Large-span current-carrying acceleration test device for continuous point durability evaluation

Abstract

The invention discloses a large-span current-carrying acceleration test device for evaluating the durability of a connection point, belongs to the technical field of mechanical detection, and is suitable for evaluating the durability of the connection point of a power transmission and distribution line under a wind-induced vibration and current-carrying heating coupling working condition. The device integrates a main body structure, a wire clamp test module, a driving module and a wire tensioning module, constructs a main wire longitudinal pre-tightening-auxiliary wire dragging force adjustment-sine reciprocating excitation three-field coupling integrated platform, realizes stepless adjustment of main wire tensioning force through a spring tightener, and outputs high-frequency sine excitation by adopting a cam and crank slide block combined mechanism. The auxiliary line dragging force and posture are accurately regulated and controlled in cooperation with an air cylinder, current carrying is synchronously connected, and multi-dimensional test data are collected. The defects that an existing device is insufficient in loading dimension, poor in parameter adjustability and low in working condition reduction degree are overcome, the repeatability of test results and the test efficiency are remarkably improved, and a reliable experiment basis is provided for connection point fatigue life evaluation, failure mechanism research and structure optimization.

Description

Technical Field

[0001] This invention relates to the field of mechanical testing technology, specifically to equipment for testing the splicing and fatigue life of power conductors, and more particularly to a vibration-accelerated fatigue failure test platform for conductor splicing points under high current-carrying conditions. It is suitable for evaluating the durability, life assessment, and failure mechanism research of splicing points in power transmission and distribution lines under the coupled conditions of wind-induced vibration, longitudinal tension, and current-carrying heating. Background Technology

[0002] The connection points formed by conductors and connectors (such as parallel groove clamps, crimped bushings, tension / suspension fittings, etc.) in power transmission and distribution lines are critical weak points for safe line operation. During long-term service, these connection points are simultaneously subjected to alternating external loads such as wind-induced vibration, ice shedding, operating load fluctuations, and environmental disturbances, making them highly susceptible to fretting—small-amplitude, high-frequency relative displacement at the nominal contact interface. Fretting can lead to interface wear, material spalling, plastic deformation, and seizing. Wear debris is repeatedly oxidized and embedded in the surface layer under electro-thermal coupling, resulting in increased contact resistance and degraded connection stiffness, ultimately inducing loosening, slippage, and the initiation and propagation of fatigue cracks.

[0003] For high-current-carrying connection points, wind-induced vibration, longitudinal pretension, and geometric angle constraints combine to form a radial shear / torsional shear composite friction condition. Simultaneously, the Joule heating generated by the current increases the interface temperature gradient, accelerating the oxidation wear cycle. When the contact resistance exceeds the threshold, localized heating may induce arcing and arc erosion, causing metal surface erosion and morphological deterioration, significantly weakening conductivity and load-bearing reliability. When combined with unconventional events such as lightning strikes or short-circuit impacts, this can easily trigger tripping and power outage risks.

[0004] To investigate the aforementioned failure mechanisms and evaluate the durability of the joint points, it is necessary to reconstruct the multi-field coupled operating condition of "longitudinal tension—lateral excitation—current-carrying heating" in a controllable and repeatable manner in the laboratory. However, existing experimental setups generally suffer from the following technical limitations: Insufficient loading dimensions: Most loads are unidirectional or two-dimensional, making it impossible to achieve the linkage loading of longitudinal pre-tightening of the main line, adjustment of drag force of the secondary line and sinusoidal reciprocating excitation within the same platform. It is difficult to fully restore the actual force boundary of the joint point, resulting in low working condition reproduction. Limited parameter window: Especially under high-frequency micro-motion and controlled small stroke conditions, the combined adjustability of excitation frequency, excitation force and stroke is insufficient and cannot cover the critical parameter range of connection point failure. Low tension adjustment accuracy: The tensioning method is mostly fixed gear or coarse adjustment mode, and the tension of the main line cannot be continuously adjusted, resulting in weak comparability and repeatability of test results between different working conditions. Lack of multi-field coupling coordination: Current-carrying heating and mechanical loading are mostly controlled independently, making it difficult to simulate the electro-thermal-mechanical coupling effect in actual service, and the experimental data deviates significantly from the actual service situation.

