Conductors of overhead transmission and distribution lines typically consist of aluminum, which is lightweight and relatively inexpensive, and are often reinforced with steel for strength. Stranded cable is often used, which, as the name suggests, is twisted from many individual strands. At the same diameter or gauge, stranded cable is much easier to bend and manipulate. For underground lines, cables with insulation are used. Here heat dissipation is more of an issue, whereas weight is not. Copper is the material of choice for underground cables because, while it is more expensive, it has a lower resistance than aluminum. Low resistance is generally desirable for power lines to minimize energy losses, but also because heating limits the conductor’s ability to carry current.  

Resistance is given by R = rl/A,

 Where

•  A is the cross-sectional area,
•  l is the length of the conductor, 
• r (rho) is the resistivity (inverse of conductivity).

   The electrical resistance of a power line thus increases linearly with distance and decreases with the conductor cross section. For the purpose of minimizing resistance, then, conductors should be chosen large. However, resistance must be weighed against other factors, including the cost of the conductor cable itself and its weight that needs to be supported by the towers. Because even aluminum conducts so well, this trade-off comes out in favor of surprisingly slender lines considering the amount of current and power transferred.   

 Selection of Route  There are no lay-down conditions the routing of MV Overhead Distribution Lines.However due consideration shall be given for the following factors when selecting route for the MV Line.  

1. Straightness of the route.

 2. location along the road 

3. amount of way leave to be cleared to be 

 4. inconvenience caused to the other services to be 

 5. swampy ground and areas liable to flooded to be avoided 

6. geological condition of the located pole pit 

7. cost of construction shall be kept to minimum 

8. use of taller poles at uplifts, and construction of tension points at uplifts to be avoided  

Pole Positions  

Terminal Pole Here the line is terminated with MV Tension Insulators on one side of the pole. This is also called dead end poles  

Shackle Pole  Here the line is terminated with MV Tension Insulators on both sides of the same pole.  

Intermediate Pole  Here the line is continuous and is supported on MV Pin Insulators or Post Insulators as necessary.

When a line changes direction, an additional force is introduced at the angle pole. This force is the resultant of line tensions acting at the pole. The resultant force tries to move the top of the pole in the direction that bisects the angle between the wires. These forces, due to angles, can be considerable. The Stays, Struts and Flying Stays shall be fixed to neutralize the resultant force on the poles. Number of stays to be used at any particular pole location is designed on the overturning force acting on the pole. The force acting on the pole depends on the following factors. 

 • Number of conductors and size of the conductor, along with conductor tension. 

• Length of adjacent spans

 • Angle of deviation of the line

 • Equipment mounted on the pole

 • Geographical position of the pole  Following shall be noted in fixing slays & struts  

1. The angle between pole and the stay wire or strut pole shall not be less than 30°. 
2. Stays, Struts and flying Stays should be erected so as to avoid disturbances to pedestrians or vehicular traffic.
3. It shall be ensured that the correct side of the ratchet nut faces the ratchet face of the cross head of the buckle before tightening the stay buckle.
4. Stay and Flying Stay Wire over a street must not be less than
5. In flat terrain poles used for struts and flying stays shall be of the same size as line poles.
6. Stay Insulator shall be positioned below the level of the lowest current carrying conductor and not-less than 3.7m above the ground.  

 Types of Stays 

1. Line stay 
2. Angle stay 
3. Bow stay 
4. Flying stay

Ordinary Supply  

01) Single Phase 30A (single Phase 5A, single Phase 15A) 

02) Three Phase 30A 

03) Three Phase 60A

 Bulk Supply

01) Three Phase 100A

02) Three Phase 160A

03) Three Phase 200A

04) Three Phase 400A

 Single Phase Supply

  Supply to the domestic consumer is given by 415v distribution power lines .By using three phase overhead lines or underground lines take live wire and neutral wire and connected it to the consumer meter as figure shown in bellow then Live wire is connected to the live wire of the house through the breaker. Neutral wire came from meter is connected to neutral wire of house.

Three phase supply  Supply to the domestic consumer is given by 415v distribution power lines by using three phase overhead lines or underground lines then directly supply to factories or consumer through the three-phase meter. Usually this is done when the power consumption or the consumer is very high.