| 1. |
- Heggebo, L. C., et al.
(författare)
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Investigating survival, quality of life and cognition in PROton versus photon therapy for IDH-mutated diffuse grade 2 and 3 GLIOmas (PRO-GLIO): a randomised controlled trial in Norway and Sweden
- 2023
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Ingår i: Bmj Open. - : BMJ. - 2044-6055. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionThe use of proton therapy increases globally despite a lack of randomised controlled trials demonstrating its efficacy and safety. Proton therapy enables sparing of non-neoplastic tissue from radiation. This is principally beneficial and holds promise of reduced long-term side effects. However, the sparing of seemingly non-cancerous tissue is not necessarily positive for isocitrate dehydrogenase (IDH)-mutated diffuse gliomas grade 2-3, which have a diffuse growth pattern. With their relatively good prognosis, yet incurable nature, therapy needs to be delicately balanced to achieve a maximal survival benefit combined with an optimised quality of life.Methods and analysisPRO-GLIO (PROton versus photon therapy in IDH-mutated diffuse grade 2 and 3 GLIOmas) is an open-label, multicentre, randomised phase III non-inferiority study. 224 patients aged 18-65 years with IDH-mutated diffuse gliomas grade 2-3 from Norway and Sweden will be randomised 1:1 to radiotherapy delivered with protons (experimental arm) or photons (standard arm). First intervention-free survival at 2 years is the primary endpoint. Key secondary endpoints are fatigue and cognitive impairment, both at 2 years. Additional secondary outcomes include several survival measures, health-related quality of life parameters and health economy endpoints.Ethics and disseminationTo implement proton therapy as part of standard of care for patients with IDH-mutated diffuse gliomas grade 2-3, it should be deemed safe. With its randomised controlled design testing proton versus photon therapy, PRO-GLIO will provide important information for this patient population concerning safety, cognition, fatigue and other quality of life parameters. As proton therapy is considerably more costly than its photon counterpart, cost-effectiveness will also be evaluated. PRO-GLIO is approved by ethical committees in Norway (Regional Committee for Medical & Health Research Ethics) and Sweden (The Swedish Ethical Review Authority) and patient inclusion has commenced. Trial results will be published in international peer-reviewed journals, relevant conferences, national and international meetings and expert forums.Trial registration numberClinicalTrials.gov Registry (NCT05190172).
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| 6. |
- Gubanski, S. M., et al.
(författare)
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Performance of biologically contaminated high voltage insulators
- 2006
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Konferensbidrag (refereegranskat)abstract
- Biological growth has been observed on insulators installed all over the world. However, so far, its impact on insulator performance is not well known. This paper summarizes the work published in the field. Based on the gathered experiences, it can be concluded that microbiological growth is unlikely to cause severe degradation of the rubber housings of non-ceramic insulators. Furthermore, it seems that the impact of growth on the insulator performance is rather low. Techniques available for detection and characterisation of growth on insulators are also described and discusses. Among those, laser-induced fluorescence (LIF) spectroscopy has been found to give good results in remote detection of micro-organisms.
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| 12. |
- Abeywickrama, K. G. Nilanga B., et al.
(författare)
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Determination of complex permeability of silicon steel for use in high-frequency modeling of power transformers
- 2008
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Ingår i: IEEE transactions on magnetics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9464 .- 1941-0069. ; 44:4, s. 438-444
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Tidskriftsartikel (refereegranskat)abstract
- Information about frequency dependence of complex permeability of silicon steel is a vital input parameter in calculations of transformer winding inductance used for modeling. high-frequency behavior (100 Hz-1 MHz). We present two ways of determining small signal complex permeability spectra in frequency domain and compare and discuss the results. The first method is based on an optimization procedure, in which inductance of a winding is measured and calculated by analytical formulas and finite-element modeling. The second method makes use of a single sheet tester. We show that the magnitude of effective permeability of the silicon steel laminations remains significant up to about 100 kHz. We also report on the effect of magnetic viscosity on complex permeability.
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| 13. |
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| 14. |
- Bin, Ma, et al.
