An environment-friendly overhead insulated conductor crosslinking process temperature field regulation method

Abstract

This invention belongs to the field of wire and cable manufacturing technology, specifically relating to an environmentally friendly method for temperature field control in the cross-linking process of overhead insulated conductors. The method includes: acquiring surface temperature field data of the insulated conductor and converting it into a spatial frequency domain signal; obtaining a first compensation level for each spatial frequency based on the amplitude differences, fluctuation dispersion, and symmetry of its neighboring frequency domain components; obtaining a second compensation level based on real-time temperature values ​​and measured resistance values, combined with initial values ​​and the conductor resistance temperature coefficient; aligning and fusing the second compensation level sequence with the first compensation level sequence to obtain the total compensation level, correcting the amplitude value of the spatial frequency domain signal, thereby identifying abnormal temperature fluctuation regions and outputting adjustment signals to the heating power controller to perform temperature field control. This invention achieves full-dimensional adaptive compensation of the temperature field in the cross-linking process, improving the consistency and stability of cross-linking quality, reducing energy consumption and scrap rate, and exhibiting significant environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of wire and cable manufacturing technology. More specifically, this invention relates to an environmentally friendly method for temperature field control in the cross-linking process of overhead insulated conductors, applicable to the production and manufacturing process of cross-linked polyethylene insulated power cables and cable accessories. Background Technology

[0002] Cross-linked polyethylene (XLPE) is widely used as the insulation material for overhead insulated conductors due to its excellent insulation properties, heat resistance, and corrosion resistance. In the production process of environmentally friendly overhead insulated conductors, the cross-linking process is a crucial step that determines the performance of the insulation layer. This process uses physical or chemical methods to form a three-dimensional network structure of polyethylene molecules, thereby significantly improving the conductor's heat resistance, mechanical strength, and aging resistance.

[0003] In the cross-linking process, heating methods such as hot air heating, infrared heating, or steam heating are typically used to bring the insulation layer to and maintain it within the temperature range required for the cross-linking reaction. The uniformity and stability of the temperature field directly determine the degree and consistency of the cross-linking reaction. If the temperature distribution is uneven or deviates from the set value, it will lead to insufficient or excessive cross-linking in some areas of the insulation layer, which in turn will cause quality problems such as decreased insulation performance, inconsistent mechanical strength, and susceptibility to cracking. In severe cases, it may even cause the conductor to break down during subsequent operation.

[0004] In existing technologies, temperature control for the cross-linking process of overhead insulated conductors often employs fixed-point temperature monitoring based on thermocouples or resistance temperature detectors (RTDs), combined with closed-loop regulation of heating power using a PID controller. However, in actual production, factors such as continuous conductor traction through the heating channel, differences in heat capacity between conductors of different specifications, power fluctuations in the heating equipment itself, and changes in environmental heat dissipation conditions can result in a complex, non-uniform temperature field distribution along both the axial and radial directions of the conductor. Fixed-point monitoring cannot fully reflect the true state of the entire temperature field, and traditional uniform temperature correction methods cannot provide precise correction for temperature fluctuations at different locations and frequencies, leading to lag and insufficient accuracy in temperature control, thus affecting the stability of cross-linking quality.

[0005] Therefore, there is an urgent need for a method that can accurately identify and dynamically control the complex temperature field in the cross-linking process of overhead insulated conductors, so as to improve the consistency of cross-linking quality, reduce the scrap rate, and achieve the environmental protection goals of energy saving and consumption reduction. Summary of the Invention

[0006] To address the technical problems of insufficient precision in traditional temperature field control and the inability to perform fine-grained correction for fluctuations at different spatial frequencies, this invention provides solutions in the following aspects.

[0007] In a first aspect, the present invention provides an environmentally friendly method for temperature field control in the crosslinking process of overhead insulated conductors, comprising: acquiring temperature field data of the surface of the insulated conductor in the crosslinking process and preprocessing it; converting the spatial domain temperature acquisition signal into a spatial frequency domain signal after denoising; for each spatial frequency in the spatial frequency domain signal, obtaining a first compensation degree characterizing its temperature fluctuation compensation requirement based on the amplitude difference, fluctuation dispersion degree and left and right neighbor symmetry of its frequency components, thus forming a first compensation degree sequence; based on the real-time temperature value and measured resistance value at each moment during the heating process of the insulated conductor, combined with the initial temperature value, initial resistance value and conductor resistance temperature coefficient before heating, comparing the difference between the theoretical resistance value and the measured resistance value and combining the relative change rate of resistance, obtaining a second compensation degree characterizing the signal attenuation compensation requirement, thus forming a second compensation degree sequence; aligning and fusing the second compensation degree sequence with the first compensation degree sequence in the spatial dimension to obtain the total compensation degree of each spatial frequency at each spatial location; using the total compensation degree to correct the amplitude value of the spatial frequency domain signal; identifying abnormal temperature fluctuation regions based on the relative difference of the amplitude values ​​before and after correction; and outputting an adjustment signal to the heating power controller to perform temperature field control.

[0008] This method acquires the surface temperature field of the insulated conductor and transforms it into a spatial frequency domain signal. A first compensation level is obtained based on the frequency domain fluctuation characteristics, and a second compensation level is obtained based on the real-time resistance-temperature relationship. These two levels are then fused to correct the frequency domain signal amplitude, thereby identifying abnormal fluctuation regions and adjusting the heating power. This method achieves full-dimensional adaptive compensation of the temperature field in the crosslinking process, from spatial frequency to resistance attenuation, significantly improving the accuracy and response speed of temperature control, ensuring the uniformity of crosslinking quality, and reducing energy consumption.

