ee022-electrical installation 2-th-inst.pdf

7/25/2019 EE022-Electrical Installation 2-Th-Inst.pdf

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SRI LANKA INSTITUTE of ADVANCED TECHNOLOGICAL EDUCATION

Training Unit

Electrical Installation 2Theory

No: EE 022

INDUSTRIETECHNIKINDUSTRIETECHNIK

ELECTRICAL and ELECTRONIC

ENGINEERING

Instructor Manual


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Training Unit

Electrical Installation 2

Theoretical Part

No.: EE 022

Edition: 2008Al l Rights Reserved

Editor: MCE Industrietechnik Linz GmbH & CoEducation and Training Systems, DM-1Lunzerst rasse 64 P.O.Box 36, A 4031 Linz / Aus triaTel. (+ 43 / 732) 6987 3475Fax (+ 43 / 732) 6980 4271Website: www.mcelinz.com


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ELECTRICAL INSTALLATION 2

CONTENTS Page

LEARNING OBJECTIVES...................................................................................................5

1 DOMESTIC CONNECTIONS .......................................................................................6

1.1 General ................................................................................................................6

1.2

Types of domestic connection ............................................................................. 6

1.2.1

Overhead-cable connections ...........................................................................7

1.2.2 Wall-box connection (facade connection) ......................................................10

1.2.3 Underground-cable connection ......................................................................11

1.2.4

Special connections .......................................................................................11

1.3

Guidelines for making connections ....................................................................12

1.3.1 Safety.............................................................................................................12

1.3.2

Inside connection ...........................................................................................12

1.3.3 Pre-meter cables............................................................................................12

1.3.4

Voltage drop...................................................................................................12

2

METER PANELS........................................................................................................13

2.1 General ..............................................................................................................13

2.2 Fixing areas ....................................................................................................... 13

2.3

Type of fixing......................................................................................................14

2.3.1 Meter panels ..................................................................................................14

2.3.2

Distribution Units............................................................................................14

3

SWITCHING AND DISTRIBUTION PANELS.............................................................16

3.1 General ..............................................................................................................16

3.1.1 Distribution fuses............................................................................................16

3.1.2 Distribution panels..........................................................................................16

3.2

Voltage drop in distribution cables .....................................................................17

4 INSTALLATION IN SPECIAL AREAS........................................................................18

4.1

Special rooms and workplaces ..........................................................................18

4.2 Rooms which are occasionally damp (bathrooms) ............................................18

4.2.1 Area of protection ...........................................................................................18


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4.2.2 Protective earthing .........................................................................................19

4.2.3

Installation of electrical appliances.................................................................19

4.2.4 Permitted types of cable installation...............................................................19

4.3 Damp and wet rooms.........................................................................................20

4.3.1 Electrical installation.......................................................................................20

4.4 Hot rooms ..........................................................................................................20

4.4.1 Authorized cable types ...................................................................................21

4.5

Rooms where there is a danger of fire...............................................................21

4.5.1

Inflammable materials....................................................................................21

4.5.2 Authorized cable types ...................................................................................22

4.6 Areas with an explosion danger .........................................................................22

4.6.1

Explosion danger areas .................................................................................22

4.6.2

Conductor installation.....................................................................................22

4.7 Areas endangered by explosives.......................................................................23

5 OUTDOOR ELECTRICAL EQUIPMENT....................................................................24

5.1

General ..............................................................................................................24

5.2 Equipment on building sites ............................................................................... 24

5.2.1

Safety.............................................................................................................24

5.2.2 Distributions units for building sites................................................................25

5.3 Fixed lights.........................................................................................................26

5.3.1

Cable..............................................................................................................26

5.3.2 Voltage requirement.......................................................................................26

5.4

Equipment for events at fixed or movable locations...........................................26

5.5 Connections for filming and television ...............................................................27

5.6

Vehicle connections ...........................................................................................27

5.6.1 Fusing ............................................................................................................27

5.6.2 Cable requirements........................................................................................27

5.6.3 Distribution units.............................................................................................28

6

LAYING AND MOUNTING CABLES..........................................................................29

6.1 General ..............................................................................................................29

6.2

Laying cables ..................................................................................................... 29

6.2.1 Cable temperature .........................................................................................29


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6.2.2 Bending radii ..................................................................................................29

6.2.3

Cable reel.......................................................................................................30

6.2.4 Laying cable...................................................................................................30

6.3 Cable connectors and terminations ...................................................................32

6.3.1 Making a resin filled connection .....................................................................33

6.3.2 Making terminations.......................................................................................33

7

BELLS - DOOR OPENERS........................................................................................34

7.1

Installation material ............................................................................................34