(författare)
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Dielectric Properties and Resistance to Corona and Ozone of Epoxy Compositions Filled with Micro- and Nano-fillers
- 2009
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Ingår i: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena. ; , s. -380
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Konferensbidrag (refereegranskat)abstract
- This paper describes activities aiming to evaluate and compare the resistance to a prolonged corona and ozone exposure for a range of epoxy based compositions filled with micro- and nano-fillers of silica at different proportions. It has been earlier shown for this system that substitution of 5 wt% of micro-filler by nano-filler slightly improved mechanical properties, yielding an increase in Young's modulus, tensile strength and elongation at break. At the same time, the toughness of the systems decreased with the addition of nano-fillers indicating a poor particle-matrix interaction, which was in accordance with the prior art claiming that this interaction is weaker in case of SiO 2 nano-particles, as for example compared to Al 2O 3 nano-particles. For the exposure to corona and ozone a methodology employing a multiple-needle electrode system was used, as recommended by CIGRE working group WG D1.14. Measurements of surface resistivity, bulk resistivity as well as dielectric response (DR) at broad frequency range (10 -4-10 3 Hz) were performed on new samples of the investigated compositions and after each of two sequences of the corona-ozone treatment, lasting 100hours each. It was found that the long-term corona-ozone exposure had obvious effect on surface resistivity for all the compositions investigated and the contents of the micro- and nano-fillers played a significant role in the observed changes. On the other hand, bulk resisitivity, dielectric permittivity as well as dissipation factor, all being the properties of material bulk, did not exhibit high sensitivity to the exposure.
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| 17. |
- Florkowski, M., et al.
(författare)
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Condition Monitoring and Diagnostics
- 2013
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 20:6, s. 1961-1961
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 18. |
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| 21. |
- Gubanski, M., et al.
(författare)
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Quality of life in patients with advanced gastric cancer sequentially treated with docetaxel and irinotecan with 5-fluorouracil and folinic acid (leucovin)
- 2014
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Ingår i: Medical Oncology. - : Springer Science and Business Media LLC. - 1357-0560 .- 1559-131X. ; 31:4, s. 906-
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Tidskriftsartikel (refereegranskat)abstract
- With a median overall survival of only 9-13 months in patients with advanced gastric cancer (GC), the quality of life (QoL) during the palliative treatment remains a key issue. Furthermore, when combinations of two or three drugs are used, the impact on QoL should be carefully evaluated. This was studied within the GATAC trial in patients sequentially treated with docetaxel and irinoteca n with 5-fluorouracil and leucovorin (5-Fu/ Lv). Patients with previously untreated advanced GC were randomly assigned to start with docetaxel 45 mg/m(2) (arm T) or irinotecan 180 mg/m(2) (arm C) with bolus and 44 h infusion of 5-Fu/Lv (D1, q2 weeks). After four courses, there was a prescheduled crossover to the alternative regimen for four additional courses. QoL was measured with the EORTC QLQ-C30 questionnaire at the start of the treatment, at crossover and after completing treatment with both regimens. Eighty-one patients were randomized, and 78 patients started treatment. A total of 191 completed QoL questionnaires were collected. There were no statistically significant differences in QoL scores between the two treatment groups and no changes in mean scores during the 16 weeks of treatment. During the last 8 weeks of treatment, a significantly larger portion of patients with radiological response reported sustained or better QoL scores than those with no radiological response (82 vs. 50 %, p = 0.007). Chemotherapy in advanced GC did not affect QoL average scores. Patients with non-responding tumours reported more often a decline in the global QoL score. The concept of the pre-scheduled switch of chemotherapy regimens prior to progression should be further studied in this disease, as it appears effective, tolerable and not to negatively affect QoL.
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| 22. |
- Gubanski, Stanislaw, 1950, et al.
(författare)
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Ageing of Silicone Rubber Insulators in Coastal and Inland Tropical Environment
- 2010
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 17:2, s. 326-333
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents investigations on the performance of 33 kV silicone rubber insulators characterized by different creepage lengths, which aimed to find out whether the insulators could permanently work when electrically stressed beyond the recommended limits in polluted and clean tropical environments. The study was performed under natural field and laboratory conditions. The insulators tested included eight types of silicone rubber composite insulators, one type of hybrid silicone-ceramic insulator and one semi-conducting glazed porcelain insulator, while ordinary porcelain and glass insulators were used as reference. During the field investigation, two sets of the insulators were separately installed and energized in coastal and inland parts of Sri Lanka, being by that exposed to marine and clean tropical environments. Their performances were periodically evaluated by visual inspections and measurements of hydrophobicity class. After five years of field exposure, the insulator performances were evaluated in laboratory by measurements of leakage currents under clean fog conditions and of wet flashover voltage. A third set of the insulators was aged in laboratory for 1000 hours inside a salt fog chamber where the insulators were continuously energized and daily sprayed with salt solution for eight hours and left to rest for remaining 16 hours. This treatment represented conditions similar as those in the field i.e. insulators exposed to salt sprays during monsoons. The insulator performances were investigated by measurements of leakage currents and classifying their patterns into different categories, i.e. capacitive, resistive, non-linear, discharge and strong discharge types, by means of fast Fourier transform and short time Fourier transform analyses. It was found that the long-term field exposure yielded weaker insulator deterioration than the salt fog chamber ageing, which indicated for a possibility to increase the electric stress on silicone rubber insulators to levels higher than the ones used today on glass and porcelain counterparts.
