Lightning arrester devices are used at substations and at line terminations to discharge the lightning overvoltages and short duration switching surges from lightning voltage.
They are capable of discharging 10 to 20 KA of long duration surges (8120 us) and 100 to 250 KA of the short duration surge currents. These are non-linear resistance in series with spark gap which acts as fast switches.
The requirement for Surge Arrester
Lightning flashover on transmission lines can be reduced by increasing the insulation or by reducing the tower footings resistance. An alternate approach is to install transmission line surge arresters in parallel with the insulator strings to prevent insulator flashover.
Following is the basic operational requirements for arresters:
1. If lightning strikes within a protected section, it should not create flashover either inside or outside the protected section.
2. If lightning strikes outside a protected section, it should not create a flashover mild Protected section.
3. Lightning flash can inject several strokes in less than a second so arresters must have sufficient energy capability.
4. Arresters which are for lightning protection should not conduct during SWitChing or during low-frequency overvoltage due to the line to ground fault, etc.
5. It should be able to keep the system voltage as possible as normal.
Types of surge arresters
There are mainly following live types of surge arresters:
1. Expulsion type surge arrester.
2. Valve type surge arrester.
3. Metal oxide surge arrester.
4. Rod-gap type surge arrester.
5. Zinc-oxide surge arrester.