Potential Rise Research Articles

Harmonic grounding impedance of rods in horizontally stratified soils using ABCD-matrix approach

Grounding electrodes play a fundamental role in the operation of power systems. In this context, precise computation of grounding impedance must consider the frequency-dependence of the soil parameters and the ground organized in stratified layers of soil. This paper proposes an ABCD matrix approach to compute the harmonic grounding impedance of rods buried in frequency-dependent stratified soils directly in the frequency domain. This technique is based on the traditional ABCD matrix used for overhead multi-phase transmission lines extended to grounding systems. In this approach, each rod segment is modeled as a short transmission line where the equivalent harmonic grounding impedance is calculated. Then, the Ground Potential Rise (GPR) waveforms are computed by lightning currents injected into the rods buried in different scenarios. Results indicated that the ABCD matrix approach has shown a good agreement with those obtained using a full-wave electromagnetic software FEKO. The frequency-dependence of the soil electrical parameters causes a significant modification in the harmonic impedance of grounding rods which reduces the GPR peaks considerably, being this reduction more pronounced in homogeneous and 2-layer soils. The proposed technique is an attractive tool since that considers the frequency dependence on each layer of soil, with a low computational cost and good accuracy from 100 Hz up to 1 MHz.

Experimental analysis of horizontal grounding wires buried in high-resistivity soils subjected to impulse currents

• Experimental response of grounding wires in high-resistivity soils is presented. • Grounding impulse impedance is lower than resistance for higher resistivities. • Experiments show relevant influence of frequency dependence of soil parameters. • Influence of increasing the front-time on impedance depends on electrode length. This paper presents experimental results of the ground potential rise (GPR) developed by grounding wires buried in high-resistivity soils and subjected to impulse currents. A large experimental dataset is presented, comprising grounding wire lengths ranging from 10 m to 50 m, buried in soils of resistivities between around 1100 Ωm to 1600 Ωm, and subjected to impulse currents with front-time ranging from around 1.2 μs to 7 μs. The experimental results further confirmed some important aspects regarding the lightning response of grounding electrodes buried in high-resistivity soils, namely the influence of the frequency dependence of soil parameters and the value of impulse impedance lower than the grounding resistance for electrodes shorter than effective length. Comparison between experimental and simulated results reinforces the need to consider the frequency-dependence of soil parameters for obtaining accurate results of the lightning response of grounding systems buried in poor conducting soils.

Alternative study to reduce backflashovers using tower-footing grounding systems with multiple inclined rods

This paper investigates the influence of the inclination angle on the harmonic grounding impedance (HGI) of three arrangements with multiple rods. Then, Ground Potential Rise (GPR) and the lightning performance (backflashover prediction) on transmission towers using these grounding systems are studied. A full-wave electromagnetic software FEKO using Method of Moments (MoM) is utilized to compute the HGI in a frequency range of 100 Hz to 10 MHz, assuming the soil with low-frequency resistivity of 1,000 Ω m and modeled considering the frequency effect on the ground parameters. The analysis is carried out for grounding systems of multiple rods composed of 2, 3, and 4 inclined electrodes considering inclination angles of 0°, 15°, 30°, 45° and 60°. The transient GPR developed for the first and subsequent return strokes are evaluated. The calculated HGI showed expressive differences for each topology and also for various inclination angles. Consequently, transient GPR waveforms present expressive mitigation for each grounding system whose difference can be obtained only by varying the inclination angle of the rods. Finally, the backflashover probability is reduced when these arrangements with multiple rods combined with highly inclined electrodes are used as tower-footing grounding systems, improving the lightning performance of power systems. • Harmonic impedance of inclined rods is computed for frequency-dependent soil. • GPR is significantly influenced for arrangements with multiple electrodes and angle. • Backflashover is reduced when multiple rods are used as a grounding system. • These arrangements are an alternative for lines located in limited urban areas.

Effect of lightning mast placement on underground power cable jacket stress within high voltage substations

This study aims to investigate the impact of lightning masts placement on underground cables within high voltage substations. While the subject of lightning discharges near to underground cables has been covered with open cable runs and wind farms in many papers, this study focuses on lightning events within high voltage substations considering the associated effective zones, which were not covered in the available literature. Substations built within areas prone to high lightning activity experience frequent discharges that cause the potential rise of the earthing system into hundreds of kilovolts. The potentials propagating within the soil and the earthing grid affect underground cables jackets terminated within the substation. The numerical analysis of the problem is carried out using Current Distribution, Electromagnetic fields, Grounding and Soil structure analysis (CDEGS) software engine for different configurations of lightning mast placements with varied separation, electrode placement and length, soil resistivity, and lightning current. Study findings indicate that provision of lightning masts/down conductors as far as possible or at least twice the effective zone radius from cable termination/route electrodes ensures relatively lower stress voltages. Electrodes with effective zone radius length placed as close as possible to lightning masts further reduce the attainable jacket stress voltages.

