Crosslinked polyethylene cable operation safety early warning method
By compensating the spectrum of crosslinked polyethylene cables amplitude, the problem of low local discharge detection accuracy in the prior art is solved, and more accurate cable defect identification and operation safety warning are achieved, ensuring that the detection is comparable at different temperatures sex.
Patent Information
- Application Number
- CN202411678102.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2024-12-24
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The prior art is difficult to effectively realize safety warning of partial discharge operation of crosslinked polyethylene cables, and the local discharge detection accuracy is low, making it difficult to accurately identify cable defects.
By obtaining the initial spectrum map of the cable, intercepting the spectrum slices on both sides of the target frequency, calculating the amplitude standard deviation difference of the slices, performing amplitude compensation based on the difference value, generating the compensated target spectrum map to reduce background noise interference and improve detection accuracy .
More accurate detection of partial discharge of crosslinked polyethylene cables is achieved, background noise interference is reduced, operational safety warning is improved, and detection results are comparable at different temperatures.
Smart Images
Figure CN119178973A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of data processing technology, and in particular to a cross-linked polyethylene cable operation safety early warning method. Background Art
[0002] In the existing power transmission technology, in order to meet the needs of high-voltage and ultra-high-voltage power transmission, cross-linked polyethylene cables have become an important type of cable. The insulation layer of cross-linked polyethylene cables has high dielectric strength and low dielectric loss, can work stably under high-voltage environments, and effectively reduce power loss; cross-linked polyethylene materials have good heat resistance and can maintain insulation performance at higher temperatures.
[0003] During long-term operation, the insulation layer of the cross-linked polyethylene cable may have local defects due to manufacturing defects, material aging, and environmental stress, which may lead to partial discharge. Therefore, it is necessary to perform partial discharge detection on the cross-linked polyethylene cable.
[0004] In the related art, for example, in the Chinese patent application document with publication number CN110866340A, a partial discharge data processing method is provided, which is used to process the partial discharge data of the tested cable under the shock wave. The partial discharge data processing method includes: obtaining the partial discharge information of the tested cable under the shock wave; obtaining the partial discharge phase distribution spectrum and time-frequency spectrum of the tested cable based on the partial discharge information; analyzing the damage of the tested cable according to the partial discharge phase distribution spectrum; and analyzing the number and type of defects of the tested cable according to the time-frequency spectrum.
[0005] In the related art, partial discharge detection is performed through the overall spectrum, which results in low accuracy of partial discharge detection. Therefore, it is difficult to effectively implement early warning of the operation safety of partial discharge of cross-linked polyethylene cables. Summary of the invention
[0006] In order to overcome the problem that it is difficult to effectively realize the early warning of the operation safety of the partial discharge of the cross-linked polyethylene cable in the related art, the present application provides a method for early warning of the operation safety of the cross-linked polyethylene cable, comprising: obtaining an initial spectrum diagram for partial discharge detection of the cable to be tested, and intercepting adjacent first spectrum slices and second spectrum slices from both sides of the target frequency in the initial spectrum diagram; the difference between the amplitude of the first spectrum slice and the second spectrum slice and the amplitude of the target frequency is less than a preset amplitude threshold; the amplitude standard deviation of the first spectrum slice is used as the first fluctuation value, and the amplitude standard deviation of the second spectrum slice is used as the second fluctuation value to determine the difference between the first fluctuation value and the second fluctuation value; when the difference value is greater than the first preset difference threshold, determining a first compensation value for the amplitude of the target frequency ,in, is the normalization function, min is the minimum value, is the first fluctuation value, is the second fluctuation value, n is the number of frequencies in the first spectrum slice and the second spectrum slice, N is the number of frequencies in the initial spectrum image, and exp is an exponential function with a natural constant as the base; a second compensation value corresponding to the temperature of the cable under test during partial discharge detection is obtained, and the amplitude of the target frequency in the initial spectrum image is compensated according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image; the amplitudes corresponding to the same frequency in the target spectrum image and the preset spectrum image are compared to determine the frequencies whose amplitude differences are greater than a second preset difference threshold; a safety warning of partial discharge defects of the cable under test is performed according to the proportion of the number of frequencies whose amplitude differences are greater than the second preset difference threshold.
[0007] In this way, a second compensation value corresponding to the temperature when the cable to be tested is subjected to partial discharge detection is obtained, and the amplitude of the target frequency in the initial spectrum image is compensated according to the product of the first compensation value and the second compensation value, so as to obtain a compensated target spectrum image. Since the first compensation value is determined according to the characteristics of the first spectrum slice and the second spectrum slice located on both sides of the target frequency, and the difference between the amplitude of the first spectrum slice and the second spectrum slice and the amplitude of the target frequency is less than a preset amplitude threshold, the target spectrum image can more accurately reflect the details of the partial discharge signal and reduce the interference of background noise. A more accurate partial discharge detection result can be obtained through the target spectrum image, so as to better realize the operational safety warning of partial discharge of the cable to be tested.
