PROJECT:-765KV S/C RAIGARH-CHAMPA TL.
METHODS ADOPTED FOR CONDUCTOR INSTALLATIONS IN 7 65 KV T/L
a) Mechanized Paying out of conductors and installation Mechanized Manually b) Manual Paying out of conductor and its manual installation. Manual
TYPE OF RISK ASSOCIATED:
a)Fall a) Fall of workmen from height b)Fall b) Fall of objects from height, on workers and co-passers by by – c)Collapse c) Collapse of towers, conductors and hardware Fittings on workers and passers by by – d)Electrocution d) Electrocution due to contact of person / Conductors with live wires e)Hit e) Hit by Vehicles (Workmen and co passers-by)
METHODS ADOPTED FOR CONDUCTOR INSTALLATIONS IN 7 65 KV T/L
a) Mechanized Paying out of conductors and installation Mechanized Manually b) Manual Paying out of conductor and its manual installation. Manual
TYPE OF RISK ASSOCIATED:
a)Fall a) Fall of workmen from height b)Fall b) Fall of objects from height, on workers and co-passers by by – c)Collapse c) Collapse of towers, conductors and hardware Fittings on workers and passers by by – d)Electrocution d) Electrocution due to contact of person / Conductors with live wires e)Hit e) Hit by Vehicles (Workmen and co passers-by)
VARIOUS STAGES OF WORK IN THE INSTALLATION OF CONDUCTORS IN TRANSMIS TRANSMISSION SION LINE a)Insulator 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:
SL NO
HAZARD INVOLVED
REMEDIAL MEASURES
CHECK POINTS
.
ACTION
PERIODICI
BY
TY
REMARK
INSULATOR AND ARIEAL ROLLER HOISTING 1.
a) Fall of workmen from cross arm sitting location
a) *Use of fall arrester must be ensured for making vertical movement over tower.
CHECK FOR---
A) REGULAR
The most
A) *Fall arrester.
And for each
hazardous
* Good condition double
insulator
aspects of
lanyard Safety belt.
string
insulator
b) * Availability of 12mm dia
hoisting.
hoisting is
or while ascending and
* Proper use of double lanyard type full body
descending over tower.
harness shall be ensured.
b) Fall of insulator string
b) * Proper fixing of cotter pins/split pins
wire rope as a lifter.
when
must be ensured before hoisting insulator
* Good condition single
workmen
or other tools and tackles. c) Hit by tractor in path of his maneuvering. d) Hit Injury or crush injury
while
handling
insulator boxes and heavy aerial rollers.
string. * Check the wire rope (12mm) being used for insulator string hoisting for any type of visual damage.
sheave pulleys of bearing
b) REGULAR
uses to get
type only.
And for each
down
* Additional safety rope
insulator
through
used foe securing single
string
insulator
hoisting.
string for
sheave pulleys of open hook SITE
* Before hoisting proper working co ndition
type.
both the single sheave pulleys shall be
* Good condition 16mm dia
ENGINEER
ensured and also only bearing type pulleys
wire rope sling.
/ GANG
shall be used.
* License and driving skill of
LEADER
* if open hook type single sheave pulleys are being used , then additional safety rope shall be used for avoiding its accidental release. * only 16mm dia wire rope sling should be used for securing single sheave pulleys with
guide rope
For every road
tied with
crossing
bottom yoke
operator/ driver.
plate or with
IMPORTANT CHECK:
D) Regular
1. Before insulator hoisting
and for every
tower
lot of insulator
erection
must
be
complete in all regards. 2. more importance shall be
tower members provided , precautions has
given to cross arm i.e all the
been taken against sharp edges of tower
connecting bolts and tower
members.
members must be in properly
* Check for proper connection of aerial roller
intact condition.
with insulator string.
releasing c) REGULAR
boxes.
aerial roller.
3. Always avoid bending of insulator string
while hoisting i.e. P.P rope or wire rope shall be tied with 3 rd or 4 th insulator disc from top . Bending of insulator string may lead to failure of R-clips.
c)
* Only licensed and well trained driver
shall be engaged for operating tractor, used for insulator string hoisting. * If at all a ny road crossing exist in maneuvering path of tractor, presence of ‘ SIGNALMAN’ must be ensured .
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 loading and
always suspected to failure.