[0009] Preferably, the step of acquiring and preprocessing the temperature field data of the insulated wire surface during the cross-linking process includes: installing non-contact infrared temperature sensors at equal intervals along the direction of travel of the insulated wire in the heating section of the cross-linking furnace to form a temperature sensor array, continuously acquiring temperature data of the insulated wire surface; amplifying the analog voltage signal output by the infrared temperature sensors to the input range of the analog-to-digital converter, then converting it into an original temperature digital sequence by the analog-to-digital converter, and obtaining the spatial frequency domain signal by Fourier transform after denoising the original temperature digital sequence.

[0010] Preferably, the original temperature digital sequence is denoised using a median filtering algorithm. A neighborhood with an odd window length is selected centered on the current sampling point. All temperature values ​​in the neighborhood are sorted by size, and the median is taken as the filtered output value of the sampling point. The denoised temperature signal sequence is obtained by traversing all sampling points. Then, a short-time Fourier transform is performed on the denoised temperature signal sequence to obtain the Fourier coefficients corresponding to each spatial frequency. The amplitude value represents the relative intensity of temperature fluctuation at the corresponding spatial frequency.

[0011] Preferably, obtaining the first compensation level includes: determining the associated frequency set for each spatial frequency. The method for determining the associated frequency set is as follows: traversing the amplitude difference of all adjacent frequency components in the amplitude sequence of the spatial frequency domain signal and taking the minimum value as the minimum amplitude difference; taking the amplitude value of the current spatial frequency as a reference, traversing to its left and right sides successively until the first frequency component whose difference from the reference amplitude value is greater than the sum of the minimum amplitude difference and the preset tolerance is encountered. The traversed frequency components constitute the left neighbor and the right neighbor, respectively. The left neighbor, the right neighbor, and the current spatial frequency itself together constitute the associated frequency set.

[0012] This invention uses the minimum amplitude difference between adjacent frequency components as a scale, and dynamically searches to the left and right with the amplitude of the current frequency as a reference until the sum of the scale and the tolerance is exceeded. The frequency components within the search range are then grouped into a set of associated frequencies. This method adaptively determines the effective neighborhood of each spatial frequency, avoiding the mismatch problem caused by fixed bandwidth division. This makes the subsequent calculation of the compensation degree more closely match the actual fluctuation pattern and improves the sensitivity of anomaly identification.

[0013] Preferably, obtaining the first compensation degree further includes: calculating the standard deviation of the amplitude of each frequency component in the left and right neighborhoods respectively, and calculating a symmetry index characterizing the fluctuation symmetry of the left and right neighborhoods accordingly; when the absolute value of the symmetry index is greater than a preset symmetry threshold, the standard deviation of the side with the smaller standard deviation is selected and combined with the proportion of the number of associated frequency sets to the total number of spatial frequencies to calculate the first compensation degree; otherwise, the relative deviation between the current spatial frequency amplitude value and the average amplitude of the associated frequency sets is combined with the proportion to calculate the first compensation degree.

[0014] This invention obtains a symmetry index by calculating the standard deviation of the amplitudes of the left and right neighboring regions. When there is asymmetry, the side with the smaller standard deviation is selected and its proportion in the neighboring region is used to calculate the first compensation level. When there is symmetry, the relative deviation between the center frequency and the mean of the neighboring region is used and its proportion is used for calculation. This method adaptively selects a compensation strategy according to different fluctuation patterns, which not only suppresses unilateral random interference but also highlights abnormal peaks in symmetrical fluctuations, significantly enhancing the robustness and rationality of the compensation level.

[0015] Preferably, the method for obtaining the theoretical resistance value includes: ;in, Indicates the first The theoretical resistance value at seconds, Indicates the initial resistance value. This represents the temperature coefficient of resistance of the conductor inside an insulated wire. Indicates the first Real-time temperature value per second. This indicates the initial temperature value.

[0016] Preferably, obtaining the second compensation degree includes: dividing the absolute value of the difference between the theoretical resistance value at each moment and the measured resistance value at the same moment by the initial resistance value to obtain a dimensionless relative resistance deviation; dividing the difference between the measured resistance value at that moment and the initial resistance value by the initial resistance value to obtain a relative resistance change rate; combining the relative resistance deviation and the relative resistance change rate and performing normalization processing to obtain a dimensionless second compensation degree, wherein the second compensation degree is greater when the relative resistance deviation is larger or the relative resistance change rate is larger.

[0017] This invention obtains the relative resistance deviation by dividing the absolute value of the deviation between the theoretical and measured resistances by the initial resistance, and then multiplying the relative deviation by the rate of change of the measured resistance relative to the initial resistance and normalizing the result to obtain the second compensation level. This method quantifies the enhancement effect of conductor resistance changes with temperature on signal attenuation, and the larger the deviation or the greater the rate of change, the stronger the compensation, achieving real-time and accurate compensation for signal attenuation.

[0018] Preferably, aligning the second compensation degree sequence with the first compensation degree sequence in the spatial dimension includes: arranging the second compensation degree sequence in whole seconds, while the sampling time interval of the temperature acquisition signal is less than one second; for each temperature sampling point, finding two adjacent whole seconds in the second compensation degree sequence, and using linear interpolation to calculate the second compensation degree after sampling corresponding to the temperature sampling point, so that the second compensation degree sequence after sampling corresponds one-to-one with each spatial position.

