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Although it is not advisable to mix water with electricity, we can understand electrical current flow if we compare its behavior to that of water. There are many similar behaviors to observe.
The movement of electrically charged particles (plus or minus) characterizes an electrical current. The charged particles are either electrons (charged minus) or ions (charged either plus or minus).
In a metallic bond, atoms do not share or exchange electrons to bond together. Instead, many electrons (roughly one for each atom) are more or less free to move throughout the metal, so that each electron can interact with many of the fixed atoms.
Metallic conduction describes the flows of electricity that are widely controlled within a facility. It is characterized by electrons moving through a metal conductor with no obvious chemical changes or movement of atoms in the metal. Where there are sufficient conductors to support current flow, there should be no signs of stress or breakdown in them.
A simple, but detailed description of how current flows is given by Sol Medoff and John C. Powers in their book The Student Chemist Explores Atoms and Molecules*:
"The last type of bond in our discussion is the "metal" bond. Metals always have one or more empty orbitals. This means that the valence electrons can jump. They can jump all over the place. Atoms of metals are arranged next to each other. The jumping electrons visit other atoms. In fact, they can no longer be identified with the original atom they came from. They go very fast, through the entire metal system of atoms. The atoms, minus their moving electrons, become charged plus. The metal bond now becomes plain. The sea of moving electrons are, at the same time, held by attraction to the plus atoms. Thus, they are like billions of cords held tightly to the package. The metal bond is a powerful one.
"The moving electrons give the metal some of its characteristics. The electrons move in waves that capture light waves. All of the light waves (or almost all) are then radiated back. The metal assumes a high luster. If one end of the metal is heated, the electrons move even faster. The entire metal object is affected, and the whole thing becomes "hot."
"In the case of electricity, an additional load of electrons are fed into the metal. The additionals are past the neutral point. No more electrons are needed by the metal. Either the new electrons move through empty orbitals, or they push other electrons down the metal by repulsion. In any case, the metal bond causes the metal to allow a flow of electricity."
Another form of conduction is ionic or electrolytic conduction, characterized by a motion of ions through a liquid. This process is associated with electrical generators and storage batteries. A battery uses the energy from an oxidation-reduction reaction to produce an electric current flow. An electrochemical battery or galvanic cell is a device powered by an oxidation-reduction reaction where the oxidizing agent is separated from the reducing agent so that the electrons must travel through a wire from the reducing agent to the oxidizing agent.
LEO says GER is a way to remember how the process of oxidation and reduction works: a loss of electrons results in oxidation, and a gain of electrons results in reduction. This relates to corrosion, current flow, and the construction of effective ISBPs.
Geomagnetism induces some current flow that creates differences in voltage (also called "potential") between specific points on the Earth. This current flow is the safest known to occupants because it occurs outside the facility and underground.
The GES shares this current with the facility on a real-time basis (at speeds of 0.6c to 1c) via the GEC, which ends at the ESE and bonds to the main bonding jumper. This jumper transfers the current to the grounding wires and isolated neutral at the supply side of the ESE. The isolated neutral and grounding wires carry this current further into the facility from the load side of the ESE.
When equipment grounding conductors and the main bonding jumper are connected to the ESE enclosure, the whole enclosure becomes a conductor with a lot of surface, or cross-sectional, area for handling current flow across it.
Any sub-panels are located downstream from the ESE, and their function is to further divide circuits for distribution indoors. The current from the ground is passed along downstream through the electrical conduit system and all sub-panels to junction boxes and to device boxes such as power outlets, lighting fixtures, and switches. Ground current will pool evenly across all these points. This balanced current is an indicator of current electrical copies.
Electrical transmission and distribution begins at a power plant which first produces electricity. The plant then sends the electrical power over a grid of wires that ends at consuming facilities. In the United States, electrical power is commonly transmitted at frequencies of 50 or 60 hertz as alternating current, or AC. This AC is transmitted in one direction only down isolated wires that permit stacking of additional current on the grid.
Electrical power distribution at 50 Hz requires 20 ms of time to form its wavelength of 5,995,849.16 m, and electrical power distribution at 60 Hz requires 16.666666666666667 ms of time to form its wavelength of 4,996,540.966666667 m. Strict (0.033 %) tolerance limits of 59.98 Hz and 60.02 Hz for electrical power distribution at 60 Hz keep wave formation time to within 16.6611129623458847051 ms and 16.6722240746915638546 ms. In practice, the wave is so much more accurate that the electrical power distribution system can be synchronized by advancing or retarding the grid frequency. This process is related to time base oscillation and to mechanical oscillation.Alternating current (AC) is sometimes characterized as traveling in "two directions" or "forward and reverse" as it proceeds along individual supply and return wires. In fact, it is transmitted across one supply conductor only in a single direction. Once consumed, the electricity continues the single direction path across a neutral / return conductor. The entire path resembles a circular loop, but the direction of travel is still one-way, and ultimately "round trip."
Current that returns to a power utility from consumer facilities will parallel neutral return conductor pathways. Neutral and return wires are commonly grounded at overhead utility poles, as well as in underground configurations, so returning current commonly flows in a parallel fashion along return wires and through the ground back to a utility. As a consequence, redundant grounding points along the neutral return conductor path across electrical distribution systems enhances safety by directing lightning strikes to the earth at the nearest available point, by reducing the amount of insulation required for high-voltage transmission lines, and by blowing local fuses and opening breakers more quickly when breakdowns and faults occur in transformer windings and in facility circuits. Beyond these benefits, there are much more: the power utility grounding points along the entire electrical distribution system create a reliable and robust means to handle overcurrents and potential differences by supporting a broad range of wavelengths, short and long. The increased efficiency in grounding electrical energy prolongs the life of individual components along the power grid and reduces overall times of exposure to active electrical events, maintenance, and repair.
By contrast, current flow inside facilities that consume electrical services does not reach grounded neutral conductors downstream from the ESE. Instead, the return current leaves the ESE and either moves upstream to find those grounding points provided by the power utility along the electrical distribution system, or it flows all the way back to the power utility across the same electrical distribution system wiring, or it flows across a main bonding jumper and local grounding electrode conductor to the grounding electrode system at the locally served facility. In normal practice, returning current flow takes all three paths.
The isolated neutral is used as a safety feature to keep return current away from occupants inside a facility in order to prevent electrical shock and fire. The isolated neutral also promotes the integrity of a facility grounding cone of protection by keeping away normal return currents that can prematurely weaken the grounding system with prolonged exposure.
SummaryElectrons are charged minus and repel each other, causing a pooling of electrons at all available plus environments.
Electrical current jumping across two points having different voltages is flashover.
Metallic conduction is typically associated with our control of current flow in a facility, and works well when there are plenty of conductors to handle the current.
Balanced and ample current flow figures prominently in a strong grounding cone of protection and up-to-date electrical copies. The practice of grounding multiple points along the path of neutral return conductors by power utilities creates a safer electrical distribution system by efficiently moving some of the returning current flow to below ground across a broad range of wavelengths. Within facilities, the isolated neutral is employed as a safety feature and helps to maintain a strong grounding cone of protection.
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