External Measuring Device and Method for Interface Pressure Sensor of Rubber Insulation of Cable Accessories

Abstract

An external measurement device and method for the interface pressure sensor of a cable accessory rubber insulation. The measurement device includes a tension rod and a specimen holder arranged parallel to the tension rod. A cable accessory specimen to be measured is connected between the bottom of the specimen holder and the bottom of the tension rod. The stretching degree of the cable accessory specimen is adjusted through the tension rod, so as to simulate the expansion state of the cable accessory specimens with different expansion ratios. A measurement platform is arranged at the top of the specimen holder, and a piezoresistive thin film sensor is arranged on the measurement platform. A pressure conduction platform is installed above the measurement platform through the tension rod, and the interface pressure generated after the cable accessory specimen is stretched by the pressure conduction platform is loaded onto the piezoresistive thin film sensor through a column. In the present invention, the measurement sensor is separated from the cable accessory, and there is no need to install a sensor inside the rubber insulation interface of the cable accessory, which can well simulate the tightly fitting state of the cable and accessory interface, making the research on the interface pressure more convenient and meeting the measurement requirements under different temperature or variable temperature conditions.

Description

Technical Field

[0001] The present invention relates to the field of interface pressure measurement of rubber main insulation cable accessories, and particularly relates to an external measurement device and method for the interface pressure sensor of the rubber insulation of cable accessories. Background Art

[0002] The interface pressure between the cable and the accessory is the key to ensuring the long-term reliable operation of the cable accessory. To study the interface pressure of the rubber main insulation cable accessory, the primary goal is to achieve the measurement of the interface pressure.

[0003] So far, the measurement methods for the interface pressure between the cable and the accessory are all off-line measurements with a piezoelectric sensor built-in between the cable body and the cable accessory. However, the rubber insulation of the accessory will be affected by temperature during use and gradually undergo stress relaxation. Therefore, the off-line surface pressure measurement method cannot reflect the actual operating state of the cable accessory. In addition, to correct the performance changes of the pressure sensor at different temperatures and the errors brought to the pressure measurement, when measuring the accessory surface pressure at different temperatures, the sensor needs to be calibrated at different temperatures. Due to the influence of time drift and temperature drift, errors will inevitably occur. Especially when trying to measure the surface pressure under variable temperature conditions, for the traditional built-in sensor measurement method, the calibration of the sensor is very cumbersome, and due to the variable temperature effect, even if it is recalibrated, the error will be large due to the influence of temperature drift, and it cannot accurately reflect the change law of the surface pressure of the cable accessory under variable temperature conditions. Summary of the Invention

[0004] The purpose of the present invention is to address the above problems in the prior art and provide an external measurement device and method for the interface pressure sensor of the rubber insulation of cable accessories. The measurement sensor is separated from the cable accessory, and there is no need to build a sensor in the rubber insulation interface of the cable accessory, which can well simulate the tightly fitting state of the cable and the accessory interface, making the research on the interface pressure of the rubber insulation of the cable accessory more convenient and meeting the measurement requirements of the interface pressure of the rubber main insulation cable accessory sample under different temperatures or variable temperature conditions.

[0005] To achieve the above purpose, the present invention has the following technical solutions:

[0006] An external measurement device for the interface pressure sensor of the rubber insulation of cable accessories includes a tension rod and a specimen holder arranged parallel to the tension rod. A cable accessory specimen to be measured is connected between the bottom of the specimen holder and the bottom of the tension rod. The stretching degree of the cable accessory specimen is adjusted by the tension rod to simulate the expansion state of the cable accessory specimen with different expansion ratios. A measurement platform is arranged at the top of the specimen holder, and a piezoresistive thin film sensor is arranged on the measurement platform. A pressure conduction platform is installed above the measurement platform through the tension rod, and the interface pressure generated after the cable accessory specimen is stretched by the pressure conduction platform through a column is loaded onto the piezoresistive thin film sensor.

[0007] In a preferred embodiment, two tension rods are arranged in parallel, a specimen holder is arranged in parallel between the two tension rods, a semi-cylindrical guide post is installed at the bottom of the specimen holder, and both ends of the cable accessory specimen to be measured are respectively connected to the bottoms of the two tension rods, and the middle part is in contact with the semi-cylindrical guide post surface.

