HiDry72: Short-circuit withstand test upon the biggest ever dry-type power transformer

The article considers the results of the analysis of autotransformers operation mode monitoring. The time diagram of active load current and oil temperature of autotransformer TashTES AT-3 is established and during one year changes of these variables and basic parameters of autotransformer were observed. Technical faults of the power transformer and high power autotransformer are established and methods of their elimination are determined. Damage of transformers and autotransformers with voltage of 110-500 kV of about 30% of the total number of outages which were accompanied by internal short-circuits and two main causes of damage were determined. The main causes of technological failures, which were not accompanied by internal short-circuits, are as follows: 20% of failures in operation of the onload tap-changer, 16% of oil leaks from the bushings, 13% of oil leaks and lowering of oil from the transformer due to violation of welded joints and rubber seals, 4% of engine damage to oil pumps of the cooling system, 3% of pressure increase in high-voltage hermetic bushings, 2% of film protection shell damage. The main reasons of technological violations accompanied by internal short-circuit in the transformer are as follows: breakdown of internal insulation of highvoltage bushings, insufficient short-circuit resistance, wear and tear of winding insulation, breakdown of insulation.

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Frequency and time fault diagnosis methods of power transformers

Measurement Science Review ◽

10.1515/msr-2018-0023 ◽

2018 ◽

Vol 18 (4) ◽

pp. 162-167 ◽

Cited By ~ 13

Author(s):

Miroslav Gutten ◽

Daniel Korenciak ◽

Matej Kucera ◽

Richard Janura ◽

Adam Glowacz ◽

...

Keyword(s):

Fault Diagnosis ◽

High Voltage ◽

Impact Test ◽

Power Transformer ◽

Short Circuit ◽

Small Deformation ◽

Short Circuit Current ◽

Diagnostic Methods ◽

Response Analysis ◽

Short Circuit Currents

Abstract The authors describe experimental and theoretical analyses of faults of power transformer winding. Faults were caused by mechanical effect of short-circuit currents. Measurements of transformer were carried out in high-voltage laboratory. Frequency and time diagnostic methods (method SFRA - Sweep Frequency Response Analysis, impact test) were used for the analyses. Coils of transformer windings were diagnosed by means of the SFRA method and the time impact test. The analyzed methods had a significant sensitivity to a relatively small deformation of coil. In the analysis a new technique for analyzing the effects of short-circuit currents is introduced. This technique is developed for high-voltage transformers (different types of power). The proposed analyses show that it is necessary to analyze the value of short-circuit current. Short-circuit current represents a danger for the operation of the power transformer. The proposed approach can be used for other types of transformers. Moreover, the presented techniques have a potential application for fault diagnosis of electrical equipment such as: transformers and electrical machines.

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On Simplified Calculations of Leakage Inductances of Power Transformers

Energies ◽

10.3390/en13184952 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4952 ◽

Cited By ~ 1

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.

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