Summary
The frequency response analysis (FRA) has become widely used to assess the mechanical and electrical condition of power transformers and shunt reactors. The FRA measurement method has been developed and standardized at the level of standards IEC, IEEE, etc. However, despite its long-term use, FRA interpretation remains subjective, and the accuracy of the
Read more Read less"diagnosis" is determined by the experience of the experts.
The interpretation of FRA measurements and the detection of transformer defects are based on comparisons of frequency responses obtained from two consecutive measurements, as well as measurements on adjacent phases or transformers of the same type. The comparison of frequency responses using correlation analysis and indexes showing the difference over a wide frequency range has become widespread. Despite its simplicity, this approach, based on integral indicators, does not allow one to take into account the specifics of the object under measurement and interpreting the type and location of the defect.
The report provides a practical example of assessing the technical condition of a 533 MVA single-phase generator step-up transformer in which internal damage occurred during shortcircuit withstand test. An approach to the interpretation of the FRA measurement results based on the analysis of the windings natural oscillation frequencies and the calculation of traditional diagnostic parameters such as short-circuit impedance and inductance, as well as turn ratio is presented.
The results of calculation of the frequency responses of winding conductance, impedance and inductance, formulas for the implementation of these calculations in measuring systems, as well as a comparison with the results of direct measurements of diagnostic parameters are presented. The results of numerical modelling of frequency responses using high-frequency models of power transformer are presented.
It is shown that the use of FRA along with additional measurement schemes makes it possible to provide a more complete condition assessment of power transformers and obtain traditional diagnostic parameters with sufficiently high accuracy without using other diagnostic equipment. Thus, FRA can be considered as a tool for rapid diagnostics in cases where it is necessary to quickly and comprehensively assess the condition of power transformers.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | A2_11160_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Russian Federation |
| Study committees | |
| File size | 1 MB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
LARIN Vasily - VEI – branch of RFNC-VNIITF; MATVEEV Daniil - MPEI; FROLOV Mikhail - MPEI; KURNYSHOV Roman - VEI – branch of RFNC-VNIITF; LESIN Boris - SVEL – Power transformers; GUREV Denis - SVEL – Power transformers; KOZHEVIN Alexey - SVEL – Power transformers; ABRAMOV Vasily - SVEL – Power transformers
Keywords
Power transformers, windings, frequency response analysis, condition assessment
