The document discusses electrical power distribution systems. It describes how power is generated at high voltages, stepped up further for transmission over long distances via transmission lines, then stepped down via substations for distribution to consumers. Key components of the distribution system include feeders that distribute power from substations, distributors that feed consumers, and service mains that connect distributors to meters. Distribution can be overhead, underground, radial, ring-based, or interconnected. Substations transform voltages and may be transmission, distribution, or switching types.

1. Electrical Power Distribution
and Utilization.

2. Power System
The generation, transmission and distribution of electric power is
called Power System.
A power system has the following stages:
-Generation of electric power
-Transmission of electric power.
-Distribution of electric power.
 Most transmission lines are high-voltage three-phase alternating
current (AC).
 High-voltage direct-current (HVDC) technology is used for greater
efficiency over very long distances (typically hundreds of miles).
 Electricity is transmitted at high voltages (115 kV or above) to reduce the
energy loss which occurs in long-distance transmission.
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4. Layout of Power System
A power system is consist of the
following stages:
1. Power Station
2. Primary Transmission
3. Secondary Transmission
4. Primary Distribution
5. Secondary Distribution
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5. 1.Power Station
The bulk power is generated
at the power station by 3-
phase, 3 wire system
employing several alternators
in parallel. The usual
generation voltage is 6.6, 11,
13.2 .or 33 kV.
Due to economic
consideration , the generation
voltage is 11kV.
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6. 2.Primary Transmission
In this step 11kV is
step up to High
voltages of the order
of 66 kV,132 kV,220
kV and 400 kV are
used for transmitting
power by 3 phase 3
wire overhead system.
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7. 3. Secondary Transmission
In this Step, after step down
the primary transmission
voltage to 132kV or 66kV the
power is transmitted at
Receiving Station and then
sent to step down
Transformer.
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8. 4.Primary Distribution
Step Down Transformer
further step down the
voltage up to 11kV and
sent to next sub station and
then to Distribution Sub
Station (Distribution
Transformer).This is called
Primary Distribution.
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9. 5.Secondary Distribution
By converting 11
kV to 400V or
220V and sent
to this power
to consumer
this step is
known as
Secondary
Distribution
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10. DISTRIBUTION
SYSTEM

11. DISTRIBUTION SYSTEM
The arrangement of conveying electric power from
bulk power sources (generating stations or major
substations) to the various consumers is called
distribution system.
Distribution is of two types. –
1.High voltage or primary distribution
2.Low voltage or secondary distribution
High voltage distribution is carried out at voltages of
the order of 33kv,66kv or,11kv.
Low voltage distribution which is carried out at
400/220 volts (in three phase 4 wires system)

12. Important terms of distribution system
1. Feeder
2. Distributor
3. Service mains
1.Feeder-
•A Feeder is conductor which connects the substation to the area where power is to
be distributed .
•
•Feeder are used to feed the electrical power from the generating station to the
substation
•
•No tapings are taken from the feeder
•
•So the current in it remains the same throughout
•
•Main consideration in the design of feeder is the Current carrying capacity.

14. 2.Distributer
A distributer is a conductor from which tapings are
taken from pole mounted transformer to the
consumer
•The current through a distributer is not constant
because tapings are taken at various places along its
length
•Voltage drop is main consideration
•Limit of variation is 6% of rated at consumer

15. 3.Service mains
A service mains is a generally a small cable which connects the distributer
to the consumer ‘s meter.
The connecting links between the distributor and the consumer terminals.
.

17. CLASSIFICATION OF DISTRIBUTION SYSTEMS
1. According to Nature of Construction :
a. Overhead distribution system
b. Underground distribution system
•overhead system is cheaper than underground
system.
•However, underground system is used in thickly
populated areas where overhead system may not be
practicable

18. 2. According to nature of current :
a.D.C distribution system
b.A.C distribution system
A.C distribution is universally adopted due to many advantage
of a.c. power over d.c. power.

19. Advantages of ac over dc:
•we got this supply by transmitting ac over long distances.
•AC can be transmitted using step up transformers but direct
current or dc can not be transmitted by this method.
•The ac is easy to generate than dc.
•It is cheaper to generate ac than dc.
•The ac generators have higher efficiency than dc.
•The ac can be easily converted into dc.
•The variation of ac can easily be done using transformers either
step up or step down.

20. Advantages of dc over ac :
•DC needs only two wires of transmission, while a 3 phase AC may need
up to 4 wires.
•The Corona loss associated with DC is negligible, while for AC, it
increases with its frequency.
•The skin effect is also observed in AC, leading to problems in
transmission conductor designs.
•No inductive and capacitive losses.
•No proximity effect.
•In fact, High Voltage transmission over 650 km long is often done with
DC.

