The reliability of offsite power for a nuclear power plant (NPP) is
assessed using fault tree (FT) analysis. The method combines alternating
current (AC) load flow analysis with FT technique. The probability of loss
of offsite power (LOOP) initiating event is assessed based on the
unreliability of the power delivered to the house load of the NPP. Based on
the quantitative and qualitative analysis of the constructed FT, the
probability of the LOOP initiating event is assessed. The FT results
include the importance measures which enable identification of the most
important elements of the power system from the aspect of nuclear safety.
The impact of changes in the power system to the safety of the NPP is
evaluated. The verification of the method was performed on the IEEE test
system.