Grounding:

What are earth, ground and grounding? Ground and earth are not necessarily synonymous .
• Literal earth is not always the end point of a ground. One example: An airplane contains many grounding points, but no earth connection while it is flying.
• Ground, in common electrical parlance is a system promulgated by NFPA (National Fire Protection Association) and the NEC (National Electric Code). It is designed solely to protect people from electric shock.
• “Grounding” is the term best used when talking about protecting equipment from electrical anomalies such as transient over-voltages. The ground wire network in a structure is usually used as part of a grounding system.
In general, earth is used as the depository of surges, which are carried from a protected structure or piece of equipment by the pathway (usually ground) of a well-designed grounding system.

A ground might be effective for its intended purpose (of protecting people), but be ineffective in handling surges . Hence, this document will concern itself solely with equipment protection grounding, whichever term is used. A proper grounding system inherently encompasses the NEC ground requirements.

As mentioned before, another vital consideration in protecting interconnected equipment at your facility is that every wire and cable tying equipment together constitutes a single circuit, and must not be considered as unrelated units. The single circuit must be comprehensively surge protected, and grounded effectively as a "single point".

That includes telephone lines, data and communications lines, sensor wires, AC and DC power lines, cables from a generator, propane gas tanks, antennas ….

Lightning strikes may give rise to harmful potential differences in, on and around a structure or facility. The major concern in the protection of facilities is the occurrence of potential differences between either the lightning protection system and other grounded metal bodies and wires belonging to the facility or between the many grounded bodies within and around the facility itself. These potential differences are caused by resistive and inductive effects and can be of such a magnitude that dangerous surges or sparking can occur. In order to reduce the possibility of this, it is necessary to equalize potentials by bonding all grounded metal bodies to the lightning protection system and to each other.
One factor that is difficult to control is the problem related to power and communication lines entering the structure. For all intents, such lines are at an earth ground potential relative to the extremely high induced voltages. If any of these lines are electrical, telephone, power, or data lines which are not bonded together as a grounding system, the voltage across the loop formed by these lines would be enhanced by the resistive effect described by Ohm's Law, and by an inductive effect to such a point as to cause a breakdown. All electrical lines and grounded bodies should be bonded together plus be bonded together through surge protection as specified in NFPA 780, thereby reducing the resistive component and controlling dangerous sparking and damage. However, if just one wire or grounded metal body stands alone and is not part of the grounding system, the danger to all of the components still exists.

Protection.
Due to the extreme lightning exposure incidence in Florida, and particularly in Central Florida (“Lightning Alley”), the recommended combination of lightning rods/grounding and higher industrial grade surge suppression is, we believe — a proper compromise between invest and cost-effective system performance, effectiveness, and protection durability. A more rugged, far more costly surge suppression system, which could be used in some parts of the facility, does not seem justified. Again, we are balancing a high level of effectiveness and cost containment (value) with additional durability.

1. Transient voltage surge suppression.

The subject for protecting electronic equipment is addressed in the recommendation which provides an effective and durable System Shield® approach to Transient Voltage Surge Suppression for the electronics in the facility.

It is important that suppressors be installed by electricians properly trained in surge suppressor installation! This is not a minor matter. Most electricians do not understand the specifics involved, and most manufacturers’ instructions are incorrect. A large percentage of installations we have to replace have been incorrectly installed, indeed, so poorly installed (although often “beautifully” so) that the surge suppressors never have seen any of the surges passing through the electrical system!

Also realize that no UPS is a surge suppressor unless it has been UL 1449 Second Edition Listed as such. If the equipment label on the case does not so list, please don’t accept the common misbelief! This applies particularly to such small stand-by UPS's as the APC boxes in use in the tower. Each of them should be plugged into an appropriate suppressor.

We are confident, based on technical sources and our own extensive experience, is that this recommendation, if completely implemented as designed, will greatly reduce or eliminate the costly necessity of replacing and maintaining all protected equipment at your facility.

CONCLUSION

Protection from lightning and surge damage to your entire, "single circuit" transmitter facility can be both effective and affordable, if implemented as a "seamless cloth". In the end, you will find that WTVT Fox Channel 13 will be operational as desired, with long-term savings in downtime, equipment degradation or destruction reduced to the practical minimum. Savings will pay for the facility's protection system time and again.