7.2 General description of low-voltage installations.................................................34

7.2.1 Bell transformers ............................................................................................34

7.2.2

AC bells.......................................................................................................... 34

7.2.3

Buzzer............................................................................................................34

7.2.4 DC bell ...........................................................................................................35

7.2.5

Electric door opener.......................................................................................35

7.2.6 Door intercom.................................................................................................35

7.3

Circuit examples ................................................................................................36


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LEARNING OBJECTIVES

The student should

- name two methods of connecting electric supply to a house

- describe the roof pole methods of cable entry to a house

- describe the construction, the size and the connections for a consumers meter panel

- name types of room and workshop requiring special installations

- state the protective area for bathtubs and showers

- name four insulation regulations for bathrooms and shower-rooms

- name the permitted cable materials for use outside, in the open or underground

- describe briefly the methods of laying and making connections to high current cables


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1 DOMESTIC CONNECTIONS

1.1 General

The type of connection to a domestic installation is determined the building plans

submitted before the building is started and the power requirements. The type and place

of connection is decided by the electricity supplier.

The cross section of the cable, used for the domestic connection should be such thatfuture extensions are possible.

If it is likely that there will be a later change from an overhead cable connection to an

underground cable connection, it is useful to provide a piece of conduit from the likely

place of the underground-cable entry in to the lowest floor distribution.

If motors above 1.1 kW, room heaters of 2.2 kW and other loads of above 3.3 kW are

present, the domestic connection must be a three-phase AC connection.

1.2 Types of domestic connection

a) Overhead-cable connections including two types:

1) Roof-pole connections

2) Wall-box connections.

b) Underground-cable connections.

c) Special connections.


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1.2.1 Overhead-cable connections

Overhead-cable connections can either be a roof pole-entry or a wall (wall-box) entry.

These are used mainly in inland areas.

1.2.1.1 Roof-pole entry

a) Whip type

1) Four lengths of conduit each 3 m long are clamped together at

approximately one metre from the bottom.

They are also clamped at the bottom by a

funnel-shaped sleeve to the elbow entry to thesupply fuse box. Approximately the upper two

metres of pipes are not clamped. The upper

end of the system is sheltered by a

hemispherical cap.

2) In order to connect the cable properly to the terminals of the supply fuses

on the one hand and to the overhead cable, on the other, the cable must be

approximately 1.5 metres longer than the pipe.


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b) Using flexible armoured-plastic conduit

In this roof-pole entry there is a separate run of individual cables in flexible armoured-

plastic conduit, 11 mm nominal diameter. The conduits must be taken to the edge of the

insulating cap of the roof-pole entry head, to the terminals of the fuses and to the neutral

terminal in the supply fuse box.

In order to connect the conductors properly, they must be approximately 1.5 metres longer

than the armoured-plastic conduit.

The end of the flexible-plastic

conduit are fixed by a bandage

or similar item


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c) Using individual double-sheathed cable

The individual, double-sheathed cables (specific roof cable, nominal voltage 1,000 V) are

laid in the roof-pole conduit and stress relieved from above.

The cables are taken in a flexible-armoured conduit, 36 mm nominal diameter from the

supply connecting box to the roof-pole conduit. In order to connect the cables properly,

they must be approximately 1.5 metres longer than the armoured-plastic conduit plus the

roof-pole conduit. The armoured-plastic conduit should have a hole below the roof-pole

conduit so that condensed water can drain away.


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1.2.2 Wall-box connection (facade connection)

Wall-box connections are also called "facade connections".

The domestic connection branches off from a distribution cable parallel to the house and

is taken inside the house through a conduit.

This conduit should have a downward slope to the outside, so that condensed water can

drain away to the outside.

The cables must be laid in a flexible armoured plastic conduit 11 mm nominal diameter.

These conduits must be laid as close as possible to the overhead-cable support and must

end, however, in the supply fuse box directly in front of the connecting terminals of the

fuses and the neutral-conductor terminal.

In order to connect the cables properly, these must be approximately 1.5 metres longer

than the flexible armoured-plastic conduit.


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1.2.3 Underground-cable connection

This type of connection is used mainly in City areas, where an underground cable is a

available or is laid for the supply. For underground entry into the building one must

provide a suitable space for connecting the cable which is accessible to the electric-supply

company.

