Improving the Outdoor Insulation Performance of Chinese EHV and UHV AC and DC Overhead Transmission Lines
Xidong Liang, Shaohua Li, Yanfeng Gao, Zhiyi Su, and Jun Zhou — Xplore Link
Performance of Outdoor Insulators in Tropical Conditions of Sri Lanka
Sarath Kumara and Manjula Fernando — Xplore Link
Assessment of External Insulation Problems Related to Pollution and Climatic Conditions in Ethiopia
Berhanu Zelalem and Mengesha Mamo — Xplore Link
Lightning Withstand of Medium Voltage Switches and Cut-Out Fuses Considering Standard and Nonstandard Impulse Shapes
G. H. Faria, G. P. Lopes, T. C. Rodrigues, E. T. W. Neto, T. A. Nogueira, and M. P. Pereira — Xplore Link
From the Editors
From the Editors’ Desk July-August 2020
This issue of the Magazine is entirely dedicated to outdoor insulation of electric power networks. We present articles written by authors from China, Sri Lanka, Ethiopia and South Africa illustrating the states of national awareness to pollution-related problems. We also have an article from Brazil that reports on research aiming to understand and model the lightning withstand of switches and cut-out fuses designed to operate on overhead distribution lines.
The first article is entitled “Improving the outdoor insulation performance of Chinese EHV and UHV AC and DC overhead transmission lines”. It is written by a team of authors from Beijing, China. These are Xidong Liang and Shaohua Li of Tsinghua University, Yanfeng Gao of North China Electric Power Research Institute and Zhiyi Su and Jun Zhou of China Electric Power Research Institute. It describes long lasting efforts, undertaken by engineers and researchers of the country, to mitigate the effects of large area power outages caused by pollution flashovers. Power grid of China has, over the last 50 years, undergone a quick expansion. Pollution-related problems threatened its reliable operation over many years but had gradually been eliminated. This successful result was achieved thanks to introducing two main measures. The first included a proper classification of pollution severity in overhead line corridors, i.e. preparation of a detail pollution distribution map for the whole country, and an introduction of appropriate procedures for insulator selection and dimensioning. The second measure was based on a wide application of silicone rubber composite insulators, where the completed research efforts allowed to eliminate the reduction of their long-term electrical and mechanical performance. Experience aroused from the large expansion of the country HVDC power transmission system and the measures adopted to mitigate the related pollution problems are also reported and analyzed. The authors conclude that the reliability of EHV and UHV AC and DC overhead lines has increased significantly and the rate of pollution outages have since 2007 decreased by two orders of magnitude, as compared with its peak value in 2001, even though the length of the lines increased dramatically and the costs involved in their construction and maintenance reduced significantly.
The second article in this issue is on “Performance of outdoor insulators in tropical conditions of Sri Lanka”. It is authored by Sarath Kumara and Manjula Fernando from Peradeniya University in Sri Lanka. This article presents results of investigations performed over 25 years on many ceramic and composite insulator units installed at 10 test sites, covering coastal and inland areas in tropical conditions of the country. The majority of those insulators had been installed in 33 kV distribution or 132 kV transmission systems belonging to Ceylon Electricity Board, the power company of Sri Lanka. Some of them were non-energized and exposed to tropical weather conditions only. Evaluation of insulator performance was based on visual scrutiny and measurements of hydrophobicity level, leakage current, surface conductivity, equivalent salt deposit density (ESDD), and biological growth concentration. Withstand voltage tests were also performed. In the coastal sites, natural washing of the pollution layer by heavy tropical rains during monsoons significantly reduced the leakage current activity and ESDD level. In the clean inland sites, green algae occupied partially shaded areas of the insulators. Also lichen colonies were found on pin type porcelain insulators. Once the porcelain insulators were contaminated by algae, their wet and dry withstand voltage levels were noticeably reduced. The silicone composite insulators preserved the hydrophobicity on non-contaminated areas. The overall investigation concludes that application of silicone rubber composite insulators provides a better option for combating salt pollution effects in coastal areas whereas all the tested types performed well in inland areas exposed to significant biological contamination.
The third article reports on “Assessment of external insulation problems related to pollution and climatic conditions in Ethiopia” and is authored by Berhanu Zelalem and Mengesha Mamo from Addis Ababa University in Ethiopia. It reports on a variety of meteorological and environmental conditions in the country, based on long term (30 years) meteorological data. The article also introduces a rough classification of general types of environments, pollution types and their sources that impact performance of insulators of overhead transmission lines in the nine operational regions of the Ethiopian national power grid. This classification is further used as a base for selection of nine test sites for detailed research work aiming to determine an accurate map of site pollution severity of the regions. In addition, the article assesses the general policy of the Ethiopian Electric Power (EEP) company related to selection and dimensioning of insulators for the existing and planned transmission and substation projects. It also attempts to evaluate procedures for insulator monitoring and maintenance. It finally presents typical examples of problems met in practice and attempts to find a pattern in monthly records of transient earth faults and correlate it with the variation of meteorological and environmental conditions.
