Aluminum Conductor Composite Core Research Articles

Research and application of key technology of energy saving and capacity increasing for overhead conductors with carbon fiber composite core reinforced

Aluminum conductor composite core (ACCC) has many excellent comprehensive properties and is gradually popularized and applied in overhead transmission lines. As an energy-saving and environmentally friendly capacitance-increasing conductor, ACCC gives full play to the advantages of carbon fiber materials. This article analyzes the test results of ACCC and compares them with traditional aluminum conductor steel reinforced (ACSR) in terms of mechanical and electrical properties and proposes the development trend of ACCC.

Improved automatic defect detection from X-ray scans for aluminum conductor composite core wire based on modified Skip-GANomaly

The Aluminium Conductor Composite Core (ACCC) is a critical component of power transmission that needs automated nondestructive defect detection to prevent wire breaking accidents and ensure regular city operations. Unfortunately, the current supervised target detection scheme is limited in its generalization ability due to the diversity of defect morphology and the high cost of acquiring samples. To overcome these challenges, we propose an automatic defect detection method based on a modified Skip-GANomaly model using X-ray images of ACCC wires as input. We experiment with semi-supervised deep learning reconstruction methods to mitigate the lack of abnormal samples and improve the generalization ability of unknown defects. We also explore hierarchical reconstruction and Skip-Connection adjustment to enhance the reconstruction effect and defect identification based on Resnet50. The results show that our method can achieve high accuracy, recall, and precision levels of over 99 %, significantly highlighting the difference in defect morphology. Compared to existing supervised schemes, our Defect Detection Scheme with Hierarchical Reconstruction and Anomaly-Subtracted Image Discrimination (DHRAD) eliminates dependence on the number of abnormal samples and the diversity of defect types in the training set, and has the ability to detect defects with unknown morphology. Therefore, DHRAD provides an effective detection scheme for automatic nondestructive defect detection of ACCC in operation, based on computer vision and semi-supervised learning.

Internal Defect Detection of Overhead Aluminum Conductor Composite Core Transmission Lines With an Inspection Robot and Computer Vision

Overhead aluminum conductor composite core (ACCC) transmission lines are extensively used. However, internal defects of ACCC wires are difficult to detect, threatening the stability and security of the grid. Thus, a novel automatic detection system using an X-ray inspection robot and an anchor-free object detection model is proposed to solve the problem of detecting internal defects in ACCC wires. First, a new inspection robot with a nondestructive testing (NDT) system consisting of a digital radiography (DR) detection panel and a portable X-ray generator is developed to acquire X-ray images of ACCC wires. Then, the IN-ACCC dataset is created by collecting the X-ray images of artificial defective ACCC wires and then processing, classifying, and labeling the images. Finally, an anchor-free object detection model named CenterNet-NDT is proposed based on CenterNet for high-performance identification of internal defects. CenterNet-NDT has a specially designed feature fusion module composed of SPPCSPC, polarized self-attention (PSA), and a newly weighted bidirectional feature pyramid network named SOFPN. Compared with some state-of-the-art methods and CenterNet with different modules, the proposed CenterNet-NDT achieves the highest mAP of 90.60% on the IN-ACCC dataset. The proposed automatic internal defect detection system is verified to be effective and robust by lab experiments and has been repeatedly applied in actual ACCC transmission line inspection tasks to reduce the safety hazards of wire breakage.

Analysis of ACCC failure of composite core glass transition temperature reduction due to brittle damage

The failure analysis of the Aluminum Conductor Steel Reinforced (ACSR) was often based on conventional failure methods such as strength and fracture, and the failure analysis of the Aluminum Conductor Composite Core (ACCC) usually followed the analysis methods of the ACSR. This research proposed a new ACCC failure mode based on the glass transition temperature (Tg) of composite materials. In this paper, a fracture accident of a 500 kV overhead transmission line was discussed. Firstly, impact test found that composite core of the ACCC was more brittle than steel core of the ACSR, and the brittle damage of the composite core was inferred as the cause of the accident in combination with fracture analysis. Then, thermal-structural coupling analysis showed that the axial stress of aluminum wires increased to 33 MPa after the brittle damage of the composite core. Subsequently, thermoelectric coupling analysis showed that the operating temperature (T) of conductor was raised to 151 °C after the increment of the axial stress of the aluminum wires. Finally, in dynamic mechanical analysis, it was shown that the Tg of faulty composite core was reduced to 146.3 °C. According to investigation, the T of conductor was greater than the Tg of epoxy resin in the faulty composite core, resulting in a decrease in the tensile strength of the composite core, which eventually led to the ACCC failure. The failure mechanism proposed in this paper can provide a reference for the prevention and maintenance of ACCC lines in power grid system.

