STRINGING & FINAL CHECKING OF
TRANSMISSION LINES
STRINGING - METHODS
• Basically there are three methods of stringing
– Manual Method
– Tension Method
– Helicopter method
STRINGING METHODS
• Manual Method:
– In this method, conductor is pulled along the
ground by means of a pulling vehicle. The
conductor drum shall be mounted on a drum
lifting jack.
– The major drawback is that surface condition of
the conductor will get damaged
Tension stringing method
• This method is used to keep conductor surface safe during stringing process.
In this method, the conductor is kept under tension during the stringing
process to keep the conductor clear of the ground.
• A pulling line is initially pulled into the travelers which is then used to pull
the conductor from the reel stands using specially designed tensioners and
pullers.
• There are basically two types of pulling machines used in the construction of transmission lines being strung under tension. These are defined as bullwheel and drum/reel-type.
• Pullers should be equipped with load-indicating and load-limiting devices.
• Tensioners should be equipped with tension indicating devices. The capacities of the puller and tensioner should be based on the conductor, span length, terrain, and clearances required above obstructions.
• Sag tensions should never be exceeded during stringing. Required capacity for both puller and tensioner can be calculated as mentioned in IEE 524.
• Positive braking systems are required for pullers and tensioners to maintain conductor tension when pulling is stopped.
• The pulling and braking systems should operate smoothly and should not cause any sudden jerking or bouncing of the conductor
TENSION STRINGING – TOOLS AND PLANTS
• The following tools and plants are normally used. • TSE Set (Tensioner & Puller of 8t/15t capacity). • Running block for conductor
• Running block for Earthwire • Head Board
• Pilot wire each of 800m length • Pilot wire joint
• Ground roller for tension/Manual stringing
• Wire mesh Pulling grip (One end open) for conductor • Wire mesh pulling grip (One end open for earth wire) • Wire mesh pulling Grip (Both ends open) for Conductor • Articulated joints
• Drum Mounting jack for conductor drum of 10T capcity • Turn Table (5t capacity) Anchor plate with Anchor pins
• Hydraulic compressor machine of 100t capacity with die sets • Travelling Ground
• Dynamometer(10t, 2t) • Pilot wire reel stand
• Four sheave pulley with wire rope.
• Equalizer pulley contd…….
TENSION STRINGING – TOOLS AND PLANTS
• Conductor lifting Tackle
• Winch machine(Motorised/Manual)
• Come along clamp for conductor(Bolted & Automatic) • Comealong clamp for Earthwire(Bolted & Automatic) • Turn Buckle (10T, 3T)
• Sag Board • Marking Roller • Mismatch Roller • Joint protector • Walkie Talkie set
• Theodalite with stand
• Hydraulic conductor cutter • Flags(Red & Green)
Hydraulic Tensioner (YK-YZ30A)
Details
• □ Essential parameter
Maximum Tension(kN):30
Continuous Tension(kN):25
Maximum speed (km/h):5
Bullwheel bottom of groove dia
meter(mm):Φ1200
Number of grooves:5
Maximum pullback (kN):20
Maximum suitable conductor di
ameter (mm): Φ32,
Engine power /speed (kW/rpm)
:11/2200
Dimensions (mm): 3560 ×1600
×2220
Features of Tensioner (YK-YZ30A)
1. Bullwheel with wearproof MC nylon lining segments.
2. infinitely variable tension control and constant tension conductor stringing . 3. it adapt Italian reducer .
4. spring applied hydraulic released brake acts automatically in case of hydraulic failure to ensure safety
□ Main component :
1. Engine :Domestic water –cooled engine .
2 .Main pump/motor ,Chinese famous branded pump and motor . 3. Reducer :RR(Italian )
4. Radiator: AKG
5. Hydraulic instrument : WIKA 6. It can choose import engine Uses:
It adequate to tension releasing various conducts and earthwires .and also useful for tension releasing OPGW optic cable compounded earth wire and ADSS self–
Hydraulic Puller (YK-YQ30)
• Essential parameter
• Maximum linepull (kN):30 • Continuous linepull (kN):25 • Maximum linespeed (km/h):5 • Bullwheel bottom of groove
diameter(mm) :Φ300
• Bullwheel grooves number : 7 • Maximum suitable steelrope
diameter (mm): Φ13
• Maximum through connector diameter (mm): Φ40
• Engine power /speed (kW/rpm):31/2200
• Dimensions(mm):3200×1600×2000 • Weight (kg): 1500
Features of (YK-YQ30):
• 1. Infinitely variable speed and line control ,the pull in the rope
can be read on the line pull gauge .
