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TRANSMISSION LINES DESIGN
AND CONSTRUCTION
BY
K.VEERABHADRA RAO
RETD.CHIEF ENGINEER,AP TRANSCO
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DEVELOPMENT OF AC TRANSMISSION LINES
16-5-1888 TRANSMISSION LINE PATENT GIVEN
FIRST LINE 25 kV LINE LAUFFEN TO FRANKFURT
IN GERMANY
1912 110 kV LINE LAUCHLAMMER TO RIESA17-4-1929 220 kV LINE BRAUWEILER TO FRANKFURT
TOWERS DESIGNED FOR 380 kV
5-10-1957 380 kV LINE ROMERSKIRCHEN TO LUDWIGSBURG-
HOHENECH
1967 735 kV LINE IN HYDRO QUEBEC1982 1200 kV LINE IN SOVIET UNION
EXTREMEMELY HIGH VOLTAGE TRANSMISSION BEYOND 2000
kV NOT PREFERED DUE TO HIGH CORONA
DISCHARGELOSSES MORE THAN LOSSES DUE TO LINE
RESISTANCE
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DESIGN BASIS
1.ECONOMIC FACTORS
2.NETWORK SAFETY
3.REDUNDANCY
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MAIN COMPONENTSMAIN COMPONENTS
1. CONDUCTOR
2. CONDUCTOR ACCESSORIES
a) REPAIR SLEEVES b) COMPRESSION JOINTS
c) VIBRATION DAMPERS d) SPACERS / SPACER
DAMPERS
3. EARTH WIRE
a) COMPRESSION JOINTS
b) VIBRATION DAMPERS
c) COPPER EARTH BONDS
4. INSULATORS
5. EARTHING/ COUNTER POISE EARTHING SETS
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6. INSULATOR STRING HARDWARE
a) SUSPENSION STRING HARD WARE
b) TENSION STRING HARD WARE
7. OPGW
8. EARTH WIRE /OPGW HARDWARE
9. TOWERS
10.TOWER ACCESSORIES
a) PHASE PLATES b) DANGER BOARDS
c) BIRD GAURDS d) ANTI CLIMBING DEVICES
e) STEP BOLTS
MAIN COMPONENTSMAIN COMPONENTS contd..contd..
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CONDUCTORS
1. COPPER
2 .COPPER CONDUCTOR STEEL REINFORCED
3. ALUMINIUM
4. ALL ALUMINIUM ALLOY CONDUCTORS(AAAC)
5. ALUMINIUM ALLOY CONDUCTOR STEEL
REINFORCED(AACSR)
5. ALUMINIUM CONDUCTOR STEEL
REINFORCED(ACSR)
6. ALUMINIUM CONDUCTOR ALUMINIUM CLAD
STEEL REINFORCED - ACSR(AS)
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ADVANTAGES OF ACSR
1. MORE SPAN-LESS SAG
2. LARGER DIA -LESS CORONA LOSS FOR UHV
LINES
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STANDARDS
1. IS:398 IEC-1098-1991:
SPECIFICATION FOR ALUMINIUM
CONDUCTORS FOR OVERHEAD
TRANSMISSION LINES
2 IS-398 PART-II : ACSR
3. IS-398 PART-V : ACSR FOR 400 kV AND ABOVE
4. IEC-1232 : ALUMINIUM CLAD STEEL WIRES FOR
ELECTRICAL PURPOSES
5.IS-1778 :REELS AND DRUMS FOR BARECONDUCTORS
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PRINCIPAL PARAMETERS OF ACSR
1. APPLICABLE STANDARDS
2. NO./WIRE DIA.AL./STEEL
3. SECTIONAL AREA OF ALUMINIUM (SQ,mm)
4. TOTAL SECTIONAL AREA (SQ,mm)
5. OVERAL DIA.(mm)
6. APPROXIMATE WT(.KG / KM)
7. DC RESISTANCEAT 20 DEG.C( OHM/KM)
8. ULTIMATE TENSILE STRENGTH ( KN)
9. FINAL MODULUS OF ELASTICITY (KG/cm)
10. COEFFICIENT OF LINEAR EXPANSION (PER DEG.C)
11.LAY RATIO( MAX./MIN.)
