A Detection Method for the Heat Source of Internal Faults in On-Vehicle Cable Terminals

Abstract

The present invention discloses a method for detecting the heat source of internal faults in vehicle-mounted cable terminals. First, according to the structural parameters of the vehicle-mounted cable terminal, the equivalent heat conduction coefficient of the single-layer equivalent structure of the vehicle-mounted cable terminal is obtained. Then, the filtered surface temperature distribution image of the vehicle-mounted cable terminal is obtained, and the one-dimensional curve temperature distribution at the highest temperature point is intercepted through infrared image processing software, and the main peak values of its second-order, fourth-order, and sixth-order differential distributions are obtained. Finally, through the equivalent heat conduction coefficient and the main peak value, the heat source intensity of the internal fault heat source is calculated. The present invention realizes the quantitative detection of the internal fault heat source of the vehicle-mounted cable terminal, and is a fast and accurate method for detecting the internal fault heat source of the vehicle-mounted cable terminal, which is beneficial to ensuring the safe and stable operation of the cable terminal.

Description

Technical Field

[0001] The present invention relates to the field of on-vehicle cable terminal fault analysis, and particularly to a method for detecting internal fault heat sources of on-vehicle cable terminals. Background Art

[0002] On-vehicle cable terminals are important components of the high-voltage system of high-speed trains. They are located at the head and end of on-vehicle high-voltage cables and are responsible for transmitting electrical energy from the power grid to the on-vehicle traction transformer. They are important "bridges" connecting on-vehicle high-voltage cables and electrical equipment. Their good service performance is a necessary condition for ensuring the safe and stable operation of high-speed trains.

[0003] However, the internal insulation structure of on-vehicle cable terminals is complex, adopting a multi-layer coating structure, with relatively serious internal electric field distortion. It is easily interfered by external factors such as construction technology, vehicle body vibration, and sudden changes in environmental temperature, resulting in insulation faults. It is a relatively weak link in the train high-voltage system. In recent years, with the development of society and the national economy, the running speed and traction power of trains have increased significantly, and the impact voltage on on-vehicle cable terminals has intensified, leading to the expansion and heating of internal insulation defects, thereby triggering cable terminal explosions and causing train accidents. Therefore, timely and accurately detecting the internal fault heat sources of on-vehicle cable terminals is the key to effectively preventing cable terminal faults and is of great significance for ensuring the safe and reliable operation of high-speed trains. Summary of the Invention

[0004] Aiming at the above deficiencies in the prior art, the method for detecting internal fault heat sources of on-vehicle cable terminals provided by the present invention realizes the quantitative detection of internal fault heat sources of on-vehicle cable terminals.

[0005] In order to achieve the above invention purpose, the technical solution adopted by the present invention is as follows:

[0006] Provide a method for detecting internal fault heat sources of on-vehicle cable terminals, which includes the following steps:

[0007] S1. Determine the radial thickness and thermal conductivity coefficient of each layer structure of the on-vehicle cable terminal according to the structural parameters of the on-vehicle cable terminal;

[0008] S2. Equivalent the on-vehicle cable terminal into a single-layer heat transfer model, and determine the equivalent thermal conductivity coefficient of the single-layer heat transfer model according to the radial thickness and thermal conductivity coefficient of each layer structure of the on-vehicle cable terminal;

[0009] S3. Obtain and filter the surface temperature distribution image of the on-vehicle cable terminal to obtain the filtered image;

[0010] S4. Obtain the one-dimensional curve temperature distribution in the filtered image, and calculate the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature;

[0011] S5. Extract the peak values of the main peaks of the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature, and determine the heat source intensity of the heat source of the in-vehicle cable terminal according to the equivalent thermal conductivity and the peak value of the main peak, thereby completing the detection of the internal fault heat source.

[0012] Further, in step S1, the structure of the in-vehicle cable terminal includes a cable core, an inner semiconductor layer, a main insulation layer, a stress control tube, an outer semiconductor layer, a heat shrinkable insulation tube, an outer shielding layer, a sheath layer, and umbrella skirts.

[0013] Further, the expression of the equivalent thermal conductivity of the single-layer heat transfer model in step S2 is:

[0014]

[0015] where is the equivalent thermal conductivity; , , , , , and are the radial thicknesses of the main insulation layer, stress control tube, outer semiconductor layer, heat shrinkable insulation tube, outer shielding layer, sheath layer, and umbrella skirts respectively; , , , , , and are the thermal conductivities of the main insulation layer, stress control tube, outer semiconductor layer, heat shrinkable insulation tube, outer shielding layer, sheath layer, and umbrella skirts respectively.

[0016] Further, the specific method of step S3 is:

[0017] Obtain the surface temperature distribution image of the in-vehicle cable terminal through an infrared thermal imager, and filter the surface temperature distribution image using a smoothing filter to obtain the filtered image.

[0018] Further, the specific method of step S4 is:

[0019] Select the horizontal line at the highest temperature point in the filtered image to obtain the one-dimensional curve temperature distribution, and obtain the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature.