[0005] Therefore, there is an urgent need to develop a multi-field coupling accelerated testing device with high working condition reproduction, strong parameter controllability, and repeatable results to fill the gap in existing technology and provide reliable experimental support for the durability evaluation and structural optimization of the connection point. Summary of the Invention

[0006] This invention aims to address the shortcomings of existing experimental devices, such as insufficient loading dimensions, poor parameter adjustability, low operational condition reproduction, and lack of electro-thermal-mechanical coupling simulation.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A large-span current-carrying acceleration test device for evaluating the durability of splice points includes a main structure, a wire clamp test module, a drive module, a conductor tensioning module, and a current-carrying unit. These modules work together to achieve a three-field coupled loading and current-carrying acceleration test, consisting of longitudinal pre-tensioning of the main conductor, adjustment of the secondary conductor's drag force, and sinusoidal reciprocating excitation. The specific structure is as follows: The main structure includes an outer shell, a main guide wire binding mechanism and a main guide wire binding mechanism. The main guide wire binding mechanism and the main guide wire binding mechanism are vertically symmetrically arranged inside the outer shell to define the force plane of the main guide wire and prevent it from deviating from the preset trajectory during longitudinal stretching. The wire clamp test module includes a main wire, a secondary wire, a splicing wire clamp, a transmission adapter block, and a cylinder. The splicing wire clamp is fixedly connected to the main wire and the secondary wire. One end of the transmission adapter block is connected to the splicing wire clamp, and the other end is connected to the cylinder. The cylinder is connected to the end of the secondary wire away from the splicing wire clamp and is used to adjust the drag force and attitude angle of the secondary wire. Drive module: includes motor base, motor, pulley, transmission connecting rod, cam, driven rod and wire clamp fixing rod. The motor is fixed to the motor base and the output end is connected to the transmission connecting rod through the pulley. The cam is sleeved on the transmission connecting rod. One end of the driven rod abuts against the cam and the other end is connected to the wire clamp fixing rod. The wire clamp fixing rod is connected to the wire clamp test module and is used to convert the rotational motion of the cam into sinusoidal reciprocating excitation motion. The conductor tensioning module includes a main conductor hook, a spring adjuster, and a tension spring. The main conductor hook is connected to one end of the main conductor, and the tension spring is connected to the spring adjuster. By adjusting the spring adjuster, the length of the tension spring can be changed, thereby achieving stepless adjustment of the main conductor tension. Current-carrying unit: used to connect current to the loop formed by the main line, the secondary line and the connecting clamp, to simulate the current-carrying heating conditions in actual service.

[0008] As a further technical solution of the present invention: the adjustable range of the excitation parameters of the drive module is: excitation frequency 0–50Hz, excitation force 0–1000N, and excitation stroke ≤10mm.

[0009] As a further technical solution of the present invention: the cylinder is a servo cylinder, which can precisely adjust the drag force of the secondary line and the angle with the main line, with an adjustment accuracy of ≤±0.5N and an angle adjustment range of 0°–30°.

[0010] As a further technical solution of the present invention: the current carrying unit has a current carrying range of 0–630A, supporting long-term stable current carrying.

[0011] As a further technical solution of the present invention, it also includes a data acquisition module for synchronously acquiring the main conductor tension, secondary conductor displacement / angle, excitation parameters and splice point temperature rise data during the test, with an acquisition frequency ≥10Hz.

[0012] As a further technical solution of the present invention: the spring adjuster is equipped with a tension feedback sensor, which forms a closed-loop control with the adjustment mechanism to ensure the long-term stability of the main line tension, with tension drift ≤ ±2% / 24h.

[0013] As a further technical solution of the present invention: the profile of the cam is a sine curve, which, together with the guide structure of the driven rod, makes the output reciprocating motion approximately a sine wave, and the motion smoothness error is ≤±5%.

[0014] As a further technical solution of the present invention, it also includes a safety monitoring module, which automatically cuts off the current carrying and vibration drive when the temperature rise at the connection point exceeds the preset threshold or the excitation parameters are abnormal, thereby achieving safety protection.

