Application of Probabilistic Neural Networks Using High-Frequency Components’ Differential Current for Transformer Protection Schemes to Discriminate between External Faults and Internal Winding Faults in Power Transformers

Internal and external faults in a power transformer are discriminated in this paper using an algorithm based on a combination of a discrete wavelet transform (DWT) and a probabilistic neural network (PNN). DWT decomposes high-frequency fault components using the maximum coefficients of a ¼ cycle DWT as input patterns for the training process in a decision algorithm. A division algorithm between a zero sequence of post-fault differential current waveforms and the differential current coefficient in the ¼ cycle DWT is used to detect the maximum ratio and faults. The simulation system uses various study cases based on Thailand’s electricity transmission and distribution systems. The simulation results demonstrated that the PNN and BPNN are effectively implemented and perform fault detection with satisfactory accuracy. However, the PNN method is most suitable for detecting internal and external faults, and the maximum coefficient algorithm is the most effective in detecting the fault. This study will be useful in differential protection for power transformers.

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A Review on the Reclamation Technologies for Service-Aged Transformer Insulating Oils

Indonesian Journal of Electrical Engineering and Computer Science ◽

10.11591/ijeecs.v10.i2.pp426-435 ◽

2018 ◽

Vol 10 (2) ◽

pp. 426

Author(s):

Sharin Ab Ghani ◽

Zulkarnain Ahmad Noorden ◽

Nor Asiah Muhamad ◽

Hidayat Zainuddin ◽

Mohd Aizam Talib

Keyword(s):

Service Life ◽

Distribution Systems ◽

Power Transformer ◽

Test Methods ◽

Standard Test ◽

Chemical Degradation ◽

Power Transformers ◽

Electrical Insulator ◽

The World ◽

Transmission And Distribution

Power transformers are the backbone of electricity transmission and distribution systems throughout the world. The price of power transformers is exorbitant (costing millions of dollars per unit) and therefore, frequent maintenance is necessary to ensure that these systems are highly reliable during their operation. The service life of mineral insulating oils is typically 30 to 40 years for power transformer applications. However, all insulating oils (regardless of their type) are subjected to thermal, electrical and chemical degradation, which will deteriorate the oil-paper insulating system and consequently reduce the capability of the oil as an electrical insulator. For these reasons, service-aged insulating oils are treated by two types of processes (i.e. reclamation and reconditioning) in order to prolong the service life of these oils. Reclamation (regeneration) is used to treat insulating oils with high levels of acidity and sludge. In this paper, a brief review on the reclamation technologies used to treat service-aged insulating oils is presented, covering various aspects such as the standard test methods that need to be complied with, the types of adsorbents used to reduce acidity and sludge of the used insulating oils, as well as the findings of several key studies related to the evaluation of the effectiveness of the reclamation process. This review will indeed benefit researchers and practitioners in this field since it provides an overall picture of the recent progress in reclamation technologies for service-aged transformer insulating oils

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A New Hybrid Protection Algorithm for Protection of Power Transformer Based on Discrete Wavelet Transform and ANFIS Inference Systems

International Journal of Emerging Electric Power Systems ◽

10.1515/ijeeps-2017-0248 ◽

2018 ◽

Vol 19 (3) ◽

Author(s):

A.M. Salama ◽

K. M. Abdel-Latif ◽

Mohamed M. Ismail ◽

S. M. Mousa

Keyword(s):

Wavelet Transform ◽

Response Time ◽

Discrete Wavelet Transform ◽

Power Transformer ◽

Power Transformers ◽

Discrete Wavelet ◽

Inference System ◽

Matlab Simulink ◽

Inference Systems ◽

High Degree

Abstract This paper presents a new protection algorithm for power transformers. The new algorithm is based on Discrete Wavelet Transform (DWT) and (ANFIS) Inference System. The simulation of power transformer is done using BCTRAN subroutine of ATP software to simulate the internal faults cases. The protection algorithm using DWT and ANFIS is implemented MATLAB Simulink software. The new Algorithm is tested on 40/40/15 MVA, 220/70/11.5 KV power transformer. The proposed algorithm satisfies high degree of accuracy and faster response time.

