A DC resistance measuring device for large cross-section cable conductors

Abstract

This invention discloses a DC resistance measuring device for a large cross-section cable conductor, comprising: a first connecting clamp and a second connecting clamp respectively connected to both ends of the cable conductor, and respectively connected to both ends of a DC power supply via connecting cables; a first voltage measuring terminal and a second voltage measuring terminal respectively disposed at two predetermined positions on the cable conductor, with a sampling distance between the two predetermined positions not less than a preset threshold; a current sensor connected to the connecting cable for reducing the loop current of the measurement circuit by a preset ratio and outputting a reduced current; a high-precision current acquisition card connected to the current sensor for measuring the reduced current output by the current sensor; and a multi-channel high-precision voltage acquisition card for acquiring voltage data between the first voltage measuring terminal and the second voltage measuring terminal, wherein the reduced current, voltage data, and sampling distance are used to calculate the DC resistance value of the cable conductor.

Description

Technical Field

[0001] This invention relates to the field of cable conductor measurement technology, and in particular to a DC resistance measuring device for large cross-section cable conductors. Background Technology

[0002] DC resistance, as a crucial parameter of cable conductors, directly affects the current carrying capacity and transmission loss of power cable lines. Therefore, DC resistance is also a key testing item for assessing the qualification of cables during type testing and incoming inspection.

[0003] The conventional method for measuring the DC resistance of cable conductors is the bridge method. However, for large-section cable conductors, the double-arm bridge method suffers from low measurement accuracy and unstable results. The DC resistance per unit length of large-section cable conductors is extremely small, for example, 2500 mm². 2 The DC resistance of the copper core cable conductor is approximately 7.2 ohms. The conventional method for measuring the DC resistance of cable conductors using the bridge method has the following problems: the measurement accuracy is not high, only at the milliohm level, making it unsuitable for measuring the DC resistance of large-section cable conductors; the small contact area and low contact pressure between the conductor sample and the connecting clamp result in unstable measurement data. Therefore, it is difficult to achieve accurate measurement of the DC resistance of large-section cable conductors. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a DC resistance measuring device for large cross-section cable conductors.

[0005] According to one aspect of the present invention, a DC resistance measuring device for a large cross-section cable conductor is provided, comprising: a DC power supply, a cable conductor, a connecting cable, a first connecting clamp, a second connecting clamp, a first voltage measuring terminal, a second voltage measuring terminal, a current sensor, a multi-channel high-precision voltage acquisition card, and a high-precision current acquisition card, wherein...

[0006] The first and second connecting clamps are respectively connected to the two ends of the cable conductor and connected to the two ends of the DC power supply via connecting cables to form a measurement circuit. The first and second voltage measuring terminals are respectively set at two predetermined positions on the cable conductor, and the sampling distance between the two predetermined positions is not less than a preset threshold. The current sensor is connected to the connecting cable to reduce the loop current of the measurement circuit by a preset ratio and output a reduced current. The high-precision current acquisition card is connected to the current sensor to measure the reduced current output by the current sensor. The multi-channel high-precision voltage acquisition card is used to acquire the voltage data between the first and second voltage measuring terminals, wherein the reduced current, voltage data, and sampling distance are used to calculate the DC resistance value of the cable conductor.

[0007] Optionally, the DC resistance measuring device for large cross-section cable conductors also includes a temperature acquisition device for acquiring ambient temperature data of the measurement circuit.

[0008] Optionally, the DC resistance measuring device for large cross-section cable conductors further includes a data processing unit, which is connected to a multi-channel high-precision voltage acquisition card, a high-precision current acquisition card, and a temperature acquisition device via a signal transmission line. The data processing unit is used to calculate the DC resistance value of the cable conductor based on the received reduced current, preset ratio, voltage data, sampling distance, and ambient temperature data.

[0009] Optionally, the cable conductor is a test sample that has been straightened and the cross-sections at both ends have been ground flat.

[0010] Optionally, the first connecting fixture and the second connecting fixture are formed by a combination of a hydraulic pressure fixture and a probe contact fixture, wherein,

[0011] The hydraulic pressure clamp includes an inner clamp, an outer clamp, and a hydraulic device. The inner diameter of the inner clamp is the same as the outer diameter of the cable conductor, and the outer diameter of the inner clamp is the same as the inner diameter of the outer clamp. After the cable conductor is connected to the inner clamp and the outer clamp, pressure is applied to the outer clamp through the hydraulic device.