12.TECHNICAL PARTICULARS OF STEEL AND AL.STRANDS
a) strand dia. b) cross sectional area c) wt./km d) min.breaking load befor
stranding and after stranding KN e)zinc coating of steel wire f) joints in
strands g) chemical composition of steel wire
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IMP. TYPE TESTS
1.ULTIMATE TENSILE STRENGTH
2.CORONA EXTINSION VOLTAGE
3.RADIO INTERFERENCE VOLTAGE
4.DC RESISTANCE
5.STESS STAIN TEST
This test is to collect the creep data of theconductor.Creep is due to settlement of strands and due tonon -elastic elongation of metal when subjected toload.The manufacturer shall furnish the amount of creep in
10,20,30,40,50 years along with supportingcalculations.The calculation to be based on every daytemp. and tension 22 % of UTS. for 400 kV
and 25 %UTS for 220 kV
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INSULATOR STRINGS
TYPES OF INSULATORS1. PORCELAIN DISC INSULATORS,LONG ROD
INSULATORS2.TOUGHENED GLASS3.POLYMER SILICON RUBBER/ALLOY OF SILICON
RUBBER AND EPDM
NORMAL SIZES1.254 X 145 mm 70KN/90KN EMS. 280mm CREEPAGE2.280 X 170 mm 120 KN/160KN,
280mm/330mm/430mm CREEPAGE3.305 X 145 mm 120 KN,
280mm /330mm/430mm CREEPAGE4.305 X 170 mm 160 KN
280mm /330mm/430mm CREEPAGEBALL DIA--16mm, 20mm
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INSULATOR STRINGS---- CONTINUED
TYPES OF STRINGS
1.SINGLE SUSPENSION
2.DOUBLE SUSPENSION
3.SINGLE TENSION
4. DOUBLE TENSION
5.V-SRTING
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CONSTRUCTION WORKSCONSTRUCTION WORKS
1. SURVEYS
a) ROUTE ALIGNMENT
b) DETAILED SURVEY c) CHECK SURVEY
i) PROFILES
ii) SOIL PARTICULARS
iii) SAG TEMPLATE
iv)TOWER SPOTTING
v) RIGHT OF WAY
2. APPROVALS FROM CONCERNED
a) ROAD CROSSINGS
i) RAIL CROSSINGS ii) TELECOM LINES
iii) RIVER CROSSINGS iv) AIR PORT AUTHORITIES
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CONSTRUCTION WORKSCONSTRUCTION WORKS contd..contd..
3. FOUNDATIONS
i) DESIGN FOR DIFFERENT SOILS ii) EXCAVATION PLAN
iii) FORM BOXES iv) STUB SETTING
v) CONCRETING vi) REVETMENTSvii) EARTHING
4. TOWER ERRECTION
i) TOWER SCHEDULES ii) INSEPCTION AND SORTING
OUT MEMBERS
iii) TREATMENT OF JOINS iv) ASSEMBLY
v) TIGHTENING AND PUNCHING OF BOLTS AND NUTS
vi) FIXING ACCESSORIES
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CONSTRUCTION WORKSCONSTRUCTION WORKS contd..contd..