[0008] Optionally, the second compensation value is determined in the following manner: obtaining a first temperature, an initial resistance and a resistance temperature coefficient of the cable to be tested before partial discharge detection; the resistance temperature coefficient is used to characterize the proportion of the resistance change of the cable to be tested with temperature; obtaining a second temperature of the cable to be tested when performing partial discharge detection, and determining a predicted resistance of the cable to be tested when performing partial discharge detection based on the first temperature, the second temperature, the initial resistance and the resistance temperature coefficient; obtaining the measured resistance of the cable to be tested when performing partial discharge detection, and determining the second compensation value based on the measured resistance, the predicted resistance and the initial resistance.
[0009] In this way, by obtaining the temperature of the cable to be tested before partial discharge detection and the temperature during partial discharge detection, the predicted resistance of the cable to be tested is determined, and the predicted resistance is compared with the actual resistance to determine the second compensation value corresponding to the temperature of the cable to be tested during partial discharge detection. The obtained second compensation value can make the frequency spectrum of the partial discharge signal consistent at different temperatures, so that the detection results at different temperatures have good comparability.
[0010] Optionally, determining the second compensation value according to the measured resistance, the predicted resistance and the initial resistance includes: , where C is the second compensation value, norm is the normalization function, To take the absolute value, To predict the resistance, is the measured resistance, log is the logarithmic function, is the initial resistance.
[0011] In this way, by comparing the predicted resistance with the measured resistance, and comparing the measured resistance during local discharge detection with the initial resistance before local discharge detection, the influence of resistance changes caused by temperature changes on the amplitude in the spectrum diagram of the local discharge signal can be avoided, so that the amplitude of the target frequency can be compensated more accurately through the determined second compensation value.
[0012] Optionally, the initial spectrum diagram of partial discharge detection of the cable to be tested is obtained by: performing partial discharge detection on the cable to be tested, and collecting partial discharge signals of the cable to be tested over a period of time using an electromagnetic sensor, etc.; filtering and amplifying the partial discharge signals, and performing Fourier transform on the amplified partial discharge signals to obtain the initial spectrum image.
[0013] Optionally, the first spectrum slice and the second spectrum slice are obtained in the following manner: taking the target frequency as the starting point, intercepting the spectrum slices from right to left, and when the ath frequency whose amplitude is intercepted and the difference between the amplitude of the target frequency and the amplitude of the target frequency is equal to the preset amplitude threshold, stopping the interception of the spectrum slices, and using the spectrum slices intercepted from right to left as the first spectrum slice; a is a preset number; taking the target frequency as the starting point, intercepting the spectrum slices from left to right, and when the ath frequency whose amplitude is intercepted and the difference between the amplitude of the target frequency and the amplitude of the target frequency is equal to the preset amplitude threshold, stopping the interception of the spectrum slices, and using the spectrum slices intercepted from left to right as the second spectrum slice.
[0014] In this way, since the selected first spectrum segment and the second spectrum segment are respectively located on both sides of the target frequency, and the difference between the amplitudes of the two spectrum segments and the amplitude of the target frequency is within a certain range, the spectrum diagram at the target frequency can be better analyzed to determine the partial discharge that may exist in the resistor to be tested.
[0015] Optionally, the amplitude of the target frequency in the initial spectrum image is compensated according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image, including: taking the product of the first compensation value and the second compensation value corresponding to the target frequency as the compensation amount for the amplitude of the target frequency; taking the sum of the amplitude of the target frequency before compensation and the compensation amount as the amplitude of the target frequency after compensation, so as to obtain the target spectrum image after compensating all target frequencies in the initial spectrum image.
[0016] Optionally, when the difference value is less than or equal to a first preset difference threshold, the first compensation value is determined in the following manner: , where A is the first compensation value, is the normalization function, is the amplitude of the target frequency in the initial spectrum, is the average value of the amplitude of all frequencies in the initial spectrum, is the maximum amplitude of all frequencies in the initial spectrum graph, n is the number of frequencies in the first spectrum slice and the second spectrum slice, N is the number of frequencies in the initial spectrum graph, To take the absolute value.
[0017] In this way, when the difference value is less than or equal to the first preset difference threshold, the amplitude of the target frequency in the initial spectrum graph, the average value of the amplitudes of all frequencies in the initial spectrum graph, and the maximum value of the amplitudes of all frequencies in the initial spectrum graph can be combined to achieve compensation for the amplitude of the target frequency, so as to more accurately realize partial discharge detection of the cable under test.
[0018] Optionally, based on the percentage of frequencies whose amplitude differences are greater than a second preset difference threshold, a safety warning of local discharge defects in the cable under test is performed, including: determining the percentage of frequencies whose amplitude differences are greater than a second preset difference threshold, and outputting safety warning information when the percentage is greater than a preset proportion threshold, wherein the safety warning information is used to indicate the presence of local discharge defects in the cable under test.