The fourth article of the issue is entitled “Lightning withstand of medium voltage switches and cut-out fuses considering standard and nonstandard impulse shapes”. It is authored by Gabriel Faria, Gustavo Lopes, Thiago Rodrigues, Estácio Neto, Thiago Nogueira and Matheus Pereira, a team of researchers from Federal University of Itajubá in Brazil. It presents evaluation of the lightning withstand of switches and cut-out fuses designed to operate on overhead distribution lines. Firstly, the evaluation considers the use of the standard impulse shape (1.2 x 50 µs), representative of direct strikes on the line. In addition, in order to evaluate the lightning withstand with focus on induced overvoltages by side strikes, five non-standard impulse shapes are used for testing the lightning withstand. The results indicate that the critical impulse shape is still the 1.2 x 50 µs for both the components. However, for all the impulse shapes, the lowest lightning withstand values are observed at positive polarity for the switches and at negative polarity for the cut-out fuses, that is, indicating a change of the critical polarity. To analyze this issue, the electric field distribution at the equipment was investigated and the results indicated that the behavior of switches is like that of rod-plane electrode configuration while that of cut-out fuses is like that of rod-rod electrode.
To complete the issue, the fifth and last article appears under the section “Special Report”. It is an updated reprint on an article, earlier published in Wattnow SAIEE magazine, entitled “Power utility perspective on natural ageing and pollution performance of outdoor insulators” and authored by Wallace Vosloo and Richardo Davey from Eskom Research Testing and Development in South Africa. Eskom has for many years followed international guidelines in selecting transmission and distribution insulator products for use in polluted environments, which could validly be applied to glass and porcelain insulators. However, the recent proliferation of non-ceramic (polymeric, resin and coated) insulator products has led to their growing use in South Africa. Appearance of major concerns about their long-term electrical performance and material longevity led to the establishment of an 11, 22, 33, 66 and 132 kV insulator pollution test station at Koeberg Insulator Pollution Test Station (KIPTS) to determine the natural pollution and ageing performance of insulator products. In conjunction with the leakage current measurements, environmental data are monitored, and visual inspections are carried out periodically on each test product at the site. These data are cross correlated with material studies with emphasis placed on identifying generic trends and failure modes. The objective of the research work at KIPTS is to position Eskom as an informed buyer of insulator products and in helping to deal with operational problems. Some results obtained at the station are discussed in this article.
Editorial Jul/Aug 2020
Ongoing revision of IEC Technical Specification 60815 on selection and dimensioning of high-voltage insulators intended for use in polluted conditions seeks a simple and effective solution to this complicated problem
Professor Xidong Liang
Convener of IEC TC36 WG11
Tsinghua University, Beijing China
e-mail: [email protected]
Transmission of electric energy at highest voltage levels (EHV and UHV) continuously increases. The dimensioning of insulator strings and tower windows for overhead lines operating at such voltage levels in contaminated areas is mainly determined by the insulator’s pollution performance, and its proper completion strongly influences line reliability, cost and maintenance procedures.
There are three categories of factors influencing insulator pollution performance, namely (i) pollution condition, (ii) wetting condition and (iii) insulator design. Description of pollution condition includes pollution type, its chemical composition and intensity of deposition. The latter being expressed as equivalent salt deposit density (ESDD) and non-soluble salt deposit density (NSDD). Wetting condition includes intensity of rainfall, wetting frequency, duration of fog or drizzle periods, etc. Insulator design, characterized by its material, shed profile and their separation, also influences the ability to accumulate pollutants as well as the way dry band arcs propagate on its surface. These factors are closely related to each other.
First publication of IEC that provided guidelines for the selection of insulators intended for use in polluted conditions was issued in 1986 (IEC 815). It shortly appeared to require revisions and this process began in 1997. After nine years of discussion, three documents (i.e. IEC TS 60815-1/-2/-3) were issued in 2008, containing Part 1: Definitions, information and general principles, Part 2: Ceramic and glass insulators for ac systems and Part 3: Polymer insulators for ac systems. After another eight years of discussions, the last document IEC TS 60815-4, Part 4: Insulators for dc systems, was issued in 2016.
