What is a Lightening Arrester?
Lightning can create voltage surges in several of the following ways. Lightning can score a direct hit on your house. It can strike the overhead power line that enters your home, or the main power line that is blocks away from your home. Lightning can strike branch circuitry wiring in the walls of your house. Lightning can strike an object near your home, such as a tree or the ground itself, and cause a surge. Voltage surges can be created by cloud-to-cloud lightning near your home. A highly charged cloud that passes over your home can also induce a voltage surge.
Surge arresters are employed to prevent damage to the apparatus due to high voltages. The arrester provides a low-impedance path to the ground for the current from a lightning strike or transient voltage and then restores to normal operating conditions. When a high voltage (more than rated line voltage) exists on the line, the arrester immediately creates a path to the ground and thus limits and drains off the excess voltage. The arrester must provide this relief and prevent further flow of current to the ground. The arrester has two functions:
- It must provide a point in the circuit at which an over-voltage pulse can pass to the ground.
- Prevent any follow-up current from flowing to the ground.
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| Lightening Arrester |
Types of Lightening Arrestors:
There are several types of lightning arresters in general use. They differ only in constructional details but operate on the same principle, providing a low resistance path for the surges to the round.
- Rod arrester
- Horn gap arrester
- Multi gap arrester
- Expulsion-type lightning arrester
- Valve-type lightning arrester
Installation of Lightening Arrestors:
- The arrester should be connected to the ground to a low resistance for effective discharge of the surge current.
- The arrester should be mounted close to the equipment to be protected & connected with the shortest possible lead on both the line & ground side to reduce the inductive effects of the leads while discharging a large surge current.
Maintenance of Lightening Arrestors:
- Cleaning the outside of the arrester housing.
- The line should be de-energized before handling the arrester.
- The earth connection should be checked periodically.
- Record the readings of the surge counter.
- The line lead is securely fastened to the line conductor and arrester
- The ground lead is securely fixed to the arrester terminal and ground.