MXPA99004081A - Lightning retardant cable - Google Patents

Abstract

There is provided a cable which retards lightning. The cable includes at least one internal conductor which may be a power conductor or a signal conductor. A choke conductor is wound about the internal conductor in the shape of a spiral. If lightning strikes near the cable or a device which is attached to the cable, such as an antenna, the chock conductor presents a high impedance to the current caused by lightning and will prevent the lightning current from flowing down the choke conductor, thus entering the internal conductor, thereby preventing damage to the internal conductor and any associated electronic equipment. Preferably, a shield is also spiraled wound about the internal conductor adjacent to the choke conductor in a direction opposite to the choke conductor, whereby the angle formed by the crossing of the choke conductor and the shield is approximately 90°to block the magnetic field component of the lightning discharge.

Description

RAY REMOTE CABLE BACKGROUND OF THE INVENTION This invention relates to an electrical cable. More particularly, it relates to an electrical cable that retards the rays so that the cable is not substantially affected by the beam and, in the case of the communication cable, the communication signal on a signal conductor within the cable is not substantially affected, as well as its associated equipment. While the invention is applicable to the power cable and the communication cable, much of the discussion discussed here will focus on the communication cable used in conjunction with an antenna. As used herein, the term "antenna" includes radio and television antenna, satellite dish antennas and other devices that receive electromagnetic signals. A major problem associated with an antenna is caused by the beam that hits the antenna. Often the high current associated with the beam will travel through the communication cable that is connected between the antenna and the electronic equipment. This current will damage the electronic equipment. According to The Liqhtninq Book, by Peter E. Viemeister, auto-induction in a driver can occur during a lightning strike. This occurs because lightning currents can be raised to a scale of approximately 15,000 amperes in one millionth of a second. For a straight conductor with the usual cross section, this transient overcurrent can produce approximately 6000 volts per 0.304 m of cable, which is sufficient to jump an insulated space towards a nearby conductor, such as the center conductor, in a coaxial cable. Currently the lightning protection cable is more focused on the installation on a cable within the system. The National Electrical Code tries to ensure an adequate trajectory for the lightning to discharge, thus reducing the damage to the equipment connected to the end of the cable. The cable in and of itself offers little or no protection from electric fields or magnetic fields associated with the impact of lightning. Although the electrical codes provide suggestions on equipment installation and grounding, its primary focus is to provide a straight path to the ground for the beam to discharge and eliminate the potential differences between the two parts. Figure 1 is an example of a domestic TV antenna installation in accordance with the National Electrical Code. If the beam were to hit the antenna 10, half of the load would be on a ground wire 12 that is attached to the mast 14 of the antenna, and the other half would be on the external shield of the coaxial cable 16 that is connected to the Antenna terminals 18. Theoretically, the current in the coaxial cable 16 would travel to the unloading unit of the antenna 20 and then through the grounding conductor 22. The center conductor or the signal conductor of the coaxial cable, It is not protected, which means that damage to the electronic components in the receiver and other components inside the house is likely. In addition, the larger the cable size, the greater the problem. Since the lightning strikes this antenna 10 and discharges to ground, a large electric field is established along the coaxial conductor 16 and the grounding cable 12. At right angles to this electric field there is an exceptionally strong magnetic field that it surrounds the entire cable. In addition, the beam follows the most direct, closest and best path to earth. Any bends, twists or turns of the grounding cable establish resistance to rapid discharge. See page 201 of The Lightning Book, referred to above. This resistance usually causes the discharge to jump to the ground wire with flexure and in a path of least resistance. In EP-A-0 071 435 an energy cable is described which includes an internal conductor and a shock conductor wound around the inner conductor in a spiral manner even though it is not in direct contact with the inner conductor. JP-A-7122116 describes elements similar to EP-A-0 071 435.

OBJECTS OF THE INVENTION It is an object of this invention to provide an improved beam retarder cable. It is another object to provide a lightning retardant cable that faces electrical and magnetic fields caused by lightning.

