diplomsko delo
Matic Žumer (Author), Boštjan Blažič (Mentor)

Abstract

Zagotavljanje ustreznih napetostnih razmer je ena izmed temeljnih nalog distribucijskega podjetja, zato je meritvam napetosti posvečena velika pozornost. Pri njihovi obdelavi opazimo medsebojno odstopanje vrednosti napetosti v posameznih fazah, t.i. napetostno nesimetrijo. Ta se v omrežju navadno pojavi zaradi enofaznih porabnikov, zato je njena prisotnost v majhnih vrednostih nekaj normalnega, večje vrednosti pa lahko nakazujejo na težave v omrežju. Posledica tega je padec kvalitete dobavljene električne energije. Na začetku diplomske naloge je opisan pojav napetostne nesimetrije. Temu sledi predstavitev zajema podatkov meritev v nizkonapetostnem omrežju in pregled grafičnih prikazov – uporabljeni so prikazi napetostnih profilov v omrežju in izračunane napetostne nesimetrije. Pred analizo se opredelimo do dovoljene mejne vrednosti, ki služi za merilo glede na veljaven standard. Analiza je najprej narejena za tri pogoste povzročitelje napetostne nesimetrije – enofazne odjemalce, razpršene vire in anomalije, ki se pojavijo v omrežju. Poleg analize napetostnih razmer so navedene tudi nekatere rešitve za omejevanje le-te. Sledi celostna analiza nizkonapetostnega omrežja, s podrobno preučitvijo nizkonapetostnega izvoda, kjer so bila najdena odstopanja v meritvah napetosti med posameznimi fazami. Izkaže se, da samo z analizo napetostnih razmer vzroka za nastanek napetostne nesimetrije ne moremo vedno najti. Nazadnje je predstavljen tudi vpliv preobremenjenih distribucijskih transformatorjev na napetostne razmere v omrežju. Prikazana je primerjava napetostnih razmer pred in po zamenjavi transformatorja, ki je z obremenitvijo redno prehajal svojo nazivno moč. Ugotovili smo, da zgolj z analizo napetostnih razmer vzroka za nastanek nesimetrije ne moremo vedno odkriti. Spremljanje njenih vrednosti je bolj uporabno za iskanje nizkonapetostnih omrežij ali izvodov, kjer so prisotne še neodkrite težave, točno lociranje pa izvedemo z drugimi metodami.

Keywords

napetostna nesimetrija;neravnotežje napetosti;analiza napetostnih razmer;odkrivanje napak;visokošolski strokovni študij;Aplikativna elektrotehnika;diplomske naloge;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UL FE - Faculty of Electrical Engineering
Publisher: [M. Žumer]
UDC: 621.31(043.2)
COBISS: 156405763 Link will open in a new window
Views: 72
Downloads: 19
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Other data

Secondary language: English
Secondary title: Analysis of voltage unbalance in distribution networks
Secondary abstract: One of the main tasks of a power distribution company is to ensure and maintain the nominal network voltage levels. Therefore, there is a great emphasis on the voltage measurements. Analysing the measured data shows discrepancies between the voltage levels in the different phases or so-called voltage unbalance. This is a consequence of single-phase loads and is always present in small quantities, however higher level of asymmetry can indicate a fault on the network which results in a lower quality of energy supply. The thesis begins with a description of the voltage unbalance, followed by a presentation of field data measured in low voltage network. Presented is a general graphical overview, where voltage profiles and voltage unbalance calculations in the network are shown. Prior the analysis, we define the allowed limit values based on the current standard. Three common voltage unbalance causes are analsyed first; single-phase loads, distributed energy sources and network anomalies. Alongside network condition analysis, a few solutions for mitigating the problem are listed. Furthermore, we have a complete analysis of the low voltage network, with a detailed examination of the feeder, where voltage unbalance was discovered. It turns out that analysis of voltage conditions alone isn’t enough to find the reason for the occurring voltage unbalance. Finally, we present the effect of overloaded distribution transformers on the voltage conditions in the network, where we show the comparison of voltage conditions before and after the change of the transformer, that was previously exceeding its maximum rated power. We discovered that it’s not always possible to determine the cause of the voltage unbalance by only analysing voltage measurements. Such analyses are more useful for finding low voltage networks or feeders where we haven’t yet detected any issues while pinpointing the issue itself requires different methods.
Secondary keywords: voltage unbalance;voltage asymmetry;fault detection;
Type (COBISS): Bachelor thesis/paper
Study programme: 1000315
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za elektrotehniko
Pages: XVIII, 39 str.
ID: 19249589