Potential Rise Research Articles

Induced Overvoltage Caused by Indirect Lightning Strikes in Large Photovoltaic Power Plants and Effective Attenuation Techniques

Indirect Lightning Stroke (ILS) is considered an urgent issue on overall power systems due to its sudden dangerous occurrence. A grid-connected solar Photovoltaic (PV) power plant of 1MW was considered and analyzed using PSCAD/EMTDC software. The effect of grounding grid resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g}$ </tex-math></inline-formula> ) on the induced voltages caused by the indirect strokes was discussed. The Transient Grounding Potential Rise (TGPR) variation with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g}$ </tex-math></inline-formula> was presented and discussed. Four different models were proposed and installed for the system under study, which includes a combination of the Externally Gapped Line Arrester (EGLA) with the Non-Gapped Line Arrester (NGLA). The results show that when the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g}$ </tex-math></inline-formula> was reduced from 5 to 1 ohm, TGPR decreased by about 79.63%, whereas the peak value was reduced by about 91.3% nearby the striking position. Four models of EGLAs were proposed to reduce the induced transient overvoltage effectively. The four models showed a remarkable ability to reduce the backflow current (BFC) and, consequently, the induced overvoltage. The EGLA’s type with the composite air gap reduced the TGPR by about 77.04 % and reduced the induced overvoltage nearby the striking position by about 51.3%.

A Comparative Life Cycle Assessment (LCA) of Gasoline Blending with Different Oxygenates in India

This paper includes a cradle-to-gate life cycle impact evaluation of gasoline blends in India. The potential environmental impacts of gasoline blends with three major components, i.e., methanol, ethanol, and n-butanol are assessed. The production of methanol from the natural gas reforming process, ethanol from hydrogenation with nitric acid, and n-butanol from the oxo process are considered in the current study. The results show that the gasoline blending with methanol has the lowest impact (11 categories) and is nearly constant from 5 to 15%. For gasoline with ethanol as an additive, the global warming potential, ozone depletion potential, and abiotic depletion potential rise with increasing ethanol addition. Meanwhile, increasing ethanol addition reduces the acidification potential and terrestric ecotoxicity potential impact of gasoline blends. Similarly, gasoline with n-butanol as an additive has higher acidification potential, eutrophication potential, human toxicity potential, terrestric ecotoxicity potential, marine aquatic ecotoxicity potential, and photochemical ozone creation potential compared to methanol and ethanol.

Study of cryogenic CO2 capture with solar-assisted VAR system

One of the major contributors to the rise in global warming potential (GWP) is the continuous accumulation of carbon dioxide (CO2) in the atmosphere. Carbon capture and storage (CCS) is a modern approach to capture CO2 from various industrial processes and store it efficiently for further use. In the cryogenic carbon capture method, CO2 is liquefied by condensation and separated from the CO2 contained gas. The CO2 capture by the cryogenic method can yield high purity CO2 and negligible secondary emissions. However, huge energy is required for the condensation process. In the present study, a low energy penalty method for a post-combustion carbon capture process by the application of the cryogenic technique is performed using process simulation. To reduce energy consumption, a solar integrated vapor absorption refrigeration (VAR) system is designed. The designed solar VAR system provides the required refrigeration cooling load for condensing CO2 in a flue gas stream. For this purpose, the flue gas mixture composed of CO2, N2, and water vapor with respective molar fractions of 15%, 75%, and 10% is considered. The mass flow rate of the flue gas considered is 673.4 kg/s at 1.1 bar and 40 °C. CO2 is separated by condensing the gas at a pressure of 40 bar and temperature of −28 °C. The heat energy required to operate the VAR is 83.3 MW at 75 °C which is supplied by the solar collector. The simulation result indicates that for a post-combustion process, a high-grade electrical energy penalty is found to be about 1.26 MJ/kg CO2 captured, which is better than the most common approaches like absorption, adsorption, and membrane methods. It is also observed that with the increase in the CO2 concentration from 15 to 25 mol% in the flue gas, the energy penalty is reduced by about 37.5%. The performance analysis is also carried out by varying the CO2 recovery rate and purity. It is observed that the energy penalty is decreased by about 10.3% with the increase of CO2 recovery from 90% to 100%. Also, the energy penalty is increased by 4.2% with the increase of CO2 purity from 95% to 100%. The specific CO2 capture process cost is found to be about 1.008 million USD/(kg.s−1).

