Partial discharge signal detection method based on power frequency voltage transformer and related product

Abstract

The invention discloses a partial discharge signal detection method based on a power frequency voltage transformer and a related product, and belongs to the technical field of insulation detection. The method comprises the following steps: acquiring a power grid side actual voltage signal of a power distribution network cable terminal by means of a power frequency voltage transformer, preprocessing to obtain an original partial discharge signal, and performing discrete time Fourier transform on the original partial discharge signal to obtain a z-domain signal of the original partial discharge signal; fitting the frequency domain response of the power frequency voltage transformer to obtain a z-domain inverse transfer function; and performing digital compensation on the z-domain signal of the original partial discharge signal by using the z-domain inverse transfer function to obtain a compensated z-domain signal, and converting the compensated z-domain signal to a time domain through inverse z transformation to obtain a final original partial discharge signal. Voltage signals are acquired through the original power frequency voltage transformer of the power distribution network, frequency band limitation of the power frequency voltage transformer is overcome through digital compensation, and live detection and online real-time monitoring of partial discharge signals of the power distribution network cable can be realized without power failure and additional installation of the transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of insulation detection, and particularly to a method for detecting partial discharge signals based on a power frequency voltage transformer and related products. Background Art

[0002] Partial discharge is one of the early manifestations of the deterioration of the insulation of power equipment, and is also an important cause leading to further deterioration of the insulation. Its situation can predict the insulation life of power equipment and is an important power equipment condition assessment index. Taking the distribution network cable as an example, as a key device for realizing long-distance energy transmission in the distribution network, its reliability directly affects the power consumption situation in a region. Due to reasons such as increased service life, improper construction, and external force damage, distribution network cables often fail or even explode. According to incomplete statistics, more than 90% of the faults of distribution network cables are insulation faults. Therefore, the assessment of the cable insulation state is crucial.

[0003] Currently, the detection of partial discharge signals is the most common and effective way to evaluate the insulation state of cables. However, due to the characteristics of partial discharge itself, such as randomness, variability, poor anti-interference ability, and complexity, the technology for detecting partial discharge signals has not yet developed to the level expected by people. Traditional partial discharge signal detection mostly uses off-line detection methods. However, with the increasing requirements for the power supply reliability and continuity of the distribution network, the cable cannot be overhauled while powered off, and the off-line detection method has obvious limitations. The high-frequency current transformer has high sensitivity and large bandwidth, and is suitable for installation on the connecting wire or the core of the distribution network cable. In the prior art, although there is also a live detection method using HFCT (High - Frequency Current Transformer), the installation position of the high-frequency current transformer is limited. In many cases, the connecting wire is encapsulated in the high-voltage compartment of the switch cabinet and cannot be obtained while powered on. It must be installed by shutting down the distribution network cable, resulting in its difficult application and promotion.

[0004] Therefore, how to provide a live detection method for partial discharge signals of distribution network cables without shutdown has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting partial discharge signals based on a power frequency voltage transformer and related products to overcome the problem that the high-frequency current transformer needs to be installed while powered off and cannot meet the high-reliability power supply requirements of the distribution network.

[0006] The present invention solves the above technical problems through the following technical solutions: The present invention provides a method for detecting partial discharge signals based on a power frequency voltage transformer, including the following steps: S1. Obtain the frequency-domain response of the original power-frequency voltage transformer in the distribution network through the frequency-sweeping method; S2. Collect the actual voltage signal on the grid side of the cable terminal in the distribution network through the power-frequency voltage transformer, preprocess the actual voltage signal on the grid side to obtain the original partial discharge signal, and perform discrete-time Fourier transform on the original partial discharge signal to obtain the z-domain signal of the original partial discharge signal; S3. Fit the frequency-domain response to obtain the transfer function, and calculate the inverse transfer function in the z-domain according to the transfer function; S4. Perform digital compensation on the z-domain signal of the original partial discharge signal using the inverse transfer function in the z-domain to obtain the z-domain signal of the compensated original partial discharge signal, and use the inverse z-transform to convert the z-domain signal of the compensated original partial discharge signal to the time domain to obtain the final original partial discharge signal.

