Three alternatives were considered during the
development of the substation plant health index.
Model A (Summated PHI)
In Model A, a simple approach was taken by
summating the different values of the equipment
routine test results. However, where multiples of
equipment exist i.e. >1 transformer or multiple feeder
circuit breakers, the substation PHI just runs away.
This provides difficulty in having a credible range
per in-specification (good), alarm and unacceptable
(urgent) rating.
Advantages:
Simple mathematical approach where tests results
values are easily summated.
Disadvantages:
A good rating for TDCG PHI Score tends to 0.
Thus it counters the summation of the other tests.
The substation PHI is not reflective of the “bad”
TDCG score.
There is no representation of individual
equipment PHI.
The end score is a challenging number to
manage.