Sky voltage
Encyclopedia
Sky voltage refers to an electrostatic voltage gradient that is present in the free air of the atmosphere, and which can have a different voltage potential relative to the surface of the planet. The gradient varies with atmospheric humidity, dropping lower on days with high humidity, and higher in very dry air. The voltage potential averages about 120 volts per meter.
Tall insulated metallic objects can absorb these voltage gradients out of the atmosphere, and conduct the voltage to a terrestrial collection and measurement station.
Small lightweight electrostatic motors and toys can be driven from this collected sky voltage when one side is connected to earth ground, and the other is connected to the sky collector, such as a kite or balloon with a foil collector and fine wire running down to the ground. A collector 200-300 ft high can develop a sky to ground potential as high as 20,000 volts.
ing from electrical devices to nearby earth grounded metal, or sparking to the people touching the electrical devices. Due to having wires spanning tens and hundreds of miles, the wire has the capacitive potential to store large charge quantities across the system that could prove lethal to energy customers. Lightning striking near an electrical power device also had the potential to leak dangerous high voltages into the system that could spread throughout the system in moments.
In order to safely dissipate this collected sky voltage, one current-carrying wire of the electrical grid is connected to a grounding rod at regular intervals throughout the power system. This serves to discharge and bleed off any large voltage charges being collected from the suspended wires. This wire is called the neutral, since its voltage is zero relative to the earth ground.
Modern three-phase
transmission lines also include a fourth suspended grounding wire which carries no load, but helps to absorb the sky voltage and prevent electrostatic buildup in the other poly-phase current-transporting wires.
Tall insulated metallic objects can absorb these voltage gradients out of the atmosphere, and conduct the voltage to a terrestrial collection and measurement station.
Small lightweight electrostatic motors and toys can be driven from this collected sky voltage when one side is connected to earth ground, and the other is connected to the sky collector, such as a kite or balloon with a foil collector and fine wire running down to the ground. A collector 200-300 ft high can develop a sky to ground potential as high as 20,000 volts.
Sky voltage and the electrical neutral wire
Sky voltage was a problem for early electrical power and communications grids which used suspended insulated bare wire to transport current. These suspended wires also acted as sky voltage collectors, and could result in dangerous electric sparkElectric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...
ing from electrical devices to nearby earth grounded metal, or sparking to the people touching the electrical devices. Due to having wires spanning tens and hundreds of miles, the wire has the capacitive potential to store large charge quantities across the system that could prove lethal to energy customers. Lightning striking near an electrical power device also had the potential to leak dangerous high voltages into the system that could spread throughout the system in moments.
In order to safely dissipate this collected sky voltage, one current-carrying wire of the electrical grid is connected to a grounding rod at regular intervals throughout the power system. This serves to discharge and bleed off any large voltage charges being collected from the suspended wires. This wire is called the neutral, since its voltage is zero relative to the earth ground.
Modern three-phase
Three-phase
In electrical engineering, three-phase electric power systems have at least three conductors carrying voltage waveforms that are radians offset in time...
transmission lines also include a fourth suspended grounding wire which carries no load, but helps to absorb the sky voltage and prevent electrostatic buildup in the other poly-phase current-transporting wires.
See also
- Electrostatic motorElectrostatic motorAn electrostatic motor or capacitor motor is a type of electric motor based on the attraction and repulsion of electric charge.Often, electrostatic motors are the dual of conventional coil-based motors. They typically require a high voltage power supply, although very small motors employ lower...
- Leyden jarLeyden jarA Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a jar. It was invented independently by German cleric Ewald Georg von Kleist on 11 October 1745 and by Dutch scientist Pieter van Musschenbroek of Leiden in 1745–1746. The...
- Oleg D. JefimenkoOleg D. JefimenkoOleg Dmitrovich Jefimenko - physicist and Professor Emeritus at West Virginia University.-Biography:...
- Static electricityStatic electricityStatic electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...