[0019] The technical solution provided by the embodiments of the present application may include the following beneficial effects: obtaining a second compensation value corresponding to the temperature when the cable to be tested is subjected to partial discharge detection, and compensating the amplitude of the target frequency in the initial spectrum image according to the product of the first compensation value and the second compensation value, to obtain a compensated target spectrum image; since the first compensation value is determined according to the characteristics of the first spectrum slice and the second spectrum slice located on both sides of the target frequency, and the difference between the amplitude of the first spectrum slice and the second spectrum slice and the amplitude of the target frequency is less than a preset amplitude threshold, the target spectrum image can more accurately reflect the details of the partial discharge signal and reduce the interference of background noise. A more accurate partial discharge detection result can be obtained through the target spectrum image, and an operational safety warning for partial discharge of the cable to be tested can be better realized.
[0020] At the same time, since the influence of temperature on the obtained spectrum diagram is taken into consideration, relatively accurate partial discharge detection of the cable under test can be achieved at different temperatures, so that the operation safety warning of the cable under test can be better achieved at different temperatures.
[0021] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.
[0023] Figure 1 The present invention is a flow chart showing a method for early warning of cross-linked polyethylene cable operation safety according to an exemplary embodiment. DETAILED DESCRIPTION
[0024] Here, exemplary embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application.
[0025] First, the application scenario of the embodiment of the present application is briefly introduced. In the application scenario of the present application, by performing local discharge detection on the cross-linked polyethylene cable, it can be determined whether the cross-linked polyethylene cable has local discharge. Since local discharge is a precursor to aging and failure of insulating materials, by performing local discharge detection on the cross-linked polyethylene cable, possible abnormalities of the cross-linked polyethylene cable can be discovered in advance.
[0026] In the related art, a partial discharge detector can be used to obtain a spectrum diagram of the cable under test during the partial discharge detection process, and determine whether the cable under test has a discharge detection based on the obtained spectrum diagram. However, the accuracy of the partial discharge detection result directly determined by the entire spectrum diagram is low. Therefore, it is difficult to effectively implement an early warning of the operation safety of the cross-linked polyethylene cable.
[0027] In view of the above technical problems, the present application provides a method for early warning of cross-linked polyethylene cable operation safety. Figure 1 FIG. 1 is a flow chart of a method for early warning of cross-linked polyethylene cable operation safety according to an exemplary embodiment. Figure 1 As shown, the method includes the following steps.
[0028] In step S101, an initial spectrum diagram for partial discharge detection of a cable to be tested is obtained, and adjacent first spectrum slices and second spectrum slices are intercepted from both sides of a target frequency in the initial spectrum diagram.
[0029] The initial spectrum diagram of the partial discharge detection of the cable under test can be obtained in the following way: perform partial discharge detection on the cable under test, and collect partial discharge signals of the cable under test over a period of time by using electromagnetic sensors, etc.; perform filtering and amplification processing on the partial discharge signals, and perform Fourier transformation on the amplified partial discharge signals to obtain an initial spectrum image.
[0030] The filtering process of the partial discharge signal can be realized by a filter, and the amplification process of the partial discharge signal can be realized by a signal amplifier.
[0031] Fourier transform is a transformation tool used in mathematics, engineering and physics. Through Fourier transform, the signal in the time domain (or space domain) can be decomposed into a combination of multiple sine waves and cosine waves in the frequency domain, thereby obtaining a spectrum diagram representing the frequency domain signal.
[0032] The difference between the amplitude of the first spectrum slice and the second spectrum slice and the amplitude of the target frequency is less than a preset amplitude threshold, so that the performance of the spectrum graph at the target frequency can be determined based on the first spectrum slice and the second spectrum slice; the target frequency can be any frequency among all the frequencies of the initial spectrum graph.
[0033] In one embodiment, the first spectrum slice and the second spectrum slice are obtained in the following manner: taking the target frequency as the starting point, the spectrum slices are intercepted from right to left, and when the ath frequency whose amplitude is intercepted and the difference between the amplitude of the target frequency and the amplitude of the target frequency is equal to the preset amplitude threshold, the spectrum slices are stopped from being intercepted, and the spectrum slices intercepted from right to left are used as the first spectrum slice; a is a preset number; taking the target frequency as the starting point, the spectrum slices are intercepted from left to right, and when the ath frequency whose amplitude is intercepted and the difference between the amplitude of the target frequency and the amplitude of the target frequency is equal to the preset amplitude threshold, the spectrum slices are stopped from being intercepted, and the spectrum slices intercepted from left to right are used as the second spectrum slice.
[0034] For example, the preset number can be set to 1, so that when the difference between the first amplitude and the target frequency is equal to the preset amplitude threshold, the interception of spectrum slices is stopped; by stopping the interception of spectrum slices when the difference between the amplitude and the target frequency is equal to the ath frequency of the preset amplitude threshold, it can be ensured that the difference between the amplitude in the intercepted first spectrum slice and the amplitude of the target frequency is within a certain range, and it can be ensured that the difference between the amplitude in the intercepted second spectrum slice and the amplitude of the target frequency is within a certain range.