[0019] Preferably, obtaining the total compensation level and correcting the spatial frequency domain signal includes: multiplying the first compensation level by the sampled second compensation level at the corresponding spatial location to obtain the total compensation level, and then superimposing the total compensation level onto the corresponding original amplitude value to obtain the corrected amplitude value. The calculation formula is as follows: ; ;in, For the first The spatial frequency is at the ... The overall compensation level at each spatial location Indicates the first The first degree of compensation for each spatial frequency; Indicates the first The second compensation level after sampling corresponds to each spatial location. The original amplitude value. This is the corrected amplitude value.

[0020] This invention corrects errors by multiplying a first compensation level by a second, sampled compensation level to obtain a total compensation level, which is then superimposed onto the original amplitude value at the corresponding spatial frequency and location. This method deeply integrates frequency domain fluctuation compensation and time domain resistance attenuation compensation, enabling each spatial location and frequency to obtain a targeted comprehensive correction amount. This provides a high-confidence data foundation for abnormal fluctuation identification and significantly improves the accuracy of control.

[0021] Preferably, the step of identifying abnormal temperature fluctuation areas and performing temperature field regulation includes: calculating the relative difference between the sum of the absolute values ​​of the differences in amplitude values ​​before and after the correction of all spatial frequencies for each spatial location and the sum of the original amplitude values; determining that there is an abnormal temperature fluctuation at the spatial location when the relative difference is greater than a preset threshold; triggering an early warning message and outputting an adjustment signal to the heating power controller when the number of spatial locations with abnormal temperature fluctuations reaches a preset proportion; increasing the power setting value of the heating segment corresponding to the abnormal fluctuation area or extending the heating time of the segment; otherwise, maintaining the current heating parameters unchanged.

[0022] The beneficial effects of this invention are as follows: By integrating spatial frequency domain fluctuation compensation and time domain resistance attenuation compensation, full-dimensional adaptive control of the temperature field in the crosslinking process is achieved. Effective neighborhoods for each spatial frequency are adaptively determined through dynamic search, and the first compensation level is adaptively calculated based on the symmetry difference between the left and right neighborhoods or the deviation between the center frequency and the neighborhood mean, improving the sensitivity of anomaly identification and the robustness of the compensation level. The second compensation level is obtained by normalizing the product of the relative resistance deviation and the relative resistance change rate, quantifying the impact of conductor heating on signal attenuation. The frequency domain amplitude value is corrected by multiplying and superimposing the two compensation levels, providing a high-confidence data basis for anomaly fluctuation identification, thereby significantly improving temperature control accuracy and crosslinking quality consistency, and reducing energy consumption and scrap rate. Attached Figure Description

[0023] Figure 1 This is a flowchart of a method for controlling the temperature field in the crosslinking process of an environmentally friendly overhead insulated conductor according to the present invention; Figure 2 This is a schematic diagram of temperature field data acquisition and preprocessing; Figure 3 This is a comparison diagram of the axial temperature distribution of insulated conductors. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] This invention discloses an environmentally friendly method for temperature field control in the cross-linking process of overhead insulated conductors, referring to... Figure 1 This includes steps S1-S4: S1. Obtain the temperature field data of the surface of the insulated wire during the cross-linking process, and perform preprocessing to obtain the spatial frequency domain signal.

[0026] It should be noted that the temperature distribution along the axial direction on the surface of the insulated wire is uneven during the cross-linking process, and the original temperature signal contains measurement errors caused by heater radiation fluctuations, airflow disturbances, and sensor noise. In order to subsequently compensate for the fluctuations at different spatial frequencies in the temperature field, it is first necessary to convert the temperature acquisition signal in the spatial domain into a spatial frequency domain signal and perform noise reduction processing.

[0027] Based on this, this step continuously collects temperature data by using a non-contact temperature sensor array arranged along the axial direction of the insulated wire. After amplification, analog-to-digital conversion, and median filtering, the spatial frequency domain signal is obtained through Fourier transform.

[0028] Specifically, infrared temperature sensors are installed at equal intervals along the direction of travel of the insulated wires within the heating zone of the cross-linking furnace, and the sampling frequency of the infrared temperature sensors is set to [value missing]. The unit is Hertz, which is the number of samples collected per second. Each temperature value was set, and the total sampling time was set to [value]. seconds, total obtained There are 1 sampling points, among which ; with the first Taking one sampling point as an example for analysis, its corresponding spatial location is: The unit is meters, where The speed at which the insulated conductor is pulled is expressed in meters per second. The sampling time interval is in seconds.

[0029] Furthermore, the weak analog voltage signal output from the infrared temperature sensor is amplified to the input range of the analog-to-digital converter (ADC). The ADC then converts the amplified analog signal into a digital signal, yielding the original digital temperature sequence. The unit is Celsius, where The value range is 1 to The median filtering algorithm was used to process the original temperature digital sequence. Denoising processing is performed to achieve the following: Centered on a sampling point, a neighborhood of odd-numbered window lengths is selected. All temperature values ​​within this neighborhood are sorted by magnitude, and the median is taken as the filtered output value for that point. traverse all The denoised temperature signal sequence is obtained. The unit is Celsius.

