SERVICE MAINS

service mains or service line is  connection of cable or conductor carrying current from LT line to meter board of a house or building using different methods. 

TYPES

There are  types of methods of service mains

i: overhead service mains

ii: underground service mains

i.Overhead service mains

It is the method of installing service mains or service line connection from LT line to meter board

where conductor are passed from above the ground level  i.e more than 5.7 m above ground level.

It is shown in the fig below:

Advantages of overhead service mains:

1.It is cheap.

2. Easy to erect.

3. Fault location and rectification is easy.

4. Extension of service line capacity is easy.

Disadvantages of overhead service mains:

1. Ugly appearance.

2. Affected by weather such as heat and rain,lightening.

3. Fault due to falling trees ,monkeys and birds, etc.

ii. Underground service mains

It is another method of service mains where the conductors or cables from LT line to meter board are passed under the ground ie, below ground level. It is shown in the figure below:

Advantages of underground service mains:

1. safety to people

2. Long life.

3. Not affected by weather such as sun rain, lightening, etc.

Disadvantages of underground service mains:

1. It is costly.

2. Fault location and rectification is difficult.

3. Skilled labours are required.

MATERIALS REQUIRED FOR SERVICE MAINS

i. Overhead service mains

1.Pot head

2. Break insulator

3.Reel insulator

4.Messenger wire

5.Service wire

6.Service pipe

7.Meter board

8.Clamps

9.Support pipe

the above points are shown in the fig. below according to no. wise:

ii.Underground service mains:

1.Underground cable

2.Service pole

3.G.I pipe

4.Clamp for pole

5.Cable box  (pot head)

6.PVC double sheathed cable

7.Meter board

It is shown below:

CODE OF PRACTICE FOR SERVICE MAINS

1.Service line should be tapped for the overhead line only at the point of support .

2.Earth leakage circuit breakers (ELCB) are to be used when load exceeds 5KVA.

3.When the load exceeds 10KVA or 8KVA, 3-phase connection is used.

4When service line erected across the road or along street should not be less than 5.7m above the ground level.

5.The meter board should always be placed at the entrance at the height of  1.5m from ground level.

6.The meter earth should not be used for other earthings.

7.Underground service mains are used for distance more than 30m.