Secondary electron emission yield measurements of dielectrics based on a novel collector-only method

The total electron-induced Secondary Electron Yield (SEY) of alkali-free glass has been determined by a novel technique which is solely based on the use of a collector electrode and of two interchangeable dielectric samples. The current from a charge-saturated sample provides a direct measure of the primary beam current. The SEY from the (uncharged) sample under investigation can then be determined simply as the ratio between the collector currents measured at the same electron energy from both samples. We further apply a low-current, short-pulse procedure to limit sample charging, needed to mitigate distortion of the SEY by charging effects. The potential build-up during the experiment could be reconstructed based on the primary electron currents and the measured SEY. This strategy permitted us to measure a 6-point SEY curve, without the need for intermediate discharging of the sample, as the total induced surface potential rise could be kept below +2.55 V.

Abstract 11706: His Bundle Pacing and Atrioventricular Nodal Ablation in the Management of Refractory Atrial Fibrillation, a Systematic Review and Meta-Analysis

Introduction: Ventricular rate control is critical in management of atrial fibrillation (AF). When pharmacologic therapy fails in controlling the ventricular rate, atrioventricular nodal ablation (AVNA) and pacing is considered an effective therapy for symptomatic management. His bundle pacing (HBP) is considered a physiologic mode of pacing with AVNA ensuring synchronized activation of right and left ventricles preserving ventricular functioning. Hypothesis: HBP and AVNA are feasible, safe, and effective for management of refractory AF. Methods: We identified 218 studies after literature review of EMBASE, Medline, and Cochrane databases. Our analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Results: Six studies (two randomized controlled trials, four observational cohorts) were included in the final meta-analyses. A total of 275 patients underwent attempted permanent HBP and AVNA. The mean age of patients was 70.74 (SD 4.38; 95% CI 62.15-79.32). Mean implant success rate for acute HBP was 94.5% (SD 10.12; 95% CI 74.70, 100.00). Selective HBP was noted in 44.7% (95% CI 12.5-76.9), while Non-selective-HBP was noted at rate of 42.2% (95% CI 10.2-74.2). The mean follow-up duration was 21.71 months (SD 3.77; 95% CI 14.32-29.11). All-cause mortality had a pooled proportion of 0.107 (SD 0.110, 95% CI -0.109-0.323); hospitalization proportion was 0.078 (SD 0.072; 95% CI -0.063-0.219). We noted a significant improvement in left ventricular ejection fraction (LVEF) (Baseline [BL] 41.84%, Follow-up [FU] 53.63%, Standardized mean difference [SMD] 0.646, p 0.028), NYHA class (BL 2.77, FU 1.55, SMD -2.542, p &lt;0.001) and LV end diastolic volume (SMD -0.495, 95% CI -0.721, -0.269, p &lt;0.001). We found a significant rise of threshold potential (BL 1.12 V, FU 1.49 V, SMD 0.393, p &lt;0.001 and an increase between baseline and follow up QRS duration (BL 102.21 ms, FU 106.90 ms, SMD 0.646, p 0.028). Conclusion: HBP and AVNA are feasible, safe, effective and has high success rate for management of refractory AF. Further studies are needed to evaluate its role in comparison to left bundle branch area pacing and cardiac resynchronization therapy to evaluate comparative efficacy in refractory AF.

