bluuebunny/crossref_metadata_2025 huggingface dataset:
Annexin A2 overexpression associates with colorectal cancer invasiveness and TGF-ß induced epithelial mesenchymal transition via Src/ANXA2/STAT3
Authors: Rocha Murilo R. , Barcellos-de-Souza Pedro , Sousa-Squiavinato Annie Cristhine M. , Fernandes Priscila V. , de Oliveira Ivanir M. , Boroni Mariana , Morgado-Diaz Jose A.
Published: July 2018

Annexin A2 (ANXA2) is upregulated in several malignancies, including colorectal cancer (CRC). However, there is little knowledge on the molecular mechanisms involved to its upregulation. The aim of this study was to identify the mechanism through which ANXA2 overexpression leads to CRC progression and evaluate its potential prognostic value. We used human CRC samples to analyse the correlation between ANXA2 levels and tumour staging. ANXA2 expression was increased in CRC tissues compared to normal colon tissues. In addition, we observe increased ANXA2 levels in stage IV tumours and metastasis, when compared to stage I-III. Whereas E-cadherin, an epithelial marker, decreased in stage II-IV and increased in metastasis. We’ve also shown that TGF-β, a classic EMT inductor, caused upregulation of ANXA2, and internalization of both E-cadherin and ANXA2 in CRC cells. ANXA2 silencing hindered TGF-β-induced invasiveness, and inhibitors of the Src/ANXA2/STAT3 pathway reversed the EMT. In silico analysis confirmed overexpression of ANXA2 and association to the consensus moleculars subtypes (CMS) with the worst prognosis. Therefore, ANXA2 overexpression play a pivotal role in CRC invasiveness through Src/ANXA2/STAT3 pathway activation. The association of ANXA2 to distinct CMSs suggests the possible use of ANXA2 as a prognostic marker or directed target therapy.
The identification of novel single nucleotide polymorphisms to assist in mapping the spread of Bacillus anthracis across the Southern Caucasus
Authors: Sahin Mitat , Buyuk Fatih , Baillie Les , Wölfel Roman , Kotorashvili Adam , Rehn Alexandra , Antwerpen Markus , Grass Gregor
Published: July 2018

Anthrax is common as a zoonotic disease in the southern Caucasus area including parts of Turkey and Georgia. In this region, population genetics of the etiological agent Bacillus anthracis comprises, where known, the major canonical single nucleotide polymorphism (canSNP) groups A.Br.Aust94 and A.Br.008/009 of the pathogen’s global phylogeny, respectively. Previously, isolates of B. anthracis from Turkey have been genotyped predominantly by multi locus variable number of tandem repeat analysis (MLVA) or canSNP typing. While whole genome sequencing is the future gold standard, it is currently still costly. For that reason we were interested in identifying novel SNPs which could assist in further distinguishing closely related isolates using low cost assay platforms. In this study we sequenced the genomes of seven B. anthracis strains collected from the Kars province of Eastern Anatolia in Turkey and discovered new SNPs which allowed us to assign these and other geographically related strains to three novel branches of the major A-branch canSNP-group (A.Br.) Aust94. These new branches were named Kafkas-Geo 1–3 and comprised isolates from the Kars region and the neighboring republic of Georgia suggesting a common ancestry. The novel SNPs identified in this study connect the population genetics of B. anthracis in the South Caucasus and Turkey and will likely assist efforts to map the spread of the pathogen across this region.
Versatile etherification of alcohols with allyl alcohol by a titanium oxide-supported molybdenum oxide catalyst: gradual generation from titanium oxide and molybdenum oxide
Authors: Kon Yoshihiro , Fujitani Tadahiro , Nakashima Takuya , Murayama Toru , Ueda Wataru
Published: July 2018

A sustainable method to synthesize allyl ethers from allyl alcohol by the simple mixing of TiO2 and MoO3 catalysts.
Effect of the acidity of HZSM-5/MCM-41 hierarchical zeolite on its catalytic performance in supercritical catalytic cracking ofn-dodecane: experiments and mechanism
Authors: Xian Xiaochao , Ran Chao , Yang Peng , Chu Yirong , Zhao Shuo , Dong Lichun
Published: July 2018

Tuning the acidity of ZSM-5/MCM-41 hierarchical zeolite by ion exchange with NaCl can enhance its stability for supercritical catalytic cracking.
Novel double layer film composed of reduced graphene oxide and Rose Bengal dye: design, fabrication and evaluation as an efficient chemosensor for silver(i) detection
Authors: Sarafbidabad Mohsen , Parsaee Zohreh , Noor Mohammadi Zahra , Karachi Nima , Razavi Razieh
Published: July 2018

A novel silver-chemosensor fabricated with reduced graphene oxide and Rose Bengal (RB) based on the interaction of Ag+ and RB.
Investigations into the biosynthesis of the antifungal strobilurins
Authors: Iqbal Zafar , Han Li-Chen , Soares-Sello Anna M. , Nofiani Risa , Thormann Gerald , Zeeck Axel , Cox Russell J. , Willis Christine L. , Simpson Thomas J.
Published: July 2018

Prestrobilurin A, formedviabenzoate and cinnamate, has been identified as the first enzyme free intermediate in strobilurin biosynthesis.
Influence of amino acid sequence in a peptidic Cu+-responsive luminescent probe inspired by the copper chaperone CusF
Authors: Roux A. , Isaac M. , Chabert V. , Denisov S. A. , McClenaghan N. D. , Sénèque O.
Published: July 2018

