OS-Sup-15-June-NR-II-2009-10s21Hot_Line_Presentation tools & 220 KV Sy

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POWERGRID, NR-II WELCOMES YOU

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A PRESENTATION On Behalf Of NR-II, Jammu ON HOT LINE MAINTENANCE TOOLS DESCRIPTION AND 220 KV DOUBLE CIRCUT

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1.0 HOT LINE MAINTENANCE 1.1 It may not be always possible to get a shut down of one or both the circuit of the transmission line as sufficient redundancy in transmission system is not available in Indian Power System. In such event the only solution is to go for hot line maintenance. Hot line maintenance as the name implies, working on transmission line while it is hot or live to inspect and replace, if necessary, defective components so as to avoid a sudden breakdown which may occur if the line with a particular defect remain unattended for a longer time.

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1.2 Initially hot line maintenance was restricted upto 22 kV by employing wood poles. However with the advancement of technology wood poles were replaced by new light weight epoxy glass handle for hot line tools. By 1964 these new hot line tools were employed for hot line maintenance for EHV lines in USA and Canada quite extensively.

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2.0 Hot Line Maintenance Methods Hot line maintenance work on live line can be done by one or other of the following methods 2.1 Hot stick method using insulated sticks. In this method the linemen is at the ground potential and is isolated from the energized conductor. This method is generally adopted for transmission lines upto 220 KV. 2.2 Bare hand technique – In this method linemen works either from the insulated bucket / truck or ladder and is bonded to the energized conductor and isolated from the ground. This method is generally employed for transmission lines above 220 kV. 2.3 A combination of the above methods

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3.0 Hot Line Operations Some of the hot line maintenance operation that can be carried out are given below: Changing of insulators Replacement of damaged section of conductor Testing of insulators (on-line insulator tester) Changing of cross arm Changing of poles Transferring conductor to higher pole In India the hot line maintenance operation have been restricted to changing of insulators, testing of insulators replacement of damaged section of conductor.

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4.0 Hot Stick Method Design Considerations 4.1 Safety and welfare of the linemen are the prime consideration while designing the hot line tools. The major characteristics required of the tools are: Perfect insulation and strength for the safety of the linemen Light weight and ease of maneuver ability for reducing the fatigue on the workmen Precision and finish are of secondary importance. In U.S.A. and Europe, the hot line tool manufacturer, the hardware manufacturer and transmission line construction engineer work together to coordinate tools, hardware and transmission lines for maximum efficiency

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4.2 The hot line tools consists of two parts i) The tool head which is the actual tool required for the various operations and ii) hot stick on which the tool head is to be mounted. In earlier days the hot sticks were made of spruce wood painted in varnish. However with the advent of the technology the wood has been replaced by epoxy glass handle. In addition to exceptional insulating qualities the epoxy glass has excellent resistance to moisture, chemical attack, and weathering. It has high mechanical strength, is durable and required a minimum of maintenance with no periodic drying time as required of wood tools

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5.0 Hot Line Tools The tools that are normally used for hot line maintenance operations, besides the hot stick are as under 1. Wire tongs - Normally used on pin type or suspension type construction for maneuvering and holding live conductors clear of the working area or for transferring to conductors to knee positions 2. Wire tongs saddle – are used to secure wire tongs to a structure 3. Tie stick - used for manipulation of the wires 4. Strain link sticks -used principally for supporting heavy conductor loads either for assisting wire tongs or for supporting entire load when changing insulators on running corners and dead end structures.

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5. Roller link sticks – used principally to hold conductors aside when relocating poles in mid span 6. Suspension link sticks – principally designed for lifting the conductor to relieve the strain from suspension insulators on high voltage lines 7. Strain carrier – used principally for relieving the strain on conductors when changing insulators on dead end structure. 8. Auxilary arms – used principally for holding conductors while damaged conductors or cross arms are being changed on pole structure. 9. Double string dead end insulator tool – normally used to remove the strain from the one side of the double insulator strings. 10.Gin poles – Used for lifting heavy conductors , hoisting transformers switches and other heavy items around energized conductors and other objects.