Rapid rise of decarbonization potentials of photovoltaics plus electric vehicles in residential houses over commercial districts

Rooftop photovoltaics (PVs) integrated with electric vehicles (EVs) has the potential to deeply decarbonize urban energy systems in a cost-effective way. The SolarEV City Concept suggested that the rooftop PV plus EV systems can supply up to 95% of electricity demand within cities in Japan. However, it was not clear which district in city could consume, generate, and store the PV electricity, as each district has different load patterns, building structures, and number of parked cars. In this study, we performed techno-economic analyses on rooftop PV systems integrated with stand-alone batteries or EVs in residential and commercial districts in Japan from 2020 to 2040. We found that rooftop PV systems in 2020 are already cost competitive relative to existing energy systems. However, “PV + EV” systems in residential houses rapidly increases its economic advantage over commercial districts due to greater rooftop space and higher number of available vehicles. Moreover, energy sharing significantly improved the decarbonization potential. By 2025, energy cost savings, payback periods, and internal rate of return (IRR) of residential “PV + EV” systems respectively reached 23%, 9 years, and 11%, and continued improving in subsequent years. CO2 emissions from electricity and gasoline consumption was reduced by 88%, and the system was capable to supplying 89% of electricity demand. The results indicate that residential “PV + EV” systems are a potential source for significant renewable energy generation and storage that can also produce increasingly dispatchable electricity. Policy makers, industries, and communities should prepare to establish these systems through regulatory reform and demonstration projects to scale-up after 2025.

Representative Democracy and Colonial Inspirations: The Case of John Stuart Mill

Focusing on John Stuart Mill, a particularly illuminating contributor to modern democratic theory, this article examines the connections between modern democracy and the European colonial experience. It argues that Mill drew on the exclusionary logic and discourse available through the colonial experience to present significant portions of the English working classes as domestic barbarians, whose potential rise to power posed a danger to civilization itself: a line of argument that helped him legitimate representative government as a democratic, rather than an antidemocratic form of government, as it had been traditionally perceived. The article contributes to our understanding of the development of modern democratic theory and practice by drawing attention to the ways the colonial experience shaped core Western institutions and ways of thinking, and it makes the case that this experience remains an essential, if often unacknowledged, part of our collective “self.”

Gross negligence ‘medical’ manslaughter in Ireland: Legal context and clinician concerns

In recent years, the prospect of the criminal prosecution of medical practitioners for patient safety incidents resulting in fatality which occur in the course of clinical practice has caused heightened anxiety among medical practitioners, particularly in England and Wales, where a number of high-profile cases have raised public consciousness of this issue. The full impact of this landscape on individual practitioners and the delivery of healthcare has yet to be ascertained, although research suggests that medical practice has been impacted. Of particular interest is the phenomenon of defensive medicine which occurs where physicians adopt assurance and/or avoidance behaviours in an attempt to minimise the risk of medical negligence litigation and/or to avoid complaints to regulatory bodies. While defensive medicine is traditionally conceived of in a civil context, the possibility of criminal prosecution for patient safety incidents resulting in fatality may also result in alterations to medical practice. Drawing on the findings of an empirical study (a survey), this research sought to explore the impact, if any, of the threat of criminal prosecution on surgical practice in the Republic of Ireland, including a potential rise in defensive practice.

Decentralized earth fault compensation in MV-grids - challenges and solutions

Decentralized earth fault compensation coils (EFCC) in resonantly grounded medium voltage networks are becoming increasingly popular. Their installation imposes several requirements on the earthing system in terms of equipment and personnel safety as well as the functionality of the ground-fault protection devices. Based on two practical examples of networks (urban and rural), the challenges and their possible solutions are presented and verified by on-site measurements. Due to the impressed current of the distributed EFCC, the earth potential rise (EPR), the touch voltage, the transmitted voltages to neighboring stations and to the low voltage installation (PEN conductors) have to be analyzed. The role of cable shields in relation to earthing and the influences on the distribution of the zero sequence currents discussed. In addition, this work investigates the currents flowing on the interconnecting cables between two different network areas under fault conditions with different distributions of compensation. The cable shields grounded at both ends are loaded by flowing zero sequence currents. This leads to additional heating of the cables. It is analyzed which zero-sequence currents are permanently permissible in order to avoid a maximum insulation temperature and to prevent additional aging of the cables

