Partial Discharge Localization in a Power Transformer: Methods, Trends, and Future Research
TL;DR: The techniques of PD localization used so far are compared, and their advantages and limitations are pointed out, to help develop the future technologies for PD localization thereby avoiding insulation damage.
Abstract: This paper presents a comprehensive review of various techniques of partial discharge (PD) localization. The technologies reviewed are acoustic, ultra-high frequency (UHF), optical, and electrical according to their chronological order of development. The paper outlines the distinctive acoustic and UHF sensors, along with the algorithm for the localization of PD source. Various digital signal processing and statistical techniques applied are likewise discussed. A substantial effort has been given to electrical methods since they represent the most active and current field of PD research. In this paper, the techniques of PD localization used so far are compared, and their advantages and limitations are pointed out. The challenges and trends in future research in PD localizations are also discussed. The review given in this paper will be useful to develop the future technologies for PD localization thereby avoiding insulation damage. Thus, this paper is intended to serve as a guide for the research ...
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TL;DR: The aim of this review was to present state-of-the-art UHF sensors in PD detection and facilitate future improvements in the UHF method.
Abstract: Condition monitoring of an operating apparatus is essential for lifespan assessment and maintenance planning in a power system. Electrical insulation is a critical aspect to be monitored, since it is susceptible to failure under high electrical stress. To avoid unexpected breakdowns, the level of partial discharge (PD) activity should be continuously monitored because PD occurrence can accelerate the aging process of insulation in high voltage equipment and result in catastrophic failure if the associated defects are not treated at an early stage. For on-site PD detection, the ultra-high frequency (UHF) method was employed in the field and showed its effectiveness as a detection technique. The main advantage of the UHF method is its immunity to external electromagnetic interference with a high signal-to-noise ratio, which is necessary for on-site monitoring. Considering the detection process, sensors play a critical role in capturing signals from PD sources and transmitting them onto the measurement system. In this paper, UHF sensors applied in PD detection were comprehensively reviewed. In particular, for power transformers, the effects of the physical structure on UHF signals and practical applications of UHF sensors including PD localization techniques were discussed. The aim of this review was to present state-of-the-art UHF sensors in PD detection and facilitate future improvements in the UHF method.
73 citations
Cites background from "Partial Discharge Localization in a..."
...To date, several review works related to PD detection based on UHF measurement have been conducted in recent years in terms of signal processing [3], localization [14,15], and pattern recognition [3]....
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TL;DR: A brief introduction of PD phenomena along with the causes and effects is presented, and distinctive sensors and technologies based on acoustic, ultra-high-frequency, electric, and hybrid methods are outlined.
Abstract: Insulation degradation is one of the prime reasons for failures in power transformers. Partial discharge (PD) is considered as one of the primary causes of initiation of insulation degradation. Thus, monitoring of PD in a power transformer at a preliminary stage is the most important task to prevent any catastrophic failure. This paper presents a brief introduction of PD phenomena along with the causes and effects. Various topics of contemporary research related to PD, such as modelling, detection, measurement, and classification, are grouped under different headings with exhaustive up-to-date bibliography. The paper outlines distinctive sensors and technologies based on acoustic, ultra-high-frequency, electric, and hybrid methods. The techniques are compared, and their advantages and limitations are pointed out. The techniques of denoising of PD signal based on signal processing, artificial intelligence, and statistical analysis are summarised. The challenges and trends in future PD research are ...
42 citations
Additional excerpts
...Recently in [1], we have presented the various techniques of localisation of the PD sources in a power transformer....
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TL;DR: In this paper, the authors present a review of Fiber Bragg Grating (FBG) sensors' application as a sensor for partial discharge monitoring in an oil-filled power transformer.
Abstract: Power transformer is one of the most important high voltage apparatus in any power system network. The life span of such apparatus commonly relies upon its insulation condition. The primary reason for an insulation breakdown is partial discharge. Partial discharges (PDs) are electrical discharges that happen in the insulation system of the transformers. Occurrence of PDs results in deterioration of the transformer insulation system. Hence, measuring and detecting the PD at an initial stage is necessary to avoid complete breakdown of the transformer. Currently, various PD detection and measurement methods, such as, electrical, chemical, acoustic, UHF and optical methods are being used for PD monitoring in power transformers. The conventional PD monitoring techniques like electrical or chemical have some limitations. The optical Fiber Bragg Grating (FBG) Sensor has been used as a PD sensor for PD monitoring in the power transformer to overcome these issues. This paper presents a review of FBG sensors’ application as a sensor for PD monitoring in an oil-filled power transformer. The challenges and future prospects in this area are also discussed.