We invite those of you who wish to have a more detailed explanation, in plain English, of the poorly understood phenomena of lightning and transient voltage surges to read through the attached Appendices. These will help you place our recommendations in perspective.

THE LIGHTNING FLASH
In normal sunny weather, the Earth carries a slight negative charge while the atmosphere is correspondingly positive in electrical polarity. However during a storm, as the air becomes more turbulent, the polarities are reversed. The Earth becomes more and more strongly positive, while the lower portion of the thunderclouds develop an intensifying negative polarity.

Eventually, a stepped leader stroke of electricity is triggered and descends rapidly toward the Earth in steps ranging from 50 feet in length for a small-scale discharge, to several hundred feet in a high magnitude flash. As the stepped leader nears the Earth, positively charged Earth bound streamers flow upward from the trees, poles, corners, edges and peaks of roofs, as well as from other targets - including people. They may feel this occurring by their hair standing on end.

When the leader stroke reaches a point that is a step's distance from the nearest Earth bound object, a positive streamer shoots upward to meet the leader, completing an ionized or conductive path between the cloud and the Earth. Immediately, the negative charge laid along the ionized path flows to Earth.

The leader stroke is typically followed by two or three "dark leader" strokes that do not stop. Each of these strokes brings additional negative charges to Earth. Each flow of current super heats the surrounding air, which literally explodes outward from the current streams, creating the intense lightning flash, as well as the accompanying thunder that we hear.

NLSI Note: The below random factoids are designed for readers who need to tell others about lightning. From students to network newsiest...this stuff is for you. It’s like fertilizer...it’s intended to be spread around.

NLSI is a group concerned with lightning safety issues. We conduct several types of education seminars. We perform site audits and we inspect facilities to assure "best available technology" for lightning safety. We have no products to sell. We represent no special interest group.
Lightning comes from thunderstorms (and snowstorms and volcanoes). Lightning is static electricity on a giant-scale. There are some 2000 thunderstorms globally at any one time producing some 100 lightning strikes to earth per second. In the USA, there are about 15-20 million ground strikes per year. Florida has the most strikes - about 12 strikes per square kilometer per year in some places. On average, more people are killed by lightning than any other weather event. There is more than $2 billion damage annually in the USA from lightning.

Your risk of being killed by lightning is 1:28,500 per exposed individual. (NPH Newsletter January 1992)
The average flash could light a 100-watt bulb for more than 3 months.
Lightning's heat exceeds 50,000 degrees F. (three times hotter than the surface of the sun). Its’ speed is 90,000 miles per second (one hundred million feet per second). The average thickness of a bolt is 1-2 inches.
It’s wrong to say lightning can be "stopped" or prevented. It is a totally capricious, stochastic (look that up!) and unpredictable event.
The "lightning code" in the USA is called NFPA-780-1995 and was written by lightning rod salesmen. Compare it with the European code, TC-81, written by scientists and engineers.
Thunder is always associated with lightning. Thunder is the shock wave created by super heated air in the lightning channel.
Some good specialized publications on lightning are:
1. General subject matter:- Uman, M "Lightning", Dover, 1984.
2. Uman, M "All About Lightning", Dover, 1986. -Viemeister, P., "The Lightning Book", MIT, 1972.
3. Medical subjects: - Seminars in Neurology, Parts I & II (Sept & Dec 1995)
4. Thunderstorms: - Kessler, E "Thunderstorms, A Social, Scientific, and Technological Documentary", U. OK Press, 1992.
5. General Weather: Williams, J "The Weather Book", Vintage Books, 1992.
6. Weird Weather Phenomena: Corliss, W "Lightning, Auroras, Nocturnal Lights and related luminous phenomena", Sourcebook, 1992.
Nine out of ten people struck by lightning survive the event. But nearly 25% of these survivors suffer long-term psychological or physiological trauma. The best defense against lightning is preparedness.