Afterglow dynamics of plasma potential in bipolar HiPIMS discharges

In bipolar magnetron sputtering, the plasma afterglow is initiated by switching the target bias from a negative to positive voltage. In the following, the plasma potential evolution in this configuration is characterized, being responsible for the ion acceleration at the substrate sheath potential fall, in particular in high power impulse magnetron sputtering (HiPIMS). A mass-energy analyzer and a Langmuir probe respectively measure the ion energies and the plasma/floating potential at different positions within HiPIMS discharges. A plasma potential drop and rise in the first 45 μs of the afterglow is observed, settling in the plasma bulk towards values below the applied positive bias. The measured ion energies agree with the plasma potential values before and after the drop-rise. To gain more comprehensive insights into the mechanisms responsible for such a potential evolution, particle-in-cell Monte Carlo 3D simulations of bipolar direct current magnetron sputtering discharges are explored in equivalent geometries. Despite their average power being orders of magnitude lower compared to the HiPIMS configuration, a similar afterglow behavior is observed. This indicates that the measured dynamics are not specific to HiPIMS, but rather a feature of bipolar magnetron sputtering. The responsible mechanisms are studied further: the effects of various system parameters are decoupled, with the magnetic field configuration emerging as crucial for the plasma potential drop-rise dynamics and the associated re-ionization close to the target.

Numerical analysis and safety design of grounding systems in underground compact substations

This paper presents a mathematical and numerical formulation to design and analyze grounding systems in underground electrical substations. The developed approach is based on the well known Maxwell’s Equations. The proposed problem is solved by means of the Boundary Element Method (BEM). The utilization of BEM allows to introduce the geometry and electrical characteristics of the enclosure in a uniform soil. Therefore, a more realistic approximation of the soil structure is achieved. This formulation allows to obtain the main parameters of these protection systems (the grid resistance, the Ground Potential Rise, and the step and mesh voltage). It also allows to compute the surface and step voltage distributions. In addition, as a secondary result, the voltage and current density distributions over the enclosure are obtained. Finally, two grounding system analyses of real underground electrical substations are presented to demonstrate the industrial application and the modelization capabilities of the proposed formulation.

Enhanced Hydrogen Evolution Reaction By Porous Curcumin Enveloped Gold Nanoparticles

We report a facile electrosynthesis (constant current of 0.5 mA) of gold-curcumin (Au-CM) nanocomposite using a gold wire (anode) and glassy carbon electrode (cathode, GCE) in a solution of curcumin. A thin and stable film of the nanocomposite was deposited on the GCE in 30 minutes. Extensive morphological and structural characterizations were carried out by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and BET analysis, which confirmed the formation of gold nanoparticles enveloped by a porous network of curcumin. Hydrogen evolution reaction (HER) was carried out in an aqueous solution of 0.5 M sulfuric acid with the modified GCEs. Enhanced hydrogen evolution activity was observed with Au-CM/GCE by a reduction in potential from -0.43 V (Au/GCE) to -0.32 V (Au-CM/GCE) (vs. Ag/AgCl: RE) with a 2-fold increase in current density compared to bare gold. A decrease in charge transfer resistance (9.13 kΩ to 82.6 Ω) was observed with the rise in cathodic potential from (-0.3 V to -0.48 V) at Au-CM/GCE, implying the facile nature of reaction at higher potential due to faster electron flow across the electrode-electrolyte interface. This is the first report wherein the curcumin network in the Au-CM nanocomposite aids in reducing 110 mV potential during the HER compared to bare Au. Figure 1

Quantifying the potential future contribution to global mean sea level from the Filchner–Ronne basin, Antarctica

