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

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

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

Mathematical Modelling and Design of Current Sensors in Non-Conventional Instrument Transformers

This research brings a novel approach for current measurement using magnetic shape memory (MSM) smart alloys. The non-conventional instrument transformer (NCIT) proposed in this research uses the property of these alloys that their shape changes when exposed to a magnetic field. It has been shown that it is possible to measure alternating currents (a.c.) in high voltage overhead transmission lines by correlating the magnetic field produced by the current to shape changes in an MSM-based sensor. Methodologies for finite element modelling of the proposed NCIT have been developed. The developed methodology and obtained results are validated by comparing them to the results obtained through an experiment done by a manufacturer of MSM materials. 5M Ni-Mn-Ga MSM crystals with Type I twin boundaries and a load of 0.5 N/mm2 were identified as the most suitable type of MSM materials for this application. The combination of a very long fatigue life, with relatively low twinning stress, makes them the most prospective for use in MSM-based current sensors. The main characteristics of overhead transmission lines are described as well as the types of conductors typically used. This analysis brought us to the conclusion that special attention in this research should be given to ACSR and AAAC conductors, more specifically to 528-Al1/69- ST1A conductor (old code MOOSE) and 996-AL5 (old code REDWOOD). Additionally, the latest trends in the development of overhead transmission lines are discussed, as well as international standards which are relevant to these types of lines. These conductors were modelled in finite element (FE) package ANSYS APDL, together with the MSM element and the magnetic circuit, and included into a single finite element model. This approach allows us to take into account significant changes that take place within an MSM element during its elongation. Based on this, we were able to determine both the bottom and upper limits of the measurement range, optimise the NCIT for transmission lines, and propose several designs of the NCIT. Finally, this allowed relating the current inside the conductor to the voltage at the output of the LVDT

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

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

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

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

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

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

Use of composite materials, health monitoring and self-healing concepts to refurbish our civil and military infrastructure.

An unavoidable by-product of a metallic structure's use is the appearance of crack, corrosion, erosion and other flaws. Economic barriers to the replacement of these structures have created an aging civil and military infrastructure and placed even greater demands on efficient and safe repair and inspection methods. As a result of Homeland Security issues and these aging infrastructure concerns, increased attention has been focused on the rapid repair and preemptive reinforcement of structures such as buildings and bridges. This Laboratory Directed Research and Development (LDRD) program established the viability of using bonded composite patches to repair metallic structures. High modulus fiber-reinforced polymer (FRP) material may be used in lieu of mechanically fastened metallic patches or welds to reinforce or repair damaged structures. Their use produces a wide array of engineering and economic advantages. Current techniques for strengthening steel structures have several drawbacks including requiring heavy equipment for installation, poor fatigue performance, and the need for ongoing maintenance due to continued corrosion attack or crack growth. The use of bonded composite doublers has the potential to correct the difficulties associated with current repair techniques and the ability to be applied where there are currently no rehabilitation options. Applications include such diverse structures as: buildings, bridges, railroad cars, trucks and other heavy machinery, steel power and communication towers, pipelines, factories, mining equipment, ships, tanks and other military vehicles. This LDRD also proved the concept of a living infrastructure by developing custom sensors and self-healing chemistry and linking this technology with the application of advanced composite materials. Structural Health Monitoring (SHM) systems and mountable, miniature sensors were designed to continuously or periodically assess structural integrity. Such systems are able to detect incipient damage before catastrophic failure occurs. The ease of monitoring an entire network of distributed sensors means that structural health assessments can occur more often, allowing operators to be even more vigilant with respect to flaw onset. In addition, the realization of smart structures, through the use of in-situ sensors, allows condition-based maintenance to be substituted for conventional time-based maintenance practices. The sensitivity and reliability of a series of sensor systems was quantified in laboratory and real-world environments. Finally, self healing methods for composite materials were evolved--using resin modules that are released in response to the onset of delaminations--so that these components can provide a living infrastructure with minimal need for human intervention. This program consisted of four related research elements: (1) design, installation, and performance assessment of composite repairs, (2) in-situ sensors for real-time health monitoring, (3) self healing of in-service damage in a repair, and (4) numerical modeling. Deployment of FRP materials and bonded joints requires proper design, suitable surface preparation methods, and adequate surveillance to ensure structural integrity. By encompassing all 'cradle-to-grave' tasks --including design, analysis, installation, durability, flaw containment, and inspection--this program is designed to firmly establish the capabilities of composite doubler repairs and introduce technology to incorporate self-monitoring and self-healing (living structures) methodologies. A proof-of-concept repair was completed on a steel highway bridge in order to demonstrate the potential of composite doubler technology for critical infrastructure use