PROJECT:-765KV S/C RAIGARH-CHAMPA
SAFETY ASPECTS OF CONDUCTOR
METHODS ADOPTED FOR CONDUCTOR INSTALLATIONS IN 765 KV T/L
a)Mechanized Paying out of conductors and installation
TYPE OF RISK ASSOCIATED:
a)Fall of workmen from height
b)Fall of objects from height, on workers and co-passers –
c)Collapse of towers, conductors and hardware
Fittings on workers and passers –by
d)Electrocution due to contact of person /
Conductors with live wires
e)Hit by Vehicles (Workmen and co passers-by)
CONSEQUENCES OF ACCIDENTS:
a) Fatality / Injuries to workers
b) Fatality / Injuries to co-passers by
c) Loss to properties including public property
d) Lost of man-hours resulting in time and cost overruns
e) Public resentments, disgrace
f) Punishment under the relevant laws
VARIOUS STAGES OF WORK IN THE INSTALLATION OF
CONDUCTORS IN TRANSMISSION LINE
a) Insulator and aerial roller hoisting
b) Paying out of pilot wire
c) Paying out and sagging of Earth wire.
d) Paying out of conductor
e) Rough sagging
f) Final sagging
g) Clipping and fixing of line spacers
h) Fixing of jumpers
i) Stringing of river crossing reaches
j) Power line crossing
k) Stringing across Highways and other service roads
l) Transportation and stacking of conductor drums and
HAZARDS ASSOCIATED AT VARIOUS STAGES OF WORK:
INSULATOR AND ARIEAL ROLLER HOISTING
a) Fall of workmen from
a) *Use of fall arrester must be ensured for
cross arm sitting location
making vertical movement over tower.
* Proper use of double lanyard type full body
descending over tower.
harness shall be ensured.
b) Fall of insulator string or
b) * Proper fixing of cotter pins/split pins must
other tools and tackles.
insulator boxes and heavy
A) *Fall arrester.
And for each
* Good condition
double lanyard Safety
b) * Availability of
be ensured before hoisting insulator string.
12mm dia wire rope as
* Check the wire rope (12mm) being used for
And for each
insulator string hoisting for any type of visual
c) Hit by tractor in path of
* Good condition single
sheave pulleys of
* Before hoisting proper working condition both
bearing type only.
* Additional safety
rope used foe securing
For every road
also only bearing type pulleys shall be used.
single sheave pulleys
* if open hook type single sheave pulleys are
of open hook type.
being used , then additional safety rope shall be
* Good condition
D) Regular and
used for avoiding its accidental release.
16mm dia wire rope
for every lot of
* only 16mm dia wire rope sling should be used
the single sheave pulleys shall be ensured and
for securing single sheave pulleys with tower
members provided , precautions has been taken
against sharp edges of tower members.
* License and driving
skill of operator/
* Check for proper connection of aerial roller
with insulator string.
hoisting tower erection
3. Always avoid bending of insulator string while
must be complete in all
hoisting i.e. P.P rope or wire rope shall be tied
insulator disc from top. Bending of
shall be given to cross
insulator string may lead to failure of R-clips.
* Only licensed and well trained driver shall
be engaged for operating tractor, used for
insulator string hoisting.
tower members must be
* If at all any road crossing exist in maneuvering
path of tractor, presence of ‘ SIGNALMAN’ must
be ensured .
Maneuvering path of
d) *Over height stacking of insulator boxes
shall be avoided at location.
* Wooden planks having nails shall be kept well
away from site to avoid nail prick.
*WEARING OF SAFETY HELMET AND SAFETY
SHOE IS MUST BY ALL PERSONNELS
IRRESPECTIVE OF NATURE OF JOB.
COMMAN PRACTICE: it is very common practice
of using step bolts, in D-shackles and in aerial
roller assembly , which are not meant for heavy
always suspected to failure.
PAYING OUT OF PILOT WIRE
a) Minor cut injury to
A) Periodical visual inspection of pilot wires
Condition of pilot wire
fingers due to
for wear and tear and other visual damages
Condition of P.P rope
protruding wires of pilot
shall be done.
Effective Use of PPE’s
B) Use of leather type hand gloves shall be
b) Fall of workmen from
ensured to minimize the severity in case of
IMPORTANT CHECK: it
is generally noticed
that local lineman uses
aerial roller (for passing
C) Use of double lanyard full body hare ness
P.P rope through roller)
shall be insured.
