149 research outputs found

    Monitoring of Overhead Polymer Core Composite Conductors Under Excessive Mechanical Loads Using Fiber Bragg Grating Sensors

    Get PDF
    This combined experimental and numerical study addresses mechanical effects associated with static and dynamic loading of novel High Temperature Low Sag (HTLS) transmission line polymer core composite conductors. The developed methodology was successfully applied to ACCC® to explain the complex failure mechanisms associated with combined bending and tension loading. Furthermore, the use of Fiber Bragg Grating (FBG) sensors was investigated for the first time to monitor the ACCC® design during installation and in-service. Transverse low-velocity impacts to the ACCC® conductor having either free or constrained end conditions and large axial tensile loads were performed. It was identified that the most damaging condition under impact is when the conductor had free ends and was thus subjected to severe bending. The experimental work performed using an original approach was supported by non-linear static and dynamic finite element analyses. For the multiaxial case of rods subjected to bending and axial tension, the axial stresses were predicted analytically and numerically with the likely failure initiating locations identified based on the theoretical composite compressive strengths. The initiating damage mechanisms change from compressive to tensile modes as axial tension increases. It has been shown for the first time that the natural presence of fiber misalignment must be considered in the failure analysis of hybrid composite rods as it can significantly reduce bending strength and influence the location of damage initiation. It has been demonstrated that FBG sensing is a viable technique for in-service monitoring of ACCC® conductors subjected to a variety of static and impact situations. Under static and low energy/velocity conditions, surface mounted sensors can accurately measure strains both on the bare rods and inside the conductors. The tests on the fullscale conductors under low energy impact also showed that the sensors can identify the location and magnitude of impact with a high degree of sensitivity. These results, combined with the intrinsic properties of optical sensors and fibers, indicate the FBG sensors could be especially useful in the monitoring of low and high energy impact events in-service. Finally, an evaluation of using of embedded FBG sensors inside the hybrid composite core of ACCC® is presented

    Monitoring of State Transitions in Extreme Environment Application Materials Using Fiber Bragg Grating Sensors

    Get PDF
    By embedding both a single fiber Bragg grating (FBG) sensor and a thermocouple (TC) during the manufacturing for extreme environment applications of certain classes of materials such as metals and polymers, a novel in-situ approach was developed to precisely monitor their entire manufacturing processes. This novel monitoring technique was able to identify many characteristic points during the curing of room and high-temperature epoxies and the solidification processes of metal alloys composed of tin and bismuth which were selected in this research purely for verification purposes. Some of the characteristic points identified for the epoxies were: (i) the gel point, (ii) the start of cure, (iii) the end of cure, (iv) the end of the manufacturing cycle, etc. For the tin/bismuth alloys, the technique was used for the first time to (i) identify the beginning and end of solidification and (ii) to construct the phase diagram of the alloys. It was demonstrated that the FBG sensor-based technique is better suited than the existing TC-based technique to detect the phase transitions of the alloys. The solidification process of water was also monitored and compared to the solidification process of the metals. The water solidification research was subsequently extended to simulate ice formation on transmission line conductors and to determine if the newly proposed FBG/TC method could be used as an ice monitoring method in service. A novel heat balance approach was presented to identify the degree of cure for the epoxies and to estimate the end of solidification in the alloys. The heat balance approach was verified using the Flory-Stockmayer theory for identifying the gel point in polymers. By using the FBG measurements and a combination of linear elastic models, a novel, yet straightforward approach was presented to determine the residual stresses in a single fiber/polymer composite. Further, multiple factors that impact the calculation of axial strain evolution using fiber Bragg grating (FBG) sensors were thoroughly investigated and verified by analyzing the cooling of the epoxies, the tin/bismuth alloys, and ice. The proposed monitoring technique could significantly improve the current capability to (i) measure the degree of cure of polymers, (ii) determine the residual strains and stresses in single fiber composites with polymer and metal matrices, (iii) assess the strain evolution during the solidification of metals, (iv) recreate the phase diagrams of metal alloys, (v) estimate stresses in solidified metal parts, (vi) monitor icing and deicing on transmission lines, and many others. Since the specimen preparation is straightforward, the proposed method can be routinely practiced, and the measurements can be completely automated. The techniques could provide a much-needed tool for rapid but accurate assessment of materials for extreme environment applications

