Suspension Clamp Research Articles

Dynamic identification method for stiffness of duplex suspension clamp based on system modes

This paper proposes a dynamic identification method based on system modes to identify the stiffness of the duplex suspension clamp in the engine hydraulic pipeline. The hammering method measures the free modes of seven groups of duplex suspension clamp-double pipe (DSC-DP) specimens (including the same diameter and different diameters). The results show that the angular stiffness of duplex suspension clamp (DSC) is related to the first and fifth modes, and the line stiffness is related to the second and sixth modes. The dynamic model of the double pipe system with duplex suspension clamp is established by the dynamic stiffness matrix (DSM) method. The approximation function between the theoretical and the experimental frequency of the duplex suspension clamp is established to reverse the stiffness of the duplex suspension clamp. The frequency response function (FRF) of the system theory and the experiment is predicted according to the results of the reverse stiffness. The coincidence of the frequency results verifies the correctness of the proposed method. Moreover, the validity of the stiffness of the duplex suspension clamp is verified by comparing the frequency results obtained from the theory, experiment, and finite element method (FEM) under the free and fixed boundary conditions. The method of identifying the stiffness of duplex suspension clamp and the obtained stiffness in this paper can provide positive guidance for the vibration analysis and modal test of aero-engine pipelines.

Horizontal Tensile Machine for Mechanical Tests Applicable to Suspension Clamps, Transmission Line Accessories, and Overhead Conductors

This work aimed to design a tensile horizontal machine that performs mechanical testing for suspension clamps, transmission line accessories, and overhead conductors with the following features: the suspension clamps device will be a permanent part of the structure, requiring a minimal setup; and it will accept overhead conductor specimens with lengths of up to 12 m and also be able to perform testing for pieces that require the plate-fork fastening option. Analytical and numerical calculations are performed according to the AISC-360-16 standard and static structural module of ANSYS software, respectively, to compare results.

A Passive Compliance Obstacle-Crossing Robot for Power Line Inspection and Maintenance

In scenarios of the overhead power line system, manual methods are inefficient and unsafe. Meanwhile, the majority of cantilevered robots have poor efficiency when crossing obstacles. This paper proposes a novel power line inspection and maintenance robot to solve these problems. The robot employs a passive compliance obstacle-crossing principle, which could rapidly cross obstacles with the cooperation of gas springs and climbing wheels. Under high payload, the robot could take 5-15 seconds without any complex strategies to roll over obstacles. A variable configuration platform is also designed, which has a multiple line mode and a single line mode. It makes the robot suitable for different kinds of overhead power lines. Meanwhile, the related adaptability analyses are presented. Manipulators are also installed to help the robot perform specific maintenance tasks. The results of lab experiments and field tests reveal that the robot could stably and rapidly cross obstacles, such as suspension clamps, vibration dampers, and spacers, and could perform three kinds of maintenance tasks on the line.

Electrical Inspection and Autometed Robot for Electrical Transmission Line Inspection

Abstract: The paper presents sharing several of experiences and practices on smart robotic application for overhead transmission line maintenance and inspection. The robotic puller passes over barriers below the power line, such as the road with traffic, power distribution lines, river, or vegetation making tasks achieved conveniently, safely, and rapidly without impact on nearby communities.The target of the research is to create a mobile robot prototype for inspection of overhead power lines. The inspection robot shall crawl along the ground wire and transpose autonomously across installed equipment on the ground wire, such as vibration dampers, suspension clamps, compression dead ends, etc. In addition, the inspection robot is able to take photos and videos during a transmission line inspection . Using the robot, transmission line inspection’s labor cost can be reduced, and the new method helps improve patrol and inspection efficiency, comparing to the conventional manpower method. Trough utilization of the new maintenance and inspection robots, utilities can minimiz transmission line operation & maintenance budget.

