Power transformer windings can be damaged by internal faults, such as short-circuit currents and the forces they generate, which can lead to, e.g., internal shorts due to damaged insulation. If these faults are not detected early, they can lead to catastrophic failures. In general, distributed-parameter models can simulate the performance of a transformer in both time and frequency domains more accurately than conventional lumpedparameter models, especially at higher frequency range (> 1 MHz). In this work, a multiconductor transmission line (MTL) model is used to simulate transformer windings in the frequency domain. Two typical winding configurations, continuous disk and interleaved disk, are studied. Internal shorts and buckling faults are applied to both models, and their frequency responses are compared using the frequency response analysis (FRA). The results show that each fault causes a noticeable change in the resonant frequency and admittance curve, except in the case of buckling in the interleaved-disk winding. The results demonstrate that combining MTL simulations with FRA can effectively identify the type of internal faults in transformer windings, offering a more comprehensive diagnostic tool than conventional frequency-domain analyses using lumped-element models.
When a power transformer subjected to transient over-voltages containing different harmonic components, the frequency components of over-voltages are coupled with the inherent electrical frequency of the transformer winding, which can induce high-amplitude resonant over-voltages in the winding and thus lead to transformer insulation failures. To analyze the electrical resonance characteristics of transformer windings, this paper establishes an equivalent model of transformer windings with reference to the actual transformer structure, and calculates the time-domain and frequency-domain distributions of transformer winding voltages. Furthermore, a test model of a real three-phase transformer is constructed, with measurement wires embedded at different positions of the windings. Experimental tests are conducted to investigate the electrical resonance characteristics of the transformer windings, verifying the effectiveness of the established equivalent model. Finally, based on the equivalent model, the effects of winding structure, number of turns per disk, wire thickness, and oil duct width on the winding resonance characteristics are analyzed.
Ya-Nan Chang, Guo-Feng Zhao, Yushan Cao et al.· Engineering Research Express· 0 citations
Inter-turn short circuit (ITSC) issues are a common electrical failure mainly caused by the deterioration of winding insulation in the machine over time. Failing to detect such issues early can lead to catastrophic consequences. This article investigates the interturn fault in the stator winding of a doubly-fed induction generator (DFIG) used in wind turbines. A flux linkage difference vector (FLDV) model is introduced in this study for fault detection. Additionally, an artificial neural network (ANN) model is proposed to classify these faults. Specifically, a short-circuit fault is induced in each phase of the stator winding, and the faults are classified by assigning different magnitudes to the respective phases. The ANN is trained to identify which phase contains an interturn fault, with output waveform amplitudes of 1, 2, or 3 corresponding to faults in phases "a," "b," and "c." If no fault is present, the waveform magnitude is designated as "0." This approach enables early fault diagnosis by analyzing waveform patterns, thereby preventing overheating caused by short circuits and avoiding severe, irreversible damage to the windings.
Vivek Kushwaha, S. Maurya, Arvind Kumar Yadav· International Journal of Pow...· 0 citations
As a critical component of power systems, the operational status of power transformers directly affects the safety and reliability of the power grid. Addressing the challenge that traditional methods struggle to achieve online monitoring of winding deformation faults, this paper proposes a novel method for online detection of transformer winding deformation based on Lissajous figure trajectories. This method involves collecting voltage and current signals from both the highand low-voltage sides, constructing voltage-squared and instantaneous power characteristics, and generating corresponding Lissajous curves. By establishing a mapping relationship between changes in the mechanical structure of the windings and electrical parameter characteristics, the method enables the qualitative identification and quantitative assessment of axial and radial deformation in the windings. Experimental results demonstrate that this method can detect minor winding deformation (deformation amount = 3%) and exhibits higher sensitivity in detecting radial winding deformation compared to the frequency response analysis method. This study provides a new technical approach for online monitoring of transformer winding deformation and holds significant engineering application value for enhancing the condition monitoring and intelligent operation and maintenance of power grid equipment.
Lai-Hong Wei· European Conference on Elect...· 0 citations
Internal temperature monitoring is an important approach for assessing the operating condition of power transformers. Temperature-rise characteristics not only indicate faults such as inter-turn short circuits but also indirectly reflect the diffusion and transport behaviors of characteristic dissolved gases within the transformer oil. To enable early warning and localization of inter-turn short circuits in transformer windings, this paper proposes a method based on monitoring the oil temperatures at the inlets and outlets of the transformer cooling system. First, a simulation model of a 110 kV transformer was developed, and coupled thermal–fluid simulations were performed to analyze the oil-temperature distributions in the transformer body and cooling system under normal operating conditions and representative inter-turn short-circuit conditions. Next, a simulation-based fault-localization strategy is proposed to investigate whether the spatial temperature distribution of cooling-system oil can be used to infer the vertical position; faulty phase; and, for certain fault locations, the winding side of an inter-turn fault. Finally, the temperature sensor locations were selected, and the performance of the localization strategy was evaluated. The simulation results demonstrate the feasibility of using the temperature distribution of cooling-system oil for the detection and localization of inter-turn short-circuit faults.
Zi-Fan Zhao, Shan Yu, Shi-Man Lin et al.· Energies· 0 citations
The main scope of this research was to complete and validate the analysis of stator winding topologies of six-phase AC machines using the winding quality factor by determining fault tolerance and validating it through experimental tests. This paper proposes a unified and practical methodology for evaluating the performance of stator windings in six-phase induction machines, with emphasis on magnetic field quality and fault-tolerant operation. The approach combines analytical modeling of the magnetomotive force (MMF) with its graphical representation using the MMF polygon, enabling an efficient assessment of harmonic content through a global indicator, referred to as the winding quality factor. Several representative winding topologies are analyzed within a common framework, including single-layer and double-layer configurations with full-pitch and short-pitch coils, suitable for generating homologous series of six-phase machines. The study considers both normal operating conditions and post-fault regimes, particularly operation with a single three-phase set. The results reveal the strong influence of winding topology on harmonic distortion and overall machine performance, highlighting the trade-offs between magnetic field quality and fault tolerance. It is shown that appropriate winding design can reduce spatial harmonics and improve robustness under degraded operating conditions. The theoretical findings are validated through experimental investigations, demonstrating good agreement between analytical predictions and measured data. A parallel analysis was performed between the theoretical findings and experimental data, and the results conform to the authors’ expectations.
P. Todos, Ghenadie Tertea, I. Nucă et al.· Technologies· 0 citations
This work develops a circuit-based simulation framework dedicated to the study of stator inter-turn short-circuit (ITSC) defects in three-phase induction machines. The formulation relies on an internal equivalent circuit (IEC) description in which every stator coil and rotor bar is characterized individually through its own electrical quantities. This strategy preserves the physical structure of the machine and enables localized and parameterized fault injection (shorted-turn ratio β and fault resistance Rf) by modifying only localized resistance and inductance values. The model is implemented using MATLAB/Simulink software and validated through experimental measurements obtained from a dedicated test bench under both healthy and faulty conditions. Frequency analysis based on FFT is used to identify distinctive fault signatures. The results show a characteristic fault harmonic at 98 Hz (β = 5%, R
f
= 0.5 Ω), confirming the theoretical predictions. The proposed model demonstrates its suitability as a computationally light yet physically meaningful simulation tool for fault analysis and diagnostic algorithm development in 3-phase induction machines under ITSC fault conditions.
Anas Hankour, A. Yazidi, F. Betin et al.· EPJ Web of Conferences· 0 citations
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