Electric switch gear type description.

1. Unit-5
Electrical Installations
Presented by
Mr. K. Shankar

2. Syllabus
• Components of LT Switchgear
• Types of Wires & Cables
• Concept of Earthing
• Types of Batteries & Characteristics
• Energy consumption calculations
• Power factor improvement methods
• Battery backup

3. Switch-Gear
• Switchgear is responsible for connecting and disconnecting
the electric power supplies from other systems.
• Switchgear is a general term used to covers the switching
device and its various combinations with some associated
control, measuring all parameter, protective and regulating
equipment, together with accessories, enclosures and
supporting structures

4. Classification of Switchgear
Depending upon the voltage to be handled, switchgear can be
classified into
1. Outdoor type Switchgear
2. Indoor type Switchgear
Outdoor type switchgear:
• For voltages beyond 66kV
• Space required for the accessories ( circuit breakers, transformers, switches) is
not economical.
Indoor type switchgear:
• For voltages below 66kV
• All parts are enclosed in metal casing.

5. Classification of Switchgear
Depending upon the voltage level, Switchgear can be classified
into
1. Low voltage switchgear (up to 1000V AC & 1500V DC)
2. Medium voltage switchgear ( 3.3 kV to 33 kV )
3. High voltage switchgear ( Above 36 kV )

6. Components of LT Switch Gear
• SFU (Switch Fuse Unit)
• MCB (Miniature Circuit Breaker)
• MCCB (Moulded Case Circuit Breaker)
• ELCB ( Earth Leakage Circuit Breaker)

7. SFU (Switch Fuse Unit)
• The switch fuse units are used for distributing power and protecting
electrical devices and cables from damage due to fluctuations. This fuse
unit is housed in an enclosure made using quality CR steel sheet
Salient Features:
• Pre-treated or powder coated finish
• For cable connections, knock outs are provided at
bottom, top and rear side
• High conductivity due to nickel or silver plated contact
• Durable and rewirable.
Application: used in industrial, residential and commercial buildings for
electrical fittings

8. Fuses
• Fuse is an electrical safety device that operates to provide over
current protection of an electrical circuit. Its essential component is
a metal wire or strip that melts when too much current flows through
it, therby stopping or interrupting the current.
Types of fuses:-
• Rewirable or Kit-Kat type fuse unit
• Cartridge type fuse unit
• HRC type fuse unit
• Semiconductor type fuse unit

9. Rewirable or Kit-Kat type fuse unit
• The fuse base is generally made up of
porcelain
• Fuse element is made up of tinned copper,
aluminium etc
• When the fuse is blown due to over
current, we can easily remove the fuse
carrier and replace the fuse wire.
• They are most commonly used in house
wiring, small industries and other small
current applications

10. Cartridge type fuse unit
• A cartridge fuse including a tubular insulating
body
• Integrally formed ferrule terminals secured
over the respective ends of the insulating body.
• A fusible strip extending within the insulating
body electrically interconnecting the ferrule
terminals.
• They are available up to 600A and 600V AC
and widely used in industries, commercial as
well as home distribution panels.

11. HRC type fuse unit
• HRC-High Rupturing Capacity
• HRC Fuse consists of highly heat resistant material (such as
ceramic) body having metal-end caps, which is welded by silver
current carrying element.
• The fuse body internal space is completely packed with a filling
powder which may be plaster of Paris, quartz, chalk, marble, dust
and cooling mediums etc.
• The heat produced under abnormal condition vaporizes the silver
melted element. Chemical reaction taking place between silver
vapour and filling powder results in high resistance substance,
which helps in quenching the arc in fuse
• HRC fuses are also available in a capacity of 16000A to 30000A at
400V
• HRC Fuses are also used for protection on low voltage distribution
systems against overload and short circuit conditions

12. Semiconductor type fuse unit
• A semiconductor fuse is simply a very fast
acting conventional fuse, designed to
prevent damage to a semiconductor device
• It is usually used with larger semiconductor
devices rated to switch 100A or more
(SCRs, IGBTs, Power transistors, etc.)
• The I2t of the semiconductor fuse is less
than the I2t of the semiconductor device and
thus the fuse gets blown off before the
device fails.

13. MCB
• MCB – Miniature circuit breaker. It
automatically switches OFF electrical
circuit during any abnormal condition in
the electrical network such as overload
& Short circuit conditions
• The MCB is an electromechanical device
which guards the electric wires &
electrical load from over current so as
to avoid any kind of fire or electrical
hazards.