Effect of Suspension Clamp Types on the Dynamic Bending Stress of All Aluminium Alloy 1120 Overhead Conductors

Determination of the bending stress is one of the important factors for the design or fatigue assessment of transmission power lines. Researchers and designers calculate the bending stress of overhead conductors by using the Poffenberger–Swart (P-S) formula, which was established for the conductor/metal suspension clamp system. This publication presents experimental work on the effect of different configurations of suspension clamps on the dynamic bending stress that causes fatigue in the conductor. For each type of clamp configuration, specific points of the conductors were instrumented with strain gauges for the measurement of bending strain. The prediction of bending stress by the P-S formula presented errors of up to 140% for clamp different from the one established during the formulation. A better correlation with experimental data was obtained by adjusting considering an effective length of the lever arm for elastomeric clamps.

Design of Backup Protective Hardware for Suspension Clamp of Electric Power Overhead Ground Wire

Aiming at the disconnection problem of power overhead ground wire caused by wind vibration or the action of power frequency short-circuit current, the newly revised “Eighteen major anti-accident measures of State Grid Corporation China” proposes that independent double string structure should be adopted in suspension clamp of overhead ground wire. Based on this, a research scheme of backup protective hardware for the suspension clamp of the overhead ground wire of the power transmission line is proposed. In this scheme, the backup protective hardware for the suspension clamp is designed and added on the premise that the original overhead ground wire-suspension clamp structure is not changed. It provides backup measures for the original suspension clamp and reduces suspension clamp heating by an electrical shunt. Finally, the mechanical failure load test and salt spray test are performed on the designed production. The results show that the designed production meets the standard and could be used in actual engineering. At the same time, the practical engineering application shows that the backup protective hardware can effectively reinforce the ground wire suspension clamp with double strings, avoiding the problem of dropping and breaking after the original clamp is broken.

Research on Independent Live Replacement Method and Equipment for Suspension Clamp of ±800kV Transmission Line

UHV transmission lines are of great significance to the long-distance transmission of electric energy. Suspension clamp is a common hardware of line tower, and its maintenance method has large load transfer and low working efficiency. Aiming at this problem, the independent live replacement method of suspension clamp is put forward, the safety is analyzed, and the simulation analysis and test verification of the developed equipment are carried out. The results show that the research results can greatly reduce the transfer load and improve the working efficiency, which is of great significance to this type of maintenance.

Numerical study of aeolian vibration characteristics and fatigue life estimation of transmission conductors.

The 2D computational fluid dynamics (CFD) model of transmission conductor is set up to simulate the aerodynamic forces varying with time on the conductor. Taking into account the geometrical nonlinearity of conductor lines, the finite element (FE) models of single span and two-span transmission lines discretized with beam elements are established. By means of the FE models, the aeolian vibrations of the conductor lines excited by the aerodynamic forces under different wind velocities are numerically simulated. The nonlinear resonant characteristics, the amplitude-frequency relations of the conductor lines during aeolian vibration are investigated, and the influences of the span length as well as the initial tension in conductors on the aeolian vibration characteristics are analyzed. Furthermore, a 3D FE model of a conductor segment and the suspension clamp is created to study the stress distributions of the 3D model corresponding to different lines during aeolian vibrations. Finally, based on the stress analysis of the 3D model, the fatigue lives of the transmission conductors during aeolian vibration under different wind velocities are estimated. The jump phenomenon induced by the nonlinear vibration is reflected by the numerical simulation considering the geometric nonlinearity, and it is found that the energy balance principle (EBP) overestimates the vibration amplitudes because it cannot take the influences of the geometrical nonlinearity and span length into account. The obtained results may provide some instructions for the prevention design of aeolian vibration.

