Lightning Damage Can Be Prevented

Questions from the field and items of fact or opinion

• During the past several decades, lightning protection systems, over-voltage absorbers, surge suppression, along with grounding and bonding have become essential components in today's micro processor electrical environment. What does one need to know about protecting equipment?

How can you determine what your facility really needs?
• A facility survey is usually the first and best recourse. (I.E. Medical doctors need each patient to visit the office for an examination prior to diagnosis and prescription.) We feel an office visit is required to evaluate the protection needs and facility/site condition with respect to the sensitive electrical equipment. (I.E. Electric heaters that create tremendous power surges have been found plugged into the same AC outlet as computer workstations.) Although there are basics that can be applied that will offer partial protection to sensitive equipment, the quality of the protection system can be sacrificed due to a lack of experience in comparing industry products as well as a lack of knowledge that would produce an incomplete protection system. Once an incomplete system is installed the client would have a false sense of protection until damage occurred.

We have surge protector strips on all our Network Center computers. Are we protected from a direct lightning strike?
• Mike's Opinion: First let's define a direct lightning strike. In a lightning strike, did you loose block, brick, mortar, roofing, tin or damage occurred to the building? The usual answer is no, we lost computers, micro wave, monitors, answer machines, telephones, etc. If the answer had been yes, then there may have been a direct lightning strike to the building. Yes, it does happen with tremendous damage and/or fires. However, most damage to electrical equipment from a lightning event enters the equipment through conductive pathways connected to the equipment. (IE. Electrical lines, telephone lines, coax cables.) According to national reports, 80% of computer damage from insurance claims is from power surge events. This can mean surge events created by lightning as well as other power quality anomalies.

How can we determine if we need transient voltage surge suppression also known as TVSS?
• And what is a TVSS device anyway? Mike's Opinion: A TVSS device is specifically designed to guard your electronics 24 hours a day. An effective TVSS device electrically monitors the conductive pathway where it is connected and diverts or absorbs the heat energy created by a surge event. It is imperative that the TVSS installed have the ability to offer effective protection on all conductors connected to the electronics. These conductors may include phase, neutral, and ground wires for alternating power (AC), positive and negative conductors for direct current (DC) along with each conductive pathway of signal cables, coax cables and telecom cables. In many cases, the TVSS device is designed to sacrifice itself to save the electrical equipment it is protecting. We offer unlimited free product replacements without conditions for 25 years if this occurs. We feel that in today's world of electronic controls all electrical equipment should be protected from constant bombardment of transient voltage surge events. Many times, electrical equipment is manufactured with some small form of protection already installed when it is assembled. Normally this protection is very minimal due partly to product manufacturers needing after delivery profits from the sale of parts to repair the damaged equipment. (I.E. Television repair shops know about protection for TVs but seldom suggest protection when you take the TV in for repair since it will directly effect their repair business. We know of one equipment manufacturer that actually gives their pumps away free as long as you agree to a 10 year parts and labor contract.) Read this next statement and answer the question yourself. "Consider the result of providing an electrical system with clean, stable, consistent voltage and current with no imbalance times, no interruption outages, no sags, and no brown outs; similar to what may be experienced in a test laboratory. Do you feel that electrical equipment would be more reliable, last longer and perform better?" Yes, we think so too.