5. INSULATOR HOISTING
6. POWER AND EARTH CONDUCTOR ERRECTION
i) DELIVERY OF CONDUCTOR AT SITE ii) PAYING OUT AND STRINGING
iii) TENSIONING AND SAGGING iv) CLIPPING -IN
7. FIXING OF CONDUCTOR AND EARTH WIRE ACCESSORIES
8. FINAL CHECKING
9. TESTING AND COMMISIONING
i) CONDUCTOR CONTINUITY TEST ii) INSULATION RESISTENCE TEST
iii) TO BE CHARGED AT LOW VOLTAGE
iv) STATUTORY REQUIREMENTS TO BE MET
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COST COMPONENTSCOST COMPONENTS
1. TOWERS AND ACCESSORIES 28%
2. ACSR CONDUCTOR AND ACCESSORIES 36%
3. EARTH WIRE AND ACCESSORIES 01%4. INSULATOR AND STRINGS 06%
5. FOUNDATIONS 04%
6. ERRECTION 14%
7. CENTAGES 11%
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DESIGN BY PROBABILISTIC METHODDESIGN BY PROBABILISTIC METHOD
IECIEC--826826CLIMATIC LOADS
a) RETURN PERIODS OF CLIMATIC EVENTS
1) 50 YEARS
2) 150 YEARS3) 500 YEARS
b) DRAG COEFFICIENT OF CONDUCTOR
c) TERRAIN CATEGORIES
DESIGN CONSIDERATIONS
a) RELIABILITY (STRUCTURAL)
OR
PROBABILITY OF SURVIVAL
b) SECURITY (STRUCTURAL)
c) SAFETY
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DESIGN BY PROBABILISTIC METHODDESIGN BY PROBABILISTIC METHODIECIEC--826826
COORDINATION OF STRENGTH OF COMPONENTS
--------------------------------------------------------------------------------------------------------
MAJOR COORDINATION WITH
COMPONENT MA JOR COMPONENTS
--------------------------------------------------------------------------------------------------------TO FAIL FIRST TANGENT TOWER TOWER,FOUNDATIONS,
HARDWARE
NOT TO FAIL FIRST ANGLE TOWER TOWER,FOUNDATIONS,
WITH 90% CONFIDENCE HARDWARE
DEAD END TOWER TOWER,FOUNDATIONS,
HARDWARECONDUCTOR CONDUCTORS, INSUL-
LATORS, HARDWARE
NOTE: WITH IN EACH MAJOR COMPONENTS THE UNDERLINED
COMPONENT IS THE WEAKEST WITH 90% CONFIDENCE
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LOADINGS ON TRANSMISSION LINESLOADINGS ON TRANSMISSION LINES
LIVE LOADS
1. WIND LOADS
a. NON-SNOWY REGIONS
b. WITH ICE SNOWY REGIONS
c. WITHOUT ICE SNOWY REGIONS
2. DEAD LOADS
a. WEIGHT OF TOWER
b. WEIGHT OF CONDUCTORS,
c. HARDWARE AND INSULATORS
3. SPECIAL LOADS
a. EXTERNAL LOADS DURING
b. CONSTRUCTION AND MAINTENANACE
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REQUIREMENT OF LOADSREQUIREMENT OF LOADS
1.RELIABILITY REQUIREMENTS
CLIMATIC LOADS UNDER NORMAL CONDITIONS
2.SECURITY REQUIREMENTS
FAILURE CONTAINMENT LOADS UNDER BROKEN WIRE CONDITION
3.SAFETY REQUIREMENTSLOADS DURING CONSTRUCTION AND MAINTENANCE LOADS
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METHODOLOGY FOR THE DESIGNMETHODOLOGY FOR THE DESIGNOF TRANSMISSION LINESOF TRANSMISSION LINES
ESTABLISH SAFETY
REQUIREMENTSSELECT SECURITY
REQUREMENTS
SELECT
RELIABILITY
CALCULATE
CONSTRUCTION
AND MAINTENANCE LOADS
CALCULATE LOADS
RELATED TO
SECURITY
CALCULATE
CLIMATIC LOADS
COMBINE ALL LIMIT
LOADS
CHECK SAFETY
REQUIREMENTSFROM
NATIONAL
REGULATIONSCALCULATE STRENGTH
NEEDED TO COMPLY
WITH ALL LOADS AND
REQUIREMENTS
DESIGN COMPONENTS
FOR LOADS AND
STRENGTH
REQUIREMENTS
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TOWER OUTLINETOWER OUTLINE
1. TOWER HEIGHT
2. TOWER WIDTH
3. CROSS ARM WIDTH
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ELECTRICAL CLEARANCESELECTRICAL CLEARANCES
1. MIN.GROUND CLEARANCE
2. MIN.CLEARANCE ABOVE HIGHEST FLOOD LEVEL
3. CLEARACE AND SWING ANGLES
4. AIR CLEARANCE
5. POWER LINE CROSSINGS
6. TELECOM.LINE CROSSINGS
7. RAIL TRACK CROSSINGS
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DESIGN PARAMETERSDESIGN PARAMETERS
1. NO.OF CIRCUITS
2. CLIMATIC CONDITIONS
a. WIND
b. TEMPERATUREc. ISOKERANIC LEVEL
d. SEISMIC INTENSITY
e. ICE FORMATION
3. ENVIRONMENT AND ECOLOGICAL CONSIDERATIONS
4. CONDUCTOR
5. EARTH WIRE
6. INSULATOR STRINGS
7. SPAN
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LOADINGSLOADINGS
1. CLIMATIC LOADS RELATED TO RELIABILITY REQUIREMENTS:
WIND LOADS
i) SNOWY WITH ICE ii) SNOWY WITH OUT ICE
iii) NON SNOWY
2. FAILURE CONTAINMENT LOADS RELATED TO SECURITY
REQUIREMENTS.
