G S N Raju Electromagnetic Field Theory And Transmission Linesl
Janet Denzel
The best book for understanding the fundamentals of electromagnetic theory is "Engineering Electromagnetics" by William H. Hayt and John A. Buck. This book covers all the essential concepts of electromagnetic theory and provides clear explanations and examples.
G S N Raju Electromagnetic Field Theory And Transmission Linesl
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One highly recommended book for understanding the principles of transmission lines is "Transmission Lines and Networks" by Umesh Sinha. This book covers both the theoretical and practical aspects of transmission lines and is suitable for beginners as well as advanced readers.
"Electromagnetic Waves and Transmission Lines" by G. S. N. Raju is a comprehensive book that covers both electromagnetic theory and transmission lines in-depth. It includes detailed explanations, numerous examples, and practice problems to aid in understanding the concepts.
"Introduction to Electromagnetic Compatibility" by Clayton R. Paul is highly recommended for self-study in electromagnetic theory and transmission lines. This book provides a thorough understanding of the basics and also covers advanced topics, making it suitable for self-study.
Yes, most of these books have online resources and supplements available, such as solution manuals, practice problems, and lecture slides. Some also have interactive simulations and demonstrations to further enhance understanding. Check the publisher's website or the author's website for more information.
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Feature papers represent the most advanced research with significant potential for high impact in the field. A FeaturePaper should be a substantial original Article that involves several techniques or approaches, provides an outlook forfuture research directions and describes possible research applications.
Abstract:With the development of smart grids, the application of localized relay protection devices has greatly reduced the distance between the secondary equipment and the primary equipment. The secondary equipment will be in a more complex electromagnetic environment during the operation of the GIS disconnector. The present study takes the multi-path electromagnetic disturbance on the secondary cable caused by the disconnector switching operation of the domestic 1000 kV ultra-high voltage GIS test circuit as the research background, solves the field-line coupling problem based on the finite integral technique, and combines the multi-conductor transmission line theory to solve the radiation disturbance and obtains its influencing factors. The results demonstrate that the radiated disturbance accounted for 16% of the overall electromagnetic disturbance when both ends of the shielding layer are grounded. The use of grounding at both ends of the shielding layer, reducing the height of the secondary cable wiring, avoiding the parallel arrangement of the secondary cables and the GIS pipe mother, and installing a low-pass filter, have different levels of suppression effects on electromagnetic disturbances. The research results will guide the reasonable arrangement of secondary cables in GIS substations to some extent and have reference significance for the protection of secondary equipment.Keywords: disconnector switching operation; broadband equivalent circuit model; finite integration technique; overall electromagnetic disturbance; suppression measures
Climate change has deleteriously affected terrestrial ecosystems. Its concomitant recurrent episodes of droughts and extreme heat have led to environmental conditions, which are conducive to the occurrence of frequent large wildfires [1]. Occasionally, the fires burn under or in propinquity to high-voltage transmission lines when there is luxuriant re-sprouted vegetation in right-of-way, e.g. such as shown in Figure 1. This affects the reliability of electrical power supply as this may lead to the utility disruption. A significant number of fire-induced power outages have been reported in several countries [2] [3] [4]. For instance, in South Africa, vegetation fires are responsible for about 22% of annual transmission line faults [4].
The faults are normally due to short-circuiting between conductor phases or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. Research has shown that wildfire plumes provide a conductive path for the discharge [2] [3]. The conductor-to-ground flashover may possibly be a safety concern for fire-fighters who may be within an arcing zone during suppression [2].
1) Reduced air density model: heat from the fires increases temperature in the air gap (i.e., between energised conductors and the ground). This lowers the air density and consequently decreases its insulation strength by up to 50% [7].
2) Particle initiated flashover: thermal plumes from the vegetation fires carry soot and ash particles aloft. The particles distort and intensify electric field in the air gap. This consequently leads to power loss when breakdown electric field is exceeded [3].
