Detection and localisation of internal defects in insulating system of power transformers

With the development of both fast and low cost analog to digital converters (ADC) and new mathematical procedures for waveform description, such as “Time Encoded Signal Processing And Recording” (TESPAR), new possibilities to detect and localize internal defects in insulating systems of power transformers become feasible if the following requirements are fulfilled: (1) the equivalent circuit of the insulating system for fast partial discharge (PD) signal propagation (ns time range) is known, (2) the measured response of the insulating system to the PD signal injected at least at three different positions of each winding (top, center, bottom) are calculated or measured at the signal tap-off points (i.e. bushings) and (3) the pattern matrix of all calculated or measured responses exist (encoded and processed signals with TESPAR) as a reference. In this contribution the above mentioned requirements for quasi simultaneous detection and localization of internal defects in insulating systems of power transformers is discussed. The application of this method for PD-measurements of real power transformers is presented