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1. WELCOME TO MY
PRESENTATION
1

2. PRESENTATION ON :
Operation of 33/11 KV Substation at Comilla
Palli Bidyut Samity-1
Presented by
Kamal Ahmed
Department of Electrical and Electronics Engineering
ID # 12205003
IUBAT-International University of Business Agriculture
and Technology
2

3. CONTENTS
INTRODUCTION
OBJECTIVE
ORGANIZATIONAL OVERVIEW
SYSTEM CRITERIA OF CPBS-1
BASIC ELECTRICAL SYSTEM
DISTRIBUTION SYSTEM
SUBSTATION
TRANSFORMER
POWER TRANSFORMER
DISTRIBUTION TRANSFORMER
INSTRUMENTAL TRANSFORMER
3

4. CONT…..
ISOLATOR
INSULATOR
FUSE
CIRCUIT BREAKER
RELAY
LIGHTNING ARRESTER
BUS BAR
POWER FACTOR
VOLTAGE REGULATOR
RECOMMENDATION
CONCLUSION
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5. INTRODUCTION
Electricity is very essential for the development
of a nation. The dependence on electricity is so
much that it has become a part and parcel of our
life. The power sector in Bangladesh faced
numerous problems characterized by lack of
supply capacity, frequent power cuts,
unacceptable quality of power supply, and poor
financial & operational performance of the sector
entities. Lack of good governance along with
poor procurement management is considered to
be the root cause of these problems.
5

6. 6
OBJECTIVE
Theoretical knowledge.
Collecting Knowledge regarding Power
& Distribution system of CPBS-1.
Study about Substation.
Test and check the equipments of
Substation.
Identifying different types of problem
which arise for operating this
Substation.
Suggest probable solution of the
identified problem.

7. Organizational Overview
 Background - Comilla Palli Bidyut
Samity-1 is a part of REB started its
activities on 12-01-1981 in Dhaka.
 Vision- To provide quality and
uninterrupted electricity to vast majority of
Rural Bangladesh for their personal,
social and economic development
 Mission- Quality and uninterruptable power
supply.
 Goal- The goal is Comilla Palli Bidyut Samity-1
to reach the electricity in every home in 2020.
7

8. System Criteria of CPBS-1
 The average system will serve 30,000 to 75,000
consumers with an average of 750Km of distribution
line.
 The nominal sub-transmission voltages are 33,000
volts Nominal voltage for primary distribution is
11000 volts.
 The system frequency is 50HZ
 Medium voltage side solidly grounded 4 to 6 three
phase feeders will distribute power from the substation
for distance of some 10 to 12 km with single phase
branch or tap lines taking off from the three phase line
as required to serve single phase consumers.
8

9. Basic Electrical system
9

10. Distribution system
Electricity can be distributed by two ways.
Overhead distribution &
Underground distribution
10

11. Overhead distribution
11

12. Sub-Station
The assembly of apparatus used to change
some characteristics (e.g. Voltage AC to DC
frequency, Power factor, etc) of electric
supply is called sub-station.
12
Fig:33/11KV Sub-Station

13. Transformer
A transformer is an electrical device that
transfers energy from one circuit to another by
electromagnetic induction without any
moving parts. Transformers are used to
convert high voltage to low voltage or low
voltage to high voltage.
13

14. Basic Function of Transformer
Transformer is an electrical device that ..
• Transfer electric
power from one
circuit to another
• It does so
without a change
of frequency
• It accomplishes
this by
electromagnetic
induction
14

15. Common Types of
Transformer
 Generally used in transmission
network
 It’s rating is given in terms of the
secondary's maximum voltage and
current-delivering capacity
 Operates at high voltage greater
than 33 KV with 100% efficiency
 Has a big size
 Used in generating station,
transmission & distribution
substation at high insulation level.
15

16. Power Transformer 33/11KV
Specification of Three Phase
Power Transformer
 Transformer Type OUT DOOR
 Type of Cooling ONAN/ONAF
 Rated MVA 5/6.25
 Rated KV
HV 33
LV 11
 Rated Line Current
HV 87.5/109.3
LV 270.5/332.6
 No of Phase 3
 Standard Frequency 50Hz
16
Fig : 3-Phase Power Transformer

17. Common Types of
Transformer
• Used for the distribution of electrical
energy
• Operates at low voltage as less than
33KV in industrial purpose and 440v-
220v in domestic purpose
• It works at low efficiency at 50-70%
• Has small size easy in installation
• Has low magnetic losses & it is not
always fully loaded.
17
Figure : Distribution Transformer