Is a Surge Protection Device (SPD) the same as a TVSS device or surge protector?
• Mike's opinion: Yes, one in the same. However, TVSS designs vary from A to Z. We know there are hundreds of TVSS manufacturers and many devices are "look-a-like" products offered to gain profitable sales from consumers and unsuspecting engineers. Some TVSS devices are even built with degrading components and for best protection results they should be replaced every 30 days but the manufacturer will not advertise this fact. (No one would buy their device if it has to be replaced every 30 days.) Another area to gain knowledge is testing of the TVSS devices to evaluate product specifications. ANSI/IEEE C62.41 offers parameters to conduct testing of TVSS devices. The test results can be utilized for comparison evaluation but we feel that testing along with proven in-the-field long term effective results go hand-in-hand. In the day of computers and printers, everyone has a specification that looks good on paper. Underwriters Laboratory (UL) is one of the nation's businesses that will test TVSS devices. Also note that UL is a "for profit business" with an obligation to stay in business as well as produce safety regulated products. The UL circle label usually means that the device was tested for safety and should not shock you, or catch fire, or explode when connected to electrical current. In the TVSS industry, the UL circle label does not mean the unit was tested as an effective surge protector. UL1449 Second Edition will offer testing for TVSS products that designates a suppressed voltage level (let-through voltage) for specific voltage/amperage and waveforms. There is no guarantee that the TVSS device will last since UL does not require life cycle testing. But with defined test levels the specifications can be evaluated for proper application and narrow the search to the best TVSS performers which then can be narrowed to application, warranty, service, and cost. Selecting the best TVSS for the job should not be a hit-or-miss selection method or even a call to the nearest electrical supply house. We find supply houses sell what they have available and engineers specify what they know until documented otherwise. We suggest doing your homework to learn what to look for and where to find the answers.

Do we need surge protection if we have lightning dissipation arrays, lightning rods (air terminals) or a lightning protection system installed on the roof?
• Mike's Opinion: Research has documented proof that lightning will strike taller objects, whether metal, wood, mortar/block or other compositions. Rods, arrays and such are designed to divert the strike to ground level in the attempt for a safe dissipation of the strike event into earth/dirt. So, yes, lightning rods have a function to provide a cone of protection. And yes, surge protection is still required since a lightning strike can miss the facility and enter by way of conductive pathways that connect the facility to electrical systems, telephone networks and antenna systems. Many lightning strike events can be miles away and travel the conductive pathways reaching equipment and causing tremendous equipment damage. The most effective protection method for the conductive pathways is to install TVSS at the entrance of each conductive pathway entering or leaving a facility. This will offer at least one stage of protection before the wiring enters the building/site. However, one TVSS device has not been documented as the best protection method. One device will interrupt the surge event and reduce the amount of voltage attempting to enter on the conductive pathway but the remaining voltage (let-through-voltage) can still be of significant amount to damage electronics. Installation of a stages or cascading of TVSS devices has been documented to consistently reduce the surge event to harmless levels. (Please request additional information regarding complete facility protection packages.)

We have a plug in surge protector strip on the commander's computer, printer, TV and VCR. Will he be able to leave his computer and video system operating during lightning storms?
• Mike's Opinion: No, I wouldn't. We provide the best plug in protection on the market, but I still would not leave my equipment to the result of only one plug in protector. When we install protection packages at Civil Defense Centers and National Weather Centers that power up during storms and inclement weather, they have much more than a plug in surge protector. A protection system for AC power alone would start at the Main Service Entrance of facility power and add protection down the conductive pathway to distribution panels, generator panels and end with a plug in protector at the outlet. In your example, the protection that is installed has begun protecting at the outlet and let-through voltage from a surge event after the protector worked could still damage the electronics.

