Therefore, a rating out of 3 for each of the 9 tests is
developed. In this model, an average score is used for
the instances where multiples of equipment exists. In
the model itself, each individual piece of equipment is
managed.
Advantages:
Each piece of equipment will have an individual
PHI rating.
Simple scoring model to manage.
Disadvantages:
None.
• Health Measures for the 9-point Substation
PHI Model:
A Sub Score of 0-2 points mean that there are a
maximum of 2 test results that are of concern. We will
call this score a Good Rating. This is because we can
always expect WC and kV for an OLTC to deteriorate
with time. We have at least 2 routine tests defined per
Equipment.
Action would be: Investigate equipment performance
record and the work order feedback reported, and
action accordingly. Continue monitoring all other
Equipment, as per normal.
A Sub Score of 3-5 points mean that there are 5 test
results that are Problematic. We will call this an
Alarm Rating. This is because we can always expect
WC and kV for an OLTC to deteriorate with time, as
in 1.1 above. The Sub PHI Score of 5, indicates
problems with at least 2 pieces of equipment out of
the 3.
Action would be: Immediately action the
abnormalities, conduct probability of failure analysis
and evaluate the contingency plan.
A Sub Score of >6 points mean that there are
abnormalities encountered with all 3 pieces of
equipment in the Substation. Probability of failure is
raised.
This score would be an Urgent Rating.
Action would be: Action maintenance issues and
consider revised maintenance strategy to maintain
current service levels. Unforeseen opex expenditure is
encountered here. Re-prioritise the completion date of
refurbishment project. A comprehensive Risk Model
is to be conducted. Contingency plan should be ready
to be activated.
Model C (17-point PHI)
We now have a total of 17 individual tests that are
being monitored.
Based on the same principles as in Model B however
each phase of the circuit breaker is represented in the
final substation PHI score.
Advantages:
Simple scoring model to manage.
Disadvantages:
The circuit breaker is overrepresented in the
substation PHI rating. It counts 40% to the
substation PHI, but consists of 12 tests.