Overvoltage characteristics of atmospheric origin
From Electrical Installation Guide
| Lightning strokes in a few figures: Lightning flashes produce an extremely large quantity of pulsed electrical energy (see Fig. J4)
|
Between 2000 and 5000 storms are constantly undergoing formation throughout the world. These storms are accompanied by lightning strokes which represent a serious hazard for persons and equipment. Lightning flashes hit the ground at an average of 30 to 100 strokes per second, i.e. 3 billion lightning strokes each year.
The table in Figure J3 shows the characteristic lightning strike values. As can be seen, 50% of lightning strokes have a current exceeding 33 kA and 5% a current exceeding 65 kA. The energy conveyed by the lightning stroke is therefore very high.
| Cumulative probability (%) | Peak current (kA) | Gradient (kA/µs) |
| 95 | 7 | 9.1 |
| 50 | 33 | 24 |
| 5 | 65 | 65 |
| 1 | 140 | 95 |
| 0 | 270 |
Fig. J3: Lightning discharge values given by the IEC 62305 standard
Fig. J4: Example of lightning current
Lightning also causes a large number of fires, mostly in agricultural areas (destroying houses or making them unfit for use). High-rise buildings are especially prone to lightning strokes.