Amino acid sequence influences the luminescence behavior of a family of bio-inspired Cu+-responsive probes.
Straightforward synthesis of quinolines from enones and 2-aminobenzyl alcohols using an iridium-catalyzed transfer hydrogenative strategy
Authors: Xiong Biao , Wang Yingying , Liu Yuan , Bao Yandan , Liu Zhaoguo , Zhang Yanan , Ling Yong
Published: July 2018

Synthesis of quinolines via transfer hydrogenative coupling with high step- and atom efficiency, mild conditions and operational simplicity.
Divergent outcomes of gut microbiota alteration upon use of spectrum antibiotics in high sugar diet-induced diabetes in rats
Authors: Prajapati Bhumika , Jena Prasant Kumar , Patel Sweta , Seshadri Sriram
Published: July 2018

A sugar rich diet induces inflammation and insulin resistance (IR) mainly through gut microbiota alteration.
Dendritic cells trigger imbalance of Th1/Th2 cells in silica dust exposure rat model via MHC-II, CD80, CD86 and IL-12
Authors: Bao Lei , Hao Changfu , Liu Suna , Zhang Lin , Wang Juan , Wang Di , Li Yiping , Yao Wu
Published: July 2018

Dendritic cells (DCs), the most powerful antigen presentation cell (APC) in the immune response, play a crucial role in silicosis.
Development of a Pichia pastoris whole-cell biocatalyst with overexpression of mutant lipase I PCLG47I from Penicillium cyclopium for biodiesel production
Authors: Liu Yihan , Huang Lin , Zheng Dong , Fu Yu , Shan Mengying , Xu Zehua , Ma Jieying , Lu Fuping
Published: July 2018

Biodiesel is efficiently produced by a lipase whole-cell biocatalyst with high activity and thermostability at low temperature.
8-Hydroxy-2-methylquinoline-modified H4SiW12O40: a reusable heterogeneous catalyst for acetal/ketal formation
Authors: Liu Li-jun , Luan Qing-jie , Lu Jing , Lv Dong-mei , Duan Wen-zeng , Wang Xu , Gong Shu-wen
Published: July 2018

A heteropoly acid based organic hybrid heterogeneous catalyst, HMQ-STW, was prepared by combining 8-hydroxy-2-methylquinoline (HMQ) with Keggin-structured H4SiW12O40 (STW).
Differences in gut microbiota between silkworms (Bombyx mori) reared on fresh mulberry (Morus albavar. multicaulis) leaves or an artificial diet
Authors: Dong Hui-Ling , Zhang Sheng-Xiang , Chen Zhuo-Hua , Tao Hui , Li Xue , Qiu Jian-Feng , Cui Wen-Zhao , Sima Yang-Hu , Cui Wei-Zheng , Xu Shi-Qing
Published: July 2018

Artificial diets for silkworms have many potential applications and they are important in sericulture.
Flexible top-emitting organic light emitting diodes with a functional dielectric reflector on a metal foil substrate
Authors: Hong Kihyon , Yu Hak Ki , Lee Illhwan , Kim Sungjun , Kim Youngho , Kim Kisoo , Lee Jong-Lam
Published: July 2018

We demonstrated flexible OLEDs with a DBR serving as an optical reflector and electrical passivation on a metal foil substrate.
Flow synthesis of coumalic acid and its derivatization
Authors: Smith Laura K. , Baxendale Ian R.
Published: July 2018

Coumalic acid is a valuable platform compound which can be prepared from malic acid, a biorenewable feedstock derived from glucose. Two flow syntheses of coumalic acid and a new heated rotating reactor are presented.
A mononuclear nonheme {FeNO}6 complex: synthesis and structural and spectroscopic characterization
Authors: Hong Seungwoo , Yan James J. , Karmalkar Deepika G. , Sutherlin Kyle D. , Kim Jin , Lee Yong-Min , Goo Yire , Mascharak Pradip K. , Hedman Britt , Hodgson Keith O. , Karlin Kenneth D. , Solomon Edward I. , Nam Wonwoo
Published: July 2018

X-ray structures of nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand are reported along with three different generation pathways.
Highly efficient perovskite solar cells based on a dopant-free conjugated DPP polymer hole transport layer: influence of solvent vapor annealing
Authors: Guo Xing , Zhang Bingjuan , Lin Zhenhua , Su Jie , Yang Zhou , Zhang Chunfu , Chang Jingjing , Liu Shengzhong (Frank) , Hao Yue
Published: July 2018

The solvent vapor annealing effect on conjugated polymer thin films as well as the corresponding perovskite solar cell devices is investigated.
Nickel–copper supported on a carbon black hydrogen oxidation catalyst integrated into an anion-exchange membrane fuel cell
Authors: Roy Aaron , Talarposhti Morteza R. , Normile Stanley J. , Zenyuk Iryna V. , De Andrade Vincent , Artyushkova Kateryna , Serov Alexey , Atanassov Plamen
Published: July 2018

