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8/6/2019 32037922 Switch Yard Equipments Switching Schmes Layouts
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EHV SWITCHYARD
EQUIPMENTS, SWITCHINGSCHMES & LAYOUTS
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Switchyard Type
Conventional Air Insulated Type.
Gas Insulated type.
Outdoor Gas Insulated type.
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Selection of Bus Switching Scheme
PRE-REQUISITES
1)System security2)Operational flexibility
3)Simplicity of protection arrangements
4)Ability to limit short circuit levels (ease ofsectionalizing)
5)Maintenance Its effect on systemsecurity
6)Ease of extension
7)Total land area
8)cost
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DESIGN GUIDELINES CONTD
OPTIONS/ALTERNATIVES
1)Single sectionalised bus
2)Main and transfer bus
3)Sectionalised Main bus with transfer bus
4)Sectionalised double main and transferbus
5)Double Bus Scheme
6)Ring bus
7)One and a half breaker
8)Double bus, double breaker
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CONTD
DESIGN PRACTICES/PHYLOSOPHY
1) Consideration in Selection of Bus
Switching Scheme
2) Comparison ofSchemes
a)Sectionalized main bus with transfer bus(Scheme-I)
b)Sectionalized double main andtransfer bus (Scheme-II)
c) One and a half breaker (Scheme-III)
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DISCUSSIONS OF SCHEMES
SCHEME1
Main and Transfer Bus Scheme
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SCHEMES CONTD
SCHEME 2
Sectionalised Double Main and Transfer Bus Scheme
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SCHEMES CONTD
SCHEME 3
One and Half Breaker Bus Scheme
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SystemSecurity(Reliability
i) feeder fault
ii) Bus fault
iii)Redundancy indesign
Main & Transfer
i) requireoperation ofone breaker
ii) supply wouldbe interrupted
until all thefeeders aretransferred tothe healthy bus
iii) No alternatepath
(Offline
redundancyavailable)
Double Main &Transfer
i) requireoperation of
one breaker
ii) supply wouldbe interrupteduntil all thefeeders aretransferred tothe healthy bus
iii) No alternatepath
(Offlineredundancyavailable)
One & HalfBreaker
i)requireoperation oftwo breakers
ii) continuity ofsupply is
maintainedbecause eachcircuit gets fedthrough twopaths
iii) Alternatepath is
available(Onlineredundancyavailable)
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OperationalFlexibility:
SimplicityofProtectionArrangements
AbilitytolimitShortCircuitLevels (Easeof
Sectionalizing)
Switching operation
to take out the
breaker from the bay
more extensive
Protectionarrangementinvolves AC &DC
switching .
Sectionalising ofbus bars or
introduction ofreactors in buseswith a view tolimit short circuitlevel is adoptable.
Switching operation
to take out the
breaker from the
bay more extensive
Protectionarrangementinvolves AC &DCswitching & bus
differentialprotection iscomplicated as itinvolves CTswitching.
Sectionalising of
bus bars orintroduction ofreactors in buseswith a view tolimit short circuitlevel is adoptable.
A breaker can be
taken out of service
without the need for
additional switching
Protectionarrangement issimplified as noAC &DCswitching involve
and Busdifferentialprotection issimple.
Sectionalising ofbus bars or
introduction ofreactors in buseswith a view tolimit short circuitlevel is adoptable.
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Easeofextension
Totallandarea
Cost
Switchyard shallbe suitable forfuture extensionwithout loss of
feeders. Thisscheme isflexible for suchfuture additions
This schemeoccupy more orless the sameland area as ofthe other twoschemes.
one breaker perfeeder isrequired
Switchyard shallbe suitable forfuture extensionwithout loss of
feeders. Thisscheme isflexible for suchfuture additions
This schemeoccupy more orless the sameland area as ofthe other twoschemes.
one breaker perfeeder isrequired
Switchyard shallbe suitable forfuture extensionwithout loss of
feeders. Thisscheme isflexible for suchfuture additions
This schemeoccupy more orless the sameland area as ofthe other twoschemes.
Three breakerper 2 feeder isrequired
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Switchyard layout
Objective:
Substation layout consists essentially inarranging a number of switchgear
components in an orderly pattern governed bytheir function and rules of spatial separationas described in electrical single line diagram.
Pre-requisites:
1) single line diagram
2) general layout plan of power plant
3) orientation of line evacuation
4) control room building
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LAYOUT CONTD
Options/Alternatives
The layout will vary for the
following:1) Switching schemes
2) Type of insulation - AirInsulated/Gas Insulated.
