Cable silicone rubber-XLPE interface pressure calibration curve generation device and method

Abstract

The invention discloses a cable silicone rubber-XLPE interface pressure calibration curve generation device and method. The device comprises a sample table board, a pressurizing device, a nonlinear high-energy ultrasonic testing system and an ultrasonic transducer, and a standard cable sample is fixed on the sample table board through a fixing clamp; the pressurizing device is arranged at the bottom of the standard cable sample and is used for applying different interface pressures to the standard cable sample; the ultrasonic transducer is used for transmitting ultrasonic waves to the standard cable sample according to a received sine wave signal transmitted by the nonlinear high-energy ultrasonic testing system, capturing a pressure signal of the standard cable sample and transmitting the pressure signal to the nonlinear high-energy ultrasonic testing system for signal conversion to obtain a pressure digital signal; and a fundamental wave amplitude and a second harmonic amplitude are extracted based on the pressure digital signal to calculate a nonlinear parameter, so that an interface pressure calibration curve of the interface pressure and the nonlinear parameter is obtained.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable condition monitoring technology, and more specifically, to a device and method for generating a pressure calibration curve of the silicone rubber-XLPE interface of a cable. Background Technology

[0002] The reliability of high-voltage power cable insulation systems hinges on the contact pressure at the interface between silicone rubber and cross-linked polyethylene (XLPE), which must be precisely controlled within a range of 0.10 to 0.25 MPa. If the interface pressure is too low, poor contact will result, leading to air gaps and partial discharge, accelerating insulation aging; if the pressure is too high, it may cause plastic deformation or damage to the insulation material, compromising its long-term insulation performance. Therefore, accurate measurement and calibration of this interface pressure are crucial for ensuring the safe operation of the cable.

[0003] However, existing interfacial pressure measurement technologies face significant challenges, failing to meet the accuracy and reliability requirements of engineering practice. Traditional contact measurement methods, such as embedding sensors in insulation layers or using mechanical probes for puncture measurements, inevitably damage the integrity of the sample. Sensor embedding causes permanent damage to the insulation layer, while probe puncture leaves permanent holes larger than 1 mm in diameter. This damage not only leads to measurement data deviations exceeding 30%, causing calibration distortion, but also requires the complete loss of the sample for each measurement, resulting in high costs and unsustainability. Another type of non-contact indirect measurement technology, such as estimating pressure through back-calculation of electrical parameters or finite element simulation, avoids physical contact, but its anti-interference capability and accuracy have significant deficiencies. In actual working environments with temperatures exceeding 40°C, the error of the electrical parameter back-calculation method increases sharply to over 25%, while finite element simulation, relying on idealized material model parameters, deviates significantly from the actual mechanical behavior of the material, and its calibration results lack engineering universality.

[0004] While emerging technologies based on nonlinear ultrasonic effects offer promising solutions for nondestructive calibration, their practical engineering applications still face significant bottlenecks. First, at the fundamental level of calibration, there is a lack of unified and standardized sample preparation specifications. Key factors such as the surface roughness of silicone rubber and overall dimensional tolerances are not clearly defined, making it difficult to reproduce and compare calibration results. Second, in terms of calibration process control, existing procedures lack systematization and precision. The accuracy of calibration pressure loading equipment is insufficient, with pressure fluctuations in conventional hydraulic equipment exceeding ±0.01 MPa. This fluctuation directly results in a data point dispersion of up to 12% in the pressure mapping curve, severely impacting calibration accuracy. Finally, at the signal processing level, the reliability of technologies ensuring efficient and high-precision separation of the fundamental (2.25 MHz) and second harmonic (4.5 MHz) signals is insufficient.

[0005] In view of the above situation and technical bottlenecks, there is an urgent need to develop a method and device for obtaining cable interface pressure calibration curves based on nonlinear ultrasound. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a device and method for generating pressure calibration curves at the interface of silicone rubber-XLPE for cables.

[0007] According to one aspect of the present invention, a device for generating a pressure calibration curve of a cable silicone rubber-XLPE interface is provided, comprising: a sample platform, a pressurizing device, a nonlinear high-energy ultrasonic testing system, and an ultrasonic transducer, wherein...

