1. ELECTRICAL SERVICES
By 11627

2. • ELECTRICITY :-- Electricity is a general term that encompasses a
variety of phenomena resulting from the presence and flow of electric
charge .

3. • Electrical distribution and protection
equipments :-1. Fuses :-

4. • A fuse consists of a metal strip or wire fuse element, of small cross-section
compared to the circuit conductors, mounted between a pair of electrical
terminals, and (usually) enclosed by a non-conducting and noncombustible housing.
• Protect electrical devices and components from overcurrent and short
circuits that occur during inproperly operating circuits.
• When fault current reaches a predetermined magnitude for a fixed period
of time,current flow is interrupted through melting of an internal element.
• Performance rating include voltage rating, current rating, rated breaking
capacity.
• Performance characterstic : Fast acting and time lag.
• The fuse element is made of zinc, copper, silver, aluminum, or alloys to
provide stable and predictable characteristics.

5. • Fuse Types :1. Miniature fuse :-
Commonly available in dimensions of
5 x 20 mm and 6.3 X 32 mm

6. 2. Sub-miniature or micro :Compact circuit board layout.
Mainly 13-32 inch diameter fuses.

7. 3. Automotive Fuse :Automotive fuses are a class of fuses used to protect the wiring and
electrical equipment for vehicles. They are generally rated for circuits no
higher than 24 volts direct current, but some types are rated for 42-volt
electrical systems. They are occasionally used in non-automotive electrical
products.

8. 4. Blade Type Fuses :Plug-in fuses (also called blade or spade fuses), with a plastic body and
two prongs that fit into sockets, are mostly used in automobiles .
Used in low voltage and high current applications.
Type
Dimensions L x W x H
Ampere ratings
Mini
10.9 x 3.6 x 16.3 mm
2A, 3A, 4A, 5A, 7.5A, 10A, 15A, 20A,
25A, 30A
Low-Profile Mini
10.9 x 3.81 x 8.73 mm
2A, 3A, 4A, 5A, 7.5A, 10A, 15A, 20A,
25A, 30A
Regular
19.1 x 5.1 x 18.5 mm
1A, 2A, 3A, 4A, 5A, 7.5A, 10A, 15A,
20A, 25A, 30A, 35A, 40A
Maxi
29.2 x 8.5 x 34.3 mm
20A, 30A, 40A, 50A, 60A, 70A, 80A,
100A

9. • FUSE HOLDER :-
Fuse holder are devices for
containing,protecting and mounting fuses.

10. 1. Open fuse holder :- Open fuse holder types are fuse claps,
fuse blocks, socket and plug on cap varieties.
2. Fully enclosed :- Fully enclosed variety may use a fuse carrier
that is inserted into a holder or have other means to fully enclosed the fuse.

11. • Circuit Breaker :- Circuit breaker are switching device capable of
making, carrying and breaking current under normal circuit conditions and
making, carrying for a specific time, and breaking current under specified
conditions such as a short circuit.
• A circuit breaker is an automatically-operated electrical switch designed
to protect an electrical circuit from damage caused by overload or short
circuit. Its basic function is to detect a fault condition and, by interrupting
continuity, to immediately discontinue electrical flow. Unlike a fuse, which
operates once and then has to be replaced, a circuit breaker can be reset
(either manually or automatically) to resume normal operation.

12. • Actuator lever - used to manually trip and reset the circuit breaker. Also
indicates the status of the circuit breaker (On or Off/tripped).
• Actuator mechanism - forces the contacts together or apart.
• Contacts - Allow current when touching and break the current when
moved apart.
• Terminals
• Bimetallic strip
• Calibration screw - allows the manufacturer to precisely adjust the trip
current of the device after assembly.
• Solenoid
• Arc divider / extinguisher

13. • Circuit Breaker

14. • TyPES OF CIRCUIT BREAKER :Low voltage circuit breaker:-1.
MCB [miniature circuit breaker]:- rate current more than 100 A.
Trip characterstic normally not adjustable. Thermal or thermal –
magnetic operation.
2.
MccB [molded case circuit breaker] :- rated curent up to 1000 A. Thermal
or thermal magnitude operation. Trip current may be adjustable in large
rating.

16. • WIRES :- A wire is a single, usually cylindrical, string of metal. Wires
are used to bear mechanical loads and to carry electricity and
telecommunications signals. Wire is commonly formed by drawing the
metal through a hole in a die or draw plate .

17. • Classified based on material :• Copper :- Very good conductor and is easy to mold and bend.
Most commonly used.
Reasonable Price.

18. • ALUMINIUM :-
Cheaper and easy to shape and bend,
A less conductive material.
Electrical safety is an issue.
Heating occurs.

19. • ALLOYS :- An alloy made from aluminium and copper to take
advantage of both.

20. • SILVER WIRES :- Best conductor of electricity .
It is too expensive.

