scholarly journals Optimized Protection of Pole-Mounted Distribution Transformers against Direct Lightning Strikes

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4372 ◽  
Author(s):  
Mahdi Pourakbari-Kasmaei ◽  
Farhan Mahmood ◽  
Matti Lehtonen
Keyword(s):  
Weather Conditions ◽  
Lightning Strikes ◽  
Medium Voltage ◽  
Distribution Transformers ◽  
Depth Analysis ◽  
System Operator ◽  
Efficient Protection ◽  
Phase Conductors ◽  
Soil Ionization

Direct lightning strikes on overhead phase conductors result in high overvoltage stress on the medium voltage (MV) terminals of pole-mounted transformers, which may cause considerable damage. Therefore, introducing an efficient protection strategy would be a remedy for alleviating such undesirable damages. This paper investigates the optimized protection of MV transformers against direct lightning strikes on the phase conductors. To this end, first, the impacts of grounding densities (number of grounded intermediate poles between every two successive transformer poles) on the probability of overvoltage stress on transformer terminals are investigated. Then, the implications of guy wire, as a supporting device for ungrounded intermediate poles, on reducing the overvoltage stress on transformers, are studied. Finally, the role of a surge arrester in mitigating the overvoltage stress of non-surge-arrester-protected transformer poles is scrutinized. The investigations are conducted on a sample MV network with 82 wood poles comprising 17 pole-mounted transformers protected by spark gaps. To provide in-depth analysis, two different poles, namely creosote- and arsenic-impregnated poles, are considered under wet and dry weather conditions. A sensitivity analysis is performed on grounding distances and on a combination of guy wire and grounded intermediate poles while taking into account soil ionization. The results provide a clear picture for the system operator in deciding how many grounded intermediate poles might be required for a system to reach the desired probabilities of transformers experiencing overvoltage stress and how the surge arrester and guy wires contribute to mitigating undesirable overvoltage stress.

Simulation of the Lightning Back-Flashover for Medium Voltage Distribution Network

2016 ◽  
Vol 3 (2) ◽  
pp. 264
Author(s):  
Osama El-Sayed Gouda ◽  
Noura Ahmed Elshesheny
Keyword(s):  
Distribution Network ◽  
Overhead Line ◽  
Voltage Distribution ◽  
Lightning Strikes ◽  
Factors Affecting ◽  
Analysis Study ◽  
Medium Voltage ◽  
Distribution Lines ◽  
Soil Ionization

Lightning strikes represent a considerable cause of short interruptions in electrical overhead line networks. The over voltages caused by lightning cannot be avoided but their influence can be limited by appropriate over voltage protection. This paper presents analysis study on some factors affecting the back flashover of Egyptian 66 kV distribution lines using Alternative Transient Program (ATP). The study includes the modeling of 66 kV distribution lines, the effects of magnitude and the front and tail times of lightning wave on the back flashover voltages, the effects of the striking distance, and the using of counterpoise wires on the back flashover on the 66 kV line towers. In this paper the 66 kV lines sag is neglected and the soil ionization by the flow of the stroke current is considered.

scholarly journals Phosphorylation of Serine 11 and Serine 92 as New Positive Regulators of Human Snail1 Function: Potential Involvement of Casein Kinase-2 and the cAMP-activated Kinase Protein Kinase A

2010 ◽  
Vol 21 (2) ◽  
pp. 244-253 ◽  
Author(s):  
Matthew Reid MacPherson ◽  
Patricia Molina ◽  
Serhiy Souchelnytskyi ◽  
Christer Wernstedt ◽  
Jorge Martin-Pérez ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Tumor Metastasis ◽  
Epithelial Mesenchymal Transition ◽  
Cop9 Signalosome ◽  
Mesenchymal Transition ◽  
Depth Analysis ◽  
Positive Regulators

