Method for calculating x-ray intensity distribution in power cables

Abstract

The application discloses a kind of calculation methods of X-ray intensity distribution in power cable, first using multi-frequency X-ray machine to five kinds of power cable materials of copper, aluminum, XLPE, silicone rubber and semiconductive layer, record initial X-ray dose rate and dose rate after penetration;Second, the transmittance of different materials through different thickness, average attenuation coefficient and each section average attenuation coefficient are calculated by X-ray attenuation formula, and the fitting formula is obtained;By comparing the results of traditional method with the results of the application calculation method, it can be found that when using traditional attenuation coefficient calculation, due to lack of measurement of X-ray attenuation coefficient of multi-frequency X-ray source transmission material and consideration of multiple hardening phenomenon occurred when cable material is irradiated by X-ray, larger error can be caused.It can be confirmed that the calculation method of this experiment is more accurate than traditional method.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage cable safety technology, specifically relating to a method for calculating the X-ray intensity distribution inside a power cable. Background Technology

[0002] With the increasing use of power cables, high-voltage cable faults have become more frequent. The main cause of cable insulation accidents is partial discharge. Currently, my country generally implements live-line testing or online monitoring for partial discharge detection of high-voltage cables, but this is insufficient to effectively detect insulation defects in the cable body and accessories, resulting in a significantly low defect detection rate. Since partial discharge in high-voltage cables is mostly caused by air-gap defects or air-gap defects induced by strong electric fields, it exhibits a distinct intermittent characteristic. To address the intermittent nature of partial discharge in high-voltage cables, moderately exciting internal air-gap defects with X-rays can reduce the intermittency of partial discharge, thereby effectively investigating insulation defects in the cable body and accessories. The main metallic materials of power cables are copper and aluminum, while the insulation materials are mainly XLPE, silicone rubber, and a semi-conductive layer.

[0003] Since the degree of partial discharge in power cables excited by X-rays is closely related to the radiation dose and intensity of X-rays, and the internal materials and structure of power cables determine the distribution of external radiation inside, it is of great significance to study the measurement of X-ray attenuation coefficients of typical power cable materials. Summary of the Invention

[0004] To address the technical problems existing in the background art, the present invention aims to provide a method for calculating the X-ray intensity distribution within power cables. By applying X-ray irradiation to five power cable materials—copper, aluminum, XLPE, silicone rubber, and a semi-conductive layer—using a multi-frequency X-ray machine, the transmittance and attenuation coefficient are calculated. Taking into account the measurement of the X-ray attenuation coefficient of the material transmitted by the multi-frequency X-ray source and the multiple hardening phenomenon that occurs when the cable material is irradiated by X-rays, the calculated transmittance of the X-ray-transmitted power cable is more accurate than that of traditional methods.

[0005] To solve the technical problem, the technical solution of the present invention is as follows:

[0006] A method for calculating the X-ray intensity distribution inside a power cable, considering the X-ray attenuation coefficients of different materials, the method includes the following steps:

[0007] Step S1: Obtain the initial dose rate, wherein the initial dose rate is the transmission dose rate under experimental conditions without a sample;

[0008] Step S2: Obtain the secondary dose rate, wherein the secondary dose rate is the transmission dose rate under experimental conditions with the sample added;

[0009] Step S3: Using the obtained initial dose rate and secondary dose rate, calculate the relationship between the transmittance and thickness of various power cable materials, the average linear attenuation coefficient of various power cable materials, and the average linear attenuation coefficient of each segment. Finally, obtain the relationship diagram of the average linear attenuation coefficient of various power cable materials under different thickness conditions and the average linear attenuation coefficient of each segment.

[0010] Step S4: Based on the relationship diagram, determine the transmittance of the X-ray transmission power cable.

[0011] Furthermore, the X-ray probe was placed horizontally 10 cm in front of the X-ray emitter, and its transmission dose rate was measured to obtain the initial dose rate; the experimental sample was irradiated with the X-ray emitter, and the X-ray probe was placed horizontally 10 cm in front of the X-ray emitter, and its transmission dose rate was measured to obtain the secondary dose rate.

[0012] Furthermore, the secondary dose rate includes the transmission dose rates of five power cable materials: copper, aluminum, XLPE, silicone rubber, and semiconductive layer.