• 2. The max pull for conductor –stringing operation can preset
,automatic overpull protection system .
• 3. Spring applied –hydraulic release brake acts automatically in
case of hydraulic failure ensure to safety .
• 4. Attached reel winder with automatically level wind .load and
unload conveniently .
• □ main component :
• 1.Chinese famous diesel engine.
• 2. Main pump:SAUER –SUNDSTRAND pump .main motor : SAI
techniques product .
• 3. Radiator:AKG
• 4.Hydraulic instrument:WIKA
Stringing tools
Pulley
Automatic clamp bolted-type-clampChain pully block
compression die sets
Engine-winch-machine-diesel-5-ton-capacity hydraulic-compressor
Equalizer-pulley Eye-type-four-sheave pulley Four-Sheave-pulley hydraulic-cond-cutter- two-cup-up-to-40mm-dia-acsr kitto-clamp open-type-single sheave-pulley
OPGW-Cable-Comealong patta clamp
pilot wire reel
sag scope sagging-pulley single-rope-pulley snatch-pulley
snatch-type-steel-pulley swivel-joint & connector
turn-table-with-breaking
HELICOPTER METHOD
• Conductor will be strung directly from the helicopter; as
• a result, most transmission line work will be performed
• without touching the ground or encroaching on the
• right-of-way.
• An aerial utility contractor will be hired as needed during
• each project’s conductor installation phase. Helicopters will
• fly in close proximity to the new transmission structures.
Helicopter stringing overview
• 1. Utility linemen will be transferred to each structure via the helicopter; they will then hang stringing wheels on each arm of the structure.
• 2. Rope is then hooked onto the helicopter and pulled through the stringing heels for about 20,000 feet. Wire
• rope is then connected and pulled back the opposite way through the stringing wheels.
• 3. Conductor is then pulled back through the stringing wheels using a machine located on the ground (conductor is too heavy to be pulled by the helicopter).
• 4. Using the helicopter, the stringing wheels are removed from each arm while
attachments, including dampers to minimize vibration on the conductor, bird diverters and spacers, are added.
B
enefits
• Stringing transmission conductor using helicopters has numerous benefits, including: • Decreases total project construction time
• Allows work in remote or inaccessible locations • Reduces environmental impact
• Minimizes right-of-way intrusion • Minimizes matting in sensitive areas
A utility lineman attaches a spacer between transmission conductor
A utility lineman
suspended from a cable attached to a helicopter hangs a stringing wheel.
Working from a platform attached to a helicopter, a utility lineman attaches
a spacer between transmission conductor
A utility lineman prepares to attach a spacer between transmission conductor
STRINGING
• Steps involved
– After ensuring the tightness of all the bolts and
nuts the following activities will be started.
– Insulator hoisting along with aerial rollers
– Earthwire stringing
– Paying out the pilot wire
What are the issues arise at the time of stringing
During stringing what should be strung first
…
Significance of earth wire stringing
How should be jumper arrangement in various
types of T/M lines ?
DRUM SCHEDULING
OBJECTIVE
• Effective utilization of the conductor
• To prevent Wastage of the conductor.
INPUTS
• Details of Tower Schedule
• Standard length of each drum.
• Receipt of Drums Details
BASIS:
• Knowledge of Usage of cut lengths for Jumpers and Short Spans.
• All the joints or splices shall be made at least 30 metres away from the tower
structures.
• No joints or splices shall be made in spans crossing over main roads, railways
and small river tension spans.
• Not more than one joint per sub conductor per span shall be allowed
.• Conductor drums have to be transported to the tensioner site as per the approved drum schedule for the section to avoid wastage and small bit lengths being left over.
• The selection of drum shall be such that no mid span joint will come within 30mtrs of any tower
HANDLING OF CONDUCTOR AND EARTHWIRE
• Handling and transporting of the conductor and accessories shall be carried out in such a manner as to minimize the possibility of damages from abrasion through rough handling or dirt and grit and getting into the reel of the conductor by touching or rubbing against ground or objects, causing injury to the conductor etc.
• Particular care shall be taken at all times to ensure that the conductor do not become kinked twisted or abraded in any manner. If the conductor is damaged, the section affected shall be
replaced or repaired by putting joint or using repair sleeves or polishing with emery cloth, so as to give satisfactory performance.
• The conductor shall not be over strained during erection. The conductor shall be run out of the drums from the top in order to avoid damage due to chaffing.
• Drum battens shall not be removed until conductor drums are properly mounted at the drum station on the line, and battens shall be immediately refitted on the drum if any surplus conductor is left thereon.
• Drums will be transported and positioned on station with the least possible amount of rolling, immediately after running out, the conductor shall be raised at the supports to the level of the clamps and placed into the running blocks.