11kv and 33kv power
Double arrangement for ascending over
lines and fitters of
insulator string shall be done as follows—
stringing gang uses to
descending over tower.
D)) Lanyard of safety belt shall be wrapped
to give shutdown of
lower the conductor
after de-energizing the
around the insulator string.
line. Following min.
E)) Jhulla arrangement made of 20mm P.P
precautions must be
ensured in such
rope, controlled from ground shall be used.
D) Over turning of
F) Regular pep talk shall be done and
1. be perfectly sure
awareness should be created among
transporting pilot drum
workmen regarding safe handling &
feeder (of the
transportation of pilot drum reel.
F) Pilot wire connectors shall be checked
2. Ensures the does not
1.pilot wire connectors:
for any type of visual damages in –
have any looping with
Pin and its threaded portion
other line near by and
Roller & U-portion
particular line) ,
installed in substation .
then decide the point
of opening jumpers.
2. eye splicing in pilot
G) Visual checks shall be done for condition
( views of local people
of eye loops made in pilot wire before every
must be taken
regarding the rout and
interconnection of line)
3. Power line / road or
H) Obtain proper shutdown before lowering
the conductors of any line crossing.
jumpers ensure the
I) Proper scaffolding capable of bearing
line is discharged
electrocution / injury to
load of pilot wire and conductors shall be
through bundling the
made for every P&T and road crossing.
3. Before opening the
conductors by passing
a p.p rope over it.
J) Suitable warning signs with signalman
4. Ensure the use of
(equipped with walky-talky) shall be
hand gloves meant for
deployed at every road crossing irrespective
working on HV/EHV
of its type and users.
5. The conductors shall
be lowered and kept in
PAYING OUT OF CONDUCTOR
POSITIONING OF TSE MACHINES
machine to a long distance.
Toppling of machine
B) Check air pressure and find out the suitable
A) Proper care shall be exercised while shifting
approach road for shifting.
C) While shifting no workmen shall be allowed
ride over it.
D) Well-experienced tractor driver shall be taken
for the task.
E) TSE machines shall be properly anchored with
dead-end anchors in the ground. The preferable
angle with ground should be 45* or less.
F) The puller shall be placed at a distance (from
Ist normal tower), not less than three times the
PRE PAYING OUT CHECKS
A) DRUM POINT
Site Engineer / TSE operator / gang leader
Hit injury to workmen
A) Hand gloves shall be used while handling wire
while placing two ends
meshed single/ double end shocks.
and single ends shocks.
B) Watch out for protruding wires, and removes
drums at least 30 M
B) Hit injury or cut
the same by cutting plier and if the wire mesh is
injury while placing
severely damaged replaces it with new one.
drum lifting jack or
C) Place the drum-lifting jack on firm and level
ground to avoid is toppling.
C) Failure at headboard
D) Never replace drum-mounting shaft with any
machine is smooth and
other inferior means such M.S or tor steel used
free from obstruction.
for reinforcement work. Use only recommended
C) The area between
connectors only in drum lifting jack.
E) Check the Physical condition and load bearing
machine must be kept
capacity (from test certificate of supplier) of
swivel joints (articulated joints) provided behind
F) Check the condition of wire rope and single
end wire meshed shocks before applying the
G) place suitable capacity D-Shackles at each
back to the tensioner
B) Check weather the
conductor release from
drum and entry into
SITE ENGINEER / GANG LEADER
A) Cut injury in fingers
A) Proper personnel precautionary measures
while handling pilot wire
shall be ensured in pilot wire reel (while
removing from puller machine after complete
B) hit injury/hit injury
A) Cut injury in fingers
--Same as above--
( loading/unloading) of
pilot wire reel.
GUYING OF DEAD-END TOWER
The make-up end tower shall be properly guyed
anchorage or guy rope
before with the help of 18mm dia wire rope and
angle of turn shall be
deadment anchor. The tightening of turnbuckles
damage of tower (cross-
shall be done carefully to avoid extra loading on
cross arm. Pit for dead ment, standards of
logwood shall be maintained as mentioned
rope according to the
turn of line . angle of
guy rope shall not be
more than 45* with
Ensure use of fall arrester for ascending and
Ensure effective tying
descending over tower.
of wire rope with cross
Ensure use of double lanyard full body harness
while working at height.
Ensure use of lifeline for making horizontal
movement over cross arm.
