From the Editors´ Desk

The first article in this issue is "Partial Discharge Influence on Dissipation Factor Values During Stator-Bar Testing," by Contin at the University of Trieste, Italy, and Zhu at Powertech Labs in Vancouver, Canada. The article reports on simulation studies and laboratory experiments done to examine how partial discharge affects dissipation factor measurements of rotating machine insulation. The article shows that periodic partial discharge pulses generate a frequency spectrum whose fundamental frequency corresponds to power frequency, and the signals can interfere with dissipation factor values measured at power frequency. To demonstrate this, an artificial defect was made on a virgin stator bar to generate partial discharge signals. Both the simulated and measured partial discharge signals recorded from the bar at various voltage levels were studied, and the parameters of partial discharge signals that influence the dissipation factor values were investigated.