Underground Service Mains Materials and Specification of Materials

July 24, 2020February 21, 2022 CS Electrical And Electronics

Hello everyone, in this article, I will discuss underground service mains materials and specifications of materials, which means materials used in underground service mains, and also the specification of materials. You can also catch me @ Instagram – Click Here

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Also read – Electrical Machines Questions And Answers.

Underground Service Mains

Underground Service mains are used to connect low tension lines to the consumer meter board below the ground as shown in the above figure.

The materials as shown in the above figure are :

Underground Cable
Service pole
G.I. Pipe
Clamp for pole
Cable box (connecting pothead)
P.V.C double sheathed cable
Meter Board

The use of underground cable is usually made for service connection when the power to be supplied is large say 25 KW and above. Nowadays it is also preferred in cosmopolitan cities like Bengaluru etc. The above figure shows the U.G service connection of sufficient current capacity and required cords. The supply is linked to the P.V.C double sheathed weatherproof cable to a pothead. The pothead of suitable size is fitted to the service pole by means of MS channel with nuts and bolts.

The U.G. cable is carried from the pothead to the ground through the G.I pipe using bends. In the ground usually, trench laying is done in case of no obstruction. However in case of road crossing etc. in the ground also the cable is taken through the G.I pipe and bends. Usually, for single-phase twin-core, U.G cable is used. For three-phase either 3 and a half core or 4 core U.G cable is used. Normally, steel armored U.G. cable is preferred.

Material Used In Underground Service Mains

1) Underground Cable :

(a) Size of Cable – In square mm, such as 4, 6, 10, 16, 25, 35, 40, 70, 95, 120, 150, 225, 300, 400, 500, 630.
(b) No of cores – 2 for single-phase, 3 1/2, or 4 for three phases.
(c) Conductor Material – Aluminum.
(d) Voltage Grade – 1100 V and 11000 V.
(e) Insulation – Paper insulated lead covered or P.V.C insulated for heavy-duty.
(f). Armored – Tape armored or steel wire armored.

Guys above are the specification of underground cables, underground cables are drawn below the ground, they are used to carry electricity from a pothead to a service pipe. Service cables are used from low tension lines to pothead and at meter side from service pipe to meter board. See guys underground cable is different and service cable is different don’t get confused.

2) Pothead or cable box :

Voltage Grade – 1100 V or 11,000 V

Material – Cast iron

Suitable for a particular number of core and size of cables such as 3 1/2 or 4 core 16 sq mm cable or 2 core 10 sq mm cable.

Pothead means which consist of protective devices like a fuse, pothead is just for protection. If any fault occurs in a low tension line, the underground cable may burn so to avoid damage pothead is used.

3) G.I. Pipe

Diameter of pipe 40 mm diameter for 4, 6, 10, and 16 sq mm cables or 50 mm diameter for 25, 35 sq mm cable, etc.

GI pipe or Galvanized pipe through which underground cables are drawn from pothead to service pipe.

4) G.I. bends

G.I bends 40 mm diameter 3 mm thick.

To connect two GI pipe at 90 degrees, GI bands are used.

5) Well, seasoned teak wood Board of suitable size for meter board.

6) Clamps

Clamps are used on both sides, at the pole side and also at the meter board side. Clamps are used to fix GI pipe with pole and it is also used at another side to fix GI pipe to the wall.

07. M.S channel with nuts and bolts for fixing pothead on service pipe.

8) PVC cable

Size – In sq such as 4, 6, 10, 16, 25, 35 etc.

Conductor – Aluminum only.

Colt Vol Grade – 1.1 KV or 11 KV.

PVC cable is used at both sides, at the pole side, it is used to connect low tension line to pothead and at meter side from service pipe to meter board.

9) Earthing Set

A complete set of 40 mm G.I pipe, 3 mm thick, 2.5 m long having an alternate hole of 12.5 mm diameter at a distance of 300 mm is all along the length buried in the pit is to be filled with alternate layers of edible salt and charcoal.

10. Meter Boar

The cable from the service main is connected to the meter board. The meter board consists of energy meter, fuse, indicators, etc. The energy meter is a device that records how many energy consumers have consumed until now. The energy meter is classified are analog and digital energy meter.

Some points related to underground service mains

We all know that underground service mains are a system used to transmit electricity from low tension line to meter board below the ground. now I will discuss some advantages related to underground service mains, life long-one time investment, not affected by sun or rain, not ugly appearance, the most important thing is it is safe.

Disadvantages of underground service mains fault location are difficult – fault location is difficult as compared to overhead mains, skilled laborers are required, materials cost is more compared to overhead service mains, etc.

Now I will discuss the cost of various materials used.

Cost of Materials

01. Pot Head – The cost of pothead is 250 for a single-phase, 450 for the three phases.
02. Service cable – The cost of service cable is 25-30 rupees per meter.
03. GI pipe – The cost of GI pipe is 3/4 inch is 35 per meter.
04. Clamps – The cost of GI clamps is 60 rupees per piece.

I hope this may help you all a lot. Thank you for reading.

Tags: Underground Service Mains Materials and Specification of Materials, what is underground service mains, what is overhead service mains, materials used in underground service mains, estimation, and cost of underground service mains.

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