[0015] This technology proposes a large-span current-carrying accelerated test device for evaluating the durability of connection points, which has the following advantages and beneficial effects: 1. High degree of working condition reproduction: For the first time, four-field coupled loading of "longitudinal pre-tightening of the main line - adjustment of drag force of the secondary line - sinusoidal reciprocating excitation - current-carrying heating" is realized in a single platform, which completely reproduces the mechanical and electrical environment of the actual service of the connection point and solves the problem of insufficient loading dimension of the existing device; 2. Precise parameter control: The tension of the main line is infinitely adjustable and stable over a long period of time. The excitation frequency, excitation force, stroke, drag force of the secondary line, and included angle can all be precisely set, covering the key parameter range of splice point failure. The repeatability and comparability of test results are improved by more than 40%. 3. Controllable testing process: Multi-channel synchronous acquisition of tension, displacement / angle, excitation parameters and temperature rise data enables continuous tracking and quantitative characterization of the fretting-wear-crack evolution process, which is convenient for establishing life models and extracting failure criteria; 4. High safety and reliability: It integrates closed-loop tension control and safety monitoring functions, which can automatically cut off the current carrying and excitation drive under abnormal working conditions, avoid equipment damage and safety risks, and meet the safety requirements of long-term accelerated testing. 5. Wide range of applications: It is suitable for durability evaluation of conductors of different specifications and types of splice clamps. It can simulate various working conditions such as normal operation, extreme wind vibration, and overload current carrying, providing high-quality experimental basis for splice point structure optimization, material improvement and standardized testing. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the outer casing of the present invention; Figure 3 This is a structural diagram of the wire clamp test module of the present invention; Figure 4 This is a structural diagram of the driving module of the present invention; Figure 5 This is a structural diagram of the conductor tensioning module of the present invention.

[0017] In the diagram: 1-Main structure, 2-Wire clamp test module, 3-Drive module, 4-Wire tensioning module, 5-Outer shell, 6-Main guide wire harnessing mechanism, 7-Main guide wire harnessing mechanism, 8-Main guide wire hook, 9-Spring adjuster, 10-Tension spring, 11-Motor, 12-Motor base, 13-Pulley, 14-Transmission connecting rod, 15-Cam, 16-Driven rod, 17-Wire clamp fixing rod, 18-Transmission adapter block, 19-Secondary wire, 20-Main guide wire, 21-Connecting wire clamp, 22-Cylinder. Detailed Implementation

[0018] The present invention will be further described below with reference to the embodiments. It should be noted that these are merely examples and descriptions of the inventive concept. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, they should all be considered to fall within the protection scope of the present invention.

[0019] like Figure 1-5 As shown, the present invention proposes a large-span current-carrying accelerated testing device for evaluating the durability of splice points. The device comprises a main structure, a clamp testing module, a drive module, a conductor tensioning module, a current-carrying unit, a data acquisition module, and a safety monitoring module. These modules work together to achieve multi-field coupled loading and accelerated testing. The specific structure and connection relationships are as follows: The main structure 1 serves as the mounting base for the device, including the outer shell 5, the upper main wire harnessing mechanism 6, and the lower main wire harnessing mechanism 7. The outer shell 5 is welded from high-strength steel, providing enclosed protection and structural support. The upper main wire harnessing mechanism 6 and the lower main wire harnessing mechanism 7 are symmetrically fixed to the vertical plane inside the outer shell 5, using a roller-type guide structure to limit the movement trajectory of the main wire 20, ensuring that the main wire does not deviate from the preset force plane during longitudinal tension and lateral vibration, thus avoiding additional stress interference.

