Electricity generation - lightning:

Lightning is a natural discharge of atmospheric electricity. It is generated when the upper air becomes unstable because of pressure and temperature variations. This motion of upward moving air is usually present inside heavy storm clouds. The updraft of air and water particles and decrease in temperature causes an electric charge to develop which in turn produces lightning. The particles of water in the cloud become charged because of their upward movement through the air. The small water drops acquire a positive electrical charge while the larger water particles acquire a negative charge.

The updraft and turbulence of the cloud separates these positive and negative particles. The upper parts are positively charged and the middle and lower parts are negatively charged. The separation of these charged particles within the cloud allows the electrical energy of the different charges to collectively increase. The buildup becomes so great that a flash occurs between the positives and negatives. A large luminous spark is the result. This spark may flash from cloud to cloud, within the cloud, or from the cloud to earth.

When lightning strikes the ground a small charge (called a leader) is attracted from the cloud to the ground. When a critical distance from the ground is reached, an upward lightning bolt (called a streamer) is launched from the ground. The first upward streamer to connect with a leader will complete the cloud-to-ground electrical connection, and the main discharge (return stroke) from the cloud to the ground will occur. Thunder is the noise made by this electrical discharge.

For more information go to:
http://science.howstuffworks.com/lightning.htm

Lightning is dangerous because if it strikes you or strikes near you, then you can receive an electric shock severe enough to kill you. It is advisable to stay indoors or in your car until the storm passes. Don’t stand in open spaces or shelter under trees because you will increase the risk of being struck by lightning. The high electric currents (as high as 200,000A) and high temperatures (around 30,000°C) are the main causes of death and damage in lightning strikes.

Apart from the obvious danger to life (it is claimed lightning causes more human deaths than any other weather phenomenon) lightning causes severe damage. Western Power has experienced many problems with lightn­ing strikes affecting equipment such as transformers and causing unex­pected blackouts. In 1984 special protection methods were incorporated in the design of the new West Kalgoorlie electricity terminal station because of the extremely high number of lightning strikes in the region. Up to 2,000 lightning strikes have been recorded in one day in West Kalgoorlie! For protection, a grid of masts and under­ground copper strips was installed to arrest and dissipate lightning strikes to prevent power blackouts.

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