    Icing Effects on Power Lines and Anti-icing and De-icing Methods

    Get PDF
    Icing on power lines may lead to compromise safety and reliability of electric supply network. Prolong icing can lead to power breakdown and collapse of towers. Since power transmission lines are mostly overhead and could face the direct impact of icing, and it is one of the main challenges faced by power distribution companies in cold regions. When the ice accretion crosses the safety limit then deicing action can be carried out. We can find number of deicing methods that are used in different parts of the world. However, all of these deicing techniques have their own advantages and disadvantages on implementation. It is one of the most difficult as well as dangerous process to perform deicing on power lines. If a fault is detected and that has been occurred due to icing or during routine maintenance, extra care must be taken in order to ensure safety of the personals when performing de-icing of lines. However, as technology evolved, new ways and techniques are adopted with the help of sensors that give quick feedback to control room in the national grid via wireless communication network for real time action. In the thesis we have discussed atmospheric icing impacts on power lines in the cold regions across the world. A literature review has been done for anti-icing and deicing methods that are currently adopted in the power distribution network. Methods that are used against ice buildups have also been analyzed. This work also shows the impacts of icing and deicing techniques presently adopted, and also throws light on their pros and cons during maintenance operations. It provides an overview of the evolving technology trends that are practiced to ensure the availability of existing power transmission system in cold climate regions

    Fiber Bragg Grating Based Sensors and Systems

    Get PDF
    This book is a collection of papers that originated as a Special Issue, focused on some recent advances related to fiber Bragg grating-based sensors and systems. Conventionally, this book can be divided into three parts: intelligent systems, new types of sensors, and original interrogators. The intelligent systems presented include evaluation of strain transition properties between cast-in FBGs and cast aluminum during uniaxial straining, multi-point strain measurements on a containment vessel, damage detection methods based on long-gauge FBG for highway bridges, evaluation of a coupled sequential approach for rotorcraft landing simulation, wearable hand modules and real-time tracking algorithms for measuring finger joint angles of different hand sizes, and glaze icing detection of 110 kV composite insulators. New types of sensors are reflected in multi-addressed fiber Bragg structures for microwave–photonic sensor systems, its applications in load-sensing wheel hub bearings, and more complex influence in problems of generation of vortex optical beams based on chiral fiber-optic periodic structures. Original interrogators include research in optical designs with curved detectors for FBG interrogation monitors; demonstration of a filterless, multi-point, and temperature-independent FBG dynamical demodulator using pulse-width modulation; and dual wavelength differential detection of FBG sensors with a pulsed DFB laser

    Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication

    Get PDF
    Optics and photonics are among the key technologies of the 21st century, and offer potential for novel applications in areas such as sensing and spectroscopy, analytics, monitoring, biomedical imaging/diagnostics, and optical communication technology. The high degree of control over light fields, together with the capabilities of modern processing and integration technology, enables new optical measurement systems with enhanced functionality and sensitivity. They are attractive for a range of applications that were previously inaccessible. This Special Issue aims to provide an overview of some of the most advanced application areas in optics and photonics and indicate the broad potential for the future

    MATLAB

    Get PDF
    Conventionally, the simulation of power engineering applications can be a challenge for both undergraduate and postgraduate students. For the easy implementation of several kinds of power structure and control structures of power engineering applications, simulators such as MATLAB/(Simulink and coding) are necessary, especially for students, to develop and test various circuits and controllers in all branches of the field of power engineering. This book presents three different applications of MATLAB in the power system domain. The book includes chapters that show how to simulate and work with MATLAB software for MATLAB professional applications of power systems. Moreover, this book presents techniques to simulate power matters easily using the related toolbox existing in MATLAB/Simulink

    Galvanic Corrosion of Aluminum/Carbon Composite Systems

    Get PDF
    Aluminum/carbon composite systems can have outstanding mechanical properties. Aluminum and carbon fiber reinforced polymer matrix composites (CFRP) are typically considered corrosion resistant when used alone, but can develop severe galvanic corrosion when in physical contact in the same component or structure. General engineering practice is to avoid contact between aluminum and CFRP in any application where moisture may be present, but it is still of great importance to understand the consequences if the two materials accidentally become in contact. There may also be applications where a low rate of galvanic corrosion is acceptable. This dissertation contributes unique experimental and numerical approaches to improve the fundamental understanding of galvanic corrosion in aluminum/carbon composite systems, with particular focus on rate limiting control mechanisms in a high-temperature low-sag bare overhead transmission line conductor utilizing a CFRP load bearing core. The improved understanding was accomplished partially by the development of a novel assessment method for the in-situ galvanic corrosion testing of bare overhead conductors of various designs. The method allows for real-time measurements of galvanic corrosion currents while retaining the original geometry of the conductors. One of the most important findings is that the galvanic corrosion is under cathodic control, which means that the total galvanic corrosion rate is determined by the exposed carbon area, and independent of the exposed aluminum area. Another important finding is that the galvanic corrosion process is under diffusion control, which means that the total galvanic corrosion rate is mainly controlled by the rate at which oxygen arrives at the carbon surface. The implication of these findings is that the geometry of the component or structure can affect the galvanic corrosion rate by orders of magnitude. The dissertation work has also included the development of a structural health monitoring method for CFRP supported overhead conductors using Time Domain Reflectometry (TDR). This comprehensive research has significantly contributed to the increased acceptance of CFRP supported bare overhead conductors in both the United States and worldwide. The knowledge gained in this study is already aiding the evaluation of existing conductor designs and the development of future ones
    • …
    corecore