[0007] A further improvement of the present invention is that: the step S1 specifically includes the following steps: Inject sine signals with different frequencies into the primary side of the original power-frequency voltage transformer in the distribution network, obtain the amplitude of the secondary side output waveform of the power-frequency voltage transformer, and calculate the frequency-domain response of the power-frequency voltage transformer based on the sine signals with different frequencies injected into the primary side and the amplitude of the secondary side output waveform; The step S1 further includes the following steps: Based on the frequency-domain response of the power-frequency voltage transformer, determine whether the sensitivity of the power-frequency voltage transformer meets the preset requirements. If the determination is yes, execute step S2; if the determination is no, replace the power-frequency voltage transformer with a sensitivity that meets the preset requirements.

[0008] A further improvement of the present invention is that: the sine signals with different frequencies are specifically: 5 kHz to 20 MHz; the preset requirements are specifically: the sensitivity of the power-frequency voltage transformer is not less than -20 dB at 5 MHz to 20 MHz.

[0009] A further improvement of the present invention is that: the transfer function is specifically:

[0010] Wherein, is the transfer function; is the number of real poles; and are the coefficients related to the th real pole; is the sampling period; is the first delay operator in the transformation, indicating that the sequence is delayed by one sampling period; and are the number of pairs of complex poles; The molecular coefficients related to a complex pole; , , are the denominator coefficients related to the th complex pole; The inverse transfer function in the z-domain is specifically:

[0011] where is the inverse transfer function in the z-domain; is the z-domain signal of the compensated original partial discharge signal; is the z-domain signal of the original partial discharge signal; , , and are the coefficients related to the th real pole in the z-domain; , and are the molecular coefficients related to the th complex pole in the z-domain; , and are the denominator coefficients related to the th complex pole in the z-domain; is the second delay operator in the z-transform, indicating that the sequence is delayed by two sampling periods.

[0012] A further improvement of the present invention is that it further includes step S5: uploading the final original partial discharge signal to the cloud database; In step S2, the preprocessing of the actual voltage signal on the power grid side is specifically: filtering and noise reduction are sequentially performed on the actual voltage signal on the power grid side.

[0013] A further improvement of the present invention is that the conversion of the z-domain signal of the compensated original partial discharge signal to the time domain by using the inverse z-transform to obtain the final original partial discharge signal is specifically: The z-domain signal of the compensated original partial discharge signal is converted to the time domain by using the inverse z-transform to obtain the compensated original partial discharge signal, and the empirical mode decomposition method is used to smooth the compensated original partial discharge signal to obtain the final original partial discharge signal.

[0014] A further improvement of the present invention is that the digital compensation is specifically:

[0015] where is the z-domain signal of the compensated original partial discharge signal; is the z-domain signal of the original partial discharge signal; is the inverse transfer function in the z-domain.

[0016] The present invention also provides a partial discharge signal detection device based on a power frequency voltage transformer, which obtains partial discharge signals by using the partial discharge signal detection method based on a power frequency voltage transformer as described above. The partial discharge signal detection device based on a power frequency voltage transformer includes: A power frequency voltage transformer, a high-pass filter, an analog-to-digital conversion unit, a microprocessor, a storage unit, a network unit, and a display. Among them, a power frequency voltage transformer is provided on the distribution network where the partial discharge signal to be measured is located. The output end of the power frequency voltage transformer is connected to the input end of the high-pass filter, and the output end of the high-pass filter is connected to the microprocessor. The analog-to-digital conversion unit, the storage unit, the network unit, and the display are respectively electrically connected to the microprocessor; The high-pass filter is used to extract the high-frequency analog signal of the actual voltage signal on the grid side; The analog-to-digital conversion unit is used to convert the high-frequency analog signal into a digital signal; The storage unit is used to store the final original partial discharge signal; The network unit is used to upload the final original partial discharge signal to the cloud database; The display is used to display the final original partial discharge signal in real time.

[0017] The present invention also provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the partial discharge signal detection method based on a power frequency voltage transformer as described above are implemented.

