The electrical system refers to the generation, storage, distribution, and use of electrical power onboard a vessel. The complexity of a vessels electrical system can vary; from small-craft electrical to diesel-electric arrangements and all-electric ships. For typical vessel sizes, a Single-Line Electrical drawing is used to describe shipboard electrical systems.
Larger vessels will have at least two generators (diesel-electric arrangements having at least three); with one generator kept on standby at all times. Notwithstanding DC vessels, most vessels generate 440V/60Hz or 380V/50Hz AC for main ship services. As such, most marine loads (such as pumps or winches) operate at this voltage. Where a vessel is fitted with a higher-voltage load, such as electric motors in the drivetrain, the ships gensets will generate at the highest voltage and use transformers to reduce voltages where necissary. Other common marine voltages are 3.3kV,6kV, 6.6kV and 11kV.
SOLAS compliant vessels will have an additional emergency generator located on or above the strength deck. The emergency generator supplies the emergency switchboard loads in the event of catastrophic electrical power loss. Some vessels also use the emergency generator as a harbour generator, supplying the vessels hotel loads at port.