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Dag Linhjell

Research Scientist

Dag Linhjell

Research Scientist

Dag Linhjell
Phone: 930 04 739
Email:
Department: Electric Power Technology
Office: Trondheim

Publications and responsibilities

Publication
https://www.sintef.no/en/publications/publication/1816551/

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 streamers, higher breakdown voltage, reduced background current, reduced...

Authors Dag Linhjell Lars Lundgaard M. Unge Olof Hjortstam
Year 2020
Type Academic article
Publication
https://www.sintef.no/en/publications/publication/1807150/

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 pre-breakdown streamer modes have been studied for a selection of model liquids...

Authors Lars Lundgaard Dag Linhjell Øystein Hestad Michael Unge Olof Hjortstam
Year 2020
Type Academic article
Publication
https://www.sintef.no/en/publications/publication/1807148/

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 vary, as new brands arrive in the market, and existing standards are unsuited for...

Authors Dag Linhjell Lars Lundgaard Michael Unge Olof Hjortstam
Year 2020
Type Academic article
Publication
https://www.sintef.no/en/publications/publication/1717940/

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. As has previously been found in short gap experiments of 1 – 7 mm in various...

Authors Dag Linhjell Lars Lundgaard Mikael Unge
Year 2019
Type Academic chapter/article/Conference paper
Publication
https://www.sintef.no/en/publications/publication/1526026/

Third mode streamers have been studied in the mineral oil Nytro 10 XN, gas-to-liquid oil Diala S4 ZX-1 and the high viscosity white oil Primol 352, in an 80 mm point-plane gap under step impulse voltage. Third mode streamer velocities were in the range 4–60 km/s. The "acceleration" of the average...

Authors Dag Linhjell Lars Lundgaard Mikael Unge
Year 2017
Type Academic chapter/article/Conference paper
Publication
https://www.sintef.no/en/publications/publication/1526028/

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 streamer inception in n-pentane with a positive needle polarity. The measured...

Authors Øystein Hestad Dag Linhjell Lars Lundgaard Jarl Ø. Samseth Mikael Unge
Year 2017
Type Academic chapter/article/Conference paper
Publication
https://www.sintef.no/en/publications/publication/1526050/

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 load, temperature, solid and liquid insulation aging, as well as marker stability...

Authors Knut Brede Liland Dag Linhjell Cedric Lesaint Marit-Helen Glomm Ese Lars Lundgaard Pascal Mavrommatis Nenad Miroljub Stjepanovic
Year 2017
Type Academic chapter/article/Conference paper
Publication
https://www.sintef.no/en/publications/publication/1385663/

For introducing power converters at ambient pressure at large sea depths, dielectric liquids are proposed as insulation for power electronic converters. This paper presents statistical analysis of short time tests of partial discharge and breakdown voltage on the trench between metallized edges of...

Authors Abdelghaffar Amoka Abdelmalik Malin Drevdal Borge Arne Nysveen Lars Lundgaard Dag Linhjell
Year 2016
Type Academic article
Publication
https://www.sintef.no/en/publications/publication/1060702/

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 projects on laboratory studies on ageing of mineral oil impregnated cellulose...

Authors Lars Lundgaard Knut Brede Liland Dag Linhjell Dejan Susa Marit-Helen Glomm Ese Cecilie Mørk Selsbak M Kes Cedric Lesaint
Year 2015
Type Report
Publication
https://www.sintef.no/en/publications/publication/1162813/

Molecular additives i.e. additives with specific molelcular propertie, has been shown to influence breakdown properties of dielectric liquids, in particular lightning impulse characteristics. In this study we investigate the propagation of streamers in a natural ester liquid with and without...

Authors M. Unge S Singha Stian Ingebrigtsen Dag Linhjell Lars Lundgaard
Year 2014
Type Academic chapter/article/Conference paper