This very long period necessary for the revision not only reflected the difficulty in formulating the documents but also the challenges encountered by the involved expert panel to understand each other and to compromise on various issues. The selection of insulators for polluted condition does not only relate to the multitude of environmental conditions that various utilities face. The process is also affected by local regulations and habits that altogether impact the design and maintenance of overhead lines and substations. Understanding these diverse influences and compromising on anticipated countermeasures in unaccustomed locations appeared to be very difficult.
Nevertheless, important progress was made in IEC TS 60815-1 regarding the classification of pollution environments. It has introduced quantitative determination of site pollution severity (SPS), made on non-energised standard profile reference insulators. The earlier classification of IEC 815 was based on a qualitative estimation. At present, SPS is defined through measurements of ESDD and NSDD parameters. However, difficulties are also encountered in the new approach – a reduced number of measurement points may result in falsification of SPS description, especially if some of them are incorrect. Many measurement points require, on the other hand, a huge workload. Furthermore, when utilities only focus on the measured ESDD and NSDD, other factors that influence the insulator pollution performance may often be ignored.
In China, for example, the determination of site SPS class is considered as one of the two key factors that allows to properly choose line and substation insulators and this way eliminate large area outages caused by pollution flashovers. Utilities and experts put much effort to correctly define SPS class and experiences on how to measure and analyse the obtained data have been gathered over a long period. These are worth sharing with the international community.
The IEC technical specification postulates three possible approaches in the process of insulator selection and dimensioning. These are as follows:
As the pollution performance is determined by complicated and dynamic interactions between the environment and the insulator, past operational experience (Approach 1) provides the best guideline for insulation selection in the same location and in other places with similar environmental conditions. A period of satisfactory operation of five to ten years can be considered as acceptable. It may, however, not work well when applied in places with different environmental conditions. It should also be noted that the past experience may not work well at the same place or at similar conditions if insulators are of different types.
SPS measurements are recommended and involve environmental research to identify and analyze all possible pollution sources (Approaches 2 and 3). A period of two to three years is normally necessary for saturated pollution accumulation, but measurements over a longer period yield more precise result. Thereafter, interactions between the environment and the insulator can either be represented by laboratory testing or by use of several correction factors.
As already mentioned, the insulator design itself influences its pollution performance and this fact is not emphasised strongly enough in the current IEC specification. Accumulation of pollution and development of dry band arc activity are strongly affected by shed profile. When the profile of the candidate insulator is like that of the reference insulator, its required dimensioning based on unified specific creepage distance (USCD) may be chosen similar to the reference unified specific creepage distance (RUSCD). This rule should, however, be applied carefully. Even for standard profile insulators of high mechanical rating (³300 kN), the USCD is different from RUSCD of reference insulators with low mechanical ratings (120 or 160 kN) for the same SPS class. Defining precise values of correction factors for different shed profiles have been tried but found to be very difficult. Instead, many artificial pollution tests were conducted in China to find the necessary USCD after conversion of field measured ESDD to salt deposit density needed for insulator testing in artificial pollution chambers.
The target of the revision that began in 1997 was to adjust the IEC specification from being only applicable for porcelain/glass insulators working under ac stress to more general recommendations that will be valid for porcelain/glass and composite insulators operating under ac and dc. Although uncertainties still exist concerning aging and dynamic hydrophobicity behaviour, the use of silicone composite insulators, called “anti-pollution insulators” in China, has tremendously increased during the past 10 to 20 years. Wide application of SR composite insulators in existing and new EHV and UHV ac and dc transmission lines is the other important reason for eliminating large area outages caused by pollution flashovers.
The considerations presented above show the complexity of the process of selecting insulators intended for work under ac voltage. If the voltage changes to dc, the situation becomes even more challenging. Experiences from such applications are scarce and pollution accumulation and the resulting propagation of dry band arcs on the insulator surface differ significantly. Attempts to solve the challenge by use of correction factors to account for pollution accumulation under dc and then following the procedure for ac have shown a very limited progress because of remarkable data dispersion. Gathering operation experiences under dc and different kinds of polluted environment are crucial and new ideas born at researcher’s desks must be verified in real field conditions.
Bringing together knowledge on experiences gained in various countries is, therefore, important for the ongoing revision of IEC TS 60815. The decision on initiation of this work was taken during the general meeting of IEC Technical Committee 36 in Frankfurt, autumn 2016. The revision work was started in 2017 and I realize, as the convener of the working group responsible for it, how difficult is this task. Experiences and facts from all parts of the world must be shared and melted into a generally accepted knowledge. The ideal solution would be to provide a simple and effective key to engineers to work with. However, facing the complicated reality has no shortcuts, that is, finding this solution must be reached stepwise. A Chinese proverb states, ‘it is better to teach one to fish, rather than giving him a fish’.