i) LONGITUDINAL LOADS ii) TORSIONAL LOADS
iii) ANTI CASCADING LOADS
3. LOADS DURING CONSTRUCTION AND MAINTENANCE LOADS
RELATED TO SAFETY REQUIREMENTS.
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LOADINGSLOADINGS contd..contd..
NATURE OF LOADS
1. TRANSVERSE LOADS(T)
WIND LOAD ON TOWER STRUCTURE, CONDUCTOR, GW &
INSULATOR STRING
COMPONENT OF MECHANICAL TENSION2. VERTICAL LOADS(V)
SELF WEIGHT
LOADS DURING CONSTRUCTION AND MAINTENANCE
3. LONGITUDINAL LOADS(L)
RELIABILITY CONDITION(NORMAL CONDITION),
SECURITY CONDITION (BROKEN WIRE CONDITION) AND
SAFETY CONDITION (CONSTRUCTION AND MAINTENANCE)
HAVE ALL THE ABOVE LOADS UNDER THEIR LOADING
COMBINATIONS.
SAFTETY CONDITION HAS BOTH NORMAL AND BROKEN WIRE
CONDITION.
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ANTI CASCADING CHECKSANTI CASCADING CHECKS
ALL ANGLE TOWERS SHALL BE CHECKED FOR ANTI CASCADING
CONDITIONS WITH ALL THE CONDUCTORS AND G.W. INTACT
ONLY ON ONE SIDE.
1. TRANSVERSE LOADS(T) : UNDER NO-WIND CONDITION
2. VERTICAL LOADS(V) : CONDUCTOR, GW WEIGHTS ON
ONE SIDE ONLY, WEIGHT OF INSULATOR STRINGS AND
ACCESSORIES
3. LONGITUDINAL LOADS(L): PULL OF CONDUCTOR/GW AT
EVERY DAY TEMPERATURE AND NO-WIND APPLIED
SIMULTANEOUSLY AT ALL POINTS ON ONE SIDE WITH ZERO
DEGREE DEVIATION.
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BROKEN WIRE CONDITIONBROKEN WIRE CONDITION
(BWC)(BWC)SINGLE CIRCUIT: ONE PHASE OR GW BROKEN WHICH EVER IS
MORE STRINGENT FOR A PARTICULAR MEMBER
MULTI CIRCUIT:
SUSPENSION TOWER: ANY ONE PHASE OR GW BROKEN WHICH
EVER IS MORE STRINGENT FOR A PARTICULAR MEMBER
SMALL ANGLE TOWERS: ONE PHASE AND GW OR TWO PHASES
BROKEN ON ONE SIDE.
LARGE ANGLE TOWERS/DEAD END TOWERS: ANY THREE
PHASES BROKEN ON THE SAME SIDE OR ANY TWO PHASES
AND GW BROKEN ON THE SAME SIDE.
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DESIGN OF TOWER MEMBERSDESIGN OF TOWER MEMBERS
STRESS ANALYSIS:
1. GRAPHICAL DIAGRAM METHOD: NOW OBSOLETE
2. ANALYTICAL METHOD
3. COMPUTER AIDED ANALYSIS: 3D ANALYSIS
SELECTION OF MATERIAL
i) BOLT DIAMETER FLARGE WIDTH16MM 45 MM
ii) MINIMUM THICKNESS: 5 MM LEG
4MM BRACINGS/REDUNDENT MEMBERS
iii) GRADE OF STEEL : MILD STEEL AND HIGH TENSILE STEEL
iv) STENDERNESS RATIO:
LEGS < 120
BRACINGS < 200
REDUNDENT < 250
TENSION < 400
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DESIGN OF TOWER MEMBERSDESIGN OF TOWER MEMBERS contd..contd..