Evaluation on User Experience (UX) and User Emotions in Open Distance Learning (ODL) at Institute of Higher Learning

Many countries have given national directives to help stop the coronavirus outbreak, encouraging people to stay at home. Other policies for fighting the coronavirus pandemic have been revealed to prevent a potential rise in the affected population. Based on [1], one of these rules would not allow more than 100 people in a room such meeting or conference. Therefore, several governments have declared the closing of IHLs since February 2020. Online Distance Learning (ODL) is the only option to sustain the continuous teaching and learning process during Pandemic. [2] stated that the world has to be forced to change from conventional to ICT based e-learning platforms. Compared to school, Institute of Higher Learning (IHL), faces a higher challenge due to international students' involvement where the Universities have to cater the education process worldwide. Many IHL in the world evolved the landscape of studies from traditional or blended learning to ODL [3]. According to [4], many closures were impacted, affecting 67 per cent of the world's IHLs students. However, throughout this case, due to the readiness and ease of using technology in education, all sorts of Web 2.0-based ICT resources are immediately used in China's education to reduce the impact of the outbreak [5]. Students who prefer learning face-to-face with an instructor in a classroom are more likely to face challenges in learning remotely. Moreover, many distance learners are now faced with a new learning environment. Keywords: User experience factors, Open Distance Learning, Emotions.

An optimal design for grounding grid configuration with unequal conductor spacing

The earthing system is considered as a very important aspect of electrical power system in terms of reliability, dependency and safety. Carrying the fault current and ensuring the safety of the operator and the equipment are the two fundamental requirements of an electrical earthing system. Moreover, by modifying the grid configuration or by reducing the earth fault current, the performance can be improved. Normally the reduction of fault current may cause changes in grid shape and size by changing the conductor spacing, grid dimensions, conductor length, grid depth and adding vertical grounding rods. A square and rectangular grid, buried in two-layer soil model is considered with unequal spaced grounding grid. This paper aims to ascertain the ideal grounding grid configuration about safety factors such as Ground Potential Rise (GPR), earthing grid resistance, touch as well as step voltages. Moreover, a square and rectangular grid, buried in a two-layer soil model are considered with Unequal Conductor Spacing. For developing an effective and economic square and rectangular earthing system for the unequally spaced design, a mathematical cost function (CF) is presented along with the modern computational intelligent technique. Hence, a Modified Harris Hawks Optimizer (MHHO) technique was proposed which is the conceptual improvement of the standard Harris Hawks Optimizer (HHO). Accordingly, the cost obtained by the proposed MHHO technique is 8.19%, 9.6%, 3.44%, 11.1% and 2.43% which is lower than other existing methods like PSO, GA, FF, HHO, MOPSO at 60th iteration, for population size 10.

Expendable and Distributed Measurement Scheme for Acquisition of Naturally Sparse Events

A common reason for electronic measurement anomaly is the inadvertent rise in ground potential with respect to measurement ground. The ground potential rise happens during current leakage to ground from lightning or from power grid and leads to catastrophic failure unless appropriate preventive action is taken to isolate the sensitive measurement systems. A networked system for acquisition and transmission of ground potential measurements to data monitoring station is presented here. The system is aimed to implement using low-cost IoT devices with limited resources since these units are planned to be expendable. The limited processing power of such devices is not sufficient to run high efficient computation intensive routing algorithms. A lightweight routing algorithm for this purpose is proposed here. The discussion on reliability of such systems is also presented. The multipath route discovery strategy presented here reconfigures the network to an optimal configuration with respect to energy dissipation and node distribution.

The Impact of Apparent Frequency-Dependent Soil Properties on Electrical Grounding Characteristics

The purpose of this work is to estimate and reduce errors that can occur if apparent frequency-dependent soil properties are used for calculations of the grounding potential rise and exact inhomogeneous soil structure is neglected. Such estimation would help evaluate, which level of complexity is needed for measurement techniques when soil properties are used for grounding design. Simulations have shown that errors associated with the usage of apparent soil properties for electrical grounding characteristics can be avoided if the depth of investigation is chosen appropriately (except for specific cases). A measurement approach was proposed that takes into account which instruments are available for measurements. The approach was verified by measurements with inhomogeneous soils. In addition, it was found that to avoid the high-frequency effects in measurements of soil properties, it is convenient to limit the depth of investigation (rather than dipole size). It has also been demonstrated that soil inhomogeneities can lead to differences in apparent soil properties at higher frequencies (for the same low-frequency resistivity).

