Supply & Distribution

Question 1

What three basic things are needed to generate power?

Answer 1

Prime mover
AC Generator
Switchboard

Question 2

What does EDC stand for?

Answer 2

Electrical distribution center.

Question 3

Explain a generic main supply system.

Answer 3

Usually minimum of 4 generators with a supply breaker in its own switchboard section with its own bus-bars, linked by a busbar linking breaker. 
Two switchboards (fwd/aft or port-stbd) are linked by interconnecting breakers.
Each switchboard has its own set of bus bars. 
Bus bars supply power to the EDC via feeder breakers. 
EDC's are situated around the ship and contain switches known as MCCB's. 
MCCB's feed power to the ships services.

Question 4

What does MCCB stand for?

Answer 4

Moulded case circuit breakers.

Question 5

What 5 main breakers are fitted to a ship main distribution system and their uses?

Answer 5

Supply breaker - connects generator to bus bars
Shore supply breaker - allows isolation between ship from another ship or shore supply
Bus bar linking breaker - allows isolation of busbars from each other
Inter-connector breaker - allows isolation between switchboards
Feeder breaker - connects aparatus and switchboard

Question 6

What are the 7 main components of the power distribution system?

Answer 6

Generator
Supply, busbar linking and interconnecting breakers
Switchboard
Feeder breaker
EDC
Fuse panels

Question 7

What does the power book show?

Answer 7

Distribution of all 450 V services
Drawings of generator and switchboard circuit layout
Drawings of the distribution circuits

Question 8

What does the low power & lighting book contain?

Answer 8

Distribution of all 115 V services

Specifically concerned with lighting system

Question 9

What does the portable apparatus drawing book contain?

Answer 9

Distribution of all 115/230 V services

Specifically concerned with power supplies to 115/230 V sockets

Question 10

What main reference books are there?

Answer 10

The power book
Low power and lighting book
Portable apparatus book

Question 11

Where are the books normally kept?

Answer 11

A central place ie main switchboard or electrical workshop

Question 12

What is the main supply?

Answer 12

450 v, 60 hz, 3 phase

Question 13

Where is the main supply fed to?

Answer 13

The EDC

Question 14

Where is the main supply distributed to?

Answer 14

The ships services

Question 15

What is the main supply transformed to?

Answer 15

115 v, 60 hz, 3 phase

Question 16

What do breakers and fuses protect?

Answer 16

The power supply.

Question 17

What is the first breaker to trip?

Answer 17

The MCCB

Question 18

What is the last breaker to trip?

Answer 18

The supply breaker

Question 19

Which fuse will blow first?

Answer 19

The one nearest to the fault.

Question 20

What ratio does 440 V discrimination use?

Answer 20

3:1

Question 21

What ratio does 115 V discrimination use?

Answer 21

2:1

Question 22

Where is power and distribution controlled from?

Answer 22

Primary control position PCP

Secondary control position SCP

Question 23

There is the PCP?

Answer 23

In the ship’s control center (SCC)

Question 24

What does PCP show?

Answer 24

Plan of whole electrical distribution system up to the EDC

State of all breakers and generators

Question 25

What does the PCP control?

Answer 25

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

Question 26

Where is the SCP?

Answer 26

In the machinery sections.

Question 27

What does the SCP show?

Answer 27

Plan of electrical distribution system fed from the section | State of all breakers and generators controlled by the section

Question 28

What does the SCP control?

Answer 28

All breakers controlled by section switchboard All generator voltages controlled by section switchboard All generator frequencies controlled by section switchboard Anti-condensation heaters in switchboard

Question 29

What meters are attached to switchboards?

Answer 29

``` Voltmeter Frequency meter Watt meter Ammeter Syncroscope Earth fault indicator ```

Question 30

What does a discrepancy switch do?

Answer 30

Shows if there is a discrepancy between the breaker and the switchboard and allows the breakers to be controlled. If the light is on, there is a discrepancy.

Question 31

What four controls do switchboards have?

Answer 31

Start/stop switch Selector switch Control switch Discrepancy switch

Question 32

What six indicator lights do switchboards have?

Answer 32

``` Control available/ not available Generator running Fire detected Over temperature Breaker tripped Earth fault ```

Question 33

What are the 9 steps required for connecting to shore supply?

Answer 33

``` 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 ```

Question 34

Where must the ship be earthed when connected to shore supply?

Answer 34

To the jetty The the ship alongside At two points not less than half the ships length apart Gangways are earthed

Question 35

What checks are done after shore power is switched on but before connecting to ship?

Answer 35

Voltage and frequency Stability of supply Proper connection of cables

Question 36

If power cables are connected correctly, what will the phase sequence indicator show?

Answer 36

The light on the right will be bright, the light on the left will be dim.

Question 37

What will happen if phases are incorrectly connected?

Answer 37

Motors and pumps will run backwards and damage equipment.

Question 38

What must be done before shore supply cables can be connected to shore supply box?

Answer 38

The cables must be checked for dead.

Question 39

What are three categories of change over switches?

Answer 39

Automatic ACOS Remote operated ROCOS Hand HCOS

Question 40

Which two supplies are all essential equipment provided with?

Answer 40

Normal | Alternative

Question 41

Where is a remote operated change over switch located?

Answer 41

Ships control center SCC

Question 42

What are the three types of hand change over switches?

Answer 42

Normal/alternative Normal/emergency Normal/alternative/emergency

Question 43

What position is a HCOS kept in and when will a HCOS position never be changed?

Answer 43

Kept in normal position | Never changed while equipment is running

Question 44

If the normal supply fails, what will an ACOS do?

Answer 44

Automatically switch to the alternative supply

Question 45

Which two ways are earth faults indicated?

Answer 45

Indicator light on PCP and SCP switchboards | Audible alarm

Question 46

How are earth faults tested in a 450 V ac system?

Answer 46

Automatically

Question 47

How and where are earth faults tested on a 115 V ac system?

Answer 47

Done at the first fuse panel after the transformer. | Usually by using insulation resistance test using MIT 420.

Question 48

Why is the 115 V system not tested for earth faults the same way as the 450 V system?

Answer 48

Because there is an air gap between the primary and secondary coils of the transformer, so there is no physical connection between the two.

Question 49

How do you test for earth faults on a control and communications switchboard?

Answer 49

Push the two buttons simultaneously to test the lights, push each button individually to test the positive and negative side of the DC supply.

Question 50

What voltage emergency supply does the C&C switchboard supply?

Answer 50

24 v DC

Question 51

How is an earth fault indicated on a electrical distribution panel EDP?

Answer 51

An earth fault indication light will illuminate if there is an earth fault in any circuit powered by the EDC.

Question 52

What equipment must be earth bonded?

Answer 52

All equipment generating or operating at greater than 35 v AC or 50 v DC must be earth bonded.

Question 53

What are the two classifications of portable electrical equipment?

Answer 53

Class 1 | Class 2

Question 54

What voltage and fuse rating limited to for portable equipment?

Answer 54

115 v AC | 20 Amps

Question 55

What does a postcode identify?

Answer 55

Where power is coming from | Where power is going to

Question 56

How many EDCs are there in a generic distribution system?

Answer 56

4

Question 57

What is the reference book and what is it used for?

Answer 57

Documents and is used in conjunction with the power book and lists all fittings, the number fitted, component symbols and pattern numbers.

Question 58

What is the name for the collection of reference books?

Answer 58

Engineers as fitted books.