Ppt power grid design

Department of Electrical Engg.SIET,Dhenkanal.

Synergy Institute of Engineering &
Technology,Dhenkanal
Seminar on
Power Grid Design
Submitted by
Susanta Das
7th Semester B.Tech
Reg.No-0901230234
Seminar Guide Mr. A. Panda
Department of Electrical
Engg.SIET,Dhenkanal. 2

Outline of Presentation
 Introduction
 Need of Power Grids
 Selection Site
 Layout Design
1.Busbar Schemes
2.Electrical Layout Drawing
3.Bill of Material
 Safety Clearance in Grid
 Design of Earth Mat
 Control Room
 Switch/Relay Room
 Grid Equipments
 Conclusion
 Reference

INTRODUCTION
 An electrical grid is an
interconnected network for
delivering electricity from
suppliers to consumers. It
consists of three main
components; 1) power
station that produce
electricity from combustible
fuels or non-combustible
fuels; 2) transmission
lines that carry electricity
from power plants to
demand centers; and
3) transformers that reduce
voltage so distribution lines
carry power for final
delivery.

WHY WE NEED GRID?
 Improvement of
Reliability
 Improvement of
economics
 Improvement of
efficiency
 Imrovement of power
quality
 Improvement of security
& safety
 Controller of entire power
system

SELECTION OF SITE
 Selection of site for construction of a Grid Sub Station is the first
and important activity. This needs meticulous planning, fore-sight,
skillful observation and handling so that the selected site is
technically, environmentally, economically and socially optimal
and is the best suited to the requirements
The site should be:-
 As near the load centre as possible.
 Easily accessible to the public road to facilitate transport of
material
 Above highest flood level (HFL) so that there is no water logging.
 Sufficiently away from areas where police and military rifle
practices are held.
 Free from master plans / layouts or future development activities
to have free line
 The should be far away from Airport

REQUIREMENT OF LAND / AREA:-
 The site should have sufficient area to properly accommodate
the Sub Station buildings, structures, equipments, etc. and
should have the sufficient area for future extension of the
buildings and / or switchyard.
 The requirement of land for construction of Sub Station including
staff colony is as under:
S.No. Voltage Class of GSS Required Area
1 400 20.0 Hectare
2 220 6.0 Hectare
3 132 3.5 Hectare

Layout Design-Bus bar Schemes
The commonly used
bus bar schemes at
Sub Stations are:
 Single bus bar.
 Main and Auxiliary
bus bar.
 Double bus bar.
 Double Main and
Auxiliary bus bar
 One and a half
breaker scheme.

Single bus bar:-
 This is the simplest switching scheme
in which each circuit is provided with
one circuit breaker.
 This arrangement offers little security
against bus bar faults .
 The entire Sub Station is lost in case
of a fault on the bus bar.
 In case of maintenance of circuit
breaker, the associated feeder has
also to be shutdown.
Main and Auxiliary bus
Bar:-
 This is technically a single bus bar
arrangement with an additional
bus bar called “Auxiliary bus”.
 As in the case of single bus
arrangement, due to the fault the
entire substation is lost.
 This bus arrangement has been
extensively used in 132 kV Sub
Stations.

Double Bus Bar
 In this scheme, a double bus bar
arrangement is provided. Each circuit
can be connected to either one of these
bus bars through respective bus bar
isolator.
 Bus coupler breaker is also provided so
that the circuits can be switched on from
one bus to the other on load.
 This scheme suffers from the
disadvantage that when any circuit
breaker is taken out for maintenance, the
associated feeder has to be shutdown
 This Bus bar arrangement was generally
used in earlier 220 kV sub stations.
DOUBLE MAIN AND
AUXILIARY BUS BAR
ARRANGEMENT
 The limitation of double bus bar
scheme can be overcome by using
additional Auxiliary bus,.
 The feeder is transferred to the
Auxiliary bus during maintenance of its
controlling circuit breaker without
affecting the other ckt.