Snail1 is a major factor for epithelial-mesenchymal transition (EMT), an important event in tumor metastasis and in other pathologies. Snail1 is tightly regulated at transcriptional and posttranscriptional levels. Control of Snail1 protein stability and nuclear export by GSK3β phosphorylation is important for Snail1 functionality. Stabilization mechanisms independent of GSK3β have also been reported, including interaction with LOXL2 or regulation of the COP9 signalosome by inflammatory signals. To get further insights into the role of Snail1 phosphorylation, we have performed an in-depth analysis of in vivo human Snail1 phosphorylation combined with mutational studies. We identify new phosphorylation sites at serines 11, 82, and 92 and confirmed previously suggested phosphorylations at serine 104 and 107. Serines 11 and 92 participate in the control of Snail1 stability and positively regulate Snail1 repressive function and its interaction with mSin3A corepressor. Furthermore, serines 11 and 92 are required for Snail1-mediated EMT and cell viability, respectively. PKA and CK2 have been characterized as the main kinases responsible for in vitro Snail1 phosphorylation at serine 11 and 92, respectively. These results highlight serines 11 and 92 as new players in Snail1 regulation and suggest the participation of CK2 and PKA in the modulation of Snail1 functionality.

Speciation and changes in male gene expression in Drosophila

Genome ◽  
2020 ◽  
pp. 1-11
Author(s):  
Bahar Patlar ◽  
Alberto Civetta
Keyword(s):  
Gene Expression ◽  
Reproductive Isolation ◽  
Potential Role ◽  
Regulation Of Gene Expression ◽  
Drosophila Model ◽  
Depth Analysis ◽  
The Impact ◽  
Plastic Responses ◽  
Male Gene

It has long been acknowledged that changes in the regulation of gene expression may account for major organismal differences. However, we still do not fully understand how changes in gene expression evolve and how do such changes influence organisms’ differences. We are even less aware of the impact such changes might have in restricting gene flow between species. Here, we focus on studies of gene expression and speciation in the Drosophila model. We review studies that have identified gene interactions in post-mating reproductive isolation and speciation, particularly those that modulate male gene expression. We also address studies that have experimentally manipulated changes in gene expression to test their effect in post-mating reproductive isolation. We highlight the need for a more in-depth analysis of the role of selection causing disrupted gene expression of such candidate genes in sterile/inviable hybrids. Moreover, we discuss the relevance to incorporate more routinely assays that simultaneously evaluate the potential effects of environmental factors and genetic background in modulating plastic responses in male genes and their potential role in speciation.

scholarly journals How to introduce new technologies to reduce nutrient losses: a case of Danish agricultural constructed wetlands

Water Policy ◽  
2017 ◽  
Vol 19 (3) ◽  
pp. 404-422 ◽  
Author(s):  
Florence Gathoni Gachango ◽  
Brian H. Jacobsen
Keyword(s):  
Constructed Wetlands ◽  
Implementation Strategy ◽  
New Technologies ◽  
Secondary Data ◽  
Policy Instrument ◽  
Nutrient Losses ◽  
Voluntary Approach ◽  
Depth Analysis ◽  
Environmental Measures

The Water Framework Directive (WFD) focuses on reduction of nutrients in individual water bodies. Innovative drainage filter technologies currently being tested in Denmark could facilitate nutrient reductions at the sub-river basins and catchment levels. The implementation strategy for these technologies, however, remains a challenge. Using both primary and secondary data, this paper presents an in-depth analysis of the role of these technologies in implementation of the WFD in Denmark. Concepts of impact assessment are used to identify the most suitable approach for incorporating these technologies into environmental measures based on a three-faceted policy instrument typology. A voluntary approach supported by investment subsidies, or incentives that could replace existing requirements, is deemed more appropriate.