[0018] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the partial discharge signal detection method based on a power frequency voltage transformer as described above are implemented.

[0019] Compared with the prior art, the positive and progressive effects of the present invention are as follows: The partial discharge signal detection method based on a power frequency voltage transformer provided by the present invention collects the actual voltage signal on the grid side of the distribution network cable terminal by means of the power frequency voltage transformer, obtains the original partial discharge signal through preprocessing, and then performs a discrete-time Fourier transform on it to obtain the z-domain signal of the original partial discharge signal; fits the frequency-domain response of the power frequency voltage transformer to obtain the inverse z-transfer function in the z-domain; uses the inverse z-transfer function in the z-domain to digitally compensate the z-domain signal of the original partial discharge signal to obtain the compensated z-domain signal, and then converts it to the time domain through an inverse z-transform to obtain the final original partial discharge signal. The power frequency voltage transformer belongs to the conventional protection equipment of the distribution network and is always in a live operation state without the need for outage installation. This method relies on the original power frequency voltage transformer of the distribution network to collect voltage signals and overcomes the bandwidth limitation of the power frequency voltage transformer through digital compensation, enabling real-time coupling of the voltage signal at the cable terminal under live operation conditions. It not only realizes the live detection of the partial discharge signal of the distribution network cable, but also, due to the need for no disassembly and installation of the power frequency voltage transformer, realizes online real-time monitoring. Using this method can effectively solve the problems of the need for power outage operations in traditional partial discharge detection and the need for outage installation of high-frequency current transformers, meeting the high-reliability power supply requirements of the distribution network.

[0020] Further, judging whether the sensitivity meets the preset requirements based on the frequency-domain response can ensure that the selected power frequency voltage transformer can accurately capture the partial discharge signal in the target frequency band, avoiding signal omission or misjudgment caused by the performance mismatch of the power frequency voltage transformer, thereby improving the accuracy of detection.

[0021] Further, in the actual operation of the power grid, the voltage signal is easily affected by power frequency harmonics, switching operation transients, electromagnetic environment noise, etc. Through filtering and noise reduction processing, the noise in the frequency bands irrelevant to the partial discharge signal (such as clutter other than the power frequency fundamental wave) can be removed, avoiding the drowning of the discharge signal by noise, and ensuring that only the effective signal components are retained in the original data for subsequent detection; the detection of partial discharge signals requires long-term monitoring of the insulation state, and the amount of original signal data is huge. Uploading it to the cloud database can achieve real-time monitoring and avoid data loss caused by insufficient local storage capacity or hardware failures. Description of the Drawings

[0022] The accompanying drawings in the specification are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0023] Figure 1 It is a schematic flow chart of the partial discharge signal detection method based on a power frequency voltage transformer of the present invention; Figure 2 It is a schematic connection diagram of the partial discharge signal detection device based on a power frequency voltage transformer of the present invention; Figure 3 Schematic diagram of the amplitude-frequency response curve of the power frequency voltage transformer; Figure 4 Frequency domain spectrum of the partial discharge signal; Figure 5 Pulse injection response waveform diagram of the power frequency voltage transformer. Specific implementation mode

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. The components of the embodiments of the present invention usually described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0026] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0027] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0028] In addition, it should be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The following further elaborates on the present invention in conjunction with the accompanying drawings and specific embodiments, which is an explanation of the present invention rather than a limitation.

[0030] See Figure 1 , a method for detecting partial discharge signals based on a power frequency voltage transformer, comprising the following steps: S1. Obtain the frequency domain response of the original power frequency voltage transformer in the distribution network through the frequency sweeping method; S2. Collect the actual voltage signal on the grid side of the cable terminal in the distribution network through the power frequency voltage transformer, preprocess the actual voltage signal on the grid side to obtain the original partial discharge signal, perform discrete-time Fourier transform on the original partial discharge signal to obtain the z-domain signal of the original partial discharge signal; S3. Fit the frequency domain response to obtain the transfer function, and calculate the inverse transfer function in the z-domain according to the transfer function; S4. Use the inverse transfer function in the z-domain to digitally compensate the z-domain signal of the original partial discharge signal to obtain the z-domain signal of the compensated original partial discharge signal, and use the inverse z-transform to convert the z-domain signal of the compensated original partial discharge signal to the time domain to obtain the final original partial discharge signal.