PAYING OUT OF CONDUCTOR
TIGHTIENING OF PILOT WIRE FROM
This is the most critical & hazardous
TO WORKMEN AND
activity of machine paying out operation. It
SIGNALMAN WITH RED
is well known that pilot wire are laid on
ground through out entire section proposed
PALCED IN BETWEEN
for paying out. When puller starts
tightening, pilot wire uses to uplift with
STRATING PILOT WIRE
high swing and speed.
& GREEN FLAGS WITH
OPERATION. AT LEAST
PULLING OF CONDUCTORS
SEVERE HIT INJURY
A) While conductor paying out is under
progress one supervisor (must be capable
WORKMEN AND SIDE
of making effective communication with
PASSERS, ANIMALS &
puller and tensioner operators and other
intermediate personnel’s positioned at road
/ power line crossings) must have to move
B) FAILURE OF PILOT
with head board.
WIRE OR PILOT
B) check out for free running of aerial
headboard can stuck.
rollers and also obstruction free passing of
RESULTING IN HIT
head board , mid-span joints ,pilot
falling in the line of
connectors by deploying signalman’s at
every tower . hey may tasked with keeping
vigil in between spans so as to keep
unauthorized personnel’s away from
particular phase corridor.
C) Check SWL of pilot wire connector and
its physical condition and also instruct
operator (puller) slow down pulling when
connector uses to enter in bull wheal of
MAKE UP & ROUGH SAGGING OF
out shall be checked
such trees, buildings &
dangerous, and it must
taking any chance.
SITE ENGINEER / GANG LEADER
Ensure the effective depth for deadment (depth
not less than 6.0feet) and also condition of wood
ANCHOR / FAILURE
log(length not less than 6.0 feet and dia. 10-
OF CAME ALONG
14inches)or steel beam of suitable section shall
Use of 18mm or 20mm steel wire rope in good
condition shall be used for holding conductors.
ENSURE THE EFFECTIVE
Check the condition of came along clamps& D-
shackles being used for holding conductors for
NEALRY 6.0 FEET.
A) Liner condition of came along clamp.
GROUND) AT LEAST 10.0
B) Availability of all bolts& nuts and packing
–12.0 FEET AWAY FROM
TOP OF PIT. FOR THAT
C) Availability of both side check nut.
SLOPE CUTTING AT 45*
D) Suitable capacity of D-shackle (min. 5.0 ton
SHALL BE ENSURED TO
best suited 10.0ton capacity)
E) never replace the pin of D-shackle with any
FINAL SAGGING OF CONDUCTORS
CHECK FOR SAGGING ARRANGMENT AND
TOOLS & TACKLES
SITE ENGINEER/ GANGLEADER
Use articulated joint
We must note final sagging is the most
of capacity not less
critical activity of stringing which involves
application of very have load and failure of
any kind can disastrous. Such as fall of
towers injuries to workmen.
mm wire rope used
Before finalizing the tools and tackles we
must give attention over sag chart and
twist in wire rope.
select the section that requires heaviest
loading and accordingly select tools and
tied at both end of
tackles for all sections.
A) Check the condition of sag plate and
condition of welding. in. thickness of sag
plate shall be of 12mm.
avoid its turning.
connecting sag plate with four-sheave pulley
through close type
B) Use good condition 12.0mm dia. Wire rope for
A) Near tip of the
making lifter arrangement with two four sheave
pulley sets. Both four sheave pulley shall be
separated a min. length 50.0-60.0M wire rope of
12.0mm dia. length of lifter arrangement should
rafter of cross arm
with tower leg.
be sufficient enough so as to ensure tightening
A min. of 10.0 ton
capacity sag winch
C)one set of lifter arrangement uses to lift two
Site engineer /gang leader
Accordingly select the suitable capacity of four-
sheave pulley block (SWL of min. 10.0Ton for
Equalizer pulley and four-sheave pulley shall be
connected directly with 15.o ton capacity D-
A) Check the condition
and suitability of bolts
V-sling used for holding conductors shall of—
A) 18.0mm wire rope for twin conductors
being used for holding
sag winch with tower
B) 22.0mm wire rope for quad conductors.
B) proper working of
Use twin came along clamps for holding single
Three bolt earth wire
wire rope after giving
MARKING AND CONNECTING OF
CONDUCTORS WITH HARDWARE FITTINGS
JHUMPERING AND SPACERING
Site engineer /gang leader
quad and 5.o ton for twin).
Incorrect and may
lead to failure of
cross –arm from
leg member and
rope from single
sheave pulleys ,
COMMAN CAUSES OF ACCIDENTS IN THE WORK OF INSTALLATION OF CONDUCTORS IN T/L
1. General lack of awareness and commitment to safe working methods by workers, supervisors,
& site Engineers.
