The following information is the intellectual property of Dr. Ronald B. Standler, and all information was gathered from the following link: http://www.rbs2.com/blitz.htm

Lightning Strike

Lightning is the transient passage of electrical current between a cloud and either the surface of the earth, another cloud, or an object in or near a cloud.
Lightning is most commonly associated with thunderstorms, but can also occur in snow storms and from the ash cloud of volcanic eruptions. Thunderstorms can be an isolated cloud, or part of a line of thunderclouds associated with a front on a map of surface air pressure. Lightning is most common in the spring and summer months, but can occur at any time.

Damage caused by lightning

Lightning causes damage to buildings and equipment in three different ways.

1. There can be damage as a result of a direct lightning strike. Such damage includes damage to roofing materials, structures such as chimneys, heating or air conditioning units located on the roof or exterior of a building, or fires caused by lightning igniting combustible material, such as wood-frame buildings or flammable liquids or vapors.

2. Part of the lightning current can be carried inside a building by electric power, telephone, analog or digital data lines (e.g., closed circuit television cameras, sensors in an industrial plant, etc.). This direct injection of lightning current inside a building can cause immense damage to electrical circuits and equipment.

3. The electromagnetic fields from the current in a lightning stroke can induce current and voltage in wire and cables inside a building. Such surge currents are typically less intense than direct injection of current, but can easily vaporize integrated circuits in computers, modems, electronic control circuits, etc.

Electronic equipment is typically designed to operate in a well-controlled electrical environment. It is the responsibility of the user to install lightning protection, electrical surge-protective devices, and power conditioning equipment to mitigate the effects of disturbances in the electrical voltage waveform. It is well recognized that the trend toward integrated circuits with more transistors per unit area, and faster switching speeds, makes these circuits more vulnerable to both upset and damage.

Upset is a temporary malfunction without any physical change in the devices or equipment. For example, one might recover from upset by rebooting a computer; the only loss would be data that was not written to disk before the upset occurred, and consequential damages from the interruption of continuous operations. The consequential damages can be large, for example, in medical equipment used in life-support applications.

Damage is a permanent alteration in the physical properties of one or more components, that requires repair or replacement before the equipment can resume normal operation. Examples of lightning damage to electrical equipment include flashover of insulation inside motors or transformers, so that the equipment is no longer functional. Examples of lightning damage to electronic equipment includes vaporized traces on printed circuit boards, vaporized transistors and integrated circuits, blown fuses, etc.

Recovery from damage usually takes much longer than recovery from upset. Prompt recovery from damage requires advance planning, including local stock of spare parts or redundant systems. Aside from stocking parts, one must also plan to have an adequate number of technicians who can diagnose and repair equipment. The lack of trained repair personnel is generally a bigger bottleneck than the lack of replacement parts.

A company also incurs expenses for consequential damages such as overtime pay to do the backlog of work while the damaged equipment was awaiting repair or replacement.

Aside from surge currents that are conducted on wires or cables, there can also be damage from magnetic fields associated with lightning currents. For example, lightning current that travels to earth along reinforcing steel inside a concrete wall or column can produce a rapidly changing magnetic field that can erase floppy disks or computer tapes inside a storage cabinet. Further, this rapidly changing magnetic field can induce a surge current in loops of wire or cable that are common in computer systems, and such surge currents can cause damage or upset in the same way as direct injection of lightning current into wires and cables.

It is well known even to laymen that lightning tends to strike elevated objects, such as tall trees, tall buildings, water towers, transmitting antennae for radio or television stations, overhead power lines, etc. As a result of this knowledge, many people have the misconception that burying a cable somehow protects it from lightning. The truth is that when lightning current reaches the surface of the earth, the current does not magically disappear, but prefers to travel through highly conducting metal pipes (e.g., buried gas and water pipes, etc.) and buried cables (e.g., electric power, telephone lines, cable television, etc.) instead of dry soil or dry rock. In this way, buried pipes and cables can act like an attractor for lightning current, in the same way as a tall tower or building.

Lightning current can travel for long distances on overhead power lines, or in underground pipes and cables, so that a user who experiences upset or damage may not recognize that it coincided with a lightning strike some distance from the user.

Warning of lightning

Courts in the USA are no longer tolerant of blaming lightning damage as an "Act of God", as the technology for avoiding such damage is well known and businesses are expected to use proven technology to avoid injury to their customers. Furthermore, customers may reasonably demand continuous service, even during local thunderstorms. Saying "the computer is down" is a flimsy excuse that indicates incompetent use of technology and should be a signal for sophisticated customers to take their business to a more reliable provider.

Lightning is no longer blamed as an act of GOD.

It is an unnatural phenomena same as hail storm that should be a recoverable loss.

Protection from lightning

Lightning protection and surge-protective devices can be divided into three general classes.

1. There are air terminals (commonly called lightning rods) on the roof, which are connected to earth through down conductors.

2. There are high-energy surge-protective devices, called arresters, installed on every electrical and electronic conductor that enters the building, so that surge currents are diverted to earth.

3. There are low-energy surge-protective devices, called suppressors, installed at each piece of equipment that is either vulnerable to damage or susceptible to upset.

Traditionally,

1. a chimney sweep, roofer, or lightning-protection company installs air terminals,

2. a licensed electrician installs a surge arrester at the main circuit breaker panel, and

3. the user installs surge suppressors at every piece of electronic equipment inside a building.

This kind of patchwork installation often provides incomplete protection, as there are interactions between these three classes of protective devices. For example, in some installations the surge suppressor has a lower voltage protection level than the surge arrester, thereby drawing surge currents inside a building and creating new problems. Drawing surge currents inside buildings can create transient magnetic fields inside the building that can induce surge currents in other loops of wire or cable, and the surge suppressor may explode when it absorbs a high-energy surge. As another example, lightning current can travel from a down conductor, punch through a wall, and enter the electrical power wiring inside a building.

Also, some installers of air terminals, down conductors, and ground rods do an in effective job, which results in a waste of money for such "protection".

Standard methods for determining lightning protection begin with an estimate of the number of lightning strikes per square kilometer per year at the user's site. While this frequency data can be useful in evaluating the economics of lightning protection, the user must remember that lightning can, and does, cause immense damage even in regions where lightning is not common. Therefore, I generally ignore the probability of a lightning strike to the user's building, since it is foreseeable that lightning will strike near the building sometime in the next few years. Instead, I focus on the loss that will be caused by lightning:

• consequential damages:

  • loss of business income while equipment is inoperative

  • cost of restoring data from backups and paper records

  • injuries caused by upset or damage to electronic equipment, e.g., failure of monitoring equipment in hospital intensive-care ward

• cost of replacing or repairing damaged equipment

• cost of replacing damaged power and data cables

• cost of replacing damaged structure - particularly significant if:

  • structure contains flammable or explosive materials, so lightning could cause catastrophic loss

  • building has a wood-frame and is located far from the nearest fire brigade (e.g., a farm house)

  • building has historic value and can not be replaced