Partial Discharge Detection and Localization in Power Transformer Windings (original) (raw)
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International Journal of Emerging Trends in Engineering Research, 2022
Partial discharges are the main causes of degradation of the insulation system in power transformers. Their permanent monitoring is therefore of fundamental importance, in the way that it ensures a better assessment of the level of electrical insulation. Several types of partial discharges are present in power transformers depending on the components of the electric field to which the insulation is subjected. Many on-line methods are used to the continuous measurement of partial discharges, including the acoustic method which doing both measurement of electrical parameters and localization of the sources of partial discharges. This article deals with both recognition and classification of partial discharges by analysis of acoustic signals. The goal is to reproduce various types of partial discharges present in the transformers (surface, internal, and corona discharges) by several structures of electrodes in a prototype transformer filled with insulating oil. The generation of partial discharges is done using an experimental setup consisting of a controlled 220V/50kV HV transformer connected to a prototype of transformer containing an electrode system. The experimental procedure are carried out according to the protocol of the IEC 61270 standard. The measurement of the acoustic signals on the tank is carried out using a conventional broadband sensor from the company ACOUSTIC EMISSION (GI150). Both signal analysis obtained in the frequency domain using the time-frequency response and high-resolution frequency analysis (MUSIC) makes it possible to clearly distinguish the type of discharge produced.
Acoustic localisation of partial discharge in power transformers
2015
Detecting partial discharges in the insulation system of a power transformer at an early stage reduces the risk of total breakdown. One method to detect partial discharges is acoustic measurement. With this technique detection and localisation of partial discharge is possible by placing acoustic sensors on the surface of the transformer tank. The low impact of electrical interferences from outside the measurement set-up constitutes one of the strengths of the acoustic method. A further advantage is the ability to identify the position of the partial discharge source, which is needed to estimate the risk and to enable a fast and effective repair. The sensitivity and accuracy of the PD localisation can be improved with a combination with conventional electrical measurement or with Ultra High Frequency (UHF) measurement method. Since the UHF measurement method is more advantageous for measurement environments with heavy interferences in the field, the combination with acoustic localisa...
2011
This paper describes an advanced combination of electric and acoustic measurements for the localization of partial discharges in power transformers. The measurement of acoustic signals is triggered by an electric partial discharge signal. The distance between the partial discharge source and sensor is calculated from the time the acoustic wave needs to travel from the partial discharge source to the sensor. Different factors influencing the accuracy of the determination of the distances between the partial discharge source and the acoustic sensor are evaluated.
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.
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.
Acoustic measuring of partial discharge in power transformers
Measurement Science & Technology, 2009
Power transformers' reliability can be seriously affected by partial discharges. For this reason, it is necessary to implement technical methods to identify endangered equipment before catastrophic failures occur. A well-known method that can be applied either in the laboratory or in the field is the detection and localization of partial discharges, by means of the analysis of the acoustic signals they produced. An innovative partial discharge detector was developed based on the analysis of an acoustic or electrical PD signal envelope. This paper describes the architecture of the developed acoustic detector, which is composed of a set of ultrasonic sensors, signal conditioning and control modules, a graphical interface and the required software for the location of the affected area within the transformer. The conditioning and control modules perform analog to digital conversion, arrival time measurement, communication and control operations. Finally, some power transformer diagnostic testing is presented and discussed.
A Strategy to Locate Partial Discharges in Power Transformers using Acoustic Emission
This paper presents a solution for the problem related to Partial Discharges (PD) source localization in oil-isolated transformers, using Genetic Algorithms. As known in literature, the simple PD detection is not enough to take a decision about intervening, so the localization is necessary to assess the risk and to plan corrective actions. The parameters extracted from the acoustic signals collected by piezoelectric sensors installed outside of the transformer, provide the correct position of PD. From parameters extracted of acoustic signals collected from piezoelectric sensors installed outside the transformer, the proposed algorithm provides the position where the PD is occurring. This work compares the performance of the method using Genetic Algorithms and those using iterative method, which is normally used to solve this problem. The conclusion describes the advantages of the proposed solution.
Detection of partial discharge acoustic emission in power transformer
International Journal of Electrical and Computer Engineering (IJECE), 2019
Partial discharge is one the most important factor that leads to deteroration and failure of the power transformer transformer. Acoustic emission detection is effective method to evaluate the health index of the power transformer using acoustic emission (AE) sensors for partial discharge (PD) measurement is considered as one of the most promising techniques to detect and localize PD activities inside the transformer tank. On the other hand, AE waves suffer from high attenuation and reflections while traveling from the PD source to the AE sensor. The modeling of the AE wave can help to understand the behavior of the AE PD signal during its travel. In this paper, the AE PD signal is assumed to be composed of different frequencies. This work aims to investigate the influence of the frequency value on the attenuation and arrival time of the acoustic wave. 1. INTRODUCTION Monitoring of PD is one of the tools to identify the health condition of transformer insulation system. When PD activities are initiated, the resulting energy is transformed into different forms as mechanical, electrical, and chemical energy. Among all PD detection techniques, there is a growing interest in the PD acoustic detection method because it overcomes several disadvantages of using electrical methods like low susceptibility to electromagnetic noise and cost effectiveness. A significant effort has been exerted to understand the behavior of the PD acoustic wave while travelling from its source to the sensor. A mathematical model was introduced in [1] by solving the acoustic wave governing equations through finite elements technique. The presented model describes the propagation of PD acoustic wave in the whole medium (oil and steel) with contour plots to show the attenuation at different locations. Moreover, it examined the propagation properties under the effect of changing oil density as the temperature increased. The effect of frequency on acoustic PD attenuation was studied in [2] by applying pulses with different widths. As the frequency of PD pulse increases, this resulted in higher attenuation. This understanding of the PD behavior can be very helpful to predict the actual frequency ranges of the generated PD based on the received one. An approach in [3] presented the PD as a multiple of different sine waves with different frequencies and attempted to understand the interaction between them as it happens in PD pulse. This approach considers that all these sine waves will travel with the same velocity which is not accurate because each frequency will travel with different velocity as discussed by reference [4]. It has been mentioned that each frequency component of the PD wave will travel with different velocity and hence will arrive to the tank wall at different time which will lead to a higher degree of distortion of the received PD wave.
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.
Energies
The article presents a novel on-line partial discharge (PD) monitoring system for power transformers, whose functioning is based on the simultaneous use of three unconventional methods of PD detection: high-frequency (HF), ultra-high frequency (UHF), and acoustic emission (AE). It is the first monitoring system equipped in an active dielectric window (ADW), which is a combined ultrasonic and electromagnetic PD sensor. The article discusses in detail the process of designing and building individual modules of hardware and software layers of the system, wherein the most attention was paid to the PD sensors, i.e., meandered planar inverted-F antenna (MPIFA), high-frequency current transformer (HFCT), and active dielectric window with ultrasonic transducer, which were optimized for detection of PDs occurring in oil-paper insulation. The prototype of the hybrid monitoring system was first checked on a 330 MVA large power transformer during the induced voltage test with partial discharge ...