[0012] The probe surface of the probe contact clamp contacts the cross-section of the cable conductor, and a connecting mechanism is used to connect the probe contact clamp to the outer clamp. The other end of the probe contact clamp is connected to the connecting cable.

[0013] Optionally, the pressure applied by the hydraulic device is not less than a first preset threshold.

[0014] Optionally, the current sensor is a 0.01-level high-precision current sensor, used to reduce the current of the measurement circuit to a reduced current according to a preset ratio, wherein the preset ratio is 200:1, and the measurement error of the current sensor is 0.01%.

[0015] Optionally, the multi-channel high-precision voltage acquisition card has a resolution of 24 bits, a sampling rate of 50 kS / s, and a measurement range of... 10V, accuracy 10ppm.

[0016] Optionally, the high-precision current acquisition card has a resolution of 24 bits, a sampling rate of 50 kS / s, a measurement range of 0~5A, and an accuracy of 10ppm.

[0017] Optionally, the data processing unit includes an industrial computer and a software system on the industrial computer, wherein the software system is used to calculate the DC resistance value of the cable conductor based on voltage data, reduced current, preset ratio, sampling distance and ambient temperature data.

[0018] Optionally, the formula for calculating the DC resistance value is:

[0019] R 20 = R T / [1+0.00393*( T -20)]

[0020] in,

[0021] R T =U / Il

[0022] In the formula, R T The sampling resistance value is the value of the measurement circuit at ambient temperature; T is the ambient temperature data of the measurement circuit; R20 is the DC resistance value of the cable conductor at 20℃; U is the voltage data; l Sampling distance; I For loop current I= I' / k , k For the preset ratio, I’ To reduce the current.

[0023] This invention employs a multi-channel high-precision voltage acquisition card, a current sensor, and a high-precision current acquisition card to improve the accuracy of conductor voltage and current measurements. The accuracy of micro-ohm DC resistance measurement is approximately 0.1%, making it suitable for measuring the DC resistance of large-section cable conductors. The high-current measurement method ensures good stability and consistent repeatability. By using the end-face injection current method and a high-pressure clamp to apply the test current to the cable sample, the current flowing through the conductor sample is uniform and stable, resulting in stable measurement data with minimal error. This invention solves the technical problem of the difficulty in accurately measuring the DC resistance of large-section cable conductors using conventional bridge methods.

[0024] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0025] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0026] Figure 1 This is a schematic diagram of a DC resistance measuring device for large cross-section cable conductors according to an embodiment of the present invention;

[0027] Figure 2This is a schematic diagram of the connection between a connecting clamp and a cable conductor according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of a hydraulic pressure clamp according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of a probe contact fixture according to an embodiment of the present invention. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] Figure 1 This is a schematic diagram of a DC resistance measuring device for large-section cable conductors according to an embodiment of the present invention. (Reference) Figure 1As shown, the DC resistance measuring device for large cross-section cable conductors includes: a DC power supply 1, a cable conductor 2, a connecting cable 3, a first connecting clamp 4, a second connecting clamp 5, a first voltage measuring terminal 6, a second voltage measuring terminal 7, a current sensor 8, a multi-channel high-precision voltage acquisition card 9, and a high-precision current acquisition card 10.

[0035] The first connecting clamp 4 and the second connecting clamp 5 are respectively connected to the two ends of the cable conductor 2, and are respectively connected to the two ends of the DC power supply 1 through the connecting cable 3 to form a measurement circuit; the first voltage measuring terminal 6 and the second voltage measuring terminal 7 are respectively set at two predetermined positions of the cable conductor 2, and the sampling distance between the two predetermined positions is not less than a preset threshold; the current sensor 8 is connected to the connecting cable 3 to reduce the loop current of the measurement circuit by a preset ratio and output a reduced current; the high-precision current acquisition card 10 is connected to the current sensor 8 to measure the reduced current output by the current sensor 8; the multi-channel high-precision voltage acquisition card 9 is used to acquire the voltage data between the first voltage measuring terminal 6 and the second voltage measuring terminal 7, wherein the reduced current, voltage data and sampling distance are used to calculate the DC resistance value of the cable conductor 2.

[0036] Optionally, the DC resistance measuring device for large cross-section cable conductors also includes a temperature acquisition device for acquiring ambient temperature data of the measurement circuit.