[0030] Specifically, for the denoised temperature signal sequence A short-time Fourier transform is performed to obtain the spatial frequency domain signal. The short-time Fourier transform is a current technique, and its calculation formula will not be elaborated here. Through this transform, the first... The amplitude value of the complex coefficients corresponding to each spatial frequency This represents the intensity of temperature fluctuations at this spatial frequency, is dimensionless, and has a spatial frequency resolution of [value missing]. The unit is Hertz, and the effective frequency range of the frequency domain signal is 0 to 1000 Hz. hertz.

[0031] like Figure 2 As shown: Figure 2 This is a schematic diagram of temperature field data acquisition and preprocessing. As shown in the diagram, infrared temperature sensors arranged along the axial direction of the insulated wire continuously acquire temperature data within the heating section of the cross-linking furnace to obtain actual temperature data points. The temperature analog signal is amplified by an amplifier and converted into a digital signal by an analog-to-digital converter to obtain the original temperature digital sequence. After denoising by a median filtering algorithm, a denoised temperature signal sequence is obtained. A short-time Fourier transform is performed on the denoised temperature signal sequence to obtain the spatial frequency domain signal, and the amplitude values ​​of the Fourier coefficients corresponding to each spatial frequency are output.

[0032] Before the cross-linking process begins and before heating is started, the initial temperature value of the surface of the insulated wire is measured by an infrared temperature sensor and recorded as follows: The unit is degrees Celsius. Simultaneously, the initial resistance of this section of insulated conductor is measured using a micro-ohmmeter and recorded as . The unit is micro-ohms.

[0033] S2. Analyze the fluctuation of each spatial frequency in the spatial frequency domain signal and obtain the first compensation level.

[0034] It should be noted that the attenuation of the temperature field signal is related to the severity of spatial frequency fluctuations. More severe spatial frequency fluctuations indicate greater influence from factors such as heater layout and airflow disturbances, resulting in more pronounced temperature field inhomogeneity and requiring a larger compensation amount. Conversely, more stable spatial frequency fluctuations necessitate a smaller compensation amount. To quantify the fluctuation level of each spatial frequency, this step analyzes the amplitude differences and distribution symmetry between each frequency component and its neighboring frequency components based on the obtained spatial frequency domain amplitude sequence, thereby calculating the initial compensation level for each spatial frequency.

[0035] Based on this, this step obtains the amplitude values ​​of each frequency component by plotting a spatial frequency domain spectrum, and then uses the first... Taking a spatial frequency as an example, we traverse to its left and right sides to find frequency components with similar amplitude values, statistically analyze the neighborhood width and amplitude standard deviation, and calculate the first compensation degree in combination with the symmetry index.

[0036] Specifically, based on the obtained spatial frequency domain signal, the first... The amplitude value corresponding to each spatial frequency ,in The value range is 1 to All amplitude values ​​constitute an amplitude sequence. The amplitude value is dimensionless, representing the relative intensity of temperature fluctuations at that spatial frequency; iterates through all adjacent frequency components in the amplitude sequence, i.e., calculates... The value, Take from 1 Take the minimum of these differences and denote it as... This minimum amplitude difference is used to subsequently determine whether the amplitudes of the two frequency components are similar.

[0037] Furthermore, with the first Amplitude values ​​of spatial frequencies Based on the first Starting from each frequency, it iterates to the left until it encounters the first frequency component whose amplitude value is... The difference is greater than So far, record all frequency components traversed during this traversal to form the left neighborhood. Similarly, starting from the... Starting from each frequency, it iterates to the right until it encounters the first frequency component whose amplitude value is... The difference is greater than Up to this point, the right neighborhood is formed, and all frequency components in the left and right neighborhoods, along with the first... The frequency itself is collectively referred to as the first frequency. A set of associated frequencies of spatial frequencies, denoted as , where the total number of frequency components in the associated frequency set is . .

[0038] Specifically, calculate the first The arithmetic mean of the amplitudes of all frequency components in a set of associated frequencies of spatial frequencies is denoted as . Calculate the standard deviation of the amplitude of each frequency component in the left neighborhood, denoted as . Calculate the standard deviation of the amplitude of each frequency component in the right neighborhood, denoted as . Standard deviation reflects the degree of dispersion of amplitude fluctuations within a neighborhood; a larger standard deviation indicates more severe fluctuations.

[0039] Furthermore, based on the symmetry of the standard deviations of the amplitudes in the left and right neighboring regions, the first compensation level is calculated in two cases. First, calculate the symmetry index. The absolute value of this indicator ranges from 0 to 1. The closer the absolute value is to 0, the more symmetrical the fluctuations of the left and right neighborhoods are; the closer it is to 1, the more asymmetrical they are. When the absolute value of the symmetry indicator is greater than 0.3, the fluctuations of the left and right neighborhoods are considered asymmetrical. In this case, the neighborhood with the smaller standard deviation is selected as the main reference, combined with the total number of associated frequency sets. For the calculation of the first level of compensation, please refer to the following formula: ; in, The first level of compensation, in physical terms, characterizes the severity of temperature fluctuations at that spatial frequency and the required compensation intensity. The standard deviation of the amplitude of each frequency component in the left neighborhood. and the standard deviation of the amplitude of each frequency component in the right neighboring region The smaller value in Indicates the number of sets of associated frequencies. Total number of frequencies The proportion; This is an index for spatial frequencies.

