Application of a new method in detecting a mechanical failure associated with series capacitance change in a power transformer winding
01 Jun 2014-pp 1-4
TL;DR: The frequency response analysis (FRA) based method is expected as an efficient one in diagnosis of mechanical failures in windings of power transformers, especially in cases other testing methods cannot provide any indication for the diagnostic as discussed by the authors.
Abstract: The Frequency Response Analysis (FRA) based method is expected as an efficient one in diagnosis of mechanical failures in windings of power transformers, especially in cases other testing methods cannot provide any indication for the diagnostic. However, the current FRA assessment which is based on the relevant Chinese standard and other draft international standards is not sensitive enough in detecting such failures in all cases.
Citations
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TL;DR: In this article, the authors proposed an effective method applied to frequency response interpretation in low frequency range and mechanical failure diagnosis support based on measurements and analysis of a physical lumped component transformer circuit.
Abstract: The authors of this paper proposed an effective method applied to frequency response interpretation in low frequency range and mechanical failure diagnosis support based on measurements and analysis of a physical lumped component transformer circuit. To extend the interpretation until medium frequencies where mechanical failures influence most, this paper presents a novel approach on determining parameters in a physical distributed component circuit. The most important contribution of this paper is the possibility of determination of electrical parameters in the distributed circuit without knowing detailed knowledge of the transformer construction, which has been a challenge so far. In addition, the application capability of the distributed circuit in diagnosis of several mechanical failures in a distribution transformer is also investigated.
15 citations
01 Nov 2017
TL;DR: The application of the finite element method (FEM) is discussed to construct a lumped parameters ladder network of an actual transformer winding of a high-frequency transformer winding.
Abstract: Power transformers are one of the critical points in the renewable energies networks for the transport and distribution of the electric energy. As a result, the diagnosis of transformers is necessary to ensure the reliability and service life. The frequency behavior of the transformer winding is generally studied using a high-frequency model to diagnose the various damages of the winding. For this purpose, this paper discusses the application of the finite element method (FEM) to construct a lumped parameters ladder network of an actual transformer winding. The investigated coil is discretized in five (05) identical sections that includes 30 turns for each. In addition, after the experimental validation of the adopted model, a diagnostic study to the axial deformations of the transformer winding was made using the parameters analysis of the detailed model and the transfer function obtained from the FRA test.
9 citations
01 Sep 2016
TL;DR: In this paper, the capacitances in physical distributed circuits of power transformers for simulation based frequency response interpretation have been calculated analytically based on internal transformer design and dielectric property data.
Abstract: Capacitances in physical distributed circuits of power transformers for simulation based frequency response interpretation have been so far calculated analytically based on internal transformer design and dielectric property data. For the practical application on in-service power transformers, the capacitances should be appropriately determined based on analysis of terminal measurements and simulation. This paper presents a study case on a black-box power transformer for proving this application possibility.
5 citations
Cites background from "Application of a new method in dete..."
...To effectively interpret frequency responses measured on power transformers for mechanical failure diagnosis purpose, the simulation task based on physical transformer circuits should be involved; this is due to the fact that, the quantitative assessment [1] is not fully efficient for real cases [2, 3]....
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TL;DR: In this paper, a cascade of parallel RLC cells, whose parameters are identified using the frequency response analysis data measurements obtained on each transformer phase, are used to simulate the frequency behavior of the transformer windings without reference to the geometries of the coils.
Abstract: Abstract The behavior analysis of the transformer is usually achieved by the frequency response analysis (FRA), which is obtained by the application of a very low AC voltage in over a wide frequency range. This paper presents a low and high frequency modelling approach of a three-phase transformer. The developed model consists of a cascade of parallel RLC cells, whose parameters are identified using the frequency response analysis data measurements obtained on each transformer phase. Thus, the proposed model can simulate the frequency behavior of the transformer windings without reference to the geometries of the coils which makes it easily usable in the failure diagnosis field. Experimental results on a 300 VA laboratory transformer validate the proposed model.
2 citations
30 Aug 2015
TL;DR: In this article, the authors proposed a new method based on simulation of a lumped three-phase equivalent circuit of power transformers to interpret frequency responses effectively, but only within low frequency range.
Abstract: In the field of diagnosis of mechanical failures in power transformer’s active part, i.e., windings, leads and the core, the technique of Frequency Response Analysis (FRA) has been recently approved as the main application tool. Mechanical failures in transformer windings reflect changes on measured terminal frequency responses normally in medium frequency range, from several to hundreds of kHz, which is in fact not easy to interpret for diagnosis. The authors proposed a new method based on simulation of a lumped three-phase equivalent circuit of power transformers to interpret frequency responses effectively, but only within low frequency range. This limitation is due to the fact that, the circuit cannot reflect well physical phenomena at medium and higher frequencies. To improve the FRA performance of the proposed method at medium frequencies for transformer failure diagnosis purpose, the paper introduces an investigation on a distributed three-phase equivalent circuit of a 200 kVA 10.4/0.46 kV Yy6 distribution transformer. Result of the investigation is a simplified procedure in determination of electrical parameters associated with the distributed circuit for better simulation based FRA interpretation at medium frequencies.
