Lightning currents inherently want to ground—whether the proper systems are in place or not. A lightning strike, which is intercepted by an air terminal, must have its current transferred to the earth safely and seamlessly.
The grounding system is the integral part of a modern electrical lightning protection system that must be dependable for this process.
Without an effective grounding system in place, dangerous ground faults, side flashes and electronic noise can occur, causing damage to structures, fires or personal injury.
What’s the Role of a Grounding System in Lightning Protection?
To understand the role of grounding, let’s first look at the four basic steps (or components) required to effectively prevent damage or injury from a lightning strike. They include:
- Interception of the Lightning Flash
- Conduction of the Lightning Current to Earth
- Creation of an Equipotential Bond
- Dissipation of the Current into the Earth
The grounding system is instrumental in the pivotal final step, as it enables the lightning current to dissipate quickly into the earth.
“Think of grounding as the foundation of a house that holds all of your electrical systems. Without it, the whole thing comes tumbling down,” says Earl Wilcox and Mark Lamendola from EC&M.
Why You Need To Ground
It is a fundamental fact that electricity always flows to the point of lowest potential. The task is to ensure that electricity (i.e. faults, lightning and electronic noise) flows to a point of maximum safety, while maintaining the reliability of equipment.
To do so, make sure to consider the following:
- Providing a low impedance network to dissipate the fast-rising lightning impulse.
- Minimizing potential touch and step hazards.
- Long-term performance of the system – i.e. quality of materials and connections.
Therefore, we must help ensure the safe, controlled flow of electricity with minimum voltage drops to earth in all cases.
Obstacles To Effective Grounding
The transient nature of lightning—with its associated fast rise times and large magnitude currents—means that special consideration must be given to grounding for lightning protection to be effective.
The concept is simple—allow the current to flow from the interception point to the ground—but making that happen is complex. It’s complicated because many factors influence the design of a grounding system, such as:
- Soil resistivity variations
- Installation accessibility
- Existing physical features
- Seasonal soil moisture variations
Soil characteristics, grounding conductor materials, grounding connections and terminations are all significant factors that determine the design of a grounding system.