Some microprocessor controlled (computer) electronics have factory requirements for internal surge protection components. Should there be a need for additional protection and is there a difference between computer protection and non-computer protection?
• Mike's Opinion: Metal Oxide Varistors (MOV) are commonly installed inside a computer as well as other electronics to offer minimum protection for 30-90 days. Ever wonder why products are guaranteed for 30-90 days.) Documented testing has proven that MOV's degrade and become non-effective way before the life span of the electronics, usually 30-90 days. Additional protection should be a requirement for all microprocessor electronics. And yes, there is a vast difference between effective protection products designed for computer electronics and protection for equipment with inductive motors such as heating/air conditioning (HVAC), refrigeration, pumps, motors, lighting systems, etc. Documentation has proven that effective TVSS can have the following results: motors last 65% longer without service, fluorescent light bulbs last 75% longer, and computer circuit cards last 95% longer. Calculate the annual savings and you will understand how many facilities document 100% return-on-investment within 6-12 months. We offer a broad selection of specifically designed TVSS devices that will fit most all applications and facility requirements. Inductive motors create surge events when they cycle on and off. The electromagnetic field collapses and a surge event is created. Degradation of motor windings and such attribute 75% of motor failure to surge related events. However, inductive motor insulation can handle more current than computer power supplies. Insulation is rated at double the voltage plus 1000. So to meet insulation standards, a 120 volt motor should be using insulation rated for 120+120+1,000 = 1,240 volts. Testing at 120 volt outlets has documented results of surge events reaching 6,000 volts. So what do you think will happen when 6,000 volts reaches motor insulation rated at 1,240 volts? The answer is premature motor failure. Yes, TVSS devices can save inductive motors, appliances and large equipment. Also note that computers use 120 volt from the power cord and then transform it down to low 2-10 volts DC. So if the same insulation rating is utilized, what will happen when 6,000 volts reaches the computer power supply and circuit cards? That's right, meltdown, computer crash, hard drive lock, reboot, monitor blackout, etc. And yes we offer different TVSS protection devices for micro processor computer circuits and inductive motor applications.

Where can we gain authentic lightning protection and TVSS educational information to help us make a wise decision?
• Mike's Opinion: We offer excellent educational seminars from several hours to all day with C62.41 TVSS testing. And then there is the preferred list of reading material: NFPA 70 National Electrical Code (NEC); NFPA 780 Lightning Protection Code; UL 96 Lightning Protection Components; UL 96A Installation Requirements for Lightning Protection Systems; AF Regulation 91-43 Maintenance Responsibilities for Air Force Grounding Systems; AFP 91-38 Maintenance of Electrical Grounding Systems; MIL-STD-188-124B Grounding, Bonding and Shielding; AFI 32-1065 Civil Engineering Grounding Schedule; MIL-HNBK-419 Military Handbook; ANSI/IEEE C62.41 UL 1449 Second Edition Transient Voltage Surge Suppression; ANSI/IEEE Standard 1100 Emerald Book, Powering and Grounding Sensitive Electronic Equipment; IAEI Soares Book On Grounding; FAA-STD-020 Transient Protection, Grounding, Bonding and Shielding Requirements for Electronic Equipment; FAA Order 6950.19 Practices and Procedures for Lightning Protection, Grounding, Bonding and Shielding Implementation; FAA Order 6950.20 Fundamental Considerations of Lightning, Protection, Grounding, Bonding and Shielding; ASTM F1507-94: Standard Specification for Surge Suppressors for Shipboard Use; MIL-S-901D: Shock Tests for High Impact Shipboard Machinery; MIL-STD-1399 Section 300A: Interface Standard for Shipboard Systems, Electric Power, Alternating Current; MIL-STD-167-1: Mechanical Vibrations of Shipboard Equipment; MIL-STD-461D: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment

We have protectors listed on the schematic of the Airport Surveillance Radar (ASR) but we still have damage to line drivers, power supplies and signal lines. What can be done?
• Mike's opinion: Most ASR sites have one of the best earth electrode ground systems installed. Therefore, we offer a custom manufactured and installed protection package for ASR sites that has been very effective for over 10 years. I remember seeing an annual maintenance report from Eglin AFB that showed a flat line graph for the year after our protection package was installed. In preparation of the PWIG briefing, it was noted that in the previous year 65% of service had been to electrically related damage. We are experienced with AN/GPN12, GPN20, GPN30 DASR along with ASR 7, 9, 11 and others. We have also designed protection packages for commercial radar systems operating in England, Italy, Korea, Japan, and Mexico. We also have protection packages available for the NEXRAD, MPN14K. MAC and other systems like the MMLS, LANTIRN, and ACMI. (See the USAF letters posted on this site along with the ATCAL & ASR Photo Report and ATCAL Equipment List.)