The fire-induced particle initiated flashover model and its associated critical flashover voltage has been clearly elucidated by several researchers, e.g., [8] [9]. The theory of reduced air density has been expounded by (Robledo-Martinez & Guzman, [7] ). However, very few attempts have been made to explicate flame conductivity model, e.g. in [5]. Even though there is no consensus as to which model is predominant, several researchers acknowledge that temperature and ionisation are major factors that influence to fire-induced flashover, e.g. in Wu et al. [10]. Moreover, it has been illustrated from field experiments that flame conductivity plays major role in fire-induced flashover.
Several experiments have been conducted to measure breakdown voltage for vegetation fires under different conditions, e.g. [3] and [6]. Nevertheless, there is paucity of experimental data on breakdown electric field in flame medium. Maabong et al. [11] observe that breakdown electric field strength is crucial for initiation of electrical discharge mechanism for conduction in fluids or in streamers propagation in flames. The data is essential for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. Despite this, there is paucity of data on breakdown electric field strength for vegetation fires.
It is intended in the study to: 1) measure dielectric breakdown electric field for vegetation fuel flames at atmospheric pressure and different combustion temperatures; 2) derive an empirical expression that relates breakdown electric field with vegetation fuel flame temperature. The expression is compared to similar ones in for other gas mixtures, e.g. Nitrogen, Oxygen and Carbon dioxide. Section 2 of the manuscript discusses ionization vegetation fuel flames. Classical electrodynamics and electrical discharge theories are applied to derive an expression for critical electric field in Section 3. In Section 4, combustion experiments to measure breakdown electric field and chemical equilibrium calculations are described. The results are discussed in Section 5 and the manuscript is concluded in Section 6 with a suggestion of future research directions on the subject.
When subjected to intense heat, vegetation undergoes three interconnected temperature-dependent decomposition stages (Morvan & Dupuy, [12] ). The decomposition stages lead to the development of fire and influence its rate of spread through vegetation. The stages are shown in Figure 2 as: drying (A), pyrolysis (B) and char oxidation (C).
The first reactant in Equation (1) is the average formula for biomass material. The excess air ratio is depicted by λ. The equation illustrates several by-products of incomplete combustion (intermediates) which are released into the atmosphere in form of a thermal plume. The intermediates include inorganic salts of alkalis, carbon monoxide, oxides of nitrogen, pyrogenic (organic and black) carbon, polycyclic aromatic hydrocarbons as well as volatile organic compounds, which are not shown in the equation (Reid et al., [15] ).
Latham [16] identifies two major mechanisms that produce charged particles in vegetative fuel flames. These processes are flame temperature dependent and have been identified as thermal and chemi-ionization.
Vegetative fuel fires are considered impure hydrocarbon diffusion flames seeded with Alkali-Alkaline Earth Metals (A-AEM) based nutrients [17]. In plants, about 90% of A-AEM exist in aqueous form, e.g., as companions of anions such as chlorides and sulphates or as cations of complexes such lactone and carbonyl forming weak ionic bonds. The A-AEM species could also exist as discrete salt particles in plants organic matrix, e.g. calcium oxalate.
During flaming a significant number of A-AEMs are volatilised from a thermally decomposing vegetative matter and drawn into the reaction zone by local convective currents of the fire. A major fraction of the volatilised species is potassium-based salts [18]. However, at temperatures lower than 500 K, charcoal is formed at the wood surface and this traps A-AEMs in organic matrix voids. The trapped A-AEMs react with functional groups such as carboxyl and carbonyl (O-C-) on the inner charcoal surface to form Charcoal Matrix Attached Alkalis (CharM-A). As the combustion temperature rises above 500 K, cellulose and lignin rapidly disintegrate, a process which results in the formation of a highly reactive hydrogen radical (H). The radical reacts the CharM-A species to give A-AEM atoms according to the following reaction equation (Okuno et al., [19] ):
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