[0013] Furthermore, using the formula I = I0e -μx Calculate the average linear attenuation coefficient and the average linear attenuation coefficient of each segment for various power cable materials; where I represents the intensity of transmitted X-rays, I0 represents the intensity of incident X-rays, and μ represents the attenuation coefficient (cm). -1 ), where x represents the thickness (cm) of the material through which the X-rays pass during transmission.

[0014] Furthermore, based on the aforementioned relationship diagram, considering the measurement of the X-ray attenuation coefficient of the multi-frequency X-ray source transmission material and the multiple hardening phenomenon that occurs when the cable material is irradiated by X-rays, the transmittance of the X-ray transmission power cable is calculated.

[0015] Furthermore, using the formula And the formula I = I0e -L The transmittance of the X-ray transmission power cable is calculated. Given the X-ray source intensity, the radius of the internal structural materials of the cable, and the attenuation coefficient, the X-ray intensity distribution within the high-voltage cable can be calculated using the above formula. This formula allows for the calculation and solution of the X-ray intensity at any point inside the cable. Where μ... i This represents the attenuation coefficient (cm) of each layer of the cable's internal structure. -1 ), x i This indicates the distance (in cm) that the line segment connecting the measured point and the X-ray source travels through each layer.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] 1. The technical solution provided by this invention uses a multi-frequency X-ray source in the experimental process. Multi-frequency X-ray sources are more widely used in actual production and life than single-frequency X-ray sources and have broad application prospects.

[0018] 2. The X-ray attenuation coefficients of XLPE, silicone rubber and semiconductive layer were measured for the first time, which is a pioneering achievement in this field.

[0019] 3. X-rays undergo hardening when penetrating materials of a certain thickness, resulting in an attenuation coefficient that is not a single constant. Due to the typical structure of power cables, multiple hardening phenomena can even occur when X-rays penetrate them. This invention fully considers this situation, and the calculation method used in this experiment is more accurate than traditional methods. Attached Figure Description

[0020] Figure 1 A schematic flowchart of a calculation method for X-ray intensity distribution in a power cable considering the X-ray attenuation coefficient of different materials, provided by the present invention;

[0021] Figure 2 A schematic diagram of an experiment involving X-ray source irradiation of a sample provided by the present invention;

[0022] Figure 3 This is a graph showing the relationship between the linear attenuation coefficient of the copper material of this invention and the sample thickness;

[0023] Figure 4 The linear attenuation coefficient of aluminum material versus sample thickness is provided for the present invention.

[0024] Figure 5 The linear attenuation coefficient of XLPE material versus sample thickness is provided in this invention.

[0025] Figure 6 A graph showing the relationship between the linear attenuation coefficient of the silicone rubber material and the sample thickness provided by the present invention;

[0026] Figure 7 The graph shows the relationship between the linear attenuation coefficient of the semiconductive layer material provided by this invention and the sample thickness. Detailed Implementation

[0027] The specific implementation of the present invention is described below with reference to embodiments:

[0028] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0029] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0030] Example 1:

[0031] This embodiment discloses a method for calculating the X-ray intensity distribution within a power cable considering the X-ray attenuation coefficients of different materials. First, a multi-frequency X-ray machine is used to apply X-ray irradiation to five power cable materials: copper, aluminum, XLPE, silicone rubber, and a semi-conductive layer. The initial X-ray dose rate and the dose rate after penetration are recorded. Second, the X-ray attenuation formula, I = I0e... -μx The transmittance, average attenuation coefficient, and average attenuation coefficient for each segment of different materials with varying thicknesses were calculated, and fitting formulas were derived. When the initial incident X-ray dose rate was approximately 7.2 mGy / s, five fitting formulas were obtained for the relationship between the X-ray attenuation coefficient and sample thickness for five materials: copper, aluminum, XLPE, PVC, and a semiconductive layer. The fitting formula for the X-ray attenuation coefficient of copper and sample thickness was y = 12.432x. -0.501 The fitting formula for the X-ray attenuation coefficient of aluminum with sample thickness is y = -1.889ln(x) + 5.2844, and the fitting formula for the X-ray attenuation coefficient of XLPE with sample thickness is y = -5 × 10 -5 x 2 The X-ray attenuation coefficient of PVC is -0.0073x + 0.8231, and the fitting formula for the sample thickness is y = -0.164ln(x) + 0.9777. The fitting formula for the X-ray attenuation coefficient of the semiconductive layer is y = 0.0055x. 2 -0.1527x + 1.2713. Where y represents the X-ray attenuation coefficient (cm²). -1), where x represents the sample thickness (mm). Finally, comparing the above experimental results with existing literature, it was found that as the penetration thickness increases, the average linear attenuation coefficient continuously decreases, and the amount of decrease gradually diminishes, eventually approaching a stable value. As the penetration thickness increases, the average linear attenuation coefficient of each segment continuously decreases and gradually approaches a stable value. This is because hardening occurs after continuous X-rays penetrate an object of a certain thickness. Due to the typical structure of power cables, multiple hardening even occurs when X-rays penetrate the power cable. Comparing the results of traditional methods with the calculation method of this invention, it can be found that using traditional attenuation coefficient calculations leads to significant errors due to the lack of measurement of the X-ray attenuation coefficient of materials transmitted by multi-frequency X-ray sources and the consideration of the multiple hardening phenomenon occurring when cable materials are irradiated by X-rays. This confirms that the calculation method in this experiment is more accurate than traditional methods.