21. • CLASSIFICATION BASED ON USE :1. Triplex Wire :- It is arial cable uses to fed the power pole.
Wire ties to the wires sticking out of the weather
head.

22. 2. Main Feeder wires :- These wires are usually type THHN
wire and rated for 125% of the load required. These are usually black
insulated wires coming out of the service weather head.

23. • Panel Feed Wires :- These wires are also type THHN like the
main feeder . A typical 100 A servicewould have a THHN set of wires. They
would then be rated at 125 A. This would protect the wires if the
amperage was at full 100 A.

24. • Non-metallic sheathed wire :- This wire commonly
called Romax. Is a plastic coated wire that has either 2 or 3 conductors.

25. • Single Strand wires :- when your home is piped you will have
to have another type of wire. Single strand wire is insulated and many of
these can be pulled into the same pipe.

26. • Bus Bars :- An aluminium or copper conductor supported by
insulators that interconnects the loads and the source of the electrical
power in an electric power system.
1. Rigid bus bars :-Low,medium and high voltage.
Sulphur hexafluoride.

27. • Switches :- Devices used to allow electrical current to flow. When closed
and when opened,they prevent current flow.
Common Switch Types :Push button
Rocket Rock
Toggle
Dual line
Rotary
Keylock
Slide
Snap action
Reed

28. • Wiring :- Electrical wiring in general refers to insulated conductors
used to carry electricity, and associated devices.
Types of wiring :1 . Cleat Wiring:-Types of wiring to be adopted is depends upon
various factors,duarability,safety,appearance,cost,consumers budget etc
This system uses insulated cables sub protected in porcelain cleats.
Recommended only for temporary installations.
Cleats are made in pairs having bottom and top halves.
initially top and bottom cleats are fixed according to the layout. Then
the cable is drawn , tensioned and cleats are tightened by screw.

29. • Types :- Having 1,2 or 3 grooms to receive 1,2, or 3 wires.
• Advantages :Cleat wiring is one of the cheapest wiring.
More suitable for temporary installation
When not required the wiring could be dismanteled without damaging
cables,cleats and accessories.
Disadvantages:Wiring is exposed chnces of fire are there.
Not appealing
Less durable

30. • B.I.S recommendations for cleat wiring :Not employed for wiring on damp walls or ceiling unless precautions are
adapted for affectively preventing dampness.
Class of cables :- vulcanised rubber insulated cables, pvc and
poluthene insulated cables, insulated cables could be used without any
further protection.
Cleats :- All cleats should consist of two parts a base piece and a
cap. Cleats shall be fixed at a distace more than 60 cm apart and at regular
intervals.Cleats shall be inserted either with varnished wood fillets or
varnished wood clamps.

31. • Fixing of cleats :- IN ordinary cases cleats shall be attached.
Cleats shall be such that conductor distance shall not be less than 2 cmfor
pressure upto 250 volts
Branch load :- 2.5 cm apart
Sub-mains :- 4 cm apart

32. • Batten wiring :- Tough rubber sheathed or pvc sheathed cabled
are suitable to sum on teak wood battens
Metal sheathed wires are used.
teakwood shall be seasond and wel finished from all sides. Shall not be
less than 10 mm in thickness
battens shall be painted with vanish prior to erection.
Battens shall be fixed to wallas using wall plug or wooden plug not more
than 75 cm
Cables are held on battens.
Link Clip :- use to family clipping the cables in position.

33. • Link Clip :- use to family clipping the cables in position.
link clips are of two types.
made of tin or brass coated tin.
ADVANTAGES :- easy to install.
widely used for indoor installations.
DISADVANTAGES :- Wires are exposed more chances of damage.
Chances of spreading fire are more.
not much appealing.

34. • Cassing caping wiring :- For low voltage installation.
cables like vulcanised rubber,insulated cables,plastic insulated cables are
used and carried within the wood casing enclosure
Not to be used in un ventilated or dap places . Unless precautions are
taken.
Material and pattern of casing :all casing shall be of fust glass, seasoned teak wood or any other
approved hardwood.
all sides well varnished,both inside or outside shealed varnish.

35. • Advantages :- Wires not fully enclosed ,less chances of damage.
•
•
chances of fire spreading are less
better asthetically appealing.
Disadvantages :-Expensive.
only used in dry places.

36. • Conduit wiring :- conduit is defined as a tube or channel.
•
Tubular conduit is most commonly used installation.
• Types of conduit :• Rigit steel conduit.
• rigid non-mettalic conduit.
• Flexible steel conduit.
• Flexible non mettalic conduit.

37. • Surface conduit :- conduit shall be finished with galvanised or
stone surface.
• Conduit accesories shall be threaded type and conduit shall be fixed using
screwed couplers and accessories at a distance not more than 1 m and 30
cm in case of bends.
• Diameter not less than 16 cm
• For long runs : use inspection type couplers.
Advantages :- Fire protection
Water Proof
easy replacement of defective wires.
• Disadvantages :- Expensive wiring
•
mostly used in factories only.