[0008] A standard cable sample is fixed to the sample platform using clamps.

[0009] The pressurizing device is located at the bottom of the standard cable sample and is used to apply different interfacial pressures to the standard cable sample;

[0010] The ultrasonic transducer is used to transmit ultrasonic waves to a standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, and to capture the pressure signal of the standard cable sample and transmit it to the nonlinear high-energy ultrasonic testing system for signal conversion to obtain a pressure digital signal. Based on the pressure digital signal, the fundamental amplitude and second harmonic amplitude are extracted to calculate the nonlinear parameters, thereby obtaining the interface pressure and the interface pressure calibration curve of the nonlinear parameters.

[0011] Optionally, it also includes a duplexer disposed between the nonlinear high-energy ultrasonic testing system and the ultrasonic transducer for amplifying the transmitted signal.

[0012] Optionally, it also includes a low-pass filter and an impedance matching module sequentially disposed between the duplexer and the nonlinear high-energy ultrasonic testing system, for denoising the acquired pressure signal.

[0013] Optionally, it also includes: a signal selector, connected to the nonlinear high-energy ultrasonic testing system, for switching the frequency of the sinusoidal signal generated by the nonlinear high-energy ultrasonic testing system.

[0014] Optionally, it also includes: an oscilloscope connected to the nonlinear high-energy ultrasonic testing system for displaying signal waveforms emitted, acquired, or processed by the nonlinear high-energy ultrasonic testing system.

[0015] According to another aspect of the present invention, a method for generating a pressure calibration curve at the interface of silicone rubber-XLPE for cables is provided, comprising:

[0016] Place the standard cable sample on the sample platform using a fixing clamp;

[0017] The ultrasonic transducer transmits ultrasonic waves to a standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, and applies a series of increasing pressures to the interface of the standard cable sample through a preset pressurization device.

[0018] The pressure signal at the standard cable interface is collected by an ultrasonic transducer and transmitted to a nonlinear high-energy ultrasonic testing system, which then converts the pressure signal into a digital signal.

[0019] The fundamental amplitude and second harmonic amplitude of the digital signal are extracted to obtain the fundamental amplitude variation curve and the second harmonic variation curve based on pressure.

[0020] Based on the fundamental amplitude variation curve and the second harmonic variation curve, an interface pressure calibration curve for nonlinear parameters and interface pressure is generated.

[0021] Optionally, an ultrasonic transducer transmits ultrasonic waves to a standard cable sample based on a sinusoidal signal received from a nonlinear high-energy ultrasonic testing system, including:

[0022] The sinusoidal signal emitted by the nonlinear high-energy ultrasonic testing system is amplified by a duplexer;

[0023] The amplified sine wave signal drives the ultrasonic transducer to emit an ultrasonic signal to a standard cable sample.

[0024] Optionally, the fundamental amplitude and second harmonic amplitude of the digital signal are extracted to obtain pressure-based fundamental amplitude variation curves and second harmonic variation curves, including:

[0025] Perform Fourier transform on the digital signal to extract the fundamental amplitude and the second harmonic amplitude;

[0026] Based on the fundamental wave amplitude and second harmonic amplitude under different interface pressures, the fundamental wave amplitude variation curve and the second harmonic variation curve are obtained.

[0027] Optionally, based on the fundamental amplitude variation curve and the second harmonic variation curve, an interface pressure calibration curve for nonlinear parameters and interface pressure is generated, including:

[0028] Based on the fundamental wave amplitude variation curve and the second harmonic variation curve, the nonlinear parameters under different interface pressures are calculated respectively.

[0029] By fitting data points of different interfacial pressures and their corresponding nonlinear parameters, an interfacial pressure calibration curve is generated.

[0030] Optionally, the expression for calculating the nonlinear parameter β is:

[0031] β=A2 / A1 2

[0032] In the formula, A1 is the fundamental frequency amplitude and A2 is the second harmonic frequency amplitude.

[0033] Optionally, the expression for the interface pressure calibration curve is:

[0034] β=aP 2 +bP+c

[0035] In the formula, β is a nonlinear parameter, P is the interfacial pressure, and a, b, and c are fitting coefficients.

