| 1. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Dynamisk belastningsförmåga av luftledningar : Överbelastningsskydd och tillförlitlighet
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Dynamisk belastningsförmåga är att sätt att möjliggöra en högre användning av överföringskapacitet av en luftledning utan att det finns en ökad risk att ledningen blir överbelastad. Från prognosen eller mätning av väderparametrar görs det en uppskattning av hur mycket ström en luftledning klarar.Metoden har studerats förut och det pågår en hel del forskning kring detta. Det som dock får begränsat med uppmärksamhet är dynamisk belastningsförmågas roll i överbelastningsskydd, dess olika osäkerheter och tillförlitlighet. Det är dessa aspekter som var utgångspunkter för studien som presenteras i denna rapport.Det visas att det finns en stor potential för dynamisk belastningsförmåga under vintermånaderna i Sverige, precis då som det behövs mer överföringsförmåga. Det möjliggör bland annat en större integrering av elbilsladdning i elnätet.En metod för dynamisk belastningsförmåga i kombination med överbelastningsskydd har introducerats; sannolikheten att ledningen är överbelastat är kriteriet för att bedöma om det behövs åtgärder för att förebygga överbelastning. Denna stokastiska metod kan användas under driftplanering (till exempel dagen innan), under driften (till exempel för att bedöma driftsäkerheten) och som en skyddsåtgärd (i fall ingen av de förebyggande åtgärderna hjälper).Belastningsförmågan och sannolikhet på överbelastning har beräknads för varje timme under en åttaårsperiod för en hypotetisk ledning till en hypotetisk stad i Norra Sverige, Belasteå. Alla ingångsparametrar var dock baserade på verklig data och inte hypotetiska alls.Rapporten innehåller en diskussion angående en del förslag på tillämpningar och utvidgning av metoden. Där ingår det bland annat tillämpningar i det svenska elnätet, utveckling av liknade metoder för kablar och transformatorer, samt tillämpningar då ledartemperaturen mäts.
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| 2. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Enhancing the hosting capacity of distribution transformers for using dynamic component rating
- 2022
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Ingår i: International Journal of Electrical Power & Energy Systems. - : Elsevier. - 0142-0615 .- 1879-3517. ; 142, Part A
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing deployment of solar power, high photovoltaic (PV) penetration is expected to adversely impact the distribution grid. One of the challenges relates to the power flow and transfer capacity of the distribution transformers. Transformers might not have sufficient capacity to accommodate for all the downstream PV to feed back to a higher voltage level during sunny periods with low consumption. In this paper, we estimate the transformer hosting capacity considering dynamic thermal rating for residential consumption with increasing amounts of PV penetration. This paper analyzes the impact of PV integration and increased consumption on the aging of a transformer. The potential of dynamic rating to enhance transformer hosting capacity is studied under varying environmental conditions.
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| 3. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Increasing the Grid Capacity for Electric Vehicle Charging using Dynamic Rating
- 2021
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Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 1777-1781
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Konferensbidrag (refereegranskat)abstract
- With a noticeable increase in the number of electric vehicles\,(EVs) in coming years, lack of grid capacity may become a barrier for electrification of transportation. This study presents the application of dynamic rating to increase the available transfer capacity and to enable more increase in consumption. Through stochastic calculation the hourly available capacity has been estimated which then used to calculate the hosting capacity. In this sense, the probability of overloading considering different EV types is calculated. The results show that the probabilistic hosting capacity would be a better indication to estimate the minimum and maximum EV load demand in the coming hours.