News from Japan
Development of a New On-line Partial Discharge Monitoring System
With the advent of sophisticated electronic power control systems, the power efficiencies of electric and electronic devices and machines have been improved significantly. This improvement in efficiency is quite obvious in rotating electric machines such as motors. In other words, electric or hybrid electric vehicles would not gain so great a popularity, if motors in such vehicles were driven or controlled without using power electronic devices. One of the most typical and most important power electronic device systems is a converter system, which is composed of an inverter circuit that converts dc to ac and a converter circuit that converts ac to dc.
Although a converter system is quite powerful and useful as mentioned above, it is not friendly to electrical insulation. That is, output voltages from a converter system usually have waveforms such as the one shown in Figure 1 . It is clearly understandable by doing Fourier transform that those waveforms are composed of many components with quite rapidly rising fronts and falling tails. Partial discharges (PDs) generally occur actively when such voltages are applied. This means that generators, motors, or any other power devices controlled by a converter system have many chances of being attacked by PDs. This, in turn, means that the importance of adequate monitoring of PDs has recently been growing rapidly.Although the generation of PDs in motors in electric vehicles would be a matter of concern, PD monitoring has long been an affair of great importance for high voltage rotating electric machines. Especially for rotating machines installed in power grids, natural renewables would be another source of concern. Namely, for balancing the fluctuating outputs from renewables, frequent start-and-stop operations of rotating machines would be necessary. This may incur the degradation of electrical insulation of rotating machines.
Until recently, the degree of insulation failure caused by PDs in rotating machines is checked off-line while the machines are stopped. However, to conduct off-line PD monitoring for a rotating machine, we have to disconnect the machine from the wiring, and to connect it to a measuring circuit. This needs manpower and a high cost. In addition, neither thermal stresses like heat nor mechanical stresses like various vibrations and forces are present unless the machines are working. In addition, if a rotating machine is on-line, the potential difference applied to a winding coil in the machine is as determined by the operating voltage. However, if we do an off-line PD test, an arbitrary test voltage would be applied. That is, the situation around a rotating machine is usually very different between the on-line and off-line states.
With these backgrounds, Soken Electric Co., Ltd., Chofu, West of Tokyo, has developed a novel on-line monitoring method of detecting the occurrence of PDs in motors or generators. Regarding this, this short article introduces a brief outline of the new method.
One major problem to conduct on-line monitoring of PDs is the generation of electromagnetic noise. It is usually very difficult to discriminate PDs from electromagnetic signals with much noise, since PD signals very often possess similar characteristics to noise signal. Figure 2 shows a schematic diagram of component devices of the new on-line PD monitoring system, DAC-PD-10. The monitoring system is mainly composed of three identical sets of PD detection systems. Each detection system consists of a coupling capacitor, a PD analyzer, a dc power source, an electro-optic converter, a co-axial cable, and an optical fiber cable. Optical signals from the three detection systems are transmitted to a personal computer via an optical interface. Each coupling capacitor is connected to each phase of a rotating machine as shown in Figure 2. Therefore, if PDs occur in one of the coils of three phases, electromagnetic signals generated by the PDs are detected directly by the PD detection system connected in the PD-occurring phase. At the same time, signals are also detected by two other detection systems in the form of interference noise. If we can recognize the difference between the signals generated by PDs and those of interference noise, the phase where PD occurred can be identified. This is the principle of the developed PD monitoring systems.
Figure 3 shows a schematic diagram of a source, which may generate common-mode noise signals. For securing the safety of an operator, who is doing the measurement of PDs, each PD detection device and its electrooptic converter are placed far enough away with a long connecting cable. Consequently, this cable and the earth forms a large ground loop. If electromagnetic waves from any source, regardless of whether they are internal or external like outside broadcast or communication waves, pass through the loop, common-mode noise will be induced. To prevent the occurrence of such noise, optical fiber cables are used in this system, as shown in Figure 2. The optical fiber is not electrically conductive and can isolate the optical interface from high voltage sites. Therefore, any common noise would not enter the optical interface. In addition, batteries are used as the dc power source of the PD converters to eliminate noise that may penetrate from ac commercial power lines. Furthermore, noise generated in converter-fed rotating machines usually has specific frequencies. The developed PD monitoring system can select measurement frequencies, which enables us to pick up or take off such frequencies selectively.