[0031] This method uses a power frequency voltage transformer to collect the actual voltage signal on the grid side of the cable terminal in the distribution network. After preprocessing, the original partial discharge signal is obtained, and then discrete-time Fourier transform is performed on it to obtain the z-domain signal of the original partial discharge signal; the frequency domain response of the power frequency voltage transformer is fitted to obtain the inverse transfer function in the z-domain; the inverse transfer function in the z-domain is used to digitally compensate the z-domain signal of the original partial discharge signal to obtain the compensated z-domain signal, and then it is converted to the time domain through the inverse z-transform to obtain the final original partial discharge signal. The power frequency voltage transformer belongs to the conventional protection equipment of the distribution network and is always in the live operation state without the need for outage installation. This method collects voltage signals through the original power frequency voltage transformer in the distribution network and overcomes the band limitation of the power frequency voltage transformer through digital compensation. It can couple the voltage signal of the cable terminal in real time without power outage, not only realizing the live detection of the partial discharge signal of the distribution network cable, but also realizing online real-time monitoring, and solving the problems that the traditional partial discharge detection requires power outage operation and the high-frequency current transformer needs outage installation, which cannot meet the high-reliability power supply requirements of the distribution network.

[0032] Specifically, the step S1 specifically includes the following steps: Inject sine signals with different frequencies into the primary side of the original power frequency voltage transformer in the distribution network, obtain the amplitude of the output waveform on the secondary side of the power frequency voltage transformer, and calculate the frequency domain response of the power frequency voltage transformer based on the sine signals with different frequencies injected into the primary side and the amplitude of the output waveform on the secondary side; The step S1 further includes the following steps: Based on the frequency-domain response of the power-frequency voltage transformer, determine whether the sensitivity of the power-frequency voltage transformer meets the preset requirements. If the determination is yes, execute step S2; if the determination is no, replace the power-frequency voltage transformer with a sensitivity that meets the preset requirements.

[0033] Judging whether the sensitivity meets the preset requirements based on the frequency-domain response can ensure that the selected power-frequency voltage transformer can accurately capture the partial discharge signals in the target frequency band, avoiding signal omission or misjudgment caused by the mismatch of the performance of the power-frequency voltage transformer, thereby improving the accuracy of detection.

[0034] Specifically, the sine signals of different frequencies are: 5 kHz to 20 MHz; the preset requirements are specifically: the sensitivity of the power-frequency voltage transformer is not less than -20 dB in the range of 5 MHz to 20 MHz.

[0035] Specifically, the transfer function is specifically:

[0036] Where, is the transfer function; is the number of real poles; and are the coefficients related to the th real pole; is the sampling period; is the first delay operator in the transformation, indicating that the sequence is delayed by one sampling period; and are the numerator coefficients related to the th complex pole; 、 、 are the denominator coefficients related to the th complex pole; The inverse z-domain transfer function is specifically:

[0037] Where, is the inverse z-domain transfer function; is the z-domain signal of the compensated original partial discharge signal; is the z-domain signal of the original partial discharge signal; 、 、 and are the coefficients related to the th real pole in the z-domain; 、 and are the coefficients related to the The molecular coefficients related to a complex pole; and and are the denominator coefficients related to the th complex pole in the z-domain; is the second delay operator in the

[0038] Specifically, it further includes step S5: uploading the final original partial discharge signal to the cloud database; In step S2, the preprocessing of the actual grid-side voltage signal is specifically: filtering and noise reduction are sequentially performed on the actual grid-side voltage signal.