BRIEF DESCRIPTION OF THE INVENTION According to one form of this invention, a lightning delay cable is provided that includes at least one internal conductor. The internal conductor can be a signal conductor or a power conductor. A signal driver carries a signal containing information. An energy conductor conducts current to operate devices and equipment. A shock driver is provided. The shock conductor is wound around the inner conductor in the form of a spiral. The shock driver is not in contact with the internal driver. The shock conductor has a high impedance to the electric current caused by the beam when the beam hits near the cable. Preferably, the inner conductor is made of metal to conduct electrical signals or current, although the inner conductor may be an optical fiber. It is also preferred that a spiral shield be placed below the shock conductor. The spiral shield is also wound around the inner conductor, although in a direction opposite to the shock conductor. The adjacent windings of the shield are not in electrical contact with each other and act as a shock conductor. Preferably, angles of 90 ° are formed at the crossing points between the shock conductor and the shield. The shock conductor dissipates the electric field caused by the impact of the beam. The shield performs two functions. It acts as a shock in the opposite direction to the shock driver and therefore improves the cancellation process and acts as a Faraday Cage to greatly reduce the associated magnetic field. It is also preferred that one side of the shield be insulated so that when the shield is wound around the wire a winding is not in electrical contact with the previous or following winding. This forms a shock shield. It is also preferred that a general external jacket be provided for the cable and that a grounding conductor be attached to an external jacket.

BRIEF DESCRIPTION OF THE DRAWINGS The subject matter that is considered to be the invention is set forth in the appended claims. However, the invention itself, together with the objects and additional advantages thereof can be better understood with reference to the accompanying drawings in which: Figure 1 is a simplified electrical diagram showing an antenna signal transmission and connection system to Earth; Figure 2 is a simplified electrical diagram showing the antenna signal transmission and grounding system of the present invention; Figure 3 is also a simplified electrical diagram showing the antenna signal transmission and grounding system of the present invention; Figure 4 is an elevation view of the lightning retarder cable of the present invention; Figure 5 is a side elevation view of an alternative embodiment of the lightning retarder cable of the present invention; Figure 6 is a side elevational view of another alternative embodiment of the lightning retarder cable of the present invention; Figure 7 is a side elevational view of yet another alternative embodiment of the retarder cable of the present invention; Figure 8 is a cross-sectional view of the spiral shield of Figures 5, 6 and 7; Figure 9 is a side elevation view of another alternative embodiment of the lightning retarder cable of the present invention for an energy application.