[0008] In a preferred embodiment, clamps are arranged at the bottoms of the two tension rods, and both ends of the cable accessory specimen to be measured are fixed to the clamps by bolts and nuts.

[0009] In a preferred embodiment, the two tension rods and the specimen holder are both screw rods, and the distance between the semi-cylindrical guide post and the clamp is adjusted by nuts to adjust the stretching degree of the cable accessory specimen.

[0010] In a preferred embodiment, gaskets are installed on both of the two tension rods above the pressure conduction platform by nuts. After the cable accessory specimen is stretched, the pressure of the cable accessory specimen received by the semi-cylindrical guide post is conducted and loaded on the gaskets through the tension rods, and the pressure received by the gaskets acts on the pressure conduction platform.

[0011] In a preferred embodiment, the semi-cylindrical guide post is fixed on the guide post bottom plate, the guide post bottom plate is fixed at the bottom ends of the two tension rods, and a notch for the cable accessory specimen to pass through is formed in the clamp facing the two tension rods, and the arc surface of the semi-cylindrical guide post is connected to the two notches on the guide post bottom plate.

[0012] In a preferred embodiment, a plurality of support platforms are installed at intervals on the specimen holder. The pressure conduction platform, the measurement platform, the support platforms and the guide post bottom plate are all circular, and the radii of the pressure conduction platform, the measurement platform and the support platforms are equal. The radius of the guide post bottom plate is not greater than the radii of the pressure conduction platform, the measurement platform and the support platforms, and notches for the two tension rods to pass through are formed in the pressure conduction platform, the measurement platform and the support platforms.

[0013] In a preferred embodiment, the parts of the tension rods and the specimen holder connected to the cable accessory specimen are placed in a programmable constant temperature and humidity test chamber.

[0014] A measuring method for the external measuring device of the cable accessory rubber insulation interface pressure sensor includes the following steps:

[0015] Cut the cable accessory specimen to be measured into a long strip with parallel sides, and connect it between the bottom of the specimen holder and the bottom of the tension rod;

[0016] Adjust the tension rod to stretch the cable accessory specimen to be measured to the required expansion rate;

[0017] Install the calibrated piezoresistive thin-film sensor under the column;

[0018] Place the part of the cable accessory sample of the tension rod and the connecting cable into the oven;

[0019] Set the oven temperature and maintain it for a set time, set the change end temperature and the temperature change rate, and continue to measure at a constant temperature at the change end temperature for a set duration;

[0020] Record the change in surface pressure of the cable accessory sample, calculate the relaxation rate, and obtain the relationship curve between the surface pressure relaxation rate and time.

[0021] In a preferred embodiment, the relaxation rate is calculated according to the following formula:

[0022]

[0023] In the formula: R′ is the relaxation rate; f′0 is the pressure at the initial moment of the test; f′ t is the pressure measured at time t during the period specified in the test.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] The external measurement device of the cable accessory rubber insulation interface pressure sensor of the present invention can well simulate the tightly fitting state of the cable and the accessory by simulating the structure of the actual cable and the accessory being tightly fitted, without the need to install a sensor inside the interface. When measuring the surface pressure at different temperatures or under variable temperature, since the sensor is in a separated state from the simulated accessory interface, only the part of the simulated interface needs to be placed in the required temperature environment, and the part where the sensor is placed remains at room temperature, without the need to re-calibrate the sensor at different temperatures. Since the part simulating the cable and accessory interface can always be in the oven and the piezoresistive thin-film sensor is outside the oven, it is beneficial to simulate the surface pressure at the cable and accessory interface during temperature change in the laboratory and study the variation law of the surface pressure with temperature. Compared with the traditional method of installing a sensor inside, the measurement method of the present invention is simple and easy to operate.

