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Department of Electrical Engg.SIET,Dhenkanal.


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Synergy Institute of Engineering &

Technology,Dhenkanal

Seminar on

Power Grid Design

Submitted by

Susanta Das7th Semester B.Tech

Reg.No-0901230234

Seminar Guide Mr. A. Panda

Department of Electrical

Engg.SIET,Dhenkanal.2


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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



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INTRODU TION An electrical grid is an

interconnected network fordelivering electricity fromsuppliers to consumers. Itconsists of three maincomponents; 1) powerstation that produceelectricity from combustiblefuels or non-combustiblefuels; 2) transmissionlines that carry electricity

from power plants todemand centers; and3) transformers that reducevoltage so distribution linescarry power for finaldelivery.



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WHY WE NEED GRID? Improvement of

Reliability

Improvement of

economics

Improvement ofefficiency

Imrovement of power

quality

Improvement ofsecurity

& safety Controller of entire power

system



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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



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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



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Layout Design-Bus bar Schemes

The commonly usedbus bar schemes atSub Stations are:

Single bus bar.

Main and Auxiliarybus bar.

Double bus bar.

Double Main and

Auxiliary bus barOne and a half

breaker scheme.



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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 busBar:- This is technically a single bus bar

arrangement with an additionalbus 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 SubStations.

De artment of Electrical En .SIET Dhenkanal.


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One A Half Breaker Arrangement In this scheme, three circuit breakers

are used for controlling two circuits

which are connected between two busbars. 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.



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Electrical Layout Drawing



13/33Department of Electrical Engg.SIET,Dhenkanal.


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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



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S f Cl


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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

Voltage 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


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Earth Mat Design Provision of adequate earthing system

in a Sub Station is extremely importantfor the safety of the operatingpersonnel as well as for proper systemoperation and performance of the

protective devices. The primary requirements of a good

earthing system in a Sub Station are

a):-The impedance to ground shouldbe as low as possible but it should notexceed 1.0 (ONE) Ohm.

b):- The Step Potential, which is themaximum value of the potential

difference possible of being shunted bya human body between two accessiblepoints on the ground separated by thedistance of one pace (which may beassumed to be one metre), should bewithin safe limits.

c):- Touch Potential, which is themaximum value of potential differencebetween a point on the ground and a

point on an object likely to carry faultcurrent such that the points can betouched by a person, should also bewithin safe limits.



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Cont.The details of the earthing material generally used in a

sub station are given below:


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Design of Control Room The control room is the

main command centre ofthe substation. The entireoperation of the site ismonitored and controlledfrom this central location.

A control room may rangefrom a small, seldommanned, non-ventilatedroom to a large, airconditioned area containingnumerous staff membersand electronic equipment(PCs, control

panels/consoles, electricaland electronic switchingdevices, under floorcabling, etc.).



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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 3Phase 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 ithealthy. 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.



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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 significantamount 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 operationof the plant is compromised.Department of Electrical Engg.SIET,Dhenkanal.

G E t


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Gr Equ pmentsLighting 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 groundso that the nearby transformer

will not be damaged.

Line Volt.(KV) L.A.Rating(KV)

400 327220 180

132 108

33 27

CVT


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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


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Potential

transformer:- Potential Transformer or Voltage

Transformer are used in electrical

power system for stepping downthe 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, aredesigned for low voltage.

Current Transformer


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Current Transformer:-

A current transformer isused in high voltagecircuits where it is not

possible to measurecurrent directly.

A CT is a step uptransformer with only oneturn in primary. There willbe as many cores based

on the purposes likemetering, protection etc.

The secondary of a CTshould never be kept opencircuited because very highflux will be developed in thesecondary and hence itmay be damaged.

Power TRANSFORMER


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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 mutualinduction.

Most of the power transformer are

in MVA ratings.

It is the most costlier equipments

in the grid.


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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 tothe 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: Isolators:-


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Circuit breaker:- It is protective equipments in the

grid.

It is the automatic on load switch.

There are of 5 medium type ofcircuit 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.


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Conclusion:- Grid is the nodal point of the

entire power system.

It has two objectives i.e.1: Supply

Quality Power, 2:Supply the powerfrom 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 failsto 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.

R f


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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


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