Otkrivanje i analiza signala parcijalnih pražnjenja u energetskom transformatoru UHF metodom

2020 ◽  
Vol 22 (1-2) ◽  
pp. 96-101
Author(s):  
Đorđe Dukanac ◽  
Keyword(s):  
Detailed Analysis ◽  
Background Noise ◽  
Power Transformer ◽  
Partial Discharge ◽  
Spectral Composition ◽  
Partial Discharges ◽  
Power Transformers ◽  
Discharge Source ◽  
Useful Components

This paper presents the practical detection of partial discharge signals using a UHF sensor mounted on a power transformer and then the detailed analysis of a signal is done. The first part of the paper describes possible partial discharge sources in power transformers, UHF method and UHF sensor. In the second part of the paper, received signal at UHF sensor is considered. In order to accurately determine the magnitude of the partial discharge signal, especially if the location of the partial discharge source is far from the location of the UHF sensor, it is necessary to separate the signal from the background noise. This is only possible at intervals between individual bursts of the observed partial discharges. The spectral composition of the received signal is considered and a method for separating the present noise from the useful components of the partial discharge signal is established. The presumable main cause of partial discharges is evaluated.

FEM Simulation of PD Acoustic Signal Propagation in Transformers

2013 ◽  
Vol 448-453 ◽  
pp. 2278-2285
Author(s):  
Yue Dong ◽  
Yong Qian ◽  
Hai Feng Ye ◽  
Xiu Chen Jiang
Keyword(s):  
Power Transformer ◽  
Ultrasonic Method ◽  
Partial Discharge ◽  
Fem Simulation ◽  
Signal Amplitude ◽  
Signal Propagation ◽  
Ultrasonic Waves ◽  
Diagnostic Methods ◽  
Power Transformers ◽  
The Finite Element Method

In order to study propagation process of partial discharge ultrasonic signal in power transformer, the finite element method is used for simulation modeling and calculation. Ultrasonic waves can be activated by partial discharges (PD) in power transformers. The ultrasonic method is used for evaluating the insulation condition of power transformers by analyzing the partial discharge signals information which is detected by AE sensors. Compared with other diagnostic methods the AE method causes relatively low disturbance, and measuring apparatus is simple and easy to use. This technique is noninvasive and immune to electromagnetic noise. Simulate partial discharge sources of different positions respectively. Achieved results indicate that the space and time distributions of the acoustic pressure depend on the induction position. Furthermore, a greater pressure gradient is observed in domains with higher speed of sound while the signal amplitude decays when it moves away from the PD source.

scholarly journals Analysis of Operating Modes of Oil-Immersed Power Transformers with a Voltage of 10 (6) / 0.4 kV

2021 ◽  
Vol 24 (4) ◽  
pp. 80-91
Author(s):  
A.E. Fokeev ◽  
I.N. Tumakov
Keyword(s):  
Ambient Temperature ◽  
Thermal Aging ◽  
Power Transformer ◽  
Spectral Composition ◽  
Operating Conditions ◽  
Power Transformers ◽  
Load Factor ◽  
Calculation Algorithm ◽  
Load Current ◽  
Aging Rate

The rate of thermal aging of the power transformers windings insulation depends on the effects of the electric field, mechanical stresses, temperature and processes that cause changes in these factors. A calculation algorithm is considered that allows determining the temperature of the most heated point of the windings of an oil power transformer at known values of the load current and ambient temperature. Calculation of the most heated winding point temperature and the rate of thermal aging of insulation for an oil power transformer at different ambient temperatures during the year, different values and different spectral composition of the electric load current showed that in some cases it is possible to violate the permissible operating conditions of power transformers. According to the calculation results, the dependences of the thermal aging rate of insulation on the ambient temperature are constructed, with different load parameters and different load coefficients of power transformers. For the considered modes, in the warm season, the value of the thermal aging rate of insulation significantly exceeds the nominal value. Based on mathematical models of oil power transformers with natural and forced oil circulation, expressions are obtained for determining the coefficient of reduction of the oil power transformers permissible load when the ambient temperature exceeds the normal value of 20 °C. On the basis of these expressions, for practical use, the dependences of the coefficient of reduction of the permissible load on the ambient temperature are constructed. The influence of ambient temperature must be taken into account when choosing the power of oil power transformers, for which it is assumed to operate in full redundancy mode or high load factor values (³ 0.8) in normal mode. To ensure the normative service life of the insulation of the windings, it is necessary to determine the design power of oil power transformers using the coefficient of reduction of the permissible load under the influence of higher harmonics of the current and the coefficient of reduction of the permissible load under the influence of ambient temperature.