What’s good about lightning? It produces a lot of the nitrogen compounds that are important for plant growth. It provided early man with his only source of fire. It’s better than fireworks on the Fourth of July and it’s free!
The average lightning strike contains 20,000 amps. [One National Weather Bureau website lists a measurement in excess of 1,000,000 Amps and hundreds of thousands of Volts.] An arc welder uses 250- 400 amps to weld steel. Your house probably uses only 200 amps. Current in excess of 20 milli-amps can cause your chest muscles to contract, stopping breathing.
The worst lightning incident (so far) in the USA was in New Jersey, on July 10, 1926. A Navy ammunition arsenal was hit, killing 19 people and destroying property valued at $17 million (1986 dollars). Usually, single events caused by lightning are less dramatic than single events caused hurricanes, floods or tornadoes. If you are the victim, however, it is plenty dramatic.
It’s wrong to say lightning never strikes twice. It hits the Empire State Building, on average, 21-25 times per year. A US Park Service Ranger, Ray Sullivan, was struck by lightning seven different times between 1942 and 1976. Yep, he survived them all. (We don't know if his hair was curly.) [There can be 15 or more discharges in one lightning strike.]
Beware of sheltering under tall trees during a storm. (Trees contain some 20% moisture content. We humans have 65% moisture content.) Lightning coming down a tree wants to follow the path of least resistance: TAG - YOU’RE IT! Get to an all-metal vehicle like a car or a truck if you can. That’s the safest place.

APPENDIX B

NLSI: “How’s” and “Why’s” of Lightning Protection"

Why You Need Lightning Protection:
Lightning protection systems have changed drastically since Benjamin Franklin first invented lighting rods in 1752. Today's systems must protect modern appliances, electrical systems and building constructions - they have to keep up with tile changing requirements of modern technology.

Underwriters Laboratories Inc. (UL) keeps up with these changes. Our experience in the safety-testing field has earned UL worldwide recognition and respect. Jurisdictional authorities, government agencies, insurance representatives and consumers alike have looked for the UL Mark on products and systems for almost 100 years. When you see the Mark, it means that the product or system on which it appears compares with UL's internationally recognized Standards for Safety.

In the lighting protection field, UL has been serving home and building owners since 1908. Today, UL has a large number of trained lighting protection field representatives located throughout tile United States. UL inspects sites ranging from cow barns to missile silos, front golf Course shelters to high-rise building systems. In fact, some of the most famous buildings in the world are protected by UL Master Labeled lightning protection systems, including the White House, the Sears Tower and the Washington Monument.

The Need for Lightning Protection:
Lightning can strike anywhere on earth - event the North and South Poles! In any U.S. geographical location, lightning storms occur as few as five times or as many as 100 times per year. -The Northeast United States has the most violent thunderstorms in the country because of the area's extremely high earth resistivity. High earth resistivity (the earth's resistance to conduct current) increases the potential of a lightning strike. If struck, structures in these areas will generally sustain more damage when there is no lightning protection system present.

Each year, thousands of homes and other properties are damaged or destroyed by lightning. It accounts for more than a quarter billion dollars in property damage annually in the United States. Lightning is responsible for more deaths and property loss than tornadoes, hurricanes and floods combined, but of these violent forces of nature, lightning is the only one we call economically affords to protect ourselves against.

Some properties have a higher risk of lightning damage. When considering installation of a lightning protection system, you may want to assess this risk. A risk assessment guide for determining lightning loss for all types of structures can be found in Appendix I of the National Fire Protection Association's Lightning Protection Code, NFPA 780. This guide takes into consideration the type of structure, type of construction, structure location, topography, occupancy, contents and lightning frequency. Information may be obtained from tile NFPA, I Batterymarch Park, Quincy, MA, 02269, (800) 344-3555.

How a Lightning Protection System Works:
Lightning is the visible discharge of static electricity within a cloud, between clouds, or between tile earth and a cloud. Scientists still do not fully understand what causes lightning, but most experts believe that different kinds of ice interact in a cloud. Updrafts in the clouds separate charges so that positive charges moves end up at the top of the cloud while negative flow to the bottom. When the negative charge moves down, a "pilot leader" forms. 'This leader rushes toward the earth in 150-foot discrete steps, ionizing a path in the air. 'The final breakdown generally occurs to a high object the major part of the lightning discharge current is then carried in the return stroke which flows along the ionized path.

A lighting protection system provides a means by which this discharge may enter or leave earth without passing through and damaging non-conducting parts of a structure, such as those made of wood, brick, tile of- concrete. A lightning protection system does not prevent lightning from striking; it provides a means for controlling it and preventing damage by providing a low resistance path for the discharge of lightning energy.