[0040] When the fluctuations in the left and right neighboring regions are asymmetrical, the side with the smaller standard deviation exhibits relatively gentler fluctuations, and the data on that side more closely approximates the true temperature distribution. Therefore, a smaller standard deviation is selected. As a measure of fluctuation intensity, The larger the value, the greater the amplitude dispersion within that neighborhood, indicating more severe temperature fluctuations and a greater need for compensation; the proportion of the number of associated frequency sets. Reflecting the first The larger the spatial extent of the anomalous fluctuation group centered on a given frequency, the wider the range of the anomalous temperature region extending along the conductor, and the greater its impact on crosslinking quality, requiring stronger compensation. The numerator is the sum of the fluctuation intensity and the spatial extent, while the denominator is increased by one unit to normalize the entire fraction to a value between 0 and 1, facilitating subsequent calculations with the second compensation level. A larger fractional value indicates a stronger crosslinking effect. The more spatial frequencies correspond to temperature fluctuations, the more compensation is needed.

[0041] Specifically, when the absolute value of the symmetry index is less than or equal to 0.3, the fluctuations in the left and right neighborhoods are considered symmetrical. In this case, the first compensation degree is calculated based on the deviation between the center frequency amplitude and the average amplitude of the associated frequency set. The calculation formula is as follows: ; in, amplitude sequence The maximum value in, This indicates the relative deviation between the center frequency amplitude and the neighborhood average amplitude. They are the first The amplitude value of the first spatial frequency, the first The arithmetic mean of the amplitudes of all frequency components in the associated frequency set of a spatial frequency; Indicates the number of sets of associated frequencies. Total number of frequencies The proportion; For spatial frequency index; It is an absolute value function.

[0042] When the fluctuations of the left and right neighborhoods are symmetrical, the neighborhood mean This can better represent the overall level of the fluctuation group; at this point, the amplitude value of the center frequency... and The deviation reflects the prominence of this frequency point relative to the surrounding fluctuation group. The larger the deviation, the more anomalous the temperature fluctuation at that spatial frequency, and the stronger the compensation required. Divide the deviation by the maximum amplitude value. Normalization is performed to obtain the relative deviation. This makes it consistent with the proportion of spatial breadth. For fractions of the same order of magnitude, the numerator is the relative deviation plus the spatial extent, and the denominator is increased by one to achieve overall normalization. The larger the value of this fraction, the more significant the difference between the first and second orders of magnitude. The more spatial frequencies correspond to temperature fluctuations, the more compensation is needed.

[0043] Using the formulas for the two cases mentioned above, the first... The first compensation level of each spatial frequency Its value ranges from 0 to 1, and the larger the value, the greater the compensation intensity that needs to be applied to that spatial frequency.

[0044] Furthermore, sequentially... equal to 1 to The first compensation level sequence is obtained by calculating each spatial frequency. .

[0045] At this point, step S2 is complete, and the first compensation level corresponding to each spatial frequency is obtained.

[0046] S3. Obtain the second compensation level at each moment based on the real-time temperature and resistance changes of the insulated wire during the heating process.

[0047] It should be noted that the resistance of the insulated wire is one of the main factors affecting the signal response of the temperature sensor, and the resistance increases with increasing temperature. When uneven heating during the cross-linking process causes a sharp rise in the temperature of the insulation layer, the resistance of the conductors inside the wire, such as copper or aluminum, increases accordingly, thus affecting the heat conduction efficiency and the attenuation characteristics of the sensor signal. To quantify the impact of temperature changes on signal attenuation, this step calculates the second compensation level at each moment based on the initial temperature and initial resistance values ​​measured before the cross-linking process, combined with the real-time temperature and real-time resistance values ​​measured at each moment during the heating process.

[0048] Based on this, this step continuously collects the real-time temperature value of the surface of the insulated wire using an infrared temperature sensor, and simultaneously measures the real-time resistance value at the same location using a micro-ohmmeter. By using the physical relationship between resistance and temperature, the difference between the theoretical resistance value and the actual resistance value is compared. Combined with the relative rate of change of resistance, the second compensation level at each moment is finally obtained.

[0049] Specifically, the initial temperature value of the surface of the insulated wire before the cross-linking process begins and before heating is started. and the initial resistance value of that section of insulated wire. Initial temperature value The unit is degrees Celsius, initial resistance value The unit is microohms, and these two initial values ​​serve as the benchmark for subsequent comparisons.

[0050] Furthermore, after the heating process of the cross-linking step is started, infrared temperature sensors are used to collect the real-time temperature value of the surface of the insulated wire every second, and the result is recorded as follows: The real-time temperature value at seconds is The unit is degrees Celsius; simultaneously, at the same time, the real-time resistance value of the insulated wire at the corresponding position of the infrared temperature sensor is measured using a micro-ohmmeter, and recorded as the first value. The real-time resistance value at seconds is The unit is microohms; among which The value range is 1, 2, 3, ..., until the heating ends.

[0051] Specifically, based on the temperature resistance characteristics of metallic conductors, the first Theoretical resistance value per second From the initial resistance value Initial temperature value Real-time temperature value and the temperature coefficient of resistance of the conductor Jointly determined; Temperature coefficient of resistance The theoretical resistance value is obtained based on production information of the conductor material inside the insulated wire, expressed in degrees Celsius. The calculation formula is as follows: ; in, Indicates the first The theoretical resistance value calculated based on temperature change per second, in microohms; This indicates the initial resistance value of the insulated wire before the cross-linking process begins, expressed in microohms. Temperature coefficient of resistance of the conductor inside an insulated wire, expressed in degrees Celsius; Indicates the first The real-time temperature value of the surface of the insulated conductor per second, in degrees Celsius; This indicates the initial temperature value of the surface of the insulated conductor before the cross-linking process begins, expressed in degrees Celsius.

