Indian standard - Download as PDF File .pdf), Text File .txt) or read online. Code of practice for installation of power cables upto and including 33kV. IS - Download as PDF File .pdf), Text File .txt) or read online. IS: MAINTENANCE 61 MAINTENANCE OF CABLE INSTALLATION. Bureau of Indian standards, IS: (reaffirmed ), Code of practice for installation and maintenance of power cables upto and including 33 kv rating.
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IS Code of practice for installation and maintenance of power cables up to and including 33 kV rating. byBureau of Indian Standards. “Knowledge is such a treasure which cannot be stolen”. IS (): Code of practice for installation and maintenance of power cables up to and including. IS: – Indian Standard. CODE OF PRACTICE FOR INSTALLATION. AND MAINTENANCE OF POWER CABLES. UP TO AND INCLUDING 33 kV.
The requisite protective covering should then be provided. For such conditions. Identifier gov. RCC or fibre glass protection boxes are used see Fig. In the case of single-core cables the cast iron or steel pipes should be large enough to contain all the three single core cables forming the circuit in the same pipe. A simple plank can serve as drum brake. Topics data.
Each tray should preferably contain only one layer of cables. Distance between these supports depends on size and weight of the cable. The suspenders are hung from catenary wire by means of GI dropper wires. NOTE — When calculating perimeter of the tunnel cross-section. Consequently there is an increase in the temperature of the cables installed in the tunnel and accordingly a proper derating has to be applied to the current carrying capacity of the cables installed in the tunnel.
The increase in air temperature is given by the following formula: The route should not subject these cables to any vibrations. The cable will unwind and become loose if the drum is rolled in the opposite direction Fig.
The route of proposed cable should be such that intersection with other cables will be minimum. Additionally a sand bed at the foot of the ramp may be made to brake the rolling of cable drum. If neither of these is available. Due consideration should be given for adequate ventilation.
The cable drum should then be rolled over the ramp by means of ropes and winches. A ramp or crane may be used for unloading cable drums.
It is desirable for the drums to stand on battens placed directly under the flanges. During storage. The cable should. To avoid damage to the protective covering and the insulation the cable must not be pulled across hard and sharp objects and must not be bent in an inadmissible way. The kinks nooses are particularly dangerous and should be avoided at all costs.
In doing so. The drum is jacked up with a drum axle to such a height that the plank needed for braking cannot jam. Warming of cables may be achieved by storing the cables for adequately longer period not less than 24 hours in a heated building or in a tent with hot air heaters. To facilitate laying.
A simple plank can serve as drum brake. The cable laying must be carried out swiftly. When pulling.
When the cables are arranged in a duct or on a rack in this way. No pull should be exerted on the end of the cable.
Instruction to back fill the trench should not be given until the entire length is protected by cable cover and checked. A rope is attached to the cable stocking pulling eye. Non-magnetic clamps may not be essential in this case and it suffices to bind the cable with steel. Single-core cables should not be installed individually in protective steel ducts.
Identification tags should also be attached at every entry point into the buildings and at the cable end termination. To avoid accidental damage to other installations in the path of the tunnel during the tunnelling operation. Of these. This is often necessary when the number of other pipes and services under the roadway.
If a large number of pipes are laid across the road.
It is usual. This invariably leads to kinking and bird-caging. The drum is slowly raised equally from both ends by using both the jacks. The drum is jacked high enough to fit in braking plank.
At least three solid plates for guiding the cable around the bend should be used maintaining minimum bending radius. Trailer should move very slowly and the cable drum should be rotated by hand and braked if necessary in order to prevent excessive tensile stresses or kinking of the cables see Fig.
Weak shaft should not be used. The drum should never be kept flat on its side on the ground and the cable taken away from the same. The cable drum is mounted and is kept at proper position in such a way that the cable is paid out from the top of the drum when turned against the direction of arrow marked ROLL THIS Where the trench is deep. A cable grip is provided at the end of the cable and rope connected to the cable grip is passed down the trench to pull the cable.
It is slipped over the end of the cable and is so designed that it tightens the grip on the cable as the pull increases. Cable rollers are placed at 3 to 4 metre intervals in the cleaned and bedded trench.
Men may also directly grip the cable. The number of men required for pulling largely depends on the size and weight of cable being laid. When pulling round a bend. The cable grip is made of wires woven in the form of a basket. The men at rollers should also apply graphite grease in the course of pulling. The gangman Mucadam should stand in a commanding position and make evenly timed calls. This enables the men positioned at each roller to pull the cable evenly.
The cable is then slid off the bottom of the drum and laid immediately in the trench. The cable loops must be distributed over a cable length of 4 to 6 m. The other half of the gang must hold on to the rope as closely as possible. It should be ensured that the cable is pulled off from the figure of eight only from the side in which it was first looped see Fig. The order should not be given from the head or tail of the section.
Where the distance is greater. The order should. The cable should be lifted off over the drum sidewall towards the trench and in doing so further cable from the bottom of the drum should be pulled off. Another possibility for synchronizing orders is to use 2 to 3 hand held loudspeakers distributed along the section. NOTE — For heavy cables the Heave ho method of laying should be discouraged as far as possible since it tends to leave built-in stresses in the cable.
Long steel or plastics duct sections should be checked with a gauge and coated on the inside with lubricant for plastics and concrete ducts. They are not recommended for unarmoured cables. The duct should be cleaned before pulling the cable through it. They are particularly economical for laying several long lengths of cables in parallel.
When aligning the cable. It is advisable to leave a crown of earth not less than 50 mm in the centre and tapering towards the sides of the trench to allow for settlement. If cable has to be cut. If trench is partially filled with water. As a temporary measure. Each cable length should be aligned immediately after it is laid starting from one end. The requisite protective covering should then be provided.