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LAYOUT CONTD
DesignPhilosophy/Practice
1)Space around the switchyard
2)Switchyard location3)Switchyard fencing.
4)Clearance.
i) phase to earth clearance
ii) phase to phase clearanceiii) section clearance
iv) ground clearance
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TABLE I: INSULATION LEVELS & CLEARANCE
REQUIREMENTS AT DIFFERENT VOLTAGE LEVELS
NOMINA
L
SYSTEM
VOLTAG
E
KV
INSULATION LEVELS HIGHESTSYSTEM
VOLTAGE
KV
MINIMUM CLEARANCE GROUNDCLEARA
NCE
(MM)
SECTIONAL
CLEARA
NCE
(MM)
HEIGHTOF
SUPPOR
TS (mm)LIGHTNING
IMPULSE
LEVEL
(kVp)
SWITCHING
SURGE
LEVEL
(kVp)
POWER
FREQUEN
CY
IMPULSE
LEVEL
(kVrms)
BETWEEN
PHASE
AND
EARTH
(MM)
BETWE
EN
PHASES
(MM)
33
66
132
220
400
765
170
325
650
1050
1425
2100
-
-
-
-
1050
1550
70
140
275
460
630
830
36
72.5
145
245
420
800
320
630
1300
2100
3500
6400
320
630
1300
2100
4000
9400
3700
4000
4600
5500
8000
--
2800
3000
3500
4300
6500
10300
2500
2500
2500
2500
2500
2500
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Clearance contd
5)Equipmentspacing
a) Ease of maintenance/removal ofequipment.
b) Equipment foundation & theircable trenches.
c) Distance between LA andequipment based on theprotection reach of LA.
d) The spacings are generally keptin order to achieve
various clearances specified
at Table-I.
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Clearance contd
6) Busbars:The bus bars of 400 kV switchyard are generally made up 4 IPSaluminum tube or Quad Moose rated for 3000 A.The bus bars of 220/132kV switchyard are generally made up of 3 IPSaluminum tube or quad/ twin moose conductor. Bus bars are placed atright angles to the feeders for tapping the power.
7)Equipment Interconnection
8)Spacer spans and locations
9) Connection Level
10) Land &Road Layout
11)Sequence and mounting of line traps
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Clearance contd.
12) Control Room Layout
13) Lighting System
14) Cabling Philosophy
15) Gravel Filling
16)Earthing System
17) Lightning Protection System
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EVOLVING A SUBSTATION
LAYOUT
LAYING OUT A SUBSTATION INVOLVESSTEP-BY-STEPPROCEDURE. MOST IMPORTANT POINTS TO BECONSIDERED ARE BRIEFLY DESCRIBED BELOW:
THE IMPORTANT ELECTRICAL PARAMETERS AREESTABLISHED BY THESYSTEMDESIGN. THEMAINPARAMETERS ARE:
1) THE VOLTAGE AND BASIC INSULATION LEVEL ORSWITCHING SURGE LEVEL., THESITE AND CLIMATICCONDITIONS, THEMETHOD OF CIRCUIT CONNECTION,
ANDSWITCHING OVER-VOLTAGE CONDITIONS.
2) THE BUS BARSYSTEMDIAGRAM, THE NUMBER OFCIRCUITS AND THEIRPURPOSE I.E. THE CONTROLOF GENERATORS, TRANSFORMERS, FEEDERS, ETC.
THEDIAGRAMSHOULD INCLUDEDETAILS OF
EXTENSIONS AND FUTURE CONVERSION TO ADIFFERENT BUS BAR SYSTEM, IF INTENDED.
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EVOLVING A SUBSTATION
LAYOUT
1) THE CONTINUOUS CURRENT RATING OF THE BUS BARSAND CIRCUITS.
2) THESHORT CIRCUIT RATING OF BUS BARS ANDEQUIPMENTS.
3) PARTICULARS OF REACTORS, NEUTRAL EARTHINGEQUIPMENT ANDREACTING, InterconnectingTransformers REQUIRED.
4) METHOD OF CONNECTION OF CIRCUITS, WHETHER BYOVERHEAD LINES OR BY CABLES.
5) DETAILS OF LIGHTNING PROTECTION EQUIPMENT.
