RU2071623C1 - Lighting protection device for buried cables - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: lightning protection circuit has rectangular frame made of metal wire and is closed to electric condenser; it is buried in low-conductivity soil and functions as receiving antenna. Specific properties of circuit appear in electromagnetic field built up due to thunderstorm and are used to convey lighting channel to circuit plane. EFFECT: improved lightning protection of buried cables.

Description

 The invention relates to the field of electrical engineering, in particular to devices for protection against atmospheric electricity, for example, cables laid in the ground.

 Information streams (individual messages) can be transmitted via communication lines with high reliability. The absence of temporary pauses on any line is an indispensable condition for delivery to the recipient of the voice original, telegram or email without distortion.

 The work of communications ceases when a natural phenomenon occurs during lightning discharges into the ground. Atmospheric electricity, huge current and voltage in the lightning trunk burns an underground cable, damages communication equipment.

Intercity cable lines, as the most responsible for the number of channels, are protected by lightning strikes by devices (1):
extra strong type of cable with increased conductivity of the protective coating,
metal tires laid in the ground, wires or cables,
grounding connected to the metal cover of the cable,
an air line built over a cable equipped with spark gaps.

 The listed means of protection have the general property of reducing the magnitude of the electromagnetic wave of atmospheric electricity that directly affects the cable circuit during thunderstorms.

 Known protective cables, wires or tires, selected as a prototype, which are metal conductors laid at half the depth of the cable and parallel to it.

 To increase the degree of protection of underground structures, one, two or three wires are laid over them.

 The disadvantages of the known device are that the wire, located in the ground on the path of lightning currents going to the cable, practically does not perform the functions of protecting the cable from direct lightning strikes into the cable; the small screening effect of metal wires in the electromagnetic field of atmospheric electricity does not save the cable line from being struck by a lightning voltage wave; in low conductive soils (ρ ≥ 500 Ohm), the conductivity of metal cables sharply decreases, and cable damage, on the contrary, increases.

 The objective of the invention is to increase the reliability of protection of underground cable lines from thunderstorms.

 This problem is solved in such a way that a grounded metal cable is located along the cable, laid on the ground surface in the form of an open rectangular loop, part of the corners of which are raised above the surface with the formation of points, and a capacitor, which is a receiving antenna, is included in the cut of the loop.

 Comparative analysis with the prototype allows us to conclude that the inventive device is characterized by the presence of new elements: an electric capacitor of constant capacity, a metal tip for spontaneous draining of electric charges in a plane vertical relative to the earth's surface.

 Thus, the claimed device meets the criteria of the invention of "novelty."

 A cable located on the surface of the earth, its gap (cut), an electric capacitor included in the gap, and a loop-shaped form of cable placement lead to increased reliability of lightning protection of cables. This allows us to conclude that the technical solution meets the criterion of "significant differences".

 The invention is illustrated in the drawing, which shows an example implementation of the device.

 A device for protecting underground cables from thunderstorms includes a metal cable 1 and an electric high-voltage pulse capacitor 2 connected in series. The angle 3 of the cable is raised to the top of the tree with the equipment of a metal tip 4. The cable is grounded to a concentrated ground 5.

 The cable is placed on a rocky surface so that the two sides of the loop-frame are laid parallel to cable 6, the length and width of which is much greater than the distance to the underground cable, because the condition is satisfied: "a", "c"> l.

 Due to the fact that the cable is located on the surface, angles and tips rise above the terrain, the electric charges of a thundercloud accumulate on the metal of the device, the lightning discharge into the cable is accelerated, and then its current flows to the point of earth remote from the cable where the ground electrode is arranged. Interception and sewerage of lightning current increases the reliability of the cable during direct impacts of atmospheric electricity into the ground.

 In the zone of the induction effect of the lightning current, the distributed cable inductance and the capacitor electric capacitance form an electric antenna, the directional properties of which are the electromagnetic shield of the cable being protected. In this case, the action of the device increases the reliability of the underground communication cable, in contrast to the prototype, since the opposite direction of the electric vectors of inductive and capacitive resistances leads to a decrease in the total resistance of the antenna, an increase in the conductivity of the cable, and as a result the screening effect of the device increases.

Claims (1)

 A device for protecting underground cables from thunderstorms, containing a grounded metal cable located along the cable, characterized in that the metal cable is laid on the ground surface in the form of an open rectangular loop, part of the corners of which are raised above the ground surface with the formation of points, and in the cut of the loop, being a receiving antenna, a capacitor is turned on.