transmission line basic presentation
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A PresentationA Presentation
onon
Transmission line BasicsTransmission line Basics
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WHY A TRANSMISSION LINE?
Transmission lines are constructed basically for transmissionof power from one point to another
Normal connecting points
Interconnection between 2(two) generating stations
Connecting generating station with substations
Interconnection between substations
Interconnection between substation & power sub station Interconnecting power substations
Connection from power substation to consumers
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BASIC SCHEMATIC
G!"#TI$! % T"#!'II$! IT"I*+TI$!
Generator
11 KV
GT220 KV
Step down
transformer
Distribution
Power plant Transmission
systemDistribution system
11220 !V
220""11 !V
110#$ !V
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POWER SYSTEM !IA"RAM
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TRANSMISSION LINE CONCEPT
Power
Plant
Consumer Home
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POWER SYSTEM COMPONENTS
Source:
www.howstufworks.com
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CHOICE O# "ENERATION $ TRASMISSION
%OLTA"E
Generation is normally at , or 11 45
tepped up through transformer and transmitted o5er a longdistance to the desired load centers at different 5oltages which
depends on % 6uantum of power to be transmitted
% 7ine length
% Cost of terminal e8uipments % conomy consistent with desired reliability
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CON!&CTOR SELECTION SCENARIOS
cenario I : Conductor for low 5oltage lines ( , 4;< 11 4;< 33 4;)
are selected from the point of 5iew of c'rrent carr(ing capacit( cenario II : election of conductor for =; > +=; lines where
conductor si?e can not be increased beyond a certain limit in #CTransmission because of factors li4e in)'ctance *+L,- capacitance
*.$+C,- corona $ RI e//ects etc Corona > "I phenomena increasesdirectly with the diameter of conductor *undle conductor<therefore< ha5e to be used for 5oltage le5el for , 4; and beyondfrom Corona > "I consideration *undle conductor can also be used
in lower 5oltage line to increase the 8uantum of power to betransmitted
S0in e//ect of conductor in #C Transmission also limits si?e ofconductor where bundle conductor is more economical (both cost
and power loss) instead of a single large diameter conductor
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WHAT IS CORONA?
Transmissionline conductors are surrounded by an electric field
Corona discharge is generated when the electric field at the surfaceof the conductor becomes larger than the brea4down strength of thesurrounding air
urface irregularities such as sharp points and water droplets cause
local field concentration< enhancing corona generation Thus< during bad weather< corona discharge is more intense and losses are muchgreater
Corona discharge generates audible noise and 5isible lights The
5isible light and audible noise can be obser5ed simultaneously The 5oltage at which corona begins in called the discharge inception
5oltage Con5ersely< the 5oltage at which corona ceases is calleddischarge e@tinction
Corona produces radio and tele5ision interference
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CORONA !ISCHAR"E PHOTO
Corona e5ent captured by corona camera on -4; line
Corona Camera
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CORONA !ISCHAR"E %I!EO
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TRANSMISSION LINE %OLTA"E AN!
CHOICE O# CON!&CTORS
Normal Transmission1oltage
T(pe o/ con)'ctor Normall( 'se)
, 4; #C" #nt> s8uirrel
11 4; #C" Aeasel
33 4; #C" "acoon.. 4; #C" og
132 4; #C" Banther> ebra
22 4; #C" ebra> 'oose, 4; Twin #C" 'oose > *ersimis> In5ar
/.- 4; 6+# #C" *"I'I>In5ar
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TRA!E NAME O# CON!&CTORS
Trade name of conductors are normally 4ept after the names of
5arious animals< birds and insects ome of the common ones are:Code !ame
#ppro@ current carryingcapacity (#mp)
ia ofconductor
(mm)
#ppo@+T
(4g)
#ppro@weight(4g>4m),D ambient ,-D ambient
8uirrel 11- 1/ .33 /11 0-
Gopher 133 123 /0 9-2 1.
Banther -2 ,02 21 912/ 9/.
