Unsteady magnetohydrodynamic mixed convection flow with heat and mass transfer over a horizontal circular cylinder embedded in a porous medium

The objective of the present study is to investigate the effect of flow parameters on the mixed convection heat and mass transfer of an unsteady magnetohydrodynamic flow of an electrically conducting, viscous, and incompressible fluid over a horizontal circular cylinder embedded in porous medium, considering effects of chemical reaction and heat source/sink, by taking into account viscous dissipation. The present magnetic field is homogenous and perpendicular to the body surface. Magnetic Reynolds number is significantly lower than one i. e. considered the problem is in approximation without induction. The governing non-linear partial differential equations and associated boundary conditions are made dimensionless using a suitable similarity transformation and similarity parameters. System of non-dimensionless equations are solved numerically by implicit finite difference three-diagonal and iteration method. Numerical results obtained for different values of porous medium, magnetic, diffusion and temperature parameters, buoyancy diffusion parameter and thermal parameter and for different values Prandtl, Echart, and Schmidt numbers. Variation of velocity, temperature and concentration and many integral and differential characteristics boundary layer are discussed and shown graphically

MHD effects on unstedy dynamic, thermal and diffusion boundary layer flow over a horizontal circular cylinder

This paper is devoted to the analysis of unsteady two-dimensional dynamic, thermal and diffusion magnetohydrodynamic laminar boundary layer flow over a horizontal circular cylinder of incompressible and electrical conductivity fluid, in a porous medium, in the presence of a heat source or sink, and chemical reactions. The present magnetic field is homogenous and perpendicular to the body surface. It is assumed that the induction of the outer magnetic field is the function of the longitudinal coordinate and time. Fluid electrical conductivity is constant. The outer electric field is neglected and the magnetic Reynolds number is significantly lower than one i. e. the considered the problem is in induction-less approximation. Free stream velocity, temperature and concentration on the body are arbitrary differentiable functions. The developed governing boundary layer equations and associated boundary conditions are converted into a nondimensional form using a suitable similarity transformation and similarity parameters. The system of dimensionless equations is solved using the finite difference method and iteration method. Numerical results are obtained and presented for incompressible fluid for different numbers, such as Sc, Pr, Ec and magnetic number, and the parameter of the porous medium, temperature parameters, thermal parameter, diffusion parameters and chemical reaction parameter. The solutions for the flow, temperature and diffusion transfer and other integral characteristics, boundary layer, are evaluated numerically for different values of the magnetic field. Transient effects of velocity, temperature and diffusion are analyzed. A part of obtained results is given in the form of figures and corresponding conclusions

Utility of CK8, CK10, CK13, and CK17 in Differential Diagnostics of Benign Lesions, Laryngeal Dysplasia, and Laryngeal Squamous Cell Carcinoma

There are no reliable immunohistochemical markers for diagnosing laryngeal squamous cell carcinoma (SCC) or diagnosing and grading laryngeal dysplasia. We aimed to evaluate the diagnostic utility of CK8, CK10, CK13, and CK17 in benign laryngeal lesions, laryngeal dysplasia, and laryngeal SCC. This retrospective study included 151 patients diagnosed with laryngeal papilloma, laryngeal polyps, laryngeal dysplasia, and laryngeal SCC who underwent surgical treatment between 2010 and 2020. Immunohistochemistry (IHC) was carried out using specific monoclonal antibodies against CK8, CK10, CK13, and CK17. Two experienced pathologists performed semi-quantitative scoring of IHC positivity. The diagnostic significance of the markers was analyzed. CK13 showed a sensitivity of 100% and a specificity of 82.5% for distinguishing between laryngeal SCC and laryngeal dysplasia and benign lesions. CK17 showed a sensitivity of 78.3% and specificity of 57.1% for the detection of laryngeal SCC vs. laryngeal dysplasia. CK10 showed a sensitivity of 80.0% for discriminating between low-grade and high-grade dysplasia, and a specificity of 61.1%. Loss of CK13 expression is a reliable diagnostic tool for diagnosing laryngeal lesions with malignant potential and determining resection lines. In lesions with diminished CK13 expression, CK17 could be used as an auxiliary immunohistochemical marker in diagnosing laryngeal SCC. In CK13-negative and CK17-positive lesions, CK10 positivity could be used to determine low-grade dysplasia. CK8 is not a useful IHC marker in differentiating between benign laryngeal lesions, laryngeal dysplasia, and laryngeal SCC

Quantifying the Severity of Short-term Instability Voltage Deviations

As power systems evolve from synchronous to inverter-based generation, voltage stability plays an increasingly important role. Voltage perturbations become faster and highly variable, and as such attract the research interest in the field of short-term instability monitoring and evaluation. The digitalization of the power systems provides a higher degree of observability by making use of synchrophasor measurements. The next step of utilizing such measurements by tailoring and applying innovative analytical and data-driven solutions is, however, still at the early development stage. In this paper, a novel approach that utilizes rapid post-fault voltage deviations for short-term instability quantification is investigated. The findings indicate that the approach is intuitive and effective. Finally, the paper discusses future research directions, enabled by the presented methodology, that deal with grid resilience challenges. Particularly, those related to post-disturbance system strength evaluation, as well as the real-time short-term instability evaluation and prediction, are addressed

Beyond SCR in Weak Grids: Analytical Evaluation of Voltage Stability and Excess System Strength

