Testing of Partial Discharges in Generator Coil Bars with the Help of Calibrated Acoustic Emission Method

Abstract

Investigation results of acoustic emission signals coming from partial discharges within chosen generator coil bar, in relation to measurement results of apparent charge introduced by partial discharges sources, are presented in the article. Analysis is based on amplitude distributions calculated for acoustic emission signals, ordered at different measuring points for different values of the supply voltage. In order to assign acoustic emission signal to its advance degree a descriptor named by an acronym ADP (defined by authors) is calculated for each amplitude distribution. Descriptor families describing acoustic emission signals measured at particular measuring points (for different supply voltages) are presented in relation to apparent charge introduced by acoustic emission sources. These families concerning acoustic emission signals, measured at different measuring points for identical supply voltage, enable us to locate acoustic emission sources with maximum activity.

Analysis of Properties Characteristic for Acoustic Emission Signals Recorded On-Line in Power Oil Transformers

“…Recorded AE signals have been put to filtration within the band of 110-200 kHz, and next basic characteristics, amplitude distributions and AE descriptor with an acronym ADC [1][2][3][4][5] were worked up. Basing on kriging method, the descriptor maps on lateral walls of trans- Positions of measuring points in the measuring network are also marked on the maps.…”

“…Author's method used to analyze AE signals [1][2][3][4][5][6], applied to signals recorded in power oil transformers, enables us to elaborate the method how to investigate AE signals in power oil transformers which includes successively: recording of signals, calculation of amplitude distributions of signals, calculation of defined AE descriptors, working up of descriptor maps on lateral walls of transformer tanks, location of AE sources according to these maps by means of the method of maximum loudness (modified by the authors), and analysis of properties characteristic for signals recorded at points lying in the vicinity of identified sources. Presented stages of analysis are realized repeatedly within different frequency bands which enable to distinguish signals coming from different types of sources such as partial discharges (PD), Barkhausen's effect, oil circulation, and outer acoustic interferences.…”

“…In order to investigate transformers an author's measuring system called AE DEMA-COMP [1][2][3][4][5][6] was applied; such a system has been equipped with AE sensors D9241A type, produced by Euro Physical Acoustic Corporation. Investigations concern two oil power transformers with transformer ratio of 120/20/6 kV and rated power of 25 MVA.…”

Vibroacoustic Measurements in a Transient State οf Transformer Operation

“…There is also an analysis method of the transformer construction vibrations, the so-called classical vibroacoustic method [1,7,8], which consists in vibration measurement and analysis of the object under study during its regular operation. Nevertheless, the above-given measurement methods enable identification of the cases only of an extreme loosening of the active part elements.…”

The Application of the Correlative Analysis and the Regression Function for Determining Correlations οf the Measurement Results of Acoustic Emission Generated by Partial Discharges

“…The paper describes the dependence between the changes of the voltage supplying the spark-gap modeling partial discharges (PDs) on indeterminate potential particles moving in insulation oil and the values of selected descriptors calculated for the amplitude spectrum of the acoustic emission (AE) pulses generated [1][2][3][4][5][6][7][8][9][10]. It is a simple type relation, which is characteristic of a unilateral influence of the cause, which is the voltage changes, on the result, which are the value changes of the descriptors under study.…”