Power Carrying Capacity Research Articles

Stress-Strain and Resistance-Strain Hysteresis in Single-Wall Carbon Nanotube Films for Stretchable Battery Electrodes

The need to protect the vulnerable and limited resources that are naturally available while meeting the growing energy demand of the world makes the sustainable development of renewable energy of paramount importance. To address these needs, a new type of battery electrode has been developed at Honda Research Institute (HRI), based on free-standing single-wall carbon nanotube (SWNT) films containing active battery materials as dispersed nanoparticles. The SWNT films provide both mechanical support and electrical conductivity, removing the need for metal electrodes (increasing the energy density of the battery) and binder materials (making the process environmentally friendly).Under cyclic strain, the SWNT-based electrodes show hysteretic behaviors in both stress-strain and electrical resistance-strain relations. The electrical resistance-strain behavior shows a different trend from the previously observed behavior on 2D SWNT films (on elastic substrate). We hypothesize that this change can be attributed to the differences in the SWNT network structures in the 2D and 3D films. To understand the microscopic origin of the hysteresis, we performed coarse-grained molecular statics (CGMS) simulations of the SWNT film. The simulations show that the intrinsic Van der Waals interaction between SWNTs is responsible for the observed robust mechanical properties of the electrodes. In addition, our study also reveals that the sparsity of the 3D morphology results in the current being carried across the simulation box only by a few paths. As a consequence, the resistance hysteresis is governed entirely by the change in the power-carrying capacity of the network due to the breaking and formation of contacts between the SWNTs during loading-unloading. The qualitative nature of the resistance-strain hysteresis can thus be attributed to the rapid formation of inter-nanotube contacts, as the nanotube bundles (elongated by initial loading) buckle during unloading.

Reliability Improvement of Composite Power System using UPFC

Together with quality power supply criteria, Composite Power System (CPS) reliability is also one of the important aspects of deciding the security of the CPS for a given load demand. In the current paper, the reliability of CPS is evaluated. The Newton Raphson (NR) approach is implemented in Power System Simulation for Engineering (PSSE) software to take into account, the load flows, then the power available to the load points, to evaluate the reliability of CPS. Newton Raphson NR Method was implemented by considering different contingencies of the CPS. Power available to the load points obtained by the NR method is critical in identifying the successful operating state of the CPS. Expected Load Curtailment (ELC), Number of Load Curtailment (NLC), Expected Energy Not Supplied (EENS), and Severity Index (SI) are the crucial dependability indices that are assessed. The main objective of the Reliability evaluation of the CPS is to investigate the scope for the improvement of reliability and explore the possible schemes to improve CPS reliability. The Unified Power Flow Controller (UPFC) one of the Flexible AC Transmission Systems is incorporated into the CPS to analyze the improvement in the reliability of the system. Further, the effect of UPFC on the power-carrying capacity of the lines under contingency conditions, resulting in the failure mode of CPS operation is examined. Improvement in the reliability indices of the system is observed due to UPFC incorporation.

COMPARATIVE ANALYSIS OF SIX PHASE INDUCTION MOTOR

In recent years, AC induction motors have replaced DC motor. The most important reason for this is that DC motors have a mechanical brush and commutator system that is subject to wear and tear over time. While DC motor drivers need a lot of maintenance due to this system, induction motors do not require almost any maintenance since this system is not available. In recent years, technological advances in the field of multiphase induction motors have led to a significant evolution. A lot of research has been done around the world and a lot of new and interesting developments have been reported to the literature. This paper provides information about six-phase induction. In addition, what kind of advantages the concept of multiphase provides and how this structure is formed contains information about them. The six-phase induction motor will be simulated through the MATLAB/SIMULINK package program and compare with three phase induction motor. Both motors were run in simulation using the same parameters. At the end of the simulation, current, moment and speed graphs of the six-phase induction motor and three-phase induction motor will be drawn according to time. The study also included equations used during modeling and equivalent circuits belonging to a six-phase induction motor. It has been graphically shown that a six-phase induction motor is more advantageous than a three-phase motor. For example, in six-phase induction motors, the transition time to a continuous state is shorter. In addition, while the frequency of torque vibration increases, its amplitude decreases, the current value of each phase decreases, the stator copper losses are less than the three-phase induction motor. In motors, usually the power needed is divided by the number of phases. So the more phases there are, the greater the power carrying capacity. Today, multi-phase induction motor drives are used in special applications such as electric vehicles, space technology, aerospace applications, as moving power on ships, electric trains, which require high reliability and power.