The method to find the coil winding where PDs occur will be explained briefly. Here, we assume that PDs occur in the voltage phase U or along the coil U. Then, PD signals will be detected directly in the phase U, which generally have relatively large amplitudes. In addition to the phase U, the PD signals will also be detected with a smaller amplitude in the phases V and W, as the signals will be transmitted to the two phases. On the other hand, common-mode noise should generate signals with the same amplitude in all the three phases.
Therefore, if PDs are generated in phase U in the presence of external or common-mode noise, we will have a three-phase diagram like the one shown in Figure 4. In this figure, the three axes represent the signal magnitudes in mV in phases U, V, and W. The color of each dot represents the frequency of the appearance of PD signals; ‘blue’ is fewest, which is followed by ‘green’ and then ‘yellow’, while ‘red’ means that the PD signals appear most frequently. Regarding this, we can recognize in Figure 4 that there are four red clusters where PD signals appear very frequently, as indicated by red arrows.
The biggest cluster at the center seems due to noise. This can be confirmed by making a two-dimensional graph showing the signal intensity as a function of phase angle of the sinusoidal voltage applied to the sample. In the case of the biggest cluster shown in Figure 4, the phase-resolved distributions of signal intensities or f–Q–n distributions of signals in the voltage phases U, V, and W are as shown in Figure 5. Here, f is the phase angle of the sinusoidal voltage, Q is the discharge amplitude in mV (or in C), and n is the frequency of appearance. The thin red curve in each figure is the voltage waveform. It is clearly shown that signals appear almost equally in all the voltage phases. This strongly indicates that these signals are due to external noise.
In contrast, the intensities of signals in the cluster that appeared closest to the axis U have phase-resolved distributions shown in Figure 6. It is clearly indicated that the signals in this cluster are due to the occurrence of PDs in coil U.
This is the basic principle of identifying the coil or the voltage phase where PDs occur. A similar method was reported more than 10 years ago . Therefore, the principle itself is known well and is not new. However, the developed system has the following feature. Namely, if we do an on-line PD monitoring test by this system, a three-phase diagram like the one shown in Figure 4 and phase-resolved signal distributions like those shown in Figure 5 can be acquired easily. Then, we can conduct a more detailed analysis by doing off-line tests. The company claims that PD monitoring can be done with higher reliability by this method than conducting usual on-line monitoring.
This article was completed in cooperation with Mr. Sadayuki Kanazawa of Soken Electric Co., Ltd.
 Y. Ohki, “News from Japan – Development of an Innovative Repetitive Impulse Voltage Generator”, IEEE Electr. Insul. Mag., Vol.34, No.5, pp.50-53, 2018.
 W. Koltunowicz and R. Plath, “Synchronous Multi-channel PD Measurements”, IEEE Trans. Dielectr. Electr. Insul., Vol.15, No.6, pp.1715-1723, 2008.
Magnetic Field Measurement with Applications to Modern Power Grids
Q. Huang, A.H. Khawaja, Y. Chen, J. Li
John Wiley & Sons, Inc.
111 River Street
Hoboken, NJ 07030
314p. 129€ (Hardcover), 2020
Magnetic fields are created from current flow in conductors. Power flow in transmission and distribution systems generate a magnetic field which can be measured. By measuring and examining thresholds and patterns in a magnetic field, it is possible to determine certain conditions that relate to some desired predictive diagnostic or measured quantity. This book focuses on the most recent techniques in magnetic field-based measurement technology used to monitor power grids. Sensor technology is anticipated to be one key enabler for modernizing the electrical grid, especially for two-way power flow between consumer and the utility or other consumers, since accurate live data is necessary to provide dynamic control and safe operation of a power system utilizing distributed energy resources (DERs).
This book begins by providing the reader with the basic fundamentals of magnetism and magnetic fields with application to the power grid. Magnetic sensors, in particular magneto-resistive (MR) sensors, are reviewed. The particular types of sensors include discussions on anisotropic magneto-resistance (AMR), giant magneto-resistance (GMR), tunnel magneto-resistance (TMR), and colossal magneto-resistance (CMR) sensors. Noise and noise shielding of these sensors are also discussed.
The book continues with proposed applications of magnetic-field-based solutions for areas of the entire distribution system including generation, transformation (substations), transmission, and distribution. Application examples are given showing how MR sensing methods can be used for each part of the power grid system to obtain an electrical signal that measures or monitors some desired system parameter or safety aspect such as fault condition, or failing motor, or reverse power flow, for example. Some of these examples also show how MR sensing can be used to measure conductor sag, determine fault locations in transmission lines, monitor motor speed, power line and motor health diagnostics, power measurements, and home energy monitoring.
The remainder of the book briefly describes the future outlook for magnetic field sensing technology for each part of the power grid system.
