Medium Voltage Cables ( 2.001 - 35.000V )
- Majority are constructed as shield construction except those for 5 KV and below.
- For underground cable, concentric neutral cable is used.
- The concentric neutral cable consist of the conductor, semi conductor insulation, neutral and jacket.
Other Shield Construction of MV Cables
- Consist of the copper conductor, conductor shield (semi conducting compound), insulation, insulation shield (semi conductor tape), metallic sheath, armour and jacket.
- The conductor shield minimizes corona by equalizing the voltage gradients across the air gap between the conductor strands.
The purposes of outer shielding on medium and high voltage cables are to:
- Prevent damage from corona.
- Confine dielectric field to the inside of cables or conductor insulation
- Reduce induced voltage
- Provide increased safety to personnel.
Cable trench
- Low voltage and high current.
- Lay in the foil formation better than frat formation.
- When cable cross will cause high temperature in trench.