scholarly journals Development of Acoustic Emission Sensor Optimized for Partial Discharge Monitoring in Power Transformers

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1865 ◽  
Author(s):  
Sikorski
Keyword(s):  
Acoustic Emission ◽  
Partial Discharge ◽  
Low Noise ◽  
Partial Discharges ◽  
Power Transformers ◽  
Laboratory Research ◽  
Fully Differential ◽  
Peak Sensitivity ◽  
Optimal Material ◽  
Discharge Detection

The acoustic emission (AE) technique is one of the unconventional methods of partial discharges (PD) detection. It plays a particularly important role in oil-filled power transformers diagnostics because it enables the detection and online monitoring of PDs as well as localization of their sources. The performance of this technique highly depends on measurement system configuration but mostly on the type of applied AE sensor. The paper presents, in detail, the design and manufacturing stages of an ultrasensitive AE sensor optimized for partial discharge detection in power transformers. The design assumptions were formulated based on extensive laboratory research, which allowed for the identification of dominant acoustic frequencies emitted by partial discharges in oil–paper insulation. The Krimholtz–Leedom–Matthaei (KLM) model was used to iteratively find optimal material and geometric properties of the main structures of the prototype AE sensor. It has two sensing elements with opposite polarization direction and different heights. The fully differential design allowed to obtain the desired properties of the transducer, i.e., a two-resonant (68 kHz and 90 kHz) and wide (30‒100 kHz) frequency response curve, high peak sensitivity (−61.1 dB ref. V/µbar), and low noise. The laboratory tests confirmed that the prototype transducer is characterized by ultrahigh sensitivity of partial discharge detection. Compared to commonly used commercial AE sensors, the average amplitude of PD pulses registered with the prototype sensor was a minimum of 5.2 dB higher, and a maximum of 19.8 dB higher.

scholarly journals Partial discharges location in power transformers using piezoceramic sensors

2021 ◽  
Vol 11 (3) ◽  
pp. 1942
Author(s):  
B. Danouj ◽  
S. A. Tahan ◽  
E. David ◽  
M. Lotfi
Keyword(s):  
Partial Discharge ◽  
Spatial Localization ◽  
Flight Time ◽  
Partial Discharges ◽  
Electrical Machines ◽  
Ultrasonic Transducers ◽  
Power Transformers ◽  
Insulation System ◽  
New Generation ◽  
Published Paper

The detection and the spatial localization of partial discharges in high-voltage electrical machines are considered as an effective method in predictive maintenance that can provide valuable information on the health of the insulation system and allow to determine accurately the location of the risky insulation elements, which in turn will avoid any premature equipment’s deterioration by scheduling preventive maintenance action. After confirming in a previous published paper the efficiency of a new generation of piezoceramics sensors (high temperature ultrasonic transducers) to detect and characterize partial discharges, we are going to investigate, in this work, a second potential of this technology to locate the partial discharge sources by relying on its ability to detect acoustic signals emitted by partial discharge sources. We will present experimental results, demonstrating the effectiveness of these sensors to locate partial discharges sources and, we will also present an algorithm for calculating the partial discharge foci, based on the acoustic wave flight time.

