can also include a non-volatile memory.

[0038] Example 3 An embodiment of the present disclosure provides a computer-readable storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured to execute the above-mentioned partial discharge location method based on multi-point synchronous distributed detection.

[0039] The computer-readable storage medium mentioned above may be a transient computer-readable storage medium or a non-transitory computer-readable storage medium.

[0040] The technical solution of the embodiment of the present disclosure can be embodied in the form of a software product, which is stored in a storage medium and includes one or more instructions for enabling a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the embodiment of the present disclosure. The aforementioned storage medium may be a non-transient storage medium, including: a USB flash drive, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a disk or an optical disk, and other media that can store program codes, or a transient storage medium.

[0041] The above description and the accompanying drawings fully illustrate the embodiments of the present disclosure so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The embodiments represent only possible changes. Unless explicitly required, separate components and functions are optional, and the order of operation may vary. The parts and features of some embodiments may be included in or replace the parts and features of other embodiments. Moreover, the words used in this application are only used to describe the embodiments and are not used to limit the scope of protection. As used in the description in the text, unless the context clearly indicates, the singular forms of "a", "an" and "the" are intended to include plural forms as well. Similarly, the term "and / or" as used in this application refers to any and all possible combinations of one or more associated listings. In addition, when used in this application, the term "comprise" and its variants "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, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method or device including the elements. In this article, each embodiment may focus on the differences from other embodiments, and the same and similar parts between the embodiments may refer 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 refer to the description of the method part.

[0042] 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 functions 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 to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the embodiments of the present disclosure. The technicians may clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here.

Claims

1. A method for locating partial discharge based on multi-point synchronous distributed detection, characterized in that: The following steps are involved: S01. Installing sensors on the cable, the sensors include a high-frequency current transformer installed at the middle joint of the cable and a built-in current sensor installed in the cable body, and the sensors are used to detect partial discharge pulses; S02, receiving the partial discharge pulses detected by each sensor, selecting the two sensors with the largest and second largest partial discharge pulses, and preliminarily locating the partial discharge source between the two sensors. The two sensors are respectively denoted as A1 and A2, and the distance between them is denoted as , then the distance between the partial discharge source and sensor A1 The calculation formula is: （1）， in is the time difference between the sensors A1 and A2 detecting the partial discharge signal. is the propagation speed of the partial discharge pulse in the high voltage cable; S03, calculate the phase difference of the cross-correlation density function of the two partial discharge signals from the partial discharge source in the frequency domain, and estimate the time difference between the partial discharge signals detected by sensors A1 and A2 based on the relationship between the phase difference and the arrival time difference of the partial discharge signals. , the estimated time difference between the detection of partial discharge signals by sensors A1 and A2 Substitute into formula (1) to calculate the location of the partial discharge source.

2. The method for locating partial discharge based on multi-point synchronous distributed detection according to claim 1, characterized in that: Step S03 is specifically as follows: S31, select the partial discharge signal in the time window T and , after Fourier transform, we get the partial discharge signal in the frequency domain , : ， Where f is the frequency of the partial discharge signal, n is the number of partial discharge signal acquisitions, S32. Calculate the cross-spectral density function of the two partial discharge signals. The formula is: ， in for The optimal solution of S33, the cross spectral density function Written as a complex expression, the formula is: ， in Indicates partial discharge signal , The phase difference is calculated according to the formula ; S34, Time difference of arrival with partial discharge signal The relationship formula is: ； Then the location of the partial discharge source is: 。 3. The method for locating partial discharge based on multi-point synchronous distributed detection according to claim 2, characterized in that: The phase difference between the partial discharge signals is obtained by the relationship between frequency and phase in the cross-spectral density function. When the calculated partial discharge signal phase value range is not When , it is considered that the phase is folded, and the phase unwrapping algorithm is used to eliminate the phase folding phenomenon to obtain the optimal phase difference , and the optimal phase difference is obtained The process is: A. Calculation The difference between the second point and the previous point; B. If the absolute value difference is less than , the two point values ​​will not be changed; C. If the absolute value difference is greater than or equal to , then increase the value at one of the points , until the absolute value difference is less than ; D. Repeat the above steps until all .

4. The method for locating partial discharge based on multi-point synchronous distributed detection according to claim 2, characterized in that: The formula for determining the time window T is: ， in , are the starting sampling points and the ending sampling points respectively. is the compensation coefficient, is the sampling rate.

5. The method for locating partial discharge based on multi-point synchronous distributed detection according to claim 1, characterized in that: , in is the distance between sensor A3 and sensor A1. Sensor A3 is another sensor adjacent to sensor A2. It is the time difference between sensors A2 and A3 detecting the partial discharge signal.

6. The method for locating partial discharge based on multi-point synchronous distributed detection according to claim 5, characterized in that: A1 and A3 are high-frequency current transformers installed at the middle joint of the cable, and A2 is a built-in current sensor located between A1 and A3.

7. A partial discharge location system based on multi-point synchronous distributed detection, comprising a processor and a memory storing program instructions, characterized in that: The processor is configured to execute the partial discharge location method based on multi-point synchronous distributed detection as claimed in any one of claims 1 to 6 when running the program instructions.

8. A storage medium storing program instructions, characterized in that: When the program instructions are executed, the partial discharge location method based on multi-point synchronous distributed detection as described in any one of claims 1 to 6 is executed.

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