Prevention of Load Encroachment Using Model Predictive Control

Tripping of distance relays due to load encroachment is one of the common causes behind major disturbances occur in power systems. Several techniques have been presented in literature to differentiate an occurrence of load encroachment and a fault in a system. However, once an event of load encroachment is observed, loading condition of the power system must be rescheduled to avoid any undesired relay tripping. This paper proposes a receding-horizon Model Predictive Control (MPC) strategy to change load and generation of a power system optimally to take the apparent impedance seen by vulnerable distance relays away from their zone-3 boundaries. To apply MPC technique, a linear state-space model of power system is developed using sensitivity analysis. Rescheduled load and generation are found by minimizing the total cost required for the change, owing to the constraints of power balance, power carrying capacity of lines and relay operational margins. During step changes in inputs, adequate time gap is provided to ensure the stability of the power system. An oscillation detection technique is developed for the above purpose. Several case studies have been presented at the end to demonstrate the performance of the proposed technique under stressed operating conditions.

О допустимой мощности автономного формирователя импульсного электромагнитного поля на основе мощного сверхвысокочастотного генератора.

О допустимой мощности автономного формирователя импульсного электромагнитного поля на основе мощного сверхвысокочастотного генератора.

Enhancement of Power Transfer Capacity and Transmission Efficiency using SSSC

The power demand is increasing globally at a higher rate than the possible increase in the generation. The increased demand requierements put additional burdon on the existing transmission lines and sometimes burdoned beyond their power carrying capacities. Increase in power demand either due modernization of power system, industrialization leads to congestion problem and abruptly affects the stable and reliable operation of power system. Redesign and reconstruction of power system according to load requirements everytime is not an economical and viable solution. Other possible solution to the problem is use of FACTS devices. The use of FACTS devices the problems like increase in load demand, high losses in transmission line and dip in receiving end voltage can be eliminated or easily tackeled. In this paper, Static Synchronous Series Compensator as one of FACTS device has been used for improvement of voltage profile of different buses and power carrying capacity of the transmission lines. The main objective of this paper is to make a comparative investigation between compensated and uncompensated power system in terms of enhancement of power carrying capacity with low losses and improvement of voltage profiles of buses in the transmission network. The performance of uncompensated power system has been compared with compensated power system with the use of MATLAB/ Simulink software.

High-power 1.6 μm noise-like square pulse generation in an all-fiber mode-locked laser

We demonstrate generation of high-power and large-energy noise-like square pulses at 1612 nm in an all-fiber dumbbell-shaped mode-locked Er: Yb co-doped double-clad fiber (EYDF) laser. The custom couplers with high power handling keep the laser function well. Large-mode-area EYDF with high power handling and enough high pump power make it possible to obtain high output power in the oscillator. Compared with figure-eight structure, strictly all-fiber dumbbell-shaped structure without isolator and optimizing splicing loss could reduce intra-cavity loss and improve optical to optical efficiency, which could reduce heat accumulation and enhance the power carrying capacity of EYDF. In order to study the influence of in-band absorption on output wavelength, EYDF1 and EYDF2 with different in-band absorption coefficients are accessed to intracavity, respectively. It is directly demonstrated that regulation of in-band absorption is an effective way to control the output wavelength. Strong in-band absorption could restrain the emission of C-band and make the wavelength range above 1.6 μm obtain enough gain. Linear insertion loss is another important factor to affect the emission wavelength in EYDF fiber laser. At pump power of 8 W, maximum average output power with emission wavelength above 1.6 μm can reach 1.16 W, corresponding to a single pulse energy of 1.26 μJ. SNR of output pulse is 70 dB which indicates the high stability of mode-locking. In order to verify and evaluate influence of insertion loss on the output characteristics of mode-locked laser, a variable attenuator is inserted in experimental setup, allowing us adjust the linear loss of the cavity. By increasing pump power and adjusting PCs, mode-locked pulses could be obtained on the condition of large additional insertion loss. Even though ~ 10 dB additional insertion loss is introduced, the oscillation still could function at 1612 nm and keep stable mode-locked state. This result demonstrates our oscillation could bear strong additional loss and own strong robustness. If excessively large additional insertion loss is added, 1566 nm becomes the central emission wavelength and wavelength component at 1612 nm almost disappears. Our investigation supplies a direct guideline to design high-power fiber laser with emission wavelength above 1.6 μm.

