Vasily Ya. Ushakov - Transformer Condition Control: Advanced and Traditional Technologies

Electrical power has been the technological foundation of industrial societies for many years. Although the systems designed to provide and apply electrical energy have reached a high degree of maturity, unforeseen problems are constantly encountered, necessitating the design of more efficient and reliable systems based on novel technologies. The book series Power Systems is aimed at providing detailed, accurate and sound technical information about these new developments in electrical power engineering. It includes topics on power generation, storage and transmission as well as electrical machines. The monographs and advanced textbooks in this series address researchers, lecturers, industrial engineers and senior students in electrical engineering.

**Power Systems is indexed in Scopus**

More information about this series at http://www.springer.com/series/4622

Translation from the Russian language edition: Original Title by Vasily Ya. Ushakov, et al., The author 2020. Published by Original Publisher. All Rights Reserved.

This Springer imprint is published by the registered company Springer Nature Switzerland AG

The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

The United Nations (UN), the International Energy Agency (IEA), the European Energy Charter, and other supranational and national structures related to the problem of meeting a growing need of mankind for electrical energy, name among the most serious challenges the aging of the entire power infrastructure and, primarily, the aging of electric power grids (EPG). Power transformers are one of the most complex in design, expensive, and widespread elements of EPG. For example, the total number of power transformers in all voltage classes (except instrument transformers) as a whole across the Unified National Power Grid (UNPG) and Distribution Grid Companies (DGC) of Russia amounted as of 2011 to 643.3 thousand units, their installed capacity being 832.6 thousand MVA. The total capacity of power transformers in Russian power systems of all voltage classes above 3 kV is currently 66.5 times higher than the installed capacity of all power plant generators due to a technological need for several stages of voltage transformation in the process of electricity transmission and distribution. The main part of transformers (in terms of quantity) consists of transformers with voltage up to 20 kV (94.7%), which are installed most entirely in distribution networks that serve agricultural purposes. The UNPG facilities account for about 0.8% of transformers in terms of quantity, and for about 37.8% in terms of capacity, while the DGC facilities account for 99.2% of transformers in terms of quantity and 62.2% in terms of capacity. Of the total number of power transformers installed in UNPG networks with voltage of 110 kV and higher, 55.3% of the units have exhausted their resource (as of 01.01.2012), with the accepted standard resource of service life for basic electrotechnical equipment being 25 years.

Despite such comprehensive CDT, sudden transformer failures continue to occur directly after an inspection issuing an act granting further operation. The reason for this to happen is the presence of hidden defects undetectable by regulatory diagnostic procedures. These defects include, for instance, displacement of winding coils relative to each other in different directions: axial and radial shifts, coil lowering, and other displacements. Any shift leads to an increase in the electric field strength between the shifted coils, and then to a subsequent speedup of insulation degradation in this locality, eventually causing a breakdown.