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11. Cum-a-along-clamp - normally used to grip the conductor when tension is applied to the clamps by rope blocks, link sticks etc. 12 Safety equipment like conductor guards, cross arm guards, insulator covers, hand gloves etc. 6.0 Safety Measures 6.1 A golden rule for hot line operation is "nothing is too safe when a life is at stake". Records prove that hot line work on high voltage lines is actually safer than maintenance work on "Cold" lines which could possibly become energized while the line is being worked. Linemen working with hot sticks are always conscious of the danger involved, and being aware of this danger they work more cautiously and keep a safe distance

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6.2 SAFE DISTANCE FOR WORKING The person going on the hot line with the help of the ladder, before reaching the conductor touches the clamp, connected to the conductive strap on his conductive suit, to the conductor, remaining at certain distance so that his whole body reaches the voltage of conductor before he reaches the conductor. With this step the person remains free from effects due to the voltage difference in the electric field. While working it should be kept in mind that the person working invariably keep a certain distance from the earth point. In addition to this he should also keep a certain safe distance from the other phases of the lines.

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Voltage Minimum Distance Limit Ph to Earth Phase to Phase Ph to Ph Meter Feet Meter Feet (KV) 30-35 0.7 2’4’’ 0.7 2’4’’ 35.1-46 0.8 2’4’’ 0.8 2’4’’ 46.1-72.5 0.9 3’.0’’ 0.9 3’.0’’ 72.6-121 1.0 3’4’’ 1.4 4’6’’ 138-145 1.1 3’6’’ 1.5 5’0’’ 161-169 1.2 3’8’’ 1.7 5’8’’ 230-242 1.5 5’0’’ 2.5 8’4’’ 345-362 2.1 7’0’’ 4.1 13’4’’ 400-450 2.73 9’0’’ 5.87 16’4’’ 500-552 3.4 11’0’’ 6.1 20’0’’ 700-765 4.6 15’0’’ 9.4 31’0’’

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6.3 Other safety measures are  1. Use freely safety equipment like cross-arm guards, hand gloves, etc. 2. Never use a tool which is not tested and which is not familiar 3. Never use a damp tool 4. Do not exceed the manufacturer’s ratings in the use of hot line tools. Linemen must know the approximate weight of a conductor span and the line tensions which they are dealing with. When in doubt use a longer tool or two identical tools. 5. Check each tool regularly for indicating that the tool may have been overstressed 6. When not in use, tools should be kept in the tool container and not on the ground 7. All the hotline tools shall be inspected manually and electrical strength test shall be carried out as per design at site. 8. All the insulator in the string must be healthy except one or two depending on voltage class

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9. Altitude correction factor should be applied in the above electrical clearances 10. Distance from inadvertent movement shall be considered depending on the work procedure and expertise of the lineman 11. Permissible current in the energized tool is 1 micro amp per kV line to ground 12. Difference in current of two adjacent tools should not be more than 20% of the small value 13. If auto-recloser is installed the same should in manual mode Always remain cool and unruffled under any circumstances while working on a hot line

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7.0 Procedure For Hot Line Maintenance Work In 220 KV Double Circuit Suspension Tower (Middle Phase) Using Trolley Pole By Hot Stick Method 7.1 This procedure involves the main job of replacement of damaged insulator string (I-type) in 220 KV D/C Suspension Tower (Middle Phase). However some additional work can also be attended such as tightening of nut bolts of corona ring, vibration damper including replacing them. 7.2 T&P Required First segregate following tools for making sub-assemblies of tools at ground. The following sub-assemblies of tools shall be required to carry out the assigned job