6) DETAILS OF PROTECTIVEEQUIPMENT, DETERMININGTHE INSTRUMENT TRANSFORMERSREQUIREMENTS,CARRIER CURRENT EQUIPMENT ETC.
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PREPARATION OF BASIC
LAYOUT
WHILEMEETINGALLTHE NEEDSESTABLISHEDTHEFOLLOWINGIDEALSSHOULD BEAIMEDATIN MAKINGTHEBASICCIRCUITLAYOUT.
MINIMUMGROUNDAREA
MINIMUMQUANTITIES OF CONDUCTOR, JOINTSANDSTRUCTURE
MINIMUM NUMBER OF INDEPENDENTINSULATORS,ESPECIALLYIN THE BUS BAR ZONE.
AFTERHAVINGDETERMINEDTHEELECTRICALCLEARANCE BE
USEDAROUGHCIRCUITLAYOUTISMADE. SEVERALPOSSIBLEALTERNATIVESAREPREPARED FROM WHICHTHEMOSTSUITABLE ONE WILL BESELECTED. SOMEVARIATIONIS NEEDED,TO MEETTHEREQUIREMENTS OF DIFFERENTTYPES OF CIRCUIT.
ITISALSO NECESSARYTO CALCULATESHORTCIRCUITANDATMOSPHERIC FORCESTO DETERMINETHESTRESSESIN
CONDUCTORS,INSULATORSANDSTRUCTURES. THESEHELDIN DECIDINGTHEMOST OPTIMUMDIMENSIONS.
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PURPOSE OF EARTHING
THE OBJECT OF EARTHING IS TO MAINTAIN ALOW POTENTIAL ON ANY OBJECT.
THEP
URP
OSE OF A EARTHING SYSTEM IN ASUBSTATION AREA IS TO LIMIT THEPOTENTIALGRADIENT WITHIN AND IMMEDIATELY OUTSIDETHE AREA IS A VALUE, SAFE FOR THE WORKINGPERSONNEL. SAFETY IS TO BEENSURED UNDERNORMAL AS WELL AS ABNORMAL OPERATING
CONDITION.
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REQUIREMENTS OF A GOOD
EARTHING SYSTEM
FOLLOWING BASIC REQUIREMENTS ARE TO BESATISFIEDSO AS TOENSURE A PROPER ANDSOUNDEARTHING SYSTEM.
1) THEEARTHRESISTANCE FORTHESWITCHYARDAREASHOULD BELOWERTHAN ACERTAIN LIMITING VALUERAIN ORDER TO ENSURETHATA SAFEPOTENTIAL
GRADIENTISMAINTAINEDIN THESWITCHYARDAREAANDPROTECTIVERELAYEQUIPMENT OPERATESATISFACTORILY. FORMAJORSWITCHYARDSANDSUBSTATIONSIN INDIA,THISLIMITINGVALUE OF EARTHRESISTANCE (RA)ISTAKEN TO BELESSTHAN 0.5 OHM.
2) THEGROUNDINGCONDUCTORMATERIALSHOULD BECAPABLE OF CARRYINGTHEMAXIMUMEARTH FAULT
CURRENT WITHOUT-OVERHEATINGANDMECHANICALDAMAGE. THEMAXIMUM FAULTLEVELIN THE 400 KVSYSTEMHAS BEEN ESTIMATEDTO BE 40 KAANDTHISVALUE OF FAULTCURRENTTO USEDISTHEDESIGN OFEARTHMAT FORTHE 400 KVSUBSTATION.
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REQUIREMENTS OF A GOOD
EARTHING SYSTEM
ALL METALLIC OBJECTS WHICH DO NOT CARRYCURRENT AND INSTALLED THESUBSTATION SUCHASSTRUCTURES, PARTS OF ELECTRICALEQUIPMENTS, FENCES, ARMOURING ANDSHEATHSOF THE LOW VOLTAGEPOWER AND CONTROL
CABLESSHOULD BE CONNECTED TO THEEARTHING ELECTRODESYSTEM.. THEDESIGN OF THE GROUND CONDUCTOR
SHOULD TAKE CARE OF THEEFFECT OFCORROSION FOR THE TOTAL LIFESPAN OF THEPLANT.
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Switchyard Equipments.
Circuit Breaker.
Disconnectors (Isolators)
Current Transformers. Capacitor Voltage Transformers
(CVT).
Lightning Arrestors.
Post Insulators. Wave Traps
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General Parameters
Dielectric Parameters .(IEC 694)
- Power Frequency Voltage.
