Numerički proračun zagrijavanja trofazno oklopljenog generatorskog voda : magistarski rad - Gorenc, Dalibor; Haznadar, Zijad (Zagreb : D. Gorenc ; Fakultet elektrotehnike i računarstva, 2007)
U radu su prikazane teoretske osnove za proraĉun elektromagnetskog polja, gubitaka i prijenosa topline u trofazno oklopljenim vodovima kod nazivne struje. Na primjeru fazno pregraĊenog generatorskog voda, metodom konaĉnih elemenata, izvršen je proraĉun raspodjele elektromagnetskog polja i gubitaka, na 2D modelu. Gubici u vodiĉu i plaštu izraĉunati na ovaj naĉin, osnova su za analitiĉki i numeriĉki proraĉun zagrijanja. Metodom toplinske mreţe, analitiĉki su izraĉunate nadtemperature vodiĉa, plašta i zraka unutar plašta u stacionarnom stanju. Proraĉun raspodjele temperatura proveden je zatim metodom konaĉnih elemenata, na 2D modelu, uzimajući u obzir sva tri naĉina prijenosa topline: voĊenje, konvekciju i zraĉenje. Pritom je pretpostavljeno da su gubici jednoliko raspodijeljeni po presjeku vodiĉa odnosno plašta. Kako bi se obuhvatio prijenos topline konvekcijom, u zraku unutar plašta, rješavane su simultano s jednadţbom za provoĊenje topline i jednadţbe za dinamiku fluida. Prijenos topline konvekcijom na vanjskoj površini plašta obuhvaćen je empirijskim formulama. Rezultati analitiĉkog i numeriĉkog proraĉuna usporeĊeni su s rezultatima mjerenja na ispitnom modelu. Zbog velikog broja pojednostavljenja, rezultati analitiĉkog proraĉuna slabo se podudaraju s rezultatima mjerenja. S druge strane, rezultati numeriĉkog proraĉuna vrlo dobro se podudaraju s rezultatima mjerenja. Stoga je zakljuĉeno da se prikazani numeriĉki pristup moţe primjenjivati u postupku dimenzioniranja trofazno oklopljenih vodova.
Ključne riječi:
trofazno oklopljeni vod, fazni vodič, oklop (plašt), nadtemperatura (zagrijanje), vođenje topline, prijenos topline konvekcijom, prijenos topline zračenjem, dinamika fluida, metoda toplinske mreže, metoda konačnih elemenata
The thesis presents theoretical background for calculation of the electromagnetic field, losses and heat transfer in 3-phase metal-enclosed busbars at rated current. On the example of a segregated generator phase bus, the distribution of electromagnetic field and losses was computed on a 2D model using the finite element method. The losses in conductors and enclosure calculated in this way were the basis for analytical and numerical calculations of temperature rise. Thermal network method was used for analytical calculation of steady-state temperature rises in conductors, the enclosure and the air in the enclosure. Temperature distribution on a 2D model was computed using the finite element method, taking into account all the three modes of heat transfer: heat conduction, convective and radiative heat transfer. In these computations it was assumed that the losses had uniform distribution along the cross sections of conductors and the enclosure. To take into account the convective heat transfer in air in the enclosure, the heat equation and the fluid dynamics equations were coupled and solved simultaneously. Convective heat transfer from outer surface of the enclosure was described using empirical relations. The results of analytical and numerical calculations are compared with measurement results obtained on a test model. Due to large number of simplifications, the results of analytical calculation are in poor agreement with measurement results. On the other hand, the results of numerical calculation are in very good agreement with measurement results. It is concluded that the presented numerical procedure can be applied to the design of 3-phase metal enclosed busbars.
Keywords:
3-phase metal-enclosed bus, phase conductor, enclosure, temperature-rise, heat conduction, convective heat transfer, radiative heat transfer, fluid dynamics, thermal network method, finite element method
Bibliografija str. 110-112.