Academic literature on the topic 'Dynamic transformer rating'
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Journal articles on the topic "Dynamic transformer rating"
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Bracale, Antonio, Guido Carpinelli, and Pasquale De Falco. "Probabilistic risk-based management of distribution transformers by dynamic transformer rating." International Journal of Electrical Power & Energy Systems 113 (December 2019): 229–43. http://dx.doi.org/10.1016/j.ijepes.2019.05.048.
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Daminov, Ildar, Rémy Rigo-Mariani, Raphael Caire, Anton Prokhorov, and Marie-Cécile Alvarez-Hérault. "Demand Response Coupled with Dynamic Thermal Rating for Increased Transformer Reserve and Lifetime." Energies 14, no. 5 (March 3, 2021): 1378. http://dx.doi.org/10.3390/en14051378.
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(1) Background: This paper proposes a strategy coupling Demand Response Program with Dynamic Thermal Rating to ensure a transformer reserve for the load connection. This solution is an alternative to expensive grid reinforcements. (2) Methods: The proposed methodology firstly considers the N-1 mode under strict assumptions on load and ambient temperature and then identifies critical periods of the year when transformer constraints are violated. For each critical period, the integrated management/sizing problem is solved in YALMIP to find the minimal Demand Response needed to ensure a load connection. However, due to the nonlinear thermal model of transformers, the optimization problem becomes intractable at long periods. To overcome this problem, a validated piece-wise linearization is applied here. (3) Results: It is possible to increase reserve margins significantly compared to conventional approaches. These high reserve margins could be achieved for relatively small Demand Response volumes. For instance, a reserve margin of 75% (of transformer nominal rating) can be ensured if only 1% of the annual energy is curtailed. Moreover, the maximal amplitude of Demand Response (in kW) should be activated only 2–3 h during a year. (4) Conclusions: Improvements for combining Demand Response with Dynamic Thermal Rating are suggested. Results could be used to develop consumer connection agreements with variable network access.
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Alvarez, David L., Sergio R. Rivera, and Enrique E. Mombello. "Transformer Thermal Capacity Estimation and Prediction Using Dynamic Rating Monitoring." IEEE Transactions on Power Delivery 34, no. 4 (August 2019): 1695–705. http://dx.doi.org/10.1109/tpwrd.2019.2918243.
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Daminov, Ildar, Anton Prokhorov, Raphael Caire, and Marie-Cécile Alvarez-Herault. "Assessment of dynamic transformer rating, considering current and temperature limitations." International Journal of Electrical Power & Energy Systems 129 (July 2021): 106886. http://dx.doi.org/10.1016/j.ijepes.2021.106886.
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Zarei, Tahereh, Kateryna Morozovska, Tor Laneryd, Patrik Hilber, Malin Wihlén, and Olle Hansson. "Reliability considerations and economic benefits of dynamic transformer rating for wind energy integration." International Journal of Electrical Power & Energy Systems 106 (March 2019): 598–606. http://dx.doi.org/10.1016/j.ijepes.2018.09.038.
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Talpur, Saifal, Tek Tjing Lie, Ramon Zamora, and Bhaba Priyo Das. "Maximum Utilization of Dynamic Rating Operated Distribution Transformer (DRoDT) with Battery Energy Storage System: Analysis on Impact from Battery Electric Vehicles Charging." Energies 13, no. 13 (July 2, 2020): 3411. http://dx.doi.org/10.3390/en13133411.
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This paper investigates thermal overloading, voltage dips and insulation failure across a distribution transformer (DT), under residential and battery electric vehicle (BEV) loadings. The objective of this paper is to discuss the charging impact of BEVs on voltage across consumer-service points, as well as across the life of paper insulation under varying ambient temperatures (during winter and summer), with and without a centralized battery energy storage system (BESS). This study contributes in two ways. The first part of this study deals with coordinated and uncoordinated BEV charging scenarios. The second part of this study deals with maximum utilization of a test DT rated under dynamic thermal rating (DRoDT). The DRoDT integration with BESS is carried out to flatten the load spikes, to obtain maximum DT utilization, to achieve active power and voltage supports in addition to an enhanced DT lifespan. The obtained results indicate that, when test DT operates under the proposed hybrid technique (combining both dynamic transformer ratings and a centralized BESS), it attains maximum utilization, lower hot-spot temperature, enhanced lifespan, less degraded paper insulation and an improved voltage across each consumer service point. The proposed technique is furthermore found effective in maintaining the loading across the distribution transformer within the nominal limits. However, under excess loading during peak hours, the proposed technique provides relief to the DT to a certain extent. To achieve an optimal DT operation and an enhanced BESS lifespan, the BESS is operated under nominal charging and discharging cyclic limits. Under the proposed DRoDT integration with BESS, DT attains 25.9% more life when loaded with coordinated BEV charging, in comparison to no BESS integration under the same loading scenario. The worst loading due to uncoordinated BEV charging also brings 51% increase in DT life when loaded under the proposed technique.
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Eya, Candidus U., Ayodeji Olalekan Salau, and Stephen Ejiofor Oti. "Uninterruptible DC-powered boost differential inverter with a Sensorless Changeover System." WSEAS TRANSACTIONS ON CIRCUITS AND SYSTEMS 20 (March 19, 2021): 10–26. http://dx.doi.org/10.37394/23201.2021.20.2.
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This paper presents the design and implementation of an Uninterruptible DC-powered boost differential inverter with a sensor-less Changeover system. The systems design was developed using solar panels, bidirectional converter current linked battery banks, and a single-staged DC/AC Converter. The system was designed, modeled, and simulated using MATLAB/Simulink software before its implementation. The properties exhibited by the system include: Single stage input voltage transformation and amplification without a power transformer, lightweight sensor-less and relay-less automatic changeover, and a simplified feedback system. The simulation results show that the system gives a pure sine voltage and current waveforms, total harmonic distortion (THD) of 1.25%, efficiency of 94.4%, relatively fast dynamic response and 1 kilowatt power rating. The specific target areas of applications are: in medical paraphernalia where pure sine waveforms are needed, homes, and medium scale industries.
