Electrical Transmission and Distribution

1. EARTHWIRE

2. EARTHWIRE/GROUNDWIRE
 Earthwire/Groundwire are arranged above
the phase conductors and grounded at
every tower.
 The main function of Earthwire/ Groundwire
is to provide protection against direct
lightening strokes to the line conductors or
towers.
 In addition Groundwire reduces the induced
voltage on parallel telecom lines under fault
condition.

3. GROUNDWIRE/EARTHWIRE
 Groundwire must meet the following
requirements:
- It must be able to carry the maximum lightening
current without undue overheating.
- It must be strong mechanically.
- It must be high enough to afford protection to all
the line conductors. This function is called
shielding.
- It must have enough clearance above the line
conductors at mid-span to prevent a side
flashover to a line conductor.
- Tower footing resistance should be low.

4. REQUIREMENTS FOR GS EARTHWIRE
 Chemical Composition
 Carbon : < 0.55%
 Increase strength but also increases brittleness
 Manganese: > 0.3%
 Imparts malleability and strength and lessens fatigue
 Sulphur & Phosphorous : < 0.045%
 These are impurities of Iron and should be eliminated as far
as possible

5.  Galvanising
 Protects against corrosion
 Joints
 No joints are permitted in galvanised strands as these are the
weakest point for onset of corrosion.