[0020] The clamp test module 2 is the core for the installation and stress distribution of the splice point, including the main conductor 20, the secondary conductor 19, the splice clamp 21, the transmission adapter block 18, and the cylinder 22. Both the main conductor 20 and the secondary conductor 19 use conductors with specifications consistent with actual power transmission and distribution lines (such as LGJ-400 / 50 type steel-cored aluminum stranded wire). The splice clamp 21 is the test piece to be evaluated, used to fix the main conductor 20 and the secondary conductor 19, simulating the actual splice structure. The transmission adapter block 18 is made of rigid alloy material, with one end bolted to the splice clamp 21 and the other end connected to the cylinder 22 to achieve effective transmission of excitation force. The cylinder 22 is a servo cylinder, which adjusts the drag force of the secondary conductor 19 and its angle with the main conductor 20 by extending and retracting the cylinder piston rod. The drag force adjustment range is 0–500N, and the angle adjustment range is 0°–30°, with adjustment accuracies of ±0.5N and ±0.5°, respectively.

[0021] The drive module 3 is the output source of the excitation force, including a motor base 12, a motor 11, a pulley 13, a transmission connecting rod 14, a cam 15, a driven rod 16, and a wire clamp fixing rod 17. The motor 11 is a variable frequency speed-regulating motor, fixed to the motor base 12. Its output speed can be adjusted by a frequency converter, thereby controlling the excitation frequency. The pulley 13 uses a synchronous belt pulley drive to ensure the smoothness and accuracy of power transmission. The transmission connecting rod 14 is fixed to the main structure through a bearing seat, with both ends connected to the pulley 13 and the cam 15 respectively. The cam 15 has a sinusoidal profile, ensuring that it drives the driven rod 16 in an approximately sinusoidal reciprocating motion during rotation. The driven rod 16 uses a sliding guide structure, cooperating with the guide sleeve of the main structure to restrict its movement only laterally. The wire clamp fixing rod 17 is rigidly connected to the driven rod 16, and its other end is fixed to the wire clamp test module 2, transmitting the reciprocating motion to the connecting wire clamp 21. By adjusting the motor speed and replacing cams with different profiles, adjustable output can be achieved with an excitation frequency of 0–50Hz, an excitation force of 0–1000N, and an excitation stroke of ≤10mm.

[0022] The conductor tensioning module 4 is used to achieve longitudinal pre-tensioning and tension adjustment of the main conductor, including a main conductor hook 8, a spring adjuster 9, and a tension spring 10. The main conductor hook 8 is fixedly connected to one end of the main conductor 20, and one end of the tension spring 10 is connected to the spring adjuster 9. The spring adjuster 9 is fixed to the end of the main structure 1 and adopts a screw adjustment structure. By rotating the adjustment knob, the length of the tension spring 10 is changed, thereby realizing stepless adjustment of the tension of the main conductor 20, with a tension adjustment range of 0–10kN. The spring adjuster 9 has a built-in tension feedback sensor, which forms a closed-loop control with the adjustment mechanism to monitor and compensate for tension drift in real time, ensuring tension stability during long-term testing.

[0023] The current-carrying unit is used to simulate the actual current-carrying heating conditions at the connection point, and includes a rectifier power supply, current-carrying wires, and terminals. The rectifier power supply outputs DC or AC current with a current carrying range of 0–630A, supporting long-term stable current carrying. The current-carrying wires are connected to the ends of the main line 20 and the secondary line 19 through the terminals to form a closed loop, putting the connection clamp 21 in a current-carrying state and generating Joule heating to simulate the temperature rise effect in actual operation.

[0024] The data acquisition module includes a tension sensor, a displacement / angle sensor, a vibration parameter acquisition unit, a temperature sensor, and a data acquisition card. The tension sensor is integrated into the main conductor hook 8 to measure the real-time tension of the main conductor. The displacement / angle sensor is installed at the hinge between the secondary conductor 19 and the cylinder 22 to collect the displacement and angle of the secondary conductor. The vibration parameter acquisition unit is connected to the frequency converter of the motor 11 and the displacement sensor of the driven rod 16 to collect the vibration frequency, amplitude, and vibration force. The temperature sensor uses an infrared thermometer or a contact temperature probe, aligned with the contact interface of the connector clamp 21, to collect real-time temperature rise data. All sensor signals are transmitted to the computer via the data acquisition card, with a sampling frequency ≥10Hz, enabling synchronous acquisition and storage of multi-dimensional data.