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| 4. |
- Hajeforosh, Seyede Fatemeh, 1988-
(författare)
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Multiple Aspects of Dynamic Rating in the Power System
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased consumption and increased use of renewable energy make overhead lines and transformers more often congested. Dynamic rating (DR) uses a time-depending maximum permissible current instead of a long-term-fixed rating; it is an effective solution to upgrade the capacity of existing grid assets to minimize this congestion. Dynamic line rating (DLR) considers how the weather affects the thermal behavior of the conductor and therewith its rating; environmental parameters as well as conductor characteristics have to be considered. Likewise, dynamic rating of transformers (DTR) relies on a thermal assessment of the hottest spot in the transformer windings. The hot-spot temperature is dependent on the ambient temperature, loading, and transformer’s cooling system.In this thesis, a number of lesser-studied aspects of DR are studied: stochastic modeling of the rating; relations between protection, reliability and rating; risk assessment for line selection when using DLR; and increased transformer hosting capacity (HC) in the presence of solar photovoltaic (PV).In the first part of the work, the focus is on the stochastic modeling of DLR and its relation to the protection operation. Actual line rating is considered a random variable in the protection system for a more flexible decision-making. Different sources of uncertainties are modeled using suitable probability density functions. The method allows for a transparent trade-off between the risk of failure to take measures and the risk of unnecessary measures against overload. The results depicts that deterministic DLR could result in high probabilities of overloading or would require large safety margins. While, a stochastic approach will allow for both small margins and appropriate risks. A generic model is introduced to consider DLR reliability from two different viewpoints: errors and failures of components that would affect the calculation of the rating; and the impact of a DLR failure on the power system. The qualitative reliability study highlights that it is important to update the protection settings on a real-time basis. In the second part of the work, a risk assessment framework is proposed to select the minimum set of overhead lines for DLR implementation. Results show a possible increase of permissible hosting capacity (HC) for electric-vehicle charging by up to 80% (depending on the test system and initial data) with low interruption costs and reduced risk of congestion. Furthermore, the improvement in the transformer HC by using DTR has been quantified. The results indicate that depending on the HC performance indices, the transformer can be loaded beyond the normal operational limits up to 35% to host PV and up to 100% for increased consumption.
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| 5. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Reliability Aspects of Battery Energy Storage in the Power Grid
- 2020
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Ingår i: Proceedings of 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe) 26-28 October, 2020. - : IEEE. ; , s. 121-125
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Konferensbidrag (refereegranskat)abstract
- This paper gives an overview of the components and failure modes that should be considered when studying the reliability of grid-size Battery Energy Storage System (BESS). Next to failures of the primary component, a reliability study should consider the failure of the protection, failure of the communication, and failure of the control system. After all the diagnosed failures, qualitative fault tree analysis (FTA) based on Boolean logic is introduced as a basis of further analysis. Storage installations have a number of applications, each of which requires a different look at the reliability. The following applications are discussed in the paper: improving supply reliability, compensation power flows, market participation and frequency control.
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| 6. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Reliability Aspects of Dynamic Thermal Rating in the Power Grid
- 2021
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Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 1086-1090
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Konferensbidrag (refereegranskat)abstract
- This paper is an overview of the components and failure modes that should be considered when studying the reliability of dynamic thermal rating (DTR) in the power system. A reliability study should include failure of a measurement device, failure of the communication, model inaccuracy, and failure of the control system. The presence of the DTR system increases the risks of unnecessary operation and lack of action in power system due to an error in DTR calculation. This impact is studied qualitatively in this paper; it is of great importance during operation and maintenance of the power system.
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| 7. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Risk Assessment Criteria for Utilizing Dynamic Line Rating in Presence of Electric Vehicles Uncertainty
- 2022
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Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 212
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic line rating (DLR) is a grid enhancing technology to enable a more effective use of transmission capacity of existing infrastructure.~The growth in load consumption along with a high integration of electric vehicles (EV) highlights the potential of DLR utilization for reducing the congestion costs and overloading risks.~Selecting the proper lines for DLR implementation is necessary to exploit optimally the benefits of DLR. In this paper, we propose risk assessment criteria to select proper lines for DLR implementation to minimize the system operation costs and the risk of overloading caused by high EV integration.A stochastic method is introduced to model the uncertain behavior of EV in charging stations. Furthermore, we analyze the impact of inherent uncertainties in DLR by comparing different DLR percentiles. The benefits of using DLR in different percentiles are then quantified in terms of supply and interruption costs.The results show improvements in system supply cost, system reliability, and operation risks.
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| 8. |
- Hajeforosh, Seyede Fatemeh, 1988-, et al.
(författare)
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Uncertainties in radiation modelling for overhead lines and their impact on the ampacity
- 2021
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Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 2366-2370
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Konferensbidrag (refereegranskat)abstract
- This paper gives a detailed analysis of the radiation terms in the heating balance for overhead conductors. The terms in the radiation balance determine the rating of an overhead line for use in dynamic line rating schemes. These radiation terms are often not considered and in which there is a relatively big uncertainty. The available knowledge and the different uncertainties are summarized, for radiation from the environment reaching the conductor, for thermal emission from the conductor and for heating of the conductor due to direct and indicated solar irradiation. The impact of the uncertainties on the uncertainty in line rating is quantified and it is concluded that the error made is around 10 % for low wind speed.
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