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) Crow bar (1.8m length)
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 Weight(kg):1700
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– stand optic cable .etc
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 5.Mating with model GSP950 drum
Stringing tools
Pulley
Automatic clamp
hydraulic-compressor machine-motorised
bolted-type-clamp
compression die sets
Chain pully block
Engine-winch-machinediesel-5-ton-capacity
Equalizer-pulley
Eye-type-four-sheave pulley
hydraulic-cond-cuttertwo-cup-up-to-40mm-diaacsr
kitto-clamp
Four-Sheave-pulley
open-type-single sheave-pulley
OPGW-Cable-Comealong
patta clamp
pulley-blocks pilot wire reel
sag scope
snatch-typesteel-pulley
sagging-pulley single-rope-pulley
swivel-joint & connector
turn-table-withbreaking
snatch-pulley
Turn-buckle-3t-10t
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.
Benefits • • • • • •
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 – Positioning of Stringing equipment
SPACER TROLLY ARRANGEMENT
What are the issues arise at the time of stringing
?
During stringing what should be strung first…
Conductor/ earth wire ?
Significance of earth wire stringing
What is the effect of stringing earth wire first
?
How should be jumper arrangement in various types of T/M lines ? What is the method for measuring jumper ?
DRUM SCHEDULING
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
DRUM SCHEDULE
TOWER SCHEDULE
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.
OPGW(optical ground wire)system:
T&P for OPGW
Swivel Tensioner
Pulley
Puller
Pulling grip
Anti-twisting devices
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, selfgripping 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 located far from any activity that may damage them.
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
What are the precautions which should be taken at the time of insulator hoisting?
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 the manufacturer/supplier.
Way of fitting of C.C. RINGS & GRADING RINGS ?
C.C. RING
GRADING RING
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.
PAYIONG-OUT OF CONDUCTOR
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 96 hours.
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.
How Final sag is done? What are the various steps involved ?
Temperature difference should be considered or not during final sag ? What are the consequences of not changing the sag board for overall day temperatures?
FINAL SAGGING OF CONDUCTOR: • The sagging of the conductor shall be done using sagging winches. After being rough sagged the conductor shall be allowed to hang in the stringing blocks for more than 96 hrs. 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.
Preparation of Stringing Chart • Eq. Span less than Normal Span 32 deg.C No wind condition.
• Eq. Span more than Normal Span 32 deg.C Full wind condition.
Catenary curve
Preparation of Stringing Chart • Eq. Span less than Normal span – For conductor • All the calculation shall be based upon maximum working tension of 3614 kgs at 32 deg. C and no wind pressure provided that tension of 8048 kgs at 32 deg. C and 161 kg/sqm. Wind pressure is not exceeded.
– For Earthwire • All the calculation shall be based upon maximum working tension of 1212 kgs at 32 deg. C and no wind pressure provided that tension of 3360 kgs at 32 deg. C and 200 kg/sqm. Wind pressure is not exceeded.
Preparation of Stringing Chart • Eq. Span more than Normal span – For conductor • All the calculation shall be based upon maximum working tension of 8048 kgs at 32 deg. C and 161 kg/sqm. Wind pressure provided that tension of 3614 kgs at 32 deg. C and no wind is not exceeded.
– For Earthwire • All the calculation shall be based upon maximum working tension of 3360 kgs at 32 deg. C and 200 kg/sqm. wind pressure provided that tension of 1212 kgs at 32 deg. C and no wind is not exceeded
STRINGING – FINAL SAGGING • Sag boards are tied. • Final sagging will be carried out with the help of winch machine. • Check the final sag. • Mark the conductor. • Connect to the tower with the help of tension clamp
STRINGING – CLIPPING & SPACERING • After completion of final sagging. • Clipping work will be carried out at all the suspension towers. • Spacers will be placed as per the spacer placement chart.
FINISHING ACTIVITIES – STEPS AND PRECAUTIONS • CLIPPING AND SPACERING – Before taking up clipping, the conductor should be earthed to avoid any electrical hazards. – Conductor should be marked properly to ensure the verticality of the insulator string after placing the suspension clamps. – Ensure to provide specified No. of armour rods.
FINISHING ACTIVITIES – STEPS AND PRECAUTIONS • All the other components of suspension clamps have been properly provided as specified • None of the components of suspension clamps is damaged. • All the bolts & nuts have been properly tightened. • All the split pins have been provided
FINISHING ACTIVITIES – STEPS AND PRECAUTIONS • SPACER FIXING – Spacers shall be provided as per approved placement chart. – Necessary precaution shall be taken while crossing any LT/HT line. – All components of the spacer shall be properly fitted as per the approved drawing. – None of the components shall be damaged.
• Requisite No. of retaining rods are provided. • All bolts & nuts are properly tightened
What should be the jumper arrangement in various types of T/M lines?
What is the method for measuring jumper ?
• • • •
– Ensure proper earthing – Length of the jumper shall be carefully measured to ensure the parabolic shape with requisite live metal clearance and the jumper drop. – Ensure the sub conductor lengths so that jumper lies in horizontal position. Jumper cone shall be compressed as per the approved drawing. All nuts and bolts shall be properly tightened. Spacers shall be provided as per specifications. Ensure correct No. of insulators in the pilot insulator strings and use balancing weights if required
FINISHING ACTIVITIES – STEPS AND PRECAUTIONS • Jumper cone shall be compressed as per the approved drawing. • All nuts and bolts shall be properly tightened. • Spacers shall be provided as per specifications. • Ensure correct No. of insulators in the pilot insulator strings and use balancing weights if required.
FINSHING ACTIVITIES – FINAL CHECKING • Once the line is completed in all respects final checking of the line is to be carried out to identify balance left over works and attend the same immediately. • As per POWERGRID’s practice a team comprising of Executives/JEs , Technicians shall be assigned to check the line thoruoughly to identify any defects as per the prescribed format.
FINISHING ACTIVITIES – FINAL CHECKING • The following are normally checked during the final checking. • Backfilling is complete • Coping is completed • Earthing is completed • Left over soil of the excavation is uniformly distributed.
FINISHING ACTIVITIES – FINAL CHECKING • • • •
Any missing/buckled tower members All the dummy holes are bolted or not All the bolts & nuts are fixed All the statutory requirements such as NP/DP/PP/ACD’s are fixed or not. • Any broken insulators are existing. • Correct No. of insulators used
FINSHING ACTIVITIES – FINAL CHECKING • All the hardware fittings are fixed • Jumpers are properly placed and their clearance is in order • Requisite No. of armour rods are provided at suspension clamps. • Check all the cotter/split pins are provided. • Damages to the conductor.
FINISHING ACTIVITIES – FINAL CHECKING • Requisite No. of spacers are provided. • Minimum Ground clearance at the nul point. • Vibration dampers are fixed as per the damper placement chart. • Any damages to the earthwire and its fittings. • Earth wire VD are placed as per the placement chart. • All the copper bonds are provided.
FINISHING ACTIVITIES – FINAL CHECKING • Any trees are existing in the right of way. • Minimum clearance is available at power line/NH/Railway line crossings etc. • Any deviations shall be recorded and signatures of both the checking person and the representative from construction department shall sign the formats.
FINISHING ACTIVITIES – FINAL CHECKING • All the defects identified by the final checking team are to be attended by the contractor. The same shall be ensured by carrying out the final checking of the locations where defects are identified before giving submitting the application for final charging to CEA.
• Thank you….