• The grooves of the running blocks shall be of a design that the seat is semi-circular and larger that the diameter of conductor/earth wire and it does not slip over or rubs against the sides.
• The grooves shall be lined with hard rubber or neoprene to avoid damage to conductor and shall be lined with hard rubber or neoprene to avoid damage to conductor and shall be mounted on well oiled bearings.
• At all stages of construction proper care shall be taken so that the conductor surface is smooth enough to give satisfactory corona and radio interference performance. Contd…..
HANDLING OF CONDUCTOR AND EARTHWIRE
• The running blocks shall be suspended in a manner to suit design of the cross-arm. • All running blocks specially those at the tensioning end, will be fitted on the cross arms
with jute cloth wrapped over the steel works and under the sling to avoid damage to the slings as well as the protective surface finish of the steel work.
• In case, section towers are used even for temporary terminations, if this be unavoidable, they shall be well guyed and steps shall be taken to avoid damage.
• The drums shall be provided with a suitable breaking device to avoid damage, loose running out and kinking of the conductor.
• The conductor shall be continuously observed for loose or broken strands or any other damage.
• When approaching end of a drum length at least three coils shall be left when the stringing operations are stopped.
• These coils shall be removed carefully and if another and if another length is required to be run out a joint shall be made as per the recommendations of the conductor
manufacturers.
• Normally, the joints shall be so made that these are not required to pass through running out of blocks, the joints will be protected with suitable joint protector sleeves.
T&P for OPGW
Tensioner Puller
Swivel
Basic controls for OPGW stringing
• Strict controls must be established during installation to ensure that it is
performed correctly, without excess tension, twist of the OPGW,
unsuitable compression, regulating a correct sagging. Neither the fibers
nor the aluminum tube will be damaged
• The tensioner and the puller should be placed at a distance from the first
tower pulley which is equivalent to at least twice the height of the pulley.
• No obstacles must prevent the pulleys from rotating in the correct way.
Stringing speed:
• Stringing speed about 60 m/min, depending always on the environmental
conditions and the topology of the overhead line.
• pulling tension shall be lower than 1.5 times the weight (kg) of 1 km
OPGW cable length
.
INSTALLATION PROCEDURE FOR OPGW FIBER OPTIC CABLES
• OPGW Cable with optical fiber are similar to those used for installation of the standard ground wire cable special care should be taken to avoid any damage to the fibers by observing the minimum bending radius at all times
• Therefore, specific components and machinery are used for the OPGW cable: pullers, tensioners, anti twisting counterweights, swivels, pulling grips, pulley-blocks, self-gripping clamps, pulling ropes, pulling cables, etc
Survey of the line:
• The OPGW drum lengths are determined based on the following considerations:
position of the tension towers, tower access, distance between supports and crossing with other lines, roads, railways, routes, services and other obstacles.
• The position of the splices depends on the maximum available length of OPGW, on the position of the towers and the tower access.
Transport, loading, unloading and storage
:
• The drums should always be transported in vertical position with the cable ends
fixed to prevent cable from slackening. All of the staves and/or safeguards should
be maintained until the drums are situated for immediate installation.
• After the transport, the drums should be inspected to verify that they have not
been damaged and that none of the staves and/or safeguards are broken.
• The drums should never, under any circumstances, be thrown from the lorry
during unloading, nor moved by uncontrolled rolling.
• Loading and unloading are performed so that the drum ream ins in vertical
position and the sides of the drum are not damaged.
• The drums can be moved by rolling a short distance ensuring that there are no
objects that may damage the staves. The direction in which the drum turns
should be the same as that in which the cable is wound during manufacture.
• The drum should not be stored on its side under any circumstances whatsoever.
• The ends of the cable should be sealed to prevent water penetration.
• The drums should be stored on flooring that is strong enough to prevent sinking.
• The drums should be stored to facilitate handling and loading. They should be
Positioning the equipments
The drum must be located at a distance of 2 or 3 metres from the tensioner. The lifting components usually used are hydraulic jacks and a bar with the suitable dimensions inserted in the central opening of the drum. The drum must be located at a height of 10 to 15 cm from the ground.
Puller and tensioner
Either the puller and the tensioner must be placed at a minimum distance from the tower equal or greater than 2 times the height of the tower. The tensioner as well as the puller should be placed aligned with the conductors. The
maximum acceptable deviation angle is 30º. (a < 30 º see Figure)
If it is not possible to achieve this angle, the puller and/or the tensioner are placed close to the following tower, using an additional pulling cable of the required
length.
90º or less retracking of the optic cable is not allowed.