- Lightning Impulse Voltage.- Switching Impulse Voltage.
- Corona Extinction Voltage.
- RIV Level.
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General Parameters (Contd.)
Rated Current.
Short Time Current.
Creepage Distance.
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Circuit Breakers Type (IEC: 62271-100)
MOCB.
ABCB.
SF6
Rated operating duty cycle- O-0.3 sec-
CO-3 min.-CO Operating mechanism
Total Break Time
Pre Insertion Resistor ( 300-450)
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Disconnectors
HCB Type.
Double Break Type.
Pantograph type. Vertical Break type.
Provision ofEarth Switches.
Motor / manual operated. Gang operated/Single pole type.
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Current Transformer ( IEC 0044, IS
2705)
Dead tank/Live tank type.
Bar Primary type.
Ring Type.
No. of Cores.
Ratio.
Accuracy.
rated primary current
Rated burden for metering
Knee Point voltage
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Capacitor Voltage Transformer (IEC
0044, IS 56)
Capacitance.
Voltage Ratio.
No. Of Cores. Accuracy.
Output Burden
Rated Secondary Voltage
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Lightning Arrestor ( IEC 60099)
Gap Type / Gapless Type.
Voltage Rating.
Energy Capability. Monitoring.
Location.
Nominal Discharge Current.
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Post Insulators
Voltage Rating.
Cantilever Strength.
Fixing Details.
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Wave Trap (IEC 60353)
Rated Inductance(0.5/1.0 mH).
Rated current.
Band Width. Coupling (Phase to Phase).
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SWITCHYARD AUXILIARY SYSTEMS
CONTROL ROOM
HVAC FORCONTROL ROOM
A RELIABLE 415V AC SUPPLY ( LT SWGR)
220 V & 48 V DC SUPPLY( BATTERY &BATTERY CHARGER)
POWER & CONTROL CABLE
LIGHTING ( Yard lighting & indoor lighting of
control room) Other items-Clamps, connectors , Insulator strings ,
BMK etc.
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192
69 ~10%400kV GIS
275kV GIS
Trfr
Trfr 2 Trfr3 Trfr4 SVC Trfrs
400kV AIS
275kV AIS
COMPARASON BETWEEN AIS ANDGIS SUBSTATION
FOOTPRINT FOR HECTOR
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INDOORGIS
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OUTDOORGIS - SEISMIC AREAS
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Conductor
Phase Spacing
PHASE SPACING
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OVERHEAD STRUNG BUSBARS
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9,81.mi
fs
SAGDUE TO CONDUCTOR
fs = 9,81.mi.Lc2
8.T
fs = maximum conductor sag (m)
mi = mass of conductor (kg/m)
Lc = conductor span length (m)
T = tension per conductor (N)
T
Lc
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LOW PROFILE SUPPORTEDTUBULAR BUSBAR SUBSTATIONS
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TUBE SAG EXCESSIVE INCORRECTLY SELECTED
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TYPICAL TUBULAR BB BUS SECTION BAY
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MMM
Attraction Repulsion
CANTILEVER FORCES DUE TO FAULT CURRENT
COMBINATION SUPPORT STRUCTURE FOR 3 PHASES
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F S
TUBE
TUBULAR BUSBAR EXPANSION CLAMP
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TRANSFORMER FIRE AT MINERVA
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Upgradation of transmission voltage
from 400kV AC to 765kV AC.
Presently the highest AC Transmission voltage is 400kV only.NTPC is fully geared up for implementing next AC voltage of765kV.
Advantages: Step up from generation voltage to 765kV.
High Capacity Transmission to the order of 2500MW per linewith lower right of way requirement. 765kV Transmission system is techno economically better
option whenever power transmission system requires multipoint tapping at various location for catering the loadrequirement of high growth area.
765kV system offers low transmission losses, resulting inhigher utilisation of generating capacity and optimises the
resource required for capacity addition.
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((((
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ADOPTION OF CONTROLLED SWITCHING OF TRANSFORMER AND
REACTORS.
Switching of transformer, shunt reactors, capacitors and uncharged overhead
lines is normally a 'three phase' process, where all three phases are switched
simultaneously. The actual circuit closing or opening instant is left up to
chance. This results in high inrush currents or switching surges causing undue
repercussions to switchgear equipment and networks system. For overcoming
this the switching in and out is done at desired point on wave so that theovervoltages are reduced.
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765KV CIRCUIT BREAKER
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THANK YOU!