Table 3 lists the maintenance strategies, courtesy of
Eskom Distribution [8].The results of these routine
tests during commercial operation will be the
measures for the for the development of the PHI.
During the wear-out stage of the equipment life
cycle, a point will be reached where the equipment
can no longer be maintained cost-effectively, and
thus a decision for replacement is undertaken. This isdepicted by the saw-tooth behaviour (hazard
function) illustrated in Fig. 5[3].