MKEP1633
TRANSMISSION OF ELECTRICAL
ENERGY
CONTENTS
• Overhead transmission
-
-
• Underground transmission / cable
Overhead Transmission
• Introduction
• Transmission Planning
• Electric Requirement and Design
Introduction
Power Station
Substation
High
Voltage
Substation
Medium
Voltage
Transformer
Low
Voltage
System Loads
Transmission Lines
f
•
double circuit
•
y
°
O
0
HV Power Line Component
Conductors
non insulated conductor
✓
• Normally bare
• Stranded copper or steel-reinforced aluminium cable
aluminium conductor steel-reinforced
(ACSR)
-
-
Insulators
• Support and anchor conductors and insulate them
from ground
• Ceramic or glass
• Must withstand mechanical and electrical stress
Support Structures (towers etc.)
-
-
-
• Wooden poles / H-frames for lower voltages,
galvanized steel towers for higher voltages
⑧¥¥É
É°¥÷§
" i.ae
aluminium
conductor
zy.at/zgt
→
steel
reinforce ,
ACSR
Transmission Tower
1. Suspension insulator set
2. Phase conductor
3. ←
Spacer between two
conductors of the same
phase
4. Shield conductor
lightning protection
5. A set of three phase
conductors
6. Identification plate
7. Security feature against
unauthorised climber
-
gold
¥
design
Line Conductors
other example
A CAR
-
-
ACA
-
AA
C
AC
ACSR
Line Parameter
←
should be
consider
higher concentration
÷:*
concentration
.
Line Parameter
K
electric field
between
) )
C
two
conductor
;
ii.
1-
magnetic
-5L
"
field Souvrounding conductor
Bundled Conductors
2 conductors
-
I
3 conductors
4 conductors
Advantages
the bundle
of
effect
conductor
-
• The inductive reactance is lower.
• Voltage gradient is reduced.
• Critical level for corona is increased ,resulting into reduced power
loss caused by corona, noise, and also reduced
radio frequency
interference.
=
-
• More power per unit mass of the conductor can be transported by
the lines.
Disadvantages
• Increase of mechanical loading to the line due to wind or snow.
• The technique to suspend the conductors to transmission towers
becomes much more complicated due to the weight of the
additional conductors.
• The conductors are easily sway when blown by the wind.
• Increase of construction cost.
• Significant effect from reactive power charging.
Parallel Lines
TL
(1)
Short
Transmission
line
L 8ohm
④ )
medium
→
→
T
It
transmission line
type
type
between
80hm
TL
)
i
long
①
7 240km
to
240km
Line Representation - Short
• Length < 80 km
Us
-
Vsending
Is Isendirg
-_
I
Vpivreceiving
In -1 receiving
short
TL
q¥ÉÉ
.IE#-p..Vs--IsZtVp
↳
rewrite
Vs=VrtIsZ
Is
__
-
-
-
i]
In
:]
:X
1¥11
:
:*
:]
1%7--44=1
Medium Line (80 to 240) km
• Nominal - T
c-
ABCD
F-¥ÉÉÉE÷¥÷÷ÉÉ¥É÷p
i
"
-
Vs
=
Is
-
Is E
7- r
=
+
+
Fritz
=
medium
"
Io
YI 7¥
Vs
Vt
+
"
T
transmission
"
I
Vc ✗ Y
Ic :
I
Fitz
q
=
Ip
+
+
+
so
Vr
Vr
)Y 1M¥
=
Iit¥
Ctr +7m¥
+
+
KY
KY
+
)E
KY
+
7-
RE
+
Vr
Vs
7-
:
RE
In
+
2¥
+
KYE
+
7-
ritz
+
VR
rearrange
Us
Vitt
=
=
Vr
+
Vr
LEE 1)
+
+
+
IRE
+
Ir ( 2-
from
Is
Is
Is
=
Ir +
=
V RY
=
VRY
as
a
IRIE
tr
t
+
+
VRY
+7k¥
Ipl i +7¥ )
results
7-
+
RE
+
7-
Z¥ )
RZ¥
÷÷¥K:L
.
Medium Line (80 to 240) km
←
Long Line > 240 km
…………………
…………………
No. of line segments depend on accuracy required and available computational
resources
Long Line > 240 km
ii. By using distributed representation (telegraphic
equation
Line Performance
• Efficiency
=
• Voltage regulation
Transmission Planning
• Define a transmission system or its expansions
so as to comply with the electric energy
demand at specified quality and reliability
criteria at a minimum cost.
• Time horizon
- Long term
: 15 years and more
- Medium term : about 10 years
- Short term
: about 3 years
Classification of Planning
Long Term
(15 years)
Medium Term
(10 years)
Short Term
(Operation)
(3 years)
Problem to be
considered
Required power,
overloads,
stability
Required power,
overload stability,
voltage levels,
short circuit
Required power,
overload,
stability, voltage
levels, short
circuit
Parameter to be
defined
Capacity (ratings),
voltage levels,
terminal areas,
approximate
years
Capacity (ratings),
losses, operative
voltage, terminal
substations, years
of operation
List of operational
constraints,
needs to uprate
or upgrade lines,
anticipating of
programed
facilities
Model size
Area of supply
region
Interconnected
system
Utility system
Planning Aspects
• When a new transmission line or the uprating or
upgrading of existing lines will be required?
• Where it is required and what quality of supply or
reliability is required?
• What normal and emergency ratings are required?
• What type of transmission should be used?
Overhead lines or underground cables, DC or AC
lines?
• What voltage and how many circuits will be needed
Planning Methods/Steps
• Data acquisition and preparation
- Market forecast, generation capacity, existing network
and preferential characteristics
• Formulation and preselection of alternatives
• Electrical studies in planning and design
- Power flow requirements, system stability and dynamic
performance, selection of voltage level and optimization
studies, voltage and reactive power flow control,
conductor selection, losses, corona performance
(audible, radio and television noise), electromagnetic
field effects, reliability evaluation, insulation and
overvoltage design, switching arrangements, circuit
breaker duties, short circuit and protective relaying
• Economic studies and final evaluation
General consideration in the design
of a power line
•
•
•
•
The amount of active power it has to transmit
The distance over which the power must be carried
The cost of the power line
Aesthetic consideration, urban congestion, ease of
installation, expected load growth
Standard Voltages
Classification
Range
LV
< 1 kV
MV
1 kV – 100 kV
HV
> 100 kV
Standard
Levels
415 V (3phase)
240 V (1phase)
3.3 kV, 6.6 kV,
11 kV, 33 kV, 66
kV
132 kV, 275 kV,
400 kV, 750 kV
?⃝
Electric Requirements and Design
•
•
•
•
•
•
•
•
•
•
•
•
•
Surge impedance loading (Natural power)
Stability
Voltage regulation and maximum permissible losses
Capacity of a line
Reliability and availability
Reactive power compensation
Power transmitted versus right-of-way witdh
Ohmic losses
Short-circuit condition
Effect of electrical and magnetic fields
Corona phenomena
Line performance and insulation requirement
Clearances
not
include
in
final
exam
or
test
C. Baylissand B. Hardy, Transmission and Distribution Electrical Engineering,
Third Edition, 2007, Newnes, Burlington, USA
Thank You