Lightning Protection with Bonding and Grounding
For many industries, such as the petroleum industry, the topic of lightning protection comes up frequently. This is not surprising since oil and gas facilities are usually large facilities, made mostly of metal, and sit exposed to the elements. It is not unusual to hear about either lightning strikes or the resultant static electricity causing devastating fires and damage to oil and gas facilities.
Lightning protection can be broken down into three steps, the first of which is proper bonding and grounding.
The following is an explanation of bonding and grounding in relation to lightning protection, including lightning protection for oil and gas facilities from Lightning Master CEO, Bruce Kaiser.
Bonding & Grounding
Bonding is simply a matter of taking all of the electrical and metallic masses in a facility and connecting them with conductors, bringing them to the same electrical potential. The primary reason for bonding is personnel safety, so someone touching two pieces of equipment at the same time does not receive a shock by becoming the path of equalization if the two pieces of equipment happen to be at different potentials.
For the same reason bonding protects people, it also protects equipment, by reducing current flow on power and data conductors between pieces of equipment at different potentials.
Grounding is a matter of bringing the bonded equipment mass to the potential of the surface of the earth which it occupies. Again, the primary reason is personnel safety, and the secondary reason is equipment protection. When it comes to grounding, we need to consider two types of grounding: low-impedance grounding of structures, and single-point ground potential referencing for services and equipment.
Low-Impedance Structural Grooming
A structure is anything that is likely to be struck by lightning. Multiple low-impedance paths to the grounding system transfer lighting energy off of the structure and into the ground as quickly as possible. Since lightning is very high frequency, low-impedance, the key to grounding is not just low-resistance, but the paths themselves. The higher the impedance the lighting energy “sees”, the greater the voltage increases. The higher the voltages, the more likely the energy will arc or take unwanted paths to ground.
Therefore, it is important to provide multiple paths with good geometry directly to the grounding electrodes within the grounding system.
Single-Point Services And Equipment Ground Potential Referencing
Why is it that direct lightning strikes at two similar facilities can leave one undamaged and the other virtually destroyed?
Among all the variables involved in system design, we have found the single most important factor in effective lightning protection to be not simply bonding and grounding of equipment and services, but the proper connection of the services and equipment bonding sub-system to the grounding system.
A change in potential per se does not damage equipment. It is a difference in potential across your equipment causing current flow through your equipment which causes damage. If the potential of the entire system changed at the same time and rate, and the equipment does not have any other source of ground potential reference, there is no current flow and no damage occurs.
Current divides and takes all paths. The proportion of the current flowing on any one path is proportional to the surge impedance of that path relative to the total surge impedance of all paths. Even if heavy duty bonding straps are provided between grounds as the primary intended path of equalization, some of the current flow will be through unintended paths; through other conductors and equipment.
Therefore, it is critical to bring all services and equipment grounds within a facility to the same potential before they connect to the grounding system, eliminating the possibility of current flow.
In a typical facility, we must be concerned with several different ground potentials. The first set of ground potentials is associated with the services to the site, i.s., AC power, TELCO, data and RF transmission lines from antennae. If a piece of equipment is connected to both a data line and to a power supply, and there is a difference in ground potentials between those two service grounds, that difference in potential can equalize within the equipment, causing damage or accelerated wear.
The second set of potentials is associated with the various electrical and electronic equipment chassis grounds. If two pieces of equipment are communicating with one another through a data line, and if there is a difference in potential between the two pieces of equipment, that potential can equalize through the data lines within one or both of the pieces of equipment.
When we refer to the facility equipment, it is important to note that we are referring only to electrical or electronic equipment, not door frames, air conditioning ducting, miscellaneous masses of inductance, etc.
To perhaps oversimplify the concept, envision an imaginary plane at or just below the floor level of the facility. All of the site equipment and services should be appropriately bonded together above this plane, and an appropriate grounding system established below this plane. All services and equipment grounds should pass through one and only one hole through that plane. Therefore, all equipment within the site will be at the ground potential of that single point. This concept is commonly referred to as “single point grounding”, or, more accurately, “single point ground potential referencing”.
Contact Lightning Master For More Information About Bonding and Grounding
If you need proper lightning protection for fuel storage tanks, chemical plants, or other facilities first call should be to Lightning Master. The truth is, bonding and grounding is a very complex science since lightning strikes and static electricity are extremely complex issues.
With Lightning Master Corporation on your side, you can rest assured that we will help to mitigate the threat posed to your facilities by lightning and static. Lightning Master Corporation has been in the business of lightning protection since the 1980s. Our team will conduct a site survey and make proper recommendations for lightning protection, static protection, and bonding and grounding.
Contact Lightning Master Corporation at (727) 447-6800 to schedule a site survey today.