transmission tower

Category: Education

Presentation Description

design of transmission tower, general informartion on transmission tower, types of transmission tower, tower geomentry, anatomy, foundation, stub setting,


By: kcpalo (65 month(s) ago)

Can I have the pdf / scanned copy of CBIP manual for design of transmission tower ?

By: malikimranali39 (83 month(s) ago)

i downloaqded materail but it is not opent in ppt format.. can u send me in ppt format??

Presentation Transcript



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Power in UAE..?:

Power in UAE..? Production capacity – 18.74 GW . (lack in peak seasonal times) Lack of natural gas Gulf Cooperation Council – UAE, Kuwait, Qatar, Bahrain, Saudi Arabia & Oman GCC began region-wide power grid – demand UAE has no spare power capacity Phase 3 of GCC grid to southern system of UAE In Dec’2009 $20 billion contract to Korean Electric Power – 4 nuclear reactors 1 st reactor may 2017 – each reactor 1400 MW 4 R.SARAVANAN, PGET, L&T UAE

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Electric power transmission..? The bulk transfer of electrical energy, from generating power plants to substations Power is usually transmitted through overhead power lines Underground power transmission has a significantly higher cost and greater operational limitations - urban & sensitive areas Overhead Power lines..? An electric power transmission line suspended by towers It is the lowest-cost method of transmission for large quantities of electric energy (most of insulation by air) The bare wire conductors on the line are generally made of aluminum 5 R.SARAVANAN, PGET, L&T UAE

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Transmission tower..? Tall structure u sually a Steel lattice tower , used to support an overhead power line Electricity pylon – UK & parts of Europe Ironman – Australia Hydro tower in parts of Canada 6 R.SARAVANAN, PGET, L&T UAE

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Tower Anatomy:

Tower Anatomy Peak - supports G.W Cage - b/w peak & tower body Cross Arm - Support Conductor/G.W Boom – supports power conductors (horizontal) Tower body – main portion, connects cage/boom to foundation/(leg/body )extensions 9 R.SARAVANAN, PGET, L&T UAE

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Bracings Provided for interconnecting the legs To afford desired slenderness ratio for economical tower design Framing angle b/w bracings & main leg members shall not be < 15 degree Patterns are Single web system Double web or warren system Pratt system Portal system Diamond Bracing system Multiple Bracing System 11 R.SARAVANAN, PGET, L&T UAE

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Tower Extension:

Tower Extension Body Extension Leg Extension Body Extension Used to Increase the height of tower to obtain the reqd min Ground clearance & over road crossings, river crossings, ground obstacles Body extensions upto 7.5m height in steps 2.5m can be used & thus form a part of standard tower Extensions having greater heights (25m) the suitability is checked by reducing span length and angle of deviation. Practice in tower industry is also to specify negative body extension (portion of tower body is truncated) 14 R.SARAVANAN, PGET, L&T UAE

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Leg Extension Tower Leg extensions are required when the tower was spotted in the undulated surface / Hilly terrain. While spotting the tower locations in hilly areas requires more benching or revetment or both are involved , but suitable hill side (leg extensions) can be used to minimize benching or revetment or both. Two types of Leg extension : i ) Universal leg extension ii) Individual leg extension 15 R.SARAVANAN, PGET, L&T UAE

Types of Tower:

Types of Tower No. of Circuits Single Circuit Double Circuit Multi-Circuit Deviation Angle. Ranges from 0 to 90 deg . Type of Insulator Suspension Tension/Dead end Transposition Type of Support Self Supporting Guyed Shape at the base Square Rectangle kV Rating. Ranges from 33 to 1200 kV HVDC R.SARAVANAN, PGET, L&T UAE EDRC-TL Design

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Vertical Configuration Horizontal Configuration 17 R.SARAVANAN, PGET, L&T UAE

Tension Tower:

Tension Tower Suspension Tower 18 R.SARAVANAN, PGET, L&T UAE

Guy Towers:


Conductor Configuration:

Conductor Configuration 20 R.SARAVANAN, PGET, L&T UAE

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66 kv 132 kv 220 kv 400 kv 21 R.SARAVANAN, PGET, L&T UAE

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66 kv 132 kv 220 kv 400 kv 22 R.SARAVANAN, PGET, L&T UAE

Tower Nomenclature:

Tower Nomenclature Sr. No. Nomenclature Deviation Remark 1 A/DA/ S /SLC/T0/TDL/QA/SA/V 0-2 0 Suspension Tower 2 B/DB/ AT /DLB/TD2/QB/X 0-30 0 Used Small angle tower. Used as a Section Tower 3 C/DC/ BAT /DLC/TD3/QC/CZ 30-60 Used as Medium Angle Tower Used as a Transposition 4 D/DD/ BAT /DE/TD6/TDT/QD/DE 60-90 0 /Dead End Used as a large angle Tower Used as a Dead End Tower 23 R.SARAVANAN, PGET, L&T UAE

