High Frequency Dielectric Properties and Losses in Partial Discharge Resistant Rotating Machine Insulation

The complex permittivity of glass-fiber and polyimide backed mica tape for winding insulation in rotating machines have been investigated using a dielectric spectrometer. A frequency ranging from 10 ‐2 Hz to 10 6 Hz and a temperature ranging from 20 °C to 150 °C was applied to both pristine samples and samples aged for one week at 150 °C and 200 °C, respectively. The real part of permittivity, real part of conductivity and loss factor increased for decreasing frequencies and increasing temperatures. For both tape materials, a significant decrease was seen after one week at high temperature, but for the polyimide tape the change was less significant at 150 °C. This temperature is below the thermal class of the insulation. The observed decrease in the real part of permittivity, and hence decreased loss factor is possibly due to a continuing curing of the resin in the insulation system.High Frequency Dielectric Properties and Losses in Partial Discharge Resistant Rotating Machine InsulationacceptedVersio

Hybrid Method for Numerical Implementation of Segmented Power Cable Conductors in Finite-element Based Ampacity Calculation

This paper addresses challenges with modelling of segmented power cable conductors using finite element analysis (FEA) for ampacity calculation. Segmented conductors improve current distribution by minimizing skin and proximity effects, thus reducing conductor losses. 2D FEA simulation offers high flexibility and accuracy beyond IEC 60287 for complex laying geometries, but the modelling of losses in segmented constructions using FEA has proven difficult due to the big difference in wire size and twisting pitch, requiring great amounts of computational power. In this paper a hybrid method is proposed, in which the IEC 60287 empirical formulae for segmented conductors are included in a 2D FEA model. The proposed method shows a good correspondence to IEC standard calculations, with deviations in conductor AC resistance of less than 1 %.Hybrid Method for Numerical Implementation of Segmented Power Cable Conductors in Finite-element Based Ampacity CalculationpublishedVersio

Partial Discharge Inception Voltage of Pigtail Samples with Type II Insulation and Sinusoidal vs Switched Voltage

Partial discharge inception voltage (PDIV) under sinusoidal voltage and switched voltage with dV/dt of 20 V/ns have been investigated for pigtail samples with type II insulation consisting of Litz wire as conductor and mica-Kapton tape as groundwall insulation. Voltage was increased in steps of 100 V peak with duration of 60 s for both sinusoidal and switched voltage with switching frequency of 45 Hz until PDs were observed. No significant difference in the PDIV for sinusoidal and switched voltage was found. Further, sinusoidal voltage was applied until breakdown. No correlation between breakdown voltage and PDIV was found, but very large PDs (∼ 100 nC) consequently initiated 4-5 kV below breakdown voltage. Dissection of the tested pigtails showed multiple voids in the wedge between Litz wire strands and the inner insulation layer, suspected to cause the main portion of the PDs. Such voids with only a thin varnish covering the electrode surfaces would get less significant space charge build-up. Therefore, a low field enhancement from space charges is expected during the fast voltage change of switched voltage.Partial Discharge Inception Voltage of Pigtail Samples with Type II Insulation and Sinusoidal vs Switched VoltageacceptedVersio

Full-scale case study of a road crossing thermal bottleneck in buried MV cable installation

Infrastructures such as road crossings, are often limiting the ampacity of a cable link due to poor thermal properties. In order to fully utilize the true loading capacity of the cable, thermal modelling with correct input parameters should be applied. In this work, a full scale artificial road crossing have been constructed and characterized, and temperature measurements have been compared with calculations performed according to IEC 60287 and finite-element analysis (FEA). It was found that calculations according to IEC provide a good fit to measured temperature profiles by adjusting the unknown mean thermal resistivity of the material layers outside the pipe. The thermal properties of road construction materials can be challenging to measure, and in order to provide accurate ampacity calculations further work should be focused on this.publishedVersio

Chemoautotrophic growth of ammonia-oxidizing Thaumarchaeota enriched from a pelagic redox gradient in the Baltic Sea