[0032] Example 2:

[0033] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. This embodiment is a calculation method for an X-ray machine with an initial emission intensity of 0.3 MeV. Figure 1 The diagram shows a flowchart illustrating a method for calculating the X-ray intensity distribution within a power cable considering the X-ray attenuation coefficients of different materials, according to an embodiment of the present invention. The method includes:

[0034] Step 1: Before irradiating the sample with X-rays, conduct an experiment without the sample and measure its transmission dose rate as the initial dose rate. Then, arrange the experimental equipment and sample according to the experimental diagram, irradiate the experimental sample with an X-ray emitter, and measure its transmission dose rate.

[0035] In step 1, the specific process is as follows:

[0036] Before irradiating the sample with X-rays, conduct an experiment without the sample. Place the X-ray probe horizontally 10 cm in front of the X-ray emitter and emit X-rays with an initial energy of 0.3 MeV. Measure the transmitted dose rate as the initial dose rate. Then, arrange the experimental equipment and sample according to the experimental diagram. Irradiate the experimental sample with the X-ray emitter, placing the X-ray probe horizontally 10 cm in front of the X-ray emitter and emitting X-rays with an initial energy of 0.3 MeV. Measure the transmitted dose rate.

[0037] Step 2): Calculate the relationship between the transmittance and sample thickness of five power cable materials: copper, aluminum, XLPE, silicone rubber, and semiconductive layer. Obtain the corresponding experimental images, calculate the average line attenuation coefficient of the five samples and the average line attenuation coefficient of each segment, and plot the experimental images.

[0038] In step 2, the specific process is as follows:

[0039] Using data recorded by the X-ray measuring instrument probe, the relationship between the transmittance and sample thickness of five power cable materials—copper, aluminum, XLPE, silicone rubber, and semiconductive layer—was calculated, and corresponding experimental images were obtained. Based on the experimental data and images, it can be concluded that as the sample thickness increases, the transmitted dose rate continuously decreases, and the amount of decrease gradually diminishes, eventually leveling off. Using formula (1), the average linear attenuation coefficient of the five samples and the average linear attenuation coefficient of each segment were calculated, and experimental images were plotted. It was found that, based on the experimental data and images, it can be concluded that, as the penetration thickness increases, the average linear attenuation coefficient continuously decreases, and the amount of decrease gradually diminishes, gradually approaching a stable value. As the penetration thickness increases, the average linear attenuation coefficient of each segment continuously decreases and gradually approaches a stable value. This can be explained by the fact that after continuous X-ray transmission through an object of a certain thickness, a hardening phenomenon occurs.

[0040] I = I0e -μx (1)

[0041] Where I represents the intensity of transmitted X-rays, I0 represents the intensity of incident X-rays, and μ represents the attenuation coefficient (cm). -1 ), where x represents the thickness (cm) of the material through which the X-rays pass during transmission.