Abstract. The future of the Antarctic Ice Sheet in response to climate warming is one of the largest sources of uncertainty in estimates of future changes in global mean sea level (ΔGMSL). Mass loss is currently concentrated in regions of warm circumpolar deep water, but it is unclear how ice shelves currently surrounded by relatively cold ocean waters will respond to climatic changes in the future. Studies suggest that warm water could flush the Filchner–Ronne (FR) ice shelf cavity during the 21st century, but the inland ice sheet response to a drastic increase in ice shelf melt rates is poorly known. Here, we use an ice flow model and uncertainty quantification approach to project the GMSL contribution of the FR basin under RCP emissions scenarios, and we assess the forward propagation and proportional contribution of uncertainties in model parameters (related to ice dynamics and atmospheric/oceanic forcing) on these projections. Our probabilistic projections, derived from an extensive sample of the parameter space using a surrogate model, reveal that the FR basin is unlikely to contribute positively to sea level rise by the 23rd century. This is primarily due to the mitigating effect of increased accumulation with warming, which is capable of suppressing ice loss associated with ocean-driven increases in sub-shelf melt. Mass gain (negative ΔGMSL) from the FR basin increases with warming, but uncertainties in these projections also become larger. In the highest emission scenario RCP8.5, ΔGMSL is likely to range from −103 to 26 mm, and this large spread can be apportioned predominantly to uncertainties in parameters driving increases in precipitation (30 %) and sub-shelf melting (44 %). There is potential, within the bounds of our input parameter space, for major collapse and retreat of ice streams feeding the FR ice shelf, and a substantial positive contribution to GMSL (up to approx. 300 mm), but we consider such a scenario to be very unlikely. Adopting uncertainty quantification techniques in future studies will help to provide robust estimates of potential sea level rise and further identify target areas for constraining projections.

Calculation of Earth Surface Potential and Neutral Current Caused by HVDC Considering Three-Dimensional Complex Soil Structure

In ground return mode of high-voltage direct current (HVDC) transmission, direct current is injected into the soil through a ground electrode, causing ground potential rise in different areas and direct current at the neutral point of transformers. Earth surface potential (ESP) and neutral current are closely related to the 3-D structure of soil, but few studies treat the soil three dimensionally when calculating these two parameters. In this article, a 3-D resistor network (RN) is developed to construct the soil model, and a soil–grid unified circuit model is proposed to simplify the calculation of neutral current. The RN method is verified by calculating ESP of a horizontal multilayer soil model and contrasting the result with that of CDEGS software. The feasibility and accuracy of the soil–grid unified circuit model is demonstrated through comparing neutral currents of two substations with the results calculated by finite-element method (FEM). The influence of resistivity changes in a water-bearing fault on ESP and neutral current is specifically analyzed using RN method and FEM to prove the necessity of considering the 3-D complex soil structure. The results of this article contribute to the simulation of DC distribution of wide-area HVDC transmission in complex soil structures.

Cellular Substrates of Functional Network Integration and Memory in Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) patients are at risk of memory deficits, which have been linked to functional network disturbances, particularly of integration of the default mode network (DMN). However, the cellular substrates of functional network integration are unknown. We leverage a unique cross-scale dataset of drug-resistant TLE patients (n = 31), who underwent pseudo resting-state functional magnetic resonance imaging (fMRI), resting-state magnetoencephalography (MEG) and/or neuropsychological testing before neurosurgery. fMRI and MEG underwent atlas-based connectivity analyses. Functional network centrality of the lateral middle temporal gyrus, part of the DMN, was used as a measure of local network integration. Subsequently, non-pathological cortical tissue from this region was used for single cell morphological and electrophysiological patch-clamp analysis, assessing integration in terms of total dendritic length and action potential rise speed. As could be hypothesized, greater network centrality related to better memory performance. Moreover, greater network centrality correlated with more integrative properties at the cellular level across patients. We conclude that individual differences in cognitively relevant functional network integration of a DMN region are mirrored by differences in cellular integrative properties of this region in TLE patients. These findings connect previously separate scales of investigation, increasing translational insight into focal pathology and large-scale network disturbances in TLE.

