22-05-2012, 11:07 AM
Flexible Ship Electric Power System Design
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Introduction
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
110 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 solidstate
protective devices.
Shipboard Power System Structure
Navy Ships use three phase power generated
and distributed in an ungrounded delta
configuration. Ungrounded systems are used to
ensure continued operation of the electrical
system despite the presence of a single phase
ground. The voltages are generated at levels of
450 volts a.c. at 60 hertz. The most popular
topology used in Navy electrical system is a ring
configuration of the generators which provides
more flexibility in terms of generation
connection and system configuration. In this
type of topology, any generator can provide
power to any load. This feature is of great
importance in order to ensure supply of power
to vital loads if failure of an operating
generating unit occurs.
Reconfiguration and Restoration
System faults must be quickly resolved by
removal of the faulted portion of the system
from the remainder of the system. These faults
could be due to material casualties of individual
loads or widespread fault due to battle damage.
In addition to load faults, casualties can occur to
cables, power generating equipment, or power
distribution buses which can lead to conditions
of having inadequate power generation capacity
for all attached loads.
CURRENT STATUS OF MONITORING AND CONTROL
Table 1 characterizes the current status of the
monitoring, control, and protection functions of
protective devices in shipboard electrical
systems. Remote operation in the table refers to
operations at the control center. The table shows
that below the load center, the protective
devices are locally controlled and monitored
which does not permit remote automation of
those devices.