Height of Tower Structure:

Height of Tower Structure 24 Height of tower is determine by- h 1 = Minimum permissible ground clearance h 2 = Maximum sag h 3 = Vertical spacing between conductors h 4 = Vertical clearance between earth wire and top conductor R.SARAVANAN, PGET, L&T UAE


ELECTRICAL CLEARANCES Sr. No Type of Clearance 132 kV 220 kV 400 kV 765 kV 1 Ground Clearance 6.1 m 7.0 m 8.84 m 15.5 m 2 Live Metal Clearance in mm Swing 132 / 220 400 / 765 Suspension insulator 15 15 1530 1980 3050 4400 (25°) 30 30 1370 1830 1860 1300 (55°) 45 - 1220 1675 - 60 1070 - - Tension Insulator 0 0 1530 2130 3050 Jumper 10 20 1530 2130 3050 4400 20 40 1070 1675 1860 1300 30 - 1070 - - - 3 Mid Span Clearance (m) 6.1 8.5 9.0 12.4 4 Shielding Angle ( Deg ) 30 30 20 20 5 Phase to Phase Clearance Vertical 3.9 m 4.9 m Horizontal 6.8 m 8.4 m 25 R.SARAVANAN, PGET, L&T UAE

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Right of Way : Sr. No Type of Clearance 132 kV 220 kV 400 kV 765 kV 1 ROW width 27 m 35 m 52 m 85 m 26 R.SARAVANAN, PGET, L&T UAE


DESIGN PARAMETERS Transmission Voltage Number Of Circuits Climatic Conditions Environmental and Ecological Consideration Conductor Earth Wire Insulators Span 27 R.SARAVANAN, PGET, L&T UAE

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Economic Voltage of Transmission of Power E = Transmission voltage (KV) (L-L). L = Distance of transmission line in KM KVA =Power to be transferred Standard Voltage - 66,110,132, 220, 400 KV 28 R.SARAVANAN, PGET, L&T UAE


Conductor Aluminum is used it has about half the weight of copper for the same resistance , as well as being cheaper Types: AAC : All Aluminium conductors. AAAC : All Aluminium Alloy conductors ACSR : Aluminium conductors, Steel-Reinforced ACAR : Aluminium conductor, Alloy-Reinforced Bundle conductor Bundle conductors are used to reduce corona loses & audible noise It consists of several conductors cables connected by non-conducting spacers It is used to increase the amount of current that may be carried in line As a disadvantage, the bundle conductors have higher wind loading Spacers must resist the forces due to wind, and magnetic forces during a short-circuit 29 R.SARAVANAN, PGET, L&T UAE spacers

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Earth Wire:

Earth Wire Earth wire provided above the phase conductor across the line and grounded at every tower. It shield the line conductor from direct strokes Reduces voltage stress across the insulating strings during lightning strokes Galvanized steel earth wires are used Aerial marker balls (>600mm dia) (Red, Orange, White) Shield angle 25 ° -30 ° up to 220 KV 20° for 400 KV and above 31 R.SARAVANAN, PGET, L&T UAE

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Insulators Insulator are required to support the line conductor and provide clearance from ground and structure. Insulator material- High grade Electrical Porcelain Toughened Glass Fiber Glass Type of Insulator- Disc Type Strut Type Long Rod Insulator 33 R.SARAVANAN, PGET, L&T UAE

Insulator Strings:

Insulator Strings Disc insulator are joint by their ball pins and socket in their caps to form string. No of insulator disc is decided by system voltage, switching and lighting over voltage amplitude and pollution level. Insulator string can be used either suspension or tension . Two suspension string in parallel used at railways, road and river crossing as statutory requirement. Swing of suspension string due to wind has to be taken into consider. single string Double string 34 R.SARAVANAN, PGET, L&T UAE

Design Span lengths:

Design Span lengths 1.Basic Span Most economic span Line is designed over level ground The requisite ground clearance is obtained at maximum specified temperature 35 R.SARAVANAN, PGET, L&T UAE

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2.Ruling Span Assumed design span that will produce, between dead ends It is used to calculate the horizontal component of tension (which is applied to all spans b/w anchor pts) Tower spotting on the profile is done by means of sag template, (which is based on ruling span) Ruling span = √ ( L1^3 + L2^3 +….+L6^3 / L1 + L2 + … + L6) 3.Average Span Mean span length between dead ends It is assumed that the conductor is freely suspended such that each individual span reacts to change in tension as a single average span Average span = (L1+ L2+...+L6) /6 36 R.SARAVANAN, PGET, L&T UAE