[0036] Therefore, the cable silicone rubber-XLPE interface pressure calibration curve generation device proposed in this invention adopts a modular design, including an ultrasonic transmitting and receiving module, a pressure application module, and a data processing unit, which is compact and easy to integrate. The method, through a standardized pressure loading and signal acquisition process, is applicable to silicone rubber-XLPE cable samples of different specifications, without the need for complex pretreatment or destructive testing. This reduces testing costs and improves the convenience of field applications. Attached Figure Description

[0037] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0038] Figure 1 This is a schematic diagram of the structure of the cable silicone rubber-XLPE interface pressure calibration curve generation device provided in an exemplary embodiment of the present invention;

[0039] Figure 2 This is a schematic flowchart of a method for generating a pressure calibration curve at the silicone rubber-XLPE interface of a cable, provided in an exemplary embodiment of the present invention.

[0040] Figure 3a This is a schematic diagram of a silicone rubber sample provided in an exemplary embodiment of the present invention;

[0041] Figure 3b This is a schematic diagram of a cross-linked polyethylene sample provided in an exemplary embodiment of the present invention;

[0042] Figure 4a This is a typical waveform reflection diagram provided by an exemplary embodiment of the present invention;

[0043] Figure 4b This is a spectrum verification diagram provided by an exemplary embodiment of the present invention;

[0044] Figure 5a This is a schematic diagram of the fundamental amplitude variation curve provided in an exemplary embodiment of the present invention;

[0045] Figure 5b This is a schematic diagram of the second harmonic amplitude variation curve provided by an exemplary embodiment of the present invention. Detailed Implementation

[0046] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0047] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0048] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0049] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0050] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0051] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0052] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0053] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0054] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0055] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0056] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0057] Figure 1 This is a schematic diagram of the structure of a cable silicone rubber-XLPE interface pressure calibration curve generation device provided in an exemplary embodiment of the present invention. Figure 1 As shown, the device for generating the pressure calibration curve of the silicone rubber-XLPE interface for cables includes: a sample platform, a pressurizing device, a nonlinear high-energy ultrasonic testing system, and an ultrasonic transducer.

[0058] Standard cable samples are fixed on the sample platform using clamps.

[0059] The pressurizing device is located at the bottom of the standard cable sample and is used to apply different interfacial pressures to the standard cable sample;

[0060] The ultrasonic transducer is used to transmit ultrasonic waves to a standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, and to capture the pressure signal of the standard cable sample and transmit it to the nonlinear high-energy ultrasonic testing system for signal conversion to obtain a pressure digital signal. Based on the pressure digital signal, the fundamental amplitude and second harmonic amplitude are extracted to calculate the nonlinear parameters, thereby obtaining the interface pressure and the interface pressure calibration curve of the nonlinear parameters.

[0061] Optionally, it also includes a duplexer disposed between the nonlinear high-energy ultrasonic testing system and the ultrasonic transducer for amplifying the transmitted signal.

[0062] Optionally, it also includes a low-pass filter and an impedance matching module sequentially disposed between the duplexer and the nonlinear high-energy ultrasonic testing system, for denoising the acquired pressure signal.

[0063] Optionally, it also includes: a signal selector, connected to the nonlinear high-energy ultrasonic testing system, for switching the frequency of the sinusoidal signal generated by the nonlinear high-energy ultrasonic testing system.

[0064] Optionally, it also includes: an oscilloscope connected to the nonlinear high-energy ultrasonic testing system for displaying signal waveforms emitted, acquired, or processed by the nonlinear high-energy ultrasonic testing system.

[0065] Specifically, this invention aims to provide a method and apparatus for obtaining cable interface pressure calibration curves based on nonlinear ultrasound, solving key problems such as inconsistent sample bases, low accuracy of the calibration process, and poor reliability of signal separation. The specific objectives are as follows:

[0066] 1. Establish standardized sample specifications and interface characterization methods: By specifying the geometric dimensions of silicone rubber (100×100×15mm, XLPE 10×100×9mm) and surface roughness characteristics (4μm radius of semicircular protrusions, 20μm spacing) for silicone rubber and XLPE, calibration data deviations caused by sample differences are eliminated. Specifically, surface morphology parameters are quantified based on white light interferometry, and a standard contact interface model is established by combining the material's acoustic properties. This provides a reusable benchmark sample library for nonlinear ultrasonic calibration, enabling direct comparability of β-P curves generated by different laboratories or production batches, solving the problem of data non-reusability caused by sample randomness in traditional calibration.

