The effectiveness of a lightning protection
system is one where the principle is to minimize or avoid direct lightning discharge
on installations we want to protect, and to avoid all kinds of risks such as
human death, accidents or fire caused by voltage differences or surges during
the lightning strike.
Introduction
The
lightning phenomenon:
According to the world weather detection
system, around 44,000 storms generating more than 8,000,000 lightning strikes
happen during every second of every day around the world.
This
is reference data because the evolution of weather is affecting lightning
activity off season and even in winter or during snow storms.
A lightning strike is the electrical
reaction caused by the saturation of electrostatic charges that have been
generated by progressive accumulation of the electrical field between earth and
cloud during the start of a typical storm. In a fraction of a second during the
lightning discharge, the accumulated electrostatic energy becomes
electromagnetic energy (the visible lightning strike and the sound
interference), acoustic energy (thunder) and finally heat.
The lightning phenomenon is represented by
an atmospheric electrical potential (10/45 kV). It is previously generated
between two points of attraction of different polarization and equal potential
in order to compensate for the saturation of electrostatic charge.
The lightning’s charge density is
proportional to the electrostatic charge saturation of the area. The more
density charge in the cloud, the bigger the risk of generating a leader in land
and a lightning strike. The intensity in the lightning discharge is variable
and will depend upon the critical moment of the air resistance break between
the two reference points. The resistance
of the exposed materials like land, rock, wood, iron, lightning installations and
grounding will influence it, but will not limit the place of the strike, only
its intensity. Lightning can transport an electric charge equivalent to 100
million ordinary bulbs in less than a second. The average measured charge per
lightning strike is 20GW.
Once the lightning is formed, its
trajectory can be chaotic, it will always predominate the power charged
environments in the earths natural high voltage field. This electrical
phenomenon is represented as an electrical shadow that will determine the
elements that will be affected by the exchange of charges inside the natural
high tension field.
Studies of the atmospheric electrical field
around the earth determine that the charge distribution during the generation
of the earth’s high tension field is not static but dynamic, by generating the leader
in motion and different geographical points at the same time. The intensity and location of these
electrical shadows can change radically and affect the sides and low parts of
high buildings or structures.
Once the lightning is formed, the area of
impact or the intensity of discharge cannot be guaranteed unless there is
adequate protection.
Lightning
causes great economic losses.
According to references from 2002,
lightning causes more than 5 billion dollars in economic losses to the United
States alone.
Reference values for lightning :
- Voltage between cloud and an object on
earth 1. To1.000. KV
- Intensity
of discharge 5 a 300 KA
- di/dt 7.5kA/s to 500kA/s
- Frequency
1 K Hz to 1 M Hz
- Time 10 microseconds to 100 milliseconds
- Temperature
higher than 27,000 degrees
Celcius
- Propagation 340
meters per second
- Electrostatic field/meter of elevation from
land 10 kV
This data is only for your information since
it is only proportional to the intensity of the cloud’s charge and the
intensity of the lightning strike in each geographic zone.
The electrical phenomenon reverberated by a
lightning impact, directly or indirectly during its strike, will vary according
to the environment or installation that it finds in its path, where variable voltage
values will appear depending upon material resistance, structure, situation and
humidity of the ground grounding rod dissipation rate, absorption time of the
physical land’s mineral compound, electrode’s crystallization state, etc.