Power transformer magnetization under GIC/GMD

Simple item page
dc.contributor.authorLu, Shuen
dc.contributor.committeechairLiu, Yiluen
dc.contributor.committeememberPhadke, Arun G.en
dc.contributor.committeememberBesieris, Ioannis M.en
dc.contributor.committeememberDe La Ree, Jaimeen
dc.contributor.committeememberJohnson, Lee W.en
dc.contributor.departmentElectrical Engineeringen
dc.date.accessioned2014-03-14T21:19:14Zen
dc.date.adate2008-09-23en
dc.date.available2014-03-14T21:19:14Zen
dc.date.issued1994-03-05en
dc.date.rdate2008-09-23en
dc.date.sdate2008-09-23en
dc.description.abstractGeomagnetically induced currents (GIC) could saturate a transformer core. Two significant effects are the abnormal stray flux in transformers and extremely large harmonic contents in excitation currents, which can lead to serious equipment damage and power system misoperation. Such incidents have occurred during the March 1989 K-9 solar magnetic disturbance. This dissertation starts with a systematically study of transformer magnetization under GIC. It reviews both dc and ac saturation patterns of five transformer core designs. Magnetic fields along various traverses for dc excitation are presented. Impedance matrix entries of a single phase transformer are compared for normal and dc operations. New observations have been formed based on the simulation results. The study helps to reveal the fundamental transformer magnetization mechanism under GIC in order to assess potential stray flux heating possibilities of geologically vulnerable transformer units. Based on the finite element analysis, an improved method of modeling transformer excitation under dc bias using equivalent magnetic circuit is developed. There are two unique points in this approach: first, information of 3D finite element magnetic flux distribution analysis is used to construct and verify the circuit model; second, the effect of the transformer tank: is included The model is capable of simulating transformer excitation currents under different levels of dc bias with good accuracy. As a consequence, the complete variations of excitation current harmonics with respect to an extended range of dc bias are revealed. The sensitivity of transformer winding impedances and core loss on the excitation characteristics are examined. The saturated transformer under no-load and various loading conditions is simulated. A laboratory test is performed on a small scale transformer and compared with the model results. Excitation harmonics generated from dc biased three phase transformer banks with different types of equivalent loads are also simulated The effect of both unbalanced dc excitations and unbalanced loads are investigated The results of this study contribute in understanding transformers as harmonic sources and the impact on power systems during a geomagnetic disturbance.en
dc.description.degreePh. D.en
dc.format.extentxiii, 181 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-09232008-144706en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-09232008-144706/en
dc.identifier.urihttp://hdl.handle.net/10919/39460en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1994.L8.pdfen
dc.relation.isformatofOCLC# 30932783en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1994.L8en
dc.subject.lcshElectric currentsen
dc.subject.lcshElectric transformersen
dc.subject.lcshGeomagnetismen
dc.titlePower transformer magnetization under GIC/GMDen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineElectrical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
LD5655.V856_1994.L8.pdf
Size:
5 MB
Format:
Adobe Portable Document Format
Download

Collections

Doctoral Dissertations