GROUNDING & BONDING – THE BASICS
The first step toward safe and stable operation of AC powered electrical and electronic devices are a properly designed and installed grounding system. The importance proper & appropriate grounding and bonding can not be overstated. The foundation of a building is critical for the structure of the building to function and survive. The foundation of your electrical system is the grounding system.
Grounding, equal potential bonding are the most basic elements of the electrical design and installation. Lightning protection, and surge protection are interdependent technologies that rely on proper low resistance and low impedance grounding and bonding. It is not possible to over state the importance of grounding and bonding. The best example possible is to show the positive of what can transpire when lightning strikes an electrical system directly:
The above example defines the importance of a grounding system and the proper bonding when lightning strikes. Can you imagine the what the outcome would have been if this data center did not have the grounding, bonding and surge protection system they had installed?
Today, proper and appropriate grounding far exceed the NEC requirements for life safety grounding. Due to the wide range of soil and installation conditions most o!en selection of materials and grounding system design is complicated at the very least. In addition to the basic design provisions must be made for future testing of the system installed. Long gone are the days when a ground rod(s) is driven and forgotten until a problem is experienced. The design of a proper and appropriate grounding and bonding system should be completed by a competent professional that will most o!en be a licensed professional electrical engineer (PE) with significant experience in what is o!en termed “high performance grounding and bonding”.
Equal potential bonding is required for structures, equipment and systems with more than one ground reference. Not only is bonding required for life safety, it is also critical to for networked equipment. The most sophisticated surge protection devices and systems protection equipment can not protect networked equipment from damage without proper and appropriate equal potential bonding.
The reliable protection of a facility from lightning can not be achieved without low- impedance grounding and bonding. An air terminal can not capture and dissipate lightning energy without a low impedance path to ground along with low resistance & impedance earth grounding. Any such system should be designed to meet NFPA-78 and UL (Underwriters Laboratories) master label standards. In addition to those minimum standards, it is important to install lightning protection systems so they are sustainable and to best possible industry standards. For more on the di”erence between “code minimum” or “standards minimum” contact PSI-Tampa for additional information.
The most expensive AC power surge protection device (SPD) will provide poor performance without a low impedance path to ground. Low voltage surge protection devices can induce ground surges to protected networked equipment if ground loops are present. Many such devices do not function without a low impedance path to a single point grounding system.
To better better understand a SPD you need to understand how they function. SPD (o!en called TVSS) are diversion devices. They are preset to turn on if the electrical voltage exceeds their turn on point. If you understand the function of the pressure relief valve on a hot water heater you understand the plumbing version of a SPD. The pressure relief valve does nothing until the pressure in the hot water system exceeds a safe level and it opens (diverts) to reduce the pressure. That is the function of a SPD does in the electrical system, divert excess voltage. The hot water systems pressure relief valve depends on a pipe that will allow the excess pressure (water) to be sent away from the system to reduce the pressure to a safe level. This is exactly what the SPD must have as well to function. The SPD needs a “path” that is low in resistance to send the electrical pressure (voltage) away (call it the pipe that is not clogged) so it will not damage electrical and electronic devices. Knowing a <5-Ohm ground and proper ground bonding will provide the path (pipe) needed to dissipate the over voltage what do you think the results will be if the ground is not proper for the SPD to function properly? Imagine lightning strikes, the SPD turns on and it cannot send the lightning energy (voltage) away from what it is trying to protect. So just having a SPD is not worth much if you don’t have the conditions needed for it to function properly.
The sophisticated noise (EMI & RFI) shielding can not dissipate unwanted noise without a low resistance / impedance path to ground. The shields of electronic equipment must have the path they require or the equipment may not function properly.
The most basic reason for grounding is life safety. The goal is to eliminate shock hazards of all conductive enclosures that may be touched by personnel.
Provide protection from large electrical disturbances (such as lightning) by creating a low resistance path to earth.
Reduce Static Electricity that may be generated within facilities.
Limit voltage in an electrical distribution system to definite values.
Limit voltage to within insulation ratings.
Provide a more stable system with a minimum of transient over voltage and electrical noise.
Provide the proper conditions for power quality devices to operate to their design specifications. (SPDs, UPS, Power Conditioners, etc.)
Provide a path to ground in fault conditions for quick isolation of equipment with ground fault protection.
Improve the operation of equipment sensitive to electrical noise.
Provide a stable platform for the operation of sensitive networked equipment.
Increase the life of electrical and electronic devices.
Eliminate ground loops (di”erence in ground potential).
Improve the e”ectiveness of network, control and loop SPD’s.
Increase the e”ectiveness of EMI & RFI shielding.