[0035] Since the selected first spectrum fragment and the second spectrum fragment are respectively located on both sides of the target frequency, and the difference between the amplitudes of the two spectrum fragments and the amplitude of the target frequency is within a certain range, the spectrum diagram at the target frequency can be better analyzed to determine the partial discharge that may exist in the resistor to be tested.
[0036] The preset amplitude threshold may be determined according to the amplitude of the target frequency. For example, the preset amplitude threshold may be between 10% and 20% of the amplitude of the target frequency.
[0037] In step S102, the amplitude standard deviation of the first spectrum slice is used as the first fluctuation value, and the amplitude standard deviation of the second spectrum slice is used as the second fluctuation value to determine the difference between the first fluctuation value and the second fluctuation value.
[0038] The amplitude standard deviation of the first spectrum slice can characterize the degree of change of the amplitude of the signal in the frequency band corresponding to the first spectrum slice, and the amplitude standard deviation of the second spectrum slice can characterize the degree of change of the amplitude of the signal in the frequency band corresponding to the second spectrum slice. Therefore, by determining the difference between the first fluctuation value and the second fluctuation value, the difference in signal changes in the two frequency bands can be quantified.
[0039] When the cable under test has a local discharge defect, there may be abnormal amplitude fluctuations in the local area of the spectrum graph, resulting in differences in the degree of amplitude fluctuation in different frequency bands. By determining the difference between the first fluctuation value and the second fluctuation value, it can be determined whether the spectrum graph has an abnormality at the target frequency; the difference between the first fluctuation value and the second fluctuation value can be equal to the absolute value of the difference between the first fluctuation value and the second fluctuation value.
[0040] When there is no local discharge defect in the cable under test, the fluctuation degree of the amplitude of the frequency in the spectrum diagram obtained by the local discharge detection of the cable under test is small, for example, the number of sudden amplitude changes is small or there is no sudden amplitude change; the spectrum performance on both sides of the target frequency has a certain consistency, so that when there is no local discharge defect in the cable under test, the fluctuation values of the spectrum segments on both sides of the target frequency have a certain consistency. Therefore, obtaining the difference between the first fluctuation value and the second fluctuation value can facilitate the analysis of the performance of the spectrum diagram at the target frequency.
[0041] In step S103 , when the difference value is greater than a first preset difference threshold, a first compensation value for the amplitude of the target frequency is determined.
[0042] When the difference value is greater than the first preset difference threshold, it indicates that the frequency spectrum slices on both sides of the target frequency have a high degree of difference in amplitude fluctuation, and the partial discharge signal has a high probability of being attenuated at the target frequency.
[0043] The first preset difference threshold can be set according to actual needs, for example, it can be determined according to the difference values corresponding to multiple spectrum slice groups, the spectrum slice group includes a first spectrum slice and a second spectrum slice respectively located on both sides of the target frequency, and different spectrum slice groups correspond to different target frequencies.
[0044] When the difference value is greater than the first preset difference threshold, the first compensation value of the amplitude of the target frequency is determined in the following manner: ,in, is the normalization function, min is the minimum value, is the first fluctuation value, is the second fluctuation value, n is the number of frequencies in the first spectrum slice and the second spectrum slice, N is the number of frequencies in the initial spectrum graph, and exp is an exponential function with a natural constant as the base.
[0045] The calculation result is normalized using the norm function, which is used to normalize the calculation result to a value within the range of 0 to 1, so as to facilitate comparison and analysis between different parameter values. The first compensation value comprehensively considers the first fluctuation value and the second fluctuation value, which helps to compensate for the amplitude of the target frequency according to the spectrum slices on both sides of the target frequency. Compared with the corresponding compensation through the amplitude of the target frequency itself, it can achieve more refined compensation for the amplitude of the target frequency and improve the compensation effect of the amplitude of the target frequency.
[0046] When compensating the amplitude of the target frequency, the minimum value of the first fluctuation value and the second fluctuation value is selected by the min function, and the minimum value is used to determine the first compensation value, so that the amplitude of the target frequency can be compensated. Moreover, since the minimum of the first fluctuation value and the second fluctuation value is selected, excessive compensation of the amplitude of the target frequency due to abnormalities in other frequencies on one side of the target frequency can be avoided, thereby achieving more accurate compensation of the amplitude of the target frequency.
[0047] Since n is the number of frequencies in the first spectrum slice and the second spectrum slice, and N is the number of frequencies in the initial spectrum graph, n / N can characterize the proportional relationship between the total frequency span of the first spectrum slice and the second spectrum slice and the total frequency span of the spectrum graph, and since the difference between the amplitudes of the first spectrum slice and the second spectrum slice and the target frequency is within a certain range, n / N can characterize the representativeness of the target frequency in the spectrum image.
[0048] Since the difference between the first fluctuation value and the second fluctuation value can characterize the difference in amplitude fluctuation between the first spectrum slice and the second spectrum slice, the difference between the first fluctuation value and the second fluctuation value can characterize the probability of attenuation of the amplitude of the target frequency.