[0067] 2. Achieving High-Precision Gradient Pressure Loading Control: A hydraulic platform applies a gradient pressure of 0-0.2 MPa in 0.05 MPa steps, and a pressure stabilization mechanism (30-minute rest period after loading) suppresses material creep interference. The key innovation of the control system lies in compressing pressure fluctuations to within ±0.005 MPa, while introducing a real-time feedback calibration module to dynamically correct pressure deviations. This directly improves the linearity and dispersion tolerance of the β-P calibration curve, reducing the database dispersion from 12% to within 5%, providing a high-confidence benchmark for engineering applications.

[0068] 3. Development of a dual-channel harmonic separation system: A parallel filtering channel was designed: a low-pass filter (1.5-2.25MHz) accurately extracts the fundamental amplitude A1, and a band-pass filter (3.0-4.5MHz) captures the second harmonic amplitude A2. The technological breakthrough lies in the dual-channel collaborative architecture with a frequency band isolation >40dB, effectively suppressing frequency band cross-interference. Combined with time-frequency analysis algorithms, the harmonic purity is verified to be >97%. This design improves the harmonic signal-to-noise ratio from <10dB to >25dB, ensuring β = A2 / A1. 2 The accuracy of the calculations fundamentally solves the problem of amplitude measurement distortion caused by conventional single filters.

[0069] This invention forms a closed-loop calibration chain through three technologies, enabling the calibration database to have reproducibility between laboratories, robustness to complex working conditions, and convenient engineering access, completely reversing the inefficient "one experiment, one calibration" mode in traditional methods.

[0070] This invention relates to a method and apparatus for obtaining pressure calibration curves of the silicone rubber-XLPE interface in cables based on nonlinear ultrasonic effects. This method achieves high-precision calibration by establishing a quantitative mapping between the nonlinear effect of interfacial contact and pressure. Its core lies in integrating three major technical elements: standardized sample preparation, precise gradient pressure loading, and dual-channel harmonic separation. First, standard samples of silicone rubber (100mm×100mm×15mm) and XLPE layered structures (10mm×100mm×9mm) are prepared (dimensional tolerance ±0.5mm). White light interferometry confirms that the silicone rubber contact surface has semi-circular periodic protrusions with a radius of 4μm and a spacing of 20μm, ensuring consistent acoustic interface characteristics. Then, a computer-controlled closed-loop hydraulic platform applies a gradient pressure of 0 to 0.2MPa (step size 0.05MPa, accuracy ≤ ±0.00) to the interface. At pressure levels of 5 MPa, the pressure was allowed to stand for 30 minutes at each level to eliminate material creep interference. Then, Hanning window amplitude-modulated ultrasonic waves with a center frequency of 2.25 MHz were incident perpendicularly onto the interface via a planar piezoelectric transducer. The reflected waves were received and input into a dual-channel harmonic separation system. A low-pass filter bank (passband 1.5–2.25 MHz) with an 8th-order Butterworth topology accurately extracted the fundamental amplitude A1, while a band-pass filter bank of the same order (passband 3.0–4.5 MHz) suppressed fundamental frequency leakage and high-frequency noise to capture the 4.5 MHz second harmonic amplitude A2. Finally, the nonlinear coefficient β = A2 / A1 was calculated for each pressure point. 2 A database of β-P calibration curves covering the entire range of 0-0.25 MPa was generated through fitting. This method breaks through three major bottlenecks: missing sample specifications, pressure loading fluctuations, and signal separation distortion. The constructed curves have a linear correlation coefficient R0. 2 With a pressure inversion error of ≤1.8% and a value of ≥0.995, it provides a reusable engineering benchmark for the reliability of high-voltage cable insulation.