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A discrete wavelet transform approach to discriminating among inrush current, external fault, and internal fault in power transformer using low-frequency components differential current only

IEEJ Transactions on Electrical and Electronic Engineering ◽

10.1002/tee.21971 ◽

2014 ◽

Vol 9 (3) ◽

pp. 302-314 ◽

Cited By ~ 1

Author(s):

Atthapol Ngaopitakkul ◽

Chaiyan Jettanasen

Keyword(s):

Wavelet Transform ◽

Discrete Wavelet Transform ◽

Power Transformer ◽

Low Frequency ◽

Discrete Wavelet ◽

Inrush Current ◽

Internal Fault ◽

Frequency Components ◽

Differential Current

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On-Line Condition Monitoring for Power Transformers Based on UHF PD Measurements

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.614-615.1158 ◽

2012 ◽

Vol 614-615 ◽

pp. 1158-1162

Author(s):

Ming Jun Liu ◽

Jian Zhang Zou ◽

Qiu Kuan Zhou ◽

Yang Lin Li ◽

Nian Ping Yan

Keyword(s):

Monitoring System ◽

High Frequency ◽

Power Transformer ◽

Partial Discharge ◽

High Sensitivity ◽

Power Transformers ◽

Simulated Experiment ◽

Envelope Detection ◽

On Line ◽

Line Condition

An on-line monitoring system based on ultra high frequency (UHF) partial discharge (PD) measurements was developed for power transformers. The UHF PD signals were coupled by a UHF sensor and preprocessed by peak envelope detection technique. The system has high sensitivity, strong ability of interference suppression and well real-time capability according to the simulated experiment in lab and field test of a power transformer. Experimental results showed that the forepart PD faults could be discovered by the analysis of UHF PD signals. The on-line monitoring system has already been applied on a power transformer for years.

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On-Line Partial Discharge Monitoring System for Power Transformers Based on the Simultaneous Detection of High Frequency, Ultra-High Frequency, and Acoustic Emission Signals

Energies ◽

10.3390/en13123271 ◽

2020 ◽

Vol 13 (12) ◽

pp. 3271 ◽

Cited By ~ 2

Author(s):

Wojciech Sikorski ◽

Krzysztof Walczak ◽

Wieslaw Gil ◽

Cyprian Szymczak

Keyword(s):

Acoustic Emission ◽

Monitoring System ◽

High Frequency ◽

Power Transformer ◽

Partial Discharge ◽

Power Transformers ◽

Ultra High Frequency ◽

On Line ◽

Simultaneous Use ◽

Dielectric Window

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 measurement (IVPD). Next, it was installed on a 31.5 MVA substation power transformer and integrated according to the standard IEC 61850 with SCADA (Supervisory Control and Data Acquisition) system registering voltage, active power, and oil temperature of the monitored unit. The obtained results showed high sensitivity of the manufactured PD sensors as well as the advantages of the simultaneous use of three techniques of PD detection and the possibility of discharge parameter correlation with other power transformer parameters.

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A Solid-State On-Load Tap Changer for the Power Transformers of 10—0.4 kV Distribution Networks

Vestnik MEI ◽

10.24160/1993-6982-2020-3-82-90 ◽

2020 ◽

Vol 6 (6) ◽

pp. 82-90

Author(s):

Dmitriy I. Panfilov ◽

◽

Mikhail G. Astashev ◽

Aleksandr V. Gorchakov ◽

◽

...

Keyword(s):