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| 23. |
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| 24. |
- Gubanski, S. M., et al.
(författare)
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Performance and diagnostics of biologically contaminated insulators
- 2007
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Ingår i: ICPADM 2006. - : IEEE. - 1424401895 - 9781424401895 ; , s. 23-30
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Konferensbidrag (refereegranskat)abstract
- Biological growth has been observed on insulators installed all over the world. However, so far, its impact on insulator performance is not well known. This paper summarizes a majority of the work published in the field. Based on the gathered experiences, it can be concluded that microbiological growth is unlikely to cause severe degradation of the rubber housings of non-ceramic insulators. Furthermore, it seems that the impact of growth on the insulator performance is rather low. Techniques available for detection and characterisation of growth on insulators are also described and discusses. Among those, laser-induced fluorescence (LIF) spectroscopy has been found to give good results in remote detection of micro-organisms.
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| 25. |
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| 26. |
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| 27. |
- Gustavsson, T. G., et al.
(författare)
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Aging of silicone rubber under ac or dc voltages in a coastal environment
- 2001
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Ingår i: IEEE transactions on dielectrics and electrical insulation. - : Institute of Electrical and Electronics Engineers (IEEE). - 1070-9878 .- 1558-4135. ; 8:6, s. 1029-1039
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Tidskriftsartikel (refereegranskat)abstract
- Material samples of silicone rubber with known differences in their composition, i.e. different filler content and extra silicone oil added, have been aged at the Anneberg field station on the west coast of Sweden. ac or dc voltage supplied to cylindrical samples at stress levels of 50 or 100 V/mm. The work includes laboratory examination of material changes together with on-site, visual observations and leakage current measurements. Material samplings for the laboratory tests were made after 18 months of electrical aging, which went on for one more year in order to gather further information on the long-term electrical performance of the material. The dominant aging factor was the level of the applied stress, independent of ac or dc voltage. The dc stressed samples showed a higher leakage current and exhibited larger surface degradation compared with samples exposed to ac voltage. The material parameter, an addition of extra silicone oil, initially lead to an increase in adhesion of pollutants, whereas the overall performance was improved by the higher suppression of the leakage current related to oligomer diffusion. Samples with lower level of alumina trihydrate (ATH) exhibited a delayed onset of degradation, but once damaged they degraded more rapidly than the specimens with a higher ATH content. Infrared spectroscopy showed that the ATH was completely consumed at the eroded surface regions. The aging of the surfaces was further assessed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The low molar mass siloxanes present in the pollution layer were extracted and analyzed by size exclusion chromatography and gas chromatography-mass spectroscopy. The results indicated that the main degradation factor was thermal depolymerization activated by electrical discharges. Oxidative crosslinking of the silicone rubber, usually attributed to surface close corona discharges, appeared to have played a minor role.
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| 33. |
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| 34. |
- Pallon, L. K. H., et al.
(författare)
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The impact of MgO nanoparticle interface in ultra-insulating polyethylene nanocomposites for high voltage DC cables
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:22, s. 8590-8601
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Tidskriftsartikel (refereegranskat)abstract
- Low density polyethylene (LDPE) nanocomposites with a reduced conductivity of two orders of magnitude are reported as a novel insulation material for high voltage distribution of renewable energy. The key to the high insulation capacity was to provide 70 nm hexagonal MgO nanoparticles with relatively tong, preferably 18 units long, hydrocarbon functional silsesquioxane coatings. This rendered the surface of the particles completely hydrophobic and also served as a protective layer against adsorption of polar low molecular weight atmospheric substances (H2O and CO2). The elimination of trace amounts of water, in combination with the provided carbon functionality, dramatically improved the dispersion of MgO nanoparticles. The lowest volume conductivity was ca. 7 x 10(-16) s m(-1) for 3 wt% surface coated nanoparticles. Extensive electron microscopy characterization was further used to relate the measured volume conductivity, acquired under conditions that resemble 800 kV high voltage direct current (HVDC) cables, to the distribution of the nanoparticles in the polymer matrix. The results show that an appropriate surface-modification approach yielded uniformly dispersed MgO nanoparticles up to contents as high as 9 wt%, with maintained 10-100 times reduced volume conductivity. Simulations of the MgO nanoparticles distribution revealed that the required interaction radius of the MgO-phase was 775 nm, setting a lower limit of particle amount to effectively work as electrical insulation promoters. The reduced volume conductivity values and scalable processing chemistry reported allow for the production of the next generation insulation material for HVDC cables.