The tensioner as well as the puller should be positioned at a minimum distance equivalent to twice the height of the support to which the cable is fastened.
Positioning the equipments
The tensioner must be equipped with a dynamometer (i). Its reels must be
protected with material that does not damage the outer layer of the OPGW cable.
The puller must also be equipped with a dynamometer with automatic
disconnection in case of over tension on the cable.
The pulling cable should be joined to the OPGW cable by a swivel and a pulling
grip
• The minimum diameter of the reels (where the OPGW is to be coiled) used during
the installation should be at least 80 times the diameter of the OPGW cable, with
no need of exceeding 1500mm. For example, the tensioner reels for a 15mm
cable should have a diameter of approximately 1.2 meters.
In the tensioner, the first groove the cable will pass through must be
perpendicular to the axis of the drum. A double armour OPGW in the tensioner it
will enter from the left and leave from the right for right-hand lay sense (and from
the right and leave from the left for left-hand lay sense).
Ground connection of the OPGW
the breaking device and the puller have to be suitably connected to the ground by a system of moveable rollers
Ground connection of the OPGW cable at the tensioner outlet
Anti-twisting devices
• When a single or double layer OPGW cable is installed, an anti-twisting system is required to compensate the inherent effect of torque of the OPWG cable.
• This device is always positioned at the pulling head of the OPGW cable and equipped with two counterweights placed at a distance that is at least 3 meters one from the other.
• In this way that when one counterweight goes through the pulley the other is operative. • Another anti-twisting device is installed at the end of the OPGW cable just before it leaves
the tensioner.
• The weight of the anti-twisting devices has to be high enough to prevent OPGW cable rotation.
• The minimum values recommended for each counterweight are as follows: • - Spans <300 m 12 kg
• - Spans 300 m - 700 m 15 kg • - Spans > 700 m 20 kg
• For Installation length longer than 4000 meters these values should be increased by 5 kg. • Special precaution must be taken in order to not rotate the cable inside the
counterweights, due to unsuitable or incorrect tightening, during tightening process special attention has to be taken on using the appropriate clamp range and correct installation procedure, in order to not damage the OPGW cable
STEPS OF STRINGING:
The stringing procedure is broadly divided into the following steps:
• Paying out & stringing of conductor.
• Paying out & stringing of earthwire
• Final sagging of earthwire and conductor.
• Clipping and fixing of accessories
.
What is guying ?
GUYING OF TOWERS
• Before commencing of stringing, the angle towers where the stringing is to be started have to be provided with guy supports for all the phases.
What are the precautions which should be taken at the time of guying?
• The guys used generally are 20 mm steel wire rope. The guys are attached to the tower at the tip of the cross arm , to the strain plates with suitable D-shackles. • The guys are anchored in the ground at an angle of 45 deg. or less from the
horizontal, attached to dead end anchors .
• The guy wire is attached to the dead end anchor wire with the help of turn buckles of 10 tons capacity.
• After pulling up the slackness in guy, it is tightened by the turn buckle.
• Excessive tightening of guy should be avoided. It is advisable to tighten the guy progressively at the time of rough sagging of the conductor.
INSULATOR HOISTING :
• In 132 KV and 220 KV transmission lines, suspension insulator strings are used on all suspension 'A' type towers (upto a deviation of 2 degrees) and tension insulator strings are used on 'B' and 'C' type Tension towers.
• In 400 KV lines V-type insulator strings are used on all suspension A-O and A-5 towers (up to a deviation of 5 degrees). Double tension insulator strings are used at all B-30, C-60 and DE type Tension towers.
• The number of insulator units to be used on various types of strings are vary.
• Double suspension insulator strings are used in 132 KV & 220 KV lines on Suspension towers of River and Power line Crossings only.
• Double Tension insulator strings are used in 132 KV & 220 KV lines on Tension towers of Railway, River and Power Line Crossings only
INSULATOR HOISTING:
PRECAUTIONS:
• 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 cloth free from
grease and oil.
• Insulators shall be checked for any chipping or crack and shall be replaced
with new one.
• 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 hardware of the string on the tower side is assembled and joined to the
first insulator by ball eye.
• The bottom insulator is joined to the twin moose roller. 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 is passed through the pulley.
• Both the end of the rope is brought to the ground. One end of the rope is
firmly tied below the 3rd or 4th insulator. The complete string with 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.
Precautions shall be taken for hosting of insulator strings:
• i.)The insulator strings shall be assembled on the ground before hosting.
• ii.)The strings shall be fixed on the towers just prior to the stringing of conductors. • iii.)It shall be ensured that all current carrying parts are smooth and without dirt, grit,
cuts, abrasions, projections etc.
