Blar i NTNU Open på forfatter "Ildstad, Erling"
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Longitudinal AC Breakdown Voltage of XLPE-XLPE Interfaces Considering Surface Roughness and Pressure
Kantar, Emre; Hvidsten, Sverre; Mauseth, Frank; Ildstad, Erling (Journal article; Peer reviewed, 2017)The interfacial breakdown between two dielectric surfaces has been reported to represent one of the principal causes of failure for power cable joints and connectors; thus, a better understanding of interfacial breakdown ... -
Longitudinal AC Electrical Breakdown Strength of Polymer Interfaces: Experimental and theoretical examination of solid-solid interfaces considering elasticity, surface roughness, and contact pressure
Kantar, Emre (Doctoral theses at NTNU;2019:93, Doctoral thesis, 2019)All electrical insulation systems consist of a combination of different insulating and conductive materials. The alternating current (AC) breakdown strength (BDS) of insulation systems is limited by the lowest BDS of either ... -
Modelling and Characterization of Partial Discharge Activity versus Applied Voltage, Test Frequency and Temperature
Ildstad, Erling; Aakre, Torstein Grav (Chapter, 2022)Measurements of partial discharges (PDs) are commonly used as diagnostic indicators for assessing the quality of high voltage equipment. In many cases, such PD measurements are of practical reasons either performed at ... -
On the Tangential AC Breakdown Strength of Polymer Interfaces Considering Elastic Modulus
Kantar, Emre; Mauseth, Frank; Ildstad, Erling; Hvidsten, Sverre (Chapter, 2017)The interfacial breakdown between two dielectric surfaces was reported to represent one of the leading causes of failure for power cable joints and connectors, in which elastic modulus of the dielectric material plays a ... -
Partial Discharge Inception Voltage of Voids Enclosed in Epoxy/Mica versus Voltage Frequency and Temperature
Aakre, Torstein Grav; Ildstad, Erling; Hvidsten, Sverre (Journal article; Peer reviewed, 2020)Detection of partial discharges (PDs) is widely used as a condition assessment tool for high voltage equipment. Application of low frequency test voltage is often preferred in the case of test objects with a large capacitance. ... -
Partial Discharge Measurements for Studying Cavities in Mass Impregnated Cables
Helle Jørgensen, Bjørn (Master thesis, 2012)A hypothesis regarding temperature dependant discharge levels was the starting grounds for this student work. Based on calculations and conversations with experienced people in this field, there should be cavity-induced ... -
Partielle utladningar og elektrisk trevekst i kryssbunden polyetylen og polypropylen isolasjon
Lunde, Ingeborg (Master thesis, 2012)Kryssbunden polyetylen (PEX) er den mest brukte polymerisolasjonen i Noreg. PEX blir brukt i kablar opp til 420 kV. Auka spenningsnivå i høgspenningskablar gjev auka termiske påkjenningar og PEX kablar har ein maksimal ... -
PD-Activity in Generator Stator Bar insulation versus Voltage Frequency and Temperature
Aakre, Torstein Grav; Ildstad, Erling (Chapter, 2020)Condition assessment of generators is today performed at various voltage frequencies and test temperatures. The main purpose of this paper is to compare measured PD results from sections of generator bars with that of ... -
Polarisasjon og Elektrisk ledningsevne i HVDC masse- og PEX isolerte kabler som funksjon av spenning og temperatur.