Calculation of Permissible Power of Synchronous Generators Functioning with Transformer Load

The influence of the currents of higher harmonic components on the operation of the electrical equipment of a power system with a high fraction of electrical receivers with nonlinear volt-ampere characteristic is considered. It is shown the presence of transient currents of higher harmonic components in the stator coil of a synchronous generator leads to a substantial increase in the losses of power both in the stator coil and in the rotor coil. Results of an estimate of the influence of the currents of higher harmonics on the operating regime of the generator are presented. It is suggested that when a synchronous generator functions in a power system containing electrical receivers with nonlinear volt-ampere characteristic its power-carrying capacity should be reduced to prevent unacceptable heating of the generator. The thermal processes in a synchronous generator functioning with nonlinear loads are considered. The permissible power-carrying capacity of a synchronous generator with different fractions of electrical receivers with nonlinear volt-ampere characteristic is calculated.

Analysis of Water Availability for Domestic Needs in Denpasar City

This research aims to know the power carrying capacity of water for domestic needs in Denpasar City, Indonesia. Primary data collection techniques and field research using interviews to the people who directly need water for domestic purposes. Determination of the respondents was conducted by the method of purposive random sampling. The number of respondents that were used in this study was 100 respondents. The percentage of the number of communities that the fulfilment of the needs of the water comes from the PDAM as much as 38%, the well bore as much as 44% and 18% of the community’s daily water needs fulfilment comes from the well dig. Most of the drinking water needs of the community in the Denpasar city, use bottled water. Water potential of Denpasar city run off coefficient calculation is 52.35 million m3/year. Water needs for domestic purposes of Denpasar city of 65,469,173 m3/year. A comparison between the availability of water by domestic needs is. 0.9, which means the Denpasar city was included in the area that has water deficit.

A Review of LCC-HVDC and VSC-HVDC Technologies and Applications

High Voltage Direct Current (HVDC) systems has been an alternative method of transmitting electric power from one location to another with some inherent advantages over AC transmission systems. The efficiency and rated power carrying capacity of direct current transmission lines highly depends on the converter used in transforming the current from one form to another (AC to DC and vice versa). A well configured converter reduces harmonics, increases power transfer capabilities, and reliability in that it offers high tolerance to fault along the line. Different HVDC converter topologies have been proposed, built and utilised all over the world. The two dominant types are the line commutated converter LCC and the voltage source converter VSC. This review paper evaluates these two types of converters, their operational characteristics, power rating capability, control capability and losses. The balance of the paper addresses their applications, advantages, limitations and latest developments with these technologies.