One & A Half Breaker Arrangement
 In this scheme, three circuit breakers
are used for controlling two circuits
which are connected between two bus
bars. Normally, both the bus bars are
in service.
 A fault on any one of the bus bars is
cleared by opening of the associated
circuit breakers connected to the faulty
bus bar without affecting continuity of
supply. Similarly any circuit breaker
can be taken out for maintenance
without causing interruption.
 Load transfer is achieved through the
breakers and, therefore, the operation
is simple.
 The breaker and a half scheme is best
for those substations which handle
large quantities of power and where
the orientation of out going.
 This scheme has been used in the
400 kV substations.

Electrical Layout Drawing

List of Material The lists of material are only typical and cover the general requirement. Any
other
 equipment / structure / material which may be required for construction of
Sub Station as
 per layout and other requirements and not included in the above typical lists
of

Safety Clearance The various equipments and associated / required facilities have to be so arranged within the substation that
specified minimum clearances are always available from the point of view of the system reliability and safety
of operating personnel. These include the minimum clearances from live parts to earth, between live parts of
adjacent phases and sectional clearance between live parts of adjacent circuits / bays. It must be ensured
that sufficient clearance to ground is also available within the Sub Station so as to ensure safety of the
personnel moving about within the switchyard.
 As per Rule 64 (2) of the Indian Electricity Rules, 1956, the following safety working
 clearances shall be maintained for the bare conductors and live parts of any apparatus in any
 Sub Stations, excluding over head lines of HV and EHV installations:
Nominal
system
Voltage
in (kv)
Highes
t
Syste
m
Voltag
e in(kv)
Lightin
g
impulse
Level(K
Vp)
Switching
Implulse
Voltage in
(KVp)
Minm
Clearance
Betn Phase
&Earth(mm)
Minm
clearanc
e Betn
Phases
(in mm)
Safety
Clearan
ce(mm)
Grou
nd
Clear
ance(
mm)
11 12 70 ---- 178 229 2600 3700
33 36 170 ---- 320 320 2800 3700
132 145 550
650
---- 1100
1300
1100
1300
3700
3800
4600
4600
220 245 950
1050
---- 1900
2100
1900
2100
4300
4600
5500
5500
400 420 1425 1050(Ph-
E)
3400
----
----
4200
6400 8000

Earth Mat Design
 Provision of adequate earthing system
in a Sub Station is extremely important
for the safety of the operating
personnel as well as for proper system
operation and performance of the
protective devices.
 The primary requirements of a good
earthing system in a Sub Station are
a):-The impedance to ground should
be as low as possible but it should not
exceed 1.0 (ONE) Ohm.
b):- The Step Potential, which is the
maximum value of the potential
difference possible of being shunted by
a human body between two accessible
points on the ground separated by the
distance of one pace (which may be
assumed to be one metre), should be
within safe limits.
c):- Touch Potential, which is the
maximum value of potential difference
between a point on the ground and a
point on an object likely to carry fault
current such that the points can be
touched by a person, should also be
within safe limits.

Cont.
The details of the earthing material generally used in a
sub station are given below:

Design of Control Room
 The control room is the
main command centre of
the substation. The entire
operation of the site is
monitored and controlled
from this central location.
 A control room may range
from a small, seldom
manned, non-ventilated
room to a large, air
conditioned area containing
numerous staff members
and electronic equipment
(PCs, control
panels/consoles, electrical
and electronic switching
devices, under floor
cabling, etc.).

Design of battery Room
 The Battery Room houses lead acid or
nickel cadmium batteries for uninterrupted
power supply (UPS) to the substation.
 In power grid normally 110 no. of batteries
are present, having each capacity of 2.1V
to maintain 220V output & the specific
gravity of liquid is 1.835.
 Power House FCBC are designed to
supply continuous power to the DC load
and simultaneously charge the batteries
connected. Input supply form 415V. AC 3
Phase or 220V. AC 1 Ph. is converted to
regulated DC. The charger has two
independent systems.
 Normally the DC Power is supplied to he
load by the Float Charger. It also supplies
trickle current to the battery to keep it
healthy. If the charging current under Float
Mode exceeds a set level.Boost charger is
switched ON. It supplies Quick charging
current to the battery. On battery reaching
the set value the Boost Charger is switched
OFF.

