scholarly journals Diagnosis winding short-circuit faults of power transformer

2018 ◽  
Vol 8 (2) ◽  
pp. 70-78
Author(s):  
Rekik Badri ◽  
Labar Hocine
Keyword(s):  
Power Transformer ◽  
Short Circuit ◽  
Power Transformers ◽  
Vector Diagram ◽  
Distribution Grid ◽  
The Core ◽  
Reliable Detection ◽  
Coupled Circuits ◽  
Base Data ◽  
Diagram Analysis

Diagnostic goal of transformers in service is to detect the winding or the core in fault. Transformers are valuable equipment which makes a major contribution to the supply security of a power system. Consequently, it is of great importance to disequilibria the three phases courant of power transformers. So, vector diagram Analysis is useful tool for reliable detection of incipient mechanical fault in a transformer, by finding winding or core defects. The authors propose this article, the coupled circuits method, because, it gives most possible exhaustive modelling of transformers. Measurement courant homopolaire in order to improve and simplify the response for à faults transformer.This study can be useful as a base data for the other transformers of the same categories intended for distribution grid.  Keywords—Diagnostic; Short-Circuit; Transformer Faults; unbalanced current.

scholarly journals On Simplified Calculations of Leakage Inductances of Power Transformers

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4952 ◽  
Author(s):  
Tadeusz Sobczyk ◽  
Marcin Jaraczewski
Keyword(s):  
Power Transformer ◽  
Short Circuit ◽  
Power Transformers ◽  
Stray Field ◽  
Good Representation ◽  
The Finite Element Method ◽  
Leakage Inductance ◽  
Leakage Flux ◽  
Calculation Results ◽  
Discrete Differential Operator

This paper deals with the problem of the leakage inductance calculations in power transformers. Commonly, the leakage flux in the air zone is represented by short-circuit inductance, which determines the short-circuit voltage, which is a very important factor for power transformers. That inductance is a good representation of the typical power transformer windings, but it is insufficient for multi-winding ones. This paper presents simple formulae for self- and mutual leakage inductance calculations for an arbitrary pair of windings. It follows from a simple 1D approach to analyzing the stray field using a discrete differential operator, and it was verified by the finite element method (FEM) calculation results.

scholarly journals Novel Remanence Determination for Power Transformers Based on Magnetizing Inductance Measurements

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4616
Author(s):  
Chen Wei ◽  
Xianqiang Li ◽  
Ming Yang ◽  
Zhiyuan Ma ◽  
Hui Hou
Keyword(s):  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Power Transformer ◽  
Power Transformers ◽  
Inrush Current ◽  
The Core ◽  
Novel Method ◽  
Simulation Results ◽  
Electro Magnetic ◽  
The Relationship

The remanence (residual flux) in the core of power transformers needs to be determined in advance to eliminate the inrush current during the process of re-energization. In this paper, a novel method is proposed to determine the residual flux based on the relationship between residual flux and the measured magnetizing inductance. The paper shows physical, numerical, and analytical explanations on the phenomenon that the magnetizing inductance decreases with the increase of residual flux under low excitation. Numerical simulations are performed by EMTP (Electro-Magnetic Transient Program) on a 1 kVA power transformer under different amounts of residual flux. The inductance–remanence curves are nearly the same when testing current changes. Laboratory experiments conducted on the same transformer are in line with the numerical simulations. Furthermore, numerical simulation results on a 240 MVA are reported to demonstrate the effectiveness of the proposed method.

An Innovative Solution for Type Testing of Power Transformers

2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Manohar Singh ◽  
Vishnuvarddhan Telukanta ◽  
K S Meera
Keyword(s):  
Power Transformer ◽  
Short Circuit ◽  
Operating Conditions ◽  
Power Transformers ◽  
Test Facility ◽  
Online Testing ◽  
Testing Laboratory ◽  
Power Testing ◽  
Grid Operation ◽  
The Impact

Abstract Type tests are essential to assess the short circuit withstand capabilities of transformer windings. The mechanical durability of power equipment are checked against the mechanical forces developed during making/breaking short circuit operations. These type tests are generally carried out in indoor transformer test laboratories. Testing of Power Transformer for size more than 200 MVA in 765/400 kV voltage class in an indoor laboratory is not economically feasible. Now a days, power transformer manufacturers are fabricating single phase auto- power transformers of size up to 630 megawatt volt ampere (MVA) rating. Type testing of these transformers in indoor laboratories is not feasible. In view of this, strong short circuit fault feeding capabilities of the national grids can be utilized for type testing of these power transformers in an online manner. However, this may affect the grid operation/control during weak grid operating conditions. Recently, National High Power Testing Laboratory is established for testing of power transformer upto of 630 MVA. This is a unique online transformer test facility for testing of 765/400/220/132 kV class power transformers. An offline simulation has been carried out in this article, to assess the impact of online type testing on the Indian National grid. In this article, an online testing scheme has been presented which enables the national grid operator to analysis the prevailing grid condition & subsequently to decide the safe rating of the power transformer for online testing. The simulated results are cross checked with field results and it is found that simulated results are close to actual field results. The concurrence of simulated and field results helped in successfully commissioning of the testing laboratory.