This work introduces the first practical platinum group metal-free (PGM-free) electrocatalyst for the hydrogen oxidation reaction (HOR) in alkaline membrane fuel cells (AMFC), based on nickel-rich Ni95Cu5-alloy nanoparticles.
Iron(iii)-based metal–organic frameworks as oxygen-evolving photocatalysts for water oxidation
Authors: Qu Ling-Ling , Wang Jun , Xu Tian-Yi , Chen Qiu-Yun , Chen Jie-Hui , Shi Chao-Jie
Published: July 2018

Development of economical and highly efficient catalysts to achieve visible light-induced water oxidation is a potential approach to mitigate energy shortage and global warming.
Unusual polysaccharide rheology of aqueous dispersions of soft phytoglycogen nanoparticles
Authors: Shamana Hurmiz , Grossutti Michael , Papp-Szabo Erzsebet , Miki Carley , Dutcher John R.
Published: July 2018

Dense dispersions of phytoglycogen nanoparticles in water are a simple experimental realization of a soft colloidal glass.
Alignment of twisted nanoribbons formed by C17H35CO-Val-Ala sodium salts
Authors: Tong Qiyun , Zhang Lianglin , Li Yi , Li Baozong , Yang Yonggang
Published: July 2018

Twisted nanoribbons formed by the lipodipeptide sodium salts can be aligned in a parallel fashion under directional force.
Structure and properties of polydisperse polyelectrolyte brushes studied by self-consistent field theory
Authors: Okrugin Boris M. , Richter Ralf P. , Leermakers Frans A. M. , Neelov Igor M. , Borisov Oleg V. , Zhulina Ekaterina B.
Published: July 2018

Two complementary self-consistent field theoretical approaches are used to analyze the equilibrium structure of binary and ternary brushes of polyions with different degrees of polymerization.
Effects of additives on the viscoelastic responses of cationic gemini surfactant solutions
Authors: Chen Xiao-Xiao , Liu Qi , Guo Yan , Yan Hui , Li Jing , Lv Dong-Mei , Zhang Jun-Hong , Liu Min , Yao Chun-Hong , Wei Xi-Lian
Published: July 2018

The viscoelastic behavior of cationic gemini surfactant solutions shows high sensitivity to the attributes and molecular structure of various additives.
Harnessing fold-to-wrinkle transition and hierarchical wrinkling on soft material surfaces by regulating substrate stiffness and sputtering flux
Authors: Yu Senjiang , Sun Yadong , Li Shichen , Ni Yong
Published: July 2018

We developed a facile technique to harness fold-to-wrinkle transition and hierarchical wrinkling on soft material surfaces by regulating substrate stiffness and sputtering flux.
Bioinspired sea-sponge nanostructure design of Ni/Ni(HCO3)2-on-C for a supercapacitor with a superior anti-fading capacity
Authors: Wu Qing Nan , Wen Jia Hao , Wen Ming , Wu Qing Sheng , Fu Yong Qing
Published: July 2018

Rational design of novel structures plays a key role in achieving high specific capacities and fast charge rates with a long cycling life for battery-type electrodes of supercapacitors.
Actuating thermo- and photo-responsive tubes from liquid crystalline elastomers
Authors: Braun Lukas B. , Hessberger Tristan , Pütz Eva , Müller Carsten , Giesselmann Frank , Serra Christophe A. , Zentel Rudolf
Published: July 2018

Long actuating tubes (both thermo- and photo-responsive) made of liquid crystalline elastomers can be prepared in a microfluidic setup.
Clinical syndromes associated with mtDNA mutations: where we stand after 30 years
Authors: Carelli Valerio , La Morgia Chiara
Published: July 2018

The landmark year 1988 can be considered as the birthdate of mitochondrial medicine, when the first pathogenic mutations affecting mtDNA were associated with human diseases. Three decades later, the field still expands and we are not ‘scraping the bottom of the barrel’ yet. Despite the tremendous progress in terms of molecular characterization and genotype/phenotype correlations, for the vast majority of cases we still lack a deep understanding of the pathogenesis, good models to study, and effective therapeutic options. However, recent technological advances including somatic cell reprogramming to induced pluripotent stem cells (iPSCs), organoid technology, and tailored endonucleases provide unprecedented opportunities to fill these gaps, casting hope to soon cure the major primary mitochondrial phenotypes reviewed here. This group of rare diseases represents a key model for tackling the pathogenic mechanisms involving mitochondrial biology relevant to much more common disorders that affect our currently ageing population, such as diabetes and metabolic syndrome, neurodegenerative and inflammatory disorders, and cancer.
Mitochondrial dynamics: overview of molecular mechanisms
Authors: Tilokani Lisa , Nagashima Shun , Paupe Vincent , Prudent Julien
Published: July 2018