[0020] Further, the specific method of step S5 is:

[0021] According to the formula:

[0022]

[0023] Obtain the heat source intensityQ ; wherein is the peak value of the main peak of the second-order differential distribution of the one-dimensional curve temperature; is the peak value of the main peak of the fourth-order differential distribution of the one-dimensional curve temperature; is the peak value of the main peak of the sixth-order differential distribution of the one-dimensional curve temperature; π is the pi; is the equivalent heat conduction coefficient.

[0024] The beneficial effects of the present invention are as follows: Firstly, according to the structural parameters of the on-vehicle cable terminal, the equivalent heat conduction coefficient of the single-layer equivalent structure of the on-vehicle cable terminal is obtained. Then, the filtered surface temperature distribution image of the on-vehicle cable terminal is obtained, and the one-dimensional curve temperature distribution at the highest temperature point is intercepted through infrared image processing software, and the peak values of the main peaks of its second-order, fourth-order, and sixth-order differential distributions are obtained. Finally, through the equivalent heat conduction coefficient and the peak values of the main peaks, the heat source intensity of the internal fault heat source is calculated. The present invention realizes the quantitative detection of the internal fault heat source of the on-vehicle cable terminal, and is a fast and accurate detection method for the internal fault heat source of the on-vehicle cable terminal, which is beneficial to ensuring the safe and stable operation of the cable terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the flow schematic diagram of this method;

[0026] Figure 2 is the schematic diagram of the construction process of the simplified equivalent model of the on-vehicle cable terminal containing a fault heat source provided by the embodiment of the present invention;

[0027] Figure 3 is the schematic diagram of the structure of the heat transfer model of the fault heat source provided by the embodiment of the present invention;

[0028] Figure 4 is the second-order, fourth-order, and sixth-order differential distribution diagrams of the curve temperature provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following describes the specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions made using the concept of the present invention are within the scope of protection.

[0030] As Figure 1 shown, the method for detecting the internal fault heat source of the on-vehicle cable terminal includes the following steps:

[0031] S1. According to the structural parameters of the on-vehicle cable terminal, determine the radial thickness and heat conduction coefficient of each layer of the on-vehicle cable terminal;

[0032] S2. Equivalent the on-vehicle cable terminal to a single-layer heat transfer model, and determine the equivalent thermal conductivity of the single-layer heat transfer model according to the radial thickness and thermal conductivity of each layer structure of the on-vehicle cable terminal;

[0033] S4. Obtain and filter the surface temperature distribution image of the on-vehicle cable terminal to obtain the filtered image;

[0034] S7. Obtain the one-dimensional curve temperature distribution in the filtered image through infrared image processing software, and calculate the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature;

[0035] S5. Extract the peak values of the main peaks of the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature, and determine the heat source intensity of the fault heat source of the on-vehicle cable terminal according to the equivalent thermal conductivity and the peak values of the main peaks, and complete the detection of the internal fault heat source.

[0036] The structure of the on-vehicle cable terminal in step S1 includes a cable core, an inner semiconductor layer, a main insulation layer, a stress control tube, an outer semiconductor layer, a heat shrinkable insulation tube, an outer shielding layer, a sheath layer, and umbrella skirts.

[0037] The expression of the equivalent thermal conductivity of the single-layer heat transfer model in step S2 is:

[0038]

[0039] Where is the equivalent thermal conductivity; , , , , , and are the radial thicknesses of the main insulation layer, stress control tube, outer semiconductor layer, heat shrinkable insulation tube, outer shielding layer, sheath layer, and umbrella skirts respectively; , , , , , and are the thermal conductivities of the main insulation layer, stress control tube, outer semiconductor layer, heat shrinkable insulation tube, outer shielding layer, sheath layer, and umbrella skirts respectively.

[0040] The specific method of step S3 is: obtain the surface temperature distribution image of the on-vehicle cable terminal through an infrared thermal imager, and filter the surface temperature distribution image with a smoothing filter to obtain the filtered image.

[0041] The specific method of step S4 is as follows: select the horizontal line at the highest temperature point in the filtered image to obtain the one-dimensional curve temperature distribution, and calculate the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature.

[0042] The specific method of step S5 is as follows: according to the formula:

[0043]

[0044] Obtain the heat source intensity Q ; where is the peak value of the main peak of the second-order differential distribution of the one-dimensional curve temperature; is the peak value of the main peak of the fourth-order differential distribution of the one-dimensional curve temperature; is the peak value of the main peak of the sixth-order differential distribution of the one-dimensional curve temperature; π is the pi; is the equivalent heat conduction coefficient.

[0045] In an embodiment of the present invention, as Figure 2 (a), Figure 2 (b), Figure 2 (c) and Figure 2 (d) shown, according to the structural characteristics of the on-vehicle cable terminal, simplify the multi-layer coating structure into a multi-layer column model, determine the radial thickness and thermal conductivity of each layer in the multi-layer column model, and the specific values are shown in Table 1.