18. Specification of Three Phase
Distribution Transformer
 Type of Cooling ONAN/ONAF
 Rated KVA 2500
 Phase 3
 Rated Voltage
HV 11 KV
LV 0.415KV
 Rated Current
HV 131.2A
LV 3478.01A
 Frequency 50Hz
18
Figure :3-Phase Distribution Transformer

19. Specification of Distribution
Transformer
 Type Wound Core
 Phase 1
 Rated Voltage
HV 6350V
LV 240V
 Rated Current
HV 11.81A
LV 312.5A
 Frequency 50H
 Total Weight 450Kg
19
Fig :1 Phase Distribution Transformer

20. Common Types of
Transformer
1. Current Transformer
(C.T)
 Current transformer is used
for stepping down AC current
from higher value to lower
value for
measurement/protection.
 Current transformer is two
types.
 Indoor type and
 Outdoor type.
20
Fig : Current Transformer

21. Type of Core
 Normally current transformer is provided with multi core.
Cores are divided into two categories:
 Protective
 Measuring.
 Protection core of current transformer is used for over
current protection, earth fault protection, differential
protection etc.
 Measuring core of current transformer is used to supply
current to measuring instruments like ammeters, watt-
meters, KVA meters, KWh meters etc.
21

22. Application of Current Transformer
 Direct measurement of current in high
voltage system is not possible because of
insulation problem of measuring
instruments.
 Its is also not possible to use current
flowing through the system directly for
protection purpose due to its high value
and high insulation problem.
22

23. Use of Current Transformer
 AC power supplies
of appliances.
 In ground fault circuit
interrupter.
 Circuit breakers.
 AC power supply
grids.
23
Fig : Sub Station

24. Common Types of
Transformer
2.Potential Transformer
 Potential transformers are
used to step-down highs
system voltage low
standard value accurately
in proportion to their ratio.
 Potential Transformer is
two types.
 Indoor type and
 Outdoor type.
24
Fig: PT

25. Application of Potential Transformer
 Direct measurement of voltage in high
voltage system is not possible because of
insulation problem of measuring
instruments.
 It is also not possible to use directly
voltage for the system protection purpose
due to its high value and high insulation
problem of protection relays.
25

26. Use of Potential Transformer
(PT)
 Potential transformers are used in the AC
power supplies of appliances,
 In ground fault circuit interrupter.
 Circuit breakers.
 AC power supply grids.
26

27. Isolator
Isolator is a disconnecting
switch, which operate
under no load condition. It
has no any specified
current breaking capacity
or current making
capacity.
27
Fig: Isolator

28. Insulator
The overhead line
conductors should be
supported on the poles or
towers. Insulators are those
substance which do not can
flow current from conductor
to earth supports. The most
commonly used material
for the manufacture of
insulator is porcelain.
28
Fig: Insulator

29. Insulator Types
In PBS system 5 types of insulator are
used.
Pin type insulator
Suspension type insulator
Strain insulator
Shackle insulator &
Stay insulator
29

30. Pin type insulator :
Pin type insulators are
used for transmission and
distribution of electric
power voltage up to 33KV
Suspension type
insulator:
For high voltage like as
33KV transmission line,
Suspension type
insulators used.
30
Fig: Pin type insulators
Fig:Suspension type
insulator

31. Strain insulator
Dead end of the line or the corner or the
sharp curve, the line is subjected to
greater tension
31
Fig: Strain
insulator

32. Shackle
insulator
It can be used either in
a horizontal position or
in a vertical position.
They can be directly
fixed to the pole with a
bolt or to the cross
arm.
For low voltage lines,
the stays are to be
insulated from ground
at a height not less
than 13 meters from
ground.
32
Stay insulator
Fig: Shackle insulator
Fig: Stay
insulator

33. FUSE
A fuse is a short pitch
of metal, inserted in the
circuit, which melts
when excessive current
flows thought it for
sufficient time. It is
inserted in series with
the circuit to be
protected.
Fig: Fuse
33

34. Circuit Breaker
34
A circuit breaker is an electrical
equipment which can open or close a
circuit under all conditions such as no
load, full load and fault conditions. It
can be operated manually under normal
conditions and automatically under fault
conditions.

