Raspodela vlage i degradacija izolacionog sistema energetskih transformatora sa mineralnim biljnim uljem
Distribution of water and degradation processes of insulation system of power transformers filled with mineral oil and natural ester oil
Докторанд
Vasović, Valentina Z.Ментор
Orlović, AleksandarЧланови комисије
Glišić, SandraLukić, Ivana
Radaković, Zoran
Lukić, Jelena M.
Метаподаци
Приказ свих података о дисертацијиСажетак
Predmet istraţivanja ove doktorske disertacije je raspodela vlage i degradacija
izolacionog sistema energetskih transformatora ĉiji su bakarni provodnici izolovani Kraft
papirom i izolacionim uljem mineralnog, odnosno biljnog porekla. Izolacioni sistem uljem
punjenih energetskih transformatora saĉinjen je od izolacionih ulja i ĉvrste izolacije na bazi
celuloze. Najvaţniji deo izolacije predstavlja izolacioni papir oko bakarnih provodnika i
smatra se da je transformator dostigao kraj svoj ţivotnog veka onda kada je papir degradirao
u tolikoj meri da je izgubio mehaniĉku ĉvrstinu i sposobnost da podnese dalja elektriĉna, a
posebno mehaniĉka naprezanja Kao jedna od mera degradacije papira, odnosno mera
mehaniĉke ĉvrstoće, uzima se vrednost stepena polimerizacije papira (DP). Ovaj parametar
se moţe odrediti tek nakon što transformator završi svoj radni vek, tako da je tokom pogona
transformatora moguće vršiti samo indirektne procene stepena degradacije papirne izolacije.
Jedan od naĉina za... procenu stanja papirne izolacije jeste odreĊivanjem sadrţaja derivata
furana u ulju koji nastaju prilikom degradacije papirne izolacije uz korišćenje odgovarajućih
korelacionih jednaĉina. Korelacione jednaĉine koje su trenutno dostupne u literaturi ne
uvaţavaju parametre koji utiĉu na rastvorljivost derivata furana iz papira u ulje kao što je
prisustvo vlage i kiselina u izolacionom sistemu.
Istraţivaĉki rad bio je organizovan u dva dela. Prvi deo istraţivanja obuhvatao je prouĉavanje
fenomena raspodele vlage izmeĊu papirne izolacije i izolacionog ulja mineralnog i biljnog
porekla. 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 dijagrama
u odrţavanju realnih energetskih transformatora ostvarena je poreĊenjem rezultata procene
sadrţaja vlage u celuloznoj izolaciji kod 23 realna energetska transformatora dobijenih na
dva naĉina: primenom elektriĉne metode FDS i primenom predmetnih dijagrama uz
korišćenje izmerenih sadrţaja vode u ulju i radne temperature ulja. U okviru istraţivanja
fenomena raspodele vlage utvrĊeno je da u sluĉaju biljnih izolacionih ulja postoji nejednaka
raspodela vlage izmeĊu papira i presborda, naroĉito na umerenim temperaturama i za niţe
sadrţaje vlage, što moţe biti veoma korisno prilikom procene ovlaţenosti izolacionog
sistema realnih energetskih transformatora punjenih uljem biljnog porekla...
Scope of this phd research was investigation of moisture distribution and ageing
phenomena of the insulation system of power transformers with kraft paper insulated copper
conductors and filled with mineral or natural ester oil. The insulation system of oil-filled
power transformers is composed of insulating oils and cellulose-based solid insulation. The
most important part of the insulation is the insulating paper wrapped around copper
conductors. Transformer is considered to have reached the end of its life when the paper have
lost it‘s mechanical strength and ability to withstand further electrical and mechanical
stresses due to degradation. A common way to express the condition of paper insulation in
transformers, ie mechanical strength of paper, is the degree of polymerization (DP). This
parameter can be determined only after the transformer has completed its service life. During
the operation of the transformer it is only possible to make estimation of DP based on furan
derivativ...es content in the oil, compounds produced during paper ageing, using appropriate
correlation equations. The correlation equations currently available in the literature do not
take into account parameters that affect the solubility of furan derivatives in oil, such as the
presence of moisture and acids.
Research was orriented in two areas. First area had covered investigation of moisture
distribution phenomena between paper and oil, mineral and natural ester. Based on
experimentally data moisture equilibrium charts for kraft paper and pressboard insulation and
mineral and natural ester oil were developed, for temperature range 40 ° C – 120 ° C and
moisture content in insulation 0.5% - 5%. A comparative analysis of estimated moisture
contents in the cellulose insulation using measurements of water content in the oil and
equilibrium curves, and moisture contents obtained by applying electrical frequency
dependent spectroscopic method (FDS) are provided for 23 transformers in service. A good
agreement of these results confirmed applicability of these charts for assesing the water
content in solid insulation of power transformers in service.
Due to the higher solubility of moisture in natural ester compared to in mineral oil, water
equilibrium in a system of natural ester oil, paper and pressboard was moved to the oil. In the
system of naural ester oil uneven distribution of water between paper and pressboard was also
observed, especially for moderate initial water contents and moderate temperatures. This fact
could be very useful in assessing the moisture content in paper in power transformers filled
with natural ester oil...