[0052] When the real-time temperature value Higher than the initial temperature value At that time, the difference Positive, theoretical resistance value Greater than the initial resistance value This reflects the physical law that resistance increases with increasing temperature; when the real-time temperature is lower than the initial temperature, the theoretical resistance decreases accordingly; adding 1 ensures that when the temperature difference is zero, the theoretical resistance equals the initial resistance. This relationship is based on a linear approximation model of the resistance-temperature of conductors and is applicable to the temperature variation range commonly encountered in cross-linking processes.

[0053] The first Theoretical resistance value per second Compared with the measured resistance value Compare the absolute values ​​of the differences between the two. This reflects the deviation between the actual thermal response and the ideal linear model; the larger the deviation, the more abnormal heating or uneven heat dissipation exists inside the insulation layer, resulting in greater signal attenuation and requiring greater compensation. To eliminate the influence of resistance dimensions, the resistance deviation is divided by the initial resistance value. The dimensionless relative deviation is obtained. Meanwhile, real-time resistance value Compared with the initial resistance value relative rate of change This reflects the percentage increase in resistance; the larger the percentage, the more severe the conductor heating and the stronger the signal attenuation. The second compensation level... The calculation formula is as follows: ; in, Indicates the first The second compensation level of the insulated conductor per second, with a value ranging from 0 to 1, is dimensionless; Indicates the first The theoretical resistance value per second, in microohms; Indicates the first The measured resistance value per second, in microohms; This indicates the initial resistance value of the insulated wire before the cross-linking process begins, expressed in microohms. This refers to the relative deviation of resistance, which is dimensionless. The relative rate of change of resistance is dimensionless; the addition of 1 in the denominator ensures that the term is 1 when the rate of change of resistance is zero, meaning that the degree of compensation is contributed only by the resistance deviation term.

[0054] Product term The resistance deviation is combined with the relative rate of change of resistance. The greater the difference between the theoretical and measured resistance values, the larger the first term becomes; the greater the increase in measured resistance value relative to the initial resistance value, the larger the second term becomes. A simultaneous increase in both terms indicates more severe actual signal attenuation, requiring greater compensation. Adding one to the denominator ensures the entire fraction falls between 0 and 1, achieving normalization and facilitating subsequent fusion calculations with the first level of compensation. The larger the value, the more significant the th... The greater the compensation intensity required for the temperature signal per second.

[0055] Furthermore, sequentially... The second compensation degree sequence is obtained by calculating at each time point from 1 to 2, 3, ... until the heating ends. ,in This represents the total number of seconds in the heating process.

[0056] At this point, step S3 is complete, and the second compensation level corresponding to each time step is obtained.

[0057] S4. Obtain the total compensation degree for each spatial frequency based on the first compensation degree sequence and the second compensation degree sequence, and correct the spatial frequency domain signal to identify abnormal temperature fluctuation regions and perform temperature field regulation.

[0058] It should be noted that the first compensation level sequence reflects the impact of the severity of temperature fluctuations at different spatial frequencies on the compensation requirements, while the second compensation level sequence reflects the impact of resistance changes at different times on signal attenuation. To obtain the comprehensive compensation intensity required for each spatial frequency at each time point, the first and second compensation level sequences need to be fused. Since the dimension of the first compensation level sequence is the total number of spatial frequencies... The dimension of the second compensation level sequence is the total number of seconds in the heating process. The original temperature signal has a total of [number] spatial dimensions. There are 10 sampling points, and a total of 100 sampling points in the time dimension. Since the two dimensions are inconsistent, it is necessary to sample the second compensation degree sequence to align it with the first compensation degree sequence in spatial dimension, and then obtain the total compensation degree of each spatial frequency at each spatial location through multiplication.

[0059] Based on this, this step downsamples the second compensation degree sequence according to the sampling time interval to obtain the second compensation degree sequence after sampling with the same dimension as the total number of spatial frequencies. Then, the first compensation degree is multiplied by the second compensation degree after sampling to obtain the total compensation degree. The total compensation degree is then superimposed on the original spatial frequency domain amplitude value to obtain the corrected amplitude value. Finally, the abnormal temperature fluctuation area is identified by comparing the difference between the amplitude values ​​before and after correction, and temperature field regulation is performed.

[0060] Specifically, the obtained first compensation degree sequence Constructing the first compensation level matrix Its form is: ;in, For one line The row vector of the column, Indicates the first The first compensation level for each spatial frequency is dimensionless and ranges from 0 to 1; the obtained second compensation level sequence Constructing a second compensation degree matrix Its form is: ;in, for A column vector with one row and one column, with superscript. Indicates transpose. Indicates the first The second compensation level is dimensionless and ranges from 0 to 1; The total number of seconds in the heating process is equal to the total sampling time. seconds, and satisfy Because a second compensation level is collected every second.

[0061] It should be noted that, due to the second compensation degree sequence The sampling interval is 1 second, meaning one value per second, while the sampling interval of the original temperature signal is... Seconds, typically much less than 1 second, have inconsistent time scales. To obtain the second compensation level corresponding to each temperature sampling moment, the second compensation level sequence needs to be interpolated.