14. Working of MCB
• Whenever continuous over current flows through
MCB, the bimetallic strip is heated and deflects
by bending. This deflection of bimetallic strip
releases a mechanical latch.
• But during short circuit condition, the current
rises suddenly, causing electromechanical
displacement of plunger associated with a
tripping coil or solenoid
• The plunger strikes the trip lever causing
immediate release of latch mechanism
consequently open the circuit breaker contacts.
• To restart the flow of current the MCB must be
manually turned ON.

15. MCCB
• MCCB- moulded case circuit breaker
• It is a protecting device which protects the circuit
form overloading, short circuit faults and for
switching the circuits.
• It is mainly used in a place where adjustable tripping
requires.
• the current rating of MCCB is up to 2500A. It is
mainly used for high current applications.
• The MCCB are used for high energy applications.
• MCCB can be used for protection of generator
protection and main electric feeder distribution.

16. ELCB (Voltage operated ELCB)
• ELCB- Earth Leakage Circuit breaker
• ELCB is basically an electrical wiring
device that disconnects the circuit
whenever there is leakage of current flow
through the human body or the current is
not balanced between the phase conductor.
• It is the safest device to detect and trip
against electrical leakage currents, thus
ensure protection against electric shock
caused by direct contacts.

17. RCCB (Current operated ELCB)
• RCCB – Residual current circuit
breaker.
• The polarity of the phase winding
and neutral winding on the core is
so chosen that in normal condition
MMF of one winding opposes that
of other.
• Under fault condition there is
difference in to MMF so a
resultant flux exists and trip coil is
energized.
• Trip coil further isolated the
supply to the load.

18. Difference between wire and cable
• Wire and cable are two terms that are used in electrical and
communication fields.
• A wire is a single conductor strand or a group of conductor strands(copper
or aluminium) while cable is two or more insulated wires wrapped in one
jacket.
• Multiple conductors that have no insulation around would be classified as
a single conductor.

19. Types of wires
• Wires can be classified into four types:
– Single strand wires
– Multi strand wires
– ACSR
– AAAC

20. Single strand wires
• Single strand wire also uses THHN
(thermoplastic high heat resistant
nylon coated) wire, though there are
other variants. Each wire is separate
and multiple wires can be drawn
together through a pipe easily.
• Single strand wires are the most
popular choice for layouts that use
pipes to contain wires.

21. Multi strand wires
• Multi strand wiring is more flexible
and less susceptible to cracking and
metal fatigue than single stranded
conductors. This makes it the
preferable solution for wiring that will
need to bend without experiencing
metal fatigue.
• The increased surface area of multi
stranded conductors decreases the
amount of resistance that currents or
signal passing through the wire will
encounter.

22. ACSR
• Aluminium conductor steel reinforced
• ACSR is a type of high capacity, high
strength stranded conductor typically used in
overhead power lines.
• The outer strands are high purity aluminium,
chosen for its good conductivity, low weight
and low cost.
• The center strand is steel for additional
strength to help support the weight of the
conductor.

23. AAAC
• All aluminium alloy conductors
• Concentric lay stranded aluminium alloy
conductors(AAAC) are made out of high
strength aluminium-magnesium-silicon alloy.
• These conductors are designed to get better
strength to weight ration and offer improved
electrical properties, when compared with
ACSR

24. Types of Cables
According to the type of insulation, cables are classified
as:
• VIR insulated cable
• CTS/TRS cable
• PVC cables
• Lead Sheathed cables

25. V I R cables (Vulcanized Indian Rubber)
• It consists of a copper conductor
covered with a insulation layer of
vulcanized Indian rubber (VIR).
• A cotton tape covering is provided
over this insulation layer to protect the
wire from moisture and to provide
mechanical strength to the wire.
• Used for low or medium voltage
• Used for indoor wiring

26. CTS/TRS Wires
• Cab type sheathed (CTS) or TRS
(Tough Rubber Sheathed) wires
consists of vulcanized rubber
insulated conductor.
• This insulation layer is covered by a
layer made of tough rubber (or)
tough rubber sheathed covering.
• This covering is very hard and
protects the wire from moisture and
provides mechanical strength.
• Used for some outdoor application
250-440V