There are protection cards installed on the (ATCAL) Instrument Landing System (ILS) Localizer (LOC) and Glideslope (GS). But, we still have damage from lightning storms to the equipment and protection cards. What can be done?
• Mike's Opinion: ILS sites usually have pretty fair earth electrode ground systems but some could be improved with better bonding to the electrical ground, signal demarc ground as well as antenna and tower grounds to complete the requirement. Like the ASR, we offer a custom manufactured and installed protection package for ILS sites that has been very effective for over 10 years. We are experienced with most ILS installations including the new 2100 series. (See the USAF letters posted on this site as well as the ATCAL Photo Report-ILS.)

There are surge protection cards installed on the Navigational Aids (NAVAIDS) and Meteorological Sensors (METNAV), but, we still experience lightning damage to the visibility sets, digital winds and ceilometers. What can be done?
• Mike's Opinion: We have installed many custom manufactured protection packages to this equipment with excellent results. Many of these sites have much room for grounding and bonding improvements. We also repair a tremendous amount of incorrect wiring at these sites. (I.E. Neutral wires connected through circuit breakers; green ground wires bonded to a neutral bus instead of a ground bus; floating grounds or no electrical grounds; neutral-to-ground bonding jumper connected three levels down from transformers; incorrectly installed or grounded air terminals/lightning rods.) Our site surveys usually identify most of the NEC code violations, safety infractions as well as non-compliance to military standards. Many times this information can be utilized for self-help corrections by military personnel. (See the USAF letters posted on this site as well as the ATCAL Photo Report.)

In our weather sensor junction boxes are cable bundles with 6 or more unused or disconnected wires. Should these be grounded?
• (MIL-HDBK-419a Volume 2 Section 1.3.3.5.27 Grounding of Unused Wires: All unused wires/pairs of communication cable runs should be connected to ground at each end. This action will reduce transients on the unused lines which otherwise could be coupled to in-service lines of the cable.) Mike's Opinion: This is a very common problem at military weather equipment sites and should be corrected. Many of the junction boxes do not offer a ground connection and a new one must be established to terminate 6-12 wires.

We are told that the earth electrode ground systems are installed according to military standards but we still experience equipment damage during storms. Civil engineering and public works have no affordable solutions. How can we check our ground system?
• (MIL-STD-188-124B Section 5.1.1.1.7 Military Standards Resistance Checks: The resistance measurements of the earth electrode subsystem to earth shall be accomplished every 21 months after the initial 12 month period by the facilities engineering activity.) Mike's Opinion: First of all, I feel that NEC, NFPA and Military Standards are minimum guidelines and should not be considered the conclusive and only installation procedure. If the code says use a number 6 solid grounding conductor but a 2/0 stranded ground conductor is installed, the code has been exceeded for the better. If the standard says utilize approved ground clamps but the cable has been exothermically welded, the code has been exceeded for better and more permanent with less maintenance. If the standard says the ground rod and cable connection should be 12" sub-surface then in our opinion, it must be exothermically welded to prevent corrosion and maintenance. A ground clamp should never be installed below surface unless you plan to dig it up every six months and perform corrosion control maintenance or prevent corrosion with weatherproof coverings before burial. However, 99.9% of the time, once the ground connection is underground, it is never inspected until equipment trouble occurs. For methods to measure ground resistance, refer to the Grounding Survey information posted on this site and/or request additional information.

Someone from DOD HQ said that we are supposed to keep written records of ground system measurements for years, but we've never seen them. Who keeps the records?
• (AF 32-1065 Military Standards Records keeping: Civil engineering should keep a sketch of the grounding system, test points, test date, tester's name, general condition of air terminals, conductors, other components, corrosion protection measures, security of attachments, resistance measurements, variations from requirements, discrepancies noted and corrective action, and date of repairs. Keep these records for a minimum of 6 inspection cycles. For Communication Electronics facilities (every 21 months) that equates to 10.5 years and for general facilities (every 5 years) that equates to 30 years of records. Mike's Opinion: Changes in ground resistance can offer incites ahead of equipment problems. Check your ground systems more often and keep a set of records for your own use. (See the Grounding Survey information posted on this site.)