Lightning protection system for a dwelling: 1) air terminals spaced 20 feet apart along ridges and within two feet of ridge ends; 2) down conductors; 3) minimum of two groundings at least 10-feet deep; 4) roof projections such as weather vanes connected to system; 5) air terminal located within two feet of outside corners of chimney; 6) dormers protected; 7) antenna mast connected to roof conductor:- 8) connect gutters or other grounded metals as required; 9) surge arrester installed at service panel to protect appliances; 10) transient voltage surge suppressors installed in receptacles to which computers and other electronic equipment are connected.

Lightning protection system commercial/industrial installation 1) air terminals spaced 20 feet apart around the perimeter of the building; 2) down conductors; 3) ground rods at least 10-feet deep; 4) art handling units bonded to system (may be in need of air terminals mounted on unit); 5) air terminals mounted within two feet of outside corner; 6) mid-roof conductor and air terminals at maximum 50-foot spacing; 7) grounded metal bodies bonded into system; 8) surge arresters installed at main electrical panels; 9) transient voltage surge suppressors installed in receptacles to protect computers and other office equipment.

UL's Role in Lightning Protection:
UL's Master Label Program for lightning protection involves periodic factory testing and inspection of system Components, along with field inspection components of completed installations. The program requires that all installers comply with UL’s internationally recognized Standards for lightning protection components and systems. UL’s field representatives countercheck compliance with these Standards.

As a home or building owner, you should make sure that your installed system complies with the UL requirements. Here’s how:

Make certain that your installer is listed by UL and that a Master Label application is submitted to UL for your installation. When You request a Master Label for your system, your installer will ask you to sign the owner’s statement on the Master Label application form. The fourth (yellow) copy of the application is for your records. This should be done before the installer submits the Master Label application to UL for issuance of the Label. Make sure you receive the Master Label from the installer and place it on the protected structure as requested.
Buildings that are changed structurally or provided with additions can be re-examined under UL’s Reconditioned Lightning Protection Program. Under this program, the entire system must comply with the current UL Standards.

How You Can Protect Your Building:
1. Install a UL Master Label Lightning Protection System that complies with current nationally recognized codes. Lightning protection systems consist of air terminals (lightning rods) and associated fittings connected by heavy cables to grounding equipment, providing a path for lightning current to travel safely to ground.

2. Install UL Listed surge arresters at your service and telephone equipment to prevent surges from entering the home or other buildings oil power or telephone lines. Surges are diverted to ground, and both wiring and appliances are protected.

3. Install UL Listed transient voltage surge suppressors in receptacles to which computers and other electronic equipment are connected in order to limit the voltage to 11/2 times the normal (maximum for solid state devices).

APPENDIX C

EQUALPOTENTIAL GROUNDING (COMMON GROUNDING):
Interconnecting to the system using main size conductors and fittings shall ensure common grounding of all ground mediums entering the building.
Grounded metal bodies located within the required bonding distance as determined by the bonding distance formulas in Section 3-23 of NFPA-780 shall be bonded to the system using bonding connections and fittings.

GROUND TERMINATIONS:
Ground electrodes shall be provided for each down conductor and shall consist of 5/8" x 10'-0" (minimum) copper-clad ground rod. The down conductor shall be connected to the ground rod using a bronze ground rod clamp having at least 1-1/2" of contact between the rod and the conductor, measured parallel to the axis of the rod, or by an exothermic welded connection (recommended). Ground rods shall be located 2 feet below grade, preferably 2 feet from the foundation wall and shall extend a minimum of 10' vertically into the earth.
Where the structural steel framework is utilized as main conductors for the system, perimeter columns shall be grounded at intervals averaging not more than 60 feet apart. Columns shall be grounded using bonding plates having 8 square inches of surface contact area or by exothermic welded connections. Conductors from the ground connections to the ground termination shall be Class II copper lightning conductors.

INSPECTION:
Upon completion of the installation the contractor shall furnish the Master Label issued by Underwriters Laboratories Inc. for this system. If the protected structure is an addition to or is attached to an existing structure that does not have a lightning protection system, the contractor shall certify that the system installed complies with UL requirements and advise the Owner of the lightning protection work required on the existing structure to obtain the Master Label. If the existing structure does have a lightning protection system, the contractor shall advise the Owner of any additional work required on the existing system to bring it into compliance with current UL requirements and thus qualify for the Reconditioned Master Label of Underwriters Laboratories Inc.