The position of the cable joint should be marked with markers. Walkie-talkie sets are necessary to permit the personnel at the drum. Lead cap for paper cable and plastic cap for PVC cable should be used.
Where necessary. The ends may be looped to provide extra lengths in case of extruded dielectric cables. To enable the cable to be laid on the inner or outer side of the trench.
The quality of joint should be such that it does not add any resistance to the circuit. The joint should further be resistant to corrosion and other chemical effects. The materials and techniques employed should give adequate mechanical and electrical protection to the joints under all service conditions.
Where the surface is of special material. Such temporary reinstatement should then be left till such time that the soil thoroughly settles down.
NOTE — Other accessories. In case of buried joint. The joint should not be near pipe end or at the bend.
If the ground has been made up by tipping. For PILC cables it is always advisable to protect the factory plumbed cap by laying the end in solid bitumen until such time as the jointing is commenced. There should be sufficient overlap of cables to allow for the removal of cable ends which may have been damaged see Fig. The two lengths of cable meeting at a joint are laid with an overlap of at least half the length of joint box when pulling in. The floor of the joint pit should be well consolidated.
This point is extremely important as otherwise it may result in a short piece of the cable having to be included. This enables the jointer to adjust the position of his joint slightly to allow for any obstructions that may be encountered see Fig. The sides of the pit should be draped with small tarpaulin sheets to prevent loose earth from falling on the joint during the course of making.
The samples of paper should be handled as little as possible to avoid contamination particularly by perspiration. The belt insulation.
Particular attention should be paid to the paper next to the sheath and to that next to the conductor. If the seals are found broken or the lead sheath punctured. The jointer should wear rubber boots or gloves or stand on a rubber mat. Only a single strip of paper gripped by a pair of tweezers should be used for the test since if several thicknesses of a paper are immersed.
The presence of moisture is indicated by the formation of bubbles when a piece of the paper is immersed in hot compound. When rubber mats are used in wet holes. The cut ends should be separated and tested to ascertain if either or both are live or dead.
It is advisable to step the positions of the cuts. A small piece of rubber insertion should then be placed between the core to be cut and the remaining cores and cut through the selected core.
Rubber insertion between this core and the rest should not be removed till this exposed core is completely taped. This process should be repeated for other cores taking care that only one core is handled at a time. A rubber insulation should be inserted between this core and the rest and prepare the core for tee-jointing. Irrespective of being live or dead. The same procedure should be followed with the remaining cores. The paper insulation of the main cable core should be cut for a suitable length and the jointing work completed.
The amount of armouring and length of lead sheath. The most convenient core to be teed should be selected and separated from others by means of a wooden wedge as far as possible. The cores of the cable to be tee-jointed should be spread and suitable tapping positions selected on the main cable.
For 22 kV compound and 33 kV grade. RCC or fibre glass protection boxes are used see Fig. Since 22 kV and 33 kV cast iron boxes and moulds for HT joints in cast resin system are not yet standardized.
Cast iron boxes with bitumen based filling compounds can be used with PVC cables with certain precautions. For voltages above this neither moulds nor casting resins are standardized. Core identification should be properly studied for this purpose. Hence cable supplier may be consulted for his advise on selection. Tee joints on HT cables up to and including 11 kV may be done only in exceptional cases. Moulds for such joints should conform to IS: Cold setting casting resins are used for further protection against water and corrosion.
A typical HV dividing box is shown in Fig. Comprehensive jointing instructions should be obtained from the cable manufacturer and should be followed see Fig. For more information: Electrotechnical Section Name: Code of practice for installation and maintenance of power cables up to and including 33 kV rating Number of Amendments: Superceded by: Identifier gov.
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Posts Comments. Where the possibility of electrolytic corrosion exists, for example, adjacent to dc traction system, the potential gradient along the pipe-line and the cable sheath should be specified. If the cables are pulled by gripping the conductor directly with pulling eye, the maximum permissible tensile stress depends on the material of the conductor and on their cross-section as given below: High voltage cables, 3.
Steel, cast iron, plastics, cement or earthenware ducts, or cable ducting blocks should be used where cables cross roads and railway tracks. Spare ducts for future extensions should be provided. Spare duct runs should be sealed off. While designing a cable layout on a bridge; expansion of bridge due to changes in atmospheric temperature should be taken into account. On most of the rail-cum-road bridges, the cables are subjected to vibrations.
Petroleum jelly or graphite powder or a combination of both is effective for this purpose and through lubrication will reduce the pulling tension by about 40 percent. The width of the rack should not exceed 0. Only single-core cables laid on horizontal racks need be clamped at suitable intervals.
Multi-core cables need not be clamped. The distance between the vertical clamps should not be more than 2 m. Laying Cables on Racks Inside a Tunnel: Horizontal distance between Two cable is min Diameter of Cable and vertical distance between two cable row is 30cm. In cable tunnel, the head room should not be less than 2 m and width sufficient to leave a free passage of at least to mm either from one side or in the middle.
Identification tags should also be attached at every entry point into the buildings and at the cable end termination The spacing between three cables laid in one plane should be not less than the cable diameter. When the cable run is several kilometers long, the cables should be transposed at one-third and at two-thirds of the total lengths.
For cables having more than 5 cores, the core identification may be done by numbers.
In that case, the insulation of cores shall be of the same color and numbered sequentially, starting with number 1 for the inner layer. The numbers shall be printed in Hindu-Arabic numerals on the outer surface of the cores. All The numbers shall be of the same color which shall contrast with the color of the insulation. The numerals shall be legible. If the number consists of two numerals, these shall be disposed one below the other and a dash placed below the lower numeral.