[0071] This embodiment provides a method and apparatus for obtaining the interface pressure calibration curve of silicone rubber-XLPE in cables based on nonlinear ultrasonic effects, specifically for the accurate measurement and calibration of the interface pressure between silicone rubber and cross-linked polyethylene (XLPE) in high-voltage cables. The following provides a detailed description of the apparatus structure and method steps:

[0072] Specifically, refer to Figure 1As shown, the nonlinear high-energy ultrasonic testing system (ultrasonic excitation-acquisition integrated module, such as the RITEC system) includes a core control and measurement unit that integrates signal generation, power amplification, and signal acquisition functions. It generates adjustable high-voltage ultrasonic pulses from 100kHz to 1MHz (output through the "RF BURST NO.1" port) to excite the transducer to emit nonlinear ultrasonic waves. It receives signals in real time through the "RECEIVER" channel (sampling rate ≥10MS / s) to complete analog-to-digital conversion and preprocessing. Through the "SNAP" interface on the backplane, it expands to include modules such as a unified scheduling duplexer and pressurization device to achieve fully automated measurement.

[0073] A duplexer is a signal routing switching device that uses an internal electronic switch to direct the signal to the transmitting transducer at the moment of transmission (when a high-voltage pulse is output) and switch the path at the moment of reception to allow the echo signal to be transmitted back to the RITEC receiver, thus avoiding damage to the receiving circuit from the high voltage of the transmitter; at the same time, it ensures that the transmitting and receiving actions are strictly separated to prevent signal crosstalk.

[0074] Signal selector: This is a multi-channel signal switcher. It can manually or automatically switch between different combinations of transmitting / receiving transducers; it supports multiple transducer connections without the need for frequent cable plugging and unplugging.

[0075] Ultrasonic transducer: It is a high-sensitivity piezoelectric ceramic sensor that emits and receives ultrasonic waves passing through the silicone rubber-XLPE interface, converting the sound waves into electrical signals; it works with an impedance matching module to optimize signal transmission efficiency and reduce energy loss.

[0076] Pressurization device: includes a precision pressure loading device and a pressure sensor. The pressure loading device is controlled by a servo motor, with an application range of 0 to 10 MPa and an accuracy of ±0.01 MPa; the pressure sensor is used to monitor the actual pressure at the interface in real time.

[0077] Low-pass filter: This is a noise suppression circuit used to remove ambient noise >1MHz before the signal enters the receiver, retaining the fundamental frequency (100kHz–1MHz) and harmonic components, and ensuring that the harmonic amplitude data for subsequent analysis is pure and reliable.

[0078] Impedance matching: This is a circuit tuning module used to adjust the circuit impedance (typically 50Ω) to match the output impedance of the nonlinear high-energy ultrasonic testing system with the transducer impedance (such as the capacitive load of PZT-5H), maximizing the sound wave transmission / reception efficiency, reducing energy reflection caused by impedance mismatch, protecting the system, and improving signal quality.

[0079] Therefore, the cable silicone rubber-XLPE interface pressure calibration curve generation device proposed in this invention adopts a modular design, including an ultrasonic transmitting and receiving module, a pressure application module, and a data processing unit, which is compact and easy to integrate. The method, through a standardized pressure loading and signal acquisition process, is applicable to silicone rubber-XLPE cable samples of different specifications, without the need for complex pretreatment or destructive testing. This reduces testing costs and improves the convenience of field applications.

[0080] In one embodiment of the present invention, Figure 2 A flowchart illustrating a method for generating a pressure calibration curve at the silicone rubber-XLPE interface for cables is provided. (Refer to...) Figure 2 As shown, the method 200 for generating the interface pressure calibration curve of silicone rubber-XLPE for cables includes:

[0081] Step 201: Place the standard cable sample on the sample platform using the fixing clamp;

[0082] Step 202: The ultrasonic transducer transmits ultrasonic waves to the standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, and applies a series of increasing pressures to the interface of the standard cable sample through a preset pressurization device.

[0083] Step 203: The pressure signal at the standard cable interface is acquired by an ultrasonic transducer and transmitted to a nonlinear high-energy ultrasonic testing system, which then converts the pressure signal into a digital signal.