2. Negligence in using appropriate personnel protective equipments at work places.
3. Lack of knowledge and experience in proper use of personnel protective equipments.
4. By passing / ignoring safety rules for reasons of misconceived convenience for faster
Execution of work.
5. Use of an inappropriate / damaged tools and tackles.
6. Failure of tension bearing materials/ equipments.
7. Inadequate guying of towers or failure of tension bearing tools.
8. Improper or over tightening of conductors during sagging operations.
9. Lack of good communication and commuting facilities.
10. Lack of proper training and continuing education to workers, supervisors and
Engineers in construction methods.
11. In adequate supervision of work by qualified and experienced personnel.
12. Lack of discipline in controlling non-compliance of safety regulations.
13. Exhaustion due to over working by workers.
14. Scattered working locations, difficult in having proper control over work locations.
15. Difficult terrains and natural topography
MEASURES AND PRECAUTIONS TO BE TAKEN IN WORK OF INSTALLTION OF CONDUCTORS IN T/L
1. Preparation of towers – tower shall be complete in all regards before starting stringing
2. Guying arrangement of towers shall be done as per given work procedure
3. Inspection and testing of tools and tackles ( follow checklist)
4. Inspection of personnel protective equipments for adequacy and workability.
5. Pre-task briefing to workmen and gang leaders before starting the job and fixing of
6. Information and caution to general public through caution boards and sign boards.
7. Identification of nearby hospital /medical center as a emergency preparedness.
8. Removal of tress and other visual obstructions in line corridor.
9. Identification of existence, source and listing power lines in section where the work is set
10. Arrangements for road or highways crossing coming in pathway of line corridor.
11. Providing temporary earth electrode for stringing equipments.
12. Adequate no. of First –Aid kit shall be made available at all work places.
13. Any restrictions on patter n of loading of towers shall be ascertained from designer.
14. Ascertaining for restrictions on placement of pulleys and application of tension for hoisting
and sagging operation.
COURSE OF WORK
1. checking of all the towers immediately before commencement of insulator hoisting, for
tightening punching, tack welding and availability of all members.
2. Positioning of pulleys for hoisting of insulators and other materials and equipment to be done
correctly to avoid improper pull on the cross arms and towers. (Refer insulator hoisting
2. Clear path for maneuvering tractors puling the hoisting slings for lifting material /
4. Availability of gang leader to co-ordinate pulling and lifting operation.
5. Proper counter weight anchors or log anchors to be installed for guying the towers, tension and
puller equipments and for holding conductors under rough sag.
6. Turn buckles used for stay wires should be tightened periodically.
7. All workers working at height above 2.0M heights shall have to wear safety belt.
8. Effective and clear communication system shall be made available
METHODOLOGY OF STRINGING
Stringing Methods & General Aspects
Methods of stringing.
There are basically two methods of stringing. These are
i) Slack or Manual methods
ii) Tension method
i) Manual method:
Using this method, the conductor is pulled along the ground by means of a pulling vehicle
(normally tractor),or the drum is carried along the line on a vehicle and the conductor is
deposited on the ground. The conductor drums are positioned on drum stands or jacks either placed
on the ground or mounted on a transporting vehicle. These stands are designed to support the drum
on an arbor, thus permitting it to turn as the conductor is pulled out. Usually, a braking device
is provided to prevent overrunning and backlash. When the conductor is dragged past a supporting
structure, pulling is stopped and the conductor is placed in travelers attached to the structure
before proceeding to the next structure.
ii) Tension Method:
Using this method, the conductor is kept under tension during the stringing process. Normally, this
Method is used to keep the conductor clear of the ground and obstacles, which might cause conductor
Surface damage and clear of energized circuits. It requires the pulling of a light pilot line into
the travelers, which in turn is used to pull in a heavier pulling line. The pulling line is then
used to pull in the conductors from the drum stands using specially designed tensioners and
pullers. For lighter conductors, a lightweight pulling line may be used in place of the pilot line
to directly pull in the conductor.
The stringing procedure is broadly divided into the following steps.
Paying out & stringing of earth wire.
Guying arrangement of tower
iii) Insulator and aerial roller hoisting
Paying out of pilot wire
Paying out & stringing of conductor.
Final sagging of earth wire & conductor.
Clipping and fixing of accessories.