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Erdinç, F. Gülşen, Ozan Erdinç, Recep Yumurtacı, and João P. S. Catalão. "A Comprehensive Overview of Dynamic Line Rating Combined with Other Flexibility Options from an Operational Point of View." Energies 13, no. 24 (December 12, 2020): 6563. http://dx.doi.org/10.3390/en13246563.
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The need for flexibility in power system operation gradually increases regarding more renewable energy integration, load growth, etc., and the system operators already invest in this manner to enhance the power system operation. Besides, the power system has thermally sensitive assets such as lines, transformers, etc. that are normally operated under highly conservative static ratings. There is a growing trend in this regard to use the actual capacity of such assets dynamically under varying operating conditions leading to a dynamic thermal rating concept which is referred as dynamic line rating (DLR) approach specifically for lines. This study provides a comprehensive overview of existing perspectives on DLR and combination with other flexibility options from an operational point of view. Apart from the existing review studies more focused on implementation category of DLR concept, the concentration on more operational stage from the power system operation point of view leads the difference of this study compared to the mentioned studies. A categorization of the DLR implementation for either being sole or combined usage as a flexibility option is further realized. Besides, a geographically categorized analysis on existing practical evidence on DLR concept and implementations is also presented in this study.
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Viafora, Nicola, Kateryna Morozovska, Syed Hamza Hasan Kazmi, Tor Laneryd, Patrik Hilber, and Joachim Holbøll. "Day-ahead dispatch optimization with dynamic thermal rating of transformers and overhead lines." Electric Power Systems Research 171 (June 2019): 194–208. http://dx.doi.org/10.1016/j.epsr.2019.02.026.
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Ariza Rocha, Oscar David, Kateryna Morozovska, Tor Laneryd, Ola Ivarsson, Claes Ahlrot, and Patrik Hilber. "Dynamic rating assists cost-effective expansion of wind farms by utilizing the hidden capacity of transformers." International Journal of Electrical Power & Energy Systems 123 (December 2020): 106188. http://dx.doi.org/10.1016/j.ijepes.2020.106188.
Full textDissertations / Theses on the topic "Dynamic transformer rating"
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Molina, Gómez Andrea. "Improved planning of wind farms using dynamic transformer rating." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287175.
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Due to the increase in electrical demand and renewable penetration, electrical utilities need to improve and optimize the grid infrastructure. Fundamental components in this grid infrastructure are transformers, which are designed conservatively on the base of a static rated power. However, load and weather change continuously and hence, transformers are not used in the most efficient way. For this reason a new technology has been developed: Dynamic transformer rating (DTR). By applying DTR, it is possible to load transformers above the nameplate rating without affecting their life time expectancy. This project goes one step further and uses DTR for the short term and long term wind farm planning. The optimal wind farm is designed by applying DTR to the power transformer of the farm. The optimization is carried out using a Mixed-Integer Linear Programming (MILP) model. In respect of the transformer thermal analysis, the linearized top oil model of IEEE Clause 7 is selected. The model is executed for 4 different types of power transformers: 63 MVA, 100 MVA, 200 MVA and 400 MVA. As result, it is obtained that the net present value for the investment and the capacity of the wind farm increase linearly with respect to the size of the transformer. Then, a sensitivity analysis is carried out by modifying the wind speed, the electricity price, the lifetime of the transformer and the selected weather data. From this sensitivity analysis, it is possible to conclude that wind resources and electricity price are key parameters for the feasibility of the wind farm.På grund av ökningen av efterfrågan av elektricitet och förnybara energin, elförsörgingsföretag måste förbättras och elnätets infrastruktur måste optimeras. Grundläggande komponenter i elnätet är transformatorer, som är designade konservativt efter en statisk märkeffekt. Laster och vädret ändras dock kontinuerligt, detta betyder att transformatorer inte används på de mest effektiva sätten. Av denna anledning har en ny teknik utvecklats: Dynamisk lastbarhet hos transformatorer (DTR). Genom att applicera DTR, gör det möjligt att belasta en transformator högre än märkdata utan att påverka den förväntade livslängden. Detta projekt går ett steg längre och använder DTR för kort och lång sikts vindkraftparkplaneringar. Den optimala vindkraftparken är designad genom att använda DLT på krafttransformatorn för vindkraftsparken. Optimeringen utförst med hjälp av Mixed-Integer Linear programming (MILP) modell. Gällande transformatorns termiska analys, så valdes den linjäriserade toppoljemodellen av IEEE Clause 7. Modellen var utförd för fyra olika krafttransformatorer: 63 MVA, 100 MVA, 200 MVA och 400 MVA. Resultatet blev att nettonuvärdet för investeringen och kapaciteten av vindkraftsparken ökade linjärt med avseende på storleken på transformatorn. En känslighetsanalys var utförd genom att ändra vindhastigheten, elpriset, livstiden av transformatorn och de valda väderdata. Från känslighetsanalysen så var det möjligt att dra slutsatsen att vindresurser och elpriset är nyckelparametrar för vindkraftsparkens genomförbarhet.
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Karlsson, Rikard. "Power system performance when implementing dynamic rating on a wind farm connected transformer." Thesis, KTH, Elektroteknisk teori och konstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215949.
