ENGINEERING LESSON GUIDE 16

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ENGINEERINGLESSONGUIDE 16

• Shipboard Electrical Distribution

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INTRODUCTION TO NAVAL ENGINEERING
SHIPBOARD ELECTRICAL DISTRIBUTION
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ELECTRICAL DISTRIBUTION COMPONENTS

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BUS TIE
N
A
ABT
SSTG 3
SSTG 1
FIRE CONTROL
A
N
SSTG 4
SSTG 2
MBT
2S
1S
ABT
N
STEERING PANEL
E
N
N
EMERGENCY GENERATOR SWITCHBOARD 2
EMERGENCY GENERATOR SWITCHBOARD 1
E
E
ABT
ABT
TO VITAL LOADS
TO VITAL LOADS
CASUALTY POWER CONNECTION
EDG 1
EDG 2
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Shipboard Generators

• Prime mover depends on ships propulsion plant
• Ships Service Turbine Generator (SSTG)
• Gas Turbine Generator Set (GTGS)
• Ships Service Diesel Generator (SSDG)
• All generators are rotating-field, 450 V, 60 Hz,
  three-phase AC generators
• A speed governor is used to control prime mover
  constant speed (controls rotor speed, and
  therefore controls output frequency ? maintain at
  60 Hz)
• A voltage regulator is used to control the field
  current (controls rotor magnetic field strength,
  and therefore controls output voltage ? maintain
  at 450 V)

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Vital v. Non-vital

• Vital loads have multiple power sources and are
  usually connected via an ABT
• Fire fighting pumps
• Steering
• Weapons systems
• Coffee maker
• Non-vital loads are not required for safe
  operation of the ship
• Power receptacles in berthing
• Laundry/Galley equipment

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Basic shipboard electrical distribution system

• Bus (Vital/Non-Vital)
• A large conductor capable of carrying electrical
  power from generator to circuit distribution
  switchboards
• Switchboards
• Houses all instruments and devices to control and
  distribute electricity
• Main switchboards
• Emergency switchboards

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SELECTIVE TRIPPING

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Fuse

• An electrical protective device consisting of a
  fusible (easily melted) metal-alloy strip of wire
  encased in a cartridge
• If current exceeds a predetermined value,
  sufficient heat is generated to melt the fuse
  causing an open circuit
• Protects the circuit from possible damage due to
  excessive current

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Circuit Breaker

• An electrical device that opens when the current
  exceeds a predetermined value for the circuit
• Circuit breakers trip open, and may be reset when
  the operators are ready to close the circuit
  breaker
• Circuit breakers may be operated manually or
  electrically, and can be used as switches in some
  circuits

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ARC FAULT

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Automatic Bus Transfer

• Also known as ABT
• A device that senses a loss of power from a
  normal (N) source and will automatically
  disconnect the load from the normal source and
  connect it to an alternate (A) source
• ABTs can be designed to transfer loads very
  quickly (within 50 ms)

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Emergency Power Distribution System

• Emergency (E) power is normally supplied by two
  or more emergency diesel generators (EDGs) which
  will start automatically upon a loss power to the
  SSDS
• Located in forward and after ends of the ship and
  low in the ship
• Physical separation between SSDS and the
  emergency power distribution system minimizes the
  possibility battle damage will cause a total loss
  of electrical power

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DEGAUSSING

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Earths Magnetic Field

• The earth acts as a 6,000 mi long permanent
  magnet, affecting all ferrous materials close to
  its surface
• A ships magnetic field interaction with the
  earths will distort the background field into
  areas of increased or decreased magnetic strength
• This distortion is used by some firing mechanisms
  in mines or torpedoes

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Shipboard Degaussing Coils

• Energized electric cable coils are located in
  specific locations onboard ship to neutralize
  distortion of the earths magnetic field
• Periodic checks at magnetic range stations are
  used to determine the value of current needed in
  the ships degaussing coils
• Also includes compensating equipment so that
  ships magnetic navigation equipment is not
  affected

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Reading

• Read
• Principles of Naval Engineering
• Chapter 22
• Chapter 23

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Questions??