Even after a power line has been de-energized and isolated from its normal power source, it is still extremely dangerous to work on. This is because the line can become energized again from several sources:

• Induced Voltage: Nearby energized lines can induce a dangerous voltage onto the de-energized line. The longer the parallel section, the greater the induced voltage.

• Accidental Re-energization: Human error can lead to a circuit being inadvertently closed at a substation.

• Lightning Strikes: A lightning strike on a nearby structure can travel through the de-energized line.

Earthing the line protects workers from these risks by creating a low-resistance path for any potential fault current to safely flow into the ground. This protective measure ensures that if a line is re-energized, the resulting short circuit will trip a protective device, de-energizing the line and protecting the worker.