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(a) Capstan sub-assembly: consisting of following tools     1. Capstan hoist with foot switch 2. Capstan mounting base 3. Two capstan base chain binders 4. 1000 lbs snatch block with sling 5. Extension cords 6. Generator (b) Trolley Pole Sub-assembly: consisting of following tools      1. Two tower saddles with extension and 2 ½" clamp or two Samson rope slings (5/8" dia., 9 ft long each) 2. One trolley ridge pole 3. One trolley pole with insulator retaining plate 4. One trolley tag rope (poly decron) – 150 ft. (1/2" dia) 5. Tandem trolley wheel 2 ½" with pole clamp 6. On swivel stick – 12 ft. 7. 2 ½" dia. Pole clamp (extra)

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(c) Additional tools required: 1. One hand lines complete (600 ft.) with hand line blick, hand line hook and swivel snap. Two extra hand line blocks Six nos. 10 ft pegging sling 4 to 5 nos. endless nylon sling 1 to 2 extra tool buckets containing small tools screw drivers, extra 6 ft. long pegging sling, piler and cutter Conductive gloves, socks and boots each for all crew members working on tower Safety belt for each line man on the tower Two strain link sticks with tower saddle and rope blocks Four wire-tongs with tower saddles and rope blocks / chain hoists 10. Helmets for all crew members 11. One snatch block 2500 lbs capacity 12. One bull line rope (600 ft.) 13. Two no tool racks

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Two no. tarpaulin sheets 12’ x 12’ size One "Y" Ball Clevis One Spliced Universal Stick (18’) fitted with Shepherd hook Silicon wiping clothes – 6 pieces Moisture eater – 1 gallon One shunt Universal tools and hot stick Locating pin All angle plier 7.3 Procedure: Install the capstan at tower leg about 5 ft. above the ground level under working phase. A line man shall climb on tower carrying hand line and 1000 lbs snatch block and install be block at suitable position on the cross arm for lifting the required tools over the tower. Contd:

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Contd: The position of hand line block should such that during operation hand line will remain at least 3 mtrs away from the conductor at all time Other crew men shall also climb on tower . Fix hand line with the help of hand line block and one endless nylon sling. Send up spliced universal stick with a shepherd hook attached at one end, a line man shall measure the clearance between upper conductor and the tower cross arm where he has to work. Minimum 10 ft. clearance from the lineman head sitting on the tower cross arm to overhead conductor is required. If the required minimum clearance is not available, do the following arrangement. Precaution: The man working at the tower cross arm shall maintain adequate clearance from upper conductor always

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Send up two wire-tongs 22 ft long 3" dia. Saddle and its attachment. Fix-up saddle for each wire-tongs on tower structure for holding the conductor by each wire-tong. The wire tong should be attached with conductor both side of suspension insulator string. Push the wire-tongs with the help of chain hoist or rope block. The insulator string just above the working phase shall swing away thus making adequate clearance for man sitting under this phase and working at tower cross arm. Precaution should be taken that string swing angle should not be beyond 30 Deg. Measure the clearance from upper conductor to lower cross arm where man has to sit, if the adequate clearance is available, job shall be done otherwise not. Send up the trolley ridge pole along with tandem trolley wheel. The trolley ridge pole shall be fitted with tower member by tower saddles at its both ends, it can also be tied up with ¾" dia., 9 ft Samson Rope pegging sling at two ends.

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The tandem trolley wheel shall be untied from ridge pole and suspended over it, clamp is also opened to insert trolley pole in it 8. Send up trolley pole sub-assembly (at one end of trolley pole insulator retaining plate attached and at other end swivel stick 10ft. attached with tag rope ½" dia., 150 ft. long). This trolley pole sub-assembly shall be fitted with tandem trolley wheel clamp. The trolley wheel clamp shall be fitted with trolley pole at about 46 cm behind the back end of the insulator retaining plate attachment.

