Faults would be isolated, and systems would route power past damaged parts.

New solid-state-based protection devices — current limiters and circuit breakers — could be employed to limit and interrupt fault currents. It has been shown that these devices should be of a hybrid type [e.g., incorporating high-speed mechanical circuit breakers in addition to solid-state electronic components] in order to satisfy the protection and operation requirements peculiar to DC SESs.

Protection Scheme

In simplified terms, what is needed is to isolate a damaged or otherwise faulty part of a power-distribution system or a power-consuming system connected to it. It was shown that the agent-based scheme could provide effective protection of a DC SES, in that the protection agents associated with the protection devices could autonomously detect and isolate any disturbance that could occur in the system, and the response times of the agents would be very short — less than 1 ms for disturbances on the DC primary bus, which is the most vulnerable section of a DC SES.

Configuration Management

The focus in this part of the program was on the development of configuration- management schemes in which the power-distribution circuitry of a DC SES would be reconfigured automatically so as to minimize the adverse effects of a fault or a disturbance upon the loads. The major accomplishment of this part of the program was the development of a scheme in which the protection agents would collaborate in performing reconfiguration in stages as needed:

  1. Automatic Load Transfer and Bus Reconfiguration

    The protection agents would be utilized to localize the fault rapidly and then assure continuity of power to critical loads, even in the presence of battle damage. First, the critical loads would be transferred to an alternate bus (see figure) without any disruption of power. Next, sectionalizing switches on the main DC bus would be operated to reconfigure that bus to limit the duration of interruption of power to the non-critical loads to an interval of about 10 to 20 ms.

  2. Load Management

    For extreme contingencies in which the demand for power exceeds the supply, a central agent at the power generator would curtail the loads when the generator becomes overloaded. The use of distributed generation as a means of enhancing load management was also investigated.

This work was done by Mesut Baran of North Carolina State University for the Office of Naval Research.

This Brief includes a Technical Support Package (TSP).

Protection Schemes for Advanced Shipboard Electrical Systems (reference ONR-0005) is currently available for download from the TSP library.

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