[0049] In the calculation formula of the first compensation value of the target frequency, the greater the difference between the first fluctuation value and the second fluctuation value, the greater the first compensation value for the amplitude of the target frequency; on the contrary, the smaller the difference between the first fluctuation value and the second fluctuation value, the smaller the first compensation value for the amplitude of the target frequency. Therefore, a higher degree of compensation can be made for the amplitude of the frequency with a higher probability of amplitude attenuation.
[0050] When the difference value is less than or equal to the first preset difference threshold, the first compensation value is determined in the following manner: , where A is the first compensation value, is the normalization function, is the amplitude of the target frequency in the initial spectrum, is the average value of the amplitude of all frequencies in the initial spectrum, is the maximum amplitude of all frequencies in the initial spectrum graph, n is the number of frequencies in the first spectrum slice and the second spectrum slice, N is the number of frequencies in the initial spectrum graph, To take the absolute value.
[0051] When the difference value is less than or equal to the first preset difference threshold, it means that the spectrum slices on both sides of the target frequency are relatively close in amplitude fluctuation, and the probability of anomalies in the target frequency in adjacent frequency bands is low. It may be difficult to accurately compensate for the amplitude of the target frequency only by using the spectrum slices on both sides of the target frequency. Therefore, it is possible to consider utilizing the characteristics of the entire spectrum graph and the actual situation of the amplitude of the target frequency to compensate for the amplitude of the target frequency.
[0052] By calculating the difference between the amplitude of the target frequency and the average amplitude and comparing it with the maximum amplitude, the relative importance of the target frequency in the overall spectrum can be more accurately reflected; using the normalization function norm, it can be ensured that the first compensation value is between 0 and 1, which is convenient for comparison and analysis between different spectrum graphs.
[0053] When the difference value is less than or equal to the first preset difference threshold, it indicates that the amplitude of the target frequency is relatively close to the characteristics of the overall spectrum. At this time, applying the compensation value can avoid over-adjustment and maintain the original characteristics of the signal.
[0054] By introducing the maximum value of the amplitude of all frequencies as the denominator, the impact of possible outliers in the spectrum graph on the first compensation value can be reduced, thereby improving the robustness of the algorithm to noise and abnormal data; through the ratio of the number of frequencies n in the spectrum slice to the total number of frequencies N, the calculation process of the first compensation value takes into account the specific situation of the spectrum slice, so that the compensation strategy can adapt to the characteristics of different spectrum graphs, and regardless of whether the spectrum in the spectrum graph is a dense spectrum or a sparse spectrum, a good compensation effect can be achieved.
[0055] In this way, when the difference value is less than or equal to the first preset difference threshold, the amplitude of the target frequency in the initial spectrum graph, the average value of the amplitudes of all frequencies in the initial spectrum graph, and the maximum value of the amplitudes of all frequencies in the initial spectrum graph can be combined to achieve compensation for the amplitude of the target frequency, so as to more accurately realize partial discharge detection of the cable under test.
[0056] In step S104, a second compensation value corresponding to the temperature of the cable under test during partial discharge detection is obtained, and the amplitude of the target frequency in the initial spectrum image is compensated according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image.
[0057] The increase in resistance will cause the signal generated by partial discharge to attenuate more seriously during the transmission process. During the transmission of the partial discharge signal, the resistance of the conductive part of the cable will convert part of the signal energy into heat energy, thereby reducing the amplitude of the collected partial discharge signal. Therefore, the resistance of the conductive part of the cable will affect the amplitude of the partial discharge signal.
[0058] The resistance of the conductive part of the cable will be affected by temperature. Therefore, the resistance of the cable is different when working at different temperatures, which makes the conductive part of the cable have different degrees of influence on the partial discharge signal when working at different temperatures. Therefore, the amplitude of the partial discharge signal during partial discharge detection can be compensated in combination with the temperature of the cable under test during partial discharge detection.
[0059] In one embodiment, the second compensation value is determined in the following manner: obtaining a first temperature, an initial resistance and a resistance temperature coefficient of the cable to be tested before partial discharge detection; the resistance temperature coefficient is used to characterize the ratio of the resistance change of the cable to be tested with temperature; obtaining a second temperature of the cable to be tested when performing partial discharge detection, and determining a predicted resistance of the cable to be tested when performing partial discharge detection based on the first temperature, the second temperature, the initial resistance and the resistance temperature coefficient; obtaining the measured resistance of the cable to be tested when performing partial discharge detection, and determining the second compensation value based on the measured resistance, the predicted resistance and the initial resistance.
[0060] Since the temperature coefficient of resistance is used to characterize the ratio of the resistance change of the cable to be tested with temperature, therefore, based on the pre-collected temperature of the cable to be tested before the partial discharge detection, for example, the temperature of the cable to be tested when the equipment where the cable to be tested is located is in a shutdown state, and the temperature of the cable to be tested during the partial discharge detection, combined with the pre-acquired temperature coefficient of resistance of the cable to be tested, the resistance change of the conductive part of the cable to be tested before and after the partial discharge detection can be determined.
