Kapacitet i faktor dielektričkih gubitaka transformatorskih provodnika

doctoral thesis

• Title (english): Capacitance and dielectric dissipation factor of transformers bushings
• Author: Antun Mikulecky
• Mentor: Josip Butorac (mentor)
• Committee member: Zlatko Maljković (član povjerenstva)
• Committee member: Josip Butorac (član povjerenstva)
• Committee member: Zdenko Godec (član povjerenstva)
• Committee member: Mladen Boršić (član povjerenstva)
• Committee member: Ivo Uglešić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Electrical Engineering Fundamentals and Measurements); Zagreb
• Defense date and country: 2006-10-30, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering; Electromechanical Engineering
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

U radu su istražene mogućnosti poboljšanja dijagnostike transformatorskih provodnika od uljem impregniranog papira mjerenjem kapaciteta C i faktora dielektričkih gubitaka tand. Istraživanja C i tand provedena su na provodnicima iz pogona i na posebno izrađenim modelima u rasponima ovlaženosti izolacije od 0,1 % do 3,3 % i temperatura od –15 oC do 120 oC. Modeli su podvrgnuti umjetnom starenju u ukupnom trajanju od 3556 sati na 120 oC. Utvrđeno je da ovlaženost ima izrazit utjecaj na temperaturnu ovisnost C i tand, te brzinu starenja izolacije. Na temelju tand na višim temperaturama moguće je razlučiti ovlaženost od ostarjelosti izolacije. Temperaturna ovisnost tand sedlastog je oblika, pri čemu se, s porastom ovlaženosti i trajanja starenja minimum vrijednosti pomiče prema nižim temperaturama. Pronađene su funkcije aproksimacije rezultata mjerenja tand u cijelom rasponu istraživanih veličina. Procijenjene su i mjerne nesigurnosti ključnih veličina pri donošenju pouzdanih dijagnostičkih odluka. Predloženi su novi kriteriji za dijagnostiku stanja provodnika prema promjeni kapaciteta, koji razlučuju normalne promjene, promjene zbog proboja obloga i promjene zbog prekomjerne ovlaženosti i ostarjelosti izolacije. Također su predloženi novi kriteriji za dijagnostiku stanja provodnika prema promjeni tand tijekom pogona, i to za slučaj kada je tand novog provodnika poznat, te kada on nije poznat.

Abstract (english)

The possibilities of improving diagnostic methods of oil impregnated paper transformer bushings by the measurement of capacitance C and dielectric dissipation factor tand are investigated in this thesis. The investigation of C and tand were implemented on bushings in service as well as on specially constructed models with content of moisture ranging from 0.1 % to 3.3 % and temperature range from –15 oC to 120 oC. The models were exposed to artificial ageing with the total duration of 3556 hours at 120 oC. It has been concluded that the moisture content has a significant influence on the temperature dependence of C and tand and ageing rate of the insulation. Based on tand at higher temperatures it is possible to distinguish between the moisture content and the insulation ageing. The temperature dependence of tand is saddle-shaped, where the minimum values, with increase of moisture content and the duration of ageing, move toward lower temperatures. Functions have been found that approximate the results of tand measurements in the entire range of the investigated values. The measurement uncertainties of crucial values were estimated, which contributes to the making of reliable diagnostic decisions. New criteria are proposed for diagnostics of bushing condition by capacitance changes, which distinguish normal changes, changes due to grading layers puncture and changes due to excess of moisture and insulation ageing. New criteria for diagnostics of bushing condition by changes in tand in service are proposed as well, for the case when tand of a new bushing is known as well as when it is unknown.

• Keywords: provodnik; kapacitet; faktor dielektrièkih gubitaka; energetski; transformator; kvar; model; termièko starenje izolacije; mjerna nesigurnost; dijagnostika; motrenje
• Keywords (english): bushing; capacitance; dielectric dissipation factor; power transformer; failure; model; insulation thermal ageing; measurement uncertainty; of line diagnostics; on line diagnostics
• Language: croatian
• URN:NBN: urn:nbn:hr:168:400746
• Study programme: Title: Doctoral study programme "Electrical Engineering and Computing"; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, po-dručje tehničkih znanosti (doktor/doktorica znanosti, po-dručje tehničkih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2019-07-11 12:11:52