Stress test measurements of lattice‐matched InAlN/AlN/GaN HFET structures

AbstractInAlN/GaN heterostructures offer some benefits over existing AlGaN/GaN heterostructures for HFET device applications. In addition to having a larger bandgap than typical AlGaN compounds used in HFET devices (with Al < 30%), which leads to better confinement and subsequent larger power carrying capacity, InAlN can be grown lattice‐matched to GaN, resulting in strain‐free heterostructures. As such, lattice‐matched InAlN provides a unique system wherein the reliability of the devices may exceed that of the strained AlGaN/GaN devices as a result of being able to decouple the hot electron/hot phonon effects on the reliability from the strain related issues. In this work, we subjected lattice‐matched InAlN‐based HFETs to electrical stress and observed the corresponding degradation in maximum drain current. We found that the degradation rates are lower only for a narrow range of moderate gate biases, corresponding to low field average 2‐dimensional electron gas (2DEG) densities of 9–10 × 1012 cm−2. We propose that the degradation is attributable to the buildup of hot phonons since the degradation rates as a function of electron density generally follow the hot phonon lifetime versus electron density. This provides evidence that hot phonons have a significant role in device degradation and there exists an optimal 2DEG density to minimize hot phonon related degradation. We did not observe any correlation between the degradation rate and the gate leakage.

A RIGOROUS ANALYSIS AND EXPERIMENTAL RESEARCHES OF WAVEGUIDE MAGIC TEE AT W BAND

Abstract—A waveguide magic tee at W band is analyzed exactly and developed. The analysis approach is a combination of the mode expansion method and finite element method, which is based on the weak form of Helmholtz equation. Mode expansion instead of PML (Perfectly Matched Layers) is used to truncate the computing space of finite element. A magic tee at W band (75∼110 GHz) with the structure, which is easy for manufacture, is developed. Calculated results are presented and compared to those in experiments. Agreement has been observed. A sensitivity analysis is carried out, which shows the influence of the tolerance of manufacture on the performance of the magic tee. And the power carrying capacity of the designed magic tee is also evaluated.

FLEXIBLE AC TRANSMISSION SYSTEMS (FACTS)

ABSTRACT The paper reviews literature which addresses the application of Flexible AC Transmission System (FACTS) concepts to the improvement of Power System utilisation and performance. It summarises literature on using high speed thyristor based control of HVAC power system elements to enhance the power carrying capacity of existing transmission circuits without compromising reliability. It describes a study system representative of existing power systems that has been developed to evaluate the economic and technical issues of loading transmission lines to their thermal limits. Considered are two scenarios, a multi-line corridor and a long radial interconnection, where the issues addressed are transient and dynamic stability, power flow control, reactive support and voltage stability. A benchmark system is developed to validate performance of die more simple devices. It is concluded that FACTS devices have the potential to significantly increase system stability margins thereby increasing loading capability of existing transmission corridors such as between Scotland and England. Economic evaluations of the applications reviewed in the literature show that FACTS devices are attractive when compared with the other methods of achieving similar performance objectives.

Use of a saturating choke in the series capacitor compensation of distribution lines

Series capacitors can increase the power carrying capacity of subtransmission and distribution lines by reducing voltage regulation. When considering series capacitor compensation of distribution lines and subtransmission lines careful consideration needs to be given to capacitor location, ferroresonance, ohmic reactive value, transient behaviour, short circuit withstand and capacitor protection. Conventional design approaches include shunt connected resistors, spark gaps, metal oxide varistors, thyristor controlled reactors and bypass switches. The use of a saturating choke and damping resistor to control ferroresonance, transients, and through-fault currents is described. A small-scale laboratory nonlinear single-phase ferroresonant circuit was constructed with realistic per unit component values. Both 3rd and 2nd subharmonic ferroresonance modes were predicted by modelling and generated in practice. Choke and damping resistor parameters were selected by modelling to eliminate all the unwanted ferroresonant states. Experimental work confirmed that all the unwanted ferroresonant states were eliminated from the laboratory circuit. The transient and short circuit performance of the system is considered. The proposed arrangement offers an effective countermeasure to ferroresonance for series compensated distribution lines. The system also allows some control of system fault levels and transient circuit behaviour. The technique is simple, effective and requires no sophisticated control, protection or bypass switch systems.

