Electrical specs of earth lightning

Cloud-to-earth lightning has the greatest damage potential. This type of lightning is divided into positive and negative lightning, depending on the polarity of the cloud charge.

Positive cloud-to-earth lightning is the most critical, due to the duration of the lightning current pulse. With a maximum current of several 10 kA, it may last longer than 2 ms. The electrical charge is typically higher than 50 As.

Negative cloud-to-earth lightning starts with a lightning current pulse whose maximum amplitude amounts also to several 10 kA, but lasts merely 1/10 of the time of a positive one. Its peculiarity lies in the subsequent smaller multiple discharges, which may result in a total duration of the lightning of over one second and a total electrical discharge of over 100 As.

Time domain considerations - Currents

This produces the following basic, schematic lightning current patterns:

1) Positive or negative lightning current pulse of several 10 kA and less than 2 ms duration  (TS).

2) Positive or negative lightning current pulse according to 1), with subsequent long-duration current of about 100 A during a period of less than 500 ms (TI).

3) Sequence of negative lightning currents with a first lightning current pulse according to 1), followed by subsequent lightning currents up to 10 kA. The break
times between the lightning current pulses
are shorter than 100 ms.

4) Sequence of negative lightning currents according to 3), with integral long-duration current according to 2)

On the basis of these lightning current patterns, CIGRÉ and IEC 61312-1 defined 3 groups of laboratory-simulated lightning currents:

Group 1 – lightning current of positive or negative polarity, first stroke – wave form 10/350 µs

Group 2 – lightning current of negative polarity, subsequent stroke – wave form 0.25/100 µs

Group 3 – lightning current of positive or negative polarity, long-duration stroke – DC 0.5 s

The most important parameters of lightning are the following:
Lightning current amplitude iL – determines the resistive effects mentioned below

Average steepness of the lightning current diL / dt – determines the resistive and magnetic coupling effects mentioned below

Total charge Q = L * dt (unit As or C) – determines the energy release/conversion at the hit point

Specific energy  (action integral)
W/R = L2 * dt (unit MJ/ or kA2s) – determines all heating and electrodynamic effects along the down-conducting path.

Group 3 – lightning current of positive or negative polarity, long-duration stroke – DC 0.5 s

The most important parameters of lightning are the following:
Lightning current amplitude iL – determines the resistive effects mentioned below

Average steepness of the lightning current diL / dt – determines the resistive and magnetic coupling effects mentioned below

Total charge Q = L * dt (unit As or C) – determines the energy release/conversion at the hit point

Specific energy  (action integral)
W/R = L2 * dt (unit MJ/ or kA2s) – determines all heating and electrodynamic effects along the down-conducting path.