[0046] Table 1: Physical properties of each layer structure

[0047]

[0048] According to Table 1, the thickness of the equivalent single-layer column model is 0.31 m, and the single-layer equivalent thermal conductivity is 0.421. As Figure 3 shown, taking the single-layer column equivalent model as an example, the fault heat source is located at the origin O where, and its heating intensity is Q , the distance to the model surface is h , and the model equivalent thermal conductivity is . According to the heat conduction theory, the temperature expression of point P on the model surface is:

[0049]

[0050] where r represents the distance from point P on the model surface to the origin.

[0051] In the rectangular coordinate system, the surface temperature expression is:

[0052]

[0053] For the surface xThe tangent temperature of =0, construct the function f ( z ):

[0054]

[0055] f ( z ) The second-order, fourth-order, and sixth-order differential functions are:

[0056]

[0057] Where is the second-order differential distribution function; is the fourth-order differential distribution function; is the sixth-order differential distribution function; z is the position of the main peak value, that is, the abscissa value of the heat source. When the heat source is at the origin, z takes the value of 0.

[0058] Let the heat source intensity Q be 2W, the equivalent thermal conductivity λ e be 0.421, the heat source depth h be 0.31m, the surface x =0 tangent temperature differential function curve is shown in Figure 4 . Where F 2, F 4, F 6 are the main peak values of the second-order, fourth-order, and sixth-order differential function curves respectively, and are located at z =0, then there is:

[0059]

[0060] From this, it can be obtained that:

[0061]

[0062] Furthermore, the internal heat source intensity can be obtained through the formula .

[0063] To sum up, the present invention first obtains the equivalent thermal conductivity of the single-layer equivalent structure of the on-vehicle cable terminal according to the structural parameters of the on-vehicle cable terminal, then obtains the filtered surface temperature distribution image of the on-vehicle cable terminal, intercepts the one-dimensional curve temperature distribution at the highest temperature point through infrared image processing software, and obtains the main peak values of its second-order, fourth-order, and sixth-order differential distributions. Finally, through the equivalent thermal conductivity and the main peak values, the heat source intensity of the internal fault heat source is calculated. The present invention realizes the quantitative detection of the internal fault heat source of the on-vehicle cable terminal, which is beneficial to ensuring the safe and stable operation of the cable terminal.

Claims

1. A method for detecting the heat source of internal faults in vehicle-mounted cable terminals, characterized in that, Including the following steps: S1. Determine the radial thickness and thermal conductivity of each layer structure of the vehicle-mounted cable terminal according to the structural parameters of the vehicle-mounted cable terminal; S2. Equivalent the vehicle-mounted cable terminal into a single-layer heat transfer model, and determine the equivalent thermal conductivity of the single-layer heat transfer model according to the radial thickness and thermal conductivity of each layer structure of the vehicle-mounted cable terminal; S3. Obtain and filter the surface temperature distribution image of the vehicle-mounted cable terminal to obtain the filtered image; S4. Select the horizontal line at the highest temperature point in the filtered image to obtain a one-dimensional curve temperature distribution, and obtain the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature; S5. Extract the peak values of the main peaks of the second-order differential distribution, fourth-order differential distribution, and sixth-order differential distribution of the one-dimensional curve temperature, and determine the heat source intensity of the fault heat source of the vehicle-mounted cable terminal according to the equivalent thermal conductivity and the peak values of the main peaks, and complete the detection of the internal fault heat source; The specific method of step S5 is as follows: According to the formula: Obtain the heat source intensity Q ; where is the peak value of the main peak of the second-order differential distribution of the one-dimensional curve temperature; is the peak value of the main peak of the fourth-order differential distribution of the one-dimensional curve temperature; is the peak value of the main peak of the sixth-order differential distribution of the one-dimensional curve temperature; π is the pi; is the equivalent heat conduction coefficient.

2. The method for detecting the heat source of internal faults in vehicle-mounted cable terminals according to claim 1, characterized in that, The structure of the vehicle-mounted cable terminal in step S1 includes a cable core, an inner semiconductor layer, a main insulation layer, a stress control tube, an outer semiconductor layer, a heat shrinkable insulation tube, an outer shielding layer, a sheath layer, and an umbrella skirt.

3. The method for detecting the heat source of internal faults in vehicle-mounted cable terminals according to claim 2, characterized in that, The expression of the equivalent thermal conductivity of the single-layer heat transfer model in step S2 is: Among them is the equivalent thermal conductivity coefficient; , , , , , and are the radial thicknesses of the main insulation layer, the controllable tube, the outer semiconductor layer, the heat-shrinkable insulation tube, the outer shield layer, the sheath layer, and the petticoat respectively; , , , , , and are the thermal conductivity coefficients of the main insulation layer, the controllable tube, the outer semiconductor layer, the heat-shrinkable insulation tube, the outer shield layer, the sheath layer, and the petticoat respectively.

4. The method for detecting the heat source of internal faults in vehicle-mounted cable terminals according to claim 1, characterized in that, The specific method of step S3 is as follows: Obtain the surface temperature distribution image of the vehicle-mounted cable terminal through an infrared thermal imager, and filter the surface temperature distribution image with a smoothing filter to obtain the filtered image.

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