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In this study, dynamic transformer rating (DTR) is applied on a medium power transformer thatis in use in the regional transmission grid. The transformer’s rated apparent power is 63 MVA, itis connected between a wind farm at 22kV and the grid, K¨orsb¨arsdalen, at 135kV. Power systemanalysis are carried out on the grid, with the objective to test how DTR and increased wind poweraffects the grid performance with respect to reliability, voltage stability and active losses.Historical measurements of ambient temperature and transformer loading is used to calculatefree transformer capacity based on unity life time loss. For the investigated transformer and giventime period the load can be increased without endanger transformer lifetime. The dynamicallyrated capacity exceeds the nominal capacity through the whole tested time period but DTR showsmost effective during winter when the ambient temperature is colder and therefore, has a coolingeffect on the transformer. DTR is used to calculate available transformer capacity but an increasedcapacity often comes with the expense of decreased lifetime and reliability. With the help of DTRthe current rate of transformer lifetime usage can be calculated and used as input to economicalanalysis where there is a trade of between reliability and profit from increased capacity.Through the power system analysis procedure presented in this report it is possible to sortout the faults that are most probable to cause severe violations, this information can be used forefficient reinforcement of the grid. The contingency and reliability analysis can work as base tofind the solutions that will decrease the probability for violations most efficiently. Furthermore,the developed procedure can also be used when expanding the grid and to determine which gridalternative that will be most reliable.I den h¨ar studien kommer en dynamisk modell f¨or en transformators maxkapacitet anv¨andas isyfte att utv¨ardera m¨ojligheterna f¨or utbyggnad av vindkraftsparken som ¨ar kopplad till transformatornsl°agsp¨anningssida. P°a transformatorns h¨ogsp¨anningssida finns regionn¨atet, K¨orsb¨arsdalen.Med hj¨alp av den dynamiska modellen ber¨aknas transformatorns varmaste punk. Dem varmastepunkten ¨ar bel¨agen p°a ¨ovre delen av transformatorns lindning. Det ¨ar denna punkts temperatursom s¨atter gr¨ansen f¨or hur mycket str¨om som kan s¨andas genom transformatorn utan att resultera io¨verhettning. O¨ verstiger den varmaste punkten en kritisk temperatur finns risk fo¨r att transformatornlivsl¨angd f¨orkortas. Konceptet dynamisk lastbarhet som bygger p°a termiska modeller kallasp°a engelska ,dynamic transformer rating (DTR).Vidare utv¨arderas effekterna av DTR p°a systemniv°a, K¨orsb¨arsdalens prestanda d°a DTR harimplementeras j¨amf¨ors med det ursprungliga n¨atets prestanda med avseende p°a tillf¨orlitlighet,sp¨anningsstabilitet och aktiva f¨orluster.Historiska m¨atv¨arden p°a omgivningstemperatur och transformatorns last anv¨ands f¨or att ber¨aknatransformatorns tillg¨angliga kapacitet, f¨or det studerade tidsspannet kan transformatorn anv¨andas¨over dess nominella effekt. P°a vintern d°a omgivningstemperaturen ¨ar l°ag kommer DTR till st¨orstnytta, den kalla luften har en kylande effekt p°a transformatorn vilket i sin tur betyder att en st¨orrestr¨om kan s¨andas genom transformatorns lindningar utan att en kritisk temperatur uppn°as.Genom det presenterade tillv¨agag°angss¨attet f¨or systemkraft analyser kan de fel som har st¨orstsannolikhet att resultera i allvarliga konsekvenser sorteras ut. Denna information kan anv¨andassom underlag f¨or reinvesteringar s°av¨al som vid expandering av det befintliga n¨atet.
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Ariza, Rocha Oscar David. "Dynamic transformers rating for expansion of expansion of existing wind farms." Thesis, KTH, Elektroteknisk teori och konstruktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-256531.
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Distribution system operators face the challenge to connect users rapidly to the grid and the opportunity to reduce costs for new connections. A method to enhance network operation and planning is dynamic transformer rating (DTR), which considers load and temperature variations to increase the rating of the transformer while maintaining in safe operation. This project investigates DTR application to an existing population of transformers connected to a wind park and proposes a method for adding new turbines to the grid using installed transformers. Five transformer locations and nine units belonging to E.ON AB are used to find the potential of DTR for network expansion. A weather analysis reveals that simultaneous high wind speeds and high temperatures seldom occur. An aging estimation based on the IEC 60076-7 standard shows that the transformers for wind power applications are underused. Considering the transformer thermal model, a sensitivity analysis shows that the parameters that mostly affect the aging rate are the moisture content, the hot spot factor, and the top-oil temperature rise. The maximum load to assure aging below 50 years is calculated for each transformer for different maximum hot-spot temperature levels showing that increasing the maximum allowed temperature reduces curtailment and increases aging. A single node analysis depicts the optimal expansion of wind power from a generator perspective, and a network analysis introduces further restrictions to the network. As a result, the optimal increase factor is around 30 to 50 % and is larger for higher hot-spot temperature limits. Accurate weather measurements and transformer parameters are necessary to make a proper estimation of transformer aging to unlock transformer potential. To use fiber optic temperature sensors in new transformers and on-site temperature measurements can increase the rating of the transformer. A maximum allowed temperature of 110◦C is conservative and limits the potential of the transformer for wind power applications. Finally, society benefits from DTR in wind power applications because there is a more efficient use of resources and additional renewable energy can be introduced to the network.Eldistributionsnätet står inför en utmaning att snabbt ansluta användare till nätet och en möjlighet att miska kostnaderna i nya ansultnigar. En metod för att förbättra nätverksdrift och planering är dynamisk lastbarhet hos transformatorer, eller dynamic transformer rating (DTR). Metoden beaktar belastings- och temperaturvariationer för att öka transformatorns lastbarhet samtidigt som den upprätthåller säker drift. Detta projekt undersöker tillämpningen av dynamisk lastbarhet till en befintling population av transformatorer kopplade till en vindkraftpark och föreslår en metod för att ansluta ytterligare turbiner till nätet med hjälp av befintliga transformatorer. Fem transformatorplatser och nio enheter som tillhör E.ON AB används för att undersöka potentialen för DTR inom tillämpningar för nätverksexpansion. En vänderanalysis avslöhar att både höga vindhastigheter och temperaturer sällan uppstår samtidigt. En uppskattning av åldrandet baserad på IEC 60076-7-standarden visar att transformatorer för vindkraftstillämpningar är underanvända. Med avseende på den termisk transformatormodellen visar en känslighetsanalys att parametrarna som påverkar minskning av livslängden mest är fuktinnehållet, hot spot-faktorn och ökning av top-olja-temperaturen. Den maximala belastningen för att säkerställa en åldring under 50 år beräknas för varje transformator, för olika värden på den maximala hotspottemperaturen. Detta visar att med ökning av den maximala tillåtna temperaturen minskar produktionsbortfall och ökar åldrandet. En-nods-analys visar den optimala expansionen av vindkraft från en producents perspektiv, och en nätverksanalys introducerar ytterligare begränsningar för nätverket. Detta resulterar i en optimal ökningsfaktor på cirka 30-50% och är större för högre värden på den maximala hotspottemperaturen. Noggranna vädermätningar och transformatorparametrar är nödvändiga för att göra en korrekt uppskattning av transformatorns åldrande. Att använda fiberoptiska temperatursensorer i nya transformatorer och platsspecifika temperaturmätningar kan öka transformatorns lastbarhet. En maximal tillåten temperatur på 110 ◦C är för konservativ och begränsar transformatorns potential för vindkraftstillämpningar. Samhället drar fördel av DTR i vindkraftstillämpningar eftersom det leder till en effektivare resursanvändning och att ytterligare förnybar energi kan introduceras i nätverket.