ebra /9- /3. 20.2 1331. 1.23'oose 9 03- 31// 1.2- 22
http://www.google.co.in/imgres?imgurl=http://blogs.warwick.ac.uk/images/rosalindhook/2005/06/04/panther.jpg&imgrefurl=http://blogs.warwick.ac.uk/rosalindhook/entry/grey_panther_induction/&h=331&w=482&sz=58&tbnid=usgk7XgE1EoJ::&tbnh=89&tbnw=129&prev=/images%3Fq%3Dpanther%2Bpicture&hl=en&sa=X&oi=image_result&resnum=1&ct=image&cd=1http://www.google.co.in/imgres?imgurl=http://blogs.psychologytoday.com/files/u26/zebra-picture.jpg&imgrefurl=http://blogs.psychologytoday.com/blog/lust-in-paradise/200803/america-zebra-nation&h=427&w=350&sz=19&tbnid=nI3czj1DAq0J::&tbnh=126&tbnw=103&prev=/images%3Fq%3DZebra%2Bpicture&hl=en&sa=X&oi=image_result&resnum=1&ct=image&cd=1http://www.google.co.in/imgres?imgurl=http://www.moose1899.com/Find-8-Moose222.jpg&imgrefurl=http://www.moose1899.com/about%2520our%2520website%2520logo.htm&h=354&w=300&sz=47&tbnid=akqAbbRd9rIJ::&tbnh=121&tbnw=103&prev=/images%3Fq%3DMoose%2Bpicture&hl=en&sa=X&oi=image_result&resnum=2&ct=image&cd=1http://www.google.co.in/imgres?imgurl=http://www.turtletrack.org/Issues04/Co01102004/Art/Gopher.jpg&imgrefurl=http://www.buzz.mn/%3Fq%3Dnode/2645&h=348&w=486&sz=45&tbnid=wuSZEXTWYqoJ::&tbnh=92&tbnw=129&prev=/images%3Fq%3DGopher%2Bpicture&hl=en&sa=X&oi=image_result&resnum=3&ct=image&cd=1http://www.google.co.in/imgres?imgurl=http://www.onlinebangalore.com/life/pets/images/squirrel.jpg&imgrefurl=http://www.onlinebangalore.com/life/pets/squirrel.html&h=253&w=304&sz=11&tbnid=29BUnPucCSwJ::&tbnh=97&tbnw=116&prev=/images%3Fq%3Dsquirrel%2Bpicture&hl=en&sa=X&oi=image_result&resnum=2&ct=image&cd=1
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INS&LATE! CABLE %s O%ERHEA! LINE
BARE CON!&CTOR
!ECI!IN" #ACTORS
;oltage le5el
istance
Congestion
Cost consideration
Geographical consideration
#esthetic consideration
"eliability
#5ailable Technology
pecial circumstances
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LAYIN" O# TRANSMISSION LIN2
I, Ins'late) ca3les
+nderground
$5erhead on Bylon
upported by *ridge Girder
II, Bare Con)'ctor
irect supports on Insulators
Bylon supports
Laying of Underground cable
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TYPES O# PYLONS
# B$7 (tandard length: /- m> 0- m> 9/- m> 12 m)
Aooden
teel "ail> Channel
Bretressed Concrete ( BC)
"einforced Cement ConcreteWooden Pole
Steel Tubular Pole PS Pole
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TYPES O# PYLONS
* LATTICE STEEL STR&CT&RE (Tower)
'odular welded (self supporting or guyed)
*olted ( built up & self supporting)
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MO!&LAR TOWER ERS
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TYPES O# LATTICE STR&CT&RE
#ccording to support condition
#ccording to number of circuits they carry:
#ccording to tower shapes> base dimension
E #'rt4er classi/ication
#ccording to angle of de5iation
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LATTICE STR&CT&RE CLASSI#ICATION
ACCOR!IN" TO S&PPORT CON!ITION5 elf supporting tower
Guyed tower
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ACCOR!IN" TO NO O# CIRC&IT THEY CARRY ingle circuit tower
ouble circuit tower
'ulti circuit towers
LATTICE STR&CT&RE CLASSI#ICATION
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!ETAILS O# SIN"LE CIRC&IT TOWER
Cross arm at 3 le5els Cross arm at 2 le5els
Cross arm at 1 le5el
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!O&BLE 6 M<I CIRC&IT TOWER
!OU"LE IRUIT TOWER
MULTI IRUIT TOWER
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ACCOR!IN" TO CON#I"&RATION
;ertical configuration tower
=ori?ontal configuration tower
elta configuration tower
LATTICE STR&CT&RE CLASSI#ICATION
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2.
#CC$"I!G T$ T$A" =#B> *# I'!I$!
!$T: To be chosen by designer on Techno economical consideration
LATTICE STR&CT&RE CLASSI#ICATION
WI!E "ASE! TOWER
NARROW "ASE!
%&'() *ts
%&'
+$ *ts
#$$ %& NORMAL
TOWER#$$ %& OMPAT
TOWER
400 kV Compact Single pole tower at Delhi &
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400 kV Compact Single pole tower at Delhi &
Noida
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ACCOR!IN" TO AN"LE O# !E%IATION5
*Tangent to+er$ s'spension to+er,
A type tower (2 degree)
Tension to+ers$angle to+ers:
B type tower (1- degree)
C type tower (3 degree)
(#lso used for transposition)
! type tower (. degree)
LATTICE STR&CT&RE CLASSI#ICATION
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TRANSPOSITION TOWER
W4at is transposition to+er an) its con/ig'ration? Transposition tower is normally parallel double circuit
transmission tower to facilitate interchange of transmissionline phase conductor< where the phase conductors occupydifferent structure positions for different portions of the line
length so that transmissionline impedances is balancedFor e@ample< conductor placement on the structures may be"* for onethird of the line length< *" for onethirdof the line length< and *" for the remaining third of theline length
Ctype tower with modified crossarm is generally usedwith ?ero degree de5iation
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WHY TRANSPOSITION?