[0037] Optionally, the DC resistance measuring device for large cross-section cable conductors further includes a data processing unit 12, wherein the data processing unit 12 is connected to a multi-channel high-precision voltage acquisition card 9, a high-precision current acquisition card 10, and a temperature acquisition device via a signal transmission line 11, and is used to calculate the DC resistance value of the cable conductor 2 based on the received reduced current, preset ratio, voltage data, sampling distance, and ambient temperature data.

[0038] Optionally, the cable conductor 2 is a test sample that has been straightened and has its ends ground flat.

[0039] Specifically, cable conductor 2 is the test sample, with a length of not less than 2.5m. It should be straightened before testing, and the cross-sections of the conductors at both ends of the cable should be ground flat.

[0040] Optionally, refer to Figure 2 , Figure 3 and Figure 4 As shown, the first connecting clamp 4 and the second connecting clamp 5 are formed by combining a hydraulic pressure clamp and a probe contact clamp 13, wherein,

[0041] refer to Figure 2 and Figure 3As shown, the hydraulic pressure clamp includes an inner clamp 14, an outer clamp 15, and a hydraulic device 16. The inner diameter of the inner clamp 14 is the same as the outer diameter of the cable conductor 2, and the outer diameter of the inner clamp 14 is the same as the inner diameter of the outer clamp 15. After the cable conductor 2 is connected to the inner clamp 14 and the outer clamp 15, pressure is applied to the outer clamp 15 through the hydraulic device 16.

[0042] refer to Figure 2 and Figure 4 As shown, the probe surface of the probe contact clamp 13 contacts the cross-section of the cable conductor 2, and the probe contact clamp 13 is connected to the outer clamp 15 by a connecting mechanism. The other end of the probe contact clamp 13 is connected to the connecting cable 3.

[0043] The connecting mechanism can be a fixing mechanism such as a screw.

[0044] Optionally, the pressure applied by the hydraulic device 16 is not less than a first preset threshold.

[0045] Optionally, the current sensor 8 is a 0.01-level high-precision current sensor, used to reduce the current of the measurement circuit to a reduced current according to a preset ratio, wherein the preset ratio is 200:1, and the measurement error of the current sensor 8 is 0.01%.

[0046] Optionally, the multi-channel high-precision voltage acquisition card 9 has a resolution of 24 bits, a sampling rate of 50 kS / s, and a measurement range of... 10V, accuracy 10ppm.

[0047] Optionally, the high-precision current acquisition card 10 has a resolution of 24 bits, a sampling rate of 50 kS / s, a measurement range of 0~5A, and an accuracy of 10ppm.

[0048] Optionally, the data processing unit 12 includes an industrial computer and a software system on the industrial computer, wherein the software system is used to calculate the DC resistance value of the cable conductor 2 based on voltage data, reduced current, preset ratio, sampling distance and ambient temperature data.

[0049] Optionally, the formula for calculating the DC resistance value is:

[0050] R 20 = R T / [1+0.00393*( T -20)]

[0051] in,

[0052] R T =U / Il

[0053] In the formula, R T The sampling resistance value is the value of the measurement circuit at ambient temperature; T is the ambient temperature data of the measurement circuit; R20 is the DC resistance value of the cable conductor at 20℃; U is the voltage data; l Sampling distance; I For loop current I= I' / k , k For the preset ratio, I’ To reduce the current.

[0054] Therefore, this invention employs a multi-channel high-precision voltage acquisition card, a current sensor, and a high-precision current acquisition card to improve the accuracy of conductor voltage and current measurements. The accuracy of micro-ohm DC resistance measurement is approximately 0.1%, making it suitable for measuring the DC resistance of large-section cable conductors. Large-section cable conductors have low resistance; for example, the DC resistance of a 2500mm² cross-section copper core cable conductor is 7.2 ohms per meter. This solution fully meets the measurement requirements. The high-current measurement method ensures good stability and consistent repeatability of the measurement results. The end-face injection current method and high-pressure clamps are used to apply the test current to the cable sample, resulting in a uniform and stable current flowing through the conductor sample. Therefore, the measurement data is stable with minimal error.