Fixing of line spacers
viii) Fixing of jumpers
i) Paying out & stringing of earth wire:
Normally stringing of earth wire is done manually since handling the earth wire is easy and it does
not get damaged easily. First, earth wire rollers are provided on the earth peaks of all the
suspension towers in the section. Before hoisting of earth wire rollers, it may be ensured that the
rollers are free from friction.
A lineman/ fitter may be kept on each tower to ensure free running of the rollers with a red &
Green flag and whistle. At the starting end of a section, earth wire reel is mounted on roller
jacks or horizontal turntable. The earth wire is pulled from tower to tower manually or by using a
tractor. After reaching the next tower the earth wire is passed through the suspended earth wire
rollers with the help of a polypropylene rope and paying out is continued further. After one length
of earth wire reel is exhausted, the second length of wire is paid out for the balance section. Mid
span joint for earth wire is compressed on the ground joining the two lengths.
Guying arrangement of tower
Before commencement of stringing, the angle towers where the stringing is to be started have to be
Provided with guy supports for all the three phases. The guys used generally are 20mm steel wire
rope. The guys are attached to the tower at the tip of the cross arms and center of the bridge, to
the strain plates with suitable D shackles. The guys are anchored in the ground at an angle of 45
Degrees or less from the horizon, attached to dead end anchors. For making dead end anchors in the
Ground, pits of 1.5mx0.6m, for a depth of 1.5m can be dug. A set of steel beam and channels tied in
the center with 16mm wire rope, is lowered and the pit is back filled while compacting. The guy
wire is attached to the dead end anchor wire with the help of turnbuckles of 10 tonnes capacity.
Alternately, instead of buried ground anchors, a dead weights of sag 5 to 10 tonnes can be placed
on the ground and sag wire attached to them securely. After pulling up the slackness in the guy, it
is tightened by the turnbuckle. Excessive tightening of the guy should be avoided. It is advisable
to tighten the guy progressively at the time of rough sagging of the conductor.
Insulator and aerial roller hoisting
Transportation of Insulators
The required no. of insulators shall be transported to the tower locations with the wooden packing.
The crates shall be opened at the tower location. The Insulator hoisting is done well in advance of
Commencement of paying out operation.
After opening of the crates, insulators shall be laid in series, on wooden planks below the
suspension points. The insulators shall be cleaned with water and wiped dry with clean cloth free
from grease and oil. Insulators shall be checked for any chipping or crack and shall be replaced
with new one if found defective. The no. of insulators required for string shall be joined and `R'
clips in the clevis shall be expanded to avoid slippage of the pin.
The joints of all insulators should be checked and `R' clips should be expanded.
The bottom insulator is joined to the moose aerial roller. The five wheels of the aerial rollers
should be checked for free running. The neoprene rubber cushion on the outer rollers shall be
checked for any cracks/wearing out and shall be changed if required.
A single sheave pulley is fixed to the cross arm very near to the suspension hanger. A 20 mm
polypropylene rope or 12mm wire rope is passed through the pulley and both the ends are brought to
the ground. One end of the rope is firmly tied below the 3rd or 4th insulator. The complete string
with aerial roller is lifted up by pulling the rope through a pulley attached to one of the tower
legs by using tractor/manually After reaching the top the string is attached to the suspension
hanger and string is released slowly to hang free.
Paying out of pilot wire
In tension stringing, a pilot wire is used to pull the conductor. The pilot wire is initially laid
through the center wheel of the aerial roller. A 22 mm dia pilot wire is generally used for pulling
of quad moose ACSR conductor. The pilot wire can be laid length by length and joined with pilot
At power line crossings, the pilot wire is laid from both sides and free ends are joined after
obtaining the shutdown of the power line. Sound Scaffoldings shall be provided for P&T and road
crossings before paying out of the pilot wire. A stand signalman shall be ensured with Red and
green flag and also with walky-talky to ensure effective communication pilot wire pulling equipment
(Tractor or Puller).
Paying out & stringing of conductor.
A) Position of tensioner and puller:
The paying out of conductor is done generally between two tension towers. The puller machine can be
Positioned behind the tension tower on one side and the tensioner in front of the tension tower on
the other side. The entry of the pilot wire into the bull wheels of the puller machine and running
out from tensioner machine should be as nearly horizontal as possible. Both the machines should be
securely anchored with two dead end anchors in the ground and slackness is removed in the stay.