Narrative review on clinical considerations for patients with diabetes and COVID-19: More questions than answers.

Background‐AimDiabetes, obesity and hypertension are common comorbidities associated with increased severity and mortality rates from Corona Virus Disease (COVID)‐19.MethodsIn this narrative review (using the PubMed database), we discuss epidemiological data and pathophysiological links between diabetes and COVID‐19. The potential effects of glycaemic control and antidiabetic drugs on the prevalence and outcomes of COVID‐19 are also reviewed, as well as the role of telemedicine and diabetes self‐management in the post‐COVID‐19 era.ResultsDiabetes has been linked to COVID‐19 morbidity and mortality, although further research is needed to elucidate this association. In the meantime, physicians should be aware of the potential rise in the prevalence of diabetes (due to unhealthy lifestyle changes during the pandemic), its severity and complications and focus on achieving optimal diabetes prevention and management. Telemedicine and diabetes self‐management may help towards this direction. Dipeptidyl‐peptidase 4 (DPP4) inhibitors, glucagon‐like peptide‐1 (GLP‐1) receptor agonists and sodium‐glucose transporter 2 (SGLT2) inhibitors may affect viral entry and infection, and thus COVID‐19 outcomes, as shown in observational studies.ConclusionDiabetes has been associated with COVID‐19 development and progression. Certain antidiabetic drugs may influence COVID‐19 prevention and management. The results of ongoing randomized clinical trials will shed more light on this field.

Cellular and molecular immune response and production performance of Indian white shrimp Penaeus indicus (H. Milne-Edwards, 1837), reared in a biofloc-based system with different protein levels of feed

The present study focuses on the immunity and growth of Penaeus indicus fed with varying protein levels (25%, 30%, and 35%) in a biofloc based rearing system. A 120 days growth trial was carried out using juvenile Penaeus indicus (0.71 ± 0.01) with dietary protein level, 25% (LP), 30% (MP), and 35% (HP), and a control diet-fed with 35% acted as control group resulting in 4 treatments each with four replicates and were randomly assigned 16 tank units (7500 L each). A combination of different carbon sources (molasses, wheat flour, and rice bran in 2:1:1 ratio), yeast and a probiotic (Bacillus sp.) consortium were used for the development of biofloc. At the end of the trial, the growth parameters of shrimps viz., initial weight, feed conversion ratio (FCR), and daily growth coefficient (DGC) were computed. The results indicated that shrimp fed with medium (30%) protein (MP) diet recorded significantly (P < 0.05) improved growth performance compared to high protein fed group (35%) and low protein (25%) fed group (LP) in a biofloc system and control group (35%). The immunological parameters such as hemagglutination activity (HA) assay, serum protein, lysozyme, phenol oxidase (PO), and inhibition of superoxide dismutase (SOD) activity were observed in serum, plasma, and hemocyte lysate supernatant (HLS). The HA activity, PO activity in plasma was found to be higher in high protein fed animals, whereas medium protein resulted in enhanced PO activity in serum. Similarly, lysozyme and SOD were inhibited well in high protein fed animals compared to the low protein fed group. The vital immune genes's mRNA profiling showed a potential rise in the expressional pattern in MP and HP treatments compared to LP and control. BGBP (beta-1,3-glucan binding protein) and hemocyanin mRNA transcript levels were highly upregulated in the HP (5 fold) and moderately expressed in MP (2 fold) and LP (1–2 fold). The transcripts of peroxinectin, antimicrobial peptides like crustin showed significant upregulation in HP followed by in MP and LP and control. Likewise, other immune genes, such as SOD, prophenoloxidase (proPO), showed a similar trend in a marginal way, indicating immunomodulation in the biofloc groups. This study suggested that biofloc with high protein (35%) supplementation can substantially enhance the immune response of shrimps, although medium protein level (30%) is optimum for improving the survival, growth, and in turn economic return in Indian white shrimp.