Due to the continuous increase (decrease) in the number of inverter-based (synchronous) generators in modern electrical power systems, the theoretical foundations behind widely used system strength and voltage stability assessment methods require thorough revision. The existing evaluation methods such as the Short-Circuit Ratio (SCR) are often based on simplifications which may produce inaccuracies, particularly when studying weak systems. As a result, a misleading estimation of voltage stability can occur, exposing systems to unnecessary renewables curtailment or other inappropriate remedial actions that may cause partial disruptions or potential instability. This paper provides a rigorous analytical revision of voltage stability assessment to confidently evaluate the maximum power transfer under various operating conditions. Subsequently, the proposed approach is applied as an enhanced method of system strength evaluation. The method is extensively tested on a single-machine-infinite-bus test system. Numerical results show a notably more accurate assessment relative to the common alternative methods.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid

System Strength: Classification, Evaluation Methods, and Emerging Challenges in IBR-dominated Grids

To facilitate the increasing penetration of inverter-based resources, understanding and evaluating system strength becomes one of the central questions for the resilient operation of power systems. However, this is a very challenging and nuanced task, currently without a clear consensus in the industry and academia. This paper provides a comprehensive review of the proposed notion for system strength, followed by a consequent introduction of a novel classification. Furthermore, an exhaustive examination of present system strength evaluation methods is performed. Finally, a critical outlook on remaining and emerging challenges of system strength evaluation is presented, with several key recommendations for future research directions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid

Oplossingsrichtingen voor congestie in middenspanningsnetten: de casus Buiksloterham-Zuid/Overhoeks Amsterdam

Door middel van een zo representatief mogelijk rekenmodel voor het middenspanningsnet van de Amsterdamse gebieden Buiksloterham-Zuid/Overhoeks (BZOH), heeft het onderzoeksteam een detailanalyse kunnen uitvoeren naar de verwachte leveringscongestie in dit gebied zoals aangekondigd door Liander op 24 juni 2021. De detailanalyse laat een grootschalige toename in elektriciteitsverbruik in 3 jaar tijd zien, voornamelijk vanwege de stedelijke ontwikkeling in Overhoeks. Uit de beperkte beschikbare data en de resultaten uit het rekenmodel blijkt dat deze toename in vermogensvraag in het middenspanningsnet boven de normale beleidsgrenzen komt totdat de realisatie van de geplande netuitbreiding halverwege 2023 gereed is. De capaciteit is vooral ontoereikend in storings- en/of onderhoudssituaties, ook wel verschakelde toestand genoemd, in bepaalde delen van het netwerk. De studie laat zien dat het effectief verschakelen van het netwerk door Liander een groot deel van het capaciteitsprobleem vermindert. Er bestaan meerdere mogelijkheden om de configuratie van het net aan te passen om zowel in normaal bedrijf als in storings- en/of onderhoudssituaties belastingen beter in het netwerk te kunnen integreren. Een optimale netwerktopologie is daarom noodzakelijk om capaciteit vrij te spelen. In combinatie met een alternatieve reservestelling voor storing en onderhoud (t.o.v. de huidige reservecapaciteit in het netwerk) blijkt dat kritieke netsituaties voorkomen kunnen worden. Om tot een kosteneffectieve en uitvoerbare inschatting te komen voor de dimensionering en locatie van de alternatieve reservestelling, is het detailniveau van netanalyse cruciaal en is voor het toepassen van een alternatieve reservestelling in BZOH een kalibratie van deze studie door Liander noodzakelijk. Daarbij kan de detailanalyse inzichten bieden om in tijden van congestie het overschrijden van de normale beleidsgrenzen omtrent kabelbelasting tijdelijk toe te staan onder de veilige omstandigheden. Op basis van de resultaten uit deze studie zijn deze opties voor reservestelling vanuit energetisch perspectief kansrijk voor BZOH, zonder een verdere uitwerking te bieden voor implementatie.Intelligent Electrical Power Grid

Synchrophasor-based Applications to Enhance Electrical System Performance in the Netherlands

This paper deals with the essentials of synchrophasor applications for future power systems aimed at increasing system reliability and resilience. In this work, several applications are presented, covering real-time disturbance detection and blackout prevention. Firstly, an advanced big-data management platform built in real-time digital simulation (RTDS) environment to support measurement data collection, processing and sharing among stakeholders is described. With this platform, a network splitting methodology to avoid cascading failures is presented and demonstrated, which upon the occurrence of a disturbance successfully isolates the affected part to avoid catastrophic cascade system outage. Online generator coherency identification is another synchrophasor application implemented on the platform, whose use is demonstrated in the context of controlled network splitting. By using synchrophasors, data-analytics techniques can also be used for identifying and classifying different disturbances in real-time with the least human intervention. Therefore, a novel centralized artificial intelligence (AI) based expert system to detect and classify critical events is outlined. Finally, the paper elaborates on the development of advanced system resilience metrics for real-time vulnerability assessment, with a focus on increasingly relevant dynamic interactions between distribution and transmission systems

Synchrophasor-based Applications to Enhance Electrical System Performance in the Netherlands

This paper deals with the essentials of synchrophasor applications for future power systems aimed at increasing system reliability and resilience. In this work, several applications are presented, covering real-time disturbance detection and blackout prevention. Firstly, an advanced big-data management platform built in real-time digital simulation (RTDS) environment to support measurement data collection, processing and sharing among stakeholders is described. With this platform, a network splitting methodology to avoid cascading failures is presented and demonstrated, which upon the occurrence of a disturbance successfully isolates the affected part to avoid catastrophic cascade system outage. Online generator coherency identification is another synchrophasor application implemented on the platform, whose use is demonstrated in the context of controlled network splitting. By using synchrophasors, data-analytics techniques can also be used for identifying and classifying different disturbances in real-time with the least human intervention. Therefore, a novel centralized artificial intelligence (AI) based expert system to detect and classify critical events is outlined. Finally, the paper elaborates on the development of advanced system resilience metrics for real-time vulnerability assessment, with a focus on increasingly relevant dynamic interactions between distribution and transmission systems.Intelligent Electrical Power Grid