PAYING OUT OF PILOT WIRE 2.
a) Minor cut injury to
A) Periodical visual inspection of pilot
fingers due to
wires for wear and tear and other visual
protruding wires of
damages shall be done.
pilot wire. b)
Fall
from
of
workmen
cross
arm
position/ aerial roller
Condition of pilot wire Condition of P.P rope being
Site
used
Engineer
Effective Use of PPE’s
/ Gang
B) Use of leather type hand gloves shall
Jhulla arrangement
Leader
be ensured to minimize the severity in
IMPORTANT CHECK: it is
case of such incident.
generally noticed that local lineman uses to give shutdown of 11kv and 33kv
(for passing P.P rope
C) Use of double lanyard full body hare
through
ness shall be insured.
roller)
Or
otherwise
during
ascending
and
Double arrangement for ascending over
power lines and fitters of stringing gang uses to lower the conductor after deenergizing the line.
insulator string shall be done as follows —
Following min. precautions
descending over tower.
D)) Lanyard of safety belt shall be
must be ensured in such
c)
Hit
handling
injury
while
wrapped around the insulator string.
pilot
drum
E)) Jhulla arrangement made of 20mm
operations--1. be perfectly sure about distribution feeder (of the
reel.
P.P rope, controlled from ground shall be
particular line) , installed in
D) Over turning of
used.
substation .
tractor while
F) Regular pep talk shall be done and
transporting pilot
awareness should be created among
drum
workmen regarding safe handling &
point of opening jumpers.(
reel.
transportation of pilot drum reel.
views of local people must
E) OTHERS:
F) Pilot wire connectors shall be checked
1.pilot wire
for any type of visual damages in –
connectors:
Pin and its threaded portion Roller & U-portion G) Visual checks shall be done for
2. Ensures the does not have any looping with other line near by and then decide the
be taken regarding the rout and interconnection of line) 3. Before opening the jumpers ensure the line is discharged through bundling the conductors by passing a p.p rope over it.
2. eye splicing in pilot
condition of eye loops made in pilot wire
wire
before every use.
gloves meant for working on
H) Obtain proper shutdown before
HV/EHV lines.
3. Power line / road or
lowering the conductors of any line
highway crossing
crossing.
(chances of
I) Proper scaffolding capable of bearing
electrocution / injury
load of pilot wire and conductors shall be
to co passers.
made for every P&T and road crossing. J) Suitable warning signs with signalman (equipped with walky-talky) shall be
4. Ensure the use of hand
5. The conductors shall be lowered and kept in bundled condition.
deployed at every road crossing irrespective of its type and users.
PAYING OUT OF CONDUCTOR POSITIONING OF TSE MACHINES
3.
Hit injury to
A) Proper care shall be exercised while shifting
workmen—
machine to a long distance. r
Toppling of machine
B) Check air pressure and find out the suitable
d
while
approach road for shifting.
el
shifting/placing
C) While shifting no workmen shall be allowed
n
ride over it.
g
a
g
a
e
/ o
r
D) Well-experienced tractor driver shall be r
a
t
taken for the task. o
p
e
E) TSE machines shall be properly anchored S
E
with dead-end anchors in the ground. The /
T
preferable angle with ground should be 45* or e
r
less. e g
ni
F) The puller shall be placed at a distance E
times the tower height.
ti
PRE PAYING OUT CHECKS 4.
n
(from Ist normal tower), not less than three
A) DRUM POINT
S
e
A) Cut injury in fingers
A) Hand gloves shall be used while handling
IMPORTANTCHECK: A) place
while placing two ends
wire meshed single/ double end shocks.
the conductor drums at least
and single ends
B) Watch out for protruding wires, and
30 M back to the tensioner
shocks.
removes the same by cutting plier and if the
B) Hit injury or cut
wire mesh is severely damaged replaces it
injury while placing
with new one.
drum lifting jack or
C) Place the drum-lifting jack on firm and level
smooth
conductor drums.
ground to avoid is toppling.
obstruction.
C) Failure at
D) Never replace drum-mounting shaft with
C) The area between drums
headboard assembles
any other inferior means such M.S or tor steel
and TSE machine must be
point.
used for reinforcement work. Use only
kept
recommended connectors only in drum lifting
unauthorized entry.
machine. B)
Check
weather
the
conductor release from drum and entry into machine is and
barricaded
free
to
from
avoid R E
jack. A
D
E) Check the Physical condition and load L
E
bearing capacity (from test certificate of supplier) of swivel joints (articulated joints)
N
G
provided behind Headboard.
G
A
F) Check the condition of wire rope and single
R
/
end wire meshed shocks before applying the
N
E
E G
I
load. N E
G) place suitable capacity D-Shackles at each I
T
E
joint. S
PULLER POINT
A) Cut injury in fingers
A) Proper personnel precautionary measures
while handling pilot
shall be ensured in pilot wire reel (while
wire reel.
removing from puller machine after complete
B) hit injury/hit injury
binding).
while handling (
R E
R N
D
E E
--Same as above-I
A E G L
loading/unloading) of N
G E E
N I G
pilot wire reel.
