Gunnar Berg-Karlsen
Research Scientist
Gunnar Berg-Karlsen
Research Scientist
Publications and responsibilities
Partial Discharge Characterisation of Stator Windings Taken from a 50-year-old Norwegian Hydrogenerator
This paper presents results from laboratory measurements of partial discharge (PD) activity in stator bars taken from a 95 MVA hydrogenerator after 52 years in service. The generator has previously been subjected to off-line condition monitoring including partial discharge (PD) testing at both...
Comparison of Offline VLF PD Measurements and Online PD Measurements on a 50-Year-Old Hydrogenerator Stator in Norway
Stator winding insulation is the part of the hydrogenerator experiencing the highest number and the most damaging failures. Partial discharge (PD) measurement, both offline and online, are commonly used for condition assessment and monitoring of electrical machines. The main concern of using very...
Tilstandskontroll av krafttransformatorer - feildeteksjon og diagnosemetoder
A novel bench size model coalescer: Dehydration efficiency of AC fields on water-in-crude-oil emulsions
We describe herein the design of a small AC electrostatic model coalescer for investigating coalescence efficiency of water in oil emulsions. The function of the model coalescer is tested on emulsions with different water cuts. In the coalescer, coalescence takes place in a couette flow in the bulk...
Experimental study of electrocoalescence of water drops in crude oil using near-infrared camera
Results are presented concerning the influence of an applied electric field on the coalescence of a water droplet with a much bigger water drop, both drops being immersed in a crude oil. This original study of electrocoalescence in crude oil was performed through high-speed optical observations...
Dielectric Properties of Asphaltene Solutions: Solvency Effect on Conductivity
Electrical demulsification is considered an elegant method to enhance the separation of water-in-crude-oil emulsions. Understanding the mechanisms involved during this process remains a challenge for the further development of this separation method. The aim of this study is to elucidate the...
The effect of hydrostatic pressure on electrical treeing in silicone cable joints
The purpose of this work was to study the effect of hydrostatic pressure on the initiation and growth of electrical trees in a silicone insulation material for electrical apparatus. In this study a commercial available light transparent silicone material was subjected to a hydrostatic pressure in...
Design of a High Voltage Penetrator for High Pressure and Temperature Laboratory Testing
High voltage apparatus and reliable power supply are of vital importance for subsea processing. The purpose of this work has been to develop a small high voltage penetrator for use with high pressure vessels in the laboratory. Such equipment can facilitate high voltage and current testing of models...