Electrical modeling of high voltage windings of power transformers for online partial discharge localization (original) (raw)
Related papers
Partial Discharge Detection and Localization in Power Transformer Windings
Applied Mechanics and Materials, 2014
The activity of partial discharge (PD) is one of the major causes of failure of high voltage transformers. Partial discharge detection is usually used as a preventive technique to avoid large-scale losses in the power system. Suitable and reliable methods to detect and localize PD in equipment winding insulation, such as in a transformer, are still widely researched. Among the methods used are based on the acoustic wave, on the electrical determination of the dominant capacitive region in frequency domain, and on the travelling wave method. After a brief review on current methods, a technique based on the frequency spectra of the measured signals showing the characteristic of the transfer functions is proposed. A Matlab simulation of the proposed technique is then presented. PD signals are injected at various points in a transformer winding to represent PD sources at different location within the winding. The main difficulties encountered in current methods, which is the noise and t...
Partial Discharge Localization for a Transformer Based on Frequency Spectrum Analysis
2003
Partial discharge (PD) is a major source of insulation failure in power transformers. The location of a PD source is of crucial importance in both the maintenance and repair of a transformer. This paper applies the knowledge that the poles of a PD current frequency spectrum do not change, whilst the zeros vary with the position of a PD source within the winding. An algorithm based on this approach has been developed for the localization of PDs. The algorithm adopts the wellknown ladder network to model the transformer winding, then estimates the parameters of this model from the poles of the PD current frequency spectrum. This provides the necessary information to be able to calculate a PD signal from different source locations within the model. Finally, the position of a PD source can then be estimated by a comparison of the measured and calculated PD signals. Simulation and experimentation results are demonstrated in the paper.
A hybrid transformer model for determination of partial discharge location in transformer winding
IEEE Transactions on Dielectrics and Electrical Insulation, 2007
Partial discharges are well known as a source for insulation degradation in power transformers. A hybrid transformer model is introduced to simulate the transformer winding transient response. Transformer structural data is used to determine the hybrid model parameters. Calculations of the hybrid transient model parameters are based on the parameters of the lumped parameter equivalent transformer model and electromagnetic rules. Modern computation techniques and optimizations are employed beside this model for PD location using the multi conductor transmission line model and also to analyze its propagation aimed at achieving (i) more reliable simulation results (ii) less computational time (iii) accurate results for a wide range of frequency. The simulation results on a 66 kV, 25 MVA fully interleaved winding are presented. The measurement results on this winding are employed to validate this model.
A new method for locating partial discharges in transformers
Annual Conference on Electrical Insulation and Dielectric Phenomena
During the manufacture of cast coil transformers voids are occluded in the epoxy if the vacuum impregnation process is not carefully controlled. These voids may become the sites of partial discharges which will cause the transformer to fail. Partial discharge sites in cast coil transformers are often difficult to locate. One approach to locating partial discharges in these transformers is to use information contained in the electromagnetic signals generated by the partial discharges. Transformers are compact units often containing thousands of feet of wire and internally their structure is very complex and irregular. Partial discharge signals observed at the terminals of transformers are extremely distorted because the windings are not arranged in a manner which provides a good propagation path to the measurement point. A new method for determining the axial location of partial discharges in cast coils will be presented. A signal processing algorithm is used to determine the normalized energy as a function of position along the coil. The normalized energy is interpreted in terms of the attenuation of the electromagnetic emissions from the partial discharges along the axis of the transformer. A plot of the attenuation as a function of distance along the length of coil clearly indicates the location of the partial discharges.
In this contribution a system for the detection and evaluation of electrical broadband measured partial discharges (PD) on power transformers is introduced and discussed. The theoretical background for some features of the system like the PD localisation based on the use of sectional winding transfer functions (SWTF), are explained exemplarily, whereas the operation of the system is described for two different transformers. The performed measurements could be carried out on-line due to an enhanced sensor technology, superior signal transmission techniques and improved digital signal processing, which enables a significant reduction of disturbing noise.
Overview and Partial Discharge Analysis of Power Transformers: A Literature Review
Проблемы качества электроэнергии в системах электроснабжения, 2019
The high voltage power transformer is the critical element of the power system, which requires continuous monitoring to prevent sudden catastrophic failures and to ensure an uninterrupted power supply. The most common failures in the transformer are due to partial discharge (PD) in electrical insulations which are the results of the insulation degradation over time. Different approaches have been proposed to monitor, detect, and locate the partial discharge in power transformers. This paper reviews and evaluates the current state-of-the-art methods for PD detection and localization techniques, and methodologies in power transformers. Detailed comparisons of PD detection techniques have been identified and discussed in this paper. The drawbacks and challenges of different partial discharge measurement techniques have been elaborated. Finally, brief reviews of PD denoising signals, feature extraction of PD signals, and classification of partial discharge sources have been addressed.
Partial Discharge Localization in Power Transformers Using Neuro-Fuzzy Technique
Partial discharge (PD) is the most common sources of insulation failure in power transformers. The most important tools for quality assessment of power transformers are PD detection, measurement, and classification. As for the maintenance and repair of transformers, the major importance is the techniques for locating a PD source. The transfer function-based (TF) method for power transformers' winding in the high-frequency range is commonly used in power engineering applications, such as transient analysis, insulation coordination, and in transformer design. Although it is possible to localize PD in transformer winding using the transfer function (TF) method, this method cannot be used for transformers with no design data. Previous attempts toward finding a feature that localizes PD in transformers in general that lineate with PD location were found to be less successful. Therefore, in this paper, a neuro-fuzzy technique that uses unsupervised pattern recognition was proposed to localize PD source in power transformers. The proposed method was tested on a medium-voltage transformer winding in the laboratory. The results showed a significant improvement in localizing PD for major types of PD compared to currently available techniques, such as orthogonal transforms and the calibration line method.
An electrical PD location method applied to a continuous disc type transformer winding
Proceedings of the 7th International Conference on Properties and Applications of Dielectric Materials (Cat. No.03CH37417), 2003
A 6.6kV continuous disc type winding of a distribution transformer is used to investigate the propagation of partial discharges (PD) with the aim of location. The winding was modelled, as multicondunor transmission lines with each turn represented by a transmission line. f i s approach results in the model being valid up to a few MHz in frequency. The validity of the model was confirmed hy impedance measurements on the winding. The msfer functions calculated W e e n probable PD source locations to winding terminals showed that the troughs (or zeros) change in frequency with the location of PD source and hence can be used for the location of PD. Transfer functions obtained experimentally using a discharge calibrator as the PD source, showed very good agreement with the calculations.
Partial discharge localization in transformers using UHF sensors
2011 Electrical Insulation Conference (EIC)., 2011
This paper uses detailed model for computation of sectional winding transfer functions that are necessary for partial discharge (PD) localization in transformer windings. In order to increase the accuracy of PD localization in practical cases, the circuit of PD detection impedance is included in the model. Also to increase the reliability, the use of calibration pulses is included in the localization algorithm. By that, it is possible to optimize model parameters before employing them to find the location of discharges. The accuracy of the method is analyzed by measurements on a special prepared transformer in laboratory.