For underground-cable connections, main cables in the cellar leading from the supply

connection box may only be laid in conduit mounted above the plaster. From the ceiling of

the cellar upwards, the main cables must be laid in ducts, conduit, channels or under the

plaster.

1.2.4 Special connections

a) Setra stress-relieved roof pole

b) Setra stress-relieved wall entry


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1.3 Guidelines for making connections

1.3.1 Safety

Domestic connections must be short-circuit-proof, fire-proof and secured against theft of

current. They must also resist atmospheric effects.

1.3.2 Inside connection

The cable between the overhead-cable terminals and the supply connection box is called

the "inside connection".

The minimum cross section is 10 mm of copper and must be kept as short as possible.

The domestic entry cable or inside connection can be a single cable or a multi-core

sheathed cable.

Consumer fuses are normally installed inside the building.

The proper fuses for the system installed must be of the correct size.

1.3.3 Pre-meter cables

Pre-meter cables are cables between the supply connection box and the meter,

The minimum cross section for cable is 6 mm of copper.

A greater cross section is recommended for later extensions.

1.3.4 Voltage drop

The voltage drop between domestic connection and meter panel may not exceed 1% of

the rated voltage.


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2 METER PANELS

2.1 General

The meter must always be mounted separately from the distribution device. In small

domestic installations (detached house), if the electric-supply company agrees, the meter

and consumers distribution unit may be installed on one panel.

The distribution fuses must always be situated above the meter.

Plugs, switches, and contactors may not be mounted on the distribution board with the

exception of circuit breakers.

All the equipment required for metering the power is situated on the meter panel. Thismay consist of meters (active and reactive power meters) time clocks and audio-

frequency carrier receivers. The size of the panel depends on the equipment required.

Minimum sizes are laid down for metering devices, which are stated as fixing areas of

sizes I, II and III.

2.2 Fixing areas

Minimum dimension

Width mm Height mm

Fixing area I 160 280

II 200 360

III 250 500

Fixing area I is used to accommodate the following

a) A single-phase watt hour meter

b) A time clock (up to 30 A)

c) A relay up to 30 A

d) Receiver for audio frequency control signals


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Fixing area II is used to accommodate the following

a) A three-phase meter watt hour meter up to 60 A

b) A time clock (above 30 A)

c) A relay (above 30 A)

d) Receiver for audio frequency control signals

Fixing area III is used to accommodate the following

a) A three-phase watt hour meter (above 60 A)

b) A meter current transformers

2.3 Type of fixing

2.3.1 Meter panels

Meter panels must be fixed in areas which are accessible at all times (stairways,

corridors).

In detached houses and blocks of flats or in farms the meter panel must be installed on

the ground floor.

The meter panel must be fixed so that the dials are not more than 1.6 metres above floor

level. This dimension can be reduced to 0.75 metres above floor level, if the meter panel

is fitted into a recess or box.

These boxes should have facilities for locking. This will under the control of the electricity

supplier.

2.3.2 Distribution Units

Distribution units manufactured in a factory and provided with meter panels (complete

distributors) must comply with the regulations as set forth in the country where they are

installed, and must be authorized by the electricity supplier. The distribution units can be

made of plastic or steel sheet.

Double insulation must be provided for steel-sheet distribution units as a protective

measure against voltage which is too high. Cables and earth leakage circuit breakers

must also be constructed with double insulation.


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The distance between the meter panels and the front plate of the distribution unit must be

at least 165 mm.

Meter panels not made in a factory must be hinged so that they can be opened to an

angle of at least 60. These panels are made of eternite or hardboard. According to the

regulations of the electricity supplier, the panel must be capable of being sealed closed

The panels must have a handle and a lock to facilitate opening and closing.

The required thickness of meter panels

Size of panel Design Material Thickness of panel

minimum in mm

Up to 1.2 m With or without angle

iron frame

Eternite

Hardboard

12

10

Over 1.2 m Without angle iron

frame

Eternite

Hardboard

15

12

Up to 1.5 m With angle iron

frame

Eternite

Hardboard

12

12

Over 1.5 m Made only with angle

iron frame

Eternite

Hardboard

15

12


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3 SWITCHING AND DISTRIBUTION PANELS

3.1 General

3.1.1 Distribution fuses

The distribution fuses (circuit fuses) which consist of a DIAZED or NEOZED fuses with

rating up to 63 A are mounted an these panels. Low-voltage, high-current fuses (NH) must

be used for currents above 63 A.