A T S
GUYING OF DEAD-END TOWER The make-up end tower shall be properly
IMPORTANT CHECK: angle of
anchorage or guy rope
guyed before with the help of 18mm dia wire
turn shall be maintained for
itself
rope and deadment anchor. The tightening of
guy rope according to the
Failure
of
guy
resulting
damage
of
in
tower
(cross-arm) Fall
of
person
height while
turnbuckles shall be done carefully to avoid extra loading on cross arm. Pit for dead ment,
from
standards of logwood shall be maintained as mentioned above. Ensure use of fall arrester for ascending and descending over tower. 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 PULLER END
turn of line . angle of guy rope shall not be more than 45* with cross arm. Ensure effective tying of wire rope with cross arm.
/
SEVERE HIT INJURY
This is the most critical & hazardous
TO WORKMEN AND
activity of machine paying out operation.
SIDE PASSERS, ANIMALS & VEHICLES (ROAD CROSSING)
It is well known that pilot wire are laid on ground through out entire section proposed for paying out. When puller starts tightening, pilot wire uses to uplift with high swing and speed.
IMPORTANT SIGNALMAN GREEN
CHECKS: WITH
RED
FLAGS
&
WITH
WHISTILES MUST BE PALCED IN BETWEEN EACH BEFORE STRATING TIGHTIENING
PILOT
E
R
WIRE N
E
OPERATION. G
I
AT LEAST TWO SIGNAL MAN WITH
FLAG
AND
E
N
WALKIE
TALKI SHALL BE POSTED ON ALL ROAD CROSSINGS.
PULLING OF CONDUCTORS
S
I
T
a)SEVERE HIT INJURY TO
A) While conductor paying out is under progress one supervisor (must be capable
WORKMEN AND
of making effective communication with
SIDE PASSERS,
puller and tensioner operators and other
ANIMALS &
intermediate personnel’ s positioned at
IMPORTANT CHECK:
The entire section proposed for
paying
out
shall
be
checked
for
visual
hindrances
such
trees,
buildings & any other type of
VEHICLES (ROAD
road / power line crossings) must have to
structures where headboard
CROSSING)
move with head board.
can stuck.
B) FAILURE OF
B) check out for free running of aerial
Branches of tress falling in
PILOT WIRE OR
rollers and also obstruction free passing
the line of headboard are
PILOT WIRE
of head board , mid-span joints ,pilot
more dangerous, and it must
CONNECTOR
connectors by deploying signalman’s at
be cleared without taking
RESULTING IN HIT
every tower . hey may tasked with
INJURY.
R
any chance.
keeping vigil in between spans so as to
A
D
E L
E
keep unauthorized personnel’s away from N
G
particular phase corridor. C) Check SWL of pilot wire connector and
G
A
its physical condition and also instruct
R
/
operator (puller) slow down pulling when
N
E
E
connector uses to enter in bull wheal of
G
I
puller machine.
E
N I
T
E S
MAKE UP & ROUGH SAGGING OF CONDUCTORS
FAILURE OF
Ensure the effective depth for deadment IMPORTANT CHECK:
DEADMENT ANCHOR
(depth not less than 6.0feet) and also condition
/ FAILURE OF CAME
of wood log(length not less than 6.0 feet and
ALONG CLAMP.
dia. 10-14inches)or steel beam of suitable
10.0-12.0 FEET
6.O’’
section shall be ensured. Use of 18mm or 20mm steel wire rope in good condition shall be used for holding conductors.
ENSURE THE EFFECTIVE DEPTH
Check the condition of came along clamps& D-
OF
shackles being used for holding conductors for
FEET.
following-- A) Liner condition of came along clamp.
DEADMENT
ENSURE
NEALRY
6.0 R
THAT
WIRE
E
ROPE A
LEAST 10.0 –12.0 FEET AWAY G
D
EMEREGS (FROM GROUND) AT
B) Availability of all bolts& nuts and packing
FROM TOP OF PIT. FOR THAT
N
washers.
SLOPE CUTTING AT 45* SHALL
G
BE ENSURED TO AVOID DIECT
R
L
E
C) Availability of both side check nut. D) Suitable capacity of D-shackle (min. 5.0 ton
UPLIFT LOAD ON DEADMENT
E
E
/
A
I
N
ANCHORE. G
best suited 10.0ton capacity) E) never replace the pin of D-shackle with any
E
N
other means.
FINAL SAGGING OF CONDUCTORS CHECK FOR SAGGING ARRANGMENT AND TOOLS & TACKLES
S
I
T
E
FAILURE OF TOOLS AND
CHECK
POINTS
IN
FINAL
SAGGING IMPORTANT CHECK:
TACKLES ARRANGMENT.