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Morozovska, Kateryna. "Dynamic Rating of Power Lines and Transformers for Wind Energy Integration." Licentiate thesis, KTH, Elektroteknisk teori och konstruktion, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226564.
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Dynamic Rating (DR) is usually associated with unlocking the capacity of power lines and transformers using available information on weather conditions. Our studies show that Dynamic Rating is a broad concept that requires further study and development. The capacity of the majority of power devices is highly dependent on the heat transfer properties of the materials which the devices are made of. To ensure correct power limits of the equipment, one must take into consideration not only the power load, but also ambient conditions, such as: temperature, wind speed, wind direction, solar irradiation, humidity, pressure, radiation into the atmosphere and magnetic losses. Dynamic rating is created as an alternative to standard constant rating that is designed with reference to extreme weather and load conditions. Some areas are more likely than others to experience extreme weather conditions, which have a chance of occurring only a few days per year for short periods of time. Such a distribution of weather parameters gives an opportunity to embed existing material properties of the power equipment and achieve a better utilization of the grid. The following thesis is divided into two simultaneous topics: Dynamic line rating and Dynamic transformer rating. The division is motivated by the importance of analysing the operation of the above-mentioned parts of the power network in greater detail. Power lines and transformers play a significant part in grid planning and have a potential to result in economic benefits when used with DR. The main focus of the doctoral project "Dynamic rating of power lines and transformers for wind energy integration" is on exploring potential ways to connect power generated from wind to the grid with the help of dynamic rating technologies. Therefore, great focus of the work lies on the analysis of DR connection of variable energy sources such as wind farms. The thesis presents the comparison of different line rating methods and proposes a new way of their classification. Evaluation of dynamic line rating application has shown the possibility to expand the power grid with additional capacity from wind power generation. Literature analysis and detailed evaluation of the conductor heat balance models have led to experimental evaluation of the convective cooling effect. The dynamic transformer rating application has shown a possibility to decrease the size of the power transformer without shortcoming in component availability.QC 20180423
Dynamic Rating for Wind Power
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Stefanou, Christos. "Investigation of the effect of moisture in transformers on the aging of the solid insulation for dynamic rating applications." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235267.
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In the present thesis an investigation is performed for the effect of moisture contenton the aging of the solid insulation for transformers that are dynamically loaded. Theinvestigation is based on a theoretical analysis and a model.First, a literature review is conducted on the basics of transformer operation, transformerinsulation and moisture in oil-paper systems. Furthermore, a model is developedbased on moisture equilibrium curves created by Oommen and MIT, moisture diffusionprocesses in oil-paper insulation systems and calculations for the aging of cellulose insulationfrom IEC 60076-7. The model represents an experimental system which is loadedon different load patterns that simulate dynamic loading. The aim of the model is toconclude whether the load patterns will cause the paper to age differently dependingon the frequency that the moisture migration phenomenon between paper and oil occurs.The result of the modeling part is that the aging process is affected by the load pattern,and that the higher the frequency the moisture migration phenomenon occurs within aloading cycle, the larger the impact on insulation degradation. This difference, though,is too small to be measured experimentally in terms of DP and it is suggested thatdifferent load patterns are used in the experiment than those used in the model, whichwill amplify the effect of moisture migration even further.Finally, experimental work is conducted in the thesis, which focuses on implementingthe LabVIEW design from previous work into hardware, debugging the system andpreparing the experimental set-up on practical matters that occurred in the lab. Somefinal work is required before the experiment is able to run, such as preparation of theexperimental units.I detta examensarbete undersöks effekten av fuktinnehåll på åldring av fast isolationsmateriali transformatorer med dynamisk last. Arbetet är baserat på en teoretisk analysoch en modell.Först genomförs en litteraturstudie på grundläggande transformatorfunktion, transformatorisolationoch fukt i oljeimpregnerade papperssystem. Vidare utvecklas en modellbaserad på jämviktskurvor for fukt skapade av Oommen och MIT, fuktdifussionsprocesseri isolationssystem baserade på oljeimpregnerat papper och beräkning av åldringav cellulosaisolation från IEC 60076-7. Modellen representerar ett experimentellt systemsom lastas för att simulera dynamisk last. Målet med modellen är att avgörahuruvida lastprofilen påverkar åldrandet av pappret beroende på frekvensen av fuktmigrationenmellan papper och olja.Resultatet av modelleringen är att åldrandet påverkas av lastprofilen och desto oftarefuktmigrationen sker inom en lastcykel, desto större är effekten på isolationsdegraderingen.Skillnaden är dock för liten att mäta experimentellt med avseende på DP och andralastprofiler föreslås i framtida experiment, för att förstärka effekten av fuktmigration.Slutligen utförs experimentellt arbete som fokuserar på implementation av LabVIEWdesignenfrån tidigare arbete i hårdvara, felsökning av systemet samt förberedelse av denexperimentella installationen för praktiska bekymmer som uppstått i laboratoriemiljön.En liten mängd arbete återstår före experimentet kan utföras, såsom förberedelse av deexperimentella enheterna.