[0061] For example, the predicted resistance of a cable under test during partial discharge testing can be determined as follows: , To predict the resistance, is the initial resistance; is the resistance temperature coefficient of the conductive part of the cable to be tested, which can be obtained by testing the conductive part of the cable to be tested in advance; is the second temperature of the cable to be tested during partial discharge detection, It is the first temperature of the cable to be tested before partial discharge detection.
[0062] When determining the predicted resistance of the cable under test during partial discharge detection, since the resistance of the conductive part of the cable under test may not be completely linear with the temperature, there may be a certain difference between the determined predicted resistance and the actual resistance of the cable under test during partial discharge detection. By comparing the measured resistance and the predicted resistance, possible deviations in the actual measurement can be identified.
[0063] In this way, by obtaining the temperature of the cable to be tested before partial discharge detection and the temperature during partial discharge detection, the predicted resistance of the cable to be tested is determined, and the predicted resistance is compared with the actual resistance to determine the second compensation value corresponding to the temperature of the cable to be tested during partial discharge detection. The obtained second compensation value can make the frequency spectrum of the partial discharge signal consistent at different temperatures, so that the detection results at different temperatures have good comparability.
[0064] In one embodiment, determining the second compensation value according to the measured resistance, the predicted resistance and the initial resistance includes: , where C is the second compensation value, norm is the normalization function, To take the absolute value, To predict the resistance, is the measured resistance, log is the logarithmic function, is the initial resistance.
[0065] The normalization processing function norm ensures that the second compensation value is in the range of 0 to 1, which is convenient for comparing and analyzing the second compensation values under different conditions; through the absolute value of the difference between the predicted resistance and the measured resistance, the predicted resistance and the measured resistance can be compared. The greater the difference between the predicted resistance and the measured resistance, the greater the probability of attenuation of the partial discharge signal, and the greater the determined second compensation value, thereby correspondingly increasing the compensation amount for the amplitude of the target frequency.
[0066] As the temperature rises, the resistance of the cable under test increases, and the degree of attenuation caused to the partial discharge signal increases. In order to make the acquired partial discharge signal have better consistency, the measured resistance can be compared with the initial resistance; the larger the ratio of the measured resistance to the initial resistance, the greater the attenuation caused to the partial discharge signal, and a larger second compensation value can be used to compensate the amplitude in the spectrum diagram of the partial discharge signal.
[0067] In this way, by comparing the predicted resistance with the measured resistance, and comparing the measured resistance during local discharge detection with the initial resistance before local discharge detection, the influence of resistance changes caused by temperature changes on the amplitude in the spectrum diagram of the local discharge signal can be avoided, so that the amplitude compensation of the target frequency can be more accurately achieved through the determined second compensation value.
[0068] In one embodiment, the amplitude of the target frequency in the initial spectrum image is compensated according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image, including: taking the product of the first compensation value and the second compensation value corresponding to the target frequency as the compensation amount for the amplitude of the target frequency; taking the sum of the amplitude of the target frequency before compensation and the compensation amount as the amplitude of the target frequency after compensation, so as to obtain the target spectrum image after compensating all target frequencies in the initial spectrum image.
[0069] By using the product of the first compensation value and the second compensation value corresponding to the target frequency as the compensation amount for the amplitude of the target frequency, the anomalies existing in the spectrum slices on both sides of the target frequency and the attenuation of the amplitude of the target frequency caused by temperature can be combined, thereby better realizing the compensation for the amplitude of the target frequency; by compensating the amplitudes of multiple target frequencies in the spectrum graph separately, the amplitude of the entire initial spectrum graph can be compensated.
[0070] In this way, since the first compensation value is determined based on the spectrum slices on both sides of the target frequency, and the second compensation value is determined based on the temperature during local discharge detection, the first compensation value and the second compensation value are combined to compensate for the amplitude in the initial spectrum diagram, which can better achieve amplitude compensation for the initial spectrum diagram, so as to determine whether there is local discharge in the cable under test.
[0071] In step S105, the target spectrum image and the preset spectrum image are compared, and a safety warning is issued when it is determined according to the comparison result that partial discharge exists in the cable to be tested.
[0072] The amplitudes corresponding to the same frequency in the target spectrum image and the preset spectrum image can be compared to determine the frequencies whose amplitude differences are greater than a second preset difference threshold; based on the proportion of the frequencies whose amplitude differences are greater than the second preset difference threshold, a safety warning of partial discharge defects in the cable to be tested is issued.
[0073] The second preset difference threshold can be set according to actual needs. For example, the second preset difference threshold can be between 10% and 20% of the amplitude of the target frequency. The embodiment of the present application does not limit the specific value of the second preset difference threshold.
