STUDY & DESIGN OF 66/33/25KV

GIS SUBSTATIONDMRC NEW DELHI

PROJECT REPORT

BACHELOR OF ENGINEERING

IN

ELECTRICAL ENGINEERING

UNDER THE SUPERVISION OF

SHEERAZ KIRMANI

ASST. PROFFESOR

FACULTY OF ENGG.&TECHNOLOGY

JAMIA MILLIA ISLAMIA PRESENTED BY

NEW DELHI-110025 DEEPAK KUMAR(11BE108)

GANESH KUMAR (11BE116)

INTRODUCTION

GAS INSULATED SUBSTATIONS• GAS INSULATED USES SULFUR HEXAFLUORIDE (SF6)• WHICH HAS A SUPERIOR DIELECTRIC PROPERTIES USED AT

MODERATE PRESSURE.

• IN GAS INSULATED SUBSTATION THE HIGH VOLTAGE CONDUCTORS, CIRCUIT BREAKER INTERRUPTERS,SWITCHES,CURRENT TRANSFORMER ,VOLTAGE TRANFORMER AND LIGHTINING ARRESTERS ARE ENCAPSULATED IN SF6 GAS INSIDE GROUNDED METAL ENCLOSURES.

• THE GAS INSULATED SUBSTATION IS PREFERRED FOR LOCATIONS SUCH AS LARGE CITIES AND TOWNS,

• UNDER GROUND STATIONS,AND MOUNTAINS AND VALLEY REGIONS

It consist of

• Bus Bars

• Circuit Breakers

• Disconnecting Switches

• Earthing Switches

• Current Transformers

• Voltage Transformers

• Cable and Boxes

• Gas Supply and Gas Monitoring Equipment

• Local Control

Circuit Breaker Under short circuit

conditions, however,

the current may reach

tens of thousands of

amperes at a power

factor as low as 0.1. It

is duty of a circuit

breaker to interrupt

such currents as soon

as possible to avoid

equipment damage.

Disconnectors

•Disconnectors or isolators

are used for electrical

isolation of circuit parts

•They are slow acting and

operating at off load

•Disconnectors must be

carefully designed and tested

to be able to break small

charging current without

generating too-high over

voltage,

Earthing Switch Earthing switch is used to earth the

live parts during maintenance and

during testing.

During maintenance although

circuit is open still there are some

voltages on line , due to

which capacitance between line

and earth is charged.

Before proceeding to maintenance

work the voltage is discharged to

earth, by closing the earth switch.

Voltage Transformer Voltage transformer is connected to

switchgear with the connecting flanges

with a barrier insulator.

primary winding is insulated with

SF6 gas & connected to high voltage

terminal.

The primary winding is wounded

on the top of the core & secondary

windings.

secondary winding is connected to the

terminals in the external terminal box

through a gas tight multiple bushing.

Current Transformer In the single phase enclosed

Core of CT is located outside

the enclosure inside for three

phase

Gas compartment to reduce

access of moisture and to

suppress gas-tight bushings for

secondary connections.

Cables Compartment

1. Optimized solution for

plug-in type power

cable connection.

2. Adjustable support

structures for minimum

requirements for the

GIS floor.

3. Fixation to the GIS

floor by cemented

anchor bolts, no need

for special foundation

(steel beams….etc)

TECHNICAL SPECIFICATION

ENCLOSURE TYPE : THREE PHASE ENCLOSURE

RATED VOLTAGE : 72.5 KV RMS

RATED FREQUENCY : 50HZ

RATED CURRENT OF 2500 A RMS

BUS BAR

RATED SHORT TIME : 40 KA RMS,3 SEC

CURRENT

GUARANTED SF6 GAS : LESS THAN 1%

LOSSES PER YEAR

SINGLE LINE DIAGRAM OF 66/33/25 KV GIS SUBSTATION

AUXILIARY MAIN TRANSFORMER(66/33 KV,30/45 MVA)

DESCRIPTION

UNIT ONAN ONAF

RATING MVA 30 45

RATED

PRIMARY

VOLTAGE

KV 66 66

RATED

SECONDARY

VOLTAGE

KV 33 33

RATED

PRIMARY

CURRENT AT

66 KV

A 262.43 393.65

RATED

SECONDARY

CURRENT AT

33 KV

A 524.86 787.30

TRACTION TRANSFORMER(66/25 KV,40/50 MVA)

DESCRIPTION UNIT ONAN ONAF

RATING MVA 40 50

RATED PRIMARY VOLTAGE KV 66 66

RATED SECONDARY VOLTAGE KV 25 25

RATED PRIMARY CURRENT

AT 66 KV

A 606.06 757.58

RATED SECONDARY CURRENT

AT 33 KV

A 1600.00 2000.00

66 KV LINE CKT BREAKER

DESCRIPTION UNIT CALCULATED SELECTED

RATED VOLTAGE KV 66 66

RATED PRIMARY

CURRENT AT 66

KV

A 1151.22 2000

66 KV LINE ISOLATOR

DESCRIPTION UNIT CALCULATED SELECTED

RATED

VOLTAGE

KV 66 66

RATED PRIMARY

CURRENT AT 66

KV

A 1151.22 2000

PROPERTIES OF SF6

•SF6 does not harm to

the ozone layer.

•Sf6 gas is chemically stable

•Non poisonous

•Colourless & heavier than air

•Almost water insoluble

•Non inflammable

Comparison b\w Gis & Ais

ADVANTAGES

• Main advantage of GIS over AIS is its phase to phase spacing decreases significantly. This is more effective in urban environment where land and its size is at a premium

• Gis have no risks for fire & explosion.• They generate no noise & have no radio interference• It offer solutions including-In industrial areas where space & pollution problems-Mountain areas where ice & snow are major problems

DISADVANTAGES

GIS installations tend to be much more expensive that air-insulated installations with the same rating.

VFTO during switching operations or earth faults and transient enclosure voltages and particle contamination

The Damage Effect Will Also Be Severe Whenever Internal Fault occurs.

APPLICATIONS

• High voltage installations.

• Urban installations

• Indoor installations

FUTURE TRENDS IN GAS INSULATED

SUBSTATIONS

Compact design of switch gear.

Use of SF6 circuit breaker cells in the medium

high voltage GIS and fewer brakes per pole in

high voltage circuit breakers

Optimization of GIS design to allow easier

maintenance

CONCLUSION• GIS are necessary for EHV & UHV

• some important areas to be studied include.

• more conservative designs.

• improved gas handling .

• Achieving & maintaining high levels of availability requires a more integrated approach to quality control by both users and manufactures