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| Three generators in a ring Configuration |
The first electrical power system was installed on the USS
Trenton in 1883 (Ykema 1988). The system consisted of a single dynamo supplying
current to 247 lamps at a voltage of 10 volts d.c. Until the 1914 to 1917 period,
the early electrical power systems were principally d.c. with the loads
consisting mainly of motors and lighting. It was during World War I that 230
volt, 60 hertz power systems were seriously introduced into naval vessels.
Since World War II the ship’s electrical systems have continued to improve,
including the use of 4,160 volt power systems and the introduction of
electronic solid-state protective devices. Protective devices were developed to
monitor the essential parameters of electrical power systems and then through
built-in logic, determine the degree of configuration of the system necessary
to limit the damage to continuity of electric service for the vessel (Ykema 1988).
Fuses are the oldest form of protective devices used in
electrical power systems in commercial systems and on navy vessels. Circuit
breakers were added around the turn of the century. The first electronic
solid-state over current protective device used by the Navy was installed on
the 4,160 power system in Nimitz class carriers. Navy systems of today supply
electrical energy to sophisticated weapons systems, communications systems,
navigational systems, and operational systems. To maintain the availability of
energy to the connected loads to keep all systems and equipment operational,
the navy electrical systems utilize fuses, circuit breakers, and protective
relays to interrupt the smallest portion of the system under any abnormal
condition.
The existing
protection system has several shortcomings in providing continuous supply under
battle and certain major failure conditions. The control strategies which are
implemented when these types of damage occur are not effective in isolating
only the loads affected by the damage, and are highly dependent on human
intervention to manually reconfigure the distribution system to restore supply
to healthy loads.
This paper discusses new techniques which aim to overcome
the shortcomings of the protective system. These techniques are composed of
advanced monitoring and control, automated failure location, automated
intelligent system reconfiguration and restoration, and self-optimizing under
partial failure.
These new techniques will eliminate human mistakes, make
intelligent reconfiguration decisions more quickly, and reduce the manpower
required to perform the functions. It will also provide optimal electric power
service through the surviving system. With fewer personnel being available on
ships in the future, the presence of this automated system on a ship may mean
the difference between disaster and survival.
Two new architectures for designing ship power systems have
been introduced: the current source current intensive (CSCI) and the articulate
system. The basic characteristics of these systems have been discussed. It
appears that the CSCI is the more ambitious of the two architectures. By this
virtue it will also be realizable in a more distant future. However, some
aspects of the articulate system architecture, as discussed in this paper can
be implemented in the short term. A flexible AC distribution systems, within
the context of flexible AC transmission systems (FACTS) (Hingorani 1993) which
are now undergoing rapid development and implementation, can be regarded as a
subset of the family of control methodologies which constitute the realm of
articulate systems. Undoubtedly as the CSCI and articulate system designs
progress, problems will arise; however, the developments in superconductors,
superconducting magnetic energy storage, and power electronics will provide a
wide technical base to solve these problems. These advanced system
architectures suggest better ways for implementing the power distribution
system in next generation ships. They also provide ways to bring new
technologies, better system operation, to existing ships during its
retrofitting for service life extension.
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