The cable from the supply must always be connected at the bottom connection of the

Diazed or Neozed fuse. Automatic circuit breakers may be used instead of fuses, but only

in conjunction with pre-fuses of 100 A maximum rating. Supply fuses, main fuses for each

floor of an apartment building and meter fuses connected before or after the meter are all

called pre-fuses.

3.1.2 Distribution panels

The distribution panels can be manufactured with a front plate which can be taken off.Otherwise they may be made of erenite or laminated plastic, but they must be hinged so

that they can be turned.

N.B. Wood must not be used for distribution panels.

It must not be possible to touch live parts while in operation. The distance between live

parts and the metalwork or house structure at the back of the panel must be at least 15

mm.

The individual circuits in the distribution unit must be labelled with their intended purpose.

Distribution fuses may only be mounted above meters. The fusing circuit must always be

positioned after the meter circuit.


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3.2 Voltage drop in distribution cables

The voltage drop must not exceed the following values on full load:

a) Voltage drop for lighting cables

From the meter to the lamps not more than 1.5 % of the nominal voltage may be

dropped.

b) Voltage drop for heating cables

From the meter to the heating equipment, not more than 3 % of the nominal

voltage may be dropped.

c) Voltage drop for power cables

From the meter to the motors, not more than 3 % of the nominal voltage may be

dropped.d) British I.E.E. regulations

For final circuits protected by an overcurrent device rated at not more than 100 A,

the voltage drop from the origin of the circuit must not exceed 2.5 % of the nominal

voltage.


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4 INSTALLATION IN SPECIAL AREAS

4.1 Special rooms and workplaces

The following are regarded as special rooms and workplaces:

a) Rooms which are occasionally damp (bathrooms, showers in flats)

b) Damp and wet rooms (communal baths)

c) Hot rooms

d) Rooms where there is danger of fire

e) Rooms where there is danger of explosion

f) Rooms where there is danger from explosivesg) Farms

h) Garages

i) Electro-medical rooms

4.2 Rooms which are occasionally damp (bathrooms)

Cables going through bathrooms or shower rooms may only be used for supplying other

rooms if they are laid at least 2.25 metres above floor level.

4.2.1 Area of protection

The area of protection in a bath or shower is 0.6 metres an all sides, and 2 metres from

floor to ceiling. Switches or socket outlets may not be fitted within this protected area.


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The exception to these regulations include fitted switches for water heaters and socket

outlets with isolating transformers up to 25 VA (shaver points). They are marked

4.2.2 Protective earthing

A conducting bathtub (or shower trough) must be connected with a copper wire of a least

6 mm area between the outlet and the freshwater pipe.

4.2.3 Installation of electrical appliances

Electric heaters need not be protected by drip-proof enclosures but their lower edges must

be at least 2 metres above floor level.

All movable equipment, including movable heaters used in bathrooms must be double

insulated. Exceptions are washing machines and spin driers.

4.2.4 Permitted types of cable installation

a) Under plaster

Cables in conduit (PVC), YM-cables and material for use under plaster

b) On top of plaster

Only YM-cables may be laid an insulating camps and only material suitable for damp

areas may be used

Twin parallel leads may not be used in bathrooms.


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4.3 Damp and wet rooms

Damp and wet rooms where there is dampness (formation of condensed water).

Damp and wet rooms include the following areas:

a) Laundries e) Stables

b) Communal baths f) Greenhouses

c) Dairies g) Wet workshops etc.

d) Refrigerated rooms

4.3.1 Electrical installation

Only cables or sheathed cables (damp area cables), damp area sockets and damp area

fittings may be used for electrical installations in such rooms. Screwed connections in

damp areas must be sealed with damp area putty. Fixing screws of fittings must also be

protected against dampness.

The transition from damp area cables to conduit may only take place outside the damp

area. Lamps must have 1 P 5 protection (drip-proof) and be provided with protective

windows.

In areas with acid vapour, sheathed cables should not be laid in or under plaster, but

should be laid outside these areas as far as possible. Only short spurs should be laid in

this type of area.

4.4 Hot rooms

These are rooms where temperatures above 35C occur. They may also be wet or damp,

and include the following:

a) Saunas d) Drying rooms

b) Heated rooms e) Smelting chambers

c) Boiler houses


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4.4.1 Authorized cable types

Normal cables may be used up to 55C ambient temperature. However, the current

through them must be reduced according to the following table:

Room temperature C correction factor

for current carrying capacity

30 92

35 85

40 75

45 65

50 53

55 38

In rooms where there are temperatures above 55C, only cables with increased thermal

resistance may be used.

At temperatures above 85C cables with asbestos insulation or mineral insulated cable

should be used.

