Lightning Arrester:
The circuits are protected from lightning strikes by a protective device referred to as a lightning arrester. Lightning strikes are
- Surges with high transient voltage,
- Arcs of isolation,
- Sparks, and
- Surge currents, etc.
These devices are utilised to protect electrical systems by redirecting excessive voltage surges toward the earth. And these power systems and overhead transmission lines can also be protected from direct lightning strikes using ground wire or earthing.
Principle of Operation of Lightning Arrester:
Once the voltage surge passes throughout the conductor, it reaches the area where the arrestor is positioned, according the lightning arrestor’s working principle. It will temporarily break down the lightning arrestor’s insulation, allowing the voltage surge to be discharged toward the ground. Once the system voltage falls below the predetermined value, the insulation between the ground and conductor will be restored. In addition, the current will no longer flow toward the ground.
Surges can go more easily via the lightning arrester because it offers a path with a low impedance, by switching the current to go towards the ground and by clamping the high voltage.
Installation of Lightning Arrester:
To effectively protect the equipment from lightning and travelling waves, the lightning arrestor as close as possible to the equipment. Between the line and the ground, the arrester is installed. For the three-phase system, install three arresters, one for each phase. The arrester has a wide range of applications for the protection of
- Transformers,
- Motors,
- Generators,
- Transmission lines.
Characteristics of a Lightning Arrester:
- During normal operating conditions, the current through the lightning arrester must be minimal. It must have a high impedance for high power frequencies.
- Whenever there are voltage spikes, transients, or lightning, the current must flow through it.
- It must be able to withstand anomalous discharge current without being damaged.
- It must rapidly re-establish its insulation level for power frequency once a surge or travelling voltage has been extinguished.
Types of Lightning Arrester:
There are a variety of Lightning Arresters utilised for a variety of purposes:
- Horn Gap Arrester
- Multigap Arrester
- Expulsion Type Arrester
- Rod Gap Arrester (Spark Gap Arrester)
- Sphere Gap Arrester
- Valve Type Arrester
- Thyrite Lightning Arrester
- Pellet Type Arrester
- Metal Oxide Arrester
