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Shipboard Electrical Distribution. …“Shifting the Electric Plant to a Normal Full Power Lineup.”. Topics. Primary Power Electrical Distribution System Components of systems Selective tripping Other AC power generation systems DC Power generation Safety Considerations.

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shipboard electrical distribution

Shipboard Electrical Distribution

…“Shifting the Electric Plant to a Normal Full Power Lineup.”

topics
Topics
  • Primary Power
  • Electrical Distribution System
  • Components of systems
  • Selective tripping
  • Other AC power generation systems
  • DC Power generation
  • Safety Considerations
primary power characteristics
Primary Power Characteristics
  • US Residential
    • 115 VAC Power
    • 1 phase, 60 Hz frequency
    • Grounded system
  • US Navy
    • 450 VAC Power
    • 3 phase, 60 Hz frequency
    • Ungrounded system
primary power characteristics1
Primary Power Characteristics
  • Why AC?
    • More power than DC for same size
  • Why 3 Phase?
    • More power than single phase
    • Can operate with only 2 phases - redundancy
  • Why ungrounded?
    • NOT Safety
    • Reliability: at least two faults are required to cause system failure (grounded systems fail with one fault)
basic components
Basic Components
  • Ship Service Generators
    • Primary source of power is rotating-field generator
    • Powered by prime mover
      • SSTG (steam)
      • GTGS (gas)
      • EDG (diesel)
  • Switchboard
    • Metal enclosure that serves as distribution center (contains buswork, breakers, instruments, etc)
basic components1
Basic Components
  • Bus Transfers
    • Allow transfer of load from one bus to another (normal -> alternate)
      • ABT: senses voltage loss quickly and auto transfers supply to alternate source to ensure continuity of power
      • MBT: manual transfer, used for non-vital loads
  • Disconnects
    • Used for infrequent connections (shore power)
basic components2
Basic Components
  • Circuit Breaker
    • Used as switches to connect buswork
    • Trip open and break circuit if unsafe condition (over current, under voltage, under frequency)
  • Fuse
    • Simplest protective device
    • Fusible strip of wire melts to provide protection
    • Must be replaced once blown
electrical distribution
Electrical Distribution
  • Ship Service Distribution System
    • Provides normal and alternate power
    • Power from generators switchboards sent to loads, power panels, etc.
  • Emergency Power Distribution
    • Normally supplied by DG’s
    • Designed to provide power to vital systems during a casualty
electrical distribution1
Electrical Distribution
  • Casualty Power Distribution system
    • Use of portable cables for temporary routing of power in severe casualty
  • Selective Tripping
    • Principle under which faults are isolated as close to the fault as possible and furthest from power supply
    • Done via fuses, switches, and breakers (most current system is arc-fault)
other ac generation systems
Other AC Generation Systems
  • 115 VAC, single phase, 60 Hz used for smaller loads
    • Used for lighting, outlets, etc.
    • Step-down transformer
  • 400 Hz Power
    • Most of electronics including fire control & sonar use 400 Hz
    • 400 Hz MG used to convert 60Hz to 400 Hz
dc generation systems
DC Generation Systems
  • Battery: chemical potential due to dissimilar metals (Pb vs. PbO2) in presence of electron bridge (electrolyte)
  • SSMG: converts AC <-> DC (large machine with an AC end & DC end)
  • Static Inverters: solid state to replace SSMG’s
  • Rectifier: converts AC -> DC
safety considerations
Safety Considerations
  • #1 On-the-job KILLER of sailors
  • Working in vicinity of energized gear requires CO’s permission
  • NUMEROUS electrical safety precautions
    • Electrical Tagout to de-energize where possible
    • Rubber gloves
    • Insulated tools
    • Diamond deck
    • CPR qualified personnel
    • Removal of jewelry/metal objects
    • Etc.
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