Blar i SINTEF Open på forfatter "Linhjell, Dag"
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Ageing and Restoration of Transformer Windings
Lundgaard, Lars E.; Linhjell, Dag; Hansen, Walter; Anker, Morten Ulrik (SINTEF Energi. Rapport;, Research report, 2001) -
Comparison between synthetic ester and mineral oil impregnated transformer paper aging markers
Liland, Knut Brede; Linhjell, Dag; Lesaint, Cedric Michel; Ese, Marit-Helen Glomm; Lundgaard, Lars Esben; Mavrommatis, Pascal; Stjepanovic, Nenad Miroljub (Proceedings of IEEE International Conference on Dielectric Liquids;, Chapter; Peer reviewed, 2017)For transformers in service, aging markers from cellulose in oil such as furans, water, methanol and acids are measured for diagnostic purposes. The content of these indicators, measured in oil, may therefore vary with ... -
Dynamic moisture diffusion in transformer winding insulation
Linhjell, Dag; Mehammer, Eirill Bachmann (Peer reviewed; Journal article, 2023)Wind power production is intermittent due to varying wind conditions. This leads to frequent temperature changes in the wind farm transformers, which in turn affects the lifetime of the transformer winding insulation. To ... -
Field dependent conductivity of n-pentane
Hestad, Øystein Leif Gurandsrud; Linhjell, Dag; Lundgaard, Lars Esben; Samseth, Jarl Ø.; Unge, Mikael (Proceedings of IEEE International Conference on Dielectric Liquids;2017, Chapter; Peer reviewed, 2017)A sensitive differential charge measurement technique was used to measure the conduction current from a sharp needle in a needle plane geometry in n-pentane. The current was measured at voltages up to the threshold for ... -
Field-dependent molecular ionization and excitation energies: Implications for electrically insulating liquids
Davari, Nazanin; Åstrand, Per-Olof; Unge, Mikael; Lundgaard, Lars Esben; Linhjell, Dag (Journal article; Peer reviewed, 2014) -
Positive third mode streamers in insulating oil
Linhjell, Dag; Lundgaard, Lars; Unge, Mikael (Chapter; Peer reviewed, 2017) -
Pre-breakdown phenomena in hydrocarbon liquids in a point-plane gap under step voltage. Part 2: behaviour under negative polarity and comparison with positive polarity
Lundgaard, Lars Esben; Linhjell, Dag; Hestad, Øystein Leif Gurandsrud; Unge, Michael; Hjortstam, Olof (Journal article; Peer reviewed, 2020)This study addresses the dielectric performance of nonpolar hydrocarbon liquids and mineral oils under negative polarity stress. Stopping length for non-breakdown streamers, breakdown voltages and velocities for various ... -
Prebreakdown phenomena in hydrocarbon liquids in a point-plane gap under step voltage. Part 1: behaviour at positive polarity
Linhjell, Dag; Lundgaard, Lars Esben; Unge, Michael; Hjortstam, Olof (Journal article; Peer reviewed, 2020)This study addresses the dielectric performance of nonpolar hydrocarbon liquids and mineral oils under positive polarity stress. It is of interest to improve knowledge on how functional properties of dielectric liquids ... -
Pressure Dependent Propagation of Positive Streamers in a long Point-Plane Gap in Transformer Oil
Linhjell, Dag; Lundgaard, Lars Esben; Unge, Mikael (Proceedings of IEEE International Conference on Dielectric Liquids;, Chapter; Peer reviewed, 2019)The propagation of positive streamers in a naphtenic transformer oil in an 80 mm point-plane gap has been investigated under an impulse voltage being close to a step voltage and under pressures ranging from 0.1 to 1.7 MPa. ... -
Pressure-Dependent Propagation of Streamers under Step Voltage in a long Point-Plane Gap in Transformer Oil
Linhjell, Dag; Lundgaard, Lars Esben; Unge, M.; Hjortstam, Olof (Peer reviewed; Journal article, 2020)The effect of pressure on positive and negative streamer propagation in a mineral transformer oil is studied in an 80 mm point-plane gap under step voltage. Increased pressure causes reduced stopping length for non-breakdown ... -
Transformer Windings Ageing, diagnosis and asset management. Version 4
Lundgaard, Lars Esben; Liland, Knut Brede; Linhjell, Dag; Susa, Dejan; Ese, Marit-Helen; Selsbak, Cecilie Mørk; Kes, M; Lesaint, Cedric Michel (SINTEF Energi. Rapport;TR A7099, Research report, 2015)This report addresses state of the art in the field of transformer ageing and diagnostics, with emphasis on advising end-users on transformer asset management and on transformer specification. The basis is results from two ...