Bower transmission lines are transposed primarily forimpedance balance so as to eliminate or reducedisturbances in the neighboring communicationcircuits produced by geometric imbalances of power
line Transposition tower are re8uired for a line length
H 2 4ms why
#rrangement of transposition tower is shown below
LINE TRANSPOSITION
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LINE TRANSPOSITION
WITH 7C8 TYPE TOWER
R
'
"
R
'
"
R
'
"
R
'
"
T( T)T*
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SIN"LE %s B&N!LE CON!&CTOR
ingle Conductor : !ormal +se
*undle Conductors:
eciding Factors
Capacity nhancement
Technical reasons ( =andling & rection easiness< Corona> "adioInterference ( "I) consideration
*undle conductor Configuration
Twin *undle
6uad *undle
pecial Burpose *undle (=e@agonal> $ctagonal etc)
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TOWER SI9ES
TOWER HEI"HT IS !ECI!E! BASE! ON
pan : 7onger the span< more is the height 'inimum Ground clearance (#) re8uired to be
maintained
Conductor sag (*) Insulator assembly length (C) to maintain
re8uired electrical
;ertical separation of Cross arms ()
!umber of cross arm and its configuration
Bea4 =eight for fi@ing earth wirecorresponding to shield angle ()
A
"
!
E
!
S+ield angle
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3,
WHY EARTH WIRE?
To protect conductor against lightning flasho5ers
To pro5ide a path for fault current
!irect #las4o1er
$ccurs due to shielding failure with lightning on the conductor<flasho5er ta4ing place across the insulator string from conductorto ground
Bac0 #las4o1er
$ccurs due to high tower footing resistance with a high 5oltage atthe grounded tower cross arm compared to conductor< resulting ina flasho5er across the insulator string from ground to conductor
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3-
WHY EARTH WIRE?
'a@imum allowable fault current (I) through earth wire mainlydepends on
#rea of earth wire (#)
'a@imum permissible temperatureTime of short circuit (t)
I 5aries proportional to # and in5erse proportion to s8rt (t)
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3.
SHIEL! AN"LE
arth wire is placed on top of the structure to
pro5ide a shied angle for protection againstlightning o5er power conductors< therecommended angle being 3 degree with the5ertical in case of 5ertical formation of powerconductors
7ocation where iso4eraunic le5els are high< lowerangle of shielding may be adopted
#s cross arm width increases< hori?ontal spacing
of conductor increases To protect the conductorswith specified shield angle< earth wire has to be
placed at a higher ele5ation in such cases Toreduce the tower pea4 height< double pea4 with
double earth wire are used in those cases
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STAN!AR! NORMAL SPAN
#OR %ARIO&S %OLTA"E CLASSES
%OLTA"E SPAN RAN"E *METERS,
11 4; /-1
33 4; 103- ( 913- o5er poles)
.. 4; 2,32
132 4; 3-3.-
22 4; 3230
, 4; 3- ,-
/.- 4; ,,-
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MINIM&M "RO&N! CLEARANCE
%OLTA"E MINIM&M "RO&N! CLEARANCE
IN METERS *IS :;.
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NO O# CROSS ARMS
AN! ITS CON#I"&RATION
3 for single circuit line
. for double circuit line
12 or more for multi circuit lines
Cross arms can be of =ori?ontal > ;ertical or Triangularconfiguration
MINIM&M PHASE TO PHASE
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MINIM&M PHASE TO PHASE
ELECTRICAL CLEARANCE
%OLTA"E MINIM&M PHASE CLEARANCE*APP=, MM * IS :;.
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WHAT IS "ALLOPIN"?
"alloping *)ancing o/ con)'ctor, is ;ery low fre8uency< high
amplitude 1i3rations induced by: =igh 5elocity steady winds on conductors with asymmetrical
ice deposit
Ahen ice on a portion of ice co5ered conductor melts and
suddenly drops off Ahen a floc4 of birds perching together on a conductor
suddenly ta4es off< lea5ing the conductor Jumping in loops
Ot4er +in) in)'ce) 1i3rations are5
#eolian 5ibrations : =igh fre8uency< low amplitude 5ibrationsinduced by low< steady & laminar wind
Aa4e induced 5ibrations: 7ow fre8uency< medium amplitude5ibrations induced by high 5elocity steady winds on bundleconductors
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CON!&CTOR SA"
Conductor sag depends on
Type of conductor
pan length
Aeight of conductor
Conductor tension Sag 7SK L A72 > 0T
A L conductor weight per meter
7L span length ( tower spacing)TL Conductor Tension
!e1elope) Lengt4 7!KL 7M A2 73
2,T2
L, -.an
S ,
- a g
!
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INS&LATOR ASSEMBLY LEN"TH
%oltage Appro>imate Stan)ar) ins'lator assem3l(lengt4- single s'spension string
11 4; 2 mm
33 4; -- mm.. 4; 9.-mm
132 4; 1.3 mm
22 4; 23, mm, 4; 3/, mm
/.- 4; -- mm
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MINIM&M TOWER HEI"HT
MINIM&M TOWER HEI"HT IS "O%ERNE! BY
Minim'm gro'n) clearance *A,
Ma>im'm sag *B,
Ins'lator assem3l( lengt4 * C,
*/or s'spension to+er onl(,
Cross arm spacing
*1ertical con)'ctor separation, * !,
Eart4 +ire pea0 )istance /rom top most
cross arm point * E,
A
"
!
E
!
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CROSS ARM SI9E *WI!TH,
%oltage Minim'm Bo)(clearance * mm,
11 4;
33 4; 33
.. 4; .1
132 4; 1/
22 4; 1./-, 4; 10.