A simple approach of partial discharge source location in high voltage cables

2017 ◽  
Vol 40 (12) ◽  
pp. 3507-3514
Author(s):  
Jose Ramírez-Niño ◽  
Carlos G Azcarraga ◽  
Alberth Pascacio ◽  
Rito Mijarez ◽  
Joaquin Rodríguez-Rodríguez
Keyword(s):  
Sensor Array ◽  
Partial Discharge ◽  
Source Location ◽  
Simple Approach ◽  
Propagation Direction ◽  
Partial Discharges ◽  
Power Cables ◽  
New Approach ◽  
Discharge Source ◽  
Incipient Faults

This article presents a new approach of partial discharges (PD) source location in power cables. The main advantage of this approach is the detection of the propagation direction of the PD. The method provides a pattern named by the authors PD+D, which, in contrast to the well–known phase-resolved partial discharge (PRPD) pattern, graphically shows the direction of PD propagation and uses the polarity of a sensor array on top of the magnitudes of the positive and negative parts of each PD pulse to detect the direction of propagation, is described in detail. The proposed technique is useful for the evaluation and diagnosis of power cables, since it can identify incipient faults. The attained results that demonstrate the value of this methodology and their scope and limitations are discussed.

scholarly journals Application of Acoustic Emission and Thermal Imaging to Test Oil Power Transformers

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5955
Author(s):  
Franciszek Witos ◽  
Aneta Olszewska ◽  
Zbigniew Opilski ◽  
Agnieszka Lisowska-Lis ◽  
Grzegorz Szerszeń
Keyword(s):  
Acoustic Emission ◽  
Thermal Imaging ◽  
Research Method ◽  
Power Transformer ◽  
Partial Discharges ◽  
Power Transformers ◽  
Imaging Studies ◽  
Ir Radiation ◽  
Side Walls ◽  
Ae Signals

In this paper, the research methodology and the results of the analysis carried out using the acoustic emission (AE) and thermal imaging for a selected oil power transformer are presented. The basis for the research, by means of the AE method, was the author’s patented research method. The AE descriptor maps on the side walls of the tested transformer along with the location of areas with increased AE activity and an analysis of the properties of AE signals recorded at the measurement points located in these areas have been performed. The results showed no partial discharges that could threaten further operation of the tested transformer as well as three areas where increased magnetoacoustic emission occurred. Thermal imaging studies were carried out in the 7.5 μm < λ < 13 μm band. Three areas were located on the calculated thermograms: the entire upper surface of the transformer tank and two areas on the side walls of the tested transformer in which increased IR radiation occurred. The results of the analysis of the research results for the two methods correspond with each other, having a common part, and complement each other giving a broader description of studied phenomena.

scholarly journals Impact of Power Transformer Oil-Temperature on the Measurement Uncertainty of All-Acoustic Non-Iterative Partial Discharge Location

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1385
Author(s):  
Vladimir Polužanski ◽  
Nenad Kartalović ◽  
Boško Nikolić
Keyword(s):  
Measurement Uncertainty ◽  
Power Transformer ◽  
Partial Discharge ◽  
Transformer Oil ◽  
Power Transformers ◽  
Acoustic Sensors ◽  
Temperature Variations ◽  
Discharge Location ◽  
The Mean ◽  
And Control

In this paper, the influence of the variation in transformer oil temperature on the accuracy of the all-acoustic non-iterative method for partial discharge location in a power transformer is researched. The research can improve power transformers’ testing and monitoring, particularly given the large transformer oil temperature variations during real-time monitoring. The research is based on quantifying the contribution of oil temperature to the standard combined measurement uncertainty of the non-iterative algorithm by using analytical, statistical, and Monte Carlo methods. The contribution can be quantified and controlled. The contribution varied significantly with different mutual placements of partial discharge and acoustic sensors. The correlation between the contribution and the mean distance between partial discharge and acoustic sensors was observed. Based on these findings, the procedure to quantify and control the contribution in practice was proposed. The procedure considers the specificity of the method’s mathematical model (the assumption that the oil temperature is constant), the non-iterative algorithm’s nonlinearity, and the large variations in transformer oil temperature. Existing studies did not consider the significant effect of the oil temperature on the combined measurement uncertainty of partial discharge location influenced by those phenomena. The research is limited to partial discharge located in the transformer oil.

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