Solid State ◽

Physical Model ◽

High Speed ◽

Power Transformer ◽

Voltage Control ◽

Power Transformers ◽

Control Algorithms ◽

Load Voltage ◽

Tap Changer ◽

Load Tap Changer

The specific features relating to voltage control of power transformers at distribution network transformer substations are considered. An approach to implementing high-speed on-load voltage control of serially produced 10/0.4 kV power transformers by using a solid-state on-load tap changer (SOLTC) is presented. An example of the SOLTC circuit solution on the basis of thyristor switches is given. On-load voltage control algorithms for power transformers equipped with SOLTC that ensure high reliability and high-speed operation are proposed. The SOLTC performance and the operability of the suggested voltage control algorithms were studied by simulation in the Matlab/Simulink environment and by experiments on the SOLTC physical model. The structure and peculiarities of the used simulation Matlab model are described. The SOLTC physical model design and its parameters are presented. The results obtained from the simulating the SOLTC operation on the Matlab model and from the experiments on the SOLTS physical model jointly with a power transformer under different loads and with using different control algorithms are given. An analysis of the experimental study results has shown the soundness of the adopted technical solutions. It has been demonstrated that the use of an SOLTC ensures high-speed voltage control, high efficiency and reliability of its operation, and arcless switching of the power transformer regulating taps without load voltage and current interruption. By using the SOLTC operation algorithms it is possible to perform individual phase voltage regulation in a three-phase 0.4 kV distribution network. The possibility of integrating SOLTC control and diagnostic facilities into the structure of modern digital substations based on the digital interface according to the IEC 61850 standard is noted.

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The Heating System of Agricultural Facilities Using Excess Heat Power Transformers

Elektrotekhnologii i elektrooborudovanie v APK ◽

10.22314/2658-4859-2020-67-1-42-47 ◽

2020 ◽

Vol 67 (1) ◽

pp. 42-47

Author(s):

Anatoliy I. Sopov ◽

Aleksandr V. Vinogradov

Keyword(s):

System Design ◽

Heat Supply ◽

Cooling System ◽

Power Transformer ◽

Electric Heating ◽

Heating System ◽

Power Transformers ◽

Large Power ◽

Excess Heat ◽

Power Centers

In power transformers, energy losses in the form of heat are about 2 percent of their rated power, and in transformers of large power centers reach hundreds of kilowatts. Heat is dissipated into the environment and heats the street air. Therefore, there is a need to consume this thermal energy as a source of heat supply to nearby facilities. (Research purpose) To develop methods and means of using excess heat of power transformers with improvement of their cooling system design. (Materials and methods) The authors applied following methods: analysis, synthesis, comparison, monographic, mathematical and others. They analyzed various methods for consuming excess heat from power transformers. They identified suitable heat supply sources among power transformers and potential heat consumers. The authors studied the reasons for the formation of excess heat in power transformers and found ways to conserve this heat to increase the efficiency of its selection. (Results and discussion) The authors developed an improved power transformer cooling system design to combine the functions of voltage transformation and electric heating. They conducted experiments to verify the effectiveness of decisions made. A feasibility study was carried out on the implementation of the developed system using the example of the TMG-1000/10/0.4 power transformer. (Conclusions) The authors got a new way to use the excess heat of power transformers to heat the AIC facilities. It was determined that the improved design of the power transformer and its cooling system using the developed solutions made it possible to maximize the amount of heat taken off without quality loss of voltage transformation.

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Multi-focus Image Fusion Using an Effective Discrete Wavelet Transform Based Algorithm

Measurement Science Review ◽

10.2478/msr-2014-0014 ◽

2014 ◽

Vol 14 (2) ◽

pp. 102-108 ◽

Cited By ~ 36

Author(s):

Yong Yang ◽

Shuying Huang ◽

Junfeng Gao ◽

Zhongsheng Qian

Keyword(s):

Wavelet Transform ◽

Image Fusion ◽

Discrete Wavelet Transform ◽

High Frequency ◽

Low Frequency ◽

Objective Evaluation ◽

Discrete Wavelet ◽

Evaluation Indexes ◽

Fused Image ◽

Focus Image

Abstract In this paper, by considering the main objective of multi-focus image fusion and the physical meaning of wavelet coefficients, a discrete wavelet transform (DWT) based fusion technique with a novel coefficients selection algorithm is presented. After the source images are decomposed by DWT, two different window-based fusion rules are separately employed to combine the low frequency and high frequency coefficients. In the method, the coefficients in the low frequency domain with maximum sharpness focus measure are selected as coefficients of the fused image, and a maximum neighboring energy based fusion scheme is proposed to select high frequency sub-bands coefficients. In order to guarantee the homogeneity of the resultant fused image, a consistency verification procedure is applied to the combined coefficients. The performance assessment of the proposed method was conducted in both synthetic and real multi-focus images. Experimental results demonstrate that the proposed method can achieve better visual quality and objective evaluation indexes than several existing fusion methods, thus being an effective multi-focus image fusion method.

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