/.- 4;
'inimum electrical clearance of conductor> Jumper from Tower body
(I -.13)
LOA!S ON TOWER
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LOA!S ON TOWER
;"TIC#7 7$# ead weight of Tower ead weight of conductor & arth wire 7i5e weight of wor4ing personal<
hoisting tools & tac4les etc now loading (where5er applicable)
Transient loads =$"I$!T#7 7$#For the purpose of con5enience weconsider all hori?ontal loads in two perpendicular a@es
$ne in Trans5erse direction wrt crossarm $ne in longitudinal direction wrt cross
arm
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ORIENTATION O# TOWER +@r@t CROSS ARM
Su-.en-ion to/er .o-ition-
Line align0ent
Line align0ent
ro-- ar0 orientation 1.lan2
# uspension Tower Longitudinal direction
Longitudinal direction
T r a n - 3
e r - e
d i r e c t i o n
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ORIENTATION O# TOWER +@r@t CROSS ARM
* #ngle Tower
Angle of
de3iation
Angle of
de3iation
"i-ector
Angle To/er Po-ition-
ro-- Ar0 Orientation of Angle to/er 1.lan2
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TRANS%ERSE LOA! ON TOWER
$n account of wind pressure on tower body
$n account of wind pressure on conductor< earth wire &insulator string
$n account of conductor > earth wire pull
Wind load on to/er , wind
pressure 4 .ro5ected area
Wind load on conductor6eart+
/ire , wind pressure 4
.ro5ected area
onductor
TRANS%ERSE LOA! ON TOWER ON A$c O#
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TRANS%ERSE LOA! ON TOWER ON A$c O#
CON!&CTOR $ EARTHWIRE P&LL
7 , angle of !e3iation
T-in 86*
*Tco- 86*
T-in 86*
T
T
T
T
8 , (#$9 : ;
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LON"IT&!INAL LOA! ON TOWER ON ACCO&NT
O# CON!&CTOR$ EARTHWIRE P&LL
Longitudinal direction
Tran-3er-e direction
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LON"IT&!INAL LOA! ON TOWER
# $n account of conductor > arth wire pull
In normal case< 7ongitudinal load due to conductor pull canceleach other e@cept for bro4en wire condition (*AC) where therewill be imbalanced pull on the cross arm
# ! T$A" which are used for termination of a line atswitch yard end are subJected to se5ere pull by conductor whichare strung on one side only
* $n account of unbalanced Tension of conductor > earth wire ontwo sides of towers which may happen due to error during final
tensioning & temperature 5ariation which may cause unbalancetension due to linear e@pansion> contraction when section lengthon either side of the tower are different
C +nder *ro4en wire condition (*AC)
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!ead End To/er
S/itc+ yard gantry
onnection to S/itc+ yard gantry i-done at a later -tage and /it+ -lac%
-.an only
LON"IT&!INAL LOA! ON TOWER
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CONCEPT O# WEI"HT SPAN
Ahat is weight span
It is the span length (length of conductor or earth wire)which contribute to the 5ertical load on tower
Weig+t -.an Weig+t -.an
Weig+t -.an
1left2
Weig+t -.an
1rig+t2
W( W*
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--
WHY NE"ATI%E WEI"HT SPAN OCC&RS ?
$n steeply inclined spans< the low point of sag may fall beyond the
lower support This indicates that the conductor in the uphill span ise@erting a negati5e or upward force on the lower tower The amountof this upward force is e8ual to the weight of the conductor from thelower tower to t4e lo+ point in t4e sag@ I/ 'p+ar) pull of the uphillspan is greater t4an t4e )o+n+ar) loa) o/ t4e ne@t adJacent span<
actual uplift will 3e ca'se)
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-.
NE"ATI%E WEI"HT SPAN
R"
L"
1:2R A
L A
A
"
Total weight span of tower # L 7# % " #
Total weight span of tower * L 7* M " *
THEORETICAL #ORM&LA #OR CALC&LATION
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O# WEI"HT SPAN BETWEEN TOWERS AT
!I##ERENT ELE%ATION
!i-tance of Null .oint or Lo/ .oint of conductor fro0 t+e center of -.an
i- gi3en by t+e for0ula
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-0
THEORETICAL CONCEPT O# O#
NE"ATI%E WEI"HT SPAN
L*
L(
T*
T(
;*
;(
;*
T*
T
/L(
T(
T*
T,T*OS;* , T( co- ;(
T*SIN ;* , /L*
T* OS ;( , T(OS ;(
T*SIN ;*@/L(,T(SIN ;(
/1L(@L*2,T(SIN ;(
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SI"NI#ICANCE O# NE"ATI%E WEI"HT SPAN
!egati5e weight span will mean that conductor> earth wire in
such a location will produce a 5ertically upward load instead of5ertically down in normal cases
;ertically upward load L () weight span @ weight per unitlength of conductor> earth wire
E##ECT O# NE"ATI%E WEI"HT SPAN
ffect of negati5e weight span is that suspension tower can not be used at location with negati5e weight span as it will lift up
the suspension insulators #ngle towers are therefore< to beused for such locations e5en if angle of de5iation is ?ero
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CONCEPT O# WIN! SPAN
WHAT IS WIN! SPAN?
