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- Ariza Rocha, Oscar David, et al.
(författare)
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Dynamic rating assists cost-effective expansion of wind farms by utilizing the hidden capacity of transformers
- 2020
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Ingår i: International Journal of Electrical Power & Energy Systems. - : Elsevier. - 0142-0615 .- 1879-3517. ; 123
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic rating of power transmission devices is a technology that allows better equipment utilization through real-time monitoring of the weather conditions and the load. Dynamic rating of transformers is a fairly new technology if compared to the dynamic rating of power lines, and has a high potential for significantly improving component utilization while lowering investment costs on installing new transformers.The following work investigates how to utilize already operational transformers, which are used for wind farm connection, for expanding wind generation capacity. Also, this paper shows improvements that dynamic transformer rating can bring to both power grid operators and wind farm owners by exploring the economic benefits of expanding wind parks without investing in new power transformers. Connecting additional wind turbines at sites with high wind potential after the wind park is already in exploitation can assist in lowering electricity price and provide a possibility of less risky investment in the wind energy sector. This paper uses transformer thermal modelling and wind farm expansion techniques such as convolution method and product method to investigate to which extent existing wind farms can be expanded using already installed transformer units.Five transformer locations and nine units are studied for finding the potential of dynamic transformer rating for network expansion applications. The analysis shows that the optimal expansion of wind power from a generator perspective is around 30%" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">% to 50%" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">%, although, it can be limited further by network restrictions. A possibility to use a large component, such as power transformer, closer to its full potential can provide material and cost savings for building new devices and decrease investment costs on manufacturing, transportation and installation of new units. Dynamic rating of power transformers can also increase the socio-economic benefits of renewable energy by lowering electricity price from renewables and incentivize an increased share of green power in electricity markets.
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| 3. |
- Ariza Rocha, Oscar David, et al.
(författare)
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Dynamic rating assists cost-effective expansion of wind farms byutilizing hidden capacity of transformers
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Dynamic rating of power transmission devices is a technology that allows better equipment utilization through real-time information about the system state. Dynamic rating of transformers is a fairly new technology if compared to dynamic rating of power lines, and has high potential for significantly improving component utilization while lowering investment costs on installing new transformers.Dynamic transformer rating increases the rating of the transformer considering load and temperature variations without affecting safe operation. Dynamic rating is highly suitable for being used in conjunction with renewable energy generation, specifically wind power. The following work investigates how to utilize existing transformers, which are under exploitation at wind farms, for expanding wind generation capacity. Also, this paper shows improvements that dynamic rating can bring to both power grid operators and wind farm owners by exploring the economic benefits of expanding wind parks while using dynamic rating. Connecting additional wind turbines with the same transformer at sites with high wind capacity after the wind park is already in exploitation can assist in lowering electricity price and provide a possibility of less risky investment in wind power.Five transformer locations and nine units are studied for finding the potential of dynamic transformer rating for network expansion applications. The analysis shows that the optimal expansion of wind power from a generator perspective is around 30 % to 50 %, although, it can be limited further by network restrictions. A possibility to use a large device, suchas power transformer, closer to its full potential can provide material and cost savings for building new devices and decrease investment costs on manufacturing, transportation and installation of new units. Dynamic rating of power transformers can also increase the socio-economic benefits of renewable energy by lowering electricity price from renewables and incentivize an increased share of green power in electricity markets.
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| 5. |
- Danielsson, Henrik, et al.
(författare)
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A Systematic Review of Longitudinal Trajectories of Mental Health Problems in Children with Neurodevelopmental Disabilities
- 2024
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Ingår i: Journal of Developmental and Physical Disabilities. - : Springer. - 1056-263X .- 1573-3580. ; 36, s. 203-242
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Forskningsöversikt (refereegranskat)abstract
- To review the longitudinal trajectories - and the factors influencing their development - of mental health problems in children with neurodevelopmental disabilities. Systematic review methods were employed. Searches of six databases used keywords and MeSH terms related to children with neurodevelopmental disabilities, mental health problems, and longitudinal research. After the removal of duplicates, reviewers independently screened records for inclusion, extracted data (outcomes and influencing factors), and evaluated the risk of bias. Findings were tabulated and synthesized using graphs and a narrative. Searches identified 94,662 unique records, from which 49 publications were included. The median publication year was 2015. Children with attention deficit hyperactivity disorder were the most commonly included population in retrieved studies. In almost 50% of studies, trajectories of mental health problems changed by < 10% between the first and last time point. Despite multiple studies reporting longitudinal trajectories of mental health problems, greater conceptual clarity and consideration of the measures included in research is needed, along with the inclusion of a more diverse range of populations of children with neurodevelopmental disabilities.
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| 7. |
- Ivarsson, Lars, 1969-, et al.
(författare)
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Anställdas upplevelse av interaktionen med kunder/mottagare i tjänstesektorn
- 2008
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Ingår i: Arbetsmarknad & Arbetsliv. - Karlstad : Karlstads universitet. - 1400-9692 .- 2002-343X. ; 14:4, s. 43-61
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Tidskriftsartikel (refereegranskat)abstract
- I denna artikel görs dels en summering av forskning som uttalar sig om arbetsvillkor för anställda med hög grad av kundkontakt, dels påvisas utbredningen av dessa villkor i den svenska tjänstesektorn. Det visar sig att tjänstearbete präglas av rutinisering, krav på utseende samt styrning av känslor. Samtidigt är kundkontakter en källa till arbetstillfredsställelse och denna arbetstillfredsställelse är mer utbredd bland anställda som identifierar sig med verksamhetens kunder.
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- Ivarsson, Lars, 1969-, et al.
(författare)
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Att leverera hantverkstjänster – en studie av näringsidkares upplevelser av affärsrelationen
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Under 2009 inkom det omkring 10 000 klagomål rörande hantverkare och hantverkstjänster till landets konsumentvägledningar. Detta är en ökning med tio procent jämfört med året innan. Vanligtvis handlar klagomålen om att hantverkstjänsten blivit dyrare än överenskommet eller att arbetet inte har utförts på det sätt konsumenten räknat med. Anledningen till det ökade klagomålet på hantverkstjänster kan enligt Helena Olofsson, boendeexpert på Konsumentverket, möjligtvis hänvisas till införandet av ROT-avdraget (Renovering, Ombyggnad, Tillbyggnad) som i korthet innebär attprivatkunder som anlitar hantverkare kan få en skattereduktion på 50 procentav arbetskostnaden. Denna förklaring bygger på ett antagande om att ROTavdragetmedför att fler personer väljer att anlita hantverkare nu närkostnaderna blir väsentligt lägre. Det förefaller logiskt att ett ökat anlitande också medför ett ökande av kunders missnöje och därmed klagomål. Den ökande andelen klagomål har föranlett en rad delstudier kring hur kunderoch hantverkare upplever affärsrelationen. Två av dessa är kvantitativt orienterade och vänder sig till privatkunder respektive hantverkare, i syfte att kartlägga utbredningen av kundmissnöje. Föreliggande rapport fokuserarnäringsidkares upplevelser av relationen.
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