Fig. 1 illustrates that if we know the condition; we
can extract more out of the equipment, and are
positioned to time the replacement at a point in the
life cycle just before intolerable risk.
Reliability Approach
0
20
40
60
80
100
120
5 10 15 20 25 30 35 40 45
Age
Reliability %
Replacement
with Age
Reliability
Prediction
Fig. 1: Equipment reliability.
Beyond the intended investment period of 25 years, a
revised maintenance strategy or intervention can be
applied to preserve the equipment performance. In the
case of transformers, more frequent samples of
insulating oil in order to investigate sources of sudden
deteriorated health, and moisture extraction are
justified in order to establish possible causes of
thermal faults. Typical “life extension” interventions
for transformers include filtering or regeneration of
the main tank oil, partial re-winding or bushing
replacement.
Often circuit breakers need to be serviced more
frequently for deteriorated performance of overhead
line (frequency of faults). The effects include reduced
dielectric strength during arcing, increased wear of
finger contact and fatigue of the circuit breaker
mechanism. Retrofitting strategies have to be applied
on a case-by-case basis given all the enhancements
available in the last 10 years i.e. internal arc
protection, remote switching and pressure venting
technology.
In the end, all power plant and control plant have an
expected life span