29 citations
TL;DR: The proposed UHF PD antenna is fabricated and measured and the results show that it provides good impedance matching, realized gain, radiation pattern, and circular polarization.
Abstract: In this work, a circularly-polarized ultra-high frequency (UHF) partial discharge (PD) antenna is proposed to detect the PD in 0.6 GHz - 1.7 GHz. The proposed PD antenna consists of an Archimedean spiral antenna, a balun, and a cavity. The Archimedean spiral antenna is embedded by FR-4 as substrate and superstrate for miniaturization. The microstrip-to-paired strips balun is designed to yield good performance in the return loss, insertion loss, and amplitude and phase imbalances which are of great necessity for low axial ratio. The cavity is employed to obtain unidirectional radiation patterns and prevent external signal interference. However, it is found that the originally-designed cavity-backed antenna does not work properly near 1.35 GHz due to resonance phenomena in the cavity. In this work, the cavity is modified to tackle this problem. The proposed UHF PD antenna is fabricated and measured and the results show that it provides good impedance matching, realized gain, radiation pattern, and circular polarization.
25 citations
Cites background from "Partial Discharge Localization in a..."
...In contrast with the external sensor, the internal sensor has several main advantage such as high signal-to-noise ratio, high sensitivity, and anti-interference [1]–[4]....
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TL;DR: In this article, a comprehensive review about the application of signal processing and machine learning technologies in UHF PD detection and diagnosis is presented, which is divided into three categories according to their respective purpose, which are the preprocessing technology, source localization technology and pattern recognition technology.
Abstract: Partial discharge (PD) detection and diagnosis based on the ultra-high frequency (UHF) signals is one of the most widely adopted methods to evaluate the internal insulation status of high voltage equipment. Benefit from the rapid development of computing hardware and data processing algorithms, the intelligent PD fault diagnosis method based on the UHF data has made considerable progress in the past two decades. This two-part paper aims to give a comprehensive review about the application of signal processing and machine learning technologies in UHF PD detection and diagnosis. These technologies are divided into three categories according to their respective purpose, which are the preprocessing technology, source localization technology and pattern recognition technology. As the first one of the two-part review, we focus on the preprocessing and localization approaches in this paper. Specifically, for the preprocessing topic, the methods for signal denoising, multi-source separation, and pulse segmentation are included. While for the localization topic, the time difference of arrival (TDOA) method, direction of arrival (DOA) method, received signal strength indicator (RSSI) method, and other latest methods are reviewed. For each topic, the basic ideas, recent research progresses, advantages and limitations are discussed in detail. Before the conclusion, we also make a discussion about the application effects of the above technologies and prospect some future directions accordingly. In the second paper, the pattern recognition problems based on the UHF PD data will be concentrated, especially the application of deep learning algorithms.
24 citations
References
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TL;DR: In this article, the authors proposed an approach to estimate the arrival times of acoustic partial discharges (PD) signals in a power transformer by using robust direct solvers instead of the previously used iterative algorithms.
Abstract: The measurement of partial discharges (PD) is a non-destructive and sensitive diagnostic tool for the condition assessment of insulating systems. Two major tasks of PD measurements may be distinguished, (i) PD detection, hence providing evidence and the type of the PD and (ii) the location of the PD. The question "Where is the PD source?" is amongst others tremendously important for scheduling and starting maintenance/repair actions cost and time efficiently or to perform a risk analysis. Here the possibility to geometrically localize the flaw, by means of arrival times of acoustic PD signals, gets an extremely interesting option. Precise acoustic arrival times are consequently essential to accurately locate PD in a power transformer. The averaging of acoustic PD signals helps to enhance the acoustic sensitivity. The acoustic detection limit is lowered significantly and the determination of the arrival times is made possible for weaker PD. Supplementary steps, like automatic objective arrival time determination or additional wavelet-based de-noising further improve the overall location accuracy. A new location approach works with pseudo-times and allows for the use of robust direct solvers instead of the previously used iterative algorithms.
365 citations
TL;DR: In this article, three different methods of acquiring the time differences of arrival (TDOA) from the PD waveforms are discussed, including the first peak of the signal as the arrival instant, or from the cross-correlation of the PD signal waveforms, or by applying the similarity function to the plots of PD signals cumulative energy.
