Doprinos mehaničkom proračunu sinkronog generatora s istaknutim polovima s obzirom na prijelazna stanja elektroenergetskog sustava

Švigir, Nikola (1999) Doprinos mehaničkom proračunu sinkronog generatora s istaknutim polovima s obzirom na prijelazna stanja elektroenergetskog sustava. = Synchronous generator with salient poles mechanical calculation contribution with regard to power supply transient phenomena. Doctoral thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Stegić, Milenko.

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Abstract (Croatian)

U radu "Doprinos mehaničkom proračunu sinkronog generatora s istaknutim polovima s obzirom na prijelazna stanja elektroenergetskog sustava" istražene su prijelazne pojave u neposrednoj blizini sinkronog generatora koji je priključen na elektroenergetski sustav, a imaju utjecaj na njegovo mehaničko dimenzioniranje. \Naime, zbog važnosti svakog sinkronog generatora, u elektrani, kao elementa u kojem se realizira elektromehanička pretvorba energije nužno je da takav element bude projektiran i izveden s visokim stupnjem pouzdanosti odnosno raspoloživosti i to kako s mehaničkog tako i električkog motrišta. Pri mehaničkom i električkom izračunu sinkronog generatora s istaknutim polovima, uglavnom, se polazi od ne samo stacionarnih stanja pogona već i od prijelaznih stanja koja postavljaju "oštrije" zahtjeve na potrebne izračune i samu izvedbu. Kada je riječ o prijelaznim stanjima analiziraju se, prije svega, kratki spojevi na stezaljkama generatora, nesimetrična opterećenja, tzv. udamo rasterećenje, pogrešna sinkronizacija i primjena tehnike automatskog (tropolnog iii jednopolnog) ponovnog uključenja na dalekovodima preko kojih generator predaje snagu odnosno električnu energiju u elektroenergetski sustav. Raniji pristupi pri izboru "najtežeg" prijelaznog stanja za mehaničko dimenzioniranje sinkronog generatora s istaknutim polovima (dimenzioniranje namota statora, rotora, polova, osovina, Iežajeva i temelja) bili su u svezi s pretpostavkom nastanka tropolnog kratkog spoja na stezaljkama generatora. Međutim, pokazalo se da to nije dovoljno, to da se pri pojavi dvopolnog kratkog spoja u najnepovoljnijem trenutku nastanka (kut između napona na stezaljkama generatora i napona sabirnica na koje je priključen na elektroenergetski sustav iznosi 120°eI.) može pojaviti elektromagnetski moment 1,8 puta veći negoli u slučaju tropolnog kratkog spoja. Iskustva i saznanja o neželjenim posljedicama na nekim sinkronim generatorima u pogonu glede mehaničke otpornosti na stanovita prijelazna stanja u elektroenergetskom sustavu (prije svega uobičajena primjena tehnike automatskog ponovnog uključenja u mreži sustava) ukazala su na potrebu istraživanja pojava u takovom slučaju kao i veličina (elektromagnetski moment, prije svega) koje imaju utjecaj na mehanički izračun generatora. Na konkretnim primjerima sinkronih generatora u HE "Varaždin" i HE "Čakovec" pokazalo se je da se prilikom primjene tehnike tropolnog automatskog uključenja pojavljuju, na generatorima elektromagnetski momenti s vrijednostima većim negoli pri "najtežem" dvopolnom kratkom spoju na njihovim stezaljkama. Upravo pomenuto značilo je i potrebu za istraživanjem prijelaznog stanja prilikom primjene navedene tehnike. Izvorno razvijeno programsko sklopovlje, za analizu pojava prilikom primjene tehnike automatskog ponovnog tropolnog uključenja u elektroenergetskom sustavu, na konkretno istraživanim elektranama pokazalo je svoju, fizikalnu, odnosno teorijsku vjerodostojnost i kao takovo se mote rabiti pri procesu mehaničkog i električkog projektiranja sinkronih generatora s istaknutim polovima. Za pristup mehaničkom izračunu sinkronog generatora s istaknutim polovima primijenjena je tzv. algoritamska i kriterijska logika u smislu, sto je moguće više, upotrebe računala i uzimanja u obzir bitnih kriterija za dozvoljene veličine naprezanja i deformacija, uključivo i dinamičke parametre. Posebna pozornost posvećena je izračunu osovina i stabilnosti mehaničkog hoda generatora gljivaste izvedbe kao i izračunu i dimenzioniranju učvršćenja pola. Glede izračuna osovine došlo se do saznanja da je nužno istraživati torzijski moment na sustav osovina, aksijalnu silu, poprečne site na rotor agregata, to opterećenje osovine vezano uz centrifugalne site vlastitih masa. S obzirom na stabilnost hoda utvrđeni kriteriji su u svezi s kritičnom brzinom koja u jednom slučaju treba biti 1,5 puta veća od brzine pobjega (agregat oslonjen na krute oslonce), a u drugom slučaju treba biti 2,5 puta, veća od nazivne brzine vrtnje (djelovanje jednostrane magnetske sile). Pri izračunu i dimenzioniranju učvršćenja pola postignuta su saznanja za učinkovitu primjenu metoda elastičnosti i fotoelasticimetrije s kojima se dobiva, realniji (praksi bliži) raspored opterećenja odnosno udjela site koju prenose pojedini dijelovi konstrukcije učvršćenja pola.