At our USAF airfield sites, should the ground rods be above ground level or below? Should they be 5/8" or 3/4" rods and how deep?
• (MIL-STD-188-124B Section 5.1.1.1.4 Military Standards: Ground Rods shall be copper-clad steel, a minimum of 10 feet in length, spaced apart not more than twice the rod length (20' apart), and shall not be less than 3/4" in diameter. The thickness of the copper jacket shall not be less than .012 inch.) Mike's Opinion: Sub-surface ground rods that have exothermically welded connections are corrosion maintenance free and being underground, grounds maintenance (lawn mowers) will not destroy the ground connections. Depth of a ground rod beyond 10' is usually based on the ground resistance measurement that is recorded. Soil conditions and other factors will determine resistance measurements that may require deeper driven rods to read the optimum resistance measurement. We have driven 100' rods to attain 10 ohms in Florida where the soil will accept 100' driven rods. Where on Utah mountain tops we cannot drive rods at all and must utilize alternate grounding methods such as conductive concrete, mesh grids/plates, wells, etc.

What's your opinion of a ground rod clamp that's made of aluminum with steel screws and is connected to a copper rod with copper wire? Does dissimilar metals cause corrosion problems?
• (MIL-STD-188-124B Section 5.2.3.1 Military Standards: Corrosion Protection: Each bonded joint shall be protected against corrosion by assuring that the metals to be bonded are galvanically compatible. Bonds shall be sealed with a silicone or petroleum-based sealant to prevent moisture from reaching the bond area.) Mike's Opinion: Yes, I find this type of ground rod clamp all the time on military base installations and many times they have corroded so much that they are disconnected from the rod, especially when the clamp was buried underground. There again, it meets the National Electrical Code that is a minimum standard and unless the military has defined what type of connection is required, it will be the cheapest hardware store variety.

Someone said the ground cable should be welded to the ground rod. Is that something we can do and how? Is that what is meant by exothermic connection?
• (MIL-STD-188-124B Section 5.2.6.3 Military Standards: Bonding of Copper to Steel: Either brazing or exothermic welding shall be used for the permanent bonding of copper conductors to steel.) Mike's Opinion: We use exothermic welding for each ground rod and cable connection. This type of connection is performed by using a mold that is slid down on top of the ground rod several inches which enables the proper gauge ground cable to be inserted into the side hole and meet against the rod. Each mold is designed for certain applications and number of ground cables. (I.E. A mold for 3/4" vertical rod with two cables sized at 2/0.) Molds are available for round pipe and flat steel as well as for vertical and horizontal attachment. Once the cable is against the rod and the mold is clamped securely, metal alloy is added to the mold well and ignited with a striker. The mold is removed and the connection has been made. Be careful, due to the extreme heat and instantly reaching skin evaporation temperatures. Molds and metal alloy along with proper mold clamps and other accessories are available from various suppliers and electrical wholesalers.