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Hu, Xiaolong. "Impact of climate change on power systems." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/impact-of-climate-change-on-power-systems(2132a62f-afa2-4d91-8381-5ec8643b97b4).html.
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The global mean surface temperature rise was observed in the past century and proved the warming of the earth climate system. Global warming is believed to continue into the next decades due to unprecedented increases in greenhouse gas emissions. As a consequence of global warming, extreme weather scenarios are also expected to occur more frequently. In such a context, it is of vital importance to assess the impacts of climate change on the operational performance of power systems. This thesis investigates the impacts of climate change on the operational performance of power systems. The future climate is simulated based on emission scenarios and is then used as an input to the thermal models of power system components to assess their ratings and ageing, and further the reliability of the system. This research contributes to a number of areas in power system research. In the literature review, the risks that climate change may cause to power systems are identified. The models used for the simulation of future climate are firstly introduced. The weather variables that can be simulated from the models include air temperature, solar radiation, wind speed and direction, soil moisture and soil temperature. Among the models, the one for soil temperature is originally developed in this thesis. Following this, the component thermal models of overhead line, cable and transformer, from different standards are compared and selected. After that, the sensitivity of component ratings to individual weather variables is investigated, as a preliminary study for the later research in this thesis. Then, the impacts of climate change on component ratings (including both static and dynamic rating) are comprehensively and probabilistically assessed. The assessment results indicate the reduction of component ratings due to climate change. The impacts of climate change on system reliability is further examined on the IEEE Reliability Test System. Results demonstrate and quantify the reduction of both component ratings and system reliability, and prove that the dynamic rating can be used to mitigate the reduction. Finally, the preliminary exploration of transformer ageing is carried out and shows an increased ageing rate due to air temperature rises.
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Gustafsson, Patrik. "Design of Experimental Setup for Investigation of Effect of Moisture Content on Transformer Paper Ageing during Intermittent Load." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232187.
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In this project an experimental setup is designed to investigate the effect of intermittent load patterns in combination with moisture content on cellulose ageing. It is done by exposing groups of samples to different intermittent load patterns with varying frequency. A literature review is done on transformer insulation system and cellulose degradation. Various technical solutions to different aspects of the experimental design are reviewed. The final experimental setup is explained with the primary focus being on the hardware and programming of the controlling system. The controlling system consists of a Data Acquisition (DAQ) system from National Instruments and is programmed in LabVIEW. The controlling system is examined in two investigative tests where it performed satisfactorily. Three load patterns are developed. This project suggests how to prepare the samples and what direct- and indirect tests to apply to the insulation system for future analysis.Over the years, a considerable amount of scientific work has been devoted to understanding paper ageing in order to improve transformer diagnostics and investments for utility owners. However, transformer loading guidelines of today do not take intermittent load in combination with moisture content into account [1] [2]. Previous work suggests that the thermal models may be improved by looking into the effects of moisture content [3].The primary aim of the proposed experimental setup is to investigate whether an intermittent load pattern in combination with moisture content have a considerable detrimental effect on cellulose ageing. The intent is to contribute with new knowledge about transformer diagnostics and long-term possibly improve the current thermal models used for Dynamic Transformer Rating (DTR) which do not take this phenomenon into account. This would in particular benefit transformers with typically intermittent load patterns, e.g. a transformer connected to a wind farm or photovoltaic panels. Increasing renewable energy installations increase the need for developing the thermal models in the transformer loading guidelines to take unconventional load profiles into account.I det här projektet utformas ett experiment för att undersöka inverkan av intermittenta lastmönster i kombination med fukthalt på åldrande av cellulosa. Detta görs genom att utsätta provgrupper för olika lastmönster med varierande frekvens. En litteraturgenomgång görs på transformatorisoleringssystem och nedbrytning av cellulosa. Olika tekniska lösningar för olika aspekter av experimentets design ses över. Den slutliga utformningen av experimentet förklaras med fokus på hårdvara och programmering av kontrollsystemet. Kontrollsystemet består av ett system för datainsamling från National Instruments och programmeras i LabVIEW. Kontrollsystemet utvärderas i två undersökande test där det förfor på ett tillfredsställande sätt. Tre lastmönster till experimentet har tagits fram. Det här projektet föreslår hur man förbereder proverna och vilka direkta och indirekta test som kan göras för framtida analyser.Under åren har en betydande mängd vetenskapligt arbete ägnats åt att förstå pappersåldring för att förbättra transformatordiagnostik och investeringsunderlaget för nätägare. De industriella standarderna tar dock inte hänsyn till intermittent belastning i kombination med fukthalt [1] [2]. Tidigare arbete föreslår att de termiska modellerna möjligen kan förbättras genom att undersöka effekterna av fukthalt [3].Det huvudsakliga målet med den föreslagna experimentella uppställningen är att undersöka huruvida ett intermittent belastningsmönster i kombination med fukthalt har en betydande inverkan på pappersåldrandet. Föresatsen är att bidra med ny kunskap om transformatordiagnostik och för att om möjligt långsiktigt förbättra de nuvarande termiska modellerna som används till dynamiska lastbarhetsmodeller för transformatorer. Detta skulle särskilt gynna transformatorer med typiskt intermittenta belastningsmönster, t ex en transformator ansluten till en vindkraftpark eller solcellspaneler. Ökande antal av anläggningar för förnybar energi ökar behovet av att utveckla de termiska modellerna för att ta hänsyn till okonventionella lastprofiler.