The placement of drum jacks should be such that the lateral angle of conductor approach into the
bull wheel through guide rollers is low enough to avoid rubbing on the sides and creating loosening
of the outer strands and bird caging. The distance of the drums from the tensioner shall be at
least 25 to 30 mtrs so as to distribute the effect of sliding of outer strands due to low back
tension. The reel should be positioned so that it will rotate in the same direction as the bull
Paying out of conductor:
For passing the conductor through the bull wheels of the tensioner, a 25 mm polypropylene rope is
initially wound over each bull wheel pair in the same way as the conductor will pass during
Running. The ropes are connected to the conductors. The conductor run shall be from the topside of
the drum. The rope is pulled by starting the tensioner at low pay out tension to pass the conductor
through bull wheels and are brought out through the guide rollers. The sub conductors are attached
to the equalizer pulley/running board by means of wire mesh/end socks and swivel joints. The pilot
wire is attached to the other end of the running board with swivel joint. At the puller site, the
pilot wire is pulled to remove all slackness using the reel winder. The wire is passed through bull
wheels of the puller and connected to the reel winder machine. The tensioner can be initially set
for a tension of 2 to 2.5 tones. Caution should be made over the wireless hand set to all the Staff
who are at middle points and to the tensioner operator that pulling is about to be started so that
they can stay clear of pilot wire. The puller is started to draw up the pilot wire until the bull
wheels of the tensioner start moving.ow paying out of Bundle conductors with tensioner and Puller.
Care should be taken that the pilot wire does not get entangled in trees, scaffoldings, Aerial
rollers etc. while going up during tensioning. This can be monitored by the staff who are posted in
between the section and guiding the puller operator over the wireless sets. The pulling of the
conductor may be done at a moderate speed while the running board is passing through the aerial
rollers.The tension in the tensioner must be adjusted so that the conductors travel well over the
ground. In long spans where conductor is likely to touch the ground, ground rollers may be placed
so that the conductor can pass without any scratches. A running ground shall be connected to the
conductor and pilot wire before paying out near the tensioner and puller which shall be earthed at
the nearest tower. Platforms shall be erected with sturdy bellies, where roads, rivulets, channels,
telecommunication or overhead power lines, railway lines, etc. have to be crossed during stringing
Operations. It shall be seen that normal services are not interrupted or damage caused to property.
The back tension of the conductor behind the tensioner has to be maintained as per the requirement
of the tensioner deployed. The back tension is adjusted by means of brakes provided on the drum
jack. A running ground shall be connected to the conductor and pilot wire before paying out near
the tensioner and puller which shall be earthed at the nearest tower.
The speed of pulling of the conductor should be such that to achieve smooth operation. Slower
speeds may cause significant swinging of the running blocks and insulator hardware assemblies.
stringing generally is about half the sagging tension. When long lengths of conductors are strung,
the tension at the puller may be higher than that at tensioner due to the length of conductor
strung, number and performance of travellers, differences in elevation of supporting structures
Jointing of conductor:
Just before one length of the conductor paying out is completed another drum has to be deployed in
advance beside the first drum. The paying out has to be stopped by braking the tensioner and
stopping the puller simultaneously. The paid out conductor of first drum is held with bolted comealong clamps at a distance of 40 to 50 mtrs from the tensioner. The come- along clamps are attached
to the ground anchor stays. The conductor of the first drum is held and the free end is cut. The
free end of the second drum is also prepared. The two ends are joined with a wire mesh mid span
socks. The paying out is again started by releasing the come along clamps until the mid span socks
emerges outside the tensioner and pulling is stopped. After anchoring, the conductor is slowly
drawn out from the two end socks. The mid span socks is removed and mid span compression joint is
After making mid span joint, the joint is covered with joint protector sleeves which is designed to
pass over the aerial roller grooves without damaging the mid span compression joint. The paying out
is continued until the conductor reaches the puller end in sufficient length to be connected to the
Rough sagging of conductor
Before final sagging the conductor, it is rough sagged to a tension slightly less than the final
Tension. Since final sagging is done from one end of the section, the conductor is initially
attached to the double tension string assembly on the other end. For doing rough sagging, initially
the double tension string assembly is assembled with insulators and hardware and hoisted to the
cross arms/bridge as done in the case of suspension towers. The dead end cones are compressed on
both the sub conductor ends. The conductor is held by come along clamps at a distance of 5 to 6
mtrs from the dead end cones and with the help of a pulley connected to a ground anchor, the
conductor is pulled to slacken the free end of conductor (sufficient length to be attached to the
hoisted insulator string assembly).By holding the conductor with pulley, the dead end cones are
attached to the tension string. The pulley is slowly released and the conductor will haul-up itself
to the top. The come along clamps and pulley etc. are removed.
