The NTS conducts lightning testing at a number of our laboratories across the country. The newest member of the NTS family, Lightning Technologies, is one of the world's most complete simulated-lightning test laboratories.
The electrical characteristics of the different types of lightning flashes, and the resulting surges and fields from a strike, are complex. Engineers have found that to study the effects of lightning upon a structure or system, it is most efficient to isolate the components of the lightning waveforms and electrical/magnetic fields and to evaluate their effects through individual simulations. NTS labs includes specialized and unique equipment to simulate all the electrical characteristics of natural lightning as well as the transients it induces in electrical and electronic systems.
The direct effects of lightning include the physical damage due to the attachment of the very hot (20,000°C) and high-current (250,000+ amperes) lightning channel. These effects include the burning and shattering of materials and the direct conduction of lightning voltages into electrical and electronic circuits resulting in burnouts of equipment. Two basic types of generators are used for direct-effects testing: High-voltage, Marx-type impulse generators produce voltages and electric fields up to 1.5 million volts to simulate lightning leader attachment and surges induced on power transmission lines. The high-current generators produce up to 250,000 amperes and include three units adapted to duplicate the lightning stroke, and intermediate and continuing current waveforms of a typical lightning strike. To accommodate very large test specimens, direct-effects tests are performed in facilities like Lightning Technologies' indoor high-bay laboratory that measures 40 x 120 feet.
The indirect effects of lightning are caused primarily by earth-voltage rises that occur when the flash dumps charge into the earth and by the intense electromagnetic field associated with the flash. These fields and earth-voltage rises have enough energy to cause component damage up to a kilometer or more from the actual strike. Indirect effects are most commonly induced into system interconnecting cables and may damage or upset electronic components. The staff of LTI and NTS have been at the forefront of indirect-effects test method development for many years. These methods are defined in IEEE, ANSI, SAE, EUROCAE, U.S. MIL-STDS and many industry and company standards and specifications. The indirect-effects testing lab includes many specialized devices for complete field and transient analysis, from the level of individual circuits to completely operational interconnected systems. Typical indirect effects tests include pin injection, transformer injection, capacitive injection, ground-circuit injection and field immersion techniques.
The flickering seen in a lightning strike to ground actually is caused by a series of current strokes, the electrical characteristics of which are called multiple stroke. On the other hand, inter- and intracloud lightning has very different electrical characteristics, referred to as multiple burst. International lightning-test requirements define the waveforms of both multiple stroke and multiple burst, and require that aerospace electronic systems that perform critical or essential functions be tested against the effects of both types of lightning. We have the most versatile facility for both multiple-stroke and multiple-burst testing.
We regularly perform a wide variety of indirect-effects verification testing at customers' facilities around the world.
We perform many types of static electricity tests. These procedures simulate the range of static effects: from those occurring on aircraft that can exceed 100,000 volts to the small, but potentially hazardous voltages, produced by manufacturing and material handling operations.