Evaluation of the lightning performance of grounding electrodes using FDTD-based computational model: Influence of absorbing boundary conditions and representation of the frequency-dependence of soil parameters

• Lightning response of grounding electrodes is assessed using FDTD. • The effect of absorbing boundary conditions is shown. • Liao's 3rd order and CPML lead to results better than those of Liao's 2nd order. • Modeling the soil as a Debye medium leads to results closer to those of HEM model. • 6 poles are enough to represent the frequency-dependence of soil parameters. This work evaluates the influence of the absorbing boundary conditions (ABC) and the representation of frequency-dependent soil parameters on the assessment of the lightning performance of grounding electrodes using FDTD-based computational model. The results in terms of grounding potential rise (GPR), grounding impulse impedance (Z P ), and low-frequency grounding resistance (R LF ) showed a better agreement with those calculated by the HEM model when Liao's 3rd order and Convolutional perfect matched layer (CPML) boundary conditions were assumed. The increase of the simulation space contributed to improve the results related to Liao's 2nd order but demanding a longer computation time. Despite the observed improvement, they are still far from those provided by the other ABC. Modeling the soil as a Debye medium to consider frequency-dependent soil parameters leaded to lightning response of grounding electrodes very close to that provided by the HEM model. In terms of Z P , the largest percentage difference was about 6%. Also, the work indicated that the adoption of 6 poles identified by the MATLAB function invfreqs was enough to represent the frequency-dependence of soil parameters, contributing to decrease the computation time.

Durable High‐Temperature Proton Exchange Membrane Fuel Cells Enabled by the Working‐Temperature‐Matching Palladium‐Hydrogen Buffer Layer

AbstractThe durability degradation during stack‐operating conditions seriously deteriorates the lifetime and performance of the fuel cell. To alleviate the rapid potential rise and performance degradation, an anode design is proposed to match the working temperature of high‐temperature proton exchange membrane fuel cells (HT‐PEMFCs) with the release temperature of hydrogen from palladium. The result is significantly enhanced hydrogen oxidation reaction (HOR) activity of Pd and superior performance of the Pd anode. Furthermore, Pd as hydrogen buffer and oxygen absorbent layer in the anode can provide additional in situ hydrogen and absorb infiltrated oxygen during local fuel starvation to maintain HOR and suppress reverse‐current degradation. Compared with the traditional Pt/C anode, the Pd/C also greatly improved HT‐PEMFCs durability during start‐up/shut‐down and current mutation. The storage/release of hydrogen provides innovative guidance for improving the durability of PEMFCs.

A Marching-on-in-Time Method of Moments for Transient Modeling of a Vertical Electrode Buried in a Lossy Medium

This article proposes a full-wave time-domain method for analyzing the transient behavior of a grounding electrode buried vertically in a lossy soil. In this method, the electrode is first approximated by a thin wire, and the modified image theory is utilized to account for the soil–air interface. The governing electric field integral equation (EFIE) is then derived with the current distribution along the electrode being the unknown quantities. Finally, the EFIE is solved by the time-domain method of moments based on a marching-on-in-time (MOT) procedure. This is done by expanding the unknown currents in terms of a finite linear combination of products of appropriate spatial and temporal basis functions, and adopting the Galerkin method in space and the point matching method in time. The MOT procedure makes the proposed method more efficient computationally than its rival frequency-domain method of moments (FD-MoM). The efficiency of the proposed method is demonstrated by comparing the lightning ground potential rise of various grounding electrodes with those obtained using the FD-MoM and a commercial numerical code.

Durable High-Temperature Proton Exchange Membrane Fuel Cells Enabled by the Working-Temperature-Matching Palladium-Hydrogen Buffer Layer.

The durability degradation during stack-operating conditions seriously deteriorates the lifetime and performance of the fuel cell. To alleviate the rapid potential rise and performance degradation, an anode design is proposed to match the working temperature of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) with the release temperature of hydrogen from palladium. The result is significantly enhanced hydrogen oxidation reaction (HOR) activity of Pd and superior performance of the Pd anode. Furthermore, Pd as hydrogen buffer and oxygen absorbent layer in the anode can provide additional in situ hydrogen and absorb infiltrated oxygen during local fuel starvation to maintain HOR and suppress reverse-current degradation. Compared with the traditional Pt/C anode, the Pd/C also greatly improved HT-PEMFCs durability during start-up/shut-down and current mutation. The storage/release of hydrogen provides innovative guidance for improving the durability of PEMFCs.

