Presentation PT.pptx

Distribution of
Transmission Line

Group Members
NAMES REGISTRATION NUMBERS
SAAD MALIK
Names Registration Numbers
Saad Malik FA19-EPE-075
Nangyal khan FA19-EPE-088
M. Yar Khan FA19-EPE-084
M Zeyad FA19-EPE-085
Kashif Zaman FA19-EPE-052

Introduction
1. Transmission Lines
 Transmission lines are a high voltage line that carries electricity from power plant to the
substation from it is further distributed to various areas for different purposes..
 The combined transmission and distribution network is known as the "National
Grid".
Distribution Lines
Distribution lines are low voltage lines that carry electricity from the substations to the end
users for residential and commercial use.

Basic Concept of Energy Transmission

Background of Electricity in Pakistan:
 At the time of independence in 1947 Pakistan had installed power
generating capacity of 60MW. In 1959 when Water and Power
Development Authority (WAPDA) was established, power
generating capacity was increased to 119MW.
 Pakistan’s power sector at that time was managed by two
integrated public sector WAPDA and KESC.

Water and Power Development Authority
(WAPDA)-1959
 Water and Power Development Authority (WAPDA) had Massive agenda was generation,
transmission and distribution of power along with irrigation, drainage and flood control etc.
The Electricity customer in the Pakistan is over 13 million Customer.
 There are Four Major Producers in Pakistan
 WAPDA (Water and Power Development Authority)
 KESCO (Karachi Electric Supply Company)
 IPPs (Independent Power Producers)
 PEACE (Pakistan Atomic Energy commission)

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

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 11kV. Due to
economic consideration, the
generation voltage (ie: 11kV) is
step up to 220kV or 132kV at the
power station with the help of step
up transformers.

2. Primary
Transmission
► 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. This is supplied to
substations usually at the out skirts of
major distribution centre or city.

3. Secondary
Transmission
 On the outskirt of the city, there
are sub station which step down
the primary transmission voltage to
66kV or 33kV and power is
transmitted at this voltage. This
forms the secondary transmission
system. 3 phase wire system is
used.

4. Primary Distribution
► The transmission lines or inner
connectors terminate at large main
substations from which the power is
distributed to small secondary
substations scattered throughout the
load area. The voltage may range from
11 kV to 132 kV.

5. Secondary
Distribution
 This consists of the low voltage
network laid along the streets,
localities and over the rural areas.
From these sources connections to
individual customers are provided.
The circuit used for this purpose is
3 phase 4 wire, 440 V/220 V from
which either 3 phase 440 V or
single phase 220 V supply to the
consumers may be provided.

Classification
of
Transmission
Lines
 The classification of the transmission lines depends on its
voltage and the length of the conductor. The transmission
line is the medium of transferring the power from the
generating station to the load center. It is mainly classified
into two types.
 AC Transmission Line
 Short-Transmission Line
 Medium Transmission Line
 Pi Model of a Medium Transmission Line
 T Model of a Medium Transmission Line
 Long Transmission Line
 DC Transmission Line

Difference
Between
Transmission
and
Distribution
Line
1. TRANSMISSION LINE
I. It is carried out electricity in three phase supply system.
II. Carries electricity at a very high voltage. About 11000 volts
III. They conduct current at 69 kV or more.
A. Distribution Lines
I. It requires a single phase supply system for carrying
electricity.
II. Carries electricity at a very low and safe level of about 220
volts.
III. They conduct less than 69 kV

Difference
Between AC
& DC
Transmission
Line
1. AC Transmission Line
I. The ac transmission line transmit the alternating current
II. Number of Conductor is three
III. Voltage Drop is High
1. DC Transmission Line
I. The dc transmission line is used for transmitting the direct
current
II. Number of Conductor is two
III. Voltage Drop is Low

Advantages &
Disadvantages
of DC and AC
Transmission
System
1. Advantages of DC Transmission System
2. Potential stresses developed on the insulation in the dc system
are 70% as compared to the ac system. Hence, it requires less
insulation
3. Construction of dc lines is easy as compared to ac lines.
4. The effect of the corona is reduced by using earth as a negative
conductor and the lines as a positive conductor.

Disadvantages
of DC
Transmission
System
It is difficult to step up and step down the
voltage in dc transmission.
It is difficult to step up and step down the
voltage in dc transmission.
Electrical power cannot be generated at high
voltage because of commutation problems.

Advantages
of AC
Transmission
System :
It is easy to generate electricity at high voltages (3.3
kV, 6.6 kV, and 11 kV) easily.
The voltage generated can be easily stepped up by
using a step-up transformer and also it can be
stepped down by using a step-down transformer.
The cost of the ac switchgear is less.

Disadvantages
of AC
Transmission
System
Due to the presence of skin effect the line resistance
will increase.
The amount of conductor material required is more as
compared to dc transmission lines.
To avoid the corona effect, the spacing between line
conductors should be kept more, which further
increases the cost of towers

High Tension &
Low Tension Line
 Tension is a French word which means Voltage
1. Low Tension Line
 Line voltage upto 1000V
I. LT Supply having two category
 (1) Single Phase (230v)
 (2) Three Phase (440/415)
(2) High Tension Line
 (11kv,22kv,33kv)

Electric Poles
 Electrical Pole is the structure or column used to support the overhead transmission line.
 The Distance Between two electric pole is called Span.
 Span between L T Poles = 30 – 45 meter
 Span between 11KV Line =45 – 65 meter
 Span between 33KV Line =80 – 100 meter
 Span between 132KV Tower = 250 _ 300 meter
 Span between 400KV Tower = 425 – 475 meter

Identification the KV
of Transmission Line
 For the 11KV transmission line,
generally Double Pole(DP)
structure is used.
if in a transmission line only one
disc insulator per phase is
connected then the transmission
line carrying 11KV

 In a transmission line, if three pieces
of disc insulators per phase are
connected, then the KV of the
transmission line is 33KV

Continuing
 If in a transmission line, five or six pieces
of disc insulators per phase are
connected then the transmission line
carrying 66KV.

 If in a transmission line, nine or ten
pieces of disc insulators per phase
are connected then the transmission
line carrying 132KV. Generally, nine
are used for suspension type and ten
are used for strain type

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