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 ANALYSIS OF CONSTRUCTION PRINCIPLES AND FUNCTIONALITY OF HIGH-VOLTAGE POWER TRANSFORMER CONDITION MONITORING SYSTEMS

2020 ◽  
pp. 61-70
Author(s):  
O. Ye. Pirotti ◽  
O. I. Balenko ◽  
V. O. Brechko ◽  
M. Yu. Huzin ◽  
Ju. G. Gontar
Keyword(s):  
High Voltage ◽  
Power Transformer ◽  
Short Circuit ◽  
Power Transformers ◽  
Electrical Network ◽  
Characteristic Functions ◽  
Economic Losses ◽  
Monitoring Systems ◽  
Measuring Instruments ◽  
Continuous Control

The article presents the results of analysis of construction principles and functionality of systems used to monitor the condition of high-voltage power transformers. The main functions of modern monitoring systems used to diagnose the condition of electrical network equipment both in Ukraine and abroad were analysed. Based on the analysis it was found that the most characteristic functions of monitoring systems are the detection of rapidly developing defects and continuous control of parameters necessary to predict and assess the state of equipment. It is shown that efficiency of monitoring systems will be determined by both accuracy of measuring instruments and adequacy of prediction and diagnostic models used in the process of measurement results processing. Requirements to the equipment which observance allows providing effective and economically reasonable use of monitoring systems are considered. The typical architecture of modern monitoring systems is analysed, the basic elements of such systems are considered. Basic levels of information flow processing within the systems for monitoring the condition of power transformers have been considered. A detailed description and justification for using diagnostic parameters for monitoring the main components of power transformers such as dissolved gases analysis, partial discharges, current, voltage and power of transformers, oil temperature in different transformer locations, switching and atmospheric overvoltages, short-circuit currents, deformation of windings and others are presented. The output parameters returned by monitoring systems are given. The introduction of modern systems and technical means of monitoring the condition of high-voltage power transformers will reduce the risks of emergencies and, consequently, reduce the economic losses associated with the replacement of damaged transformers and under-release of electrical energy.

scholarly journals DETERMINATION OF “WEAK” BY POWER TRANSFORMERS RELIABILITY OF POWER SYSTEMS ACCORDING TO THE RESULTS OF FAILURE RISK ASSESSMENT UNDER EXTERNAL SHORT CIRCUITS

2021 ◽  
Author(s):  
Eugeniy I. Bardik ◽  
Mykola P. Bolotniy ◽  
Yaroslav S. Koval
Keyword(s):  
Mathematical Model ◽  
Risk Assessment ◽  
Power System ◽  
Electric Power ◽  
Power Transformer ◽  
Short Circuit ◽  
Electric Power System ◽  
Power Transformers ◽  
Electrical Network ◽  
Failure Risk

Background. The increase of technological violation intensity and its consequences severity is caused mainly by objectively existing aging and service life depletion of electrical equipment. The power industry liberalization exacerbates the reliable operation problem of the power system and requires identification of power system operation accompanied by the maximum emergency risk with possible cascade accidents development. Therefore, the model development task for assessment of the equipment failure risk based on the diagnostic results of technical condition in particular under short circuit in the external network is relevant today. Objective. The aim of the work is to develop a fuzzy mathematical model for probability assessment of power transformer failure in the presence of a windings defect, short circuit in external network and emergency risk assessment under power transformers out of service. Methods. The fuzzy set theory and fuzzy logic were used for developing a mathematical model of risk assessment of power trans- former failure. The problems of determining the “weak” in terms of power transformers reliability of power systems based on the results of failure risk assessment due to external short circuits were solved by methods of fuzzy logic and probabilistic-statistical simulation of electric power system modes. Results. The necessity of complex simulation of electric power system modes is substantiated for probability assessment of power transformer failure under electrical network disturbances. The simulation of technical condition of power transformer windings was carried out. The short circuit influence on operability level of power transformers of electric power system was investigated. The quantitative indicators of operational risk of electric power system were determined under power transformers out of service. Conclusions. The linguistic mathematical model for estimating the failure probability of power transformer windings in the presence of defect and short circuit in electrical network has been developed to determine the quantitative indicators of emergency risk in power system.