Study of Full Composite Pole-Aluminum Conductor Composite Core System Ice-Shedding Response

Full composite pole-aluminum conductor composite core system is gradually used in the 10kV distribution network. In order to study the different ice-shedding forms of the dynamic response of this distribution system, the author established a conductor-insulator and pole-conductor system with two finite element models to study the linear section and corner section of the line in different forms of ice-shedding and ice-shedding rate under the influence of the line ice-shedding response degree. The results show that the pole-conductor model is a good model for the design of distribution lines with carbon fiber cores. The results also show that the ice jump height of the pole-conductor model is smaller than that of the conductor-insulator model, which is related to the coupling relationship between the composite pole and aluminum conductor composite core. The stay wire of the corner pole will absorb most of the energy generated by ice-shedding. In addition, when non-uniform ice-shedding, the line vibration is more violent, the jump height is higher, and the maximum axial force generated after ice-shedding is greater, which has certain safety risks.

Efficiency assessment of technologies implementation in Vietnam power transmission system

Many flaws have emerged on Vietnam power transmission system, such as obsolete technology and aging components. High voltage direct current (HVDC) system, 750 kV system, Aluminum Conductor Composite Core (ACCC) conductor are determined by Vietnam government to be implemented because of their performance as well as their suitability to the existing system. Newton Raphson load flow method is utilized to analyze different scenarios, in which performance of these technologies are compared with each other to identify the most robust method to decrease real power loss in steady state working condition. As results signified, 750 kV system is the solution with highest efficiency, whereas ACCC and HVDC’s performance does not match the expectation.

Automatic defect detection from X-ray Scans for Aluminum Conductor Composite Core Wire Based on Classification Neutral Network

The internal defects of the Aluminum Conductor Composite Core (ACCC) can be effectively visualized by X-ray imaging. However, the online detection of internal defects in the carbon core is challenging due to the huge data quantity and inconspicuous defects. In this paper, we propose an automatic defect detection framework for ACCC X-ray scans based on deep convolution neutral networks. The proposed method is based on an image classification network, with Inception-Resnet as backbone. Image normalization is conducted as the pre-processing step to reduce the training cost. We also propose a new data augmentation method according to the morphological character of the defect samples, to improve the extensiveness of the method. Experiment results have proven that the proposed method can effectively recognize the small and inconspicuous defects, with 3.5% improvement on mean Average Precision, compared to the object detection network (RetinaNet). Experiment also verifies the positive effect for data normalization and augmentation.

Defect detection of Aluminum Conductor Composite Core (ACCC) wires based on semi-supervised anomaly detection

X-ray imaging is proven effective in the visualization of defects inside the Aluminum Conductor Composite Core (ACCC) wires. Although object detection pipelines have been extensively considered in the nondestructive testing tasks, the difficulty in obtaining defect samples has become the main obstacle to the application of such methods in the task of automatic defect detection for ACCC wires X-ray images. In this paper, we conducted a new semi-supervised approach based on anomaly detection. Different from the commonly used supervised methods, the proposed method requires only samples without defects for the learning process, therefore we are no longer limited by the insufficient and unbalanced defect samples. Experimental results show that the accuracy of the proposed method is up to 0.761, which proves the effectiveness of the method in the automatic defect detection of ACCC wires X-ray images.

Defect detection for aluminium conductor composite core X-ray image with deep convolution network

The Aluminum Conductor Composite Core (ACCC) has been considered one of the solutions for massively increasing requirements for the electricity power transmission in China due to its superiority in weight, strength and ampacity. Yet the popularize of ACCC lines suffer from damages caused during the construction, which may result in line broke in the future. In this paper, an automatic defect detection method based on Deep Convolution Network is proposed. Image classification framework with Inception-Resnet structure as backbone is applied. With the online self-designed robot, the proposed method can effectively detect the defects such as fracture, splitting and distortion, with a recall rate over 90%.

LineSpyX: A Power Line Inspection Robot Based on Digital Radiography

Most of the current power line inspection robots use cameras and LiDARs to inspect the power line surfaces and the surrounding environment. But it is still difficult to detect the internal defects of the power lines. In this letter, the design and implementation of LineSpyX, a novel power line inspection robot based on digital radiography (DR), is introduced to solve the problem of non-destructive testing (NDT) of the overhead Aluminum Conductor Composite Core (ACCC) wires. The proposed robot has a stable wrapped mechanical structure with a moving system, a live work system, and a NDT system. The wheeled moving system enables the robot to move on the wires and cross obstacles such as vibration dampers. The NDT system consists of a portable X-ray generator and a DR detection panel. When the robot performs the inspection task, the X-ray goes up through the ACCC wire to the panel, where the X-ray images of the internal carbon fiber cores are recorded. A deep learning based defect diagnosis method combined with manual diagnosis is proposed to detect potential defects. The main functionalities of the developed robot are verified by lab experiments and field tests.

