Methodology to Estimate the Risk of Vibration Sparking (Spark Erosion)

Opposite to a slot Partial Discharges (PD), Vibration Sparking (VS) or “spark erosion” is to some extent scarcely known even though it is a fast deterioration mechanism and service failure in a relatively short time – just a few years of operation - have been reported. It is driven by the airgap flux in the core and can occur at any point of the winding, including at the neutral side. Vibration sparking requires 2 fundamental conditions to be generated: (i) the presence of an induced parasitic current flowing along the conductive slot coating of the bar/coil because the coating is much more conductive than “normal”; (ii) vibration of that bar/coil within the slot because the bar/coil must be loose in the slot and vibrating under the magnetic forces. VS is generated from repeated…