Reprint of: Modelling long-term shoreline evolution in highly anthropized coastal areas. Part 2: Assessing the response to climate change

Here, a methodology to obtain ensemble shoreline change projections at regional scale by combining multi-model projections of wave climate and water levels and the reduced-complexity shoreline evolution model in Alvarez-Cuesta et al. (2021) is presented. In order to account for climate change uncertainty, dynamically downscaled and bias corrected projected waves and storm surge series from five different combinations of global and regional climate models and three potential mean sea-level rise (SLR) trajectories for two representative concentration pathways, are used to force the erosion impact model IH-LANS . The methodology is applied to a 40 km highly anthropized coastal stretch in the Mediterranean coast of Spain. Thirty hourly time series of shoreline evolution between 2020 and 2100 are obtained, each of them linked to one future realization of waves and water levels. From the shoreline time-series analysis, long and short -term processes are unraveled, yielding permanent retreats and beach area losses, contribution of individual physical processes (longshore, short-term cross-shore, and SLR) to shoreline change and non-stationary extreme retreats. The methodology presented herein is intended to be a useful tool for evaluating potential climate change risks while enabling the evaluation and prioritization of adaptation measures.

Observing tidal and storm generated wave height impact on groundwater levels in a tropical delta (the Sundarbans)

Groundwater level (GWL) of coastal aquifers are strongly influenced by the ocean tide at sub-daily to seasonal scale. Similarly, GWL are influenced by storm induced ocean wave surge lasting few hours to a day. There has not been a detailed study on the conjunctive impact of such tidal and storm waves on coastal groundwater and its vulnerability. Through our coastal and field-laboratory observations at one of the world’s most extreme climate affected regions, the Ganges river mega-delta, we delineate the influence of ocean wave surge impacts on the shallow (<24 m below ground level [m bgl]) and deep (115 m bgl) aquifers GWL. Our study on the multi-layered delta-front aquifers, adjoining the tropical BoB shows that the high-temporal resolution GWL fluctuation due to wave surges are instantaneous, rapid and synchronous at all depths of the aquifers. The potential rise of ocean waves caused by tropical cyclone Bulbul (November 2019) significantly increases the GWL, both in shallow and deeper aquifer. Using multivariate statistics and machine learning techniques, we have attempted to quantify the rise of GWL during each of the ocean wave surge event. The model shows good predictability for deeper groundwater, however it is unable to quantify the shallower GWL of each of the ocean wave surge during storm events. Such phenomenon indicates aquifer vulnerability, thereby posing an emerging threat to drinking water availability to millions of groundwater-dependent inhabitants in coastal areas, globally, which may rapidly intensify with increasing rates of tropical cyclones and sea level rise in recent times and impending future.

Lightning Current Performance of Conventional and Enhanced Rod Ground Electrodes

The correct operation of surge arresters under lightning and switching transient conditions requires that grounding be effective at high frequencies as well as at power system frequency. Effective high frequency grounding also limits the electrocution risk to substation personnel due to transient ground potential rise. This article assesses the performance of high frequency electrodes at typical lightning impulse current magnitudes. The enhancement of such electrodes by addition of bonded horizontal arms in cross and star arrangement is also investigated. The effective impulse resistances for electrodes having lengths up to 4.8 m are calculated over a range of impulse current magnitudes at the same location. The results obtained indicate that, for low impulse current magnitudes, the preionization electrode's resistance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) falls with increasing rod length, a behavior reflected in the measured dc resistance. The presence of horizontal enhancement was found to reduce <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> in all cases. The occurrence of soil ionization in the immediate vicinity of the electrode resulted in a reduced postionization resistance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) at higher currents, tending toward a common asymptotic value independent of both the length of the rod and the presence of electrode enhancements. The observed behavior is supported by numerical simulation of electric field and current density distributions, indicating that the high current performance of a grounding rod is heavily influenced by soil ionization and breakdown in high-field regions at the electrode extremities.