Identification of Vibration Sparks in a Large Hydrogen-Cooled Generator Winding

The time domain-frequency domain characteristics of turbo-generator coil-to-core and packing-to-core Vibration Sparks (VS) can be determined and compared to known Partial Discharge (PD) and other non-VS discharge characteristics. The accurate characterisation of VS events is significant in the identification of this degradation mechanism in the slots of large generators. In this paper a new equivalent circuit, expressing the theoretical mechanism of VS involving a Side Ripple Spring (SRS) as a packing material in hydrogen-cooled machines, is presented. This is a variation of the direct coil-to-core air-cooled equivalent circuit model presented elsewhere. Furthermore an experimental circuit of a stator bar and SRS will be used to generate VS in order to determine their time domain-frequency domain characteristics. These can then be compared to those of PD and other non-VS type discharges using a cluster diagram to deduce if the phenomenon can be discriminated successfully in air-cooled and hydrogen-cooled turbo-generators.