[0084] Step 204: Extract the fundamental amplitude and second harmonic amplitude of the digital signal to obtain the fundamental amplitude variation curve and second harmonic variation curve based on pressure;

[0085] Step 205: Based on the fundamental amplitude variation curve and the second harmonic variation curve, generate the interface pressure calibration curve for nonlinear parameters and interface pressure.

[0086] Optionally, an ultrasonic transducer transmits ultrasonic waves to a standard cable sample based on a sinusoidal signal received from a nonlinear high-energy ultrasonic testing system, including:

[0087] The sinusoidal signal emitted by the nonlinear high-energy ultrasonic testing system is amplified by a duplexer;

[0088] The amplified sine wave signal drives the ultrasonic transducer to emit an ultrasonic signal to a standard cable sample.

[0089] Optionally, the fundamental amplitude and second harmonic amplitude of the digital signal are extracted to obtain pressure-based fundamental amplitude variation curves and second harmonic variation curves, including:

[0090] Perform Fourier transform on the digital signal to extract the fundamental amplitude and the second harmonic amplitude;

[0091] Based on the fundamental wave amplitude and second harmonic amplitude under different interface pressures, the fundamental wave amplitude variation curve and the second harmonic variation curve are obtained.

[0092] Optionally, based on the fundamental amplitude variation curve and the second harmonic variation curve, an interface pressure calibration curve for nonlinear parameters and interface pressure is generated, including:

[0093] Based on the fundamental wave amplitude variation curve and the second harmonic variation curve, the nonlinear parameters under different interface pressures are calculated respectively.

[0094] By fitting data points of different interfacial pressures and their corresponding nonlinear parameters, an interfacial pressure calibration curve is generated.

[0095] Optionally, the expression for calculating the nonlinear parameter β is:

[0096] β=A2 / A1 2

[0097] In the formula, A1 is the fundamental frequency amplitude and A2 is the second harmonic frequency amplitude.

[0098] Optionally, the expression for the interface pressure calibration curve is:

[0099] β=aP 2 +bP+c

[0100] In the formula, β is a nonlinear parameter, P is the interfacial pressure, and a, b, and c are fitting coefficients.

[0101] Specifically, the implementation steps of the method for generating the pressure calibration curve of the cable silicone rubber-XLPE interface based on the cable silicone rubber-XLPE interface pressure calibration curve generation device are as follows:

[0102] Step 1: Sample Preparation

[0103] Select standard cable samples, including silicone rubber insulation and XLPE insulation, such as... Figure 3a and Figure 3b As shown, the interface is smooth and without obvious defects. The sample is placed in a fixture, and an acoustic coupling agent (such as ultrasonic coupling adhesive) is used to ensure good contact between the ultrasonic transducer and the sample surface.

[0104] Step 2: Ultrasonic signal transmission and reception

[0105] A 5MHz sine wave signal is generated by a signal generator, amplified by a duplexer, and then drives an ultrasonic transducer to emit ultrasonic waves. After the ultrasonic waves pass through the silicone rubber-XLPE interface of the cable, the ultrasonic transducer captures the pressure signal. The pressure signal is then processed by a duplexer, a low-pass filter, and impedance matching to remove noise and amplification. The collected pressure signal is then converted into an electrical signal, and finally into a digital signal.

[0106] Step 3: Pressure Application and Data Acquisition

[0107] A series of incremental pressures, ranging from 0.5 MPa to 8 MPa, were applied to the sample interface using a pressurizing device, with increments of 0.5 MPa. At each pressure point, ultrasonic signals were repeatedly transmitted and received 10 times, and the time-domain waveform and frequency-domain spectrum of each received signal were recorded. Figure 4a and Figure 4b As shown.

[0108] Step 4: Nonlinear Ultrasonic Effect Analysis

[0109] The acquired digital signal is subjected to a Fourier transform to extract the amplitudes of the fundamental and second harmonic frequencies. The nonlinear parameter β is calculated and defined as: β = A2 / A1 2 Where A1 is the fundamental amplitude and A2 is the second harmonic amplitude. The correlation between the nonlinear parameter β and the interface pressure is analyzed, and the β value corresponding to each pressure point is recorded. For example... Figure 5a and Figure 5b As shown.