Final sagging of conductor
The sagging of the conductor shall be done using sagging winches. After being rough sagged the
conductor shall not be allowed to hang in the stringing blocks for more than 96 hours before being
Pulled to the specified sag. The tensioning and sagging shall be done in accordance with the
approved stringing charts before the conductors are finally attached to the towers through the
insulator strings. Only after the conductor is rough sagged on the adjacent section, final sagging
can be done in the preceding section to avoid overloading of towers. For doing the sagging
operation, a span has to be selected in the section to fix the sag board and check the sag. In the
event of using sag tension charts showing sags in each of the actual spans and tension in each
section, usual practice is to place the sag boards in the longest span of the section, and in a
span where the difference of elevation in the two suspension points is minimum.
The tension insulator strings are hoisted with all hardware on the tower. The conductors are held
by come-along clamps and attached to Separate four sheave pulleys at sufficient distance of say 40
to 50 mtrs depending upon rough sag condition and height of the tower. The other ends of the foursheave pulleys are connected to the line side yoke plate of the double tension string. The pulling
wires of the four-sheave pulley are passed through a set of single sheave pulleys along the body of
the tower to the ground level. The initial pulling is done with the help of tractor/truck. Then the
Pulling ropes are attached to hand winches mounted on the legs of the tower or power winches duly
Anchored. Wooden cross bars are tied to the body of the four sheave pulley and held by ropes in a
Horizontal position to avoid over turning of the four-sheave pulley and twisting of the pulling
wires. The conductor is brought into final sag position with the help of winches and the sag is
checked by sighting far end sag board from behind the near end sag thread by matching elevation
tangent of the conductor curve. Sighting should be done keeping sufficient distance from the sag
line to avoid parallax error.
After reaching the final sag, the free end of the conductor is picked up and pulled by rope and
pulley attachment along the line of the string. The conductor is marked at the point where cutting
is to be done and dead-end cone is to be pressed. The free ends of the conductors are brought down
and cut near the marking and dead end cones are pressed. The four-sheave pulley is slightly
tightened to facilitate attaching the dead end cone to the tension assembly. After fixing, the
four-sheave pulley is slowly released, brought down and all clamps and pulleys are removed.
Clipping of conductors:
The clipping of the conductor follows sagging operation. This entails removing the conductors from
The rollers and placing them in suspension clamps attached to the insulator string. Before taking
Up clipping operation, the conductor is earthed properly on suspension towers. The conductors are
Held with hooks at 2 mtrs away from the aerial roller on both sides. A wire rope is connected to
Both the hooks passed through a pulley positioned on the cross arm tip in series with a pulllift/ratchet lever hoist/four or two-sheave pulley. The center of the aerial roller is marked on
the conductor. The conductor is raised by about 75 to 100 mm and the aerial roller is removed and
lowered by rope and pulley. The suspension clamp and armoured rods are fixed with neoprene rubber
cushions centered over the marking. The suspension clamp is placed over the armored rods and
clamped with U bolts. The suspension clamp is connected to the string and the lifting device is
Released. The insulator string will hang freely with the conductors suspended in the clamps. The
Verticality of the string may be checked with plumb bob. Care should be taken to prevent any damage
to the conductor while being lifted by hooks. Gunny bags or rubber pads may be used around the
conductor to prevent damage to the outer strands.
Fixing of line spacers :
Following the clipping operations for bundled conductor lines, spacers are usually installed. This
is done by placing personnel on the conductors with the use of a conductor cycle normally known as
spacer-cycle to ride from structure to structure. Depending on the length of line to be spaced and
the equipment available, cycles may be hand powered or diesel powered. Care must be exercised to
sufficiently to cause hazards by obstructions (spacers, repair sleeves, mid span joints etc.) over
which the cycle will pass. The installation of the spacers on the conductor varies with span
length, the type and manufacture of the spacer and is normally done in accordance with the
manufacturer's recommendations duly approved. The spacer cycle is hoisted on the bundle at one
tension end. In case of engine-powered cycles, the spacer cycle is normally provided with travel
meter, with the help of which the spacers are fixed at required distances as per the placement
chart. In case of hand-powered cycles, the personnel pulling the cycle with rope measure the
distances on ground and placement is done on the top. A number of models of spacers are being
manufactured and the method of installation varies with the design of the spacers. After reaching
the next suspension tower, the cycle is transferred to the next span by crossing the suspension
clamp with the help of crossing ropes provided in the cycle. In case of spans crossing HT/LT lines,
care should be taken while drawing the spacer cycle with rope. Safe electrical clearance should be
maintained to the spacer cycle and rope. For crossing the lines, the rope shall be drawn up to the
cycle, and brought down after crossing the line, keeping sufficient clearance from the line. The
person on the cycle can travel himself to cross over the section above the power line.
