Transmission Line Design & Construction

WELCOME

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TRANSMISSION LINES DESIGN AND CONSTRUCTION

BY K.VEERABHADRA RAO RETD.CHIEF ENGINEER,AP TRANSCO 2

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 LUDWIGSBURGHOHENECH 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 4

MAIN 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 5

MAIN COMPONENTS

contd..

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 c) BIRD GAURDS e) STEP BOLTS

b) DANGER BOARDS d) ANTI CLIMBING DEVICES

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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 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 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 INSULATORS 1. PORCELAIN DISC INSULATORS,LONG ROD INSULATORS 2.TOUGHENED GLASS 3.POLYMER SILICON RUBBER/ALLOY OF SILICON RUBBER AND EPDM NORMAL SIZES

1.254 X 145 mm 70KN/90KN EMS. 280mm CREEPAGE 2.280 X 170 mm 120 KN/160KN, 280mm/330mm/430mm CREEPAGE 3.305 X 145 mm 120 KN, 280mm /330mm/430mm CREEPAGE 4.305 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 WORKS 1. SURVEYS a) ROUTE ALIGNMENT b) DETAILED 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 iii) RIVER CROSSINGS

c) CHECK SURVEY

ii) TELECOM LINES iv) AIR PORT AUTHORITIES 14

CONSTRUCTION WORKS

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 MEMBERS iii) TREATMENT OF JOINS iv) ASSEMBLY v) TIGHTENING AND PUNCHING OF BOLTS AND NUTS vi) FIXING ACCESSORIES

OUT

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CONSTRUCTION WORKS

contd..

5. INSULATOR HOISTING 6. POWER AND EARTH CONDUCTOR ERRECTION i) DELIVERY OF CONDUCTOR AT SITE iii) TENSIONING AND SAGGING

ii) PAYING OUT AND STRINGING 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 COMPONENTS 1. TOWERS AND ACCESSORIES 2. ACSR CONDUCTOR AND ACCESSORIES 3. EARTH WIRE AND ACCESSORIES 4. INSULATOR AND STRINGS 5. FOUNDATIONS 6. ERRECTION 7. CENTAGES

28% 36% 01% 06% 04% 14% 11%

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DESIGN BY PROBABILISTIC METHOD IEC-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 18

DESIGN BY PROBABILISTIC METHOD IEC-826 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, HARDWARE CONDUCTOR CONDUCTORS, INSULLATORS, HARDWARE ✔

NOTE: WITH IN EACH MAJOR COMPONENTS THE UNDERLINED COMPONENT IS THE WEAKEST WITH 90% CONFIDENCE

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LOADINGS 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 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 OF TRANSMISSION LINES ESTABLISH SAFETY REQUIREMENTS

CALCULATE CONSTRUCTION AND MAINTENANCE LOADS

SELECT SECURITY REQUREMENTS

CALCULATE LOADS RELATED TO SECURITY

SELECT RELIABILITY

CALCULATE CLIMATIC LOADS

COMBINE ALL LIMIT LOADS

CALCULATE STRENGTH NEEDED TO COMPLY WITH ALL LOADS AND REQUIREMENTS

DESIGN COMPONENTS FOR LOADS AND STRENGTH REQUIREMENTS

CHECK SAFETY REQUIREMENTS FROM NATIONAL REGULATIONS

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TOWER OUTLINE 1. TOWER HEIGHT 2. TOWER WIDTH 3. CROSS ARM WIDTH

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ELECTRICAL 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 PARAMETERS 1. NO.OF CIRCUITS 2. CLIMATIC CONDITIONS a. WIND b. TEMPERATURE c. ISOKERANIC LEVEL d. SEISMIC INTENSITY e. ICE FORMATION

3. 4. 5. 6. 7.

ENVIRONMENT AND ECOLOGICAL CONSIDERATIONS CONDUCTOR EARTH WIRE INSULATOR STRINGS SPAN

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LOADINGS 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

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 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 (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. 29

DESIGN 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 WIDTH 16MM

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

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 FOR16mmDIA BOLTS

i) CLASS 4.6 ULTIMATE BEARING STRESS - 3552 Kgf IN5mmTH.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 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 32

APPLICATION 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 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 34

DESIGN 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

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 36

DESIGN OF FOUNDATIONS

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

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