Wear and life prediction of the U-shaped connecter of transmission line system under strong wind load

https://doi.org/10.1016/j.engfailanal.2021.105404Get rights and content

Highlights

  • The wear experiment was carried out by the self-developed testing machine.

  • The wear response of U-shaped rings under the coupling system was analyzed.

  • The relationship between wear loss, axial force and the swing angle was obtained.

  • The proposed life prediction theory was verified by experiments.

Abstract

The strong wind environment may cause the wear of various fittings in transmission line system. The bearing capacity of the worn fittings will be greatly reduced, which will threaten the operation safety of transmission line system. Therefore, it is of great significance to investigate the wear of the fittings under strong wind load. The wear experiment of the U-shaped connecter was carried out. The finite element model of the coupling system considering the ground line, insulator string and U-shaped connecter was established. The effects of the span and wind speed on the dynamic characteristics of the fittings were analyzed. The probability distribution of wind speed in Xinjiang region of China was yielded from the measured average and maximum values of wind speed. The Extreme-Value Type I Distribution and Harmonic Synthesis Method were applied to synthesize the wind speed information. The movement angle and internal force of fittings in transmission line system were investigated under various wind speed levels. Based on the wear experiment and finite element analysis of the wear of the U-shaped connecter, the relationship between the wear loss, the axial force and the swing angle was proposed, which can be used to predict the life of U-shaped connecter. The results show that the predicted wear loss of the U-shaped connecters is in good agreement with the actual wear loss of the U-shaped connecters.

Introduction

Wind-induced vibration of transmission line is a common phenomenon, which is caused by the shedding of vortices on both sides of the line as the wind passes across the line. The wind-induced vibration of transmission line can lead to the wear of lines and fittings [1], [2], [3], [4]. U-shaped connecter is one kind of fittings in transmission line system, which is used to connect the transmission tower and line. In the process of maintenance and repair of transmission lines, it is often found that the U-shaped connecter is seriously worn. The Xinjiang region always suffers from strong winds above the level of 5th grade (average wind speed ranges from 8.0 to10.7 m/s). The U-shaped connecter in the 750 kV Urumqi-Turpan-Hami transmission line system was found to be severely worn after a year of operation, which has seriously threatened the safety of the transmission lines. Thus, the study on the wear behavior and life prediction of the U-shaped connecter in the strong wind environment is of great importance.

Wear of the U-shaped connecter is the result of the relative motion between the upper and lower U-shaped connecters. It causes the debris formation from the friction surface, resulting in the dimensional changes and weight loss on the contact surface. Kim et al.[5] investigated the effects of the material characteristics on the wear behavior of contact surfaces. Currently, the research on the wear of transmission line system was mainly limited to the wear of the conductor [6], [7], [8], [9], [10]. Azevedo et al.[11] focused on the failure of the conductor of the 460 kV overhead transmission line located along the crossing of the ParanáRiver. The typical static deformation and dynamic fretting wear tangential were observed on fracture cross-section. Cruzado et al.[12] explored the dynamic wear behavior and the developing process of the vibrating transmission line through the finite element method. It was found that the finite element method can well predict the wear life of line. Zhou et al.[13], [14] studied the fretting fatigue behaviors of the transmission lines. It showed that the fretting caused plastic deformation, wear and cracking, and then finally fatigue failure. Chen et al.[15] revealed that the abrasive fretting are the mechanism of fretting damage and the propagation of fatigue crack in the aluminum wire. FachriP et al.[16] carried out the experiment and finite element simulation research on the wear and fatigue of the conductor with a cross-section of 300 mm2. The finite element simulation results were in good agreement with that of the experiment. Marco et al.[17] investigated the failure characteristics of the aluminum alloy conductor under aeolian vibration. It revealed that the fractured wires shown typical static deformation marks and dynamic fretting wear tangential marks. Ma et al.[18] also studied the fretting wear behavior of aluminum cable steel reinforced conductors in different atmospheric conditions by experiment. It showed that the corrosive medium has a certain influence on the fretting transition phase.

There are some studies on the wear of the fittings of transmission line system. It is found that aeolian vibration, galloping, subspan vibration and ice jump of the line were the main causes of the wear of transmission line fittings [19], [20]. Refsnaes [21] carried out practical investigation and analysis on the operation of conductor support fittings on transmission lines in Norway in the past decades. It indicated that the prevailing wind direction affected the wear rates and the wear loss of the fittings was proportional to the insulator swing. You et al.[22] investigated the wear of the UB hanging plate of the ground line suspension string clamp under the continuous stable wind area. It revealed that the strong wind causes the side of hanging plate to contact with the bottom of the connecting angle steel, and the strong wind intensified the wear of fittings. In addition to the influence of wind-induced vibration on the wear of the fittings, the influence of wind-sand two-phase flow on the wear of the fittings has also been investigated [23]. It showed that the sandstorm can accelerate the wear of fittings.

A large number of wind-induced vibration experiments and analyses of transmission line system have been performed [24], [25], [26]. However, the influence of swing angle on the wear loss of U-shaped connecter is still lacking. The wind load acting on the lines makes the fittings move, and the relative motion of the fittings eventually leads to the wear of the fittings. The further study of the motion and wear law of U-shaped connecter is needed when the line is subjected to wind load. The current research and analysis of fittings wear did not consider the wind load environment. To investigate the wear behavior of fittings under strong winds, the wear experiment of the U-shaped connecter was carried out by the self-developed wear tester. The corresponding relationship among the swing cycles, experiment load, and residual strength was obtained. Based on the statistical data of the wind field in Xinjiang region, the finite element model of the transmission line-fittings system was established. The motion law of the fittings under various wind speed was explored, and the method for predicting the wear life of the fittings under the strong wind environment was proposed.

Section snippets

Experimental setup

The wear experiment of U-shaped connecter was carried out by the swing wear tester independently developed by the State Grid Xinjiang Electric Power Research Institute of China. The machine is shown in Fig. 1(a). It mainly includes mechanical power, mechanical transmission, mechanical execution and weight loading, as shown in Fig. 1(b). In the mechanical transmission part, the motor drives the crank to rotate, and then the connecting rod transmits the kinetic energy of the crank to the swing

Numerical simulation of wear experiment

The finite element software ANSYS is used for numerical simulation. The type of the U-shaped connecter in the experiment is U-12, which is made of Q235 carbon structural steel. It can be seen from the experiment that the lower U-shaped connecter will rotate around the upper U-shaped connecter under wind load, causing relative wear. The results show that the wear loss of the upper U-shaped connecter is greater than that of the lower one. In order to improve the accuracy of numerical simulation

Statistics of wind field

At present, many countries in the world use the annual maximum wind speed as the sample for probability statistics. The maximum or the basic wind speed for the region is obtained from the return period and the probability distributions of wind speeds. The function of Extreme-Value Type I Distribution is used to analyze the basic wind speed [29]. The expression of Extreme-Value Type I Distribution is as followsFI(x)=exp-exp-x-μσWhere μ and σ are respectively the position and scale parameters,

Conclusions

The wear experiment and the finite element simulation of the U-shaped connecter were carried out, and the influencing factors of wear were discussed. The Harmonic Synthesis Method was applied to simulate the wind field of the boundary layer, and a three-span transmission line model was established to investigate the wear behavior of the fittings under strong wind conditions. The safe service life of U-shaped connecter was predicted and the following conclusions are obtained:

  • (1)

    The wear experiment

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This study is supported by the National Natural Science Foundation of China (Grant No.: 51778097), Natural Science Foundation of Chongqing Science and Technology Commission (Grant No.: cstc2017jcyjB0210).

References (29)

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