Modelling and mapping ferroresonant states in series compensated distribution and subtransmission lines

Series capacitors can increase the power carrying capacity of subtransmission and distribution lines by reducing voltage regulation. The potential exists in selected locations for utilities to both improve the customer quality of supply and increase the supply capacity. The possibility of ferroresonance and effective countermeasures to ferroresonance are important issues that need to be carefully considered at the design stage. Other design issues are capacitor location, ohmic reactive value, transient behaviour, short circuit withstand and capacitor protection. Ferroresonance can cause severe overvoltages and heavy currents resulting in damage to power system equipment and customer installations. This paper describes a ferroresonance model incorporating both time domain and frequency domain techniques. The ferroresonance model is used to map the possible ferroresonant states. A small scale laboratory nonlinear ferroresonant circuit was constructed with the experimental results comparing favourably with the predicted model behaviour. For series compensated lines and other circuit arrangements, the ferroresonance model allows the prediction of ferroresonant states and the examination of countermeasures.

Economical design of series capacitor compensation for long power transmission systems

Series capacitor compensation has been found to considerably increase the power carrying capacity of AC long power transmission systems. This paper presents a mathematical model and an analytical procedure for finding the economical degree of series capacitor compensation. Two analytical approaches are described: the first is based on minimizing the energy transmission cost of 1 kWh to be transmitted over the compensated line, and the second is based on maximizing an objective function defined by the difference between the equivalent cost of the increase in the operating level of the power transmitted over the line and other costs associated with the line including the costs of series capacitors and extra power losses due to the higher current carried over the compensated line. Results of the application of the proposed procedure to a sample 500 kV transmission line are provided. The effects of different electrical parameters on the optimal (economical) compensation conditions are also considered.

Polygonal Coaxial Line with Round Center Conductor (Short Paper)

The complex potential function W = A (In z + C /sub n/z/sup n/) generates a zero-potential line approximating a regular polygon of N sides very closely, except in the nearly field-free region. By means of this function we work out the characteristic impedance, the power-carrying capacity, and the attenuation constant of the polygonal line of N sides wtth a round inner coaxial conductor in a closed form of elementary functions with good accuracy compared to more complex solutions. Results for N = 3 are believed to he nearly as good as those available in the literature.

Multimode propagation in anisotropic optical waveguides

Using far from cutoff approximation (2a/λ0 ≫ 1) we have derived elegant expressions for the characteristic equations and their relevant solutions to determine the guided wave features of an optical waveguide having an axial dielectric anisotropy. Also, the attenuation constant has been calculated following the concept of a complex permittivity in a lossy medium. For TE and TM, as well as hybrid modes studied here, the results computed by the approximate method show very good agreement with those of the exact analytical solutions. The dependence of the power carrying capacity and attenuation on the waveguide parameters highlights the usefulness of the dielectric anisotropy in optical waveguides.

Guided Waves In Anisotropic Slabs

Wave propagation through uniaxial and biaxial asymmetric anisotropic dielectric slab waveguides at microwave, millimetric and optical frequencies have been studied in the present paper. Results of the theoretical investigations on propagation constant, cut-off parameter, powerflow, power carrying capacity and attenuation due to lossy dielectric have been presented for different guided modes. Symmetric and asymmetric isotropic structures, treated as special cases of the formulation, have also been presented. The work is then extended to the sensitivity analysis of optical waveguides. The study is useful in design and fabrication of different components in integrated optics.

A Discussion on recent advances in heavy electrical plant - Superconducting cables for a.c. and d.c. power transmission

The growth of electricity demand has led to a steady increase in the power-carrying capacity of underground power transmission lines. Some present cables are water cooled to increase their current rating, and further increases could be achieved by refrigerating the conductors to reduce their resistivity. The ultimate and best use of refrigeration is to cool to a few Kelvins above absolute zero so that superconductors can be used. The technical problems of both a.c. and d.c. superconducting cables are described, with particular attention to the choice of superconductor and the choice of dielectric. The conductor choice is heavily influenced by fault current requirements. Some possible cable designs are then discussed, and present progress towards such designs briefly summarized. The electrical parameters of superconducting cables are deduced, and tentative economic assessments put forward. For high-power levels, exceeding 2 GVA, superconducting cables may offer real advantages; on the other hand, it may be 20 years before substantial requirements for such cable will arise.