102 electrical, lightning, lift & escalators

8/10/2019 102 Electrical, Lightning, Lift & Escalators

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Electrical, Lightning, Lift and Escalator Services Set 1

Q1 Draw a fully labeled diagram showing how TN-S earthing system is implemented forconsumer receiving single-phase and three-phase power supply. ( 5 marks)

Q2a Figure shows the single-line diagram of a LT switch board. Name the componentsnumbered 1 to 5 shown in the diagram. Describe briefly the function of the components

numbered 1 to 5. (10 marks)

The components numbered 1 to 5 are

1) Outgoing indicating lights

2) Ammeter3) Earth fault relay

4) Current Transformer

5) Voltage selector switch

Function of the components are

1) These lights are to indicate that the supply to the

switchboard is on.

2) The function of the ammeter with selectors switch

is to measure the current flowing through the 3 lines

3) The function of the earth fault relay is to detect

any earth fault in the system and to activate theshunt trip of the main circuit breaker (MCCB).

4) The function of the current transformer is to step

down the high current in the primary circuit to either

5A or 1A for the relay.

5) The function of the voltage selector switch is to

select either the line of phase voltage for

measurement.


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Q2b Describe with annotated diagrams the remedial works the need to be carried out around

the conduits when the conduit pass through floor and wall openings. ( 5 marks)

Q3a Figure shows a section of a lift installation. Name any five of the components marked 1 to 8.

( 5 marks)

The named components are

1) Drive machine or motor

2) Controller

3) Roller guide shoe or guide shoe

4) Guide rail for lift car

5) Lift car

6) Travelling cable

7) Guide rail for counter weight

8) Counter weight

( Any 5, 1 mark each)


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Q3b List down any three componentsof a lightning protection system and briefly describe the

location where these components are typically installed. ( 6 Marks)

Three components of the lightning protection system and the location where they are typically

installed are,

Air termination network --> Located at the roof of the building

Down conductors --> Provided along the side of the building from the air termination network

on the roof to earth termination in the ground.

Earth termination network --> Located at the ground level near to the building

Test clamp --> Located at about 1.5m above the ground level where down conductor and earth

conductor are clamp together. ( Any 3, 2 marks each)

Electrical, Lightning, Lift and Escalator Services Set 2

Q1 Figure show 4-core PVC SWA PVC belted copper cable. Write the proper names of all the

components of the cable numbered 1 to 5. ( 5 marks) ( 1 mark each)

Q2a Sketch an annotated diagram to show how an earth-plate could be used as part of the

earthing system for an electrical installation. ( 7 marks)

4

3

2

15


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Q2b When the electrical contractor is carrying out the trunking work at site, list 5items of workthat you need to check to ensure the trunking work is done properly. ( 8 marks)

(Any 4, 2marks each)

The items to be checked to ensure that the trunking work is done properly are as follows,

Fire barriers must be installed inside the trunking when it s passes through floor, wall and partitions if the

size of the trunking is greater than 710 sqmm.

Floors, walls and partitions opening must be filled with incombustible materials when the trunking passthrough it.

Trunking may be secured direct to a surface or suspended by mean of brackets and no sharp edged

screw to be used.

Entry to trunking must be so placed as to prevent water from entering.

Sizing of trunking must ensure that when cable are drawn into it, the cables will not be damaged. There

must also be enough space in the trunking for the cable to ensure that the temperature will not rise

significantly.

Trunking should not be used as a circuit protective conductor. However, copper straps should be fitted

across joints to ensure electrical earthing continuity.

In multi-compartment trunking, segregation of circuits as required by CP5:1998 must be compiled.

All phase and neutral(if any) of A.C circuits must be contained in the same metal trunking.

Q3a Explain why it is necessary to bond the metallic structure and metallic parts of a buildingin the vicinity to the lightning protective system. Also name four such components that are

normally bonded to the lightning protective system. ( 6 marks)

The reason for the bonding to the metallic parts to the lightning protective system is as below,

During Lightning, the potential of the lightning protective system will be raised to very high

voltage of several kilovolts.

If the metallic parts are not connected to lightning protective system, they will remain at

potential.As a result, there will be large potential different between the lightning protective system

and metallic parts which may lead to side flashing and cause damage. (4 marks)

Four for the metal parts that are normally bonded to the lightning protective system are,

Antenna system

Railing and hand rails

Metallic door and window frames

Reinforcement bar of the structure

Metallic gutters and vent pipes

Electrical earthing system (Any 4, 1/2 mark each)

Q3bDuring construction at M&E coordinator, you have to ensure that the lift contractor'sstructural requirements as shown in their sub-contract drawings are properly incorporated.

What are the items of work that you will check in this regards for the lift shaft & lift pit to

ensure compliance? (5 marks)

The following items of work will be checked in the lift shaft and lift pit to ensure that the lift

sub-contractor requirements are met,

The pit is provided with water proofing, necessary drainage facilities, ventilation and access

ladder.


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Q2b Figure show the earth termination of a lightning protection system. Draw a sketch on your

answer book. Label any three components and mark the missing dimensions. ( 5 marks)

Q2cSome of the important of an escalator are numbered 1 to 8 in the figure shown below.

Name any five of those components. ( 5 marks)

The components of the escalator are asbelow,

1) Electric motor

2) Drive gear

3) Handrail drive

4) Handrail

5) Step

6) Return wheel

7) Chain guide

8) Inner rail

(Any 5, 1 mark each)

1

2

3

4

5

?

?

102 electrical, lightning, lift & escalators

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