27. PVC cables (Polyvinyl Chloride)
• These wires consists of a conductor over which
an insulation layer made up of polyvinyl
chloride is provided
• These wires cannot resist much heat and they
have relatively low melting points, so they aren’t
used in hot places and also these wires are not
used with heating appliances.
• PVC wires are available in almost all colours.
• These are available in 250/440V grades

28. Lead Sheathed cables
• These wires consists of vulcanized
Indian rubber insulated conductor
over which Lead sheath is provided
which gives mechanical strength to
wire & also protects from moisture.
• As lead is conductor of electricity,
the lead covering is provided with
earth wire.
• These are available in 240/415V
grade

29. Earthing
• The process of transferring the immediate
discharge of the electrical charges directly to
the earth by the help of low resistance wire is
known as the electrical earthing.
• Thus earthing protects the operating
personnel and some times the system and
equipment from damage.

30. Effects of shock
• Let go current:- the
maximum value of electric
current through the body of
a person at which that
person can release himself or
herself. This ranges between
10-20 mA.
• Under dry conditions, the
resistance offered by the
human body may be as high
as 100,000 ohms. Wet or
broken, skin may drop the
body’s resistance to 1000
ohms.

31. Types of electrical earthing
On the basis of type of installation earthing can
be classified into following types
• Plate earthing
• Pipe earthing
• Rod earthing
• Strip earthing

32. Calculation of Energy Consumption
• Device Wattage (watts) x Hours Used Per Day
= Watt-hours (Wh) per Day
• Device Usage (Wh) / 1000 (Wh/kWh) =
Device Usage in kWh
• Daily Usage (kWh) x 30 (Days) =
Approximate Monthly Usage (kWh/Month)
• Monthly Usage (kWh) x Electric Rate
(Rs./kWh) = Approximate Cost per Month
• A 125-watt television used three hours per day
125 watts x 3 hours = 375 Wh/Day
• A television using 375 Wh of electricity per
day
375 / 100 = 0.375 kWh
• A television using 0.375 kWh of electricity per
day
0.375 kWh x 30 Days = 11.25 kWh/Month
• A television using 11.25 kWh/Month with an
electric rate of Rs. 2.60/kWh
11.25 kWh x Rs. 2.60 = Rs.29.25/Month

33. Methods for Power Factor Improvement
• Static Capacitor
• Synchronous Condenser
• Phase Advancer

34. Static Capacitor
• Inductive load are taking lagging current which decreases the system
power factor.
• Capacitors provide leading current which neutralize the lagging inductive
component of load current.

35. Static Capacitor
• Advantages:
– Losses are low in static capacitors
– Low maintenance
– Do not require a foundation for installation
– Light weight so easy to install
• Disadvantages:
– Age of capacitor bank is less (8-10 years)
– If the rated voltage increases then it causes damage
– Once capacitor spoiled then repairing is costly

36. Synchronous Condenser
• When a synchronous motor operates at No-load and over excited then its
called a synchronous condenser.
• It provides leading current like a capacitor by over exciting the
synchronous motor
• It draws leading current and eliminates the reactive component when
synchronous condenser connected in parallel to the supply.
• These are used to improve the power factor in large industries.

37. Synchronous Condenser
• Advantages:
– Long life (almost 25 years)
– High reliability
– Requires low maintenance
– Faults can be removed easily
• Disadvantages:
• Produces noise
• It is expensive

38. Phase advancer
• It is a simple ac exciter.
• It is used to improve the power factor of induction motor in
industries.
• Advantage:
- The phase advancer can be easily used.
• Disadvantage:
– It is not economical for motors below 200HP.
Supply
Motor
Phase
Advancer

39. Phase advancer
• Advantage:
- The phase advancer can be easily used.
• Disadvantage:
– It is not economical for motors below 200HP.

40. Types of Batteries
Cells/Battery
Primary Cell
Secondary Cell
Battery is a collection of one or more cells. Which converts
chemical energy into electrical energy.
There are 3 main components: - Anode, + Cathode & Electrolyte

41. Primary Cells
• These batteries cannot be recharged once depleted.
• These are made up of electrochemical cells.
• These batteries have specific energy.
Applications:
•Wrist watches
•Remote controls
•children toys
•Portable entertainment devices
•Flashlights etc.