[0026] Furthermore, a semi-cylindrical guide post is installed at the bottom of the sample holder of the present invention. Both ends of the cable accessory sample to be measured are respectively connected to the bottom of two tension rods, and the middle part is in surface contact with the semi-cylindrical guide post. By replacing the semi-cylindrical guide posts with different radii, the expansion states of cable accessories with different inner diameters can be simulated. Description of the Drawings

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 Schematic structural diagram of the external measurement device for the rubber insulation interface pressure sensor of the cable accessory of the present invention;

[0029] Figure 2 Schematic structural diagram of the bottom of the specimen holder of the measurement device of the present invention;

[0030] Figure 3 Schematic structural diagram of the top of the tension rod of the measurement device of the present invention;

[0031] In the accompanying drawings: 101 - support platform; 102 - specimen holder; 103 - tension rod; 104 - measurement platform; 201 - semi-cylindrical guide post; 202 - fixture; 301 - gasket; 302 - column; 303 - piezoresistive thin film sensor. Detailed implementation manners

[0032] The present invention will be further described in detail below with reference to the accompanying drawings.

[0033] See Figures 1-3, an external measurement device for the rubber insulation interface pressure sensor of the cable accessory in the embodiment of the present invention includes a tension rod 103 and a specimen holder 102 arranged parallel to the tension rod 103. A cable accessory specimen to be measured is connected between the bottom of the specimen holder 102 and the bottom of the tension rod 103. There are two tension rods 103 arranged in parallel, and there are also two specimen holders 102 arranged in parallel. The two specimen holders 102 are arranged in parallel between the two tension rods 103, forming a cross-shaped structure. A semi-cylindrical guide post 201 is installed at the bottom of the specimen holder 102. The two ends of the cable accessory specimen to be measured are respectively connected to the bottoms of the two tension rods 103, and the middle part is in surface contact with the semi-cylindrical guide post 201. Clamps 202 are provided at the bottoms of the two tension rods 103, and the two ends of the cable accessory specimen to be measured are fixed to the clamps 202 by bolts and nuts. The two tension rods 103 and the specimen holder 102 are both screw rods. The distance between the semi-cylindrical guide post 201 and the clamp 202 is adjusted by nuts to adjust the stretching degree of the cable accessory specimen, so as to simulate the expansion state of the cable accessory specimen with different expansion ratios; a measurement platform 104 is provided at the top of the specimen holder 102, and a piezoresistive thin film sensor 303 is provided on the measurement platform 104. A pressure conduction platform is installed above the measurement platform 104 through the tension rod 103. Gaskets 301 are installed on the two tension rods 103 above the pressure conduction platform through nuts. After the cable accessory specimen is stretched, the pressure of the cable accessory specimen received by the semi-cylindrical guide post 201 is conducted and loaded on the gasket 301 through the tension rod 103. The pressure received by the gasket 301 acts on the pressure conduction platform, and the pressure conduction platform loads the interface pressure generated after the cable accessory specimen is stretched onto the piezoresistive thin film sensor 303 through the column 302.

[0034] In this embodiment, the semi-cylindrical guide post 201 is fixed on the guide post bottom plate, the guide post bottom plate is fixed at the bottom ends of the two tension rods 103, and a notch for the cable accessory specimen to pass through is provided in the clamp 202 facing the two tension rods 103. The arc surface of the semi-cylindrical guide post 201 is connected to the two notches on the guide post bottom plate.

[0035] On the other hand, a plurality of support platforms 101 are installed at intervals on the specimen holder 102. The pressure conduction platform, the measurement platform 104, the support platform 101 and the guide post bottom plate are all circular, and the radii of the pressure conduction platform, the measurement platform 104 and the support platform 101 are equal. The radius of the guide post bottom plate is not greater than the radii of the pressure conduction platform, the measurement platform 104 and the support platform 101. The pressure conduction platform, the measurement platform 104 and the support platform 101 are provided with notches for the two tension rods 103 to pass through.

[0036] The parts of the tension rod 103 and the specimen holder 102 connected to the cable accessory specimen can be placed in a programmable constant temperature and humidity test chamber.

[0037] In the structure of the external measurement device for the rubber insulation interface pressure sensor of the cable accessory of the present invention described above:

[0038] The function of the support platform 101 is to support the overall measurement device in the oven hole when the measurement device passes through the oven wall. At the same time, in cooperation with some heat insulation materials, it can also play a role in sealing the box body and blocking heat dissipation.