[0039] During the actual operation of the power grid, the voltage signal is vulnerable to the influence of power frequency harmonics, switching operation transient interference, electromagnetic environment noise, etc. Through filtering and noise reduction processing, the band noise irrelevant to the partial discharge signal (such as clutter other than the power frequency fundamental wave) can be removed, avoiding the drowning of the discharge signal by noise, and ensuring that only the effective signal components are retained in the original data for subsequent detection; the detection of partial discharge signals requires long-term monitoring of the insulation status, and the amount of original signal data is huge. Uploading to the cloud database can achieve real-time monitoring and avoid data loss caused by insufficient local storage capacity or hardware failures.

[0040] Specifically, the process of converting the z-domain signal of the compensated original partial discharge signal to the time domain by using the inverse z-transform to obtain the final original partial discharge signal is specifically: The z-domain signal of the compensated original partial discharge signal is converted to the time domain by using the inverse z-transform to obtain the compensated original partial discharge signal, and the empirical mode decomposition method is used to smooth the compensated original partial discharge signal to obtain the final original partial discharge signal. This method is only a digital compensation algorithm process available for practice and can be used as a reference for on-site testing. The detection effect of partial discharge signals can be better optimized by designing targeted algorithms for on-site conditions.

[0041] Specifically, the digital compensation is specifically:

[0042] where is the z-domain signal of the compensated original partial discharge signal; is the z-domain signal of the original partial discharge signal; is the inverse transfer function in the z-domain.

[0043] Based on the same inventive concept, the present invention further provides a partial discharge signal detection device based on a power frequency voltage transformer, which uses the partial discharge signal detection method based on a power frequency voltage transformer as described above to obtain partial discharge signals. The partial discharge signal detection device based on a power frequency voltage transformer includes: A power frequency voltage transformer, a high-pass filter, an analog-to-digital conversion unit, a microprocessor, a storage unit, a network unit, and a display. Among them, a power frequency voltage transformer is provided on the distribution network where the partial discharge signal to be measured is located. The output end of the power frequency voltage transformer is connected to the input end of the high-pass filter, and the output end of the high-pass filter is connected to the microprocessor. The analog-to-digital conversion unit, the storage unit, the network unit, and the display are respectively electrically connected to the microprocessor; The high-pass filter is used to extract the high-frequency analog signal of the actual voltage signal on the grid side; The analog-to-digital conversion unit is used to convert the high-frequency analog signal into a digital signal; The storage unit is used to store the final original partial discharge signal; The network unit is used to upload the final original partial discharge signal to the cloud database; The display is used to display the final original partial discharge signal in real time.

[0044] Embodiment 1 Refer to Figure 2 , a partial discharge signal detection device based on a power frequency voltage transformer, includes a high-voltage detection unit and a data acquisition and control unit. The high-voltage detection unit includes a power frequency voltage transformer and a high-pass filter; the data acquisition and control unit includes an analog-to-digital conversion unit, a microprocessor, a storage unit, a network unit, and a display; a power frequency voltage transformer, a high-pass filter, an analog-to-digital conversion unit, a microprocessor, a storage unit, a network unit, and a display. Among them, a power frequency voltage transformer is provided on the distribution network where the partial discharge signal to be measured is located. The output end of the power frequency voltage transformer is connected to the input end of the high-pass filter, and the output end of the high-pass filter is connected to the microprocessor. The analog-to-digital conversion unit, the storage unit, the network unit, and the display are respectively electrically connected to the microprocessor.

[0045] Among them, the power frequency voltage transformer comes from the electromagnetic voltage transformer sold on the market. The high-frequency bandwidth of this power frequency voltage transformer is designed to be 10 kHz - 20 MHz. Before use, it is necessary to measure and verify its frequency domain response at high frequencies to ensure that its sensitivity reaches -10 dB at about 10 MHz. The input end of the power frequency voltage transformer is connected to the distribution network cable terminal, and the output end of the power frequency voltage transformer is connected to the input end of the high-pass filter. The high-pass filter uses a Butterworth filter with a -3dB bandwidth of 5 kHz - 30 MHz and a -40dB rejection bandwidth of 2 kHz - 80 MHz. The output end of the high-pass filter is connected to the input end of the analog-to-digital converter. The analog-to-digital converter uses a two-channel AD9689 (Analog-to-Digital 9689), with a single-channel sampling rate of 2.6 GS / s and a sampling bit number of 14 bits. The output end of the analog-to-digital converter is connected to the microprocessor. The microprocessor uses an FPGA (Field-Programmable Gate Array) + ARM (Advanced RISC Machine) architecture. The FPGA is used to store the signal data collected by the analog-to-digital converter into the storage unit, and then the ARM filters, denoises, and digitally compensates the high-frequency signal data in the memory, and finally displays the original partial discharge signal through the display, and uploads it to the cloud database through the network unit to achieve real-time monitoring.