[0055] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0056] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0057] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0058] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A DC resistance measuring device for large cross-section cable conductors, characterized in that, include: DC power supply (1), cable conductor (2), connecting cable (3), first connecting clamp (4), second connecting clamp (5), first voltage measurement terminal (6), second voltage measurement terminal (7), current sensor (8), multi-channel high-precision voltage acquisition card (9), high-precision current acquisition card (10), wherein, The first connecting clamp (4) and the second connecting clamp (5) are respectively connected to the two ends of the cable conductor (2) and respectively connected to the two ends of the DC power supply (1) through the connecting cable (3) to form a measurement circuit; the first voltage measuring terminal (6) and the second voltage measuring terminal (7) are respectively set at two predetermined positions on the cable conductor (2) and the sampling distance at the two predetermined positions is not less than a preset threshold; the current sensor (8) is connected to the connecting cable (3) to reduce the loop current of the measurement circuit by a preset ratio and output a reduced current; the high-precision current acquisition card (10) is connected to the current sensor (8) to measure the reduced current output by the current sensor (8); the multi-channel high-precision voltage acquisition card (9) is used to acquire the voltage data between the first voltage measuring terminal (6) and the second voltage measuring terminal (7), wherein the reduced current, the voltage data and the sampling distance are used to calculate the DC resistance value of the cable conductor (2).

2. The DC resistance measuring device for large cross-section cable conductors according to claim 1, characterized in that, Also includes: A temperature acquisition device is used to acquire ambient temperature data of the measurement circuit.

3. The DC resistance measuring device for large cross-section cable conductors according to claim 2, characterized in that, Also includes: The data processing unit (12) is connected to the multi-channel high-precision voltage acquisition card (9), the high-precision current acquisition card (10) and the temperature acquisition device via a signal transmission line (11) to calculate the DC resistance value of the cable conductor (2) based on the received reduced current, the preset ratio, the voltage data, the sampling distance and the ambient temperature data.

4. The DC resistance measuring device for large cross-section cable conductors according to claim 1, characterized in that, The cable conductor (2) is a test sample, which has been straightened and the cross-sections at both ends have been polished flat.

5. The DC resistance measuring device for large cross-section cable conductors according to claim 1, characterized in that, The first connecting clamp (4) and the second connecting clamp (5) are formed by combining a hydraulic pressure clamp and a probe contact clamp (13), wherein, The hydraulic pressure clamp includes an inner clamp (14), an outer clamp (15), and a hydraulic device (16). The inner diameter of the inner clamp (14) is the same as the outer diameter of the cable conductor (2), and the outer diameter of the inner clamp (14) is the same as the inner diameter of the outer clamp (15). After the cable conductor (2) is connected to the inner clamp (14) and the outer clamp (15), pressure is applied to the outer clamp (15) through the hydraulic device (16). The probe surface of the probe contact clamp (13) contacts the cross section of the cable conductor (2), and the probe contact clamp (13) is connected to the outer clamp (15) by a connecting mechanism. The other end of the probe contact clamp (13) is connected to the connecting cable (3).

6. The DC resistance measuring device for large cross-section cable conductors according to claim 5, characterized in that, The pressure applied by the hydraulic device (16) is not less than the first preset threshold.

7. The DC resistance measuring device for large cross-section cable conductors according to claim 1, characterized in that, The current sensor (8) is a 0.01-level high-precision current sensor, used to reduce the current of the measurement circuit to the reduced current according to the preset ratio, wherein the preset ratio is 200:1, and the measurement error of the current sensor (8) is 0.01%.

8. The DC resistance measuring device for large cross-section cable conductors according to claim 1, characterized in that, The multi-channel high-precision voltage acquisition card (9) has a resolution of 24 bits, a sampling rate of 50 kS / s, and a measurement range of... 10V, accuracy 10ppm.

9. The DC resistance measuring device for large cross-section cable conductors according to claim 1, characterized in that, The high-precision current acquisition card (10) has a resolution of 24 bits, a sampling rate of 50 kS / s, a measurement range of 0~5A, and an accuracy of 10ppm.

10. The DC resistance measuring device for large cross-section cable conductors according to claim 3, characterized in that, The data processing unit (12) includes an industrial computer and a software system on the industrial computer, wherein the software system is used to calculate the DC resistance value of the cable conductor (2) based on the voltage data, the reduced current, the preset ratio, the sampling distance and the ambient temperature data.

11. The DC resistance measuring device for large cross-section cable conductors according to claim 10, characterized in that, The formula for calculating the DC resistance value is: R 20 = R T / [1+0.00393*( T -20)] in, R T =U / Il In the formula, R T The sampling resistance value is the value of the measurement circuit at ambient temperature; T is the ambient temperature data of the measurement circuit; R20 is the DC resistance value of the cable conductor at 20℃; U is the voltage data; l Sampling distance; I For loop current I=I' / k , k For the preset ratio, I’ To reduce the current.

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