Alternative Capacitive Coupling Method for Wideband PD Measurements on Generator Windings

Inhalt:
Online measurement of Partial Discharge (PD) activity is an established monitoring technology for assessing the condition of the generator stator winding insulation system. During the past 20 years, several equipment manufacturers have offered measurement systems based on various methods, of which the electrical measurement of PD signals has become the most widely used. There are also several different types of sensors available for coupling the PD signals out of the machine. The result is a variety of different signal frequency ranges, pulse detection methods, and optimized measuring circuits being utilized for each type of sensor. The prevalence of each technology is to some extent dependent on regional markets and preferences, and their respective differences continue to be extensively discussed by experts within the field. This paper presents results from investigation into the applicability of Stator Slot Couplers(TM) (SSC) for capacitive coupling with standard wideband PD measurement systems. Results from laboratory and field measurements demonstrate the opportunities and limitations of this non-conventional method.