Development of Operation and Diagnostic Algorithm Complex for Technical Condition Assessment of Power Transformers in Permissible Risk Circumstances

2021 ◽  
Author(s):  
◽  
Gints Poišs
Keyword(s):  
Power Transformer ◽  
Diagnostic Algorithm ◽  
Condition Index ◽  
Technical Condition ◽  
Transmission System ◽  
Diagnostic Methods ◽  
Data Availability ◽  
Power Transformers ◽  
Risk Level ◽  
Data Set

A power transformer is a key unit in the transmission system, and its cut-off can impact both consumers and the general stability of the system. Therefore, it is an important tool for processing the operational and technical condition data to quantify them as the technical condition index (TCI). Based on the technical condition of the power transformer, the TCI enables objective and reasoned decisions on the future investments related to replacement or repairs of transformers. Thus, by using the TCI, the service life of the transformer can be safely extended, since the identified risks have been recognized and are being followed-up. The TCI method is useful for a power transformer park, because it allows easy identification of transformers that require most attention. A crucial precondition for this method is data availability, diversity, and regularity or frequency of data collection. These features (preconditions) may vary in different power transmission systems, and it creates the necessity for a tailored approach. The present Doctoral Thesis studies the diagnostic methods used in the transmission system in Latvia and the results thereof. Thus, it takes advantage of an already existing data set and flow to develop a TCI-based complex of algorithms for determining the risk level of high-power transformers in acceptable risk conditions.

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 ASSESS THE RISK LEVEL OF POWER TRANSFORMER DUE SHORT-CIRCUIT FAULTS BASED ON ANFIS

SINERGI ◽  
2019 ◽  
Vol 23 (2) ◽  
pp. 99
Author(s):  
Azriyenni Azhari Zakri ◽  
Mohd Wazir Mustafa ◽  
Hari Firdaus ◽  
Ibim Sofimieari
Keyword(s):  
Power Systems ◽  
Power Distribution ◽  
Fuzzy Inference ◽  
Power Transformer ◽  
Short Circuit ◽  
Electrical Power ◽  
Power Transformers ◽  
Risk Level ◽  
Electrical Machine ◽  
Intelligent Technique

A power transformer is an electrical machine that converts electrical power at different voltage levels. Faults, occur in power transformers, inhibit electrical power distribution to the consumer. Protection, therefore, of the power transformers is essential in power systems reliability. The power system can be reliable if the protection devices work well when there is a fault. A hybrid intelligent technique, which is a combination of Artificial Neural Network (ANN) and Fuzzy known as Adaptive Neuro-Fuzzy Inference Systems (ANFIS), was used in this research. The objective of this paper is the simulation of differential relays as a protection device on power transformers using Matlab/Simulink. Performance of differential relays for power transformers protection is carried out with internal and external fault scenarios. The input data were classified into three different input for ANFIS such as internal and external 1, internal and external 2, internal, external 1, and external 2, respectively. The error results of ANFIS training for the type of fault internal and external 1 is 9.46*10-7, and types of fault internal and external 2 is 1.09*10-6 internal, external 1 and external 2 are 8.59*10-7. The results obtained from the simulation were accurate and shows that the ANFIS technique is an efficient method that gives less error and a great value. Finally, the technique can minimize faults with power transformers. Finally, to prove this method can reduce faults in the power transformer, the assess of this model has been carried out through the RMSE that has been generated which is zero.

scholarly journals Methods for calculation of the marginal exploitation lifespan of power transformers 35 rV and higher based on the state index

2018 ◽  
Vol 58 ◽  
pp. 02006
Author(s):  
Alexandr Nazarychev ◽  
Dmitriy Andreev ◽  
Alexey Tadjibaev ◽  
Svetlana Vysogorets ◽  
Ilia Sulynenkov
Keyword(s):  
Initial Data ◽  
Condition Index ◽  
Technical Condition ◽  
The State ◽  
Technical State ◽  
Power Transformers ◽  
Integral Evaluation ◽  
The Real ◽  
State Index

A methods for determining the marginal exploitation lifespan of a transformer based on a complex diagnostic survey was developed. The integral evaluation of the technical state of the transformers is performed according to the value of the condition index. An example of the marginal exploitation lifespan calculation of the transformer according to the real initial data is given. The application of the methods will allow to proceed to the planning of technical re-equipment and reconstruction of energy facilities taking into account the technical condition of the equipment.

scholarly journals The Use of Generalized Gaussian Distribution in Vibroacoustic Detection of Power Transformer Core Damage

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2525
Author(s):  
Robert Krupiński ◽  
Eugeniusz Kornatowski
Keyword(s):  
Gaussian Distribution ◽  
Power Transformer ◽  
Vibration Signal ◽  
Technical Condition ◽  
Power Transformers ◽  
Generalized Gaussian Distribution ◽  
Core Damage ◽  
Vibroacoustic Diagnostics ◽  
Detector Output

Vibroacoustic diagnostics (VM—Vibroacoustic Method) is one of the methods for diagnosing the active part of power transformers. Measurement technologies have been refined over the past several years, but the methods of analyzing data obtained in VM diagnostics are still in development. In most cases, they are based on a simple frequency spectrum analysis, and the diagnostic conclusions are subjective and depend on the expert’s professional experience. The article presents an objective method for the detection of transformer unit core damage, based on the analysis of the statistical properties of the vibration signal registered on the surface of the tank of an unloaded transformer in the steady state of vibrations (VM). The algorithm for proceeding further is: FFT analysis of the vibroacoustic signal, with the determination of the relative changes in vibration power as a function of frequency P r ( f ) and, finally, the determination of the statistic properties of the dataset P r ( f ) . The Generalized Gaussian Distribution (GGD) is used to describe the P r ( f ) set. The detector output values are the λ and p parameters of the GGD distribution. These two numerical values form the basis for the classification of the technical condition of the transformer unit core. The correctness of the described solution was verified on the example of ten pieces of 16 MVA power transformers with different operating times and degrees of wear.