The role of forest deadwood in rockfall protection

2021 ◽  
Author(s):  
Adrian Ringenbach ◽  
Peter Bebi ◽  
Perry Bartelt ◽  
Andrin Caviezel
Keyword(s):  
Basal Area ◽  
Spruce Forest ◽  
Runout Distance ◽  
In Situ Sensors ◽  
Efficient Protection ◽  
Cost Efficient ◽  
Study Sites ◽  
Rockfall Protection

<p>Forests with a high density and basal area of living trees are known for their function as natural and cost-efficient protection against rockfall. The role of deadwood, however, is less understood. We address this knowledge gap in this contribution as we present the results of repeated real-scale experiments in a) a montane beech-spruce forest with and without deadwood and b) in a subalpine scrub mountain pine-spruce forest with deadwood. We used artificial rocks with either an equant or platy shape, masses between 45 kg and 800 kg (≈ 0.3 m3), and equipped with in-situ sensors to gain insights into rotational velocities and impact-accelerations. Clusters of deadwood and erected root plates reduced the mean runout distance at both study sites. For site a), we found that more rocks were stopped behind lying than living trees and that the stopping effect of deadwood was greater for equant compared to platy rock shapes. Site b) revealed a braking effect of scrub mountain pines for relatively small (45 kg), but also a visible reduction in rotational velocities for the 800 kg rocks sensor stream. We conclude that deadwood must be taken into account in rockfall modeling and the management of rockfall protection forests.</p>

scholarly journals Production choices with water markets and risk aversion: the role of initial allocations and forward trading

2018 ◽  
Vol 46 (4) ◽  
pp. 579-608 ◽  
Author(s):  
Philippe Bontems ◽  
Céline Nauges
Keyword(s):  
Irrigation Water ◽  
Weather Conditions ◽  
Water Markets ◽  
Initial Water ◽  
Production Risk ◽  
Net Returns ◽  
Murray Darling Basin ◽  
Forward Trading ◽  
Allocation Decisions

Abstract We develop a theoretical model that describes risk-averse farmers’ decisions when facing production risk due to uncertain weather conditions and when irrigation water can be traded on a market. We focus on the role of initial water allocations granted to irrigated farms at the start of the season. The presence of water markets makes the future water price uncertain and hence the value of initial water allocations uncertain. We analyse the properties of this background risk and study how initial water allocations impact farmers’ land allocation decisions between an irrigated crop and a non-irrigated crop, both characterised by random expected net returns. We then extend the model by permitting irrigation water to be traded ex-ante at a known price (forward market). Finally, we illustrate our main theoretical findings using simulations. We calibrate distributions of the random variables based on observed data from the Murray–Darling Basin in Australia where a water market has been in place for several decades.

The role of short-term weather conditions in temporal dynamics of fire regime features in mainland Spain

2019 ◽  
Vol 241 ◽  
pp. 575-586 ◽  
Author(s):  
Adrián Jiménez-Ruano ◽  
Marcos Rodrigues Mimbrero ◽  
W. Matt Jolly ◽  
Juan de la Riva Fernández
Keyword(s):  
Temporal Dynamics ◽  
Fire Regime ◽  
Weather Conditions ◽  
Short Term

scholarly journals Reproductive Success of American Kestrels: The Role of Prey Abundance and Weather

The Condor ◽  
2000 ◽  
Vol 102 (4) ◽  
pp. 814-822 ◽  
Author(s):  
Russell D. Dawson ◽  
Gary R. Bortolotti
Keyword(s):  
Reproductive Success ◽  
Natural Variation ◽  
Weather Conditions ◽  
Prey Abundance ◽  
Offspring Size ◽  
Minimum Threshold ◽  
Provisioning Behavior ◽  
American Kestrels ◽  
Parental Provisioning

Abstract We investigated how natural variation in abundance and availability of the main prey of American Kestrels (Falco sparverius), small mammals, influenced provisioning rates by parents, and offspring size and survival. Provisioning behavior of kestrels was not constrained by the abundance of food in the environment; however, the availability of food, mediated through variation in weather, appeared to significantly influence parental provisioning behavior. Moreover, variation in weather had clear effects on reproductive success because nestlings exposed to inclement weather were smaller and lighter at fledging, and less likely to survive to fledging, compared to nestlings raised during good weather conditions. Prey abundance was not related to offspring size or survival. Our results suggest American Kestrels are limited by the availability, as opposed to abundance, of food on territories. It is likely that during our study, prey abundance was above some minimum threshold necessary to support successful reproduction, and so variation in weather affected reproduction more than variation in prey abundance.

Sign in / Sign up

Export Citation Format

Share Document