While there is some very interesting theory presented in this book, with claims for a variety of sensing applications in the power grid systems, actual real-world application is not presented. Much, if not all, of the work presented was under laboratory based conditions. Actual real-world rigors of a power grid system are not described. Also, for many applications, these methods would appear to apply to the existing legacy power grid system and not only a “smart grid” system, which is never actually defined. There are also no comparisons to existing or alternative ways for measuring the same quantities or obtaining the same desired end result.
Nonetheless, power system engineers and engineers who are interested in designing magnetic based sensing technologies for power systems would be interested in this book. It provides many ideas that use magnetic field sensing as well as a good background on various MR sensor types.
College Physics Essentials – Volume One: and Volume Two
Taylor & Francis Group
6000 Broken Sound Parkway – NW, Suite 300
Boca Raton, FL 33487-2742
806p. $144 (Hardcover), 2020
This two volume set covers the traditional topics for an undergraduate college physics course. Volume one covers mechanics, heat, and thermodynamics. Volume two covers electricity, atomic, nuclear, and quantum physics.
What sets these books apart from other college physics textbooks are the follow-up and thinking it through exercises contained in each chapter. After presenting a topic such as quantization – Plank’s hypothesis giving the equations and explanation for the hypothesis, as typically done in textbooks, there are examples to help the reader think about what was just presented and the significance of the equations. Then there is also a follow-up exercise that provides a backstory about the material and provides practical observations and/or modern application of the theory including conceptual reasoning and quantitative reasoning methods. These added materials can really help a reader relate and better understand the theory or fundamental equations being presented.
These volumes would also be of interest to college professors who teach physics since they are not only well-written textbooks on physics with the needed materials for an undergraduate class in physics and lots of illustrations, but they also have a nice blend of questions and exercises at the end of each chapter consisting of multiple choice, conceptual, and exercises categorized by the degree of difficulty. Although, some of the answers to the questions are in the back of the book. There are also handy appendices at the end of each volume containing information such as mathematical relations and tables of data.
Distributed Fiber Optic Sensing and Dynamic Rating of Power Cables
S. Cherukupalli and G.J. Anders
445 Hoes Lane
Piscataway, NJ 08854
John Wiley & Sons, Inc.
111 River Street
Hoboken, NJ 07030
235p. $135 (Hardcover), 2020
Dynamic temperature sensing (DTS) systems use fiber optic (FO) cables, embedded along the length of a power cable, and exploit the fiber’s optical properties as a method for measuring temperature along the length of a power transmission line. This enables a utility to monitor the cable temperature hot spots to insure the cable is not overheated and that the power cable can be utilized to its full potential without having to de-rate the cable because the temperature is not known. This technology is also used in many other applications such as monitoring strain in composite aircraft wings, strain in the concrete of a large dam or bridge structure, underground mine shafts, and to measure current and voltage on high-voltage transmission lines.
This book presents a comprehensive view of the fundamentals of DTS and its application in electric power cables. The authors provide a wonderful review of this technology and its application, primarily focused on monitoring electric power transmission cables. It is intended to help the potential users of the technology (i.e. cable engineers), manufacturers of the DTS equipment, and the cable manufacturers understand the physics, advantages, and limitations of the technology. It is used to showcase the benefits users can get from these systems along with all the technical details and practical information an engineer would want to see.
The main topics that focus on electric power cables begin by describing the advantages and the disadvantages of distributed temperature sensing for power cables using FO technology. The fundamental physics of DTS is explained including background on Rayleigh scattering, Raman spectroscopy, Brillouin scattering and time domain reflectometry (TDR), the methods used to measure temperature in the FO cable. These methods are used to illustrate the concept of distributed temperature sensing and the design of a DTS system. The design and construction of FO cables, standards for testing FO cables, aging and maintenance are all reviewed including discussions on the important topic of protection and placement of the FO cables in a power cable.
Moving to the cable designer’s area, the authors describe the details of power cable types and how FO cables are integrated into the power cables. One very interesting area described includes manufacturing challenges. Descriptions on how a FO cable could be incorporated in a power cable are given and the challenges encountered, certainly appreciated by those in the industry. This would have been even better to include even more details and other possible methods or even speculate on other possible ways to incorporate the fiber.
An explanation of the results displayed by a DTS system gives the user of the system an idea of what to expect from the results. A general description of these systems familiarizes the reader with DTS systems, general requirements, software and calibration of a DTS system. Further information is provided for how the temperature data may be used to optimize the transmission of power along a transmission line to forecast circuit ratings based on dynamic temperature measurements from the DTS system.
Examples are given for the application of DTS systems in a utility environment including retrofitting FO cables into existing power lines. Other potential future uses are also briefly described for strain measurements and acoustic application in power cables.