21. 3. According to number of
wires :
a.2-wire d.c. system
b.3-wire d.c. system
c.Single phase, 2-wire a.c.
system
d.3-phase, 3-wire a.c. system
e.3-phase, 4—wire a.c. system

22. 4. According to the system of connection:
(a) Radial system
(b) Ring main system
(c) Interconnected system
Radial System: when the distributor is fed at one end
only, it is called radial distribution system. A single line diagram of
radial system is shown in fig.

24. Advantages of radial system:
1. its initial cost is minimum.
2.this system is employed when electrical energy is
generated at low voltage and power station is situated
at the center of load.
Disadvantages:
1.the end of the distributor nearest to the supply end
would be heavily loaded.
2.the consumers at the distant end of the distributor
would be subjected to serious voltage variations.
When the load on the distributor changes.

25. Ring main system:
In this system the only one Power Substation and there may be
two or three feeders which are connected to the ring of
distributors. Which further connected to controller switches
A,B,C and D.
Advantages of ring main system:
1.it offers a great reliability of supply. In the event of fault on
any system(Transformer) of feeder, the continuity of supply
can be maintained.
2. There may be two or three feeders but Power Substation is
only one.

27. Inetrconnected system:
In an “interconnected system” the feeder ring is energised by two or
more than two generating stations or substations fig. shows the single
line diagram of an interconnected system. The closed feeder ring
ABCDA is supplied by four stations S1, S2, S3 & S4 at
points D,A, B & C.

29. Introduction of Substations
A substation is a part of an electrical generation,
transmission, and distribution system. Substations
transform voltage from high to low, or the reverse,
or perform any of several other important
functions.

30. 21

31. Types of Substations
1. Transmission substation
•A substation where two or more transmission lines which are
come from Generation Station are connected is called
Transmission substation.
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32. 2. Distribution substation
A Substation that receive power from Transmission Substation or Power Station
and after step down the voltage, finally sent to the user is called Distribution
substation.
It is uneconomical to directly connect electricity consumers to the main
transmission network, unless they use large amounts of power, so the
distribution station reduces voltage to a level suitable for local distribution. I
The input for a distribution substation is typically at least two transmission or sub
transmission lines. Input voltage may be, for example, 115 W, or whatever is
common in the area. The output is a number of feeders.
Distribution voltages are typically medium voltage, between 2.4 kV and 33 kV
depending on the size of the area served and the practices of the local utility.
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34. 3. Switching substation
•A switching station is
a substation without transformers
and operating only at a single
voltage level
•Sometimes they are used
for switching or for parallelizing
circuits in case of failure.
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36. Components of Substations
Various components are used at grid transmission substations.
These are as follows:
1. Conductors
2. Current transformers
3. Potential Transformers
4. Lighting Arresters
5. The isolator
6. Bus Bar
7. Circuit Breaker
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37. Conductors
 Metals which do not allow the free movement of electrons or electric
charge. They resist electricity with their high resisting property.
Insulators
 It allows the flow of electric charge. It permits the free movement of the
flow of electrons through them.

38. Conductor
Insulator

39. A current transformer (CT) is a type
of transformer that is used to reduce or
multiply an alternating current (AC).
It produces a current in its secondary which is
proportional to the current in its primary
Current transformers

40. Potential transformer
Transformer used for the
transformation of voltage
from a higher value to the
lower value.

41. Lightning Arrester
A lightning arrester (lightning diverter)
is a device used on electric
power systems
and telecommunication systems to
protect the insulation and conductors
of the system from the damaging
effects of lightning.

43. The isolator
•The isolator is a mechanical switch which isolates a part of the
circuit from the system as when required.
•Its main purpose is to isolate one portion of the circuit from the
other and is not intended to be opened while current is flowing in
the line

44. Bus Bar
Bus Bar is a metallic strips of copper ,
conductor or group of conductor which is
used for electrical power distribution as
junction or node. The Bus bars that makes
the electrical power distribution much easier ,
less expensive and more flexible. Bus
Bar manufactured by aluminum and copper.

46. Circuit Breakers
Circuit breakers are used to open and
close circuits.
They can be operated manually to perform
maintenance or will automatically trip if a
short circuit occurs.

48. Relays
 It is a set of many identical capacitors connected in series or parallel
within an enclosure and is used for power factor correction and basic
protection of the substation.
Capacitor bank
 These are used for disconnection of the circuits by manual or automatic
operation. It consists of coil which is excited or energized to break or
make a circuit connection.

49. Relays Capacitor Bank