4.5 Rooms where there is a danger of fire

These are rooms or areas where there is a danger of easily inflammable materials

touching electrical material, so that the higher temperatures of these materials constitute a

danger of fire.

4.5.1 Inflammable materials

Inflammable materials include the following:

a) Paper e) Wood shavings

b) Textiles f) Cotton

c) Hay g) Wool fibres

d) Straw h) Wood


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4.5.2 Authorized cable types

Cable in plastic conduit, flexible plastic conduit under the plaster, armoured conduit or

cable with flame-resistant sheath may be used for electrical installations.

All cables to a room where there is a danger of fire must have all poles capable of being

switched off at an easily accessible place.

4.6 Areas with an explosion danger

These are areas where gases, vapours or dust can gather forming explosive mixtures on

their own or with air.

4.6.1 Explosion danger areas

Areas where there is a danger of explosion include areas for storing or processing the

following items:

a) Benzene e) Ether

b) Benzol f) Alcoholc) Petrol g) Gas

d) Spirits h) Synthetic resin varnish

They also include garages and petrol stations, pits in garages.

4.6.2 Conductor installation

Installations in these areas are carried out using cables or similar conductors which can

be switched off outside the potentially explosive area.

Explosion-proof equipment (with the sign "Ex"), locked with triangular headed set-screws,

is used for this type Installation.


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4.7 Areas endangered by explosives

These include areas where explosives, igniters, ammunition or fireworks are

manufactured, processed or stored.

If there is a path to an adjacent room through windows, doors or wall openings, the

adjacent room is also regarded as potentially explosive.

There are official regulations for such areas.


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5 OUTDOOR ELECTRICAL EQUIPMENT

Outdoor electrical equipment includes the following:

a) Equipment on building sites

b) Fixed lighting

c) Equipment for events at fixed or moving locations

d) Connections for filming and television

e) Vehicle connections

5.1 General

Before starting installation work, the electricity-supply company determines the point or

connection to the distribution network. Only cables, sheathed conductors, Setra (self

supporting) cables or conductors mounted between insulators (overhead wires) may be

used for permanent cables.

Only rubber-sheathed conductors or plastic-insulated conductors of medium-heavy design

may be used for movable cables.

On building sites, such cables must be of heavy design.

The type of protection for fixed lights or equipment as well as for movable lights or

equipment must comply with local safety regulations.

5.2 Equipment on building sites

5.2.1 Safety

A building-site distributor is a distribution box which is used during construction of a

building and must comply with the local safety regulations. For metal cubicles all

equipment before the FI protective switch must be double insulated.

Strip or deep earths are mainly used as earth. lf there are foundation earths available in a

new building, then these connections are used for earthing the building-site distributor.


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If concrete vibrators or tile-grinding machines are used an building sites, they must be

operated either at low voltage (42 V), or via a protective isolating transformer (transformer

with separate windings) at voltages above 42 V.

Connection-distribution cubicles are recommended for small building sites. This means

that the supply connection, meter and distribution equipment are accommodated in one

cubicle.

For heavier loads, it has proved better to divide this into separate connection and

distribution cubicles.

5.2.2 Distributions units for building sites

Distributors at building sites with rated currents of 25, 63, 100 and 250 Amps arepreferred.

A permanent wiring diagram must be fixed inside the distribution unit.


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5.3 Fixed lights

Fixed lights include the following type of installation:

a) Facade lights

b) Christmas illuminations

c) Christmas-tree lights

d) Flower-bed illumination

e) Underwater lights

5.3.1 Cable

Cable or sheathed cable is to be used for installations. Apart from cables, lighting cables

can be used for temporary fixed lighting (e.g. Christmas-tree lights).

The fittings in accessible areas or out of doors must be made of plastic (insulating

material).

5.3.2 Voltage requirement

Low voltages should be used, if possible, for fixed lighting out of doors.

5.4 Equipment for events at fixed or movable locations

This type of location include the following:

a) Circus

b) Festivals

c) Exhibition halIs

d) Markets

Advertising lighting at these events is treated as fixed lighting.


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For such events, the cables should be laid in buildings, according to the regulations for

rooms where there is a danger of fire. Joints must be protected from being accidentally

broken. Meters must be protected against the effects of weather.

5.5 Connections for filming and television

These connections must first be discussed with the electricity supplier, who will decide

whether a meter should be installed.

Such connections are made in existing domestic connections an the supply side of the

supply fuses and are provided with their own supply fuse. If searchlights are being used,

there should be no inflammable material in these areas.