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The other end of trolley pole a swivel stick with tag rope (1/2" dia, 150 ft.) is tied to take the load of complete insulator string when the insulator string is released from both the end. An additional pole clamp (2 ½") shall be fitted just behind the trolley wheel clamp and tied with wheel base plate to avoid any slippage of clamp under load condition as extra safety. The linemen on tower shall check the trolley pole arrangement to ensure that it is correctly positioned and operate properly. After the test of operation, the trolley pole shall be tied at a side temporarily till it is required for operation 9. Send up 2 no. strain link sticks and place it in such a way that it holds the conductor and the other end of the strain link sticks are connected with rope blocks. The strain link sticks is fitted to the tower with the help tower saddles. The strain links are used to hold the conductor. By adjusting the rope blocks connected to the link stick the load of the conductor can be shifted from insulator string to the strain link so that insulator string gets loosen and it can be removed easily for replacement of damaged insulator string.

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10. Send up two more wire-tongs with their mouth on the conductor of the working phase and the other end is connected to the tope blocks. The wire-tongs fixed on tower with tower saddle. These wire-tongs are used to hold the conductor in horizontal position while lifting and shifting the load of the conductor from insulator string to the strain link sticks 11. Now the strain link sticks are gradually pulled up with the help of rope blocks and simultaneously the wire-tongs on the working phase conductor is adjusted so as to have only vertical movement of the conductor as far as possible. As the conductor pulled vertically upward with strain link stick the load of the conductor is shifted gradually from the insulator string to the strain link stick and insulator string gets loosen and it can be removed easily for replacement of the damaged insulators. A lineman positioned at tower shall push out M-pin of the bottom insulator of suspension string with the help of hot stick attached with locating pin at its head to remove ball from socket of the disc insulator.

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12. A shunt shall be provided in between tower member / cross arm and 2nd insulator cap of the string to be replaced to make equipotential area of Cold End Line Man sitting on tower cross arm. Shunt is a tool used to drain / equalize the voltage between the point of connection. The flat face clamp of shunt is connected to any tower member and adjustable jaws of shunt to cap of second insulator of the string from cold end side. The lead of shunt should not interfere with the string. 13. Lineman on tower shall roll the trolley pole towards insulator string and push the suspension fork attached with tandem trolley pole to 3rd insulator belly to support the insulator string on insulator retaining plate of trolley pole, hold. The trolley pole at this position.

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14. Lineman on the tower cross arm will open the bolts of insulator string connected with hanger a little push is required to raise the string up during opening of bolts from hanger, the man handling trolley, pull shall apply cantilever load on trolley pole to raise the string up. 15. Now, the insulator string is free from both ends and resting on insulator retaining plate of trolley pole, the lineman on the tower shall remove the shunt and then trolleyed the string towards tower side up to about 6-7 ft. from its original position. 16. To lower down the insulator string at ground, a 2500 lbs snatch block shall be fixed at suitable place on tower and string shall be lowered down with the help of bull line (rope). 17. At ground damaged insulator (s) shall be replaced with new one

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18. Then the insulator string is raised gradually with the help of snatch block and Capstan Hoist. The insulator retaining plate of trolley pole is inserted to 3rd insulator belly and trolleyed the insulator string to its original position where it is to be fitted. The insulator string load is resting on the insulator retaining plate presently 19. Lineman on tower cross arm shall put the shunt in between cross arm angle and 2nd insulator disc in cold end side. Attach the insulator string with the hanger fixed in cross arm by little pull of string up. Take out the trolley pole from the string. Take the shunt out and put it in tool bucket. 20. Lineman positioned at tower shall make string connection with string yoke with the help of hot stick. After the conductor load is gradually shifted from strain link sticks to the insulator string by adjusting the rope blocks of the strain link sticks and wire-tongs attached to the conductor. Then the strain link sticks and the wire-tongs are removed from the conductor.

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21. Lineman shall remove the wire-tongs from the conductor connected just above the working phase. 22. The linemen on tower shall open all tools from tower and send back to ground carefully. 23. Supervisor / engineer in-charge ensure that all men and material has been cleared from tower.

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Thanks

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