Attention-Guided Multitask Convolutional Neural Network for Power Line Parts Detection

Power line parts detection refers to the inspection of key parts on transmission lines against the complex background in aerial images and identifying whether exist anomalies that cause transmission failure. Obviously, this process plays a pivotal role in ensuring the safety of power transmission. Most of the existing methods are based on deep convolutional neural networks. However, the complexity and variability of the aerial image background and the problem of unmanned aerial vehicles (UAVs) shooting perspective and distance pose a challenge for previous works. This study aims to improve the detection accuracy of the model and propose an attention-guided multitask convolutional neural network (AGMNet). First, to enhance the feature representation of objects in aerial images, we construct spatial region attention blocks that are suitable for object detection. It can be inserted into any existing convolutional backbone network. Due to its efficient feature tensor computation method, the network can obtain competitive results with less computational memory. Second, we introduce a multitask framework that creatively considers the identification of rust levels and abnormal conditions of power line components, which has not been considered in previous works. Finally, we incorporate the refinable region proposal network (RPN) structure and multiscale training strategy to improve the robustness of the network. The experimental results on the testing datasets show that the proposed AGMNet can recognize the power parts (dampers and suspension clamps) with a mean average precision (mAP) of 95.3% and simultaneously identify their rust levels with an mAP of 75.4% and abnormal conditions with an mAP of 92.7%.

A case study of rupture in overhead ground wire twined by armor rod

The armor rod (AR) is used to repair the damaged overhead ground wire (OGW) and prevent the wear of the OGW in the suspension clamp in engineering. Once the OGW at the AR terminal breaks, it may lead to temporary blackout, which also causes the severe economic losses, or even threatening public safety. However, there are few literature or report about this type of accident at present. Therefore, based on a rupture accident of OGW at the AR terminal, the reason for this accident was investigated in this paper. Firstly, the description of the accident background and the material analysis for the accident sample were presented to preliminarily determine the damage characteristics of OGW and the cause of the accident. Secondly, simulation experiments for the transient temperature rise of the AR terminal were conducted. The macroscopic morphology characteristics of the experimental samples were also analyzed. Finally, based on the electromagnetic thermal coupling, a finite element model of the AR terminal of OGW was established. The overheating mechanism at the AR terminal was also discussed according to the model. The discharge occurrs at the AR terminal under the short-circuit current (SCC), and it is also the prime factor that causes the high temperature of OGW. The research methods and conclusions in this paper can provide theoretical guidance for the analysis of similar accidents and the optimization design of structures.

Numerical modeling and analysis of thermal and mechanical behavior for ground wire-clamp system under short-circuit current

In the ground wire-clamp system, aluminum armor tape (AAT) or armor rod (AR) is commonly adopted to avoid the wear damage of ground wire. While under the short-circuit current, damage or even breakage of ground wire in suspension clamp due to overheat may occur. However, there still lacks attention on the investigation about this type of damage. In this paper, a finite element (FE) modeling method of the ground wire-clamp system, which was applicable to two cases with AAT and AR, was proposed to discuss the transient thermal and mechanical behaviors. In the modeling of contact points, an improved contact bridge model considering the contact shape characteristics was proposed. The transient temperature rise experiments for ground wire-clamp systems with AAT and AR were carried out to verify the accuracy of models. The results shows that the improved contact bridge model is conducive to obtaining the accurate calculation results. For the analysis of this type of damage, the generated thermal stress cannot be ignored. In engineering, the ground wire twinned by AAT is at risk of overheat or even breakage under the short-circuit current, while using AR can prevent the ground wire in the suspension clamp from damage of overheat.

Fatigue Evaluation of All Aluminium Alloy Conductors Fitted With Elastomeric and Metallic Suspension Clamps

Overhead conductors for transmission lines are subjected to cyclic loading due to Aeolian vibration which can lead to the failure of their wires. One of the most critical transmission power line points where fatigue failure occurs is the vicinity of the assembly consisting of the conductor and the suspension clamp. This work evaluates the fatigue life of assemblies made by two types of conductors, i.e., All Aluminium Alloy Conductor (AAAC) 1120 and 6201. Furthermore, metallic and elastomeric clamps are examined. Based on the generated S-N and <inline-formula><tex-math notation="LaTeX">${\boldsymbol{f}}{{\boldsymbol{y}}_{{\boldsymbol{max}}}}$</tex-math></inline-formula>-N graphs, it was proved that the assembly AAAC 1120 with elastomeric clamp presented a better fatigue performance than the other three assemblies. Additionally, the change in fatigue life was investigated, failure and contact marks analyses were also performed on all samples after the fatigue test with respect to the conductor layer where the failure occurred as well as the types of break and the position of wires&#x2019; break (whether radial and longitudinal position).