[0074] The preset spectrum image is obtained when performing partial discharge detection on a reference cable. The reference cable is another cable made of the same material as the cable to be tested and does not have partial discharge defects. The preset spectrum image can represent the spectrum information when there is no partial discharge defect. By comparing the target spectrum image with the preset spectrum image, it can be better determined whether there is an abnormality in the target spectrum image, so as to determine whether there is a partial discharge defect in the cable to be tested.
[0075] The target spectrum image is obtained after compensating the initial spectrum image, and the compensation for the amplitude of the target frequency in the initial spectrum image is performed based on the spectrum slices on both sides of the target frequency, so that the compensation amount for the target frequency with abnormalities is larger, and the difference in amplitude between the target frequency with abnormalities and the preset spectrum image is larger. Therefore, by comparing the amplitudes corresponding to the same frequency in the two spectrum images, the frequency with abnormalities can be determined, so as to determine whether there is a local discharge defect in the cable to be tested.
[0076] Since the amplitude of the frequency in the spectrum graph has a certain allowable fluctuation, determining the number of frequencies whose amplitude difference is greater than the second preset difference threshold can avoid misjudging the frequencies whose amplitude fluctuation is within the allowable fluctuation as abnormal frequencies. When the number ratio is greater than the preset ratio threshold, it means that the proportion of abnormal frequencies is greater than the allowed ratio, and it can be determined that partial discharge exists in the cable to be tested. The preset ratio threshold can be between 10% and 15%, and the corresponding preset ratio threshold can be set according to actual needs.
[0077] In one embodiment, a safety warning of a partial discharge defect in the cable under test is performed based on the proportion of frequencies whose amplitude differences are greater than a second preset difference threshold, including: determining the proportion of frequencies whose amplitude differences are greater than the second preset difference threshold, and outputting a safety warning message when the proportion is greater than a preset proportion threshold, wherein the safety warning message is used to indicate the presence of a partial discharge defect in the cable under test.
[0078] For example, the cross-linked polyethylene cable operation safety warning method can be executed by a monitoring device. When the quantity ratio is greater than a preset ratio threshold, it can be determined that the cable under test has a local discharge defect, and the monitoring device can output at least one of the warning information such as audio warning information, light warning information, and text warning information; or, the monitoring device can send a prompt message to the terminal device bound to the user, so that the device outputs at least one of the warning information such as audio warning information, light warning information, and text warning information.
[0079] In this way, when the number ratio is greater than the preset ratio threshold, a safety warning information is output to indicate that the cable under test has a partial discharge defect, which can effectively realize an operation safety warning for the cable under test.
[0080] Through the cross-linked polyethylene cable operation safety warning method provided in the embodiment of the present application, a second compensation value corresponding to the temperature of the cable to be tested during local discharge detection is obtained, and the amplitude of the target frequency in the initial spectrum image is compensated according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image. Since the first compensation value is determined based on the characteristics of the first spectrum slice and the second spectrum slice located on both sides of the target frequency, and the difference between the amplitude of the first spectrum slice and the second spectrum slice and the amplitude of the target frequency is less than a preset amplitude threshold, the target spectrum image can more accurately reflect the details of the local discharge signal and reduce the interference of background noise. A more accurate local discharge detection result can be obtained through the target spectrum image, and the operation safety warning of the local discharge of the cable to be tested can be better realized.
[0081] It should be understood that the features of some embodiments of the various applications described herein may be combined with each other, unless specifically stated otherwise.
[0082] Although terms such as "first", "second", and "third" may be used herein to describe various components, parts, regions, layers, or sections, these components, parts, regions, layers, or sections are not limited to these terms. Instead, these terms are only used to distinguish one component, part, region, layer, or section from another component, part, region, layer, or section. Therefore, without departing from the teachings of the examples described herein, the first component, part, region, layer, or section mentioned in the examples may also be referred to as the second component, part, region, layer, or section.
[0083] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description herein, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
[0084] In addition, the word "exemplary" is used herein to mean serving as an example, instance, or diagram. Any aspect or design described herein as "exemplary" is not necessarily to be understood as being advantageous over other aspects or designs. Instead, the use of the word exemplary is intended to present concepts in a concrete manner. As used herein, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or".
[0085] Likewise, although the present application has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. With particular regard to the various functions performed by the components (e.g., elements, resources, etc.) described above, unless otherwise noted, the terms used to describe such components are intended to correspond to any component (functionally equivalent) that performs the specific functions of the described components, even if not structurally equivalent to the disclosed structures.
[0086] Additionally, while particular features of the present application may have been disclosed with respect to only one of several implementations, such features may be combined with one or more other features of other implementations as may be desired and advantageous for any given or particular application.
[0087] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application, and the specification and embodiments are only considered as exemplary.
[0088] It will be appreciated that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.
