Security for space power systems

An initial system security monitor (SSM) developed for the power system of a proposed NASA permanently manned space station is presented. Four types of ranked disturbances or faults to the transmission system are successively corrected by remedial action of the SSM. After each corrective action, the SSM verifies the system change that has been implemented, then proceeds to examine lower-priority disturbances if they persist. The SSM authority is limited by the operating state of the system, and only one correction is permitted for each scan cycle. The disturbance signals are verified by the use of a state estimator. The small network size permits use of connectivity searches of the network topology for possible corrective actions and a load flow to predict the effect of corrective actions. The data scan rate is higher than for earth-based systems. Line switching actions are implemented within line cycles because thyristors are used as circuit breakers. The work presents examples of disturbance identification and remedial action that could also apply to earth-based power systems