Chapter  9—ENGINEERING  CASUALTY  CONTROL lighting,   interior   communication,   electronics equipment, and other electrically powered devices. In designing the electric plant, every effort is made to obtain the greatest reliability and continuity of service possible under casualty conditions. from any live switchboard to supply power to vital circuits. EMERGENCY  POWER  SYSTEM The distribution system forms the vital con- nection between the generators and the equipment which uses electric power. The distribution of elec- trical  power  is  generally  done  through  either  the ship’s  service  or  the  emergency  switchboards. Electrical power distribution may also be done through  a  casualty  power  circuit  rigged  from either of these switchboards. The general arrangement of the ship’s service system is such that any faulty circuit will be cut out  automatically,  without  interruption  of  power supply to other circuits. This is done through the operation of protective devices. If the ship’s serv- ice generators fail, the emergency generator is automatically placed in operation for battle func- tions.  The  emergency  switchboard  can  supply power to all parts of the ship; however, all un- necessary circuits must be stripped from the board when   the   emergency   generator   is   set   up   in automatic to supply emergency power to vital equipment. If this is not done, the generator will be overloaded and the breakers will trip out or the  diesel  engine  will  stall. The  purpose  of  the  emergency  power  system is to furnish an immediate, automatic source of electric power to a limited number of selected vital circuits.  It  includes  one  or  more  diesel-driven emergency  generators,  the  emergency  switch- boards,   and   a   distribution   system,   which   is separate from the ship’s service electric plant and distribution system. Emergency feeders run from the emergency switchboards to at least one and usually  to  two  different  ship’s  service  switch- boards. Emergency power feeders for certain vital auxiliaries  are  also  run  to  control  panels.  The emergency   power   system,   with   the   use   of transformers, is also used for furnishing emer- gency  lighting. Whenever  practical,  emergency  generators  and switchboards are installed above the waterline, to minimize   danger   from   flooding.   Also,   the emergency plant is installed as far away as prac- tical from the ship’s service plant, to avoid both plants being put out of action by battle damage. Protection against loss of power on a ship with ship’s service, emergency, and casualty power distribution systems is described below: On most ships, the emergency generators do not have the same capacity as the ship’s service plants. Therefore, care must be taken to prevent overloading the emergency generator, which in turn will overload the diesel engine. CASUALTY POWER SYSTEM 1.  FAILURE  OF  ONE  SHIP’S  SERVICE GENERATING   PLANT.   The   load   is   trans- ferred,  by  the  Electrician’s  Mate,  to  the  other ship’s service generating plant. Care must be taken to prevent overloading the generating plant that takes over the load. The  casualty  power  system  is  used  to  supply emergency power for steering gear, fireroom and engineroom  auxiliaries,  fire  pumps,  drainage pumps,  communications  equipment,  and  other vital machinery needed to keep the ship afloat or to get it out of a danger area. 2.   CIRCUIT   OR   SWITCHBOARD FAILURE. Vital loads are transferred to an alter- nate feeder and source of ship’s service power by means of a transfer switch on the control panel. 3.  FAILURE  OF  BOTH  NORMAL  AND ALTERNATE POWER SUPPLY. Certain vital equipment  are  shifted  to  an  emergency  feeder which   receives   power   from   the   emergency switchboard. 4.  FAILURE  OF  THE  SHIP’S  SERVICE AND   EMERGENCY   CIRCUITS.   Temporary circuits are rigged with the casualty power cables The casualty power system is a simple electrical distribution system used to maintain a source of electrical supply for the most vital machinery and equipment  needed  to  keep  the  ship  afloat  and functioning. This casualty power system is in- tended   to   supply   power   during   emergencies ONLY. The system is purposely kept simple so that it can be rigged quickly and with a minimum chance of error; but, the very simplicity of its design limits the extent of its use. Sources of supply for casualty power use are provided  at  each  ship’s  service  switchboard  and 9-11