[0046] Embodiment 2 A method for detecting partial discharge signals based on a power frequency voltage transformer, comprising the following steps: Measure the frequency domain response of the power frequency voltage transformer and observe whether its sensitivity at 10 MHz reaches -10 dB. When the requirement is met, it means that the power frequency voltage transformer has the ability to measure partial discharge signals. Connect it to the distribution network cable terminal and carry out the measurement work; Use the power frequency voltage transformer to extract the actual voltage signal on the grid side of the distribution network cable terminal; Use a high-pass filter to filter out the low-frequency part of the actual voltage signal on the grid side and use a microprocessor for filtering and noise reduction processing to obtain the original partial discharge signal; Input the measured frequency domain response of the power frequency voltage transformer into the Vector Fitting Toolbox for fitting to obtain the transfer function ; Take its inverse transfer function in the z domain ; Use the inverse transfer function in the z domain to digitally compensate the original partial discharge signal, that is, multiply the inverse transfer function in the z domain by the z domain signal of the original partial discharge signal Multiply to obtain the z-domain signal of the compensated original partial discharge signal, perform inverse z-transform on it to convert it to the time domain, and obtain the compensated partial discharge signal; smooth the compensated partial discharge signal by the Empirical Mode Decomposition (EMD) method to obtain the final original partial discharge signal, and upload the final original partial discharge signal to the cloud database.

[0047] The method of the present invention does not require additional installation of a dedicated partial discharge sensor, saving the cost of sensor purchase and installation, and will not interfere with its original protection and measurement functions, nor will it have a negative impact on the normal operation of the cable network. It has the characteristics of being convenient, simple and efficient to use; the power frequency voltage transformer used has high sensitivity at high frequencies and has a high gain in the frequency range of 1 MHz and above, and can effectively detect rapidly changing partial discharge signals; digital compensation is a method of waveform reconstruction using the transfer function of the power frequency voltage transformer. Only by measuring the transfer function of the power frequency voltage transformer can partial discharge signals be obtained in different working environments, ensuring the accuracy and versatility of the measurement.

[0048] See Figure 3 , when this amplitude-frequency response curve graph is actually applied, there is no need to power off the distribution network, and only offline measurement of power frequency voltage transformers of the same specification is required; Figure 3 The amplitude-frequency response curve shown is obtained by the frequency sweep method, that is, by injecting sine signals of different frequencies from low frequency (5 kHz) to high frequency (20 MHz) into the primary side of the power frequency voltage mutual inductor using a function generator, recording the output waveform amplitude on the secondary side, and then calculating the actual transformation ratio; when this power frequency voltage transformer is used as a partial discharge sensor, it should be ensured that in the high frequency region, that is, the gain near 10 MHz should be as close as possible to -10 dB to ensure that its sensitivity performance meets the measurement requirements; Figure 4 The frequency domain spectrum of the partial discharge signal shown is a verification of the detection effect of the partial discharge signal of this power frequency voltage transformer. From Figure 4 it can be seen that the amplitude of the partial discharge signal is the highest in the range of 10 MHz - 20 MHz, and this frequency range exactly coincides with the high-sensitivity frequency range of the power frequency voltage transformer in Figure 3 , indicating that the power frequency voltage transformer has the ability to measure partial discharge signals. The waveform comparison graph obtained by injecting a sine signal using a partial discharge calibrator on the primary side of the power frequency voltage transformer and observing the output signal on the secondary side is the basis for judging whether the power frequency voltage transformer has the ability to measure partial discharge. See Figure 5 , the discharge amount of the injected signal is 100 pC, and it can be seen that the output signal is relatively clear, proving that this power frequency voltage transformer can be used as a partial discharge sensor.