Installation of dampers:
clipping to prevent any possible damage because of vibrations to the conductors, which at critical
tensions and wind conditions can occur in a matter of hours.
The jumpers at the section/angle towers shall be formed to parabolic shape to ensure minimum
(Generally where angle of deviation is more than 45 degrees), to restrict the jumper swings to the
design values at both middle and outer phases. Clearance between the conductors and ground, jumpers
and the tower steel work shall be checked during erection and before commissioning the line. While
jumpering is made, a local earthing should be made to avoid any static discharge that might occur
due to the voltage induced on the line by existing power lines in the vicinity. Care should be
taken to leave jumpers for one angle tower in a continuous stretch of 25 to 30 kms, so as to
prevent transmission of electric shock. These left out jumpering can be taken up during final
inspections. The individual sections jumpered shall be kept earthed and earth shall be removed only
before commissioning. The jumpers in general are 10 to 15 mtrs in length. Hence left over bits of
conductor shall be used for jumpering. For installation of jumpers, the distance between the jumper
pads of dead end cones is measured by passing a rope in the shape of a jumper and by checking
vertical clearance from the cross arm end. Conductor is cut after making adjustment in length for
the jumper cone dimension. The inner and outer conductor of the bundled jumper are of different
lengths, which shall be measured separately. This will ensure a horizontal plane of the jumper
compressor. The conductors are laid out on the ground parallelly and spacers are fixed as per the
fixing instructions. The jumper is hauled up from both ends of the tension clamps and jumper cone
is attached to the connector of the dead end cone. Clearance to the tower body shall be checked as
per the drawing.
SAFETY ASPECTS OF TOWER ERECTION
METHODS OF ERECTION
There are THREE main methods of erection of steel transmission towers, which are described, as
i. Built-up method or piecemeal method.
ii. Section method
iii. Ground assembly method.
Built up method
This method is most commonly used in this country for the erection of 66 KV, 132 KV, 220 KV and 400
KV Transmission Line Towers due to the following advantages.
i. Tower materials can be supplied to site in knocked down condition which facilitate easier and
ii. It does not require any heavy machinery such as cranes etc.
iii. Tower erection activity can be done in any kind of terrain and mostly through out the year.
iv. Availability of workmen at cheap rates.This method consists of erecting the towers, member by
member. The tower members are kept on ground serially according to erection sequence to avoid
search or time loss. The erection progresses from the bottom upwards, the four main corner leg
members of the first section of the tower are first erected and guyed off. Sometimes more than
continuous leg sections of each corner leg are bolted together at the ground and erected.The cross
braces of the first section which are already assembled on the ground are raised one by one as a
unit and bolted to the already erected corner leg angles. First section of the tower thus built and
horizontal struts (bet members) if any, are bolted in position. For assembling the second section
of the towers,two gin poles are placed one each on the top of the diagonally opposite corner legs.
These two poles are used for raising parts of second section. The leg members and braces of this
section are then hoisted and assembled. The gin poles are then shifted to the corner leg members on
the top of second section to raise the parts of third section of the tower in position for
assembly. The gin pole is thus moved up as the tower grows. This process is
continued till the complete tower is erected.Cross-arm members are assembled on the ground and
raised up and fixed to the main body of the tower. For heavier towers, a small boom is rigged on
one of the tower legs for hoisting purposes. The members/sections Are hoisted either manually or by
winch machines operated from the ground. For smaller base towers/vertical configuration towers, one
gin pole is used instead of two gin poles. In order to maintain speed and efficiency, a small
assembly party goes ahead of the main erection gang and its purpose is to sort out the tower
members, keeping the members in correct position on the ground and assembling the panels on the
ground which can be erected as a complete unit. Sketches indicating different steps of erection
by built up method are shown at Figure 4.1 to Figure 4.7.
Guying arrangements are to be done at waist level/bottom cross-arm level as well as in the girder
level/top cross-arm level depending on SC/DC towers and it is to be installed at 450 from vertical.
The deadments for guying arrangements are to be properly made. A sample of deadments drawing is
enclosed at Figure 4.8 for reference. Guying should be steel wire or polypropylene rope depending
Upon requirements. Nominal tension is to be given in guying wire/rope for holding the tower in