scholarly journals Predicting the technical condition of the power transformer using fuzzy logic and dissolved gas analysis method

2022 ◽  
Vol 12 (2) ◽  
pp. 1139
Author(s):  
Vladimir Mikhailovich Levin ◽  
Ammar Abdulazez Yahya ◽  
Diana A. Boyarova
Keyword(s):  
Fuzzy Logic ◽  
High Efficiency ◽  
Power Transformer ◽  
Thermal Power ◽  
Technical Condition ◽  
Electric Power System ◽  
Diagnostic Methods ◽  
Digital Model ◽  
Vibration Monitoring ◽  
Ratio Method

Power transformers are one of the most important and complex parts of an electric power system. Maintenance is performed for this responsible part based on the technical condition of the transformer using a predictive approach. The technical condition of the power transformer can be diagnosed using a range of different diagnostic methods, for example, analysis of dissolved gases (DGA), partial discharge monitoring, vibration monitoring, and moisture monitoring. In this paper, the authors present a digital model for predicting the technical condition of a power transformer and determining the type of defect and its cause in the event of defect detection. The predictive digital model is developed using the programming environment in LabVIEW and is based on the fuzzy logic approach to the DGA method, interpreted by the key gas method and the Dornenburg ratio method. The developed digital model is verified on a set of 110 kV and 220 kV transformers of one of the sections of the distribution network and thermal power plant in the Russian Federation. The results obtained showed its high efficiency in predicting faults and the possibility of using it as an effective computing tool to facilitate the work of the operating personnel of power enterprises.

Power Transformers Condition Assessment of GI Simangkuk Switchyard Sumatra Interconnection in Indonesia

2012 ◽  
Vol 452-453 ◽  
pp. 975-979 ◽  
Author(s):  
Josep Franklin Sihite ◽  
Takehisa Kohda
Keyword(s):  
Power Systems ◽  
Power Transformer ◽  
Electrical Power ◽  
Aging Effect ◽  
Diagnostic Methods ◽  
System Stability ◽  
Power Transformers ◽  
System Control ◽  
Electrical Power System ◽  
Power Utility

The electricity needs of Indonesia grow an average 10% each year. Therefore, PLN (Perusahaan Listrik Negara) as the only power utility business in Indonesia, has a master plan to develop new power plant, switchyard and transmission system. One of the new developed systems is GI Simangkuk switchyard of Sumatra interconnection system. This switchyard is prepared to improve reliability of Sumatra interconnection system. This site utilizes power transformers of 275 kV. Power transformer is one of the main equipments in power systems. When a failure occurs in a power transformer, the whole system will be failed and the electricity could not be delivered to customer. Each utility has to assure their reliability in order to maintain electrical power system stability by assessing transformer condition. There is an increasing need for better diagnostic and monitoring tools to assess the condition of transformers. Modern power transformers are equipped with software and computer system control. The reliability of this computer systems are needed to evaluate for assurance of system safety. This paper describes the need of assessment and maintenance of power transformers such as outages effect of failures, high cost of maintenance and replacement, increase of world demand, aging effect and used of old transformer, and computer protection system failure. Monitoring and diagnostic methods of transformers assessment have been developing in recently years. They can be separated into traditional and non-traditional methods that have been used in many years and are still in research stage. In this paper we propose a new approach in order to assess power transformer condition by using fault tree analysis.

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

Vestnik MEI ◽  
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.

The Heating System of Agricultural Facilities Using Excess Heat Power Transformers

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.

Financial distress determinants among SMEs: empirical evidence from Sweden

2020 ◽  
Vol 47 (3) ◽  
pp. 547-560 ◽  
Author(s):  
Darush Yazdanfar ◽  
Peter Öhman
Keyword(s):  
Financial Crisis ◽  
Financial Distress ◽  
Large Scale ◽  
Global Financial Crisis ◽  
Binary Logistic Regression ◽  
Data Availability ◽  
Cross Sectional ◽  
Data Set ◽  
Content Type ◽  
The Global Financial Crisis

PurposeThe purpose of this study is to empirically investigate determinants of financial distress among small and medium-sized enterprises (SMEs) during the global financial crisis and post-crisis periods.Design/methodology/approachSeveral statistical methods, including multiple binary logistic regression, were used to analyse a longitudinal cross-sectional panel data set of 3,865 Swedish SMEs operating in five industries over the 2008–2015 period.FindingsThe results suggest that financial distress is influenced by macroeconomic conditions (i.e. the global financial crisis) and, in particular, by various firm-specific characteristics (i.e. performance, financial leverage and financial distress in previous year). However, firm size and industry affiliation have no significant relationship with financial distress.Research limitationsDue to data availability, this study is limited to a sample of Swedish SMEs in five industries covering eight years. Further research could examine the generalizability of these findings by investigating other firms operating in other industries and other countries.Originality/valueThis study is the first to examine determinants of financial distress among SMEs operating in Sweden using data from a large-scale longitudinal cross-sectional database.

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