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Cong, Yuhang. "Synchronized measurement technology supported operational tripping schemes." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/synchronized-measurement-technology-supported-operational-tripping-schemes(7d472659-d352-4291-96fc-fce7e6ce5fc8).html.
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The increasing volume of renewable and intermittent generation that is being connected to power systems means that system operators need more advanced dynamic control tools to manage the increase in congestion and the resulting pressure on system constraints. The introduction of synchronised measurement technology provides the wide area real-time measurements that are essential to develop and implement adaptive online solutions for current network issues. The objective of the research presented in this thesis is to design intelligent system integrity protection schemes (SIPS) that protect transmission lines and power transformers from thermal overloading. An intelligent protection scheme should be able to identify the fault severity, predict the post disturbance trend of system states, continue monitoring specific vulnerable system variables and propose an accurate solution that is tailored to the actual system conditions and the specific contingencies that have occurred. The intent of this research is to contribute to the development of adaptive protective schemes that are enabled by modern synchronized measurement technologies for future power systems. The research presented in this thesis focuses on the creation of novel Operational Tripping Schemes (OTSs) that explicitly satisfy both the functionality and economical requirements by integrating an improved assessment of thermal behaviour of the monitored assets. Novel OTSs are proposed for both transmission lines and transformers and they can be considered to be intelligent, adaptive and efficient SIPS for the thermal protection of system assets. A novel functional block is proposed that be included within the OTS and that uses optimization theory to determine the lowest cost solution to overheating in the time available. Furthermore, case studies have been conducted to verify the performance of each novel OTS using simulations of a full GB system model.
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Gavrilovic, Nenad. "VIBRATION-BASED HEALTH MONITORING OF ROTATING SYSTEMS WITH GYROSCOPIC EFFECT." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1358.
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This thesis focuses on the simulation of the gyroscopic effect using the software MSC Adams. A simple shaft-disk system was created and parameter of the sys-tem were changed in order to study the influence of the gyroscopic effect. It was shown that an increasing bearing stiffness reduces the precession motion. Fur-thermore, it was shown that the gyroscopic effect vanishes if the disk of system is placed symmetrically on the shaft, which reduces the system to a Jeffcott-Ro-tor. The second objective of this study was to analyze different defects in a simple fixed axis gear set. In particular, a cracked shaft, a cracked pinion and a chipped pinion as well as a healthy gear system were created and tested in Adams. The contact force between the two gears was monitored and the 2D and 3D frequency spectrum, as well as the Wavelet Transform, were plotted in order to compare the individual defects. It was shown that the Wavelet Transform is a powerful tool, capable of identifying a cracked gear with a non-constant speed. The last part of this study included fault detection with statistical methods as well as with the Sideband Energy Ratio (SER). The time domain signal of the individual faults were used to compare the mean, the standard deviation and the root mean square. Furthermore, the noise profile in the frequency spectrum was tracked with statistical methods using the mean and the standard deviation. It was demonstrated that it is possible to identify a cracked gear, as well as a chipped gear, with statistical methods. However, a cracked shaft could not be identified. The results also show that SER was only capable to identify major defects in a gear system such as a chipped tooth.
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Al, Rababa'A Abdel Razzaq. "Uncovering hidden information and relations in time series data with wavelet analysis : three case studies in finance." Thesis, University of Stirling, 2017. http://hdl.handle.net/1893/25961.
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This thesis aims to provide new insights into the importance of decomposing aggregate time series data using the Maximum Overlap Discrete Wavelet Transform. In particular, the analysis throughout this thesis involves decomposing aggregate financial time series data at hand into approximation (low-frequency) and detail (high-frequency) components. Following this, information and hidden relations can be extracted for different investment horizons, as matched with the detail components. The first study examines the ability of different GARCH models to forecast stock return volatility in eight international stock markets. The results demonstrate that de-noising the returns improves the accuracy of volatility forecasts regardless of the statistical test employed. After de-noising, the asymmetric GARCH approach tends to be preferred, although that result is not universal. Furthermore, wavelet de-noising is found to be more important at the key 99% Value-at-Risk level compared to the 95% level. The second study examines the impact of fourteen macroeconomic news announcements on the stock and bond return dynamic correlation in the U.S. from the day of the announcement up to sixteen days afterwards. Results conducted over the full sample offer very little evidence that macroeconomic news announcements affect the stock-bond return dynamic correlation. However, after controlling for the financial crisis of 2007-2008 several announcements become significant both on the announcement day and afterwards. Furthermore, the study observes that news released early in the day, i.e. before 12 pm, and in the first half of the month, exhibit a slower effect on the dynamic correlation than those released later in the month or later in the day. While several announcements exhibit significance in the 2008 crisis period, only CPI and Housing Starts show significant and consistent effects on the correlation outside the 2001, 2008 and 2011 crises periods. The final study investigates whether recent returns and the time-scaled return can predict the subsequent trading in ten stock markets. The study finds little evidence that recent returns do predict the subsequent trading, though this predictability is observed more over the long-run horizon. The study also finds a statistical relation between trading and return over the long-time investment horizons of [8-16] and [16-32] day periods. Yet, this relation is mostly a negative one, only being positive for developing countries. It also tends to be economically stronger during bull-periods.
Book chapters on the topic "Dynamic transformer rating"
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Kocharyan, Gevorg G., Alexey A. Ostapchuk, and Dmitry V. Pavlov. "Fault Sliding Modes—Governing, Evolution and Transformation." In Springer Tracts in Mechanical Engineering, 323–58. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_15.