It is the span length ( length of conductor & arth wire) which contributeto the trans5erse hori?ontal load on the tower
B( B*
Wind -.an , 1 B( @ B*2 6 *
Wind load on conductor6 Eart+ /ire , /ind .re--ure 4 .ro5ected area
TOWER SPOTTIN"
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TOWER SPOTTIN"
Tower spotting is the process of choosing right type of Tower
along the line routeTB I!;$7;
Choosing Techno economical line route
Fi@ing of #ngle ( de5iation point) to a5oid> minimi?e obstaclesenroute
Ta4ing le5els at intermediate points for drawing of profile between #ngle points ( igital instruments li4e total stations arenow a days used)
rawing of Brofile ( lectronic soft wares are now a days usedusing data from digital instruments
TOWER SPOTTIN"
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.2
Tower spotting is done either manually using sag templatecur5es or through electronic soft ware li4e B7C#
To/er -.otting on .rofile
TOWER SPOTTIN"
SA" TEMPLATE C&R%E
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SA" TEMPLATE C&R%E
Conductor & arth wire when strung between towers normally
ta4es shape of a catenary cur5e Catenary cur5es of conductordrawn at the wor4ing tension forms the sag template cur5e
Blastic sagtemplates are made for the purpose of manualtower spotting and also for random chec4ing of spotting done
through electronic soft ware
TOWER SPOTTIN" !ATA
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TOWER SPOTTIN" !ATA
$nce the technical parameters li4e angle of de5iation< weight
span< wind span etc are tabulated< the ne@t step is to choose thecorrect type of towers at 5arious locations after comparing thefield parameters with the design parameters In case of hilllyterrains< towers with 'ne'al leg e>tension are also used This
is mainly adopted to reduce benching wor4 in a particularlocation The design parameters are contained in a documentcalled Tower spotting ata
&NE&AL LE" E=TENSIONS
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&NE&AL LE" E=TENSIONS
Leg 1 @ CD 0tr E4tn2
Leg ! 1 @ 0tr E4tn2
1"2 !V Badarpur K-lie-riat /ine
/oc# o# 1 /3 4"5 "5 "5 +6
1 @ 0tr E4tn2
1 @ ) 0tr E4tn2
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SAMPLE TOWER SPOTTIN" !ATA
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SAMPLE TOWER SPOTTIN" !ATA
SAMPLE TOWER SPOTTIN" !ATA
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SAMPLE TOWER SPOTTIN" !ATA
TOWER SCHE!&LE
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TOWER SCHE!&LE
Loc
No
Angle o/
!e1iation
Weig4t Span Win) Span Recommen)e)
to+er t(peLe/t Rig4t Total Le/t Rig4t Total
"ENERAL I!EA ON WIN! PRESS&RE
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"ENERAL I!EA ON WIN! PRESS&RE
Aind pressure is proportional to wind 5elocity
Aind pressure ?onesIndia is di5ided in . ( i@) wind ?ones based on wind speed
;b is based on pea4 gust 5elocity a5eraged o5er a short timeinter5al of about 3 ( Three) seconds
!ote: Aind as per I 02 and Aind ?one as per I 0/-
Aind one *asic wind speed (;b) m>sec
1 33
2 393 ,,
, ,/
- -
. --
WIN! 9ONES O# IN!IA
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/1
WIN! 9ONES O# IN!IA
WIN! 9ONES 6 BASIC WIN! SPEE!S O# NER
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/2
WIN! 9ONES 6 BASIC WIN! SPEE!S O# NER
Name o/ states Win) Done Basic +in) spee) * %3,m$sec
#ssam .>->,>2 -->->,/>39
'eghalaya .>->, -->->,/
#runachal Bradesh ->3 ->,,
!agaland ,>3 ,/>,,
'anipur .>->3 -->->,,
'i?oram . --
Tripura . --
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WIN! 9ONE MI9ORAM
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WIN! 9ONE MI9ORAM
WIN! 9ONE MANIP&R
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WIN! 9ONE MANIP&R
WIN! 9ONE ME"HALAYA
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WIN! 9ONE ME"HALAYA
WIN! 9ONE AR&NACHAL PRA!ESH
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WIN! 9ONE AR&NACHAL PRA!ESH
WIN! 9ONE TRIP&RA
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/0
WIN! 9ONE TRIP&RA
WIN! SPEE!
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/9
WIN! SPEE!
METEOROLO"ICAL RE#ERENCE WIN! SPEE! * %R ,
;" is e@treme 5alue of wind speed o5er an a5eraging period of 1( ten) minutes duration
;" L ; b> N
N is ta4en as 13/- to con5ert 3 seconds pea4 gust speed in to 1minutes a5erage
!ESI"N WIN! SPEE! * %),
;d L ;" @ N 1 @ N 2
N 1L "is4 coefficient
N 2 L Terrain "oughness coefficient
SELECTION TABLE #OR 2
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0
SELECTION TABLE #OR 2 .
Aind ones1 2 3 , - .
