The Lightning Phenomenon
Lightning,
an awesome and terrifying natural phenomenon, is really nothing more
than an electrical discharge that happens to be at an enormous voltage.
Lightning equalizes a difference of electrical potential, whether it
is between a cloud and the ground, between two clouds, or between two
different areas of the same cloud. Due to various mechanisms in storm
cloud formation, such as the rising and falling of air currents carrying
moisture and ice particles, the storm cloud generates an electrical charge
at its base. Charged regions in a thundercloud create conductive ionization
channels through the atmosphere called “stepped leaders,” while an opposite
electrical charge or “shadow” accumulates on the ground below.
These
leaders jump and branch ever downward in a quest to connect with their
oppositely charged image or “shadow” on the earth's surface. As the fiercely
charged electrical field builds, streamers rise from objects on the ground.
When a stepped leader from the sky chooses to meet the strongest rising
streamer from below, a lightning “circuit” is completed. The main lightning
stroke erupts up the ionized path. Numerous additional strokes along
the same channel are common, creating a mesmerizing strobe light effect.
We are most interested in protecting our clients from the “shadow” and
its resulting electrical discharge--a lightning strike.
Whatever lightning protection method is implemented, the importance of the grounding system supporting it cannot be overemphasized. A well designed, correctly installed, low impedance and low resistance connection from the earth to the components of the lightning protection system is essential. With the addition of transient voltage surge suppression devices, a comprehensive facility protection approach addressing all concerns of safety and power quality finally is made possible. Only then may we watch in unflinching wonder as the sky explodes in its timeless electrical display.
Protection Methods for Lightning Strikes
An overview of the technologies used to protect against lightning strikes
The traditional passive Franklin-style lightning rod system simply seeks to offer a preferred point of strike and further direct the energy of a lightning strike harmlessly to the earth through a safe low impedance path. Whereas, both charge
dissipation and early streamer
emission (ESE) technology systems seek to actively defend an area on the earth's surface by using the “upward streamer” aspect of every lightning “circuit” in two very different ways.
The charge dissipation,
or charge redistribution, terminal uses numerous sharp metal electrodes to generate a rapidly dispersing
corona of ions to lower induced surface charge, effectively delaying
or mitigating the formation of a rising streamer. In contrast, an early
streamer emission terminal actively uses the increase in ambient energy,
which precedes a lightning strike, to initiate its own upward streamer
earlier and stronger than
would naturally occur. This ensures that
the leader is attracted to a certain low impedance path to ground and
causes the streamer to meet the leader much higher than the point of
the ESE, thus, providing a larger area of protection. These modern
technologies reflect today's greater knowledge of the formation, generation,
and termination of the truly beautiful and destructive phenomenon that
is lightning.
Types of Lightning Damage
A look at different damages caused by lightning
There are three types of lightning damage: direct lightning strike, secondary, and electromagnetic. The first and most physically impressive type of damage is sustained from a direct lightning strike. The sheer impact of tens-of-thousands of amps at 100 million volts striking an area the size of a half-dollar is both spectacular and destructive. Secondary effect damage is caused by the movement of electrical charge from the surrounding area to the point of a lighting strike. This movement of charge, caused by the difference of potential between the strike point and the surrounding area, produces an electrical current through the ground and structures on it. Electromagnetic effects are produced by the on-and-off arcing of lightning “return strokes.” In accordance to general electrical theory, if a magnetic field is passed back and forth across a conductor, an electrical charge on the conductor will be induced. The on and off arcing of lightning return strokes, which produce an electromagnetic pulse, will induce electrical currents in conductive materials
Alltec Protection Pyramid
Alltec's approach to comprehesive lightning protection
Lightning is an unpredictable act of nature. A “bolt from the blue” can occur 10-20 miles from the cloud source, and power transmission lines can carry extreme voltage transients many miles. It is prudent that certain steps be taken to protect people, equipment, and buildings; the TerraEval Advanced Solution Assessment engineering service is specifically designed for this purpose. Alltec's three-step Protection Pyramid implementation begins with the installation of a stable, low resistance and low impedance grounding system to bond all electrically conductive surfaces together. TerraDyne, TerraFill, TerraBar, and TerraWeld grounding product lines are utilized to safely direct lightning energy to the earth and away from equipment and structures. After providing a stable grounding system, it is important to properly install a transient voltage surge suppression (TVSS) system, such as our PowerTrip line of TVSS products. Only then, is equipment truly protected from both open and short circuit transients traveling on incoming electric, rf, telephone, coax, and data lines, as well as other internal equipment, and from direct surges, secondary, and electromagnetic effects. Finally, a well-designed structural lightning protection system will be installed. TerraStat, TerraStreamer, and traditional lightning protection products, are offered to fulfill this role of ensuring safety from direct lightning strikes.
We ensure our customers the highest caliber of services and products through our continual investment, testing, and evaluation of lightning protection, grounding, and transient voltage surge suppression (TVSS) components and systems. Innovation and sound engineering practices combine in Alltec Corporation's research efforts. We partner with and direct national and international university level experimentation, analysis, standardization, and certification efforts in the field of lightning protection and grounding systems. Furthermore, our products are independently tested by preeminent scientific laboratories, universities, and certification authorities. Unequivocal results back up our Alltec Advantage.