Transient Thermal Field Analysis in ACCC Power Lines by the Green’s Function Method

The paper investigates the dynamics of the thermal field of the ACCC (aluminum conductor composite core) line. The system was heated by solar radiation and current flow. Conductor cooling was modeled using the total heat transfer coefficient as the sum of convective and radiative components. The temperature increase generated by the current is described by a system of parabolic differential equations with an appropriate set of boundary, initial and continuity condition. The mentioned boundary-initial problem was solved by a modified Green’s method, adapted to the layered structure of the system. For this purpose, Green’s functions, as the kernels of integral operators inverse to differential ones, were determined. Aluminum resistivity and heat transfer coefficient change significantly with temperature. For this reason, the solution to the problem is presented in the form of a lower and upper estimation of the heating curve and local time constant. A steady-state current rating was also determined. The results are presented graphically and verified by other methods (power balance and finite element). The physical interpretation of the presented solution is also given.

Thermal Characteristics of Aluminum Conductor Composite Core

Cheng, Z., 2018. Thermal characteristics of aluminum conductor composite core. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 356–358. Coconut Creek (Florida), ISSN 0749-0208.In this paper, the thermal characteristics of aluminum conductor composite core (ACCC) are studied with the example of ACCC315/40 conductor.The simulation software is used to simulate the relationship between the temperature and the temperature of the conductor under the condition of ACCC, and the influence of the wind speed on the surface temperature of the wire. The results show that with the increasing of numerical operation line current, wire surface temperature will increase, when the environment temperature changes, the temperature of wire will change the wind speed in the range of 0–1m/s, the wire surface temperature drop more largely, as the wind speed increases, the wire surface temperature drops greatly. The research of this paper provides the basis for the real-time monitoring of the conductor.

Mechanical behavior of carbon fibre composite rod subjected to pure bending loading

Carbon fibre composite rod (CFCR) has been widely used in Aluminum Conductor Composite Core (ACCC) conductor. CFCR is usually under flexural loading during the operation of electric power. Therefore, the flexural properties of CFCR are related with the safety of electric power supply. The failure of CFCR could lead to the outage of electric power. Therefore, it is of importance to analyze the mechanical behavior of CFCR under flexural loading. The material of CFCR is transverse isotropy, which is different from isotropy material. The available finite element models (FEMs) are based on isotropy material. It is unreasonable to use these FEMs to predict the mechanical behavior of CFCR. This paper presents a new FEM to analyze the mechanical properties of transverse isotropy materials. Using the proposed FEM, the mechanical behaviors of CFCR under flexural loading are obtained.

Effect of Carbon Fiber Modulus on Mechanical Behavior of Carbon Fibre Composite Rod

Carbon fibre composite rod (CFCR) has been widely used in Aluminum Conductor Composite Core (ACCC) conductor. The mechanical properties of CFCR are related with the safety of electric power supply. The mechanical properties of CFCR are mainly determined by volume fraction of carbon fiber. Therefore, it is necessary to analyze the effect of carbon fiber fraction on the mechanical behavior of CFCR. The relationships between carbon fiber fraction and mechanical properties help to the design of ACCC conductor. This paper presents a finite element model (FEM) to analyze the mechanical properties of carbon fibre composite. The mechanical behaviors of CFCR for different carbon fiber fractions were simulated by using FEM. Based on the simulated results, the effects of carbon fiber fraction on stress and strain of CFCR under pure bending loading were revealed.

The Line-broken Analysis of the Aluminum Conductor Composite Core

Aluminum conductor composite core has many technical advantages such as high tensile strength, light weight, low sag, large current carrying capacity. In order to study the influence of the broken of aluminum conductor composite core on the transmission tower, tower-line model was built by using the finite element software ANSYS/LS-DYNA, and the deformation of joints and stress of bar were analyzed. The impact load and the impact coefficient of the representative bars of the transmission tower are calculated. The results show that the impact acting on the tower is the most serious in the place of the conductor suspension point, the connection of upper and lower crank arms, the tower neck.