Friction Properties at the Contact Interfaces of Overhead Line Aluminium Conductors

Overhead conductors may undergo fretting fatigue failures at contact interfaces located at or near the suspension clamps. Some recent experimental studies were carried out on individual wires to understand the fretting fatigue phenomenon. However, the majority of the available results are for the wire-to-wire contact configuration, while little interest has been brought to the wire-to-clamp contact configuration, which is typically a critical interface for conductor fatigue. A new experimental test bench intended to perform fretting fatigue tests on individual strands of overhead conductors is used to study the wire-to-clamp and the wire-to-wire contact configurations. Variable displacement amplitude (VDA) tests under different normal contact forces were carried out on 1350-H19 aluminium wires for both contact types. The experimental results showed a slight difference between the studied contact configurations in terms of the friction coefficient values and the transition sliding amplitude. To complete this analysis, constant displacement amplitude (CDA) tests were carried out sweeping the displacement range and replacing the tested specimen for each test. The resulting contact marks are observed using an optical microscope and a good correlation is found between both types of tests in terms of friction coefficient and transition sliding amplitude. This study allowed characterizing the sliding conditions of wire-to-clamp contact in the context of fretting fatigue of aluminium conductors and is an important step in the development of a method to evaluate the fatigue life of conductors using fretting fatigue tests of individual wire-to-clamp contacts.

Fretting fatigue life assessment of overhead conductors using a clamp/conductor numerical model and biaxial fretting fatigue tests on individual wires

AbstractThe fatigue life of overhead conductors is usually evaluated through experimental tests on clamp/conductor assemblies. Some recent studies aim to estimate the fatigue life of conductors using uniaxial tests on individual strands. This paper presents an innovative method for assessing the fretting fatigue life of overhead conductors combining the effect of both tension and bending loadings. It consists of coupling a numerical approach based on modeling the clamp/conductor assembly using the finite element method and an experimental one based on fretting fatigue tests on individual wires. A biaxial fretting fatigue test rig has been developed and validated through preliminary tests performed on 1350‐H19 aluminum wires under uniaxial and an equivalent biaxial loading. Tension and bending loadings obtained from the numerical model were then applied on individual wires. Results showed a good correspondence with existing experimental data of the fatigue tests carried on the aluminum conductor steel reinforced (ACSR) Bersfort conductor with a metal‐to‐metal suspension clamp.

Research on maintenance tools of wire clamps for live working on Ultra High Voltage transmission lines

Aiming at the problem that the suspension clamp is difficult to be quickly replaced due to the heavy load of the suspension clamp when replacing the transmission line wire suspension clamp in the UHV live operation, this paper develops an auxiliary device for realizing the rapid replacement of the conductor suspension clamp. Through the design of fixtures suitable for the installation of UHV wires and connecting plates, the load transfer of the suspension clamp can be quickly realized, and the suspension clamp can be separated and replaced under the condition of no force. The device is flexible and light, and effectively improves the live working personnel work efficiency.

Characteristics of the asymmetric Stockbridge damper

The Stockbridge damper (tuned mass absorber) is used on overhead transmission power lines to suppress wind-induced vibrations. These power lines get exposed to various types of wind motions that cause them to vibrate and this causes fatigue failure at the suspension clamp where the maximum stress occurs. Aeolian vibration is the most common wind motion that causes fatigue and eventually, failure to transmission lines. This paper presents the study of an asymmetric Stockbridge damper. A set of experiments were conducted on the damper according to the Institute of Electrical and Electronics Engineers (IEEE) 664 standards to evaluate the characteristics of the asymmetric Stockbridge damper. The results obtained revealed that the asymmetric damper is four degrees of freedom. The results also revealed a relationship between the mass and the magnitude of the resonance frequency.

