Interpretation of the Results of a Non-Destructive Method for Evaluating the State of Power Transformer’s Winding
Alexander Yu. Khrennikov *
Scientific Department, Scientific & Technical Center of Federal Grid Company of United Energy System, Russian electrical networks, Kashirskoe highway, 22/3, 115201 Moscow, Russia.
Nikolay M. Aleksandrov
SPE Dynamics, 6 Anisimova str., 428000, Cheboksary, Russia.
*Author to whom correspondence should be addressed.
Abstract
A review of the regulatory documentation governing the analysis of the state of the windings of power transformers by the frequency response method (SFRA) DL 911/2004, CIGRE A2.26 WG Brochure, IEC 60076-18, IEEE C57/147 is presented. Formulas and equations for calculating indicators for numerical comparison of normograms and defectograms are given to provide the analysis of winding state. A summary table with a comparison of damage types and a range of frequency response is presented. An example of an analysis of the winding of a power transformer with the presence of deformation of the winding as a result of testing it for electrodynamic resistance to short circuit currents is also given. The research results of 400 MVA 220 kV transformer testing showed that any change in the frequency response (SFRA) corresponds to significant deformations of the windings. As shown above by the example of diagnosing the state of transformer windings between short-circuit shots at Short-circuit Laboratory, the use of frequency analysis is quite effective.
Keywords: Transformer, deformation, frequency response, SFRA, diagnostics, interpretation