This very well-written book clearly addresses the fundamental workings of DTS systems and the application of DTS to power cable temperature monitoring. Our readers, who work in designing high-voltage transmission line systems, would certainly benefit from understanding the capabilities of this technology for utilizing the full potential of their cables. One area that is limiting the acceptance of such systems is from the lack of standardization. More use cases and practical implementation of DTS systems standards will help to accelerate the adoption of this technology and reduce costs and create even more innovation in this technology.
Lens Design – A Practical Guide
Taylor & Francis Group
6000 Broken Sound Parkway – NW, Suite 300
Boca Raton, FL 33487-2742
371p. $245 (Softcover), 2017
Lenses are used for manipulating electromagnetic radiation, often, but not necessarily, visible radiation or light. The design of lenses can be quite complicated and involve intractable equations. Except for very simple designs, lenses are typically designed using commercially available software such as Zemax and others. Zemax is considered an entry level program, and is widely used because it can be used to solve most lens design problems and it is easier to use than other optical lens design programs. However, even Zemax is not easy for the novice designer to learn. Also, relying only on software, without understanding the fundamentals can lead to a poor understanding of a design and lead to poor lens performance. This book can help the reader understand the fundamentals of optical lens design and gain very practical design advice from a leading expert in lens design.
This is where this book excels. The author has taken his many years of lens design experience and condensed it into this book. In addition to presenting the fundamentals of optics, he presents practical recommendations for lens design and guides the reader through the setup and solutions using the Zemax optical lens design software, helping the reader gain a quick understanding of the software and feel more comfortable in using the software.
The first part of the book reviews optics fundamentals and fundamental lens phenomena including aberrations, optical glasses, and lens parameters. The majority of the book then covers the lens design process from start to finish. This section provides all the details necessary to design a lens system including optimizing the design, and putting the final touches on the design such as eliminating/reducing ghost images, selecting glass types, and common mistakes made when optimizing the design. To further illustrate the process, the author presents various case studies and shows exactly how to design these systems, step-by-step. Some lens systems described are singlets for focusing, eyepieces, microscope objectives, binoculars, gun scopes, camera lenses, projector lenses, aspheric, cylindrical, and reflective optic lens designs.
Other topics cover raytracing design with examples, tolerance analysis, and design for production with information on costing, cost versus tolerance, and cost versus quantity.
Anyone new to optical lens design or those wanting to learn how to design optical lenses and learn about Zemax lens design software would find this book very useful. It can give you the guidance needed to start creating your own lenses and provide you with a good understanding of the fundamentals and the ability to confidently use the Zemax software.
The Finite Element Method in Engineering, 6th Edition
S. S. Rao
The Boulevard, Langford Lane
Kidlington, Oxford OX5 1GB, UK
50 Hampshire Street, 5th Floor
Cambridge, MA 02139
780p. $130 (Softcover), 2018
The finite element method (FEM) finds a solution to a complicated problem by replacing it with a simpler one. The FEM uses many small, interconnected sub-regions called elements to create an approximation to a surface or volume. Solutions to the complicated problem are obtained by solving a set of equations for each element and combining the elements together to find the final solution using a set of interlinked equations.
This book introduces the various aspects of the FEM as it applies to solving engineering problems. Each aspect of FEM is described from basic principles with simple clear examples and illustrations. Commercial FEM software packages, ABAQUS and ANSYS, are also introduced. In addition, several MATLAB programs are provided along with examples to illustrate the use of the programs.
After an introduction and overview to FEM, the book can be broken down into three major sections. The first section covers the basic finite element procedure and the solution to the resulting equations. The number and types of elements are discussed along with interpolation models, boundary conditions, element properties, and solutions to the finite element equations.
The second section shows how to apply the FEM for solid and structural mechanics problems (internal and external equilibrium, stress-strain, strain-displacement relations). Trusses, beams, plate elements, 3D, and dynamic analysis, including free and forced vibration of structural problems are described.
The third section covers applications in heat transfer (conduction, convection, and radiation) for 1D, 2D, and 3D solutions. Both steady-state and transient problems are illustrated. Fluid mechanics problems are also presented for incompressible viscous flows as well as non-Newtonian fluids. A brief introduction to the use of commercial software programs, namely ABAQUS, ANSYS, and MATLAB are illustrated along with some examples of mechanical structural problems.
The book is clear, concise and well-illustrated with extensive references at the end of each chapter for further study. Readers who are interested in understanding the fundamentals of FEM would be interested in this book. Teachers may also be very interested in this book for use in an undergraduate engineering class in FEM. There are questions at the end of each chapter and a solutions manual with additional materials available for instructors from the publisher.