[0110] Step 5: Calibration curve generation

[0111] A calibration curve is generated by fitting data points with interfacial pressure as the horizontal axis and the nonlinear parameter β as the vertical axis. A quadratic polynomial fitting method is used.

[0112] β=aP 2 +bP+c

[0113] Where P is the interfacial pressure, and a, b, and c are fitting coefficients. In this embodiment, the fitting result is: β = 0.002P 2 +0.015P+0.01, goodness of fit R2=0.98.

[0114] Verification and Calibration: Using test samples with known pressure, repeat steps 2 to 4 to verify the accuracy of the calibration curve. If the deviation exceeds ±5%, adjust the coupling conditions or recalibrate the pressure loading device and repeat the experiment.

[0115] The essential function of the calibration curve is to establish a mapping relationship between the nonlinear parameter β and the actual interface pressure through experiments, forming a quantifiable mathematical curve. Specifically, its functions include: first, converting abstract ultrasonic signals into intuitive pressure values ​​(MPa), achieving quantification of nondestructive testing; second, providing a unified conversion standard for different devices, avoiding measurement deviations caused by sensor differences; and third, allowing field personnel to obtain pressure values ​​directly from tables or formulas without needing to understand complex acoustic principles. Therefore, the calibration curve can be used for real-time monitoring of cable pressure.

[0116] The method and apparatus of this embodiment successfully obtained the calibration curve of the interface pressure and nonlinear ultrasonic parameters of the silicone rubber-XLPE cable. Experimental results show that the nonlinear parameter β exhibits a good quadratic correlation with the interface pressure, the measurement accuracy reaches ±0.05MPa, and the repeatability error is less than 3%. This method is suitable for interface pressure detection in the manufacturing and operation and maintenance of high-voltage cables and has high engineering application value.

[0117] Therefore, the present invention has the following beneficial effects:

[0118] First, this invention achieves high-precision interface pressure measurement. By utilizing the nonlinear ultrasonic effect, characteristic parameters such as the second harmonic amplitude of the ultrasonic signal are extracted, and a calibration curve of interface pressure versus the nonlinear parameter β is constructed. The measurement accuracy reaches ±0.05 MPa, with a repeatability error of less than 3%. Experimental results show that the nonlinear parameter β exhibits a stable quadratic correlation with the interface pressure (goodness of fit R0). 2 =0.98), ensuring the reliability and accuracy of the calibration curve. This high-precision measurement effectively compensates for the shortcomings of traditional methods (such as mechanical stress testing) in complex interface environments.

[0119] Secondly, the method of this invention is simple to operate and highly applicable. The device adopts a modular design, including an ultrasonic transmitting and receiving module, a pressure application module, and a data processing unit, making it compact and easy to integrate. The method, through standardized pressure loading and signal acquisition procedures, is applicable to silicone rubber-XLPE cable samples of different specifications, eliminating the need for complex pretreatment or destructive testing. This reduces testing costs and improves the convenience of field applications.

[0120] Furthermore, this invention has significant application value in the manufacturing and operation maintenance of high-voltage cables. The pressure state at the interface between silicone rubber and XLPE directly affects the insulation performance and service life of the cable. The calibration curve provided by this invention can be used to monitor the interface pressure in real time, promptly identify potential defects, thereby optimizing cable manufacturing processes, extending service life, and reducing the risk of power system failures.

[0121] In summary, this invention achieves accurate and non-destructive measurement of interface pressure in high-voltage cables using nonlinear ultrasonic technology. It is highly accurate, easy to operate, and widely applicable, providing efficient and reliable technical support for cable manufacturing and power system maintenance. It has significant engineering practicality and economic benefits.