[0062] Specifically, with the first The time corresponding to each temperature sampling point Using seconds as the target, find two adjacent integer seconds in the second compensation level sequence. and , making ,in For integers, calculate using linear interpolation. Second compensation level at time The linear interpolation formula is: ; in, and The first Second and the The second degree of compensation per second; for The offset relative to the whole second, in seconds, with a value ranging from 0 to 1; when When equal to an integer number of seconds, It is directly equal to the second compensation level corresponding to that second.

[0063] Through the above linear interpolation, for the common For each temperature sampling point, the corresponding second compensation level is calculated to obtain the second compensation level sequence after sampling. This sequence corresponds one-to-one with the temperature sampling points in time and with their spatial location indices. Consistent, among which linear interpolation is an existing mathematical method, and its error analysis will not be elaborated here.

[0064] Furthermore, the first compensation degree matrix With the second compensation degree matrix after sampling Perform multiplication to obtain the total compensation degree matrix. , with the first The spatial frequency and the first Taking a spatial location as an example, the total compensation level The calculation formula is as follows: ; in, Indicates the first The spatial frequency is at the ... The total compensation degree at each spatial location is dimensionless and ranges from 0 to 1. Indicates the first The first degree of compensation for each spatial frequency; Indicates the first The second compensation level after sampling corresponds to each spatial location.

[0065] It should be noted that the multiplication operation makes the total compensation level jointly affected by the spatial frequency fluctuation characteristics reflected by the first compensation level and the resistance change characteristics of the time dimension reflected by the second compensation level. When the fluctuation of a certain spatial frequency is more intense and the resistance deviation at the corresponding time of that spatial location is greater, the product of the two is larger, indicating that the comprehensive compensation intensity that needs to be applied at that location is greater.

[0066] Specifically, for the first The spatial frequency is at the ... Original amplitude value at each spatial location Its corrected amplitude value The calculation formula is as follows: ; in, Indicates the obtained first The spatial frequency is at the ... The original amplitude value at each spatial location is dimensionless. Indicates the first The spatial frequency is at the ... The total degree of compensation at each spatial location; This represents the corrected amplitude value, which is dimensionless; it is obtained by traversing all spatial frequencies. From 1 to and all spatial locations From 1 to The corrected spatial frequency domain amplitude matrix is ​​obtained. .

[0067] Furthermore, each spatial location Compare the corrected amplitude values ​​of all spatial frequencies with the original amplitude values ​​at that spatial location: For the first... For each spatial location, calculate the relative difference in amplitude values ​​before and after correction; when the relative difference exceeds a preset threshold... When an abnormal temperature fluctuation is detected at a certain location, a preset threshold is set. The value is 30, and the unit is percentage, representing the relative difference. The calculation formula is as follows:

[0068] Among them, molecules Indicates the first The sum of the absolute values ​​of the differences in amplitude values ​​before and after spatial frequency correction at each spatial location, with the denominator being... It represents the sum of the original amplitude values ​​of all spatial frequencies at that spatial location.

[0069] When the number of spatial locations with abnormal temperature fluctuations accounts for a majority of the total number of spatial locations When the proportion is greater than or equal to the exemplary value of 30%, an early warning message is triggered on the computer display screen. At the same time, an adjustment signal is output to the heating power controller of the crosslinking furnace to increase the power setting value of the heating section corresponding to the abnormal fluctuation area or extend the heating time of the section. When the proportion of the number of spatial locations with abnormal temperature fluctuations to the total number of spatial locations is less than the exemplary value of 30%, the current heating parameters are kept unchanged.

[0070] At this point, step S4 is complete, achieving precise identification and dynamic control of the temperature field in the crosslinking process, such as... Figure 3 As shown, Figure 3 This is a comparison chart of the axial temperature distribution of insulated wires. The comparison results show that under the traditional PID control strategy, the axial temperature of the wire fluctuates greatly, with obvious overshoot and undershoot phenomena. The temperature range is 142℃~168℃, which cannot stably fall within the optimal crosslinking temperature range, i.e., 145℃~155℃. However, after adopting the control method of this invention, the axial temperature of the wire is accurately controlled within the optimal range, the fluctuation range is greatly reduced, and the consistency of the crosslinking process and product quality are effectively improved.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the temperature field in the cross-linking process of environmentally friendly overhead insulated conductors, characterized in that, include: The temperature field data of the surface of the insulated wire during the cross-linking process is acquired and preprocessed. The spatial domain temperature acquisition signal is denoised and then transformed into a spatial frequency domain signal. For each spatial frequency in the spatial frequency domain signal, based on its amplitude difference with neighboring frequency components, fluctuation dispersion, and left and right neighbor symmetry, a first compensation degree characterizing its temperature fluctuation compensation requirement is obtained, forming a first compensation degree sequence. Based on the real-time temperature and measured resistance values ​​at each moment during the heating process of the insulated wire, combined with the initial temperature, initial resistance and conductor resistance temperature coefficient before heating, the difference between the theoretical resistance value and the measured resistance value is compared and combined with the relative rate of change of resistance to obtain the second degree of compensation characterizing the signal attenuation compensation requirement, thus forming the second degree of compensation sequence. Align and fuse the second compensation degree sequence with the first compensation degree sequence in the spatial dimension to obtain the total compensation degree of each spatial frequency at each spatial location. Use the total compensation degree to correct the amplitude value of the spatial frequency domain signal. Identify abnormal temperature fluctuation areas based on the relative difference between the amplitude values ​​before and after correction, and output an adjustment signal to the heating power controller to perform temperature field regulation.

2. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 1, characterized in that, The acquisition and preprocessing of temperature field data on the surface of the insulated conductor during the cross-linking process includes: installing non-contact infrared temperature sensors at equal intervals along the direction of travel of the insulated conductor in the heating section of the cross-linking furnace to form a temperature sensor array, continuously collecting temperature data on the surface of the insulated conductor; amplifying the analog voltage signal output by the infrared temperature sensors to the input range of the analog-to-digital converter, then converting it into a raw temperature digital sequence by the analog-to-digital converter, and obtaining the spatial frequency domain signal by Fourier transform after denoising the raw temperature digital sequence.

3. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 2, characterized in that, The original temperature digital sequence is denoised using a median filtering algorithm. A neighborhood with an odd window length is selected centered on the current sampling point. All temperature values ​​in the neighborhood are sorted by size, and the median is taken as the filtered output value of the sampling point. The denoised temperature signal sequence is obtained by traversing all sampling points. Then, a short-time Fourier transform is performed on the denoised temperature signal sequence to obtain the Fourier coefficients corresponding to each spatial frequency. The amplitude value represents the relative intensity of temperature fluctuation at the corresponding spatial frequency.

4. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 1, characterized in that, Obtaining the first compensation level includes: determining the associated frequency set for each spatial frequency, wherein the method for determining the associated frequency set is as follows: The amplitude difference of all adjacent frequency components in the amplitude sequence of the spatial frequency domain signal is traversed and the minimum value is taken as the minimum amplitude difference. Based on the amplitude value of the current spatial frequency, the frequency is traversed to the left and right sides respectively until the first frequency component whose difference from the reference amplitude value is greater than the sum of the minimum amplitude difference and the preset tolerance is encountered. The frequency components traversed constitute the left neighborhood and the right neighborhood respectively. The left neighborhood and the right neighborhood, together with the current spatial frequency itself, constitute the associated frequency set.

5. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 4, characterized in that, The attainment of the first level of compensation also includes: Calculate the standard deviation of the amplitude of each frequency component in the left and right neighborhoods respectively, and calculate the symmetry index representing the symmetry of fluctuations in the left and right neighborhoods accordingly. When the absolute value of the symmetry index is greater than a preset symmetry threshold, select the standard deviation of the smaller side and combine it with the proportion of the number of associated frequency sets to the total number of spatial frequencies to calculate the first compensation degree. Otherwise, calculate the first compensation degree by combining the relative deviation between the current spatial frequency amplitude value and the average amplitude of the associated frequency sets with the proportion.

6. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 1, characterized in that, The method for obtaining the theoretical resistance value includes: ； in, Indicates the first The theoretical resistance value at seconds, Indicates the initial resistance value. This represents the temperature coefficient of resistance of the conductor inside an insulated wire. Indicates the first Real-time temperature value per second. This indicates the initial temperature value.

7. The method for temperature field control in the cross-linking process of an environmentally friendly overhead insulated conductor according to claim 6, characterized in that, The acquisition of the second level of compensation includes: The absolute value of the difference between the theoretical resistance value at each moment and the measured resistance value at the same moment is divided by the initial resistance value to obtain the dimensionless relative resistance deviation; the difference between the measured resistance value at that moment and the initial resistance value is divided by the initial resistance value to obtain the relative resistance change rate; the relative resistance deviation and the relative resistance change rate are combined and normalized to obtain the dimensionless second compensation degree, and the second compensation degree is greater when the relative resistance deviation or the relative resistance change rate is greater.

8. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 1, characterized in that, Aligning the second compensation degree sequence with the first compensation degree sequence in the spatial dimension includes: The second compensation degree sequence is arranged in whole second intervals, while the sampling time interval of the temperature acquisition signal is less than one second. For each temperature sampling point, the two adjacent whole second intervals are found in the second compensation degree sequence, and the second compensation degree after sampling is calculated by linear interpolation, so that the second compensation degree sequence after sampling corresponds one-to-one with each spatial position.

9. The method for temperature field control in the cross-linking process of environmentally friendly overhead insulated conductors according to claim 1, characterized in that, The process of obtaining the total compensation level and correcting the spatial frequency domain signal includes: The total compensation level is obtained by multiplying the first compensation level by the second compensation level after sampling at the corresponding spatial location. This total compensation level is then superimposed onto the corresponding original amplitude value to obtain the corrected amplitude value. The calculation formula is as follows: ； ； in, For the first The spatial frequency is at the ... The overall compensation level at each spatial location Indicates the first The first degree of compensation for each spatial frequency; Indicates the first The second compensation level after sampling corresponds to each spatial location. The original amplitude value. This is the corrected amplitude value.

10. The method for temperature field control in the cross-linking process of an environmentally friendly overhead insulated conductor according to claim 1, characterized in that, The process of identifying abnormal temperature fluctuation areas and performing temperature field regulation includes: calculating the relative difference between the sum of the absolute values ​​of the differences in amplitude values ​​before and after the correction of all spatial frequencies for each spatial location and the sum of the original amplitude values; determining that there is an abnormal temperature fluctuation at the spatial location when the relative difference is greater than a preset threshold; triggering an early warning message and outputting an adjustment signal to the heating power controller when the number of spatial locations with abnormal temperature fluctuations reaches a preset proportion; increasing the power setting value of the heating segment corresponding to the abnormal fluctuation area or extending the heating time of the segment; otherwise, maintaining the current heating parameters unchanged.

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