Mitochondria are highly dynamic organelles undergoing coordinated cycles of fission and fusion, referred as ‘mitochondrial dynamics’, in order to maintain their shape, distribution and size. Their transient and rapid morphological adaptations are crucial for many cellular processes such as cell cycle, immunity, apoptosis and mitochondrial quality control. Mutations in the core machinery components and defects in mitochondrial dynamics have been associated with numerous human diseases. These dynamic transitions are mainly ensured by large GTPases belonging to the Dynamin family. Mitochondrial fission is a multi-step process allowing the division of one mitochondrion in two daughter mitochondria. It is regulated by the recruitment of the GTPase Dynamin-related protein 1 (Drp1) by adaptors at actin- and endoplasmic reticulum-mediated mitochondrial constriction sites. Drp1 oligomerization followed by mitochondrial constriction leads to the recruitment of Dynamin 2 to terminate membrane scission. Inner mitochondrial membrane constriction has been proposed to be an independent process regulated by calcium influx. Mitochondrial fusion is driven by a two-step process with the outer mitochondrial membrane fusion mediated by mitofusins 1 and 2 followed by inner membrane fusion, mediated by optic atrophy 1. In addition to the role of membrane lipid composition, several members of the machinery can undergo post-translational modifications modulating these processes. Understanding the molecular mechanisms controlling mitochondrial dynamics is crucial to decipher how mitochondrial shape meets the function and to increase the knowledge on the molecular basis of diseases associated with morphology defects. This article will describe an overview of the molecular mechanisms that govern mitochondrial fission and fusion in mammals.
Stackelberg game for price and power control in secure cooperative relay network
Authors: Chopra Khyati , Bose Ranjan , Joshi Anupam
Published: July 2018

In this study, the authors propose a scheme based on Stackelberg game for price and power control in threshold‐based relay network, where the source transmits message to destination with the cooperation of a relay, in the presence of an eavesdropper. The relay gets revenue for transmitting the source information and the source profits from the cooperation secrecy rate. The source needs to pay for the amount of power allocated by the relay for transmission of source data to destination. Threshold‐based relaying is considered, where the relay can correctly decode the message, only if the received signal satisfies the predetermined threshold. Maximal ratio combining scheme is employed at destination and eavesdropper to maximise the probability of secure transmission and successful eavesdropping, respectively. Unlike other works to date, the authors have maximised the utility of relay and source, with allocated maximum power constraints at the relay node, using Stackelberg security game scheme. The closed‐form optimal solution for price and power control is obtained, for this leader–follower security equilibrium game model, with the help of convex optimisation.
Fast full‐wave calculation of electromagnetic fields based on weak‐form volume integral equation for MRI applications
Authors: Huang Shao Ying , Ma Zu‐Hui , Wan Luo , Yu Wenwei , Vaughan J. Thomas
Published: July 2018

High‐field magnetic resonance imaging (MRI) scans have safety problems because energy is not homogeneously distributed in the human body. A prescan where energy and temperature distributions are calculated for input energy budgeting can significantly lower the risk. Therefore, fast and accurate calculations of the electromagnetic (EM) fields of an MRI system with a subject under scan are needed. Here, the authors present a fast EM solver based on a weak‐form volume integral equation (VIE) for solving this problem. The proposed approach calculates the EM field inside the human body at a high speed without sacrificing accuracy. In the proposed approach, the VIE formulation for an inhomogeneous dielectric object is employed for near‐field calculations. The operation on a dense matrix resulted by the VIE is accelerated by fast Fourier transform (FFT) in conjunction with the latest efficient iterative method. Numerical experiments are presented to show the speed and accuracy of the proposed EM solver.
Field experience with sympathetic tripping in distribution networks: problems and solutions
Authors: Sabra Hossam , Ibrahim Doaa Khalil , Gilany Mahmoud
Published: July 2018

Sympathetic tripping is a common challenge that affects the proper operation of the earth fault (EF) relays in distribution networks. It likely occurs when healthy feeders are exposed to an unnecessary trip operation in response to an actual fault occurring on an adjacent feeder. The sympathetic tripping phenomena of overcurrent and EF relays in the distribution networks and their causes are studied in this paper. Real recorded data of affected healthy feeder(s) for different sympathetic trip scenarios reported from an Egyptian distribution network are extensively analysed. A custom logic protection scheme is proposed to detect the sympathetic tripping phenomena using the existing features of IED relays without any additional cost. In addition to the captured real disturbance records, simulated scenarios of sympathetic tripping are modelled using MODELS language in ATP/EMTP program to evaluate the proposed schemes. The achieved results ensure the suitability of the proposed protection program in order to avoid the unnecessary false sympathetic tripping for both incoming and outgoing feeders.
Sensitive ground fault detection in compensated systems (arc suppression coil). What is influencing the sensitivity?
Authors: Kaufmann Gerd , Vaitkevičius Ramūnas
Published: July 2018

High‐impedance Earth fault detection is always a topic for any kind of neutral point treatment in electrical power line systems. For compensated networks, it is the disseminated opinion that fault detection is too difficult. The authors aim to show it is simpler and much more sensitive compared with other neutral point treatments. Especially for the sensitivity of classical fault detection methods such as wattmetric (cos ϕ), admittance method and transient method, the question is what sensitivity to expect. This study gives a basic overview of the mentioned detection methods, their achievable sensitivity and the requirements for that. Since the fault detection should work with natural signals only, methods with artificial signal injection during the fault are not included. The necessary measurement accuracy for different detection methods will be considered as well. Basic aspects with practical measurements taken during Earth fault tests in a compensated system with overhead lines are compared. The fault impedance was >5 kΩ in the 10 kV system. The earth fault tests have been undertaken with Energijos Skirstymo Operatorius. The device Erdschluss Ortungs Relais‐3D (EOR‐3D) has been tested regarding the fault detection sensitivity. They will show that classical methods can achieve high fault detection sensitivity.
Adaptive multiple‐master strategy for power management of distributed generators in an islanded distribution subsystem
Authors: Zheng Wei , Crossley Peter , Xu Bingyin , Hu Yushi
Published: July 2018

