Lightning bolts occur when the voltage differential between two locations in the atmosphere or the earth’s surface reaches a critical level. Then, with astonishing speed, an ionized, conductive path is established and there is a flow of electrical current that is often powerful. A direct strike on a partially grounded object such as a building can cause immense destruction and injury or loss of life.
Lightning is actually a plasma. Although resembling a gas, it is significantly different and, in fact, may be viewed as a hybrid form of matter and energy.
Plasmas are the most abundant form of matter in the universe, comprising over 99% of what is visible. Plasma is created either in nature or intentionally by humans when a gas is subjected to some form of energy, thermal, electrical, magnetic, or consisting of electromagnetic radiation as in a laser beam. Abruptly, the gas changes to a plasma and assumes different qualities. A gas has low electrical conductivity, whereas once transformed to a plasma, the conductivity is higher by many orders of magnitude.
Gases of a given type exhibit fairly simple and uniform properties whereas plasmas are all over the spectra. That is because they are far more reactive to electromagnetic and other influences. Their electrons, ions, protons and neutrons vary in polarity and value of charge, in combination they tend to behave differently in the face of changing circumstances, often exhibiting diverse wave mechanics and abrupt instabilities.
Plasma particles, being charged, interact at greater distances than gases. So there is more tendency for plasma particles to exhibit quasi-organized motion, often in waves.
Terrestrial plasma is not uncommon. In the home and office, fluorescent lighting involves the intentional ionization of an otherwise inert gas, which then becomes conductive and emits ultraviolet radiation, subsequently converted to visible light when it strikes the fluorescent coating on the inner surface of the glass envelope. Another example is neon tube lighting. Also, arc welders and plasma cutters generate plasma and depend upon it for effective operation.
When plasma takes the form of lightning, electrical charge differentiation is caused by large vertical (hence dark) cloud formations. The high voltage drop across nonconductive atmospheric air results in abrupt ionization, whereupon a conductive path is established and the lightning bolt ensues.
A lightning discharge near a utility line will induce unwanted current and a voltage spike throughout connected premises wiring. The result can affect electrical equipment, ranging from invisible damage of a single integrated circuit to explosive and total destruction of the entire unit. Proper design and installation of the electrical system greatly reduces these hazards.
The first and most effective counter-measure for lightning is adequate grounding. The National Electrical Code specifies sizing and installation details for numerous grounding electrodes ranging from simple ground rods to more elaborate ground rings and plate electrodes.
Enhanced grounding may be necessary if the location is severe (such as a mountaintop) or where there is extensive bedrock, or where the soil has high resistivity (such as well-drained gravel), or in a building containing a lot of expensive electronic equipment such as a telephone central office. Code mandates may be exceeded, and even an existing installation can be expanded by adding more grounding electrodes. Grounding electrode types may be mixed. For example, ground rods can be appended to a ground ring.
Underground water pipe makes an excellent ground electrode. But beware of the fact that in the past plastic pipe may have been spliced in to make a repair, interrupting ground continuity.
The ground electrode conductor (typically a bare stranded copper wire run from the meter socket to the ground rod) should be straight as possible, without sharp bends. A lightning surge, with its extremely high rise time, resembles of high-frequency waveform. A sharp bend in the ground rod conductor equates to a part-turn in a wire coil. With high inductive reactance, the wave front is likely to seek a lower-impedance path to ground, leaving the confines of the copper and arcing through the air, unfortunate if there is flammable material nearby.
A different type of protection, which should be used in conjunction with good grounding, is the surge suppressor. One type is waterproof and mounts on the outside of a meter socket enclosure. The wires are color-coded and they are connected according to the manufacturer’s instructions. For this operation the utility must shut off the power at the transformer because two of the surge suppressor leads must connect to the meter socket supply lugs. The utility likes to have this done because its costly meter is being protected.
Another type of surge protection is integrated into the familiar plug-in strip that is used for computers and peripherals. This type of surge protector neutralizes lower level spikes but would be destroyed in a higher voltage event. Actually, it is considered beneficial to provide a range of two or more unequally rated surge suppressors. This is known as a cascaded configuration.
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