• iv.)Damaged insulators and strings shall not be used in the assemblies. Insulators which have cracks or chip or those having glazing defects exceeding half a centimeter Sq. shall not be used
• v.)Before hosting all insulators shall be deemed in a manner that will not spoil, injure or scratch the glaze of the porcelain, but in no case shall any oil be used for this
purpose.
• vi.)Security clips shall be placed properly in position for the insulator assemblies before hosting.
• vii.)For 132 KV and 220 KV lines in suspension strings the arcing horns are used on line side only and in tension strings the arcing horn are used both on line and tower sides • viii.)Arcing horns and Anti-corona rings shall be fitted as per recommended practice of
Way of fitting of C.C. RINGS &
GRADING RINGS ?
PAYING OUT OF PILOT WIRE:
• A pilot wire is used to pull the conductor. The pilot wire is
initially laid through the centre wheel of the roller.
• A 12 mm dia pilot wire is generally used for pulling of twin
moose conductor.
• The pilot wire can be laid length by length and joined with pilot
wire connectors or it can be pulled from one side of the section
after each drum is paid out.
• At power line crossings, the pilot wire is laid from both sides
and free ends are joined after obtaining the shutdown of
power line.
• Scaffolding shall be provided for P&T and road crossing before
paying out of the pilot wire.
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.
• Both the machine should be securely anchored.
• Reel winder shall be positioned at a convenient distance
behind the puller.
• The distance of the drums from the tensioner shall be at
least 25 to 30 mtrs.
Puller and tensioner operating characteristics :
• Semicircular grooves with depths in the order of 0.5 or more times the conductor
diameter and with flare angles in the order of 5° to 15° from the vertical generally
have been found to be satisfactory for stringing.
• The number of grooves in the bull wheel must be sufficient to prevent the outer
layer of wires of multilayer conductors from slipping over underlying layers.
• In order to avoid loosening of outer layer of strands as it passes on bull wheel, for
normal conductors having a right-hand direction of lay for the outer wires, bull
wheels should be arranged so that, when facing in the direction of pull, the
conductor will enter the bull wheel on the left and pull off from the right side and
will enter the bull wheel on the right and pull off from the left side for normal
conductor with outer layer having left had direction of lay.
• The material and finish of the grooves must be such as not to damage the surface
of the conductor.
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 same way as the conductor
will pass during running. The ropes are connected to the
conductors.
• The rope is pulled by starting the tensioner at low pay
out tension to pass the conductor through bull wheel
and are brought out through the guide rollers.
• The pilot wire is attached to the other end of conductor
with swivel joint.
PAYING OUT OF CONDUCTOR:
• At the puller side, the pilot wire is pulled to remove
slackness using the reel winder. The wire is passed
through bull wheel of the puller and connected to the
reel winder machine.
• The tensioner can be initially set for a tension of 2 to 2.5
tonnes.
• The puller is started to draw up the pilot wire until the
bull wheels of the tensioner start moving.
• The tension in the tensioner must be adjusted so that the
conductors travel well over the ground.
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 other end.
• Double tension string assembly is assembled with insulators and
hardware and hoisted to the cross arm.
• The dead end cone is compressed on both the sub conductors ends.
The conductor is held by come-along clamps at a distance of 5 to 6
mtrs.
• From the dead end cone and with the help of a pulley connected to
a ground anchor, the conductor is pulled to slacken the free end of
the conductor.
• By holding the conductor with pulley, the dead end cones are
attached to the tension string. The pulley is slowly released. the
come-along clamp and pulley etc. are removed.
STRINGING – ROUGH SAGGING
• Pilot wire is connected to the conductor throuh head
board.
• Pilot wire will be pulled with the help of puller by
maintaining required tension on the conductor with
the help of Tensioner.
• Conductor will be pulled up to the rough sag level.
• Will not be allowed at rough sag level for more than
STRINGING OF EARTHWIRE:
• Paying out of Earthwire:
• Normally stringing of earthwire is done manually since handling of earthwire is easy and it does not get damaged easily.
• First, earthwire rollers are provided on the earthwire peaks of all the suspension towers in the section.
• A lineman/fitter may be kept on each tower to ensure free running of rollers with red and green flag and whistle.
• Earthwire is pulled from tower to tower manually or by using tractor.
• After reaching the next tower the earthwire is passed through the suspended earthwire rollers with the help of a polypropylene rope and paying out is
continued further.
• After one length of earthwire reel is exhausted, the second length of wire is paid out for the balance section.
• Midspan joint for earthwire is compressed on the ground joining the two lengths.