Electromagnetic-thermal two-way coupling analysis and application on helium-cooled solid blanket

The blanket plays an important role in fusion reactor and stands extremely high thermal and electromagnetic loads during operation situation and plasma disruption event, brings the need for precise thermal and electromagnetic analysis. Since the thermal field and EM field interact with each other nonlinearly, we develop a method of electromagnetic-thermal two-way coupling by using finite element software COMSOL. The coupling analyses of blanket under steady state and MD event are implemented and the results are analyzed. For steady state, the influences of coupling effects are relatively small but still recommended to be considered for a high precision analysis. The influence of thermal field on EM field can't be ignored under MD events. The variation of force density could cause a significant change in stress in certain parts of blanket. The influence of Joule heat during MD event is negligible, yet the potential temperature rise caused by induced current after MD event still needs to be researched.

Health beyond medicine. A planetary theory extension.

In Niklas Luhmann's vision of the modern functionally differentiated society, health presents one of the essential function systems, along with politics, law, economy and science. While he devoted much effort to elaborating the theoretical foundations of the latter function systems, his work on the health system was relatively sparse. This research gap has been rendered particularly acute by the recent COVID-19 crisis. In reconstructing and updating the Luhmannian analysis of this system, this article presents a three-dimensional concept of organic, psychic and social health and highlights the risks raised by a potential overexpansion of the health concept to the planetary level. The most important of these risks is shown to be the potential rise of totalitarian social control that exceeds classical forms of medical social control. The proposed argument not only contributes to the public criticism of the political responses to the COVID-19 crisis but also fills in some missing pieces of Luhmann's seminal elaboration of the health system.

Study on the characteristics of the potential rise of shell under VFTO in the GIS pumped storage power station

Compared with the traditional GIS station, complex wiring and operation mode of pumped-storage plant diversity, working condition of frequent transformation, makes the plant to produce very fast transient overvoltage (VFTO) probability increase greatly. VFTO will form a transient coupled to the GIS shell casing transient earth voltage (TEV), and then to station personnel safety and the reliability of the secondary equipment poses a great threat. But at the moment because of the limitation of testing technology such as understanding of the academic study of TEV is lack of system. Based on a typical 500 kV gis pumped-storage power station, this paper established a system equivalent model of GIS, network frame and calculates the amplitude, frequency spectrum characteristic of the TEV and influence on VFTO characteristics, and analyzes the fault location, power supply mode, branch bus, the influence of vertical grounding electrodes on the TEV characteristics, For the characteristics of the TEV rules and parameters. Research on TEV characteristics of GIS of pumped storage power station has important reference value for further perfecting relevant theories.

Histomorphological evaluation of placenta in SARS-CoV-2 patients: A cross-sectional study.

SARS-CoV-2 has emerged as a major pandemic of the century and little is known about the impact of maternal infection on placental histopathology. Histopathologic examination of placental tissue can contribute to significant information regarding the pathophysiology of the disease and how it affects the fetal outcome. This was a cross-sectional study conducted at the Department of Pathology, Government Doon Medical College and Hospital, Dehradun, on the placenta of 50 coronavirus disease 2019 (COVID-19)-positive pregnant females confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) from August 2020 to October 2020. Fifty term historical placentas were taken as control. Placenta sections were fixed in formalin, processed into paraffin blocks, stained with hematoxylin and eosin (H and E) stain, and visualized for any abnormality. The most prominent histological finding in the placenta of pregnant women affected by COVID-19 was chorangiosis, which is a feature of fetal vascular malperfusion seen in 28 (56%) cases. Other features included maternal vascular malperfusions (MVM) such as villous crowding and agglutination in 12 (24%) cases. Tenney-Parker change was seen in 13 (26%) patients. Intervillous fibrinoid deposition and intervillous hemorrhage were seen in 37 (74%) patients and 7 (14%) patients showed significant calcification. Other findings observed were less common. Infection with SARS-CoV-2 may be associated with a significant impact on fetal and maternal circulation causing features of fetal and maternal malperfusion such as chorangiosis, villous crowding, and agglutination. Indicating that the infection could cause a potential rise in the risk of adverse perinatal outcomes such as intrauterine fetal growth retardation, preterm birth, or stillbirth.

Numerical assessment of potential sea level rise impacts on coastal retreat along the Nigerian Mahin mud coast

Numerical assessment of potential sea level rise impacts on coastal retreat along the Nigerian Mahin mud coast

Sodium-Glucose cotransporter 2 inhibitor empagliflozin decreases ventricular arrhythmia susceptibility by alleviating electrophysiological remodeling post-myocardial-infarction in mice.