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AbstractA brief summary of fundamental results obtained in the IDG RAS on the mechanics of sliding along faults and fractures is presented. Conditions of emergence of different sliding regimes, and regularities of their evolution were investigated in the laboratory, as well as in numerical and field experiments. All possible sliding regimes were realized in the laboratory, from creep to dynamic failure. Experiments on triggering the contact zone have demonstrated that even a weak external disturbance can cause failure of a “prepared” contact. It was experimentally proven that even small variations of the percentage of materials exhibiting velocity strengthening and velocity weakening in the fault principal slip zone may result in a significant variation of the share of seismic energy radiated during a fault slip event. The obtained results lead to the conclusion that the radiation efficiency of an earthquake and the fault slip mode are governed by the ratio of two parameters—the rate of decrease of resistance to shear along the fault and the shear stiffness of the enclosing massif. The ideas developed were used to determine the principal possibility to artificially transform the slidding regime of a section of a fault into a slow deformation mode with a low share of seismic wave radiation.
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Brahimi, Tayeb, and Ion Paraschivoiu. "Aerodynamic Analysis and Performance Prediction of VAWT and HAWT Using CARDAAV and Qblade Computer Codes." In Entropy and Exergy in Renewable Energy [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96343.
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Wind energy researchers have recently invited the scientific community to tackle three significant wind energy challenges to transform wind power into one of the more substantial, low-cost energy sources. The first challenge is to understand the physics behind wind energy resources better. The second challenge is to study and investigate the aerodynamics, structural, and dynamics of large-scale wind turbine machines. The third challenge is to enhance grid integration, network stability, and optimization. This chapter book attempts to tackle the second challenge by detailing the physics and mathematical modeling of wind turbine aerodynamic loads and the performance of horizontal and vertical axis wind turbines (HAWT & VAWT). This work underlines success in the development of the aerodynamic codes CARDAAV and Qbalde, with a focus on Blade Element Method (BEM) for studying the aerodynamic of wind turbines rotor blades, calculating the induced velocity fields, the aerodynamic normal and tangential forces, and the generated power as a function of a tip speed ration including dynamic stall and atmospheric turbulence. The codes have been successfully applied in HAWT and VAWT machines, and results show good agreement compared to experimental data. The strength of the BEM modeling lies in its simplicity and ability to include secondary effects and dynamic stall phenomena and require less computer time than vortex or CFD models. More work is now needed for the simulation of wind farms, the influence of the wake, the atmospheric wind flow, the structure and dynamics of large-scale machines, and the enhancement of energy capture, control, stability, optimization, and reliability.
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Chu, C. Y. Cyrus. "Sex Preferences and Two-Sex Models." In Population Dynamics. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195121582.003.0010.
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The demographic models I reviewed in previous chapters are all one-sex models, in which the sex referred to is usually the female. This setting can be justified if we assume either that the life-cycle vital rates (as functions of state variables) for both sexes are the same or that the population dynamics are determined by one sex alone, independent of the possibly relative abundance of the other sex. However, at least for human population, neither assumption is valid. The ratio of newborn girls and newborn boys is close to one, but is less than one for almost all countries in the world. The age-specific mortality rates of women are also lower than those of men worldwide. This is called sexual dimorphism in the demography literature. Such a dimorphism makes the study of two-sex models indispensable. If we look at the male and female vital rates, we find that the differences are small. Despite this small difference, population dynamics derived solely from male vital rates and those derived solely from female vital rates will show ever-increasing differences with the passage of time. Furthermore, because the intrinsic growth rates derived from male and female lines, respectively, are distinct, we cannot avoid the undesirable conclusion that, if we do not incorporate males and females in a unified model, eventually the sex ratio will become either zero or infinity, which is never the case in reality. This is the inconsistency we have to overcome while dealing with population models with two sexes. Another technical difficulty with two-sex modeling has to do with the irreducibility of the state-transition matrix. I mentioned in chapters 2 and 3 that in an age-specific one-sex model, because people older than a particular age, say β, are not fertile anymore, the age group older than β is an absorbing set; hence, our focus of population dynamics can be restricted to the age set [0, β]. This is why we can transform the n × n Leslie matrix to a Lolka renewal equation. In a two-sex model, however, there does not exist a common upper bound for the reproduction of both sexes, for a male older than β can marry a female younger than β and become fertile again.
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Zakaria, Jamaluddin, and Mohd Fadzli Mohd Salleh. "Wavelet Based Multicarrier Modulation (MCM) Systems: PAPR Analysis." In Wavelet Theory [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94579.
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Orthogonal frequency division multiplexing (OFDM) is a prominent system in transmitting multicarrier modulation (MCM) signals over selective fading channel. The system offers to attain a higher degree of bandwidth efficiency, higher data transmission, and robust to narrowband frequency interference. However, it incurs a high peak-to-average power ratio (PAPR) where the signals work in the nonlinear region of the high-power amplifier (HPA) results in poor performance. Besides, an attractive dynamic wavelet analysis and its derivatives such as wavelet packet transform (WPT) demonstrates almost the same criteria as the OFDM in MCM system. Wavelet surpasses Fourier based analysis by inherent flexibility in terms of windows function for non-stationary signal. In wavelet-based MCM systems (wavelet OFDM (WOFDM) and Wavelet packet OFDM (WP-OFDM)), the constructed orthogonal modulation signals behaves similar to the fast Fourier transform (FFT) does in the conventional OFDM (C-OFDM) system. With no cyclic prefix (CP) need to be applied, these orthogonal signals hold higher bandwidth efficiency. Hence, this chapter presents a comprehensive study on the manipulation of specified parameters using WP-OFDM, WOFDM and C-OFDM signals together with various wavelets under the additive white Gaussian noise (AWGN) channel.
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Parwez, Md Salik, Hasan Farooq, Ali Imran, and Hazem Refai. "Spectral Efficiency Self-Optimization through Dynamic User Clustering and Beam Steering." In Research Anthology on Developing and Optimizing 5G Networks and the Impact on Society, 79–94. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-7708-0.ch005.