DESCRIPTION OF THE PREFERRED MODALITIES Referring now more particularly to Figure 3 which refers to an embodiment of the invention where the lightning delay cable is a communication cable, an antenna signal transmission system and ground connection 24 for the ground antenna 10 is provided. As previously indicated, the antenna 10 may also be a satellite dish for satellite or another device for receiving signals from the air. The system 24 includes the lightning delay cable 26, which is the cable of the present invention and will be described in greater detail below. The lightning delay wire 26 is attached to the antenna 10 in the connector lead box 28. The wire 26 is connected to a standard antenna discharge unit 30. A typical antenna discharge unit 30 is a commercially available Tru Spec from CZ Labs. A coaxial cable 32 is connected to the unloading unit 30 and to the electronic equipment (not shown). A ground wire 34 connects the antenna discharge unit 30 to the ground clamps 36 and 38. The ground clamps 38 are, in turn, connected to the ground rod 39. In addition, the mast antenna 40 is connected to a ground clamp 38 through the ground connection cable 42. Figure 2 is similar to figure 3, although it illustrates some of the details of the cable 26. In the embodiment of the communication cable of this invention , the cable 26 is preferably a coaxial cable, although the coaxial cable 26 would be a fiber optic cable or a two-wire piano cable. A communication cable must include at least one signal conductor. In the preferred embodiment of the communication cable of this invention, the cable 26 is a coaxial cable. Figure 2 illustrates the center conductor 44. The center conductor 44 is the signal conductor and is connected to the terminal box 46 attached to the mast of the antenna 10. The signal conductor 44 is connected through the discharge unit of the antenna. the antenna 30 to the coaxial cable 30. The spiral shock conductor 56 surrounds the signal conductor 44 and is connected to the antenna discharge unit 30, which, in turn, is connected to the grounding conductor 34 The cable 26 will be described in more detail below. Figure 4 shows the lightning delay cable 26 having the central signal conductor 44 which is surrounded by foamed dielectric 50. A standard coaxial cable shielding 52 surrounds the dielectric 50. The insulated sleeve 54 surrounds the shielding 52. A conductor of shock 56 is wound around the external jacket 54 in the form of a spiral. A general external insulated jacket can be placed over the cable to provide cable protection. The shock conductor 56 must be long enough to handle the high currents caused by the beam without melting. The shock conductor 56 must be at least 17 gauge and preferably 10 gauge. Preferably the shock conductor is made of copper. If the shock conductor is made of a group of round copper cables, the group must be equivalent to at least one cable of 17 gauge or greater. Referring now to Figure 2, if the beam hits the antenna 10, the energy of that impact would normally be separated, that is, one half would follow the ground wire 42 and the other half follow the wire 26 to the wire. 39. However, since the cable 26 forms an electric shock due to the spiral shock conductor 56, that is, the conductor 56 actually impacts the current flow due to its high impedance to the lightning current having a time very fast rise, most of the peak follows the ground connection wire 42 to earth and does not follow the cable 26 to earth. Half of the energy from the impact that the cable 26 would derive after a lightning strike would be quickly eliminated by the action of the shock. Each time that the shock conductor 56 is rotated around the cable, it causes the electric field generated by the beam to interact on itself, thereby blocking the flow of current. As with any electric current, there is an electric field, as well as a magnetic field at right angles to the electric field. The beam causes a tremendously large magnetic field due to the huge discharge of electric current. Figure 5 shows an alternative embodiment of the lightning delay cable of the present invention which includes a special shield to block the magnetic component of the lightning discharge, thus acting as a Faraday cage. In Figure 5 there is provided a central signal conductor 44, the dielectric 50, the standard coaxial cable shield 52 and the coaxial cable jacket 54. A substantially flat spiral-wrapped shield 58 is wound over the top of the coaxial sleeve. coaxial cable 54. As shown by a cross section of the spiral shield 58 in Figure 8, the shield includes a conductive upper metal portion 60 which is insulated by a plastic insulation 62 in the lower part, therefore the shielding can be spiraling on itself without causing an electrical short circuit. The metal portion 60 of the shield 58 is preferably made of aluminum or copper, the shield 58 is commercially available. The shock conductor 56 is coiled on top of the shield 58 in the opposite direction to the spiral of the shield 58. Preferably, both the shield 58 and the shock conductor 56 are coiled at 45 ° angles with respect to the conductor of the shield. signal 44. Therefore, the shield and the shock conductor intersect at 90 ° angles. Alternatively, the spirals for the shock conductor and the shield could be adjusted at various angles to maximize the inductance depending on the desired effect. In the embodiment of Figure 5, the shock conductor 56 is in electrical contact with the metal portion 60 of the shield 58. However, in the embodiment of Figure 6, an insulated jacket 64 is provided between the spiral shield 58 and the shock conductor 56 and a small consumer cable 61 is placed in contact with the shield 58 between the shield 58 and the jacket 64. The consumer cable 61 allows the shielding to be conveniently terminated. In the design shown in Figures 5 to 8, the electric and magnetic fields are referred to. The electric field is referred to by the spiral shock conductor 56 which, as indicated above, functions as an electrical shock. The magnetic field is referred to by the spiral shield 58, which acts as a Faraday cage. Also, the spiral shield acts as a flat shock in the opposite direction of the electric spiral shock 56, thereby improving the elimination effect. Therefore, shield 58 has two functions. As indicated above, preferably, the shield 58 is preferably at an angle of 45a with respect to the central transmission signal conductor 44 and is spirally wound in the left-hand housing. The shock conductor 56 is preferably also at an angle of 45 ° to the central conductor 44, although spiraling in the opposite direction around the shield 58, ie, right-handed. The directions in which the shock conductor and the signal conductor are coiled could be reversed. The result is a 90 ° angle between the magnetic shield and the electric shock. • Referring now more particularly to Figure 7, for ease of installation, a ground wire 66 can be made as a component of the cable 26. The ground wire 66 is attached to the outer clamp 65 of the cable. cable and is embedded in plastic that is part of the extruded jacket 65. The grounding cable 66 runs along the cable. The ground wire is fixed apart from the main cable so that it can be easily separated and attached to a ground rod. The cable shown in Figure 5 has been tested in the laboratory and in the field. The results show a substantial improvement over the prior art. The detailed description above describes first the communication cable applications of the invention. Figure 9 shows a lightning delay cable 69 of the present invention for energy applications. The internal conductor 70 and 72 are energy conduits that are normally of a larger caliber than the communication conduits. Frequently a gravel conductor (not shown) is placed adjacent to the power conductors. The conductors 70 and 72 are covered by the insulating jacket 74. The impact conductor 56 is wound in a spiral around the sleeve 74 in the same manner as shown and described with reference to FIG. 4., the shielding arrangement shown in Figures 5, 6 and 7 can also be used in power cable applications. From the foregoing description of the preferred embodiments of the invention, it will be apparent that many modifications may be made thereto. It will be understood, however, that the embodiments of the invention are exemplifications of the invention only and that the invention is not limited to the same. It is therefore understood that the appended claims are intended to cover all modifications as they fall within the true spirit and scope of the invention.