Influence of Active Part Stiffness on Radiated Sound Power Level in Power Transformers

2019 ◽  
Author(s):  
Cassiano C. Linhares ◽  
João S. Costa ◽  
Ricardo E. R. Teixeira ◽  
Cristiano P. Coutinho ◽  
Sérgio M. O. Tavares ◽  
...  
Keyword(s):  
Power Transformer ◽  
Power Level ◽  
Low Frequency ◽  
Dynamic Mechanical Properties ◽  
Active Part ◽  
Power Transformers ◽  
Radiated Noise ◽  
The Core ◽  
Stiffness Properties ◽  
Directional Component

Abstract Power transformers are associated with the radiation of unwanted noise in many circumstances due to its low frequency and relative high power, which reduction and mitigation is imperative. It is known that the main source of this noise are originated by the vibrations induced in the active part, namely the core, primarily due to electromagnetic forces and magnetomechanical effects. On the other hand, the laminated design of the core is indispensable in order to reduce the Foucault currents losses. Thus, in addition to the electrical requirements, the development of an appropriate model of the core dynamic behavior taking into account its segmented structure is urgent, in order to avoid resonances at any of the excitation frequencies. In the current proceeding, the influence of the core equivalent dynamic mechanical properties on a power transformer radiated noise was studied by performing a numerical parametric analysis. It was concluded that the active part stiffness properties, namely the directional component related to the out of lamination plane bending, ruled the vibroacoustic behavior of the transformer for the studied frequency range.

Experimental Study on Short-Circuit Withstand Capability of 110kV Power Transformer

2014 ◽  
Vol 672-674 ◽  
pp. 848-853
Author(s):  
Chao Wei ◽  
Peng Wu ◽  
Yun Cai Lu
Keyword(s):  
Experimental Study ◽  
Power Transformer ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Assessment Method ◽  
Power Transformers ◽  
Experimental Scheme ◽  
Strong Current ◽  
Technological Level ◽  
Current Value

Short-circuit withstand capability test of transformers is mechanical strength withstand test under strong current imposed on power transformers, which is a kind of assessment method of comprehensive technical capabilities and technological level of transformer manufacturing. This paper analyzes the theory basis of short-circuit withstand capability test and calculates the imposed short-circuit current value and provides experimental scheme which is verified by the testing. All is to verify the ability to withstand a short circuit of 110kV power transformer.

On Developing the Theory of Resonant Processes in Power Transformer Windings. Part 1. Frequency Responses of a Circuit with Two PI Sections

2021 ◽  
pp. 49-55
Author(s):  
Vasily S. LARIN ◽  
Keyword(s):  
Equivalent Circuit ◽  
Power Transformer ◽  
Short Circuit ◽  
Natural Oscillation ◽  
Power Transformers ◽  
Equivalent Circuits ◽  
Electrical Networks ◽  
Frequency Responses ◽  
Voltage Resonance ◽  
Resonant Processes

The windings of power transformers are complex oscillatory circuits. Their natural oscillation frequencies range from a few to hundreds of kHz, and under unfavorable conditions they can coincide with the frequencies of transient voltage oscillations in electrical networks caused by switching operations and short circuit faults in cable lines. The development of electrical networks and the technical solutions that have come in wide use in recent years give rise to a situation in which the cases of damage to the insulation of power transformer windings resulting from resonant overvoltages are increasingly more frequently encountered during operation. An attempt is made in the article to develop the theory of resonant processes in the windings of power transformers. The frequency responses of voltages and currents in a simplified equivalent circuit of the power transformer winding are considered. Analytical expressions are obtained for the admittances of individual parts of equivalent circuits and the voltages at intermediate nodes, as well as expressions for the natural frequencies of the equivalent circuits considered. It is shown that the resonant growth of voltage in the transformer windings results from the voltage resonance caused by the presence of the winding’s own inductance and capacitance with respect to ground. By analyzing the frequency dependences of the admittances of equivalent circuit individual parts, the conditions and frequency ranges in which voltage resonance may occur are shown.

Numerical Analysis on Short-Circuit Force Parameters of Windings for Power Transformer

2011 ◽  
Vol 138-139 ◽  
pp. 764-769
Author(s):  
Jian Jun Liu ◽  
Jian Min Wang ◽  
Chong You Jing ◽  
Chang Zai Fan ◽  
Yuan Zhai
Keyword(s):  
Magnetic Field ◽  
Numerical Analysis ◽  
Power Transformer ◽  
Short Circuit ◽  
Strength Test ◽  
Power Transformers ◽  
Simplified Model ◽  
Leakage Magnetic Field ◽  
Set Up ◽  
Short Circuit Condition

The Simplified model of both calculating leakage magnetic field and mechanical force of windings at short circuit condition for a 120MVA/220kV power transformer is set up. The leakage magnetic field ‚ short-circuit force and stress in transformer windings are analyzed and their distributing characteristics are acquired respectively by using FEM. The calculation method and results are validated by withstanding short circuit strength test of the product. A number of useful suggestions are given for design of power transformers.

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