[0122] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A device for generating a pressure calibration curve at the interface of silicone rubber-XLPE for cables, characterized in that, include: The sample platform, pressurization device, nonlinear high-energy ultrasonic testing system, and ultrasonic transducer, among which... A standard cable sample is fixed to the sample platform by a fixing clamp; The pressurizing device is located at the bottom of the standard cable sample and is used to apply different interfacial pressures to the standard cable sample. The ultrasonic transducer is used to transmit ultrasonic waves to the standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, and to capture the pressure signal of the standard cable sample and transmit it to the nonlinear high-energy ultrasonic testing system for signal conversion to obtain a pressure digital signal. Based on the pressure digital signal, the fundamental amplitude and second harmonic amplitude are extracted to calculate the nonlinear parameters, thereby obtaining the interface pressure and the interface pressure calibration curve of the nonlinear parameters.

2. The apparatus according to claim 1, characterized in that, Also includes: A duplexer is installed between the nonlinear high-energy ultrasonic testing system and the ultrasonic transducer to amplify the transmitted signal.

3. The apparatus according to claim 1, characterized in that, Also includes: A low-pass filter and an impedance matching module are sequentially arranged between the duplexer and the nonlinear high-energy ultrasonic testing system to perform noise reduction processing on the acquired pressure signal.

4. The apparatus according to claim 1, characterized in that, Also includes: A signal selector, connected to the nonlinear high-energy ultrasonic testing system, is used to switch the frequency of the sinusoidal signal generated by the nonlinear high-energy ultrasonic testing system.

5. The apparatus according to claim 1, characterized in that, Also includes: An oscilloscope, connected to the nonlinear high-energy ultrasonic testing system, is used to display the signal waveforms emitted, acquired, or processed by the nonlinear high-energy ultrasonic testing system.

6. The method for generating a cable silicone rubber-XLPE interface pressure calibration curve using the cable silicone rubber-XLPE interface pressure calibration curve generation device according to any one of claims 1-5, characterized in that, include: Place the standard cable sample on the sample platform using a fixing clamp; The ultrasonic transducer transmits ultrasonic waves to the standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, and applies a series of increasing pressures to the interface of the standard cable sample through a preset pressurization device. The pressure signal at the standard cable interface is acquired by the ultrasonic transducer and transmitted to the nonlinear high-energy ultrasonic testing system, which then converts the pressure signal into a digital signal. The fundamental amplitude and second harmonic amplitude of the digital signal are extracted to obtain the fundamental amplitude variation curve and the second harmonic variation curve based on pressure. Based on the fundamental amplitude variation curve and the second harmonic variation curve, an interface pressure calibration curve for nonlinear parameters and interface pressure is generated.

7. The method according to claim 6, characterized in that, The ultrasonic transducer transmits ultrasonic waves to the standard cable sample based on the sinusoidal signal received from the nonlinear high-energy ultrasonic testing system, including: The sinusoidal signal emitted by the nonlinear high-energy ultrasonic testing system is amplified by a duplexer; The ultrasonic transducer is driven by the amplified sine wave signal to emit an ultrasonic signal to the standard cable sample.

8. The method according to claim 6, characterized in that, Extract the fundamental amplitude and second harmonic amplitude of the digital signal to obtain pressure-based fundamental amplitude variation curves and second harmonic variation curves, including: Perform a Fourier transform on the digital signal to extract the fundamental amplitude and the second harmonic amplitude; Based on the fundamental wave amplitude and the second harmonic amplitude under different interface pressures, the fundamental wave amplitude variation curve and the second harmonic variation curve are obtained.

9. The method according to claim 6, characterized in that, Based on the fundamental wave amplitude variation curve and the second harmonic variation curve, an interface pressure calibration curve for nonlinear parameters and interface pressure is generated, including: Based on the fundamental wave amplitude variation curve and the second harmonic variation curve, calculate the nonlinear parameters under different interface pressures; By fitting data points of different interface pressures and their corresponding nonlinear parameters, the interface pressure calibration curve is generated.

10. The method according to claim 9, characterized in that, The expression for calculating the nonlinear parameter β is as follows: β=A2 / A1 2 In the formula, A1 is the fundamental frequency amplitude and A2 is the second harmonic frequency amplitude.

11. The method according to claim 6, characterized in that, The expression for the interface pressure calibration curve is: β=aP 2 +bP+c In the formula, β is a nonlinear parameter, P is the interfacial pressure, and a, b, and c are fitting coefficients.

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