Lightning can strike the overhead power line which enters our house, or a main power line that is blocks away from our home.Lightning can strike an object near our home such as a tree or the ground itself and cause a surge.
Voltage surges can be created by cloud to cloud lightning near our home. A highly charged cloud which passes over our home can also induce a voltage surge.Voltage surges can also be caused by standard on and off switching activities of large electric motors or pieces of equipment.
When a voltage surge is created, it wants to equalize itself and it wants to do it as quickly as possible. These things seem to have very little patience. The surges will do whatever it takes to equalize or neutralize themselves, even it can short circuiting all of our electronic equipment.
The method of providing maximum protection for equipment is done by providing grounding. Which is efficiently done by using Lightning Arrester(or Surge Diverts).
Lightning arrester is device which provides an easy conducting path or low impedance path for the flow of current when system voltage increases more than the design value and regains its original properties of an insulator at normal voltage.
Working Principle of Lightning Arrester:-
The earthing screen and ground wires can well protect the electrical system against direct lightning strokes but they fail to provide protection against traveling waves, which may reach the terminal apparatus. The lightning arresters or surge diverts provide protection against such surges. A lightning arrester or a surge diverted is a protective device, which conducts the high voltage surges on the power system to the ground.
It consists of a spark gap in series with a non-linear resistor. One end of the diverter is connected to the terminal of the equipment to be protected and the other end is effectively grounded. The length of the gap is so set that normal voltage is not enough to cause an arc but a dangerously high voltage will break down the air insulation and form an arc. The property of the non-linear resistance is that its resistance increases as the voltage increases and vice-versa.
Types of Lightning Arresters:-
There are several types of lightning arresters in general use. They differ only in constructional details but operate on the same principle, providing low resistance path for the surges to the ground.
- Rod arrester.
- Horn gap arrester.
- Multi gap arrester.
- Expulsion type lightning arrester.
- Valve type lightning arrester.
- Silicon Carbide Arrestor.
- Metal Oxide Arrestor.
This is all about the basics of Lightning Arrester.