35. Operation of circuit breaker
 Circuit breaker consist of fixed and moving contact
 Under normal condition these contact remain close .
 When fault occurs the secondary current of C.T will
increase and the trip coil get energized
 the moving contact is pulled apart by relay
mechanism, thus opening the circuit.
35
Figure : Mechanism of Circuit Breaker

36. PBS Used circuit breaker
In PBS system 2 types of circuit breaker are
used.
Automatic Circuit Recloser (ACR) &
Oil circuit Recloser (OCR)
36

37. Auto Circuit Recloser
ACR :
 Operated by control panel
 SF6 is being used for
insulation
 Vacuum interrupter is
being used for
extinguishing the arc
 Two coil is being used
closing coil and trip coil
37
Fig : ACR

38. Oil circuit Recloser
OCR :
 Operated manually by
fiber stick
 Transformer oil is being
used for insulation
 Oil interrupter is being
used for arc interruption
 Five coil of three types is
being used like series trip
coil (3),ground trip coil,
closing coil
 Ckt will trip at least
double of rated current
38
Fig : OCR

39. Relay
A protective relay is an automatic device that
detects the fault and initiates the operation of the
circuit breaker to isolate the defective element from
the rest of the system.
 The Relays detect the abnormal conditions in the
electrical circuits by constantly measuring the
electrical quantities which are different under
normal and fault conditions.
After detecting the abnormal conditions, it close
the trip circuit in order to disconnect the faulty
part from healthy part.
39

40. Operation of Relay
 Primary winding of C.T is
connected in series with
the line
 Secondary winding of C.T
is connected with relay
coil.
 Trip coil and relay coil is
connected with supply. If
fault occur, heavy Current
flow through the relay coil.
Causing the relay to
operate by closing its
contact.
40
Figure 31: Relay Operation

41. Lightning arrester
A lightning arrester is a
protective device which
conducts the high voltage
surges on the power
system to the ground.
A lightning arrester is
used on electrical power
system to protect the
insulation on the system
from the damaging effect
of lightning. Fig: Lighting arrester
41

42. Bus bar
When a number of lines operating at the same
voltage have to be directly connected
electrically.
Bus-bars are copper rods and operated at
constant voltage. The incoming and outgoing
lines in a substation are connected to the bus
bars.
42

43. Fig: Arrangement of bus bar
43

44. Main and Transfer bus
arrangement
44
CB
CB CB CB CB
CB
Transformer
CB
Main bus bar
Transfer bus bar CB
Bus
coupler

45. POWER FACTOR
The cosine of angle between voltage and current in
an AC circuit is known as power factor.
In AC circuits, the power factor is the ratio of
the real power that is used to do work in the
circuit and the apparent power that is supplied
to the circuit.
The power factor can get values in the range
from 0 to 1.
45

46. Importance of Power Factor
 Lower utility fees by :
 Reducing peak KW billing demand
 Eliminating the power factor penalty
 Increase the system capacity and reduce the
system losses in electrical system.
 Increase the voltage level in electrical system.
46

47. Methods of Power Factor
Improvement
Static capacitor.
Synchronous condenser &
Phase advancers.
47

48. Static Capacitor
 The power factor can be improved by
connecting capacitors in parallel with the
equipment operating at lagging power factor.
The capacitor draws a leading current and
partly or completely neutralizes the lagging
reactive component of load current. This
raises the power factor of the load. For
three-phase loads, the capacitors can be
connected in delta or star as shown in Figure
48
Fig: Capacitor connected in Delta or
Star

49. Figure: Capacitor Bank use for power factor improvement
49

50. Automatic Voltage Regulator
 A voltage regulator is an electrical
regulator designed to automatically
maintain a constant voltage level.
 Voltage regulators operate by
comparing the actual output voltage to
some internal fixed reference voltage.
Specification of Automatic Voltage Regulator
 Phase Number 1
 Type of Cooling ONAN
 Rated Power 416.5KVA
 Rated Voltage 6350 V
 Rated Current 656A
 Voltage Regulation ±10
 Frequency 50 Hz
50
Fig: Voltage Regulator

51. Single Line Diagram of Distribution Substation
51
Fig: Single Line Diagram

52. Rating of Distribution Substation
There are three Transformer T1, T2 & T3 Each
Transformer are same rating 10 MVA
Current: Primary Current - 175A
Secondary Current - 575A
Voltage: Primary Voltage - 33KV
Secondary Voltage - 11KV
This Substation Total Rating is 30 MVA.
52

53. Recommendation
 According to system design, the ratio of HT
line and LT line must be 70:30 in PBS
system.
 The load of rearrangement of substation
feeder must be done properly. But they do
not follow it.
 They use manually based equipment, if they
use PLC based equipment then the system
will be easier.
 Need to change wooden poles and cross
arms. 53

54. Conclusion
Electricity is the basic necessity for the economic
development of a country.
The industrial development and living standard
of the people are directly related to the more use
of electricity.
Without electricity it is impossible to
industrialize and irrigation as agro based country.
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55. 55

56. :
Thank You
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