Alstad, Jonas (Master thesis, 2012)Formålet med masteroppgaven har vært å studere opp og utladninger knyttet til ulike HVDC kabel isolasjonsmaterialer. Eksperimentelle forsøk ble gjennomført for å beskrive disse fenomene for en 450 kV HVDC massekabel, og ... -
Polarisasjon og Elektrisk ledningsevne i HVDC massekabler som funksjon av spenning og temperatur
Fremmegaard, Esten Øyen (Master thesis, 2011)I denne masteroppgaven undersøkes det hvordan polarisasjonsfenomenet og DC ledningsevnen påvirkes av ulike faktorer. Det legges spesiell vekt på å vise hvordan temperatur, tid og spenning påvirker disse fenomenene. Resultatene ... -
Review of Partial Discharge and Dielectric Loss Tests for Hydropower Generator Bars
Aakre, Torstein Grav; Ildstad, Erling; Hvidsten, Sverre; Nysveen, Arne (Journal article; Peer reviewed, 2017)Condition assessment of hydropower generators is important to ensure high serviceability of power stations. Many of the in-service generators are old and current load operation schemes demands more than the design load, ... -
Sammenligning av målte og beregnede temperaturer langs strømbelastede Oslofjord kabler
Andersen, Trine Singelstad (Master thesis, 2017)En viktig aldringsmekanisme i strømkabler er høye driftstemperaturer, da dette kan påvirke kvaliteten på isolasjonen. Det er derfor viktig å overvåke temperaturene i kablene. For bedre utnyttelse av kabelanleggene er det ... -
Steady-State Electric Field and Conductivity in Mass-Impregnated HVDC Cable Insulation
Håkonseth, Gunnar; Ildstad, Erling (Chapter, 2018)This paper presents results from measurements and calculations of the steady-state DC electric field and the field-dependent conductivity in the two insulation materials found in mass-impregnated HVDC cables: Cable mass ... -
Structure of Paper-Oil Insulation for Mass-Impregnated HVDC Cables
Håkonseth, Gunnar; Furuheim, K. M.; Ildstad, Erling (Chapter, 2019)The electrical insulation in mass-impregnated high voltage direct current (HVDC) cables consists of many layers of paper tapes that are wound helically around the conductor and subsequently impregnated in oil. The oil fills ... -
Tangential AC Breakdown Strength of Solid-Solid Interfaces Considering Surface Roughness
Kantar, Emre; Mauseth, Frank; Ildstad, Erling; Hvidsten, Sverre (Chapter, 2017)The primary purpose of this paper is to study the influence of the surface roughness and interfacial pressure on the tangential AC breakdown strength (BDS) of solid-solid interfaces experimentally. Three-dimensional surface ... -
Tangential Electric Breakdown Strength and PD Inception Voltage of Solid-Solid Interface
Hasheminezhad, Seyed Majid (Doctoral theses at NTNU;2016:329, Doctoral thesis, 2016)The solid-solid interface is one of the critical region of the electrical insulation systems which consist of a combination of different insulating materials. It is predicted that the microscopic air-filled voids formed ... -
The effect of DC superimposed AC Voltage on Partial Discharges in Dielectric Bounded Cavities
Olsen, Pål Keim; Mauseth, Frank; Ildstad, Erling (Chapter, 2014)Voltage source converters is used in HVDC stations in offshore HVDC transmission systems, between the AC and DC power grid. The AC ripple voltage on the DC side of the HVDC stations can be in the range of 1-10 % of the ... -
Tidsdomene dielektrisk respons for tilstandskontroll av statorviklinger fra driftsaldret vannkraftgenerator
Brodin, Nikolai (Master thesis, 2022)Flertallet av generatorer i norske vannkraftverk har allerede passert forventet levetid. For å undersøke om generatorene fortsatt kan benyttes etter endt forventet levetid, kan de analyseres og diagnostiseres. Feilene som ... -
Time Development of Voltage Frequency Dependence of Partial Discharge Activity in Voids
Aakre, Torstein Grav; Ildstad, Erling; Hvidsten, Sverre (Journal article; Peer reviewed, 2019)Condition assessment of high voltage equipment based on partial discharge measurements is often performed after a voltage pre-conditioning period. The aim of this paper is to present results from experimental examinations ... -
Time-Dependent Electric Field Distribution in Layered Paper-Oil Insulation
Håkonseth, Gunnar; Ildstad, Erling (Journal article; Peer reviewed, 2019)Layered paper–oil insulation is used in several types of HVDC equipment. In order to better understand breakdown mechanisms and optimize the design, it is important to understand the electric field distribution in the ...