"eliability 7e5el
7e5el 1 (up to , 4;) 1 1 1 1 1 1
7e5el 2 (abo5e , 4;)Mtriple & 6uad c4t up to ,
4;
10 11 111 112 113 11,
7e5el 3 (Tall "i5er crossing& special tower)
11/ 122 12- 12/ 120 13
SELECTION TABLE #OR 2
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Terrain Categor( %al'e o/ 2
Cat .5 @posed terrain with few or no obstructionswith a5erage height of obJects less than 1- m li4eopen sea coast> water stretch< deserts< flat tree lessterrain
10
Cat 5 $pen terrain with well scattered obstructionsha5ing height between 1-m to 1 m li4e normalcountry with 5ery few obstacles
1
Cat < 5 Terrain with numerous closely spaced
obstructions li4e built up & forest area
0-
Note? For line- encountering ill-6 ridge-> K* -+ould be ta%en a- ne4t
+ig+er 3alue
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%AL&E O# !RA" COE##ICIENT C)t
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#OR TOWER
Soli)it( Ratio !rag Coe//icient C)
+p to - 3.
1 3,2 29
3 2-
, 22
- and abo5e 2
SOLI!ITY RATIO
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0-
SOLI!ITY RATIO
olidity ratio L Brotected area of all members
#rea of frame
!$T: rag coefficient ta4es in to account the shielding effects ofwind on the leeward face but if leeward members are not shielded
by the windward face< proJected area of the leeward members shallalso be considered in the calculation
%AL&ES O# "&ST RESPONSE #ACTOR #OR
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TOWER * "T, AN! INS&LATOR * "I,
WIN! LOA! ON CON!&CTOR
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6 "RO&N! WIRE
Fwc
L Bd @ Cdc
@ 7 @ d @ Gc
Bd L esign wind pressure in !>m2
Cdc L rag coefficient (1 for conductor and 12 for ground wire> earth wire)
7 L Aind span L =alf of sum of adJacent span
d L iameter of conductor> arth wire in meter
Gc
L Gust response factor
%AL&ES O# "&ST RESPONSE #ACTOR "C
#OR CON!&CTOR 6 EARTH WIRE
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#OR CON!&CTOR 6 EARTH WIRE
WIN! LOA! ON INS&LATOR STRIN"
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09
WIN! LOA! ON INS&LATOR STRIN"
Fwi
L Bd @ Cdi
@ #i @ GiBd L esign wind pressure in !>m2
Cdi L rag coefficient to be ta4en as 12
#i L - Q proJected area of insulator stringGi L Gust response factor
!ote: !o mas4ing effect will be considered in case of multiple >; insulator strings
TENSION LIMIT O# CON!&CTOR 6 E$WIRE
* R / IS FG P t I$S I .:,
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* Re/5 IS FG Part I$Sec I- .:,
Conductor >arth wire tension at e5eryday temperature and withoute@ternal load< should not e@ceed the following:
Condition I
Initial unloaded tension : 3- Q of ultimate tension strength ( +T)Final unloaded tension: 2-Q of +T ( for 5oltage le5el upto 22 4;)
22Q for conductor & 2 Q for arth wire
( for , & 0 4; le5el)
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#ORM&LA #OR CALC&LATIN" CHAN"E IN
TENSION O# CON!&CTOR$ E$WIRE !&E TO
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TENSION O# CON!&CTOR$ E$WIRE !&E TO
CHAN"E IN TEMP 6 PRESS&RE *RE#5 IS :;< PART I,
T22
S T2 % (T1 l2
w2
812
U)> 2,T12
VtUWX L l2
w2
822
U > 2,where
T2 L Tension at temp t2 R C in 4g
T1 L Tension at temp t1 R C in 4g
l L pan length in meter AL Aeight per meter
81 L Y( w2 Mw12 )>w w1 L wind load in 4g> m
ZL #
L oung modulus in 4g> cm2#L Cross section area ( m2)
V L Coefficient of linier e@pansion per RC
62 L loading factor
t L (t2 % t1) R C
SA" TENSION CHART
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SA" TENSION CHART
Aith change in ambient temperature< tension on conductor and
earth wire shall also change in the following pattern because ofthermal e@pansion> contraction in the following manner
Temperature increases : Tension decreases
Temperature decreases : Tension increases It is therefore important that correct tensions are maintained
during stringing of conductor > earth wire corresponding toambient temperature so that design tension and sags are
maintained during worst loading conditions as alreadye@plained earlier
SA" TENSION CHART
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For this purpose< tension and sags at different ambient
temperatures are calculated corresponding to base wor4ingtension at e5ery day temperature and with no wind & usingformula already discussed earlier
The results are than tabulated in a con5enient way for reference
SA" TENSION CHART
SA" TENSION CHART
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9-
SA" TENSION CHART
METHO! O# MAINTAININ" CORRECT
TENSION AT THE TIME O# STRIN"IN"
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9.