Power management related to the application of power system islanding is investigated. In an islanded power system, without the utility grid to regulate the island voltage and frequency, distributed generations (DGs) must switch their control tactics to maintain these parameters within the permissible ranges. Generation–load balance is a vital criterion that needs to be ensured, which requires the island DGs to properly share the load demand. Conventional DG coordination strategies cannot deliver high power quality and utilise full island generation capacity at the same time. To address this issue, an adaptive multiple‐master strategy is proposed. This strategy requires neither communication infrastructure nor extra control system, and thus it is immediately applicable to the current network. In addition, this strategy can improve the system transient performance and maximise the economic and environmental benefits. Through simulations conducted on an islanded system consisting of both synchronous and inverter‐based DGs, the effectiveness of the proposed strategy is validated. This strategy also performs well for the islanding events initiated by permanent grid faults.
Protection assessment in electrical distribution grids based on state estimation
Authors: Offergeld Thomas , Cramer Moritz , Glinka Felix , Schnettler Armin
Published: July 2018

The increasing number of inverter interfaced distributed generation units in electrical distribution grids can influence the functionality of protective devices in case of grid faults. The result can be an inadmissible delay in tripping time or failure to trip altogether. This study describes a novel approach to identify and amend potentially unreliable protection configurations. Reliance on conservative worst‐case approximations of the grid state is avoided by using distribution system state estimation instead. Thereby, protection configurations can be more accurately matched to the specific grids' requirements. The overall computational effort is reduced using methods of regression analysis while maintaining original accuracy.
Impact of measurement and communication aspects on protection of multi‐terminal DC grids
Authors: Jahn Ilka , Hohn Fabian , Norrga Staffan
Published: July 2018

The increased demand for renewable energy generation requires the higher flexibility of transmission systems. This requirement together with technical progress in high‐voltage DC technology has resulted in the ambition to build large‐scale multi‐terminal DC grids. To achieve this goal, vendor interoperability is considered a key element. Standards exist for AC systems, but not for DC systems. This work discusses and evaluates the suitability of AC standards for DC systems. As a result, a different view on substation architecture is developed and two communication protocols are suggested for further investigation in this context.
Virtual site acceptance test platform for IEC 61850 based substations with multi‐vendor bay solutions
Authors: Chen Linwei , Charton Thomas , Li Haiyu , Zhang Ray
Published: July 2018

IEC 61850 conformance alone does not necessarily guarantee interoperability of devices from different manufacturers. Achieving full interoperability in a substation protection and control system involving different vendors will increase the confidence of power utilities to deploy digital bays or substations on site. This study presents the development of a virtual site test platform to assess the engineering process and interoperability performance for a fully digital substation with multi‐vendor bay solutions. A data monitoring tool has been developed to visualise data flows in IEC 61850 networks, which can help commissioning engineers to intuitively validate signals like they do for conventional schemes. Case studies are presented to investigate the interoperability of sampled values, generic object oriented substation events and manufacturing message specification communication services. The learning from the system integration and testing will help utilities identify potential issues in engineering phases and hence reduce the risks associated with future site tests.
First digital substation in TransGrid – Australia: a journey, business case, lessons
Authors: Hinkley Kevin , Mistry Chirag
Published: July 2018

IEC61850 has now been accepted ‘almost unequivocally’ as a preferred standard for substation communications.The extent of utilisation of this standard in a majority of installations around the world is at the ‘station bus’ level. It is foreseen that numerous benefits can be availed if the process values are digitised as close to the source as possible and utilised in a comprehensive automation system. TransGrid carried out an extensive assessment of the substation secondary system design based on the implementation of IEC61850 at the station and process bus level which brought out the business case for full digitisation. The first substation to realise this technology is the Avon 330 kV switching station. At Avon, merging units are installed in outdoor cubicles; digitised signals are then transferred to the substation systems. There has been a special focus on standardisation and re‐usable engineering – these are some of the crucial factors to achieve cost reduction. The study describes some of the design principles, estimated cost savings and lessons learnt. The authors envisage that the digital substation technology implemented can bring about substantial cost reduction in green‐field as well as brown field builds and paves the way for the efficient integration of asset monitoring systems.
Testing of Intelligent Electronic Device (IED) in a digital substation
Authors: Stensrud Linda , Ohrn Bendik , Loken Rannveig.S.J. , Hurzuk Nargis , Apostolov Alex
Published: July 2018

This study reports on experience gained during factory testing on a pilot project digital substation. Testing IEDs in a digital substation is dependent on how test and simulation functionality as defined by the IEC61850 is implemented by the vendors, and also requires a different approach to testing compared to testing on a conventional station. This study highlights limitations imposed on testing due to missing IED test facilities, as well as the need for the end customer to fully specify IED functionality to ensure vendor interoperability.
Utilisation of symmetrical components in a communication‐based protection for loop MV feeders with variable short‐circuit power
Authors: Ciontea Catalin Iosif , Leth Bak Claus , Blaabjerg Frede , Hong Qiteng , Booth Campbell , Madsen Kjeld Kilsgaard
Published: July 2018