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| 35. |
- Pallon, Love K. H., et al.
(författare)
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Three-Dimensional Nanometer Features of Direct Current Electrical Trees in Low-Density Polyethylene
- 2017
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 17:3, s. 1402-1408
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Tidskriftsartikel (refereegranskat)abstract
- Electrical trees are one reason for the breakdown of insulating materials in electrical power systems. An understanding of the growth of electrical trees plays a crucial role in the development of reliable high voltage direct current (HVDC) power grid systems with transmission voltages up to 1 MV. A section that contained an electrical tree in low-density polyethylene (LDPE) has been visualized in three dimensions (3D) with a resolution of 92 nm by X-ray ptychographic tomography. The 3D imaging revealed prechannel-formations with a lower density with the width of a couple of hundred nanometers formed around the main branch of the electrical tree. The prechannel structures were partially connected with the main tree via paths through material with a lower density, proving that the tree had grown in a step-by-step manner via the prestep structures formed in front of the main channels. All the prechannel structures had a size well below the limit of the Paschen law and were thus not formed by partial discharges. Instead, it is suggested that the prechannel structures were formed by electro-mechanical stress and impact ionization, where the former was confirmed by simulations to be a potential explanation with electro-mechanical stress tensors being almost of the same order of magnitude as the short-term modulus of low-density polyethylene.
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| 39. |
- Zelalem Desta, Berhanu, et al.
(författare)
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Analyses of unexplained faults in transmission lines in the power grid of Ethiopia
- 2024
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Ingår i: Electric Power Systems Research. - 0378-7796. ; 231
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Tidskriftsartikel (refereegranskat)abstract
- Ethiopian power transmission lines operating at 132 kV, 230 kV and 400 kV are encountering unacceptably high number of unexplained outages caused by external factors, which compromise the reliability of the system. It is therefore crucial to examine the characteristics and underlying causes of these outages through analyses of long- term records of the faults for identifying their probable causes for best targeting future mitigation measures. A method is presented to identify, in retrospect, the major possible root causes of unexplained outages that combines information on fault time-of-the day and time-of-the year records with flashover characteristic of known fault causes and local climactic and environmental information. The analyses are based on data covering an 8-year period from 2015 to 2022. A total of 8891 fault records were compiled and among them 4231 faults (47 %) were unexplained faults. Results show statistical variations in the frequency of unexplained faults with respect to spaciotemporal occurrence of the faults, voltage level and local climate. Moreover, the analyses indicate that out of the total number of 4231 unexplained faults, 787 faults could be attributed to lightning (19 %), 1135 faults to pollution events (27 %), 479 were fire related (11 %) and 1830 faults caused by external interferences (43 %).
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| 40. |
- Zelalem Desta, Berhanu, et al.
(författare)
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Investigation on Pollution-Induced Flashovers of In-Service Insulators in Ethiopian Power Transmission Lines
- 2024
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Ingår i: Energies. - 1996-1073 .- 1996-1073. ; 17:9
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Tidskriftsartikel (refereegranskat)abstract
- Power transmission lines in Ethiopia are experiencing an alarmingly high frequency of unexplained outages triggered by environmental factors, which significantly undermine the reliability of the country’s power system. This paper presents investigations aiming to identify those among the unexplained fault records that have been caused by pollution induced flashovers. An identification method is developed, which associates the contextual fault features, such as information about the characteristics of the fault, fault location, and time of day, as well as month of its occurrence with local meteorological/climatic and environmental conditions. A total number of 4231 unexplained faults, recorded between 2015 and 2022, were analyzed. Among them, 1045 faults (24.7%) were identified as being most likely caused by pollution induced flashovers. The entire network suffered from more than 130 pollution-induced flashovers annually with a frequency of about 0.8 faults/100 km/year. The fault frequency strongly differed among the grid regions, being highest in the Northeast and lowest in the Southwest region. Moreover, the performed analyses also concentrated on the evaluation of the pollution performance of various insulator types employed in the network. The results indicate that porcelain insulators have the highest pollution-induced flashover intensity of 1.47 faults/year/1000 units, followed by silicone rubber polymeric composite insulators and glass insulators with the respective intensities of 1.21 and 0.83 faults/year/1000 units. These results indicate that despite the high expectations towards the pollution performance of silicone rubber polymeric insulators, their use in the Ethiopian climatic and environmental conditions appears to be unsatisfactory.
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| 41. |
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