[0049] Based on the same inventive concept, an embodiment of the present application provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method for detecting partial discharge signals of a power frequency voltage transformer. Among them, the memory may include internal memory, such as high-speed random access memory, and may also include non-volatile memory, such as at least one disk memory, etc.; the processor, network interface, and memory are interconnected through an internal bus, which can be an Industry Standard Architecture bus, a Peripheral Component Interconnect standard bus, an Extended Industry Standard Architecture bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the program may include program code, and the program code includes computer operation instructions. The memory may include internal memory and non-volatile memory and provide instructions and data to the processor.

[0050] Based on the same inventive concept, an embodiment of the present application provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the steps of the method for detecting partial discharge signals of the power frequency voltage transformer. Specifically, the computer-readable storage medium includes, but is not limited to, for example, volatile memory and / or non-volatile memory. The volatile memory may include RAM (Random Access Memory) and / or cache memory, etc. The non-volatile memory may include ROM (Read Only Memory), hard disk, flash memory, optical disc, magnetic disk, etc.

[0051] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM (Compact Disc Read-Only Memory), optical memory, etc.) containing computer-usable program code.

[0052] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and combinations of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device generate means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0053] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0054] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0055] Finally, it should be noted that the above-listed embodiments exist only as one or more specific manifestations of the technical solutions of the present invention. Their purpose is to clearly elaborate the concept, principle, and application method of the present invention through specific examples, rather than intending to limit the protection scope of the present invention to these specific embodiments. In fact, the true value of the present invention lies in the technical ideas and innovation points it proposes, rather than its manifestation form or implementation means.

[0056] For those of ordinary skill in the art, after thoroughly reading and understanding the technical solution of the present invention, they are fully capable of making various forms of changes, modifications, or equivalent replacements to the specific implementation manners of the invention based on their own professional knowledge and skills. These changes may include, but are not limited to: adjusting the value range of technical parameters, optimizing the algorithm process to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as the technical solutions after these changes still substantially maintain the technical features required to be protected by the original invention, that is, still can achieve the core functions and effects of the present invention, then these changes should be regarded as falling within the protection scope of the pending claims of the present invention.

[0057] In addition, with the continuous progress and development of technology, new technical means and methods are emerging continuously, which also provides a broad space for the further improvement and perfection of the present invention. Therefore, the protection scope of the present invention should also include those reasonably foreseeable improvements and expansions based on the existing technology. As long as these improvements and expansions do not depart from the basic principles and core concepts of the present invention, they should be regarded as equivalents of the present invention and are also protected by the patent right.

Claims

1. A method for detecting partial discharge signals based on power frequency voltage transformers, characterized in that, It includes the following steps: S1. Obtain the frequency-domain response of the original power-frequency voltage transformer of the distribution network by the frequency-sweeping method; S2. Collect the actual voltage signal on the grid side of the cable terminal of the distribution network through the power-frequency voltage transformer, preprocess the actual voltage signal on the grid side to obtain the original partial discharge signal, perform discrete-time Fourier transform on the original partial discharge signal to obtain the z-domain signal of the original partial discharge signal; S3. Fit the frequency-domain response to obtain the transfer function, and calculate the inverse transfer function in the z-domain according to the transfer function; S4. Perform digital compensation on the z-domain signal of the original partial discharge signal by using the inverse transfer function in the z-domain to obtain the z-domain signal of the compensated original partial discharge signal, and use the inverse z-transform to convert the z-domain signal of the compensated original partial discharge signal into the time domain to obtain the final original partial discharge signal.

