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February 2001: Lightning

A typical summer thunderstorm is predicted for later in the day. You dread the incoming weather change because you were hoping for a nice dry weekend. This rain will ruin your weekend. This thunderstorm is pretty spectacular, with many flashes and claps of thunder. An hour after the storm passes your plant begins having problems. The telephone system is dead. The computer system is "down." The new computer controlled process equipment is also down. Your fire alarm system reports "system trouble." The plant engineer reports that the energy management system has failed. What is the cause of this "facility breakdown?"

The lightning storm induced electrical currents, which damaged your computer and all computerized equipment. The current entered the building through various electrical conductors. The current is capable of moving so swiftly that it can penetrate many barriers designed to stop it (fuses, circuit breakers, etc.) from damaging or destroying sensitive electronic computer chips. Of 4,000 lightning strikes measured, 50% equaled or exceeded 14,000 amps. Barriers such as fuses or circuit breakers can not operate fast enough to stop this swift moving, high intensity electrical charge. Over the course of time, additional problems may be discovered that initially did not fail. The results will be downtime and severe aggravation.

Each year, lightning kills approximately 200 Americans and injures another 1,500. Unlike other types of property losses, lightning comes prior to the warning thunder. Lightning is fast becoming a serious problem as the world changes from the industrial age to the technology age. These technological advances place a high level of performance on computers and computer chip equipment.

Lightning is a sudden flash of light caused by the discharge of atmospheric electricity between clouds or between a cloud and earth. It occurs when a region of the atmosphere acquires an electrical charge sufficient to overcome the resistance of the air. Lightning can occur between clouds, within a cloud, or from cloud to ground. Almost all lightning flashes either remain in the cloud or strike the ground. Cloud to cloud lightning discharges are rare.

Managing the risk associated with lightning requires thought and effort. A good starting point is a review of NFPA 780 "Standard for the Installation of Lightning Protection Systems." This code covers lightning protection requirements for ordinary structures, miscellaneous structures and special occupancies, heavy duty stacks, watercraft, and structures containing flammable vapors. The risk assessment guide in Appendix H of this code will help in risk analyses.

The building can be protected by providing lightning rods connected by heavy cables into the ground. These rods will intercept the lightning strike and route the charge into the ground eliminating or greatly reducing potential damages. All parts of the building need to be protected. Electronic computers and equipment also needs to be protected. Computer chips in computers, communications systems, processing equipment, etc. all are easily damaged by lightning strikes and the electrical surges which follow. Installing surge arrestors will help prevent this or minimize damage.

If your are unsure of the level of protection for your operations, do not hesitate to contact us.