Thermal conductivity of graphene nanoplatelet/cycloaliphatic epoxy composites: Multiscale modeling

Composite materials using cycloaliphatic epoxy (CE) resins are used in some structural applications that require resistance to aggressive environments. Specifically, CE-based composites are used for structural reinforcement in aluminum conductor composite core (ACCC) high-voltage power lines. However, CE resins have a relatively low thermal conductivity, which makes it difficult to dissipate localized heating due to transmission line faults. Graphene nanoplatelet (GNP) reinforcement can potentially improve the thermal conductivity of CE composites (∼0.2 W/m-K) due to its superior in-plane thermal conductivity (∼5300 W/m-K). In this study, the thermal conductivities of GNP/CE composites are investigated by multiscale modeling using molecular dynamics (MD) and micromechanics simulation techniques. Different levels of GNP dispersion and aspect ratio are studied and compared to experimental data established herein and in the literature. The thermal conductivity of GNP/CE composites increases with increased GNP content, dispersion, and aspect ratio. Additionally, covalently functionalized GNP/CE systems are simulated to determine the effect of functionalization on thermal conductivity. The transverse thermal conductivity of GNP/CF/CE hybrid composites is further investigated and validated with experimental values. This study establishes a unique multiscale modeling approach for predicting thermal conductivity of polymer nanocomposite materials (and hybrid composite materials) based on molecular structure of the nano-reinforcement/polymer interface.

Evaluation of Carbon Fiber Cables in Transmission Lines

This article aims to present a technical alternative to improve the electrical conductivity in Transmission Lines (TL) and provide greater energy efficiency by using an Aluminum Conductor Composite Core (ACCC) instead of the most common conductor, the Aluminum Conductor Steel Reinforced (ACSR RAIL). Designated as a simulation line in this article, an existing TL with 500 kV and 181 km in length was considered, in order to study the exchange of four ACSR RAIL conductors per phase. Initially, the physical characteristics of these two types of conductors were compared, and the advantages of the other types of ACCC cables were considered. The technical analyses carried out were the corona effect, electrical parameters, losses by the Joule effect, the increasing of ampacity and reduction in the tower weight. The main contribution of the present manuscript is to perform this study considering all the previously mentioned parameters simultaneously. In general, conductors with a carbon fiber core presented a great potential for energy efficiency; indeed, considering some specific parameters analyzed in this research, the conductor ACCC PRAGUE could achieve an energy efficiency of 48.5%.

Multiscale thermal modeling of cured cycloaliphatic epoxy/carbon fiber composites

ABSTRACTCycloaliphatic epoxies (CEs) are commonly used for structural applications requiring improved resistance to elevated temperatures, UV radiation, and moisture relative to other epoxy materials. Accurate and efficient computational models can greatly facilitate the development of CE‐based composite materials for applications such as Aluminum Conductor Composite Core high‐voltage power lines. In this study, a new multiscale modeling method is developed for CE resins and composite materials to efficiently predict thermal properties (glass‐transition temperature, thermal expansion coefficient, and thermal conductivity). The predictions are compared to experimental data, and the results indicate that the multiscale modeling method can accurately predict thermal properties for CE‐based materials. For 85% crosslink densities, the predicted glass‐transition temperature, thermal expansion coefficient, and thermal conductivity are 279 °C, 109 ppm °C−1, 0.24 W m−1 K−1, respectively. Thus, this multiscale modeling method can be used for the future development of improved CE composite materials for thermal applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46371.

A finite element method of modelling and designing of an ACCC conductor

The ultimate breaking strength of conductors always plays a vital role in the long-term safe operation of transmission lines and it should be carefully considered in the designing of a conductor. While limited literature has been released regarding the strength calculation of ACCC (Aluminum Conductor Composite Core) conductors. In this study, a finite element method based on real conductor samples is proposed to evaluate the strength of the ACCC conductor, and investigate on how diameters (or sectional areas) of the composite core and aluminum strands influence the conductors’ breaking strength, thereby helping engineers design a proper diameter of an ACCC conductor. The finite element analysis shows that increasing the sectional area of the composite core leads to a larger breaking strength than increasing an equal sectional areas of aluminum strands, which is in line with the tensile experimental results. In specific, the relative errors between the simulated breaking strength and the experimental results are as low as less than 3%. Therefore, the finite element method presented in this work, to some extent, fills in the blank of strength calculation for ACCC conductors, and in practical terms, it could serves as guidelines for conductor-design engineers.

Creep life evaluation of aluminum conductor composite core utilized in high voltage electric transmission

The creep life of aluminum conductor composite core (ACCC) utilized in high voltage electric transmission was investigated using an experimental method based on the equivalence relationship. First, the time-temperature-stress equivalence relationship was developed using the time-temperature and the time-stress equivalence relationships. Then, tensile creep experiments were conducted under different temperatures and different stress levels to obtain the strain-time curves of the ACCC. Finally, the creep strain master curve was obtained using the experimental data based on the time-temperature-stress equivalence relationship, allowing prediction of ACCC creep life. The results will play an important role in evaluation of the long-term characteristics of the ACCC for engineering applications.