RESULTING IN
We must note final sagging is the most critical activity of stringing which involves application of very have load and failure of any kind can disastrous. Such as fall of
Use articulated joint of capacity not less 3.0 ton with 12.0 mm wire rope used
in
between
sheave
fourpulley
arrangement
to
avoid
towers injuries to workmen.
kinking or twist in wire
Before finalizing the tools and tackles we
rope.
must give attention over sag chart and
P.P rope shall be tied at
select the section that requires heaviest
both end of four sheave r
loading and accordingly select tools and pulley shall be used to
d
tackles for all sections. GENERAL CONSEDRATION ACSR (QUAD) D/C LINE A) Check the condition of sag plate and condition of welding. in. thickness of sag plate shall be of 12mm. B) Use min. 15ton capacity D-Shackle for
avoid its turning.
to ensure tightening of conductor.
g
ni
type pulley positioned; e
n
A) Near tip of the cross arm.
A
min.
ti
e S
&
cross arm with tower leg.
arrangement should be sufficient enough so as
e
e
be routed through close
B) Use good condition 12.0mm dia. Wire rope
wire rope of 12.0mm dia. length of lifter
r
/
sheave pulley set should
B) Near bottom rafter of
shall be separated a min. length 50.0-60.0M
g
a
lead coming out from four
lifter arrangement.
sheave pulley sets. Both four sheave pulley
n
g
The 12.0mm wire rope
connecting sag plate with four-sheave pulley
for making lifter arrangement with two four
le
a
e
of
10.0
ton
capacity sag winch shall be used for giving load.
C)one set of lifter arrangement uses to lift two conductors in quad arrangement and one conductor in twin conductor arrangement.
Accordingly select the suitable capacity of four- Always avoid sudden loading sheave pulley block (SWL of min. 10.0Ton for quad and 5.o ton for twin).
during
final
sagging
operation. e
r
Check point for sag winch: d
Equalizer pulley and four-sheave pulley shall be A) Check the condition and connected directly with 15.o ton capacity D- suitability of bolts being used
el
a n
g
for holding sag winch with
shackle.
g
B) proper working of locking
r
A) 18.0mm wire rope for twin conductors
arrangement.
e
B) 22.0mm wire rope for quad conductors.
Three bolt earth wire clamp
g
a
tower leg.
V-sling used for holding conductors shall of —
Use twin came along clamps for holding single
or automatic clamp shall only be used for providing extra
conductor.
safety lock to wire rope after giving final load from sag winch.
MARKING AND CONNECTING OF CONDUCTORS WITH HARDWARE FITTINGS
CLIPPING ACTIVITY
e
n
in
e
/
S
ti
e
JHUMPERING AND SPACERING
Incorrect and may lead to failure of cross – arm from leg member and cross-arm rafter join position
Correct sequence of looping wire rope from single sheave pulleys , in insulator hoisting.
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
PREPARATORY WORKS 1. Preparation of towers – tower shall be complete in all regards before starting stringing operation. 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 accountability. 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 out. 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 Methodology)
2. Clear path for maneuvering tractors puling the hoisting slings for lifting material / Tensioning. 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 dra gged 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.
STRINGING PROCEDURE The stringing procedure is broadly divided into the following steps. i)
Paying out & stringing of earth wire.
ii)
Guying arrangement of tower
iii)
Insulator and aerial roller hoisting
iv)
Paying out of pilot wire
iv)
Paying out & stringing of conductor.
v)
Final sagging of earth wire & conductor.
vi)
Clipping and fixing of accessories.
vi)
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 rol lers 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.
HOISTING: 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.
INSULATOR HOISTING
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 wire connectors. 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 fro m 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 tensi on. The reel should be positioned so that it will rotate in the same direction as the bull wheels.
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 c lear 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. Higher speeds can create greater damage in case of malfunction. The tension applied during 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 etc.
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 come-along 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 made. 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 Tension hardware.
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 conn ected 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 t owers 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 four-sheave 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 bo dy 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 pull-lift/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 spacercycle 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 ensure that the concentrated load of the man, car and equipment does not increase the sag
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:
Vibration dampers/spacer dampers are normally placed on the conductors immediately following 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.
Jumpering The jumpers at the section/angle towers shall be formed to parabolic shape to ensure minimum clearance requirements. Pilot suspension insulator string shall be used if found necessary (Generally where an gle 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 indu ced 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 bundle when installed. After cutting the conductor, jumper cone is pressed using hydraulic 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.
STRINGING SAFETY CHECK LIST
METHODS OF ERECTION There are THREE main methods of erection of steel transmission towers, which are described, as below
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 cheaper transportation.
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 arrangement 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 45
0
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 position.