[0042] Step 3): Using the relationship between the X-ray attenuation coefficients of copper and aluminum and the sample thickness obtained in Steps 1 and 2, and comparing it with previous experimental results, the differences were found to be small, proving that the fitting formula for the X-ray attenuation coefficients of copper and aluminum and the sample thickness is: The fitting formula for the X-ray attenuation coefficient of copper and the sample thickness is y = 12.432x -0.501 The fitting formula for the X-ray attenuation coefficient of aluminum with respect to sample thickness is y = -1.889ln(x) + 5.2844, which holds true. The validity of the fitting formulas for the X-ray coefficients of copper and aluminum, to some extent, corroborates the correctness of the experimental results for XLPE, silicone rubber, and the semiconductive layer. Finally, the transmittance of the X-ray-transmitted power cable was calculated, and this method is more accurate than traditional calculation methods.

[0043] In step 3, the specific process is as follows:

[0044] By comparing the relationship between the X-ray attenuation coefficients of copper and aluminum and sample thickness obtained in steps 1 and 2 with previous experimental results, the differences were found to be minimal, proving that the fitting formulas for the X-ray attenuation coefficients of copper and aluminum with sample thickness are valid. The validity of the fitting formulas for the X-ray coefficients of copper and aluminum, to a certain extent, corroborates the correctness of the experimental results for XLPE, silicone rubber, and the semiconductive layer. Finally, the transmittance of the X-ray-transmitted power cable was calculated, and this method is more accurate than traditional calculation methods.

[0045] Using formula And the formula I = I0e -L The transmittance of the X-ray transmission power cable is calculated. Given the X-ray source intensity, the radius of the internal structural materials of the cable, and the attenuation coefficient, the X-ray intensity distribution within the high-voltage cable can be calculated using the above formula. This formula allows for the calculation and solution of the X-ray intensity at any point inside the cable. Where μ... i This represents the attenuation coefficient (cm) of each layer of the cable's internal structure. -1 ), x i This indicates the distance (in cm) that the line segment connecting the measured point and the X-ray source travels through each layer.

[0046] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0047] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A method for calculating the X-ray intensity distribution within a power cable, considering the X-ray attenuation coefficients of different materials, characterized in that... The method includes the following steps: Step S1: Obtain the initial dose rate, wherein the initial dose rate is the transmission dose rate under experimental conditions without a sample; Step S2: Obtain the secondary dose rate, wherein the secondary dose rate is the transmission dose rate under experimental conditions with the sample added; Step S3: Using the obtained initial dose rate and secondary dose rate, calculate the relationship between the transmittance and thickness of various power cable materials, the average linear attenuation coefficient of various power cable materials, and the average linear attenuation coefficient of each segment. Finally, obtain the relationship diagram of the average linear attenuation coefficient of various power cable materials under different thickness conditions and the average linear attenuation coefficient of each segment. Step S4: Based on the aforementioned relationship diagram, determine the transmittance of the X-ray transmission power cable; Based on the aforementioned relationship diagram, considering the measurement of the X-ray attenuation coefficient of the multi-frequency X-ray source transmission material and the multiple hardening phenomenon that occurs when the cable material is irradiated by X-rays, the transmittance of the X-ray transmission power cable is calculated. Using formula and formula Calculate the transmittance of the X-ray transmission power cable; where, This represents the attenuation coefficient of each layer of the cable's internal structure. , This represents the distance traveled by the line segment connecting the measured point and the X-ray source in each layer. .

2. The method for calculating the X-ray intensity distribution within a power cable according to claim 1, characterized in that, The X-ray probe is placed horizontally 10 cm in front of the X-ray emitter, and its transmission dose rate is measured to obtain the initial dose rate. The experimental sample is irradiated with the X-ray emitter, and the X-ray probe is placed horizontally 10 cm in front of the X-ray emitter to measure its transmission dose rate to obtain the secondary dose rate.

3. The method for calculating the X-ray intensity distribution within a power cable according to claim 1, characterized in that, The secondary dose rate includes the transmission dose rate of five power cable materials: copper, aluminum, XLPE, silicone rubber, and semiconductive layer.

4. The method for calculating the X-ray intensity distribution within a power cable according to claim 1, characterized in that, Using formula Calculate the average line attenuation coefficient and the average line attenuation coefficient of each segment for various power cable materials; As the formula shows, X-rays will attenuate to a certain extent when passing through a homogeneous material. This attenuation phenomenon follows an exponential law, where... Indicates the intensity of transmitted X-rays. The intensity of the incident X-rays is represented by μ, and the attenuation coefficient is represented by μ. , where x represents the thickness of the material through which the X-ray passes during transmission (in cm).

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