2. The partial discharge signal detection method based on a power frequency voltage transformer according to claim 1, characterized in that The specific steps of step S1 include the following steps: Inject sinusoidal signals with different frequencies into the primary side of the original power-frequency voltage transformer of the distribution network, obtain the amplitude of the output waveform on the secondary side of the power-frequency voltage transformer, and calculate the frequency-domain response of the power-frequency voltage transformer based on the sinusoidal signals with different frequencies injected into the primary side and the amplitude of the output waveform on the secondary side; Step S1 further includes the following steps: Based on the frequency-domain response of the power-frequency voltage transformer, judge whether the sensitivity of the power-frequency voltage transformer meets the preset requirements. If it is judged to be yes, execute step S2; if it is judged to be no, replace the power-frequency voltage transformer with a sensitivity that meets the preset requirements.

3. A partial discharge signal detection method based on a power frequency voltage transformer according to claim 2, characterized in that The specific sinusoidal signals with different frequencies are: 5 kHz to 20 MHz; the specific preset requirements are: the sensitivity of the power-frequency voltage transformer is not less than -20 dB at 5 MHz to 20 MHz.

4. A method for detecting partial discharge signals based on a power frequency voltage transformer according to claim 1, characterized in that, The specific transfer function is: Among them, is the transfer function; is the number of real poles; and are the coefficients related to the th real pole; is the sampling period; is the first delay operator in the transformation, indicating that the sequence is delayed by one sampling period; and are the numerator coefficients related to the th complex pole; , , are the denominator coefficients related to the th complex pole; The specific inverse transfer function in the z-domain is: Among them, is the inverse transfer function in the z-domain; is the z-domain signal of the compensated original partial discharge signal; is the z-domain signal of the original partial discharge signal; , , and are the coefficients related to the th real pole in the z-domain; , and are the numerator coefficients related to the th complex pole in the z-domain; , and are the denominator coefficients related to the th complex pole in the z-domain; is the second delay operator in the z-transform, indicating that the sequence is delayed by two sampling periods.

5. A partial discharge signal detection method based on a power frequency voltage transformer according to claim 1, characterized in that, It further includes step S5: upload the final original partial discharge signal to the cloud database; In step S2, the preprocessing of the actual voltage signal on the grid side is specifically: filtering and noise reduction are sequentially performed on the actual voltage signal on the grid side.

6. A partial discharge signal detection method based on a power frequency voltage transformer according to claim 1, characterized in that, The specific process of using the inverse z-transform to convert the z-domain signal of the compensated original partial discharge signal into the time domain to obtain the final original partial discharge signal is: Use the inverse z-transform to convert the z-domain signal of the compensated original partial discharge signal into the time domain to obtain the compensated original partial discharge signal, and use the empirical mode decomposition method to smooth the compensated original partial discharge signal to obtain the final original partial discharge signal.

7. A partial discharge signal detection method based on a power frequency voltage transformer according to claim 1, characterized in that, The specific digital compensation is: Among them, is the z-domain signal of the original partial discharge signal after compensation; is the z-domain signal of the original partial discharge signal; is the inverse transfer function in the z-domain.

8. A partial discharge signal detection device based on a power frequency voltage transformer, characterized in that, Obtain the partial discharge signal by using the partial discharge signal detection method based on the power-frequency voltage transformer as described in any one of claims 1 to 7. The partial discharge signal detection device based on the power-frequency voltage transformer includes: A power-frequency voltage transformer, a high-pass filter, an analog-to-digital conversion unit, a microprocessor, a storage unit, a network unit and a display. Among them, a power-frequency voltage transformer is provided on the distribution network where the partial discharge signal to be measured is located. The output end of the power-frequency voltage transformer is connected to the input end of the high-pass filter, and the output end of the high-pass filter is connected to the microprocessor. The analog-to-digital conversion unit, the storage unit, the network unit and the display are respectively electrically connected to the microprocessor; A high-pass filter for extracting high-frequency analog signals of the actual voltage signal on the grid side; An analog-to-digital conversion unit for converting high-frequency analog signals into digital signals; A storage unit for storing the final original partial discharge signals; A network unit for uploading the final original partial discharge signals to the cloud database; A display for real-time display of the final original partial discharge signals.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the partial discharge signal detection method based on a power frequency voltage transformer according to any one of claims 1 to 7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the partial discharge signal detection method based on a power frequency voltage transformer according to any one of claims 1 to 7.

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