FEM Modelling of the Influence of the Remaining Windings on the Frequency Response of the Power Transformer (original) (raw)
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Energies
Frequency response analysis (FRA) is being employed worldwide as one of the main methods for the internal condition assessment of transformers due to its capability of detecting mechanical changes. Nonetheless, the objective interpretation of FRA measurements is still a challenge for the industry. This is mainly attributable to the lack of complete data from the same or similar units. A large database of FRA measurements can contribute to improving classification algorithms and lead to a more objective interpretation. Due to their destructive nature, mechanical deformations cannot be performed on real transformers to collect data from different scenarios. The use of simulation and laboratory transformer models is necessary. This research contribution is based on a new method using Finite Element Method simulation and a lumped element circuit to obtain FRA traces from a laboratory model at healthy and faulty states, along with an optimization method to improve capacitive parameters f...
TLM-method for Computer Modeling of Transformers’ Windings Frequency Response
Poznan University of Technology Academic Journals. Electrical Engineering, 2012
The diagnostics of power transformers is a very fast developing branch, due to increasing average age of assets and changes in asset management strategies, nowadays companies introduce asset management based on technical condition. One of important methods used for diagnostics of a transformer’s active part is Frequency Response Analysis (FRA). It allows determination of mechanical condition of windings, their displacements, deformations and electric faults, as well as some problems with internal leads and connections, core and bushings. For the aim of windings impedance modeling the transmission-line models are applied. The idea of TLM was presented in [1]. While the length of transformer wires is comparable to wave length at high frequency, such approach is reasonable. The paper presents examples of models created for simple windings.
Modeling of frequency response of transformer winding with axial deformations
Archives of Electrical Engineering, 2014
One of important methods used for diagnostics of a transformer’s active part is Frequency Response Analysis (FRA). It allows to determine the mechanical condition of windings, their displacements, deformations and electric faults, as well as some problems with internal leads and connections, core and bushings. Still pending problem is interpretation of measurements results. One of approaches is application of computer modeling to simulate various failure modes and connected with them changes in FRA response. The paper presents two types of models, one based on lumped parameters with RLC elements, and one based on distributed parameters with TLM method. Both methods give similar results, comparable to real measurements of simulated coil
Impact of other windings on frequency response of power transformers
2015
The diagnostics of power transformers is a very fast developing branch. Due to increasing average age of assets and changes in asset management strategies, nowadays companies introduce asset management based on technical condition. One of important methods used for diagnostics of a transformer’s active part is Frequency Response Analysis (FRA). It allows determination of mechanical condition of windings, their displacements, deformations and electric faults, as well as some problems with internal leads and connections, core and bushings. In the FRA measurements of many power transformers there can be observed a first resonance, which position on frequency axis and damping factor seems to be similar for primary and secondary windings. The authors are going to explain this strange phenomenon, not depending on inductance of the winding being measured.
Recent Developments in the Modelling of Transformer Windings
2021
The paper provides a review of the modelling techniques used to simulate the frequency response of transformer windings. The aim of the research and development of modelling methods was to analyze the influence of deformations and faults in the windings on the changes in the frequency response. All described methods are given with examples of the modelling results performed by the authors of this paper and from literature sources. The research is prefaced with a thorough literature review. There are described models based on lumped parameters with input data coming from direct calculations based on the winding geometry and obtained from FEM modelling software and models considering the wave phenomena in the windings. The analysis was also performed for practical problems in winding modelling: the influence of windings other than the modelled one and the influence of parallel wires in a winding.
A Contribution to the Frequency Analysis and Transient Response of Power Transformer Windings
Electric Power Components and Systems, 2014
The paper suggests a Laplace-domain technique for analyzing the transient response of non-uniform transmission lines with arbitrarily varying characteristic impedance. A mathematical model based on a distributed parameter Laplace-domain representation will be derived taking into account the waveform of the current and/or voltage sources initiating the transients, as well as the circuit constants of the non-uniform line. From the location dependence of the line's characteristic impedance and the application of a recursive circuit reduction technique, s-domain expressions for the line's input impedance for any loading condition will be determined. The voltage and current distributions along the line can then be obtained. These expressions, followed by numerical Laplace inversion, will be utilized for finding the line's transient response in the time domain.
A Review of Frequency Response Analysis Methods for Power Transformer Diagnostics
Energies, 2016
Power transformers play a critical role in electric power networks. Such transformers can suffer failures due to multiple stresses and aging. Thus, assessment of condition and diagnostic techniques are of great importance for improving power network reliability and service continuity. Several techniques are available to diagnose the faults within the power transformer. Frequency response analysis (FRA) method is a powerful technique for diagnosing transformer winding deformation and several other types of problems that are caused during manufacture, transportation, installation and/or service life. This paper provides a comprehensive review on FRA methods and their applications in diagnostics and fault identification for power transformers. The paper discusses theory and applications of FRA methods as well as various issues and challenges faced in the application of this method.
Transformer modeling for FRA techniques
IEEE/PES Transmission and Distribution Conference and Exhibition, 2002
Transformers are one of the main devices in the utility grids. Reliability, power quality, economic cost and even the company image are influenced by the transformers health. For this reason, advanced techniques have been developed in recent years in order to improve the transformer life assessment. FRA (Frequency Response Analysis) Techniques are nowadays widely used by the electric utilities as one of these advanced techniques. They are specially appreciated to detect winding displacements inside the transformer. The main problem about FRA Techniques is to interpret the observed evolution of the frequency response in order to identify both failures and failures tendencies in the transformer. In order to solve this problem, a Modeling Tool is proposed in this work using the frequency response measured at the transformer.
The Characteristics of Frequency Response on Winding Faults and Configurations of Transformer
Thesis, 2019
This research presents a study on the monitoring of several winding configurations of power transformers using Frequency Response Analysis (FRA). The frequency response provides indications of any mechanical and electrical changes in the transformer's active parts. Three three-phase transformers were tested with the aim to investigate their FRA responses due three case studies. They are due to vector group, three types of faulty winding and also the effect of coupling in the three-phase coretyped transformers. The tests were repeated to three transformers to carry out the desired condition scenario of the FRA responses. The first case is to investigate the characteristics of the FRA response due to different vector groups. It is found that it gives subtle to the response and mainly altering the medium frequency region. The second case study is the investigations of the effect of three types of faulty winding in the FRA response. They are performed by physically simulate the faults to the transformers. The faults are inter-turn short circuit (SC) fault, local overheating and radial deformation. The results show that the SC causes the starting magnitude to increase and the resonance at the low frequency region to shift towards higher frequencies. Meanwhile, during local overheating fault, the winding carries out additional resistance at the winding. It is found that it causes the alteration of the response at the very low frequency region. Lastly, the study found that radial deformation causes the responses to change in the mid-frequency region. The third case study is to investigate the effect of coupling in the three-phase transformers. This is performed by investigating the effect of fault at winding of other phases to the response of measured phase. It is found that faulty occurred in winding of other phases could actually affect the response of measured winding. The location of the fault determines how severe it is affecting the response. The findings from this research could be helpful in enriching the knowledge to evaluate the FRA response.
2007
This paper discusses the possibility of utilizing power transformer modelling for interpretation of frequency response analysis (FRA) measurements. FRA is a reliable technique for power transformer winding distortion and deformation assessment and monitoring. A lumped parameter model of a three phase power transformer is briefly presented and applied to simulate frequency responses at various winding fault conditions such as short-circuited turns, axial displacements and radial deformations. Simulations and discussions are presented to explore the potentials of the model to transformer fault detection based on FRA measurements.