[0039] The specimen holder 102 is used to support the cable accessory specimen and simulate the expansion state of the cable accessory. The semi-cylindrical guide post 201 can be replaced with different radii to simulate the expansion states of cable accessories with different inner diameters.

[0040] There are two tension rods 103 in total. Their function is to stretch the cable accessory specimen and conduct the tensile force of the specimen. Different expansion states of cable accessories with different expansion ratios can be simulated by different stretching lengths. When in use, the end of the cable accessory specimen passes through the iron sheet by the clamp 202, and the end of the specimen is clamped by the cooperation of the screw and the nut to prevent the specimen from sliding and affecting the pressure measurement. The function of the gasket 301 is that after the specimen is stretched, the specimen pressure received on the semi-cylindrical guide post 201 is conducted and loaded on the gasket 301 through the tension rod 103. Different expansion states of cable accessories with different expansion ratios can be simulated by changing the stretching degree;

[0041] A piezoresistive thin film sensor 303 is arranged on the measurement platform 104. After the gasket 301 is subjected to pressure, the pressure is loaded on the piezoresistive thin film sensor 303 through the column 302, realizing the separation of the piezoresistive thin film sensor 303 from the measurement part, and the interface pressure of the rubber main insulation cable accessory specimen under different temperatures or variable temperature conditions can be simulated and measured.

[0042] Another embodiment of the present invention provides a measurement method for the external measurement device of the rubber insulation interface pressure sensor of the cable accessory:

[0043] 1. Cut the rubber main insulation cable accessory specimen into a long strip with parallel sides. Use a programmable constant temperature and humidity test chamber as a test instrument to simulate environmental temperature changes, and use a thin film pressure sensor for pressure testing;

[0044] II. Since there are issues with the factory inconsistency of piezoresistive thin-film sensors, calibration is required before use. Calibration is carried out using a dedicated calibration table, a thin-film pressure test system, and upper computer software. The calibration table consists of a screw operating rod, a pointer-type push-pull force gauge (range 200N, graduation value 1N), a loading head, and a calibration backing plate. By operating the screw operating rod, pressure can be applied to the sensor, and the pointer-type force gauge can display the applied pressure value in real-time. To avoid the influence of temperature on the piezoresistive thin-film resistance value, calibration is carried out at room temperature. Place the piezoresistive thin-film sensor on the calibration table, apply pressure to the sensor, starting from 0N. After applying the pressure, record the voltage value displayed after the upper computer software stabilizes. Then, continuously apply force at a certain interval and record the voltage value after stabilization until the pressure reaches the required range. Through data acquisition and fitting, the calibration is completed;

[0045] III. Clamp both sides of the long strip-shaped specimen with fixture 202, and make the wide parallel surface fit on the semi-cylindrical guiding column 201 of the simulated cable. Adjust the tension rod 103 to stretch the specimen to the required expansion rate to complete the installation of the specimen on the simulated measurement surface pressing device;

[0046] IV. Place the calibrated piezoresistive thin-film sensor 303 under the measuring side column 302 of the device. Then, place the entire measuring device on the oven. A part of the specimen rack 102 used to simulate the interface is inside the oven, while the measuring platform 104 on the side where the piezoresistive thin-film sensor 303 is placed remains outside the oven. Support the entire device through the support platform 101 in the oven hole;

[0047] V. Set the oven temperature and maintain it for a specified time. Then, set the changed temperature and the temperature change rate, and continue the constant-temperature measurement at this temperature for a specified duration.

[0048] VI. After the measurement, to more clearly represent the law of surface pressure change, divide the amount of surface pressure change by the surface pressure at the initial moment, and call it the relaxation rate, denoted as R′. Calculate it according to the following formula, and then plot the relationship curve between the surface pressure relaxation rate and time.

[0049]

[0050] In the formula: R′——relaxation rate / %; f′0——pressure at the initial moment of the test / N; f′ t ——pressure measured at time t during the specified period of the test / N.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included within the protection scope of the present application.

