Lightning arrester is a protective device which is give protection against the over voltage due to the lightning surges. Lightning arrester is kept in sub station at suitable palce. Which connected between the ground and the line conductor.
There are many types of lightning arresters,
- Rod gap arrester
- Sphere gap arrester
- Horn gap arrester
- Multi gap arrester
- Electrolyte type arrester
- Metal-oxide lightning arrester
Rod gap arrester :-
Construction of rod gap arrester is very simple. Two rod are band at right angle and diameter of rod is 15 mm. Make some gap between that two rods. One rod is join to the ground and other is joint to the line conductor.The distance between the insulator and gap should be more then the third of the lengh. So the arc is occur away from the insulator.
Sphere gap arrester :-
In this type of arrester , two electrode sphere is taken and they both kept to near each other by few distance. One sphere is connected to the ground and other is connected to the line conductor. There is three phase transformer is used. Chock coil is connected between the one phase of transformer and sphere. During the healthy condition there are no discharge at normal voltage. Air is dielectric median between two electrode. When over voltage is comes the air between two sphere is breakdown in form of arc. Arc is continue when over voltage is come until the voltage is not available when circuit breaker tripped.
Horn gap arrester:-
There are two metal rod in shaped of horn. One is connected to ground and other is connected to line conductor. The horn are mounted on the insulator.There is no arc produced between the two horn during normal condition. But when over voltage is come arc is produce between the horn rods.
So over voltage surges is grounded. Here choke coil is used. Which is connected between the horn and the winding of transformer. choke coil is gives negligible reactance at power frequency but during the over voltage its offer the high reactance. Because of high frequency. So over voltage lightning surges does not effect the winding transformer and its is grounder through the horn gap rod. Here resistance is connected in series with the horn. Which is limit the flow of current.
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