| 1. |
- 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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| 2. |
- Ariza Rocha, Oscar David, et al.
(författare)
-
Dynamic rating assists cost-effective expansion of wind farms byutilizing hidden capacity of transformers
-
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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| 3. |
- Bahaloo, Hassan, 1983-, et al.
(författare)
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On the failure initiation in the proximal human femur under simulated sideways fall
- 2018
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Ingår i: Annals of Biomedical Engineering. - : Springer. - 0090-6964 .- 1573-9686. ; 46, s. 270-283
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Tidskriftsartikel (refereegranskat)abstract
- The limitations of areal bone mineral density measurements for identifying at-risk individuals have led to the development of alternative screening methods for hip fracture risk including the use of geometrical measurements from the proximal femur and subject specific finite element analysis (FEA) for predicting femoral strength, based on quantitative CT data (qCT). However, these methods need more development to gain widespread clinical applications. This study had three aims: To investigate whether proximal femur geometrical parameters correlate with obtained femur peak force during the impact testing; to examine whether or not failure of the proximal femur initiates in the cancellous (trabecular) bone; and finally, to examine whether or not surface fracture initiates in the places where holes perforate the cortex of the proximal femur. We found that cortical thickness around the trochanteric-fossa is significantly correlated to the peak force obtained from simulated sideways falling (R 2 = 0.69) more so than femoral neck cortical thickness (R 2 = 0.15). Dynamic macro level FE simulations predicted that fracture generally initiates in the cancellous bone compartments. Moreover, our micro level FEA results indicated that surface holes may be involved in primary failure events.
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| 4. |
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| 5. |
- Galvan-Valencia, Oscar, et al.
(författare)
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Associations of salivary aldosterone levels during pregnancy with maternal blood pressure and birth weight-for-gestational age in a Mexico City birth cohort
- 2024
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Ingår i: Journal of Perinatology. - : Springer Nature. - 0743-8346 .- 1476-5543. ; 44:5, s. 643-649
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveTo determine associations of maternal salivary aldosterone with blood pressure (BP) in pregnancy and infant birth weight-for-gestational age (BWGA).MethodsWe measured maternal salivary aldosterone, BP and BWGA z-scores in 471 Mexico City pregnancy cohort participants and performed multivariable linear regression of BP and BWGA on log-aldosterone levels.ResultsLog-aldosterone was positively associated with diastolic BP (beta = 0.12 95% CI: 0.04, 0.21). There were no main effects of log-aldosterone on BWGA. However, we detected an interaction between log-aldosterone and BP in association with BWGA; higher log-aldosterone was associated with lower BWGA in the lowest (beta = -0.12, 95% CI: -0.26, 0.02) and highest (beta = -0.12, 95% CI: -0.29, 0.06) BP tertiles. In contrast, in the middle BP tertile the association was positive (beta = 0.09, 95% CI: -0.02, 0.20), p for interaction = 0.03.ConclusionHigher maternal salivary aldosterone is positively associated with diastolic BP and may affect fetal growth differently depending on concurrent maternal blood pressure.
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