TENSION AT THE TIME O# STRIN"IN"
*y measuring sag
*y measuring tension
TB
tepI : 'easure ambient temp
tep II: Calculate a5erage ruling span of the section using thefollowing formula
tep III : Consult ag Tension chart and note sag and tension5alue corresponding to ambient temp and corresponding
to a5erage ruling spantep I; : elect the span whose length is nearest to the ruling span
& adJust sag or tension so as to attain the re8uired 5alue before final tensioning (clamping on tower)
TOWER LOA!IN" CON!ITIONS
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7oadings shall be determined for the Two loading conditions
Combination I : Corresponding to ma@imum wind at meanannual temperature
Combination II : Corresponding to 2>3 rd ma@imum wind at
the minimum temperature
TOWER LOA!IN" TRANS%ERSE LOA!S
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90
WIN! LOA!S NORMAL CON!ITION BRO2EN WIRE CON!ITION
$n conductors andground wires onfull proJected areas
Corresponding to full windspan of bundledconductors & ground wire
Corresponding to -Q of intactspan and 1Q of bro4en span of bundled conductor> ground wire
$n Tower $n 1- times the proJected
areas of members on thewindward face of towers
$n 1- times the proJected areas
of members on the windwardface of towers
$n insulator strings1) uspension
2) Tension
1 4g
3 4g
1 4g
3 4g
TOWER LOA!IN" TRANS%ERSE LOA!S
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!E%IATION
LOA!S
NORMAL
CON!ITIONS
BRO2EN WIRE
CON!ITIONS
Trans5erse componentstension of bundledconductors and groundwire
a) uspension tower Trans5erse components
corresponding to -Q ofthe tension of bundled
conductors or 1Q of thetension of ground wire
b) Tension tower
Trans5erse componentcorresponding to 1Q ofthe tension of bundledconductor> ground wire
TOWER LOA!IN" %ERTICAL LOA!S
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1
!&E TO
CON!&CTOR
NORMAL
CON!ITIONS
BRO2EN WIRE
CON!ITIONS
uspensiontower
8ual to the ma@imum>minimum weight span of bundled conductors
.Q of ma@imum>minimum weight span of bundled conductors
Tension Tower 8ual to ma@imum weightspan of bundledconductors ( downward orupward)
.Q of ma@imum weightspan of bundledconductors ( downward orupward)
TOWER LOA!IN" %ERTICAL LOA!S
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!&E TO"RO&N! WIRE
NORMALCON!ITIONS
BRO2EN WIRECON!ITIONS
uspension tower 8ual to the ma@imum>minimum weight span ofGround wire
.Q of ma@imum>minimum weight span ofGround wire
Tension Tower 8ual to ma@imumweight span of Groundwire ( downward orupward)
.Q of ma@imum weightspan of Ground wire( downward or upward)
ue to Insulator &conductor#ccessories
8ual to the weight ofInsulator strings< spacers<dampers etc
8ual to the weight of Insulatorstrings< spacers< dampers etc
TOWER LOA!IN" LON"IT&!INAL LOA!S
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!&E TO POWER
CON!&CTOR
NORMAL
CON!ITIONS
BRO2EN WIRE CON!ITIONS
uspension Towers !I7 - Q of the tension of bundledconductors
Tension Towers 8ual to the tension of bundled power
conductors for deadend towers only
8ual to the components of tensionof the bundled power conductors
corresponding to the rele5ant anglesof de5iation
ue to Groundwire
!ormal conditions *ro4en wire conditions
uspension Towers !I7 8ual to the tension of Ground wire
Tension Towers 8ual to the tension ofGround wire fordeadend towers only
8ual to the components of tensionof the Ground wire corresponding tothe rele5ant angles of de5iation
TOWER LOA!IN" ERECTION LOA!S
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NORMALCON!ITIONS
BRO2EN WIRECON!ITIONS
'an with Tools !I7 8ual to the tension ofGround wire
7oads due to liftingtac4les< line car etc(to be considered atconductor cross armand lifting points)
8ual to thetension ofGround wire fordeadend towersonly
8ual to the componentsof tension of the Groundwire corresponding tothe rele5ant angles ofde5iation
!ote: The design of towers shall be based on loading combinationand condition which is more stringent for the particular member
#O&N!ATION LOA!IN"S
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1,
Calculated from Tower 7oadings
Typical Tower 7oading tree is indicated below
#O&N!ATION LOA!IN"S
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1-
7oads transmitted to Foundation through tower legs
Two types of loads act on foundation
# ;"TIC#7 ( M )* =ori?ontal or side thrust
&N!ER %ERTICAL LOA!
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1.
&N!ER HORI9ONTAL LOA!
A@ O%ERT&RNIN"
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O%ERT&RNIN"
&N!ER HORI9ONTAL LOA!B@ SLI!IN"
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SLI!IN"
%ERTICAL LOA! ON #O&N!ATION
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&L/ &LM&L/&LM
FSTFST
L
WIN!