PERMISSIBLE STRESSES
SELECTION OF MEMBERS
BOLTS & NUTS
i) CLASS 4.6
ULTIMATE BEARING STRESS - 4440 Kgf/cm2
ULTIMATE SHEARING STRESS - 2220 Kgf/cm2
ii) CLASS 5.6
ULTIMATE BEARING STRESS - 6322 Kgf/cm2
ULTIMATE SHEARING STRESS -3161 Kgf/cm2
FOR 16 mm DIA BOLTS
i) CLASS 4.6
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TESTING OF TOWERSTESTING OF TOWERS
TOWER TESTING STATION
1. TEST BED
2. PERMANENT ANCHORS: LONGITUDINAL MOST
3. ARRANGEMENT FOR APPLYING THE COMBINATION OF LOADS
4. ELECTRICAL WRINCHES (REMOTE CONTROLLED)
5. INSTRUMENTS TO RECORD THE LOAD APPLIED:
MECHANICAL SPRING GAUGES OR ELECTRICAL /
ELECTRONIC TRANSDUCEROS/DYNAMO METERS
6. CONTROL ROOM
7. THEODOLOTES TO OBSERVE DEFLECTION OF TOWER
TESTING
1. BOLT SLIP TEST 2. BWC/ANTI CASCADE CONDITION
3. NC 4. DESTRUCTION TEST
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APPLICATION OF LOADSAPPLICATION OF LOADS
TRANSVERSE, LONGITUDINAL LOADS AND VERTICAL LOADS
AT PEAK AND RESPECTIVE CROSS ARM POINTS.
WIND LOAD ON TOWER BODY SIMULATED ATA. G.W.
B. CROSS ARM LEVELS
C. WIND BELOW CROSS ARM LEVEL TO BE
SIMULATED TO ACT AT BOTTOM CROSS ARM LEVEL
D. TOWER WITH EXTENSION AT TOP OF EXTENSION
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QUALITY ASSURANCE PLANQUALITY ASSURANCE PLAN
1. QUALITY POLICY
2. QUALITY CONTOL(QC) DEPARTMENT
3. QUALITY PLANNING
4. DESIGN AND DRAWING5. COMPANY STANDARDS
6. INSPECTION EQUIPMENT, TOOLS AND GUAGES
7. MATERIAL MANAGEMENT
8. INSPECTION OF INCOMING MATERIAL
9. BOUGHTOUT ITEMS
10. IN-PROCESS INSPECTION
11. DOCUMENTATION
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DESIGN OF FOUNDATIONSDESIGN OF FOUNDATIONS
1. TYPE OF LOADS
a. COMPRESSION OR DOWN WARD THRUST
b. TENSION OR UPLIFT
c. LATERAL FORCES OR SIDE THRUST BOTH, TRANSVERSE AND
LOGITUDINAL DIRECTIONS
2. SOIL PARAMETERS
a. LIMIT BEARING CAPACITY
b. DENSITY OF SOIL
c. ANGEL OF EARTH FRUSTRUM
3. SOIL INVESTIGATION
a. TYPY OF SOIL
b. GROUND WATER TABLE
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DESIGN OF FOUNDATIONSDESIGN OF FOUNDATIONS contd..contd..
4. TYPES OF FOUNDATIONS
a. NORMAL DRY SOIL FOUNDATION
b. WET SOIL FOUNDATION
c. PARTIAL SUBMERGED FOUNDATION
d. FULLY SUBMERGED FOUNDATION
e. BLACK COTTON SOIL FOUNDATION
f. PARITAL BLACK COTTON SOIL FOUNDATIONg. SOFT ROCK/FISSURED ROCK FOUNDATION
h. HARD ROCK FOUNDATION
i. SANDY SOIL FOUNDATION
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DESIGN OF FOUNDATIONSDESIGN OF FOUNDATIONS contd..contd..
5. STRUCTURAL ARRANGEMENT OF FOUNDATION
a. PCC TYPE
b. RCC SPREAD TYPE
c. BLOCK TYPEd. UNDER CUT TYPE
e. GROUTED ROCK AND ROCK ANCHOR TYPE
f. PILE TYPE
g. WELL TYPE
6. REVETMENT ON FOUNDATION
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THE END