After hidden failure outages for all substations are obtained
and consolidated, the security-constrained adequacy
evaluation methodology is applied to evaluate contingencies
resulting from independent, common mode, and hidden failure
outages. If any of such contingencies result in the system loss
of load, which is defined as system failure, such contingencies
have nonzero contribution to system unreliability. The
evaluation results show that there are a total of seven
contingencies resulting from the independent outage, one
contingency resulting from the common mode outage, and
seventy-nine contingencies resulting from the hidden failure
ouaethat lead to system unreliability. These contingencies. . outage
are provided in Table 6, in which only p art of contingencies
resulting from the hidden failure outage are listed. It can be
seen that most of contingencies that result in system failures
are hidden failure contingencies because of the outages of
intact system components following the initial system faults
making the stressed system situation worse.
The reliability indices of probability, frequency, and
duration of such system loss-of-load event are calculated for
both situations with and without the consideration of
contingencies resulting from hidden failure outages.
Results
are shown in Table 7. It can be seen that hidden failures in
protection systems can downgrade the system reliability level
and such influence increases with the increase of the CBTM
failure probability.