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4.Wind Span 5.Weight Span Horizontal distance between the lowest point of conductor , on the two spans adjacent to the tower The lowest point is defined as point at which the tangent to sag curve It is used in design of cross-arms Half the sum of the two spans , adjacent to support It is assumed that the conductor is freely suspended such that each individual span reacts to change in tension as a single average span Wind span = 0.5(L1 + L2) Weight span = a1 + a2 37 R.SARAVANAN, PGET, L&T UAE

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38 Determination of Base Width The base width (at the concrete level) is the distance between the centre of gravity at one corner leg and the centre of gravity of the adjacent corner leg. A particular base width which gives the minimum total cost of the tower and foundations. The ratio of base width to total tower height for most towers is generally about one-fifth to one-tenth. 38 Ryle Formula R.SARAVANAN, PGET, L&T UAE

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Determination of Weight of tower Rough approximation From knowledge of the positions of conductors & ground wire above ground level & overturning moments Ryle gives empirical formula in term of its height & maximum overturning moment at base 132 kv – 1.7 metric tones 220 kv – 2.5 metric tones 400 kv – 7.7 metric tones 765 kv – 14 metric tones Approximate values 39 R.SARAVANAN, PGET, L&T UAE


LOADINGS Loads are applied in all three directions namely Transverse ( FX ), Vertical ( FY) and Longitudinal (FZ) direction. Transverse loads consists of – Wind on Conductor Wind on Insulator Component of Wire Tension in Transverse Direction (Deviation Load) Wind on Tower Body Vertical Load consists of – Weight of Wire Weight of Insulator Weight of Line man & Tools Self Weight of Tower Longitudinal Load Consist of – Component of Unbalanced pull of the wire in the longitudinal direction. 40 R.SARAVANAN, PGET, L&T UAE

Loads on Tower:

Loads on Tower Normal Condition Broken Wire Condition 41 R.SARAVANAN, PGET, L&T UAE

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Loads are calculated as per the guide lines furnished in specification/standard. Standards for Calculation of Loads IS – 802 – 1977 IS – 802 – 1995 DIN – VDE 0210 ASCE Manual IEC – 826 The loads are calculated for following Conditions. Reliability / Working condition Security / Broken wire condition Safety / Erection & maintenance Condition 42 R.SARAVANAN, PGET, L&T UAE


ANALYSIS & DESIGN Analysis is carried out by finite element software STAAD Required FOS is provided in input file to find out ultimate force The critical compression and tension in each member group is found out Members and Connections are designed for these forces. Iterations are carried out for the optimum usage of tower. 43 R.SARAVANAN, PGET, L&T UAE

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FOUNDATION It costs 10-30 % of overall cost of tower It is the last step in designing process but precedes the construction Overload factors assumed in designs are 2.2 under Normal condition & 1.65 under broken-wire conditions Data's for foundation design 47 R.SARAVANAN, PGET, L&T UAE

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0.5 to 2m dia Shaft depth 3 to 15m Skin friction between ground & shaft resists uplift Used in usa , acceptance for wide use in India Uplift loads are resisted by undistrube material Develop uplift load of 2 to 3times that of an iidentical footing without undercut Non-cohesive soil For non-cohesive soils such as uncemented sand or gravel Provide pad footing without undercut Usually followed in INDIA at present 48 R.SARAVANAN, PGET, L&T UAE

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Adopted in firm cohesive soils Undercut on the pads Experience shows that this type of footing develop resistance to uplift 2 to 3 times that given footing without undercut Hybrid design Large uplift force are to be resisted SBC is low Augered footing with more than one bulb is used to increase the uplift capacity 35m long under reamed to 2.5 times dia of shaft Clayey black cotton soils & medium dense sandy soils 49 R.SARAVANAN, PGET, L&T UAE

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In usa , canada Steel corroded, periodic excavation & maintanence Medium dry sand, clay or sandy caly soils (no special precautions necessary) The steel is treated with one coat of bituminous paint & top coat of asphalt Suitable in areas with rock out crop Based on uplift, the anchor be single bar or group of bars welded to tower leg Vertical bars below stub angle form cage for footing Grouted to a depth of about 50 times dia into the rock Special circumstances River crossing towers & towers on embankments The raft at bottom makes the foundation substantially rigid to minimize differential settlement 50 R.SARAVANAN, PGET, L&T UAE

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Raft foundation 51 R.SARAVANAN, PGET, L&T UAE Pyramid chimney type foundation

Stub-setting :

Important steps in tower erection The stubs are set with the help of stub setting templates Excavated pits are lean concreted to correct level Stubs are placed on lean concrete pad Alignment is carried by four plumb bobs hung from centre of the horizontal bracing If any pit over excavated by mistake, the extra depth should be filled by concreting After the stub is set, the heel distance of four faces of the tower and two diagonals should be checked 52 R.SARAVANAN, PGET, L&T UAE Stub-setting

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