VALIDITY OF NARROW AND BROAD-BAND PD-MEASUREMENTS ON POWER TRANSFORMERS - PULSE DEFORMATIONS

Extensive investigations of partial discharge (pd) pulse winding response characteristics have revealed considerable physical insight into the mechanics of pulse transfer from within the windings to the externally accessable points of measurement. Based on the IEC charge measuring method, pd-pulse response profiles were investigated on both, layer- and disc-type transformers of different original size (25 MVA, 40 MVA and 1100 MVA) by means of internal pd-pulse injections at geometrically and electrically differing sites. The winding design and the pd-source locations influence significantly the externally measurable pd-magnitude and pulse form. By no means and by neither broad band (BB) or narrow band (NB) method of detection is it possible to correlate externally measured apparent charge values with the dissipated charge at the pd-source location. NB and BB instruments are equally applicable, with some preference to NB for pd-measurements on power transformers.