Design of Switch/Relay Room
 The Switch Room
accommodates high density of
electronic equipment housed
in cabinets and automated
switch-gear. In-cabinet
equipment maintain the
primary functions of the facility
and form the switching
interface between the Control
Room and the field
equipment. The area may also
accommodate a significant
amount of metering and
logging equipment. Due to the
high volume of critical
electronic equipment, it is
essential that a fire event be
detected before the operation
of the plant is compromised.Department of Electrical Engg.SIET,Dhenkanal.

Grid Equipments
Lighting Arrestor
 It is an instrument that protect
vital equipments in the grid
 when a lightning strikes a
power transmission line, the
induced high voltage travels
along the line towards both
ends; this arrester will bypass
this high voltage to the ground
so that the nearby transformer
will not be damaged.
Line Volt.(KV) L.A.Rating(KV)
400 327
220 180
132 108
33 27

CVT:-
 It is that type tfr which is used to
measure potential
 It is the major advantage of PT, &
also used for carrier
communication, which replace the
coupling capacitor.
 At first for carrier communication a
coupling capacitor is used with a
PT, which is costlier than CVT.
 It act as a high pass filter.
Connection diagram of CVT

Potential
transformer:-
 Potential Transformer or Voltage
Transformer are used in electrical
power system for stepping down
the system voltage to a safe value
which can be fed to low ratings
meters and relays. Commercially
available relays and meters used
for protection and metering, are
designed for low voltage.

Current Transformer:-
 A current transformer is
used in high voltage
circuits where it is not
possible to measure
current directly.
 A CT is a step up
transformer with only one
turn in primary. There will
be as many cores based
on the purposes like
metering, protection etc.
 The secondary of a CT
should never be kept open
circuited because very high
flux will be developed in the
secondary and hence it
may be damaged.

Power TRANSFORMER
 It is a static device which
transforms electrical energy from
one ckt to another ckt without
change of frequency, but changing
voltage with the principle mutual
induction.
 Most of the power transformer are
in MVA ratings.
 It is the most costlier equipments
in the grid.

 INSULATOR:-
 Insulators are used to prevent
flow of current from
conducting material to non
conducting material.
 It should be mechanically
strong & high dielectric
strength.
 Each insulator rating is of
11kv to 16kv.
Wave Trap:-
It is the combination of inductance &
capacitance, which act as a low pass filter,
which passes low frequencies in to the
grid, & this frequency is used in the grid.
The Line trap offers high impedance to
the high frequency communication signals
thus obstructs the flow of these signals in
to the substation bus bars. If there were
not to be there, then signal loss is more
and communication will be
ineffective/probably impossible.

Circuit breaker:-
 It is protective equipments in the
grid.
 It is the automatic on load switch.
 There are of 5 medium type of
circuit breaker., but SF6 ckt
breaker is used for best.
Isolators:-
 This is an off load switching
device to used open or close for
flow of current or not to flow
respectively in the grid.

Conclusion:-
 Grid is the nodal point of the
entire power system.
 It has two objectives i.e.1: Supply
Quality Power, 2:Supply the power
from source to load with an
economic reasons.
 AS Grids are interconnected so,
there is an improvement of
reliability of can achieved.
 As grid is the nodal point, if it fails
to work, then entire power system
will fails.
 Grid efficiency is lower i.e. 50-
70%.
 As Grid has too many equipments
so, design of grid is too costlier.

Reference:-
 Construction Manual for substations by Shreemat Pandey Chairman &
Managing Director Jaipur Rajasthan Rajya Vidyut Prasaran Nigam Ltd.
 Albert, R., Albert, I., and Nakarado, G. L. (2004). Structural Vulnerability of
the North American Power Grid. Physical Review E 69 025103(R). 1-4 pgs.
 Grid Manual of OPTCL.
 http://www.powergridindia.com

Ppt power grid design

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