Modeling and characterization of single-phase and three-phase transformers based on minimum information
(English) The main objective of this thesis is to develop and validate simple but sufficiently accurate mathematical models for single-phase and three-phase transformers, by estimating their parameters from simple laboratory tests and field measurements, in particular, from the information obtained...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/690618 |
| Acceso en línea: | http://hdl.handle.net/10803/690618 https://dx.doi.org/10.5821/dissertation-2117-406724 |
| Access Level: | acceso abierto |
| Palabra clave: | Inrush current Residual flux Single-phase transformer Three-legged transformer Current transformer Saturation curve Reluctance Corriente de conexión Flujo residual Transformador monofásico Transformador de tres columnas Transformador de corriente Curva de saturación Reluctancia Àrees temàtiques de la UPC::Enginyeria elèctrica 621.3 |
| Sumario: | (English) The main objective of this thesis is to develop and validate simple but sufficiently accurate mathematical models for single-phase and three-phase transformers, by estimating their parameters from simple laboratory tests and field measurements, in particular, from the information obtained from the inrush current. The energizing process of a transformer results in the generation of a high inrush current due to the saturation of the transformer core. This current can cause several problems, such as protections tripping and consequently being out of service. Clearing faults in the transmission network can also lead to transformer saturation. A part of this work aims to develop methodologies for the reduction of these high inrush currents. In the literature, a great effort has been dedicated to the modeling, identification and analysis of electrical transformers. The representation of a transformer can be very complex due to the different types of core configurations and the large number of transformer parameters, as well as the fact that some of these parameters are nonlinear and even frequency dependent. These include core and coil configurations, self and mutual inductances among coils, dispersion fluxes, skin and proximity effects in coils, magnetic core saturation, hysteresis cycles, losses due to eddy currents, and capacitive effects. The materials commonly used in transformer cores, like ferromagnetic materials, exhibit non-linear magnetic permeability, and usually work slightly saturated. The behavior of a non-linear core is given by the relationship between the magnetic field and magnetic induction, known as the magnetization or saturation curve. There are different ways to model the nonlinear operation of a magnetic core, ranging from finite elements to single-valued functions, through especially complex models such as Jiles-Atherton or Preisach hysteretic models. This work is focused on low frequencies models (up to a few kHz), whose parameters reproduce in detail those situations in which the nonlinearity of the magnetic circuit significantly influences its dynamic behavior. For example, inrush current can be predicted, for which modeling or estimation of the residual flux is necessary. The adjustment of the parameters will be based on experimental measurements to which the developed adjustment algorithms will be applied. These measurements will be obtained both in specific laboratory tests and in transient connection records in transformers connected to the distribution network. Although articles on transformers have been published for more than seventy years, the high number of current publications on their modeling and on the problems derived from their non-linear behavior is an indication that the issue has not been resolved satisfactorily and which is still relevant. |
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