Introduction to Phase Diagrams in Materials Science and Engineering
World Scientific Publishing Co.
5 Toh Tuck Link
27 Warren Street
Hackensack, NJ 07601
186p. $78 (Softcover), 2019
A phase diagram is a graphical representation of the combinations of temperature (T), pressure (P), composition, or other variables for which specific phases exist at equilibrium. Phase diagrams show what phases exist at equilibrium and what phase transformations we can expect when we change one of the parameters of the system (T, P, composition). Typically, in material science and engineering, phase diagrams are often associated with an alloy of two or three metallic materials corresponding to binary and ternary phase diagrams respectively. These diagrams show phase transitions and crystalline structure of these metals at different concentrations and temperatures. For example, these graphs can be used to know the parameters necessary for hardening steels, make lower melting point materials than either material alone, or change the crystalline structure to toughen a material.
Material scientists and anyone developing alloys need to understand how to read and use phase diagrams. This introduction to phase diagrams provides the reader with these fundamentals for both binary and ternary alloys.
The book provides the bare essentials for understanding phase diagrams by providing a basic introduction to metallography and Gibbs phase rule. Constructing binary phase diagrams and the use of tie lines is recommended by the author to help beginners visualize the various phases involved. Examples of binary phase diagrams are used to illustrate key points in the graph such as eutectic points and phase changes as a function of component concentration.
Heat treatment for aluminum and steels includes aging and precipitation hardening of aluminum alloys, including precipitates are covered. Heat treatments for steels reviews iron-carbon (Fe-C) phase diagrams, quenching, martensite transformations, tempering, and case hardening – all important techniques widely used today.
A chapter on the thermodynamics of binary phase diagrams is included for those who really want to understand the physics behind phase changes. However, this material is not absolutely necessary to read since you can still understand how to read and use phase diagrams without understanding the physics behind the changes.
The last part of the book deals with teaching ternary phase diagrams. These are far more complex than binary compound diagrams, so the author uses color drawings in two-dimensions (2D) and three-dimensions (3D) to help the reader better understand what is happening in the phase diagram. Examples of ternary compounds include important alloys such as stainless steels (Fe-Cr-Ni). These illustrations greatly help one to visualize important points described in each diagram and clarifies difficult processes by also including a step-by-step description of key points through the graph. Complex graphs are built-up by starting with a simpler 2D graph and building upon that by adding other parts until the complete ternary phase diagram is formed.
For material scientists and engineers who need to understand phase diagrams, this book can provide you with that basic knowledge that will make you an expert at reading these sometimes very complicated graphs.
Wearable Solar Cell Systems
Taylor & Francis Group
6000 Broken Sound Parkway – NW, Suite 300
Boca Raton, FL 33487-2742
163p. $71.96 (Hardcover), 2020
Today’s solar cells (aka photovoltaic (PV) cells) are frequently associated with large solar panels on rooftops or large arrays in the fields for electric utilities. But there are many other applications for these devices that include wearable/portable applications. This book, after reviewing the fundamentals of solar cells and basic power conversion systems for converting the PV energy into desired current and voltage levels, provides some comparisons of various cell materials for wearable devices powered by PV cells.
After covering the fundamentals of light and the basic properties of PV cells, the book goes on to describe first generation (mono, poly, and amorphous crystalline Si), second generation (GaAs, CdTe, and CuIn-GaSe), and third generation (organic, dye-sensitized, perovskites, and quantum-dot) PV cell technologies. Basic descriptions and fundamental mechanisms are given for light to electric energy conversion for each material.
The book then continues with descriptions of PV cell arrays, maximum power-point-tracking (MPPT), and array reconfiguration such as bending or warping cells into shapes other than flat. The very basics of DC-DC converters are also described which include boost, buck, and buck-boost converter topologies. Wearable and portable technologies including cell phones and wearable devices on the ear, wrist, head, and smart clothing are discussed for existing products on the market including commonly used products such as cell phones, fitness trackers, earphones, and head mounted displays but unfortunately there is no information provided as to how these devices can be powered by solar cells in a practical application. The final few pages provide a list comparing the efficiencies of various PV materials under a variety of lighting conditions, assuming that wearable electronics could be used indoors or outdoors each having different light spectrums and intensities. Flexibility of various cell materials are also compared. There is very little detail and only a short mention of charge controller and battery considerations. No examples of wearable devices powered by PV cells are provided.
This is a book for students or interested readers who want to learn some basic fundamentals of PV cells, the different types of cells, and some of the considerations when designing with PV cells for wearable applications.