FORE
LOA! ON #O&N!ATION
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On acco'nt o/ gra1it( /orce *+eig4t, on to+er
If A L Total gra5ity force ( weight)
Then 5ertical load (;7) on account of A on each leg<
;7w L A>, which acts downward (down thrust)
On acco'nt HoriDontal /orces *trans1erse $ longit')inal , on to+er
Ahich produces turning moment at the base of tower
!et 'oment 'T L [ F= @ h
Ahere F= L =ori?ontal force at a particular height
h L corresponding height from foundation top
LOA! ON #O&N!ATION
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@ternal 'oment ' produces restoring moment in the form of upward &downward thrust at leg> foundation
"estoring 'oment
'" L 2(upward> downward thrust in each leg @ leg to leg dist)
ie '" L 2 ;7' @ 7
For stability: !et turning moment L !et "estoring moment
ie 'T L '" \ ie 'T L 2;7' @ 7 \ ie ;7' L 'T>27
!et down thrust on 2 legs on one side L M( ;7A M ;7')
!et upward thrust on 2 legs on other side L ( ;7' % ;7A) !ormally ;7' HH;7A and therefore there is net upward thrust on 2 legs
of a tower which also acts on the foundation and this is called uplift onfoundation
#O&N!ATION LOA!IN" WIN! 9ONEII *
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* ,
#OR GG 2% !$C TOWER WITH TWIN MOOSE CON!&CTOR
TOWER TYPE COMPRESSION*2g,
&PLI#T *2g, SI!E THR&ST*TRANS, *2g,
SI!E THR&ST*LON", *2g,
# M -9 -3
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B@ HORI9ONTAL LOA! ON #O&N!ATION
=ori?ontal forces on tower also produces side thrust onfoundation
ide Thrust F&T L [ F= > ,
arth8ua4e forces
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TOWER #O&N!ATION
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c) # footing with an under cut generally de5elops uplift
resistance of two to three times that of an identical footingwithout undercut +ndercut foundations are normally
pro5ided in fissured & soft roc4 foundations
TOWER #O&N!ATION
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11/
Failure .lane Soil S+ear Stre--
Undercut
Foundation
F$+!#TI$! TB
TOWER #O&N!ATION
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110
F$+!#TI$! TB
BROA! CLASSI#ICATION :
$pen Cast % 'ost commonly used
#ugured under reamed pile (where open e@ca5ation is Broblematic)
Bile foundation
Aell foundation $n pecial 7ocations: "i5er *ed< !earby ri5er< prone to erosion< Aea4 soil
OPEN CAST #O&N!ATION
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A&"&RE! &N!ER REAME! PILE
#O&N!ATION
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PILE #O&N!ATION
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WELL #O&N!ATION
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PILE #O&N!ATION
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PILE #O&N!ATION CONSTR&CTION
LI#TIN" O# CA"E
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P7/3 8&9DAT7& &ST%9T7&
/owerin, of reinforcement ca,e in pile bore
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12-
, , p
P7/3 8&9DAT7& &ST%9T7&
/owerin, of reinforcement ca,e in pile bore
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12.
, , p
P7/3 8&9DAT7& &ST%9T7&
7nstalled pile
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http://us.f347.mail.yahoo.com/ym/ShowLetter?box=Inbox&MsgId=7316_5371269_958_2182_4736217_0_145619_6254142_4149395225&bodyPart=2&tnef=&YY=76524&y5beta=yes&y5beta=yes&order=down&sort=date&pos=1&view=a&head=b&VScan=1&Idx=29http://us.f347.mail.yahoo.com/ym/ShowLetter?box=Inbox&MsgId=7316_5371269_958_2182_4736217_0_145619_6254142_4149395225&bodyPart=2&tnef=&YY=76524&y5beta=yes&y5beta=yes&order=down&sort=date&pos=1&view=a&head=b&VScan=1&Idx=29
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P7/3 8&9DAT7& &ST%9T7&
3rected tower on pile foundation
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WELL #O&N!ATION
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13WELL FOUN!ATION
WELL #O&N!ATION &N!ER CONSTR&CTION
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OPEN CAST #O&N!ATION
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'ost commonly used< Con5enient & 8uic4 in e@ecution wherethere is no high water table and soil collapse problem
COMMON TYPE O# OPEN CAST #O&N!ATION:
!epen)ing on t(pe o/ materials 'se)
teel Grillage Type foundation
BCC > "CC foundation !epen)ing on e>tent o/ e>ca1ation
Indi5idual footing
Chimney % frustrum type
Chimney % Bad type
*loc4 type
pread type footing
STEEL "RILLA"E TYPE #O&N!ATION
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PCC $ RCC #O&N!ATION
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CHIMNEY PA! TYPE #O&N!ATION
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BLOC2 TYPE #O&N!ATION
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SPREA! TYPE #O&N!ATION
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OPEN CAST #O&N!ATION *Cont)@,
!epen)ing on t(pe o/ soil
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!epen)ing on t(pe o/ soil
!ormal dry soil foundation ry fissured roc4 (with under cut) "oc4 Foundation (#nchored) *lac4 Cotton soil foundation< commonly 4nown as Aet
*lac4 Cotton (A*C) type !epen)ing on )ept4 o/ +ater ta3le
ry Foundation: Aater table below footing depth Aet Foundation: Aater table 1- ' from ground surface
Bartially ubmerged (B): Aater table between 1- to /- mfrom ground surface
Fully ubmerged (F): Aater table abo5e /- m
WHY CLASSI#ICATION
BASE! ON WATER TABLE?
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Aeight of soil and concrete is less when submerged in water because of buoyancy effect and therefore offers lessresistance to uplift then in dry condition
#ngle of internal friction (]) is less for wet soil and
therefore 5olume of frustum of soil abo5e footing pad is lessin wet condition & therefore offers less resistance to uplift
conomy in cost is therefore achie5ed in classifyingfoundations based on water table instead of adopting one
type considering worst condition (F type)
#O&N!ATION %OL&ME
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1,
Comparison of foundation 5olume for different fdn classification:
!ame of 7ine : , 4; >C 'isa *alipara
TOWERTYPE
CONCRETE %OL&ME *C&M,
!RY WET P@S #@S
# 9.0 133 12.9 1-/,
* 2,9, 20-1 3,99 ,29
C 2/0. ,3-31 -3,9 .3.2
3,-. -219 -03- 1330,
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T=#!N $+