State the procedure for laying / installation of underground cable.

State the procedure for laying / installation of underground cable.  
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1 Answer

Answer :

1) Direct laying Cable: or Trench laying method:

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Procedure:

* For laying of a cable trench about 1.5m deep and 0.5m wide is made along the cable route.

* A layer of 10 cm thickness of soft soil is spread throughout the cable route in trench.

* The cable is laid on this soft soil (bed)

* A wall of bricks (concrete cover) is provided on either side or top of cable along the length of cable for better mechanical protection.

* Another layer of soft sand, about 10 cm thicknesses is spread throughout its cable length.

* Refill the remaining trench with the help of remaining soil up to ground level.

* While crossing roads (public-crossing) cable is laid through cement pipe or DWC pipe,instead of bricks for better mechanical protection.

* When more than 1 cable is to be laid in the same trench, then minimum 30 cm spacing is provided between 2 cables and gap is filled by sand.

* The spacing is kept between 2 cables to reduce the effect of mutual heating and also fault occurring on one cable does not damage the adjacent cable.

* Only armored cables are used in this method. 


2) Draw in cable laying System or Duct laid cable laying system: 

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Procedure:

* A trench of minimum 60cm deep is made along with cable route.

* Width of trench depends on number of conduits to be laid.

* Separate pipes are provided for each cable.

* Spacing between 2 cables (conduit) is between 25 cm to 75 cm.

* Diameter of pipe is 2 to 3 cm, greater than cable diameter for easy handling of cable.

* Pipe used may be cement pipe, DWC pipe or ducts of glad stone are used.

* For Maintenance and other cable work, man-holes are provided at suitable distance.

* Size of man-holes should be large enough to allow a person to enter into duct without difficulty.

* Unarmored cables are used in this type. 


3) Solid system or through Laying method: 

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Procedure:

* In this method of laying, the cable is laid in open pipes or troughs dug out in earth along the cable route.

* The troughing is of cast iron, stoneware, asphalt or treated wood.

* After the cable is laid in position, the troughing is filled with a bituminous or asphaltic compound and covered over.

* Cables laid in this manner are usually plain lead covered because troughing affords good mechanical protection. 

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