Title (srp)

Raspodela vlage i degradacija izolacionog sistema energetskih transformatora sa mineralnim biljnim uljem : doktorska disertacija

Author

Vasović, Valentina Z., 1983-

Contributor

Orlović, Aleksandar, 1965-
Glišić, Sandra, 1978-
Lukić, Ivana, 1979-
Radaković, Zoran, 1965-
Lukić, Jelena M., 1970-
Kartalović, Nenad, 1960-

Description (eng)

Scope of this phd research was investigation of moisture distribution and ageingphenomena of the insulation system of power transformers with kraft paper insulated copperconductors and filled with mineral or natural ester oil. The insulation system of oil-filledpower transformers is composed of insulating oils and cellulose-based solid insulation. Themost important part of the insulation is the insulating paper wrapped around copperconductors. Transformer is considered to have reached the end of its life when the paper havelost it‘s mechanical strength and ability to withstand further electrical and mechanicalstresses due to degradation. A common way to express the condition of paper insulation intransformers, ie mechanical strength of paper, is the degree of polymerization (DP). Thisparameter can be determined only after the transformer has completed its service life. Duringthe operation of the transformer it is only possible to make estimation of DP based on furanderivatives content in the oil, compounds produced during paper ageing, using appropriatecorrelation equations. The correlation equations currently available in the literature do nottake into account parameters that affect the solubility of furan derivatives in oil, such as thepresence of moisture and acids.Research was orriented in two areas. First area had covered investigation of moisturedistribution phenomena between paper and oil, mineral and natural ester. Based onexperimentally data moisture equilibrium charts for kraft paper and pressboard insulation andmineral and natural ester oil were developed, for temperature range 40 ° C – 120 ° C andmoisture content in insulation 0.5% - 5%. A comparative analysis of estimated moisturecontents in the cellulose insulation using measurements of water content in the oil andequilibrium curves, and moisture contents obtained by applying electrical frequencydependent spectroscopic method (FDS) are provided for 23 transformers in service. A goodagreement of these results confirmed applicability of these charts for assesing the watercontent in solid insulation of power transformers in service.Due to the higher solubility of moisture in natural ester compared to in mineral oil, waterequilibrium in a system of natural ester oil, paper and pressboard was moved to the oil. In thesystem of naural ester oil uneven distribution of water between paper and pressboard was alsoobserved, especially for moderate initial water contents and moderate temperatures. This factcould be very useful in assessing the moisture content in paper in power transformers filledwith natural ester oil...

Description (srp)

Predmet istraţivanja ove doktorske disertacije je raspodela vlage i degradacijaizolacionog sistema energetskih transformatora ĉiji su bakarni provodnici izolovani Kraftpapirom i izolacionim uljem mineralnog, odnosno biljnog porekla. Izolacioni sistem uljempunjenih energetskih transformatora saĉinjen je od izolacionih ulja i ĉvrste izolacije na baziceluloze. Najvaţniji deo izolacije predstavlja izolacioni papir oko bakarnih provodnika ismatra se da je transformator dostigao kraj svoj ţivotnog veka onda kada je papir degradiraou tolikoj meri da je izgubio mehaniĉku ĉvrstinu i sposobnost da podnese dalja elektriĉna, aposebno mehaniĉka naprezanja Kao jedna od mera degradacije papira, odnosno meramehaniĉke ĉvrstoće, uzima se vrednost stepena polimerizacije papira (DP). Ovaj parametarse moţe odrediti tek nakon što transformator završi svoj radni vek, tako da je tokom pogonatransformatora moguće vršiti samo indirektne procene stepena degradacije papirne izolacije.Jedan od naĉina za procenu stanja papirne izolacije jeste odreĊivanjem sadrţaja derivatafurana u ulju koji nastaju prilikom degradacije papirne izolacije uz korišćenje odgovarajućihkorelacionih jednaĉina. Korelacione jednaĉine koje su trenutno dostupne u literaturi neuvaţavaju parametre koji utiĉu na rastvorljivost derivata furana iz papira u ulje kao što jeprisustvo vlage i kiselina u izolacionom sistemu.Istraţivaĉki rad bio je organizovan u dva dela. Prvi deo istraţivanja obuhvatao je prouĉavanjefenomena raspodele vlage izmeĊu papirne izolacije i izolacionog ulja mineralnog i biljnogporekla. Formirani su ravnoteţni dijagrami raspodele vlage izmeĊu izolacionog Kraft papira,presborda i mineralnog, odnosno biljnog izolacionog ulja, za opseg temperatura 40 °C - 120°C i sadrţaja vlage u izolaciji 0,5% – 5%. Potvrda mogućnosti primene formiranih dijagramau odrţavanju realnih energetskih transformatora ostvarena je poreĊenjem rezultata procenesadrţaja vlage u celuloznoj izolaciji kod 23 realna energetska transformatora dobijenih nadva naĉina: primenom elektriĉne metode FDS i primenom predmetnih dijagrama uzkorišćenje izmerenih sadrţaja vode u ulju i radne temperature ulja. U okviru istraţivanjafenomena raspodele vlage utvrĊeno je da u sluĉaju biljnih izolacionih ulja postoji nejednakaraspodela vlage izmeĊu papira i presborda, naroĉito na umerenim temperaturama i za niţesadrţaje vlage, što moţe biti veoma korisno prilikom procene ovlaţenosti izolacionogsistema realnih energetskih transformatora punjenih uljem biljnog porekla...

Description (srp)

Tehnološko inženjerstvo - Hemijsko inženjerstvo / Tehnološko inženjerstvo- Hemijsko inženjerstvo Datum odbrane: 17.09.2021.

Object languages

Serbian

Date

2021

Rights

Creative Commons License
This work is licensed under a
CC BY-NC-ND 3.0 AT - Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Austria License.

http://creativecommons.org/licenses/by-nc-nd/3.0/at/legalcode

Subject

OSNO - Opšta sistematizacija naučnih oblasti, Hemijsko inženjerstvo

power transformers, paper insulation degradation, natural ester insulation oil, furan derivatives, moisture distribution

Identifiers