Abstract The SBO is defined as the events of Loss of Offsite Power (LOOP) combined by loss of dedicated Emergency Diesel Generators(EDGs) for each unit. The SBO can be also extended when the shared Diesel Generator (AAC-DG) is lost additionally. The Electrical Cross-tie (ECT) is the concept of sharing other unit’s dedicated EDG to the unit under extended SBO in the multi-unit NPP site. We re-evaluate the risk of the extended SBO with the ECT option in Single Unit PRA considering Multi-Unit Features. To get a more realistic estimation of Core Damage Frequency (CDF), we developed the KU-PRA model using the AIMS-PSA code. We examined the factor of redundancy of the AC sources on the CDF by adding additional EDGs to the reference KU-PRA Model. We developed methodology and modeling of the Electrical Cross-tie for Multi-units PRA considering Common Cause Failure, Human Reliability Analyses, Battery load shedding, and Occupancy factor.