Main Electrical Distribution Flashcards
what are the requirements for Main Electrical Distribution System:
Motors for auxiliaries, refrigeration, air conditioning
Lighting and converted supplies.
Weapon systems, radar and sonar systems, external communications
To generate power we need three basic items:
Prime mover that can be either: Gas turbine, steam turbine or diesel engine
AC Generator also known as an ALTERNATOR
A SWITCHBOARD to control and distribute power around the ship
The main supply system has normally how many generators
minimum of 4 normally
What does EDC stand for?
Electrical Distribution Centre
what does MCCB stand for?
Moulded case circuit breakers
what links generator to a busbar?
supply breaker
Name the Seven major components to the power distribution system:
Generator Supply breaker, busbar linking breakers, interconnecting breakers Switchboard (contains the Bus Bars) Feeder breaker Electrical Distribution Centres Fuse panels Transformers
What does VD mean in the power book
Voltage Drop through the cable
What does SC stand for in the power book
Starting current
what documents do we have to support our distribution system?
The Power Book
Low Power & Lighting Book
Portable Apparatus Book
The main supply is what in volts, hertz and ohms?
450v, 60Hz, 3Ø
the main supply is transferred to how many volts, hertz and ohms?
115v 60Hz 3Ø
how many phases are required to supply for lighting and small power circuits
only a single phase
Numbers on the fuse panels are often referred to as?
post codes
What do the post codes show?
Where power is coming from
Where power is going to
440V discrimination uses a ratio of what?
115V discrimination uses a ratio of what?
3: 1
2: 1
What is PCP and SCP
primary control position
Secondary control position
What is MCR
Machinery control room
What is SCC
Ship’s Control Centre
PCP controls what?
All main breakers
All generator voltages
All generator frequencies
Anti-condensation heaters in switchboard
SCP controls what?
Breakers controlled by section switchboard
Voltages of generators controlled by section switchboard
Frequency of generators controlled by section switchboard
Anti-condensation heaters in switchboard
Switchboards have Six meters
these are:
Voltmeter Frequency meter Watt meter Ammeter Syncroscope Earth Fault Indicator
Switchboards have four controls what are they?
Start/stop switch Diesel Start
Selector switch Select Generator Voltage or Frequency
Control Switch PCP/SCP Control
Discrepancy switch Open/Close breakers
Switchboards have six indicator lights, these are:
Control Available/Not available
Generator running
Fire detected
Over temperature
Breaker tripped Discrepancy Switch Illuminates
Earth fault Light Indication & Audible Alarm
What are the nine steps required for connecting shore supply?
Send signal to port Raise permit to work Rack out breakers Prove box ‘Dead’ Obtain Castel key Test shore supply cables Bring on and secure cables Connect cables Inform dockyard
the ship has to be what, when earthing from a shore supply?
The ship must be earthed: To the jetty To the ship along side At two points NOT LESS THAN half the ship’s length apart Gangways are also to be earthed
After shore power is switched on but before connecting to the ship you have to:
Check voltage and frequency
Check stability of supply
Check proper connection of cables
Essential equipment provided with two supplies
Normal
Alternative
What are the three categories of changeover switch?
Automatic Change-Over Switch (ACOS)
Remote Operated Change-Over Switch (ROCOS)
Hand Change-Over Switch (HCOS)
What are the three types of hand changeover switch
Normal/alternative
Normal/emergency
Normal/alternative/emergency
when dealing with the Hand Change-Over Switch
Supply source position must be selected by hand
Emergency position used with damage control cables
Always kept in normal position
Position never changed while equipment running
if the phases are connected incorrectly
Pumps and Motors will run backwards and pumps could be damaged
All equipment generating or operating at greater than 35V AC or 50V DC must be ?
Earth bonded
Portable electrical equipment has two classifications
Class 1
Class 2
Portable equipment voltage is limited to how many volts
115V AC
Portable equipment fuse rating is limited to how many amps
20 amps
what does ACOS stand for
Automatic Change over switch
What does ROCOS stand for
Remote Operated Change-Over Switch
How can you operate ROCOS
Operated by hand from a remote location
Operating switch located in ship’s control centre
how are the Presence of earth faults indicated in two ways
Indicator light on PCP and SCP switchboards
Audible alarm
what is an EDP
electrical distribution panel
what portable electrical equipment are exempt from earth testing?
Equipment working at 440v AC, phase 3
Locally approved 240v AC, private equipment
Mains voltage powered private electrical equipment is to be registered where?
In the ship’s Private Electrical Equipment Log