[0025] The safety monitoring module is linked with the data acquisition module, with preset temperature rise thresholds (≥150℃) and abnormal excitation parameter ranges (such as frequency exceeding 50Hz or excitation force exceeding 1000N). When the temperature rise at the connection point exceeds the threshold or the excitation parameters are abnormal, a control signal is automatically sent to cut off the power supply to the current-carrying unit and the motor power supply to the drive module, while simultaneously triggering an audible and visual alarm to prevent equipment damage and safety accidents. Example

[0026] Device assembly and commissioning Main structure installation: Fix the outer shell 5 to the experimental table, and install the main upper wire binding mechanism 6 and the main lower wire binding mechanism 7 in sequence, ensuring that the guide rollers of the two are on the same vertical plane and the parallelism error is ≤0.2mm / m; Drive module installation: Fix the motor base 12 and bearing base to the preset positions of the main structure, install the motor 11, pulley 13, transmission connecting rod 14 and cam 15, adjust the pulley tension to ensure smooth transmission; install the driven rod 16 and the wire clamp fixing rod 17 to ensure that the driven rod moves smoothly in the lateral direction without jamming, and the smoothness error of the movement is ≤±5%; Wire tensioning module installation: Fix the spring adjuster 9 to the end of the main structure, connect the tension spring 10 to the main wire hook 8, calibrate the tension sensor, and ensure that the tension measurement accuracy is ≤±1%; Installation of the wire clamp test module: Pass the main wire 20 through the upper wire binding mechanism 6 and the lower wire binding mechanism 7 of the main wire, fix one end to the hook 8 of the main wire, and fix the other end to the fixing seat at the other end of the main structure 1; install the splice clamp 21 to be evaluated, fix the secondary wire 19 to the splice clamp 21, and hinge the other end of the secondary wire to the cylinder 22; 5. Connection of the current carrying unit and data acquisition module: Connect the current carrying unit to the main wire 20 and the secondary wire 19 through the terminal block, and check the continuity of the circuit; install the temperature sensor and the displacement / angle sensor, connect the data acquisition card to the computer, debug the data acquisition software, and ensure that the data acquisition of each channel is normal.

[0027] Test operation steps (1) Main line tensioning: Adjust the length of the tension spring 10 through the spring adjuster 9, set the tension of the main line 20 to 5kN, and let it stand for 30 minutes. Confirm the tension stability through the tension feedback sensor, and the drift amount is ≤±2%; Step (2) Sub-line parameter setting: Start the cylinder 22, adjust the drag force of the sub-line 19 to 100N, set the included angle to 15°, and confirm the parameter stability through the displacement / angle sensor; Step (3) Excitation parameter setting: Start the drive module, set the motor speed through the frequency converter, make the excitation frequency 30Hz, control the excitation stroke to 5mm through the cam profile, and the excitation force to 500N. Run for 10 minutes to confirm that the excitation motion is stable; Step (4) Current carrying: Start the current carrying unit, connect 630A AC current, monitor the initial temperature rise of the connection point, and ensure Initial temperature rise ≤ 50℃; Step (5) Data acquisition and monitoring: Start the data acquisition software, synchronously acquire tension, displacement / angle, excitation parameters and temperature rise data, and set the acquisition frequency to 20Hz; Enable the safety monitoring module, set the temperature rise threshold to 150℃, and the abnormal range of excitation force to 0–1000N; Step (6) Accelerated test operation: Continuously run the test device, check the equipment operation status and data acquisition status every 24 hours, set the running time according to the test requirements (such as 1000 hours), until obvious wear, cracks or temperature rise exceeding the threshold appear at the connection point, and stop the test; Step (7) Post-test processing: Turn off the current-carrying unit and drive module, and after the equipment cools down, disassemble the connection clamp 21, observe its wear, cracks and ablation, and combine the acquired data to conduct failure mechanism analysis and life assessment.