5.6 Vehicle connections

Vehicle connections include the following:

a) Caravans

b) Show cars

c) X-ray vehicles

d) Exhibition vehicles

5.6.1 Fusing

A sealable supply fuse must be mounted near the connection to the distribution network of

the electricity supplier.

5.6.2 Cable requirements

A sheathed cable of medium design is used for the connecting cable. These cables must

be protected from mechanical damage.


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5.6.3 Distribution units

Camping site distribution units are also suitable for annual fairs and exhibitions.

The connecting cable between distributor and load should not be more than 25 metres

long.


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6 LAYING AND MOUNTING CABLES

6.1 General

Supply cables are used to transmit electrical energy over long distances. Power cables

are mainly used for electrical installations.

The cables may be laid in the ground, in water or in the open.

In densely populated areas, the cables are always laid underground. Paper and plastic

material are used as insulation for cables.

Cables with paper insulation require a sealed waterproof sleeve, which is usually made of

lead.

6.2 Laying cables

6.2.1 Cable temperature

When laying cables, the cable temperature should not be lower than +5 C. At lower

temperatures, the cables should be stored in a heated room at least for one day prior to

laying.

6.2.2 Bending radii

The minimum permissible bending radii are given below.

There are two basic types of supply cable Paper and plastic insulated cables.

Da= outside diameter of cable (mm)


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6.2.3 Cable reel

The supply-cable reel should be transported as near as possible to the place of use. The

drum should not be rolled. When reeling, the cable may only be unreeled from drums

mounted with bearings and the cable must be taken from the top and reeled in the same

direction.

The cable must be kept taut, but not over-tensioned and must not be pulled over edges or

in a curve.

If the supply cable reel cannot be brought to the equipment, then one should unreel via

guide rollers. A pulling rope and cable grip should be used.

6.2.4 Laying cable

Depths for laying cables are generally 60 to 80 cm (for high-voltage cables 0.8 to 1.2

metres). If pipelines are to be crossed, the cable trench should be dug gradually deeper

so that the cable will lie under these pipelines. Before laying the cable, the cable trench

should be checked for width, depth and absence of rocks. The cable trench should be

filled to a depth of 10 cm with bedding material or sand. The cable can then be laid, so

that there is some resilience in case of changes of length due to temperature or earth

movements. In order to protect the cable, it is covered by bricks or covers before filling in

the cable trench.

A yellow marker strip is laid about 30 cm below the surface.


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1. soil

2. yellow marker

3. cable

4. sand bed

5. cover brick

If several power cables of up to 1 kV voltage rating are to be laid in one trench, then they

must be spaced by at least 6 cm apart. When laying several cables with a rating above 1

kV in one trench, these cables must be separated by bricks.

The cable must be laid through a clay, concrete or iron pipe when entering a building.

1. soil

2. yellow marker

3. sand bed

4. cover bricks

5. cables up to 1 kV rating

6. cables above 1 kV

NOTE

Single-core cables may not be pulled through closed metal conduit (induction voltages). Ifa metal conduit is used (e.g. when passing through walls) then this must have a cut a long

its length.


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6.3 Cable connectors and terminations

Cable connections, T-offs and cable ends are made with their connections and

terminations in a mould filled with resin. With oil impregnated paper insulated cables,

moisture must be prevented from entering and oil from leaking.

a) Resin filled connections

1) Connections

2) Tee junctions

1. tape 8. wire binding

2. half-lapped tape 9. string binding

3. resin 10. compression screw terminals

4. mould 11. plastic sheathed cable

5. lead sheath 12. soldered connection

(cleaned with grease-free solvent) 13. tee-off clamp

6. steel cable sheath

(cleaned with grease-free solvent)

7. paper lead cable with jute sheath


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b) termination

1. tape 8. wire binding

5. lead sheath 9. string binding

(cleaned with grease-free solvent) 10. soldered connectors

6. steel sheath 11. plastic sheathed cable

(cleaned with grease-free solvent) 14. conductor with Y type -

7. paper insulated lead cable with jute sheath insulation

6.3.1 Making a resin filled connection

a) Strip the cable and make the electrical connection.

b) Clean the cable sheaths and wind with tape.

c) When mounting the half covers, first cut the sleeve ends to the cable diameter.

d) Seal the mould ends with some layers of tape. Set the funnels an the openings

provided.

e) Mix the resin for about 2 minutes and then pour into the lowest funnel.

f) When the resin has hardened, saw off the funnel.