References
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TL;DR: In this paper, a vector-network analyzer is used to determine most electrical parameters of the transformer active part based on only the driving-point impedance tests performed by means of a vector network analyzer.
Abstract: To diagnose electrical and mechanical failures on the active part of power transformers efficiently, different state-of-the-art testing methods are recommended to be performed since transformers are complex devices Measurement results can be equivalent electrical parameters relating to the windings (resistances, leakage/zero-sequence inductances and capacitances), core magnetic property (via induced voltages and exciting currents) or terminal frequency responses (standard FRA tests) Consequently, it is not easy for normal users to implement all necessary measurements, which require much time and training skills due to use of different specialized testing devices To help users for fast and efficient diagnostics, the paper presents a new method in determining most electrical parameters of the transformer active part based on only the driving-point impedance tests performed by means of a vector-network analyzer More importantly, the method can be applied to give a FRA interpretation based on physical electrical parameters, which is currently requested from relevant standards The physical FRA interpretation is found to be useful in calculating immeasurable series capacitances of windings in transformer bulk, which is still problematic until now Investigation on a large distribution transformer shows that the new method is simple, less time consuming but efficient
50 citations
TL;DR: In this paper, a novel procedure to determine the series capacitance of a transformer winding, based on frequency-response measurements, is reported, which is based on converting the measured driving-point impedance magnitude response into a rational function and thereafter exploiting the ratio of a specific coefficient in the numerator and denominator polynomial.
Abstract: A novel procedure to determine the series capacitance of a transformer winding, based on frequency-response measurements, is reported. It is based on converting the measured driving-point impedance magnitude response into a rational function and thereafter exploiting the ratio of a specific coefficient in the numerator and denominator polynomial, which leads to the direct estimation of series capacitance. The theoretical formulations are derived for a mutually coupled ladder-network model, followed by sample calculations. The results obtained are accurate and its feasibility is demonstrated by experiments on model-coil and on actual, single, isolated transformer windings (layered, continuous disc, and interleaved disc). The authors believe that the proposed method is the closest one can get to indirectly measuring series capacitance.
39 citations
TL;DR: In this article, a method to indirectly measure series capacitance (Cs) of a single, isolated, uniformly wound transformer winding, from its measured frequency response, was proposed and implemented on an actual three-phase transformer.
Abstract: Recently, authors published a method to indirectly measure series capacitance (Cs) of a single, isolated, uniformly wound transformer winding, from its measured frequency response. The next step was to implement it on an actual three-phase transformer. This task is not as straightforward as it might appear at first glance, since the measured frequency response on a three-phase transformer is influenced by nontested windings and their terminal connections, core, tank, etc. To extract the correct value of Cs from this composite frequency response, the formulation has to be reworked to first identify all significant influences and then include their effects. Initially, the modified method and experimental results on a three-phase transformer (4 MVA, 33 kV/433 V) are presented along with results on the winding considered in isolation (for cross validation). Later, the method is directly implemented on another three-phase unit (3.5 MVA, 13.8 kV/765 V) to show repeatability.
13 citations
TL;DR: In this paper, the authors analyze the physics of the process and gain insight on test circuit selection and analysis of the results, and suggest methods for avoiding erroneous test results are suggested.
Abstract: Low voltage and single-phase excitation are often used to measure leakage reactance or short-circuit impedance of transformers. Winding distortion may be detected by comparing field results with factory nameplate values measured at 25-100% of the rated current using three-phase excitation. The results of single- and three-phase excitation will not always correlate. If the voltage applied in the field is not properly selected then the data may be influenced by the magnetizing reactance. The resulting difference between the nameplate value and the field data might then lead to erroneous analysis of test results and could be interpreted as an indication of winding distortion. The intent of this paper is to analyze the physics of the process and gain insight on test circuit selection and analysis of the results. Methods for avoiding erroneous test results are suggested.
8 citations
Journal Article•
TL;DR: Streszczenie as mentioned in this paper presented a procedure to obtain the parameters of the transformer physical-circuital model based on data obtained from external measurements, without need for design data.
Abstract: Modeling a transformer usually requires all its construction data, which is very difficult to obtain for the units in operation; for new transformers manufacturers are not usually willing to provide this information. This paper presents a procedure to obtain the parameters of the transformer physical-circuital model based on data obtained from external measurements, without need for design data. This was done by using different tests, some routine tests like losses and other special tests such as frequency response or FRA. It is also presented the application of the procedure to obtain the model of a 15-KVA 13200 / 244 V single-phase transformer, and its use to simulate the frequency response. Streszczenie. W artykule zaprezentowano procedure określania parametrow modelu transformatora na podstawie pomiarowych danych eksperymentalnych. Przedstawiono przyklady testow rutynowych jak i specjalnych. Uzyskane wyniki sprawdzono na przykladzie transformatora 15- KVA 13200/244 V. (Metodologia eksperymentalnego określania parametrow modelu transformatora)
5 citations