Claims

1. An external measurement device for the interface pressure sensor of the rubber insulation of a cable accessory, characterized in that: It includes a tension rod (103) and a specimen holder (102) arranged in parallel with the tension rod (103). A cable accessory specimen to be measured is connected between the bottom of the specimen holder (102) and the bottom of the tension rod (103). The tension degree of the cable accessory specimen is adjusted by the tension rod (103) to simulate the expansion state of cable accessory specimens with different expansion ratios. A measurement platform (104) is provided at the top of the specimen holder (102), and a piezoresistive thin film sensor (303) is arranged on the measurement platform (104). Above the measurement platform (104), a pressure conduction platform is installed through the tension rod (103). The interface pressure generated after the cable accessory specimen is stretched by the pressure conduction platform is loaded onto the piezoresistive thin film sensor (303) through a column (302). Two tension rods (103) are arranged in parallel, and the specimen holder (102) is arranged in parallel between the two tension rods (103). A semi-cylindrical guide post (201) is installed at the bottom of the specimen holder (102). The two ends of the cable accessory specimen to be measured are respectively connected to the bottoms of the two tension rods (103), and the middle part is in surface contact with the semi-cylindrical guide post (201). The two tension rods (103) and the specimen holder (102) are both screws, and the distance between the semi-cylindrical guide post (201) and the fixture (202) is adjusted by a nut to adjust the tension degree of the cable accessory specimen. Gaskets (301) are installed on the two tension rods (103) above the pressure conduction platform through nuts. After the cable accessory specimen is stretched, the pressure of the cable accessory specimen received by the semi-cylindrical guide post (201) is conducted and loaded onto the gasket (301) through the tension rod (103), and the pressure received by the gasket (301) acts on the pressure conduction platform.

2. The external measurement device for the rubber insulation interface pressure sensor of the cable accessory according to claim 1, wherein: Fixtures (202) are provided at the bottoms of the two tension rods (103), and the two ends of the cable accessory specimen to be measured are fixed to the fixtures (202) by bolts and nuts.

3. The external measurement device for the rubber insulation interface pressure sensor of the cable accessory according to claim 2, characterized in that: The semi-cylindrical guide post (201) is fixed on a guide post bottom plate. The guide post bottom plate is fixed at the bottom ends of the two tension rods (103) and is provided with a notch for the cable accessory specimen to pass through opposite to the fixtures (202) of the two tension rods (103). The arc surface of the semi-cylindrical guide post (201) connects the two notches on the guide post bottom plate.

4. The external measurement device for the rubber insulation interface pressure sensor of the cable accessory according to claim 3, characterized in that: A plurality of support platforms (101) are installed at intervals on the specimen holder (102). The pressure conduction platform, the measurement platform (104), the support platforms (101) and the guide post bottom plate are all circular. The radii of the pressure conduction platform, the measurement platform (104) and the support platforms (101) are equal, and the radius of the guide post bottom plate is not greater than the radii of the pressure conduction platform, the measurement platform (104) and the support platforms (101). The pressure conduction platform, the measurement platform (104) and the support platforms (101) are provided with notches for the two tension rods (103) to pass through.

5. The external measurement device for the cable accessory rubber insulation interface pressure sensor according to claim 3, wherein: The parts of the tension rod (103) and the specimen holder (102) connected to the cable accessory specimen are placed in a programmable constant temperature and humidity test chamber.

6. A measuring method for an external measuring device of a cable accessory rubber insulation interface pressure sensor as described in any one of claims 1-5, characterized in that, It includes the following steps: Cut the cable accessory sample to be measured into a long strip with parallel sides, and connect it between the bottom of the sample holder (102) and the bottom of the tension rod (103); Adjust the tension rod (103) to stretch the cable accessory sample to be measured to the required expansion rate; Install the calibrated piezoresistive film sensor (303) under the column (302); Place the part of the tension rod (103) and the sample holder (102) connected to the cable accessory sample into the oven; Set the oven temperature and maintain it for the set time, set the change end temperature and the temperature change rate, and continue to measure at a constant temperature at the change end temperature for the set duration; Record the surface pressure change of the cable accessory sample, calculate the relaxation rate, and obtain the relationship curve between the surface pressure relaxation rate and time.

7. The measuring method according to claim 6, characterized in that, The relaxation rate is calculated according to the following formula: Where: is the relaxation rate; is the pressure at the initial moment of the test; is the pressure measured at the moment t within the specified period t of the test.

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