STATISTICAL BASED AN INVESTIGATION OF FAILURE OF POWER TRANSFORMERS AND REACTORS (original) (raw)

High Power Transformers Failures due to Flow Electrification: Tools for Understanding the Electrostatic Hazard

Flow electrification phenomenon is suspected to be responsible for some failures in high power transfo rmers. Acoustic sensor surveys from suspected transformers and visual observations in damaged transformers revealed some evidences of electrical discharges (electric "tree" paths, "w orm holes", presence of carbon ...) on inner pressboards. Never theless the scenario, which lays the electrostatic activity and consequently transformer failure, is still not well understood. The goal of this work is to propose some elements for understanding electrostatic hazards in high power transformers. Experimental set up has been developed in our laboratory to study flow electrification of oil at a pressboard r ectangular duct. As in power transformers, the oil/pressboard couple is insulated from the ground by an oil volume. Pressboard potential, accumulated charges on pressboard surface are recorded and correlated to charge leakage.

Power Transformer Tank Rupture and Mitigation—A Summary of Current State of Practice and Knowledge by the Task Force of IEEE Power Transformer Subcommittee

IEEE Transactions on Power Delivery, 2009

Ten presentations made by members of the IEEE Task Force on Transformer Tank Rupture and Mitigation over a course of four Transformer Committee meetings have been summarized. The task force was established in 2005 with an aim to review the current state of practice and knowledge for transformer tank rupture and mitigation, as well as to determine if this issue has been adequately covered by existing IEEE standards. The mechanics of transformer tank rupture, current IEEE standards on this issue, as well as various methods for preventing or mitigating tank rupture were presented and discussed. There were 81 registered members in the Task Force. The aim of this paper is to provide a description of all existing methods and technologies to prevent or mitigate transformer tank rupture. The paper does not endorse any particular product or method.

A Nonlinear Finite-Element Analysis Tool to Prevent Rupture of Power Transformer Tank

Sustainability

High-energy internal failures of transformers are catastrophic events which are hardly predictable. For this reason, a full-scale controlled experiment represents a valuable learning opportunity to gather accurate information about sequence of events during the very short time in which the failure occurs. Controlled parameters include tank design, material properties, experimental load and measurements. In this paper, we present a detailed investigation using nonlinear finite-element analysis of a 210-MVA transformer high-pressure experiment. We begin by evaluating the relationship between internal arcing pressure rise and tank expansion characteristics. Since this relationship is not linear due to geometric and material nonlinearities, an iterative process is proposed to ensure result accuracy. Stress–strain material properties are retrieved by tension experiments of specimens extracted from the tested tank to enable accurate comparison of numerical and experimental results. It is ...

Transformer Failures , Causes & Impact

Study of transformers, the faults that most commonly occur, the causes of these faults and their impact is conducted and discussed in this paper. The transformers that were studied were stepdown transformers (11kv-220v) used by WAPDA in distribution sectors. Data about the transformer failure for the last 5 years was collected from PESCO for two locations of Peshawar district. The first region was the metropolitan area of University Town and the second was the suburb area of Ragi-Lalma. Comprehensive data mining was done to investigate the cause of failures.

ANALYSIS THE REASONS OF 110 kV TRANSFORMERS BREAK DOWN AND THE METHODS OF ITS DIAGNOSTICS

Vestnik of Kazan State Agrarian University, 2018

The article deals with the diagnostics of power transformers by different methods. Particular attention is paid to modern methods and diagnostic tools that maximally allow to determine the state of the transformer. Based on the statistical processing of the results of the research, the authors indicate that the most common failures are: damage to the windings of transformers with the possibility of regulation under load, without disconnecting power and leaving consumers without power supply (RPN) for any period of operation. The greatest number of damages for transformers with on-load tap-changers with a service life of 10-30 years, for high-voltage bushings after 10 years of operation. The most severe damage to the transformer is an internal short circuit (short circuit). These types of overvoltage cause damage to the windings in 80% of the total number of damage, high-voltage bushings - 89%, RPN - 25% and other elements - 36%. It is indicated that a serious consequence occurs when...

International Journal of Engineering Technology Research & Management ACOUSTIC PRESSURE LEVEL MECHANICAL VIBRATION ANALYSIS OF A TRANSFORMER MODEL

The paper presents the results of vibration acoustic investigations and the measurements of the acoustic pressure measurment (noise) of a transformer model. The analyses were taken at a full transformer load in following operation steps: at a producer packeted core and at unpacketed core. Unpacketing consisted in loosing the screws pressing the particular core plates. Mechanical vibrations were observed and the acoustic pressure level was identify and measured. The vibration acoustic analysis results are presented in the form of frequency spectrum and the results of the acoustic analysis of the transformer under study are shown by determining corrected values of the acoustic pressure level and by a frequency analysis.

Transmission of Vibrations from Windings to Tank in High Power Transformers

Energies

This article presents a step-by-step methodology for calculating transformer tank vibrations caused by electromagnetic forces. This approach uses 3D finite element models for both magnetic and structural calculations. Particular attention was paid to the description of momentum transfer between structural and fluid areas of the transformer. The actual geometry of the coils in the phase windings was taken into account. The dominant role of the axial component of the Lorentz force is the main conclusion of the article. The results are given in the form of three-dimensional displacement fields of the transformer tank presented together with the acoustic pressure field in the oil. The theoretical analysis is verified by laser-scanned vibration patterns on the tank wall.

Detection of arc faults in transformer windings by transient signal analysis

Research Square (Research Square), 2024

In power and distribution transformers, lightning strikes, switching operations, short-circuits and other reasons can cause deterioration of the winding insulation, resulting in arcing between the windings. The arcing event is very important in transformers and if it is detected late, it can cause a rigid short circuit and burn the transformer and even cause the transformer to explode due to heating and pressure. In this study, the effects of arcing between transformer windings on transformer end current and voltage waves are analysed and arcing is determined. In the study, a 15 MVA power transformer was modelled in three dimensions in the Ansys@Maxwell environment and the arc model created in Matlab@Simulink was adapted to the Ansys magnetic model and the arc in the transformer windings as a result of synchronous operation was analysed. The transient regime effects of arcing at 5 different points in the same high voltage winding of the transformer on the current and voltage waves at the input terminals of the transformer are analysed to obtain data that allow the fault to be detected in a short time without the use of sensors. The data obtained from the transformer input was transformed into the frequency domain using Fast Fourier Transform (FFT), and the high-frequency transient regime signals occurring in the transformer under arcing fault conditions were detected from these signals. Using the method proposed in the study, it is possible to detect the occurrence of arcing in the transformer.

REVIEW OF FAULTS IN TRANSFORMERS

IJEAST, 2022

The focus of this paper is to classify different types of disturbances/faults in transformers, their protection schemes.