Variability of the available short‐circuit power also implies variation of the fault level, which can potentially cause several protection problems in the electric networks. In this study, a novel protection method that is insensitive to the fault level changes caused by variable short‐circuit power is presented. It relies on utilisation of symmetrical components of the short‐circuit currents and on communication between the protection relays. The proposed method addresses the single phase to ground (SPG) faults occurring in directly grounded distribution networks, with focus on closed‐loop medium voltage (MV) feeders. Case studies are presented, which demonstrate that the proposed protection scheme is capable of effectively detecting the SPG faults in closed‐loop feeders with variable short‐circuit power.
Synchronous rotor thermal model based on stator current modulation
Authors: El Halabi Nabil , Donolo Marcos , Donolo Pablo , Rajab Thaiban
Published: July 2018

Starting synchronous motors connected to high‐inertia loads often leads to starting times greater than the synchronous motor locked rotor time. This compromises thermal algorithm capabilities to provide adequate rotor thermal protection under stall and slow acceleration conditions. This study presents a novel slip‐dependent thermal model which obtains a slip estimated using stator current modulation caused by rotor saliencies. The proposed algorithm is validated using an OpenModelica model and its performance is compared against the conventional slip‐independent thermal model. Finally, the algorithm is implemented in a protective relay and field tested on a 28820HP motor driving a high‐inertia gas injection compressor at a natural gas liquids facility.
Advanced RTDS‐based studies of the impact of STATCOM on feeder distance protection
Authors: Guan Rui , Xue Ying , Zhang Xiao‐Ping
Published: July 2018

The studies of the performance of feeder distance protection with multiple installations of the static synchronous compensator (STATCOM) are presented. Detailed representation of delta‐connected multi‐level modular converter (MMC) STATCOM is modelled and its impact on feeder distance protection is analytically studied. A real‐time digital simulation (RTDS) based hardware‐in‐the‐loop testing platform is established using practical distance relays, multiple detailed MMC STATCOM models and realistic transmission data. Different types of internal/external faults at varying locations are simulated to investigate the STATCOM's impact on feeder distance protection.
Using fault current limiting mode of a hybrid DC breaker
Authors: Wang Mian , Leterme Willem , Beerten Jef , Van Hertem Dirk
Published: July 2018

Fast DC breakers are essential components to realise future high‐voltage DC grids. Recent development in the industry shows great feasibility in achieving such DC breakers using various technologies. In particular, hybrid DC breakers with modular design have the potential to operate in fault current limiting (FCL) mode, which can provide added functionalities in DC grid protection. However, the degrees of freedom in breaker design and control, and their impact on the transients associated with the FCL operation has not yet been addressed in the literature. Understanding the characteristics of the FCL operation is crucial to achieve interoperability between various technologies in a multivendor environment. This study investigates the impact of design and control parameters on the transients during the FCL operation. Possible applications of the FCL operation in DC grid protection are discussed and demonstrated in a four‐terminal test system.
Assessment methodology and performance indicators for HVDC grid protection strategies
Authors: de Freitas Guilherme Dantas , Ismail Boussaad , Bertinato Alberto , Raison Bertrand , Niel Eric , Poullain Serge , Luscan Bruno
Published: July 2018

This study presents an assessment methodology of protection strategies for meshed grids. It also proposes the computation of two performance indicators to evaluate protection strategies through a reliability and speed perspective. The Monte Carlo method is used to calculate the two indicators proposed. These two indexes can be used as criteria for comparison between protection strategies. Owing to the increasing debate around the protection for high‐voltage DC (HVDC) grids, three proposals of protection of HVDC grids were chosen as application cases.
Impact of dc bias on operating performance of current transformers
Authors: Zhao Yucong , Crossley Peter A. , David Trevor
Published: July 2018

DC bias can be induced via earth return currents (ERCs) from high voltage direct current (HVDC) systems or geomagnetically induced currents (GICs). However, these currents have different characteristics. This study divides dc bias into ERC and GIC types and separately compares their impacts on current transformers (CTs) performance. This was achieved by simulations using PSCAD/EMTDC. The ERC and GIC were represented by different signatures to describe their characteristics. Transformer differential protection was used as an example to demonstrate how ERC and GIC affect CTs transient performance and protection behaviours. The results show the effects of ERC and GIC on CT performance were similar. Although GIC could introduce more measurement errors than ERC, under a practical level of dc bias current, this difference was negligible. Either ERC or GIC has limited impact on correctly specified CTs during steady state. ERC and GIC can transiently saturate CTs during faults, but CTs can remove the transient saturation inherently. As long as the technical specifications of the CTs were adequate for the application, the impacts of ERC or GIC on CTs and protection behaviour were minor. Consequently, the low‐frequency characteristic of GIC was negligible when considering its impact on CTs and protection behaviour.
Hardware‐in‐the‐loop testing of impedance protection with compensation of fault impedance and DG infeed current
Authors: Pandakov Konstantin , Adrah Charles Mawutor , Liu Zou , Høidalen Hans Kristian , Kure Øivind
Published: July 2018