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This paper presents a novel scheme for spectral efficiency (SE) optimization through clustering of users. By clustering users with respect to their geographical concentration we propose a solution for dynamic steering of antenna beam, i.e., antenna azimuth and tilt optimization with respect to the most focal point in a cell that would maximize overall SE in the system. The proposed framework thus introduces the notion of elastic cells that can be potential component of 5G networks. The proposed scheme decomposes large-scale system-wide optimization problem into small-scale local sub-problems and thus provides a low complexity solution for dynamic system wide optimization. Every sub-problem involves clustering of users to determine focal point of the cell for given user distribution in time and space, and determining new values of azimuth and tilt that would optimize the overall system SE performance. To this end, we propose three user clustering algorithms to transform a given user distribution into the focal points that can be used in optimization; the first is based on received signal to interference ratio (SIR) at the user; the second is based on received signal level (RSL) at the user; the third and final one is based on relative distances of users from the base stations. We also formulate and solve an optimization problem to determine optimal radii of clusters. The performances of proposed algorithms are evaluated through system level simulations. Performance comparison against benchmark where no elastic cell deployed, shows that a gain in spectral efficiency of up to 25% is possible depending upon user distribution in a cell.
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Marks II, Robert J. "Time-Frequency Representations." In Handbook of Fourier Analysis & Its Applications. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780195335927.003.0014.
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The Fourier transform is not particularly conducive in the illustration of the evolution of frequency with respect to time. A representation of the temporal evolution of the spectral content of a signal is referred to as a time-frequency representation (TFR). The TFR, in essence, attempts to measure the instantaneous spectrum of a dynamic signal at each point in time. Musical scores, in their most fundamental interpretation, are TFR’s. The fundamental frequency of the note is represented by the vertical location of the note on the staff. Time progresses as we read notes from left to right. The musical score shown in Figure 9.1 is an example. Temporal assignment is given by the note types. The 120 next to the quarter note indicates the piece should be played at 120 beats per minute. Thus, the duration of a quarter note is one half second. The frequency of the A above middle C is, by international standards, 440 Hertz. Adjacent notes notes have a ratio of 21/12. The note, A#, for example, has a frequency of 440 × 21/12 = 466.1637615 Hertz. Middle C, nine half tones (a.k.a. semitones or chromatic steps) below A, has a frequency of 440 × 2−9/12 = 261.6255653 Hertz. The interval of an octave doubles the frequency. The frequency of an octave above A is twelve half tones, or, 440 × 212/12 = 880 Hertz. The frequency spacings in the time-frequency representation of musical scores such as Figure 9.1 are thus logarithmic. This is made more clear in the alternate representation of the musical score in Figure 9.2 where time is on the horizontal axis and frequency on the vertical. At every point in time where there is no rest, a frequency is assigned. To make chords, numerous frequencies can be assigned to a point in time. Further discussion of the technical theory of western harmony is in Section 13.1.
Conference papers on the topic "Dynamic transformer rating"
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Jalal, T. S., N. Rashid, and B. van Vliet. "Implementation of Dynamic Transformer Rating in a distribution network." In 2012 IEEE International Conference on Power System Technology (POWERCON 2012). IEEE, 2012. http://dx.doi.org/10.1109/powercon.2012.6401328.
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Bracale, Antonio, Pierluigi Caramia, Guido Carpinelli, and Pasquale De Falco. "Probabilistic Management of Power Delivery Based on Dynamic Transformer Rating." In 2020 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS). IEEE, 2020. http://dx.doi.org/10.1109/pmaps47429.2020.9183656.
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Bracale, Antonio, Guido Carpinelli, and Pasquale De Falco. "A Predictive Stress-Strength Model Addressing the Dynamic Transformer Rating." In 2019 International Conference on Clean Electrical Power (ICCEP). IEEE, 2019. http://dx.doi.org/10.1109/iccep.2019.8890172.
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Chittock, L., D. Strickland, J. Mourik, C. Harrap, and J. Yang. "Distribution network transformer thermal modelling parameter determination for dynamic rating applications." In 8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016). Institution of Engineering and Technology, 2016. http://dx.doi.org/10.1049/cp.2016.0296.
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Yang, J., and D. Strickland. "Thermal modelling for dynamic transformer rating in low carbon distribution network operation." In 7th IET International Conference on Power Electronics, Machines and Drives (PEMD 2014). Institution of Engineering and Technology, 2014. http://dx.doi.org/10.1049/cp.2014.0330.
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Morozovska, Kateryna, Rikard Karlsson, and Patrik Hilber. "Dynamic rating of the wind farm transformer from the power system’s perspective." In 2021 IEEE Madrid PowerTech. IEEE, 2021. http://dx.doi.org/10.1109/powertech46648.2021.9494902.
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Daminov, Ildar, Anton Prokhorov, Raphael Caire, and Marie-Cecile Alvarez-Herault. "Receding horizon algorithm for dynamic transformer rating and its application for real-time economic dispatch." In 2019 IEEE Milan PowerTech. IEEE, 2019. http://dx.doi.org/10.1109/ptc.2019.8810511.
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Viafora, Nicola, Joachim Holboll, Syed Hamza H. Kazmi, Thomas H. Olesen, and Troels S. Sorensen. "Load Dispatch optimization using Dynamic Rating and Optimal Lifetime Utilization of Transformers." In 2019 IEEE Milan PowerTech. IEEE, 2019. http://dx.doi.org/10.1109/ptc.2019.8811002.
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Jalal, Thahirah Syed. "Case study: Implementation of Dynamic Rating for Transformers in a distribution network." In 2014 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT). IEEE, 2014. http://dx.doi.org/10.1109/isgt.2014.6816414.
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Yang, J., C. Harrap, D. Strickland, and L. Chittock. "Predicting practical benefits of dynamic asset ratings of 33KV distribution transformers." In IET International Conference on Resilience of Transmission and Distribution Networks (RTDN) 2015. Institution of Engineering and Technology, 2015. http://dx.doi.org/10.1049/cp.2015.0898.
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