Ammonia-oxidizing archaea (AOA) are an important component of the planktonic community in aquatic habitats, linking nitrogen and carbon cycles through nitrification and carbon fixation. Therefore, measurements of these processes in culture-based experiments can provide insights into their contributions to energy conservation and biomass production by specific AOA. In this study, by enriching AOA from a brackish, oxygen-depleted water-column in the Landsort Deep, central Baltic Sea, we were able to investigate ammonium oxidation, chemoautotrophy, and growth in seawater batch experiments. The highly enriched culture consisted of up to 97% archaea, with maximal archaeal numbers of 2.9 × 107 cells mL-1. Phylogenetic analysis of the 16S rRNA and ammonia monooxygenase subunit A (amoA) gene sequences revealed an affiliation with assemblages from low-salinity and freshwater habitats, with Candidatus Nitrosoarchaeum limnia as the closest relative. Growth correlated significantly with nitrite production, ammonium consumption, and CO2 fixation, which occurred at a ratio of 10 atoms N oxidized per 1 atom C fixed. According to the carbon balance, AOA biomass production can be entirely explained by chemoautotrophy. The cellular carbon content was estimated to be 9 fg C per cell. Single-cell-based 13C and 15N labeling experiments and analysis by nano-scale secondary ion mass spectrometry provided further evidence that cellular carbon was derived from bicarbonate and that ammonium was taken up by the cells. Our study therefore revealed that growth by an AOA belonging to the genus Nitrosoarchaeum can be sustained largely by chemoautotrophy

How to Plug In the Fishing Fleet: Connectors in charging infrastructure for small fishing boats

Fishing fleets are targeted for electrification in many parts of the world. These vessels represent a large potential for emission reductions by transitioning from fossil to hybrid and electric propulsion. However, a massive electrification of such vessels requires a disruptive green shift, introducing safe and reliable battery charging infrastructure along the coastline. Up to now, electric energy has been supplied only, if supplied at all, for auxiliary loads, such as lighting, heating, and ventilation, when fishing boats are in a harbor. The standard connection method has been through industrial connectors. In other sectors, such as automotive, other connector types are used. When batteries are installed on fishing vessels, high charging powers and currents are deployed, calling for robust connector solutions.How to Plug In the Fishing Fleet: Connectors in charging infrastructure for small fishing boatsacceptedVersio

Use of Data-Driven Approaches for Defect Classification in Stator Winding Insulation

Partial discharges (PD) in the high voltage insulation systems are both a symptom and cause of terminal and impending failures. The use of data-driven methods based on PD measurements will enable predictive strategies to replace traditional maintenance strategies. This paper employs machine learningbased classification models to identify and characterize PD signals originating from lab-made artificial defects in epoxy-mica material samples. Three different PD sources were studied: surface discharges in air, corona discharges, and discharges caused by internal cavities/delaminations. To generate high-quality datasets for the training, validation, and testing of classification models, Phase-Resolved PD (PRPD) data for each test object was obtained at room temperature under 50 Hz AC excitation at 10 % above the PD inception voltage (PDIV) of each sample. Relevant statistical and deterministic features were extracted for each observation and were labeled based on the defect type (supervised learning). Finally, the trained and validated ML models were used to identify PD sources in the service-aged stator winding insulation. Support vector machines (SVM), ensemble, and k-nearest neighbor (kNN) algorithms achieved significantly high accuracy (≥ 95 %) of defect identification.publishedVersio

The effects of the serotonin transporter polymorphism and age on frontal white matter integrity in healthy adult women

Studies of populations at genetic risk have the potential to explore the underlying structural and functional mechanisms in the development of psychological disorders. The polymorphic region (5-HTTLPR) in the serotonin transporter gene (SLC6A4) has been associated with major depression (MDD) (Caspi et al., 2003). In healthy women, variation in the human brain white matter microstructure integrity in the uncinate fascicule (UF) has been suggested as an endophenotypes in the development of MDD. Pacheco et al. (2009) found a unique effect of age and 5-HTTLPR within the left frontal UF. The present study examined whether these associations persist along the adult life span. Thirty-seven right-handed healthy women between 21 and 61 years of age were invited for a diffusion MRI study. The functional polymorphism 5-HTTLPR located in the promoter region of the SLC6A4 gene was genotyped using polymerase chain reaction (PCR). Fractional anisotropy (FA) was generated for the UF based on Tract-Based Spatial Statistics (TBSS). Models of emotion regulation circuitry suggest that working memory is important in conscious emotion regulation (Price and Drevets, 2010). To explore if 5-HTTLPR is related to this aspects of emotion processing, a working memory pathway, the superior longitudinal fascicule (SLF) was included. The results demonstrate that age may explain the hypothesized association between 5-HTTLPR and frontal UF white matter integrity in healthy adult women. Both white matter changes associated with the aging process and those associated with growth and development may explain why the earlier reported unique effects of genotype in frontal UF FA do not persist into adulthood

Utilization of farm animal genetic resources in a changing agro-ecological environment in the Nordic countries

201