Our military ground resistance requirement is 10 ohms but we are unable to achieve 10 ohms driving one ten foot rod. What can we do?
• (MIL-STD-188-124B Section 5.1.1.1.3.1.2 Military Standards Resistance to Earth: (DO) the resistance to earth of the earth electrode subsystem should not exceed 10 ohms at fixed permanent facilities. Resistance to earth for tactical and transportable systems should not exceed the TO established for the particular system.) Additional Considerations: Where a 10 ohm ground resistance measurement is not obtained at fixed permanent facility or the required resistance established for tactical or transportable systems is over 10 ohms due to high soil resistivity, rock formations, or other terrain features, alternate methods for reducing the resistance to earth shall be considered. See MIL-HDBK-419 Footnote: MIL-HDBK-419 Section 2.2.2.2: Department of Defense Communications Electronics Requirements - The NEC 25 ohm resistance is not acceptable for C-E facilities when consideration is given to the large investments in personnel and equipment. A compromise of cost versus protection against lightning, power faults, or EMP has led to establishment of a design goal of 10 ohms for the earth electrode subsystem (EES) in Mil-STD-188-124b. The EES designed in MIL-STD-188-124b specifies a ring ground around the periphery of the facility to be protected. With proper design and installation of the EES, the design goal of 10 ohms should be attained at reasonable cost. At locations where 10 ohms has not been attained due to high soil resistivity, rock formations, or other terrain features, alternate methods listed in Paragraph 2.9 shall be considered for reducing the resistance to earth. Footnote: MIL-HDBK-419 Section 2.2.3 Experience has shown that a grounding resistance of 10 ohms gives a fairly reliable lightning protection to buildings, transformers, transmission lines, towers and other exposed structures. The lower the resistance, the greater the protection, therefore, attempts should be made to reduce the resistance to the lowest practical value. Footnote: MIL-HDBK-419 Section 2.6.2 and 2.6.2.1 Most of the resistance of a single electrode (ground rod) is obtained within a reasonable distance from the electrode. For a vertical rod, better than 90 percent is realized within two rod lengths. If two or more electrodes are closely spaced, however, the total effective resistance of neither is realized. This interaction prevents the resistance of N electrodes connected in parallel from being 1/N times the resistance of one of the electrodes. For this reason, the crowding of multiple vertical rods is not as beneficial in terms of dollar cost per ohm as is achievable with fewer rods properly spaced. If the electrodes in a multiple electrode installation are separated by adequate distances, the interactive influence is minimized. The separation between driven vertical ground rods in a group of rods should not be less than the length or greater than twice the length of an individual rod. Consider two rods driven into the earth with their tops flush with the surface. The two rods are electrically parallel, but the presence of one rod affects the resistance of the other. Also see MIL-HDBK-19 Figure 6: Combined Rod Resistance that offers a formula that can be utilized to calculate ground resistance when installing multiple ground rods.

Are the down conductors of a lightning rod supposed to be bonded to the top of the tower or bottom?
• (MIL-STD-188-124B Section 5.1.1.3.8.4 Military Standards: Down Conductors shall be bonded to the tower legs at the base. Conductors connecting to the earth electrode subsystem shall be protected against mechanical damage. Connecting cables passing through foundations shall be installed in plastic or non-metallic conduit. Section 5.1.1.3.3 Down Conductors - 8" radius and bends NOT GREATER THAN 90 DEGREES. Where practicable, a separation of at least 6 feet shall be maintained between open conductors of power and communications systems and lightning down conductors. Down conductors shall be continuous and shall be bonded in accordance with 5.1.1.1.5 and 5.2.3 to an earth electrode subsystem or to a ground rod bonded to this subsystem installed as near as practicable and within 6 feet from the structure.

We have green ground wires connected to the neutral bus bar in the power panel. Is that correct?
• (MIL-STD-188-124B Section 5.1.2.2.3 Military Standards: AC Power Neutral: In all electrical and electronic equipment, the AC power neutral (white wire) shall be insulated from the equipment chassis, case, and facility ground system except for one point at the facility power service entry.) And (NEC Article 250-24(a)(5) Load-Side Ground Connections: A grounding connection shall not be made to any grounded circuit conductor on the load side of the service disconnecting means.) Mike's Opinion: This can be correct if the power panel is the service disconnect (first panel past a transformer). The service disconnect is where the bonding jumper is connected between the neutral bus and the enclosure. This is a common violation that could have disastrous consequences. By bonding the neutral and equipment together down stream from the service disconnect the usually silent equipment grounding system becomes a current carrying system. Of course the equipment grounding system includes all the appliance and equipment enclosures as well as the conduit. An unfortunate electrician could receive a fatal shock as he dismantles a conduit or a refrigeration mechanic could receive a shock when he takes apart an ac unit.

Additional information and site survey information can be obtained by contacting

POC: Mike Helms mike@lightningmike.com