42. Secondary Cells
• These are rechargeable batteries.
Applications:
• Mobile phones
• Power portable electronic devices
• Some gadgets
• Electric vehicles
Types:
•Nickel Cadmium(Ni-Cd)
•Nickel-Metal Hydride(Ni-MH)
•Lithium-ion(Li-ion)
•Lead-Acid

43. Secondary Cells
1.Nickel Cadmium(Ni-Cd)
•Ni-Cd batteries are good at maintaining voltage and holding
charge when not in use.
• Material is nickel oxide hydroxide and metallic cadmium as
electrodes.
• these batteries offer good life cycle and good performance at
low temperature.
•Nominal Cell voltage is 1.2V
Applications:
•The small packs are used in portable devices, electronics and toys
•The bigger ones find in aircraft starting batteries, Electric vehicles and standby power supply

44. 2. Nickel-Metal Hydride Batteries
Secondary Cells
•The chemical reaction at the positive electrode of batteries is
similar to that of the nickel–cadmium cell (NiCd).
•The negative electrodes in Nickel-Metal Hydride use a
hydrogen-absorbing alloy instead of cadmium which is used in
NiCd batteries.
•Nominal Cell voltage is 2V.
Applications:
•Used in high drain devices because of their high capacity and energy density.

45. Secondary Cells
3. Lithium-ion Batteries
•Lithium ion batteries are one of the most popular types of rechargeable batteries.
• Lithium-ion batteries are a type of rechargeable battery in which lithium ions from the
negative electrode migrate to the positive electrode during discharge and migrate back to
the negative electrode when the battery is being charged.
• Nominal cell voltage is 3.6-3.85V.
Applications:
•Mobile phones
•Smart devices
•Aerospace
•Military applications due to light weight in nature.

46. Secondary Cells
4. Lead-Acid Batteries
•Lead acid batteries are a low-cost reliable power workhorse used in heavy duty
applications.
•They are usually very large and because of their weight.
•Lead acid batteries have very low energy to volume and energy to weight ratios but it has
a relatively large power to weight ratio.
•These are low in cost and attractive for use in several high current applications.
•Nominal cell voltage is 2V.
Applications:
•Solar-panel energy storage
•Vehicle ignition and lights
•High current application like powering automobile starter motors
•Backup power and load levelling in power generation/distribution.

47. Factors for selecting the battery
• Factors for selecting the battery
• 1. Energy Density: The energy density is the total amount of energy that can be stored per unit
mass or volume. This determines how long your device stays on before it needs a recharge.
• 2. Power Density: Maximum rate of energy discharge per unit mass or volume.
• Low power: laptop, i-pod.
• High power: power tools.
• 3. Safety: At high temperatures, certain battery components will breakdown and can undergo
exothermic reactions. High temperatures generally reduce the performance of most batteries.
• 4. Life cycle durability: The stability of energy density and power density of a battery with repeated
cycling (charging and discharging) is needed for the long battery life required by most applications.
• 5. Cost: It is important that the cost of your battery choice is commensurate with its performance
and will not increase the overall cost of the project abnormally.

48. Battery Backup
• It is also called as Uninterruptible power supply (or) online UPS (or)
Standby UPS.
• Applications:
– Data Centers
– Industries
– Hospitals
– Banks
– Telecommunications

49. Thank you

51. Example-1
• A house has the following loads:-
a) 8 lamps-60W each working for 6 hours a day
b) 5 fans-80W each working for 8 hours a day
c) 3 electric heaters-1000W each working for 2 hours a day
d) 1 electric motor 1.5hp working for 4 hours a day
Calculate the electricity bill if rate/unit is Rs.1.5/- and
Rs.15/- as meter rent for the month of September.

52. Example-2
• A workshop is connected with:-
a) 10 fans of 60W each working for 10 hours a day
b) 2 heaters of 1KW each working for 6 hours a day
c) 1 oven of 1.5KW each working for 12 hours a day
d) 15 electric bulbs of 60W each working for 4 hours a day
Calculate the electricity bill for the month of 30 days @ 55
paisa/unit.

53. Example-3
• A house has the following loads:-
a) 10 lamps of 60W each working for 10 hours a day
b) 1 oven of 450W working for 1 hour a day
c) 8 fans of 80W each working for 2 hours a day
d) 1 heater of 1000W working for 1 hour a day
e) 1 refrigerator of 250W working for 12 hours a day
Calculate the monthly electricity bill if rate of charge/unit if
Rs.1.20/- plus Rs.20/- as meter rent for the month of June.