Claims (28)

1. A lightning delay cable 826) comprising: at least one internal conductor (44); a shock conductor (56); the shock conductor (56) wound around the inner conductor (44) in the form of a spiral; the shock conductor (56) that is not in direct contact with the internal conductor (44); the shock conductor (56) having a high impedance to the electric current caused by the beam when the beam impacts near said cable (26); and a spiral shield (58) adjacent to the shock conductor (56); the spiral shield (58) which is wound around the inner conductor (44); the spiral shield (58) is not in direct contact with the inner conductor (44).

A cable (26) according to claim 1, wherein the internal conductor (44) is made of a material that conducts electric current.

3. A cable (26) according to claim 2, wherein the internal conductor (44) is a signal conductor.

4. A cable (26) according to claim 2, wherein the internal conductor (44) is an energy conductor.

5. A cable (26) according to claim 3, wherein the signal conductor (44) is at least one optical fiber to conduct light.

A cable (26) according to claim 2, further including an electrical insulator layer (54) located between the inner conductor (44) and the shock conductor (56).

A cable (26) according to claim 1, wherein the shock conductor (56) has a diameter of at least gauge 17.

A cable (26) according to claim 7, wherein the inner conductor (44) is a signal conductor, a coaxial cable shield (52) surrounding the signal conductor, and an outer jacket (54) covers said shield, whereby the cable (26) is a coaxial cable.

A cable (26) according to claim 1, wherein the impact conductor (56) is coiled at an angle of approximately 45 ° with respect to the inner conductor (44).

A cable (26) according to claim 1, wherein the spiral shield (58) is in the form of a flat conductor.

A cable (26) according to claim 10, wherein at least one side of the flat conductor (58) has an electrical installation attached thereto.

A cable (26) according to claim 11, wherein the shock conductor (56) is in contact with the uninsulated side of the flat conductor of said spiral shield (58).

A cable (26) according to claim 11, further including an insulating layer (64) located between the shock conductor (56) and the spiral shield (58).

14. A cable (26) according to claim 1, wherein the spiral shield (858) and the shock conductor (56) are wound in opposite directions.

15. A cable (26) according to claim 14, wherein the spiral shield (58) and the shock conductor (56) intersect at an angle of approximately 90 °.

16. A cable (26) according to claim 14, further including an outer jacket (65) covering said cable.

17. A cable (26) according to claim 1, further including a ground conductor (66) attached to the outer portion of said cable (26).

18. A cable (26) according to claim 16, further including a ground conductor (66), the ground conductor (66) attached to the external jacket (65).

19. A cable (26) according to claim 2, wherein the spiral angles of the shock conductor (56) and the shield (58) can be adjusted to maximize the inductance.

20. An antenna signal transmission and grounding system comprising the lightning delay wire (26) of claim 1, wherein the inner conductor (44) is a signal conductor for conducting a signal containing information.

21. A system according to claim 20, wherein the signal conductor (44) is made of a metallic material that conducts electric current, and which includes a layer of electrical insulation (64) located between the signal conductor (44) and the shock conductor (56) .

22. A system according to claim 20, wherein the spiral shield (58) is in the form of a planar electrical conductor.

23. A system according to claim 22, wherein at least one side of the flat conductor is electrically isolated.

24. A system according to claim 20, wherein the spiral shield (58) and the shock conductor (56) are wound in opposite directions.

25. A system according to claim 24, wherein the spiral shield (58) and the shock conductor (56) intersect at an angle of approximately 90 °.

26. A system according to claim 20, further including the spiral shield (58) and the shock conductor (56) being wound in opposite directions, a general external jacket (65) covering the cable (26) and a shock conductor (66), the ground conductor (66) attached to the general external jacket (65).

27. A system according to claim 20, further including a ground conductor (66) attached to the outer portion of said cable (26).

28. A system according to claim 20, wherein the shock (56) and the spiral shield (58) are isolated from each other. SUMMARY A cable that delays the rays is provided. The cable includes at least one internal conductor which can be a power conductor or a signal conductor. A shock conductor is wound around the inner conductor in the form of a spiral. If the lightning strikes near the cable or a device that is attached to the cable, such as an antenna, the shock conductor has a high impedance to the current caused by the lightning and will prevent lightning current from flowing inside the shock conductor, thus entering the internal conductor, thus avoiding damage to the internal driver and any associated electronic equipment. Preferably, a shield is also spirally wound around the inner conductor adjacent to the shock conductor in a direction opposite to the shock conductor, whereby the angle formed by the crossing of the shock conductor and the shield is approximately 90. ° to block the magnetic field component of the lightning discharge.