[0028] The experimental results were verified by using this device to conduct accelerated durability tests on a certain type of parallel groove clamp. Compared with the test results of existing single-dimensional loading devices, the working condition reproduction rate of this device reached 92% (65% for existing devices), and the coefficient of variation of the test results was ≤8% (18% for existing devices). It can complete an accelerated test equivalent to 5 years of actual service within 1000 hours, improving the testing efficiency by more than 3 times. Through synchronously collected data, a correlation model between the wear of the connection point and the excitation parameters and current carrying capacity was successfully established, providing a precise basis for the structural optimization of this type of clamp.

[0029] The above is an exemplary description of the invention. Obviously, the specific implementation of the invention is not limited to the above-described manner. Any non-substantial improvement made using the inventive concept and technical solution of the invention, or the direct application of the inventive concept and technical solution to other situations without modification, is within the protection scope of the invention.

Claims

1. A large-span current-carrying acceleration test device for evaluating the durability of a connection point, characterized in that, The system includes a main structure, a wire clamp test module, a drive module, a conductor tensioning module, and a current-carrying unit. These modules work together to achieve a three-field coupled loading and current-carrying acceleration test involving longitudinal pre-tensioning of the main conductor, adjustment of the secondary conductor's drag force, and sinusoidal reciprocating excitation. The specific structure is as follows: The main structure (1) includes an outer shell (5), a main upper wire binding mechanism (6) and a main lower wire binding mechanism (7), wherein the main upper wire binding mechanism (6) and the main lower wire binding mechanism (7) are vertically symmetrically arranged inside the outer shell (5); The wire clamp test module (2) includes a main wire (20), a secondary wire (19), a connecting wire clamp (21), a transmission adapter block (18), and a cylinder (22). The connecting wire clamp (21) is fixedly connected to the main wire (20) and the secondary wire (19). One end of the transmission adapter block (18) is connected to the connecting wire clamp (21), and the other end is connected to the cylinder (22). The drive module (3) includes a motor base (12), a motor (11), a pulley (13), a transmission connecting rod (14), a cam (15), a driven rod (16), and a wire clamp fixing rod (17). The motor (11) is fixed to the motor base (12), and its output end is connected to the transmission connecting rod (14) through the pulley (13). The cam (15) is sleeved on the transmission connecting rod (14). One end of the driven rod (16) abuts against the cam (15), and the other end is connected to the wire clamp fixing rod (17). The wire clamp fixing rod (17) is connected to the wire clamp test module (2) and is used to convert the rotational motion of the cam (15) into sinusoidal reciprocating excitation motion. The conductor tensioning module (4) includes a main conductor hook (8), a spring adjuster (9) and a tension spring (10). The main conductor hook (8) is connected to one end of the main conductor (20), and the tension spring is connected to the spring adjuster (9). By adjusting the spring adjuster (9), the length of the tension spring (10) can be changed, thereby realizing stepless adjustment of the tension of the main conductor (20). The current-carrying unit shown is used to connect current to the loop formed by the main line (20), the secondary line (19) and the connecting clamp (21) to simulate the current-carrying heating condition in actual service.

2. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, The adjustable range of the excitation parameters of the drive module is: excitation frequency 0–50Hz, excitation force 0–1000N, and excitation stroke ≤10mm.

3. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, The cylinder (22) is a servo cylinder, which can precisely adjust the drag force of the sub-line (19) and the angle between it and the main line (20).

4. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, The current-carrying unit has a current-carrying access range of 0–630A and supports long-term stable current carrying.

5. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, It also includes a data acquisition module, which is used to synchronously acquire data on the tension of the main conductor, the displacement / angle of the secondary conductor, the excitation parameters, and the temperature rise at the splice point during the test.

6. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, The spring adjuster (9) is equipped with a tension feedback sensor, which forms a closed-loop control with the adjustment mechanism to ensure the long-term stability of the tension of the main line (20).

7. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, The profile of the cam (15) is sinusoidal, and in conjunction with the guide structure of the driven rod (16), the output reciprocating motion approximates a sine wave.

8. The large-span current-carrying acceleration test apparatus for evaluating the durability of the connection point according to claim 1, characterized in that, It also includes a safety monitoring module that automatically cuts off the current carrier and excitation drive when the temperature rise at the connection point exceeds the preset threshold or the excitation parameters are abnormal, thus achieving safety protection.

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