Atmospheric charge separation

Lightning is a rapid discharge of electrostatic energy between charged regions in a thunderstorm cloud, or between the cloud and the earth. Charge separation inside the storm builds electric fields strong enough to ionize air and create a conductive path.

Why electrical systems care

When a cloud-to-ground flash occurs, enormous current flows for a short time. Nearby power lines, earthing systems, and conductive structures can pick up dangerous voltages through induction, conduction, and rise of earth potential.

Key takeaway for SPD design

Surge protective devices (SPDs) do not "stop lightning." They divert and clamp transient overvoltages so equipment insulation and electronics survive the event.

• Typical peak currents for first strokes can reach tens of kiloamperes
• Subsequent strokes are often shorter but can still stress electronics
• Distance from the strike strongly affects coupling severity