Background: Recent clinical trials indicate that sodium–glucose cotransporter 2 (SGLT2) inhibitors improve cardiovascular outcomes in myocardial infarction (MI) patients, but the underlying mechanisms remain unknown. As arrhythmia often occurs during myocardial infarction, it is the main cause of death. Objective: The purpose of this study was to investigate the influence of empagliflozin (EMPA), an SGLT2 inhibitor, on cardiac electrophysiological remodeling and arrhythmia susceptibility of myocardial infarction mice. Methods: ECG was obtained from mice 1 week after MI to determine the QT interval. In an electrophysiological study and optical mapping was performed to evaluate the function of EMPA and underlying mechanisms of post-myocardial-infarction in mice. Results: EMPA treatment significantly reduced the QT interval of MI mice (MI + EMPA 50.24 ms vs. MI 64.68 ms). The membrane potential and intracellular Ca [Cai] were mapped from 13 MI hearts and five normal hearts using an optical mapping technique. A dynamic pacing protocol was used to determine action potential duration and [Cai] at baseline and after EMPA (10 umol/L) infusion. EMPA perfusion did not change the APD80 and CaT80 in normal ventricles while shortening them in an infarct zone, bordering zone, and remote zone of MI hearts at 200 ms, 150 ms, 120 ms, and 100 ms pacing cycle length. The conduction velocity of infarcted ventricles was 0.278 m/s and 0.533 m/s in normal ventricles at baseline (p < 0.05). After EMPA administration, the conduction velocity of infarcted ventricles increased to 0.363 m/s, whereas no significant changes were observed in normal ventricles. The action potential rise time, CaT rise time, and CaT tau time were improved after EMPA perfusion in infarcted ventricles, whereas no significant changes were observed in normal ventricles. EMPA decreases early afterdepolarizations premature ventricular beats, and ventricular fibrillation (VF) in infarcted ventricles. The number of phase singularities (baseline versus EMPA, 6.26 versus 3.25), dominant frequency (20.52 versus 10.675 Hz), and ventricular fibrillation duration (1.072 versus 0.361 s) during ventricular fibrillation in infarcted ventricles were all significantly decreased by EMPA. Conclusion: Treatment with EMPA improved post-MI electrophysiological remodeling and decreased substrate for VF of MI mice. The inhibitors of SGLT2 may be a new class of agents for the prevention of ventricle arrhythmia after chronic MI.

Assessing Public Transportation Vulnerability to Sea Level Rise:A Case Study Application

The potential for sea level rise inundation of critical transportation infrastructure rises as the threat of climate change continues. Inundation of public transportation including railroads and bus routes, specifically those located in low-lying coastal areas, are vulnerable to these impacts. Therefore, identifying vulnerable facilities in order to implement adaptation planning practices is essential to protecting these facilities and avoiding impacts on mobility. This research focuses on the application of the Transit Inundation Modeling Method (TIMM) to a transit network (railways and bus routes) in Philadelphia County, Pennsylvania. TIMM is developed based on the need to identify transit infrastructure systems that are vulnerable to sea level rise using Geographic Information Systems (GIS). Applying TIMM to a real-world transit network provides an example for how transit agencies throughout the nation can begin to identify at-risk links and nodes based on potential sea level rise inundation levels.

Zero volt storage of Na-ion batteries: Performance dependence on cell chemistry!

Sodium-ion batteries (NIBs) are regaining their importance in recent years as a sustainable complementary energy storage device for Li-ion batteries. Although, they cannot compete in terms of energy density with respect to Li-ion, they present a few advantages, namely the 0 V stability that makes them safe during external short and/or over-discharge. When the cell is discharged to 0 V, the negative electrode potential shoots up high during which the copper current collector in use for Li-ion cells could oxidize, dissolve and leads to internal short. In contrast, Na-ion cells utilize an aluminium current collector that is strongly resistant against oxidation, hence enabling their 0 V stability. However, apart from the current collector stability, the negative electrode potential rise could cause interphase instability which is not well elucidated. Hence, herein, we explored two different Na-ion chemistries, namely polyanionic Na3V2(PO4)2F3-hard carbon and sodium layered oxide-hard carbon using different electrolyte formulations. Combined impedance analyses, ex-situ X-ray photoelectron spectroscopy (XPS) and operando optical sensing indicate the 0 V discharge involves SEI degradation thereby deteriorating the cell performance, the extent of which depends on the positive electrode potential and the electrolyte in use. Overall, the 0 V stability is not an in-built property of Na-ion cells and a careful selection of cell chemistry is mandatory to achieve 0 V stable Na-ion cells.