In this paper the latest Electric Power System (EPS) off-nominal operations and caution and waming techniques for the Intemational Space Station (ISS) are presented. The EPS off-nominal operations development consists of a compilation of analyses that provide plans and procedures for continued operation of the EPS in the event of a failure or anomaly. The off-nominal conditions encompass the following: ( I ) expected system performance changes (Le., contributions due to aging), ( 2 ) failures that are automatically detected, isolated,and reconfigured, (3) failures that are manually reconfigured (extravehicular activity [EVA] or via command and control by an operator), and (4) unexpected system anomalies. Off-nominal scenarios including those associated with failure detection, isolation, and recovery (FDIR) operations within the ISS EPS are performed by FDIR functionality allocated to individual FDIR domains resident in equipment that implements the EP functionality (Aghabarari 1995).The off-nominal conditions were isolated by estimating EPS effect and risk assessment for loss of function andlor hazard relation. After off-nominal scenarios are identified, the following products are developed to support EPS testing and verification:(1) detailed procedures, ( 2 ) test plans, and (3) test requirements. The identification and development of off-nominal scenarios was performed on a flight-by-flight basis.Additional objectives of off-nominal and contingency analysis reviewed in this paper include (1) initial verification that the EPS design supports continued operation after a single failure for every station build, (2) to provide a solid basis for the development of test plans, requirements, and procedures to be used at testing facilities, (3) feedback on requirements compliance and the adequacy of the design to support off-nominal and contingency operations, (4) operational constraints that exist after a failure occurs, (5) the effects of given failures based on the accomplishment of mission objectives, and (6) the relative risk of continued operation with the failed condition, and recommended plans for future flights based on the relative risk.

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