6.3.2 Making terminations

Terminations are made in a manner similar to resin sleeves. In order to obtain good

sealing, the cores must be taped where they pass through the termination cap, and the

insulation removed for a certain distance, for outside terminations, so that resin can

penetrate and seal the cables.


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7 BELLS - DOOR OPENERS

This equipment is usually operated from a bell transformer fed from the supply

7.1 Installation material

Signal cables (bell wires) are used as installation material, utilizing the following

dimensions:

a) For cables up to 50 metres long the cable diameter is 0.6 mm

b) For cables up to 100 metres long the cable diameter is 0.8 mm

c) For cables up to 160 metres long the cable diameter is 1 mm.

This type of cable must not be used for lighting.

7.2 General description of low-voltage installations

7.2.1 Bell transformers

Bell transformers are short-circuit proof and give a voltage of 3, 5 and 8 V and a short-

circuit current of 1 to 3 A.

There are bell transformers with higher secondary voltages, e.g. 5, 10 and 15 V.

7.2.2 AC bells

The iron armature of the bell vibrates due to the alternating magnetic flux and this the bell

7.2.3 Buzzer

The construction is the same as that of the bell. Instead of a bell, the buzzer has a

resonant metal sheet.


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7.2.4 DC bell

The current flows through the coil of the DC bell. The armature is attracted and hits the

bell. The current is interrupted by a contact which is normally closed and the armature

drops off. This process is repeated.

7.2.5 Electric door opener

The electric door opener is taken for granted in modern flats. It guarantees the safety of

the door which is always closed, and makes it convenient to open and monitor the door

from the fiat.

Doors with electric door openers have only one door knob.

The doors are locked and can be opened either electrically with a door-opening push-

button or mechanically with a key or from inside with the door handle.

When the door is opened electrically, a buzzing noise can be heard.

7.2.6 Door intercom

This is designed for verbal communication between the main entrance of a block of flats

and an individual fiat. It consists of a weatherproof microphone-loudspeaker combination.

The speaker in the flat has a pushbutton which operates the door opener. It is not possible

to speak from one flat to another.

The inhabitants of the flats may communicate with a person at the door via a loudspeaker

at the main entrance to the block of flats. The volume at the front door can be increased

with the aid of a transistor amplifier.

For flats on busy roads with a lot of traffic noise, an amplifier must be provided.


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The operating voltage of the door intercom equipment is usually 6 to 8 volts.

Schematic diagram

7.3 Circuit examples

a) Bell and door opener


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b) Door intercom and door opener


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EE 022

Electrical Installation 2

Theoretical Test


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EE 022


TEST 1

QUESTIONS:

1. What factors determine the type of domestic connection to be used?

2. State the requirement for laying main cables in a cellar leading from the supply

connection box.

3. Explain the term "premeter cable".

4. What is the minimum distance between meter panels and the front plate of the

distributor?

5. What is the maximum permissible voltage drop from the meter to the load for power

cables on full load?

6. What are the dimensions of the protection area in bathrooms?

7. Name at least 4 types of electrical equipment that may be used in the open (outdoors).

8. State the lowest permissible cable temperature when laying cables.

9. State the rule to be followed when laying two or more supply cables, for above 1 kV, in

the same trench.

10. State the principle of operation of an AC bell.


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EE 022


TEST 2

QUESTIONS:

1. State the basic types of supply connection.

2. State the basic construction characteristics for roof-pole entry using flexible armoured-

plastic conduit.

3. What is the maximum permissible voltage drop between supply connections and

meter panel?

4. Explain the term "pre-fuses".

5. Name at least six "special areas" for installation.

6. Explain the term "hot rooms".

7. State two main types of insulation for supply.

8. Explain the term "connection distribution cubicle".

9. What is the minimum distance between cables of up to 1 kV when more than one are

laid in the same trench?

10. Name at least five types of low-voltage installation.


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EE 022


TEST 3

QUESTIONS:

1. Which type of supply connection must be used if loads of above 3.3 kW are present?

2. State the main construction characteristics of a wall-box supply connection.

3. Explain the term "fixing area" in a distribution unit. Name the different fixing area

designations.

4. State the maximum permissible voltage drop from the meter to the load for lighting

cables on full load.

5. May switches or socket outlets be installed in the protected area of a shower or bath ?

6. State which type of cable may be used for a room where temperature is:

a) 55 to 85 C

b) above 85 C

7. In which situations are connector-distribution cubicles used?

8. State the depth for laying cables for up to 1 kV.

9. State the sequence of layers which will be found when digging down into a cable

trench.