Claims
1. A cross-linked polyethylene cable operation safety early warning method, characterized in that: include: Acquire an initial spectrum diagram for partial discharge detection of the cable to be tested, and intercept adjacent first spectrum slices and second spectrum slices from both sides of the target frequency in the initial spectrum diagram; The target frequency is any one of all the frequencies of the initial spectrum graph; the difference between the amplitude of the first spectrum slice and the second spectrum slice and the amplitude of the target frequency is less than a preset amplitude threshold; Taking the amplitude standard deviation of the first spectrum slice as the first fluctuation value, and taking the amplitude standard deviation of the second spectrum slice as the second fluctuation value, to determine the difference between the first fluctuation value and the second fluctuation value; When the difference value is greater than a first preset difference threshold, a first compensation value for the amplitude of the target frequency is determined. ,in, is the normalization function, min is the minimum value, is the first fluctuation value, is the second fluctuation value, n is the number of frequencies in the first spectrum slice and the second spectrum slice, N is the number of frequencies in the initial spectrum graph, and exp is an exponential function with a natural constant as the base; Obtaining a second compensation value corresponding to the temperature of the cable to be tested during partial discharge detection, and compensating the amplitude of the target frequency in the initial spectrum image according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image; The amplitudes corresponding to the same frequency in the target spectrum image and the preset spectrum image are compared to determine the frequencies whose amplitude differences are greater than a second preset difference threshold; based on the proportion of the frequencies whose amplitude differences are greater than the second preset difference threshold, a safety warning of partial discharge defects in the cable to be tested is issued.
2. The cross-linked polyethylene cable operation safety early warning method according to claim 1, characterized in that: The second compensation value is determined in the following manner: Obtaining a first temperature, an initial resistance, and a resistance temperature coefficient of the cable to be tested before partial discharge detection; the resistance temperature coefficient is used to characterize the ratio of the resistance change of the cable to be tested with temperature; Acquire a second temperature of the cable under test when performing partial discharge detection, and determine a predicted resistance of the cable under test when performing partial discharge detection according to the first temperature, the second temperature, the initial resistance, and the resistance temperature coefficient; The measured resistance of the cable to be tested during partial discharge detection is obtained, and the second compensation value is determined according to the measured resistance, the predicted resistance and the initial resistance.
3. The cross-linked polyethylene cable operation safety early warning method according to claim 2, characterized in that: Determining the second compensation value according to the measured resistance, the predicted resistance and the initial resistance includes: , where C is the second compensation value, norm is the normalization function, To take the absolute value, To predict the resistance, is the measured resistance, log is the logarithmic function, is the initial resistance.
4. The cross-linked polyethylene cable operation safety early warning method according to claim 1, characterized in that: The initial spectrum of the partial discharge test on the cable under test is obtained by: Detect partial discharge of the cable under test and collect partial discharge signals of the cable under test within a period of time using electromagnetic sensors; The local discharge signal is filtered and amplified, and the amplified local discharge signal is Fourier transformed to obtain the initial spectrum image.
5. The cross-linked polyethylene cable operation safety early warning method according to claim 1, characterized in that: The first spectrum slice and the second spectrum slice are obtained in the following manner: Taking the target frequency as the starting point, spectrum slices are intercepted from right to left. When the intercepted frequency has an amplitude difference equal to the preset amplitude threshold of the target frequency, the spectrum slice interception is stopped, and the spectrum slice intercepted from right to left is taken as the first spectrum slice; a is a preset number; Spectrum slices are intercepted from left to right starting from the target frequency. When the difference between the intercepted amplitude and the amplitude of the target frequency is equal to the ath frequency of the preset amplitude threshold, the spectrum slice interception is stopped and the spectrum slice intercepted from left to right is used as the second spectrum slice.
6. The cross-linked polyethylene cable operation safety early warning method according to claim 1, characterized in that: Compensating the amplitude of the target frequency in the initial spectrum image according to the product of the first compensation value and the second compensation value to obtain a compensated target spectrum image, including: The product of the first compensation value and the second compensation value corresponding to the target frequency is used as the compensation amount for the amplitude of the target frequency; The sum of the amplitude of the target frequency before compensation and the compensation amount is used as the amplitude of the target frequency after compensation, so as to obtain a target spectrum image after all target frequencies in the initial spectrum image are compensated.
7. The cross-linked polyethylene cable operation safety early warning method according to claim 1, characterized in that: When the difference value is less than or equal to the first preset difference threshold, the first compensation value is determined in the following manner: , where A is the first compensation value, is the normalization function, is the amplitude of the target frequency in the initial spectrum, is the average value of the amplitude of all frequencies in the initial spectrum, is the maximum amplitude of all frequencies in the initial spectrum graph, n is the number of frequencies in the first spectrum slice and the second spectrum slice, N is the number of frequencies in the initial spectrum graph, To take the absolute value.
8. The cross-linked polyethylene cable operation safety early warning method according to claim 1, characterized in that: According to the proportion of the number of frequencies whose amplitude differences are greater than the second preset difference threshold, a safety early warning of partial discharge defects of the cable to be tested is performed, including: Determine the proportion of frequencies whose amplitude differences are greater than a second preset difference threshold, and output safety warning information when the proportion is greater than a preset ratio threshold, wherein the safety warning information is used to indicate that a partial discharge defect exists in the cable to be tested.