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Power & Distribution > Main Electrical Distribution > Flashcards

Main Electrical Distribution Flashcards

1
Q

what are the requirements for Main Electrical Distribution System:

A

Motors for auxiliaries, refrigeration, air conditioning
Lighting and converted supplies.
Weapon systems, radar and sonar systems, external communications

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2
Q

To generate power we need three basic items:

A

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

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3
Q

The main supply system has normally how many generators

A

minimum of 4 normally

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4
Q

What does EDC stand for?

A

Electrical Distribution Centre

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5
Q

what does MCCB stand for?

A

Moulded case circuit breakers

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6
Q

what links generator to a busbar?

A

supply breaker

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7
Q

Name the Seven major components to the power distribution system:

A 
Generator
Supply breaker, busbar linking breakers, interconnecting   breakers
Switchboard (contains the Bus Bars)
Feeder breaker
Electrical Distribution Centres
Fuse panels
Transformers
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8
Q

What does VD mean in the power book

A

Voltage Drop through the cable

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9
Q

What does SC stand for in the power book

A

Starting current

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10
Q

what documents do we have to support our distribution system?

A

The Power Book
Low Power & Lighting Book
Portable Apparatus Book

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11
Q

The main supply is what in volts, hertz and ohms?

A

450v, 60Hz, 3Ø

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12
Q

the main supply is transferred to how many volts, hertz and ohms?

A

115v 60Hz 3Ø

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13
Q

how many phases are required to supply for lighting and small power circuits

A

only a single phase

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14
Q

Numbers on the fuse panels are often referred to as?

A

post codes

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15
Q

What do the post codes show?

A

Where power is coming from

Where power is going to

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16
Q

440V discrimination uses a ratio of what?

115V discrimination uses a ratio of what?

A

3: 1
2: 1

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17
Q

What is PCP and SCP

A

primary control position

Secondary control position

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18
Q

What is MCR

A

Machinery control room

19
Q

What is SCC

A

Ship’s Control Centre

20
Q

PCP controls what?

A

All main breakers
All generator voltages
All generator frequencies
Anti-condensation heaters in switchboard

21
Q

SCP controls what?

A

Breakers controlled by section switchboard
Voltages of generators controlled by section switchboard
Frequency of generators controlled by section switchboard
Anti-condensation heaters in switchboard

22
Q

Switchboards have Six meters

these are:

A 
Voltmeter
Frequency meter
Watt meter
Ammeter
Syncroscope
Earth Fault Indicator
23
Q

Switchboards have four controls what are they?

A

Start/stop switch Diesel Start
Selector switch Select Generator Voltage or Frequency
Control Switch PCP/SCP Control
Discrepancy switch Open/Close breakers

24
Q

Switchboards have six indicator lights, these are:

A

Control Available/Not available
Generator running
Fire detected
Over temperature
Breaker tripped Discrepancy Switch Illuminates
Earth fault Light Indication & Audible Alarm

25
Q

What are the nine steps required for connecting shore supply?

A 
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
26
Q

the ship has to be what, when earthing from a shore supply?

A 
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
27
Q

After shore power is switched on but before connecting to the ship you have to:

A

Check voltage and frequency
Check stability of supply
Check proper connection of cables

28
Q

Essential equipment provided with two supplies

A

Normal

Alternative

29
Q

What are the three categories of changeover switch?

A

Automatic Change-Over Switch (ACOS)
Remote Operated Change-Over Switch (ROCOS)
Hand Change-Over Switch (HCOS)

30
Q

What are the three types of hand changeover switch

A

Normal/alternative
Normal/emergency
Normal/alternative/emergency

31
Q

when dealing with the Hand Change-Over Switch

A

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

32
Q

if the phases are connected incorrectly

A

Pumps and Motors will run backwards and pumps could be damaged

33
Q

All equipment generating or operating at greater than 35V AC or 50V DC must be ?

A

Earth bonded

34
Q

Portable electrical equipment has two classifications

A

Class 1

Class 2

35
Q

Portable equipment voltage is limited to how many volts

A

115V AC

36
Q

Portable equipment fuse rating is limited to how many amps

A

20 amps

37
Q

what does ACOS stand for

A

Automatic Change over switch

38
Q

What does ROCOS stand for

A

Remote Operated Change-Over Switch

39
Q

How can you operate ROCOS

A

Operated by hand from a remote location

Operating switch located in ship’s control centre

40
Q

how are the Presence of earth faults indicated in two ways

A

Indicator light on PCP and SCP switchboards

Audible alarm

41
Q

what is an EDP

A

electrical distribution panel

42
Q

what portable electrical equipment are exempt from earth testing?

A

Equipment working at 440v AC, phase 3

Locally approved 240v AC, private equipment

43
Q

Mains voltage powered private electrical equipment is to be registered where?

A

In the ship’s Private Electrical Equipment Log

Power & Distribution (2 decks)

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