A preliminary analysis on mechanical characteristics of transmission conductors in the vicinity of suspension clamps

Overhead transmission conductors are prone to wire strands breaking under the conditions of breeze vibration, and many broken strands occur in the vicinity of suspension clamps. In order to research the stress distribution characteristics of the conductor in the vicinity of suspension clamps, a relatively effective Finite Element (FE) model was proposed. Preliminary verification of model rationality through comparative analysis of theoretical calculation and simulation, and use this model to study the mechanical characteristics of the cross-section of the conductor in the key position of the conductor-clamp system. The research conclusions are as follows: a new concept of equivalent bending stiffness and equivalent diameter is proposed, which is used to calculate the alternating bending stress of conductors under breeze vibration conditions. The alternating bending stress of the wire strands follow the bending amplitude (Y b) increases with increasing. Under the complex load, the Equivalent (Von-Mises) stress of the aluminum wire strands at the Last Point of Contact (LPC) of the conductor and the clamp shows a decreasing trend from the outside to the inside, and the maximum Von-Mises stress occurs at the contact position between the outermost wire strands and the clamp.

Analysis on Mechanical Characteristics of Catenary Positive Feeder in Gale Area

ABSTRACT To investigate the mechanical characteristics of catenary positive feeders under galloping state in gale areas, the aluminium cable steel reinforced (ACSR) LGJ-300/25 used in the catenary positive feeder of the Lanzhou- Urumqi high-speed railway is taken as an example. Then, on the basis of galloping amplitude and frequency, the tension on the conductor is deduced. In accordance with the structural and material characteristics of the conductor, a 3D finite element model of the positive feeder is constructed by ABAQUS software. The correctness of the model is verified by comparing the theoretical calculation and simulation results of tension stratification. Different tensile loads are applied to the model to simulate the force of the positive feeder under different galloping degrees, and the mechanical changes of the whole and sections of the steel and aluminium strands are analysed. Results show that under tensile load, the overall deformation of the positive feeder presents a stepped distribution, and the tension of the steel core and aluminium strand varies from inside to outside; the tension ratio is approximately 3:2. The stress at the outlet of the suspension clamp is complex and prone to stress concentration, which mainly cause the fatigue damage of the positive feeder. The results of this study can provide a theoretical reference for the selection and optimal design of electrified railway conductors in gale areas.

Effect of Sr Modifier on Microstructure and Mechanical Properties of ZL102 Casting Suspension Clamp

In this thesis, the microstructure and mechanical properties of the suspension clamp made of ZL102 material modified with different amounts of Sr added are studied, and the grip strength and damage load of the suspension clamp as well as the tensile testing properties at room temperature, hardness and impact toughness of the material are tested. The results show that with the increase of Sr addition, α solid solution gradually changes into dendrite, while coarse strip eutectic silicon and bulk primary crystal silicon gradually change into granular and short-rod shapes. With the addition of Sr modifier, the tensile strength, elongation, expansion and impact toughness of ZL102 material increased significantly, and the hardness value decreased slightly but with a smaller range. The grip strength test of suspension clamp modified with different added amounts of Sr meets the standard requirements, and the damage load test of suspension clamp modified without Sr does not meet the requirements. When the added amount of Sr is 0.0250%, the type test index of suspension clamp is stable and dispersive.

Analysis on three typical abnormal microstructures of overhead power line suspension clamps

This article lists three typical abnormal microstructures of overhead power line suspension clamps, including inclusion, flake graphite and cementite network. A series of tests including macro check, hardness measurement, composition tests, Energy-dispersive x-ray analysis and metallographic observation have been carried out. The experimental results showed that the causes of abnormal microstructures mainly include: high content of impurities, flake graphite blank and unfulfilled annealing heat treatment. It is suggested to strengthen the supervision on suspension clamps before using, and focus on the quality inspection of metallographic structure and composition.