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WELCOMEWELCOME

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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 RIESA

17-4-1929 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 QUEBEC

1982 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 COMPONENTS MAIN 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 BARE CONDUCTORS

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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 STRENGTH2.CORONA EXTINSION VOLTAGE3.RADIO INTERFERENCE VOLTAGE4.DC RESISTANCE5.STESS STAIN TEST

This test is to collect the creep data of the conductor.Creep is due to settlement of strands and due to non -elastic elongation of metal when subjected to load.The manufacturer shall furnish the amount of creep in 10,20,30,40,50 years along with supporting calculations.The calculation to be based on every day temp. 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 CREEPAGE 3.305 X 145 mm 120 KN, 280mm /330mm/430mm CREEPAGE4.305 X 170 mm 160 KN 280mm /330mm/430mm CREEPAGE BALL 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 WORKS1. 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 WORKS CONSTRUCTION WORKS contd..contd..

3. FOUNDATIONS

i) DESIGN FOR DIFFERENT SOILS ii) EXCAVATION PLAN

iii) FORM BOXES iv) STUB SETTING

v) CONCRETING vi) REVETMENTS

vii) 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 WORKS CONSTRUCTION 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 METHODIEC-826IEC-826

CLIMATIC LOADS

a) RETURN PERIODS OF CLIMATIC EVENTS

1) 50 YEARS

2) 150 YEARS

3) 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 METHODIEC-826IEC-826

COORDINATION OF STRENGTH OF COMPONENTS--------------------------------------------------------------------------------------------------------

MAJOR COORDINATION WITH

COMPONENT MA JOR COMPONENTS

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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,

HARDWARE

CONDUCTOR 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 REQUIREMENTS LOADS DURING CONSTRUCTION AND MAINTENANCE LOADS

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METHODOLOGY FOR THE DESIGN METHODOLOGY FOR THE DESIGN OF TRANSMISSION LINESOF TRANSMISSION LINES

ESTABLISH SAFETY REQUIREMENTS

SELECT SECURITY REQUREMENTS

SELECT RELIABILITY

CALCULATE CONSTRUCTION

AND MAINTENANCE LOADS

CALCULATE LOADSRELATED TO

SECURITY

CALCULATE CLIMATIC LOADS

COMBINE ALL LIMITLOADS

CHECK SAFETY REQUIREMENTS

FROMNATIONAL

REGULATIONSCALCULATE STRENGTHNEEDED TO COMPLY

WITH ALL LOADS ANDREQUIREMENTS

DESIGN COMPONENTSFOR LOADS AND

STRENGTHREQUIREMENTS

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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 LEVEL3. CLEARACE AND SWING ANGLES4. AIR CLEARANCE5. POWER LINE CROSSINGS6. TELECOM.LINE CROSSINGS7. RAIL TRACK CROSSINGS

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DESIGN PARAMETERSDESIGN PARAMETERS

1. NO.OF CIRCUITS

2. CLIMATIC CONDITIONS

a. WIND

b. TEMPERATURE

c. 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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LOADINGS LOADINGS contd..contd..

NATURE OF LOADS

1. TRANSVERSE LOADS(T)

WIND LOAD ON TOWER STRUCTURE, CONDUCTOR, GW & INSULATOR STRING

COMPONENT OF MECHANICAL TENSION

2. 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 CONDITION BROKEN 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 MEMBERS DESIGN 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

ULTIMATE BEARING STRESS - 3552 Kgf IN 5mm TH.sECTION

ULTIMATE SHEARING STRESS - 4464 Kgf SINGLE SHEAR

i) CLASS 5.6

ULTIMATE BEARING STRESS - 5058 Kgf in 5mm th. SECTION

ULTIMATE SHEARING STRESS -- 63564464 Kgf SINGLE SHEAR

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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 AT

A. 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 DRAWING

5. 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 FOUNDATIONS DESIGN 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 FOUNDATION

g. SOFT ROCK/FISSURED ROCK FOUNDATION

h. HARD ROCK FOUNDATION

i. SANDY SOIL FOUNDATION

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DESIGN OF FOUNDATIONS DESIGN OF FOUNDATIONS contd..contd..

5. STRUCTURAL ARRANGEMENT OF FOUNDATION

a. PCC TYPE

b. RCC SPREAD TYPE

c. BLOCK TYPE

d. 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