The standard impedance protection deployed in distribution networks can malfunction due to underreach errors caused by fault impedances and remote infeed currents from embedded generators (becoming more and more widespread). This paper introduces a compensation method aiming at elimination of these issues and enhancement of relay dependability. As an advantageous outcome, compensated measurements can be utilised for accurate fault location. The method is verified on ABB RED 670 relay in the loop with an OPAL‐RT real‐time simulator. As the method is based on multi‐point measurements, the test setup also contains a communication network emulator for modelling network delays and imperfections. The laboratory tests verify applicability of the method with proper appearance of the tripping signals from the relay. The fault location results based on synchronised data show overreaching inaccuracy rising with fault resistance. Though communication network delays and imperfection of the channels lead to underreaching, it has been revealed that not strict requirements for data synchronisation can be applied to specific measurements.
Power line signalling based earth fault location
Authors: Farughian Amir , Poluektov Anton , Pinomaa Antti , Ahola Jero , Kosonen Antti , Kumpulainen Lauri , Kauhaniemi Kimmo
Published: July 2018

Fault location in power networks is important as accurate information about the faulted line section expedites system restoration following a fault occurrence. A number of fault location methods have been proposed. Methods based on injecting a signal into the network and tracking it along the feeder appear to have received limited attention. In this study, fault location methods based on network signalling are examined. Two different types of approaches are presented. The first one is based on injection on a very low‐frequency band, whereas the second one is based on utilising modern modulation technologies on low‐frequency band, under 500 kHz, implemented on software‐defined radios. The simulation results indicate the capability of the proposed methods in determining the location of a single phase‐to‐earth fault in medium‐voltage distribution networks.
Generator protection of a bidirectional generator test‐bench working at off‐nominal frequencies and a wide range of voltages
Authors: Aguilar Carlos , Arenas Daniel , Bianchi Fabio , Tobaldi Alessio
Published: July 2018

As part of a new Gas Turbine R&D project, there is always a need to test it throughout a wide range of speeds and loads. A generator connected to a load bank has been chosen to be the variable load for the turbine. This poses several challenges from a generator protection perspective. The study addresses these challenges.
Analysis of single‐ended protection based on boundary element for transmission lines
Authors: Huang Wei , Song Guobing , Zhang Chenhao , Jiang Kun
Published: July 2018

Whole‐line quick‐action protection utilising single‐end electrical parameters has been studied and verified in alternating current and direct current power systems. This study analyses the origin of fault generated high‐frequency harmonics based on the properties of boundary elements and power source during the fault, creating the possibility for the distribution network to achieve single‐ended protection. Based on the non‐loss transmission line model, the differences of transient harmonic characteristics are explained by the comparison of the stabilisation process of the power system with boundary elements and the one without. It is revealed that the source generated specific high‐frequency harmonics and energy storage elements generated high‐frequency harmonics contribute to single‐ended protection criterion during the fault. As the protection scheme only relying on the source generated specific harmonics is hard to take effect for all segments of the distribution network, the travelling wave generated harmonics ought to be utilised to distinguish between internal and external faults for each segment by adding a proper boundary element in the line.
Assessment and analysis of different process bus redundancy networks performance for IEC61850‐based digital substation
Authors: Xu Luoyun , Li Haiyu , Chen Linwei , Patterson Christopher , Mohapatra Priyanka
Published: July 2018

To achieve a highly reliable data communication network, Future Intelligent Transmission Network Substation (FITNESS) project has considered three different substation data communication redundancy networks. These include two independent parallel star networks, High‐availability Seamless Redundancy (HSR) network, and Parallel Redundancy Protocol (PRP) network. This paper presents the assessment and comparison analysis of the data flow performance for these three networks. A typical 275 kV substation with the consideration of three redundancy networks is modelled and simulated using OPNET a communication network simulation tool. The data flow capability performance with respect of the network time delay for the typical protection and control equipment requirements (e.g. IEDs and MUs) in one bay are simulated and analysed. Results show that two independent parallel star networks have the highest data flow capacity. The capacity of PRP network is reduced by a half, while the capacity of HSR network is reduced to a quarter. The results also reveal that Ethernet Switch can consume a part of network bandwidth as well. The work would help power utilities to determine an optimal number of devices to be installed and to ensure highly reliable data communication network for protection and control functions in an IEC 61850 based digital substation..
Earth fault location in compensated MV network using a handheld measuring device
Authors: Horák Martin , Vinklárek Petr , Kordas Jan , Grossmann Jan
Published: July 2018

Various papers and professional literature describe plenty of methods of locating the exact place of the earth fault in a compensated medium‐voltage (MV) network. However, the usability of these methods is very polemic – from the perspective of achieved accuracy, as well as extreme investment demands. Information on practical experience and results from the actual operation are rarely published at all. Handheld earth fault location finder (device) is an innovative and highly functional alternative to static earth fault locators for overhead MV lines. The device enables a contactless determination of the relative earth fault location in relation to the specific place of measurement. With sequential measurements in right positions, it is possible to get to the fault location very quickly. This study describes the function and possibilities of the handheld device, as well as practical experience with locating both the actual and the experimental earth faults in the MV network.
Advanced simulation of IEDs
Authors: Schossig Thomas
Published: July 2018