Abstract

The paper "Synchronous generator with salient poles mechanical calculation contribution with regard to power supply transient phenomena" deals with transient phenomena in the vicinity of the synchronous generator connected to electrical power supply, which influence its mechanical calculations. Since each synchronous generator in a power plant is a very important element trough which electromechanical energy conversion is realized, that element should be designed and produced with a very high degree of reliability and availability from both mechanical and electrical point of view. Mechanical and electrical calculations of a synchronous generator with salient poles take into consideration not only stationary state drives but transient states as well, since their requirements concerning necessary calculations and design are "more strict". When it comes to transient phenomena, it is particularly important to analyse short circuits on generator terminals, unsymmetrical loading, so called shock unloading, faulty synchronization and automatic (three pole or one pole circuit) reclosing on overhead power lines through which a generator "gives" power, i. e. electrical energy into the power supply system. Earlier approaches in choosing "the most difficult" transient phenomena for mechanical calculation of a synchronous generator with salient poles (stator winding, rotor, poles, shafts, bearings and foundation calculation) were related to the supposition of three phase fault on generator terminals. However, it has not proved to be sufficient. When a phase to phase fault occurs in the most inconvenient moment (the angle between generator terminals and busbars voltage, to which electrical power supply is connected, is 120 el.), an electrical air-gap torque may occur and it may be 1,8 times greater than in the case of three phase fault. Knowledge and experience regarding undesirable consequences on some synchronous generators in the plant when their mechanical resistance to certain transient phenomena in electrical power supply are analysed, (first of all automatic triple-pole reclosing technique in the network system) pointed to the need of investigating phenomena in such a case as well as values (electrical air-gap torques in the first place) which influence generator mechanical calculation. The actual application of synchronous generators in hydro-electric power plant Varazdin and hydro-electric plant Cakovec show that during automatic triple-pole reclosing, electrical air-gap torque occurs with values higher than during the ""worst"" phase to phase fault on their terminals. The above discussion led to the idea of investigating transient phenomena during the applied techniques. Software originally developed for phenomena analysis during automatic triple-pole reclosing technique into the electrical power system in actual hydro-electric power plants mentioned above showed its physical as well as theoretical credibility and may be used for mechanical and electrical design of synchronous generator with salient poles. In order to carry out calculations for synchronous generator with salient poles, so called algorithm and criterion logics have been applied, i.e. the use of computers and taking into consideration relevant criteria for allowed parameters of strain and deformation, values, and dynamic parameters included, have been highly recommended. Additional attention has been paid to shaft calculation and mechanical drive stability of generators with salient poles design as well as to calculation and design of fixing pole. When shaft calculation was considered, it became evident that it is necessary to investigate torsion moment on shaft system, axial forces, cross sectional forces on the rotor assembly and shaft loading referring to centrifugal forces of their own masses. When determining drive stability criteria with regard to critical speed which in one case is expected to be 1,5 times greater than the run-off speed (assembly being leaned against solid supports) and in the other 2,5 times greater than the nominal speed rotation (one-side magnetic force influence) ... Calculation and fixing pole design led to better knowledge of efficient method for elasticity and photoelesticity application which give a more realistic (and closer to the practice) load scheme, i.e. force participation transferred by particular parts of fixing pole construction.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: mehanički izračun; sinkroni generator s istaknutim polovima; turbina; rotor; pol; osovina; opterećenje; naprezanje; čvrstoća; deformacija; elektroenergetski sustav; prijelazno stanje; tropolni kratki spoj; dvopolni kratki spoj; elek
Keywords (Croatian): mechanical calculations; synchronus generator with salient poles; turbine; rotor; pole; shaft; loading; strain; strenght; deformation; power system; transient phenomenon; three phase fault; phase to phase fault; electrical air - gap torques; automatic tri
Divisions: 200 Department of Engineering Mechanics > 230 Chair of Mechanical Systems Dynamics
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 13:20
URI: http://repozitorij.fsb.hr/id/eprint/78

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