Turn-to-Turn Fault Protection for Power Transformers
2016
Jevgeņijs Kozadajevs

Defending
11.02.2016. 13:00, Rīga, EEF, Āzenes iela 12/1 -306.

Supervisor
Aleksandrs Dolgicers

Reviewers
Virginijus Radziukynas, Antans Sauļus Sauhats, Aleksandrs Gavrilovs

A critical analysis of the condition of the field of electrical engineering points to the need to considerably increase the reliability of power transmission and distribution, which is observed in many studies and official documents. This is mainly due to the increase in the number of serious emergencies, which cause large economic losses worldwide. The probability of emergencies is largely determined by the operating conditions. At the conditions of market economy and shortage of electric power, electric power companies in some regions operate electric equipment in the maximum operating modes, which are close to the critical modes. This is stimulated by the development and growing implementation of new means of intensive electric equipment control, which have been insufficiently studied yet. Doubtlessly, such operation leads to faster wear and tear of part of electric equipment and a decrease in the reliability of the power supply system as a whole. This acquires special topicality with regard to equipment that is close to the end of its normative service life or has exceeded it. At present, the power industry experiences wide use of transformer equipment: power transformers, controllable shunt reactors. It is natural that the reliability of the operation of power networks is in many ways determined by the reliability of the transformer equipment. Out of the total number of emergencies, about 10 % is made up by transformer faults, which cause considerable economic losses. This is due to the fact that an emergency repair of a high-capacity transformer requires considerable financial means and time. Besides, in most cases after a fire emergency, a transformer cannot be repaired at all but the ensuing emergency expert examination fails to reveal the initial cause of the fault due to the large amount of damage; thus, it is not possible to make the required structural changes, the goal of which is to increase the reliability of the power equipment. During planned repairs of transformer equipment, it is also complicated to evaluate the condition (the remaining service life) of the insulation; therefore, increased requirements are set regarding the reliability and effectiveness of means of relay protection and diagnostics. Considerable attention has been paid to the development of the relay protection, automation and control systems of transformers by G. Atabekov, A. Bulychev, V. Vanin, A. Dmitrenko, A. Drozdov, A. Dyakov, A. Zasypkin, S. Kuzhekov, M. Lint, V. Nagay, V. Novash, E. Podgorny, A. Fedoseyev, Y. Ulyanitsky, E. Shneyerson and many others. 6 The main attention when solving the task of increasing the effectiveness of transformer protection means is paid to differential protection. The degree of its technical accomplishment and the reliability of its operation are mainly determined by the quality of input data. In this connection, one of the possible ways of its development is the improvement of the metrological characteristics of the measuring equipment and development of methods that take into account the dynamic properties of the measurements. The accuracy of the measurements of current transformers, taking into account the non-linearity of their parameters, is a vital task. The paper is dedicated to the development of new methods of discerning minimum internal faults of power transformers, which will make it possible to ensure reliable operation of protection devices at early stages of such faults. The possibility to integrate the new methods into existing protection devices will make it possible to increase the effectiveness and reliability of protection devices without additional costs due to the otherwise required purchase of expensive equipment.


Keywords
Transformators, differenciāla aizsardzība

Kozadajevs, Jevgeņijs. Turn-to-Turn Fault Protection for Power Transformers. PhD Thesis. Rīga: [RTU], 2016. 134 p.

Publication language
Latvian (lv)
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