IEC 61850 is the established standard for substation communication. Since the standard describes different stages of lifecycle of Substation Automation Systems the demands for specification, testing, and especially simulation differ. The approach described in this study can be used in the different stages and fulfil practical requirements. It describes the requirements for simulation and proposes an implementation applicable. If a single Intelligent Electronic Device (IED) and its data model to be simulated in technical investigation phase is sufficient at Factory Acceptance Testing and Site Acceptance Testing multiple IEDs and utilised services as GOOSE and reports will be needed. In addition, the methods described for indicating test mode/behaviour and simulation indication become important. The simulation has to be embedded in testing environment and interact with tools to be used for visualisation of changes in IED's data model. Advanced services in IEC 61850 like setting groups control, switching device control and file transfer have to be added. The requirements will be discussed from a utility's perspective. The method described can be extended for routine testing and maintenance testing, e.g. after firmware upgrades. An outlook develops a vision to be utilised for automation and control testing.
Type D travelling wave fault location on branched underground low‐voltage networks
Authors: Gale Phillip F. , Wang Anding
Published: July 2018

Low voltage cable faults are frequently associated with arcing at the fault which creates 2 high frequency transients which propagate away from the fault towards opposite ends of the cable and whose difference in arrival times can be used to determine the fault's location using the Type D method. A variant of the Type D method, known as the Transient Recording System (TRS) using asynchronous data acquisition units (ADAU) has been used successfully in situations where multiple branches on a cable have precluded the use of other travelling wave methods. The range, and precision of location, of the TRS method is extended by the use of a Marker Unit (MU) which allows the distance and direction to a fault to be determined relative to the point of connection of the MU. The asynchronous data acquisition units operate in ‘listening’ mode and are triggered by the arrival of the transients created by the fault arc. Prior to triggering, the ADAUs continuously (over)write all received data into their cyclic buffers, including the low amplitude MU pulses. Shortly after triggering the (over)writing of the cyclic buffer stops and earlier (pre‐trigger) data retained – including the received MU pulses.
Distributed current sensing technology for protection and fault location applications in high‐voltage direct current networks
Authors: Tzelepis Dimitrios , Dysko Adam , Booth Campbell , Fusiek Grzegorz , Niewczas Pawel , Peng Tzu Chief
Published: July 2018

This study presents a novel concept for a distributed current optical sensing network, suitable for protection and fault location applications in high‐voltage multi‐terminal direct current (HV‐MTDC) networks. By utilising hybrid fibre Bragg grating‐based voltage and current sensors, a network of current measuring devices can be realised which can be installed on an HV‐MTDC network. Such distributed optical sensing network forms a basis for the proposed ‘single‐ended differential protection’ scheme. The sensing network is also a very powerful tool to implement a travelling‐wave‐based fault locator on hybrid transmission lines, including multiple segments of cables and overhead lines. The proposed approach facilitates a unique technical solution for both fast and discriminative DC protection, and accurate fault location, and thus, could significantly accelerate the practical feasibility of HV‐MTDC grids. Transient simulation‐based studies presented in the paper demonstrate that by adopting such sensing technology, stability, sensitivity, speed of operation and accuracy of the proposed (and potentially others) protection and fault location schemes can be enhanced. Finally, the practical feasibility and performance of the current optical sensing system has been assessed through hardware‐in‐the‐loop testing.
Energy and reactive power differential protection hardware‐in‐the‐loop validation for transformer application
Authors: Dantas Daniel Texidor , Pellini Eduardo Lorenzetti , Manassero Junior Giovanni
Published: July 2018

This article focuses on validating a time‐domain power system protection solution, based on energy and reactive power algorithms, through simulations using hardware‐in‐the‐loop. The results are compared against a commercial, off‐the‐shelf, intelligent electronic device. The developed protection algorithms are briefly described, followed by the description of the hardware platform responsible for its practical execution and the description of the applied tests. The obtained results show significant advantages on response times when compared to traditional protection, and the ability to securely identify delicate internal transformer faults, even during inrush condition.
Effect of Network Protection Requirements on the Design of a Flexible AC/DC‐link
Authors: Burstein Andrew , Cuk Vladimir , de Jong Erik
Published: July 2018

This study explores how protection systems affect the design of a medium‐voltage (MV) flexible AC/DC link (FDCL). To show this impact, two FDCL designs are analysed. The first designed before considering protection and the second created specifically to solve the protection issues realised in the first. One of the main aspects of the FDCL is to be placed into an existing network, reuse existing equipment, and not require any changes outside of the substations of installation. In this way, the converters must be sized in such a way to retain selectivity of the lower network as well as be able to secure a continuous supply of power through the link even in the case of a DC‐side fault. How this is performed and the converter overrating requirements are determined for a 10 kV MV link.
Fault discrimination and protection coordination for a bipolar full‐bridge MMC‐HVDC scheme
Authors: Wenig Simon , Goertz Max , Heinisch Mike , Suriyah Michael , Leibfried Thomas
Published: July 2018

Fault discrimination and protection design for bipolar high‐voltage direct current transmission solutions based on modular multilevel converters (MMC‐HVDC) links are of significant importance for a reliable and resilient power transmission. If full‐bridge submodules are utilised, fault‐dependent handling concepts considering the location of an event are enabled. This study presents a comprehensive approach to differentiate and deal with internal converter and dc side faults. While a multitude of measurements inside and at the clamps of each converter is usually only used for simple threshold‐based hardware‐related protection, additional differential and derivative criteria may further improve selectivity. However, this requires careful configuration to avoid improper reactions. To highlight the coordinated manner of the proposed concept, various faults are analysed and selected examples are explicitly investigated and visualised using the PSCAD EMTDC software.