Abstract: The location of a partial discharge (PD) source inside a transformer can be determined from the time differences of arrival (TDOA) between signals that are captured by an array of UHF sensors. The TDOA can be acquired from the received PD waveforms. In this paper, three different methods of acquiring the TDOA from the PD waveforms are discussed. The time difference can be calculated either by taking the first peak of the signal as the arrival instant, or from the cross-correlation of the PD waveforms, or by applying the similarity function to the plots of the PD signals cumulative energy. Computation algorithms for determining the TDOA automatically are introduced so that possible bias from human interpretation is avoided. The presence of noise and its effect on the accuracy of the PD localization will also be presented. Experimental results show the first-peak method has higher accuracy than the two other methods. The application of signal denoising further improves the localization accuracy.
133 citations
"Partial Discharge Localization in a..." refers background in this paper
...A comparison of three different techniques for estimating the TDOA of EM signals to sensors is discussed in [11]....
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TL;DR: In this paper, acoustic emission-based partial discharge source location has been applied successfully to power transformers in both factory and field environments, and this method is becoming an established test procedure with a high success rate.
Abstract: Acoustic emission-based partial discharge source location has been applied successfully to power transformers in both factory and field environments, and this method is becoming an established test procedure with a high success rate. With the aid of local utilities and utility laboratories that use acoustic emission apparatus daily, we expect further advances in this technology and an improved basis for determining suitable application conditions.
107 citations
"Partial Discharge Localization in a..." refers background in this paper
...A multichannel acoustic emission (AE) instrument measures the acoustic waves coming from the PD source to the multiple sensors located at different points on the tank, and the PD source is located in three dimensions by triangulation algorithm [2]....
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TL;DR: In this paper, the authors investigated the use of SWTFs for supervising the conditions of transformer units and proposed a method based on traveling wave theory to search for the optimum parameters of a partial differential equation.
Abstract: Statistical studies have shown that failures of bushings, winding insulation, and online tap changers are the main causes for long-duration outages of transformers. This article investigates the development of an instrument for supervising the conditions of transformer units. The use of sectional winding transfer functions (SWTFs) for online PD evaluation in power transformers has several advantages: localization of PD sources, discrimination between PDs inside or outside of the transformer, and evaluation of actual PD amplitudes along the winding. Direct measurement of SWTFs-when different points along the coil are accessible-and use of these SWTFs for PD evaluation and localization has shown excellent results. In order to use this method at transformers on site, an appropriate modeling method is needed for the computation of the SWTFs using only measurements at the transformer terminals. A detailed modeling approach based on discrete RLC circuit elements has been studied and different algorithms used for parameter estimation and optimization. This model is applicable in practical cases for a limited frequency range if genetic algorithms (GAs) are used for parameter optimization. A new method based on traveling wave theory has been investigated using genetic algorithms to search for the optimum parameters of a partial differential equation that describes the transient behavior of the coil. This method has shown potential in solving SWTF calculation problems for different transformers.
97 citations
"Partial Discharge Localization in a..." refers methods in this paper
...The PD input signal can be located from the output winding response measured at the bushing and neutral, and the sectional winding transfer functions (SWTFs) derived from the winding model [22]....
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TL;DR: In this paper, a method for partial discharge (PD) source location in power transformers based on detecting electromagnetic (EM) radiation emitted from PD is presented. But the problem of partial discharge location by EM waves is the difficulty in getting the accurate time arrivals of the signals from the source to multiple sensors.
Abstract: This paper presents a method for partial discharge (PD) source location in power transformers based on detecting electromagnetic (EM) radiation emitted from PD. The key problem of PD location by EM waves is the difficulty in getting the accurate time arrivals of the signals from the source to multiple sensors. Several measures are taken to improve the time arrival resolution. Firstly, a measuring frequency band (1 GHz-5 GHz) within RF band is proposed to accurately pick up the fast rise time of the signals. Secondly, an antenna array with diamond-shaped configuration is designed to improve the correlation coefficient of the waveforms from multiple sensors. Thirdly, two antenna arrays are proposed to eliminate the influences of the EM wave scattering caused by the iron core. Fourthly, an algorithm is proposed to increase the signal to noise ratio and to measure the time arrivals automatically through cross-correlation and averaging operation. Lastly, a hyperboloid-genetic algorithm is developed to search the PD source. Experiments on a single-phase transformer model were conducted in the laboratory. The tested results proved the validity of the proposed method and showed that the location error in 16 cm, mostly is about several cm
91 citations
"Partial Discharge Localization in a..." refers background in this paper
...The problem of improving the resolution of time arrival is discussed in [10]....
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