10. State the principle of operation of a DC bell.


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EE 022


TEST 4

QUESTIONS:

1. Approximately how much longer must the cable be than the pipe in a whip-type roof

pole entry?

2. Explain the term "inside connection".

3. Where must meter panels be placed?

4. State the maximum allowable voltage drop from the meter to the load for heating

cables on full load.

5. In what places must switches or socket outlets NOT be used in a bathroom?

State any exceptions

6. State which type of installation must be used in a petrol station.

7. State the provision under which normal cables can be used in hot rooms.

8. State the depth for laying high-power cables.

9. Explain the procedure in laying cables.

10. Draw a schematic diagram of a door intercom.


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EE 022


TEST 1

SOLUTION:

1. The building plans submitted and the power requirements.

2. For underground-cable connections, main cables leading from the supply-connection

box may only be laid in conduit mounted above the plaster. From the ceiling of the

cellar upwards, the main cables must be laid in ducts, conduit, channels or under the

plaster.

3. Premeter cables are cables between the supply connection and the meter.

4. 165 mm.

5. 3% of the nominal voltage.

6. 0.6 metres on all sides and 2 metres from the floor to the ceiling.

7. Fixed lighting, vehicle connections, equipment on building sites, connections for

filming and television etc.

8. +5 C.

9. They must be separated by bricks.

10. The iron armature of the bell vibrates due to the alternating magnetic field and hits the

bell.


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EE 022


TEST 2

SOLUTION:

1. Overhead cable connections (roof -pole, wall-box connections); underground cable

connections; special connections.

2. There is a separate run of individual cables in flexible armoured-plastic conduits. The

conduits are taken to the edge of the insulating cap of the roof-pole entry head and to

the supply fuse box.

The conductors must be 1.5 m longer than the armoured-plastic conduits.

3. 1% of the rated voltage.

4. Pre-fuses are supply fuses, main fuses for floors in apartment buildings and meter

fuses, connected before or after the meter.

5. Bathrooms, communal baths, hot rooms, farms, garage, damp and wet rooms, rooms

where there is danger of fire, rooms where there is danger of explosion, electro-

medical rooms.

6. Hot rooms are rooms where temperatures above 35 C occur.

7. Paper and plastic-insulated cables.

8. Connection-distribution cubicle is a cubicle that accommodates both the meter and

distribution equipment.

9. 6 cm.

10. AC bells, buzzers, DC bells, door intercom and electric door openers etc.


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EE 022


TEST 3

SOLUTION:

1. Three-phase AC connection.

2. The supply connection branches off from a distribution cable parallel to the house and

is taken inside the house through a conduit. The cables must be laid in flexible-

armoured plastic conduits which must be laid as close as possible to the overhead-

cable support and must end in the supply fuse box. The cables must be 1.5 m longer

than the flexible armoured-plastic conduits.

3. Fixing areas are areas that accommodate metering devices. Fixing areas I, II and III.

4. 1.5 % of the nominal voltage.

5. No.

6. a) Cables with increased thermal resistance,

b) Cables with asbestos or mineral insulation.

7. Small building sites.

8. 60 - 80 cm.

9. Sequence: soil, yellow marker, soil, cover brick, cable, sand bed.

10. The current flows through the coil. The armature is attracted and hits the bell. The

current is interrupted by a contact which is normally closed. Therefore, the armaturedrops off. This process is repeated.


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EE 022


TEST 4

SOLUTION:

1. Approximately 1.5 metres.

2. "Inside connection" is the cable between the overhead-cable terminals and the supply

connections.

3. Must be placed in rooms which are accessible at all times.

4. 3% of the nominal voltage.

5. In the protective area (0.6 metres on all sides of a bath and 2 metres from floor to

ceiling). Exceptions: fitted switches for water heaters and socket outlets with

transformers up to 25 VA.

6. Installation with explosion-proof equipment.

7. Only if their current rating is corrected by a factor dependant on the temperature. This

relationship can be found in the appropriate standards.

8. Generally 0.8 to 1.2 metres.

9. The cable trench is dug and is filled to a depth of 10 cm with bedding material or sand.

The cable is laid so that there is some resilience in case of changes of length and is

covered by bricks before filling in the cable trench. A yellow marker is laid about 30 cm

below the surface.


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TEST 4 - answers continued ...

10.


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KEY TO EVALUATION

PER CENT MARK

88 100 1

75 87 2

62 74 3

50 61 4

0 49 5

ee022-electrical installation 2-th-inst.pdf

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