On 2 October 2006 immediately prior to return to service
the maximum ramp test voltage was 18 kV and after 5
months 20 kV in February 2007 (Table 6) reflecting much
fewer signs of defects in the form of tape separations. The
E/M (TVA) probe readings also improved during the same
period (Table 7). This suggests that elevated PD was
associated with tape separations from which moisture had
not yet been fully removed. Kettle Unit 4 operated
satisfactorily without reduction in its rating until a new
stator frame, core and winding, assembled in the service
bay, was placed in service in 2012.