CA2270562A1 - Lightning retardant cable - Google Patents
Lightning retardant cable Download PDFInfo
- Publication number
- CA2270562A1 CA2270562A1 CA002270562A CA2270562A CA2270562A1 CA 2270562 A1 CA2270562 A1 CA 2270562A1 CA 002270562 A CA002270562 A CA 002270562A CA 2270562 A CA2270562 A CA 2270562A CA 2270562 A1 CA2270562 A1 CA 2270562A1
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- Prior art keywords
- conductor
- cable
- set forth
- choke
- shield
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- 239000004020 conductor Substances 0.000 claims abstract description 130
- 230000008054 signal transmission Effects 0.000 claims description 5
- 238000009413 insulation Methods 0.000 claims description 3
- 239000013307 optical fiber Substances 0.000 claims description 2
- 238000010292 electrical insulation Methods 0.000 claims 2
- 239000000463 material Substances 0.000 claims 1
- 239000007769 metal material Substances 0.000 claims 1
- 238000004891 communication Methods 0.000 description 11
- 230000005684 electric field Effects 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B11/00—Communication cables or conductors
- H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
- H01B11/1891—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor comprising auxiliary conductors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B11/00—Communication cables or conductors
- H01B11/02—Cables with twisted pairs or quads
- H01B11/12—Arrangements for exhibiting specific transmission characteristics
- H01B11/125—Specially adapted cable interconnections
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.
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
TITLE OF THE INVENTION
LIGHTNING RETARDANT CABLE
BACKGROUND OF THE INVENTION
This invention relates to electrical cable. More particularly, it relates to electrical cable which retards lightning so that the cable is not substantially affected by the lightning and, in the case of communication cable, the communication signal on a signal conductor within the cable is not substantially affected, as well as its associated equipment.
While this invention is applicable to both power and communication cable, most of the detailed discussion herein will focus on communication cable used in conjunction with an antenna.
As used herein, the term antenna includes television and radio antenna, satellite dishes and other devices which receive electromagnetic signals. A
major problem associated with an antenna is caused by lightning striking the antenna. Often the high current associated with the lightning will travel through the communication cable which is attached between the antenna and electronic equipment. This current will damage the electronic equipment.
According to The Lightning Book, by Peter E. Viemeister, self induction in a conductor may occur during a lightning strike. This occurs because lightning currents may rise at a rate of about 15,000 amperes in a millionth of a second. For a straight conductor with the usual cross section, this surging current can produce nearly 6,000 volts per foot of wire, which is enough to jump an insulated gap to a nearby conductor, such as the center conductor, in a coaxial cable.
Currently lightning protection cable is more focused on the installation of cable within a system. The National Electric Code attempts to insure a proper path for lightning to discharge, thus reducing the damage of 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 lightning strike. Even though -- - - ~-- - -- - ~CA 02270562 1999-04-30 -~ ---electrical codes provide suggestions an installing and grounding equipment, their primary focus is providing a stxaight path to gxound for lightning to discharge and eliminating the differences of potential between the two items.
~igttre 1 is an example of a home TV antenna installation according to the National Electric Code. If lightning were to strike antenna 10, half of the charge would be on ground wire I2 which is attached to the mast 14 of the antenna.
and the other half would be on the coaxial cable's outer shield lb which is connected to the antenna terminals 18. Theoretically, the current on coaxial cable 16 would Liavel to antenna discharging unit 20 and then through grounding conductor 22. The canter conductor or signal conductor of the coaxial cable, however, is unprotected, which means that damage to the electronics in the receiver and other components with the home is likely. Furthermore, the longer the lead-in wire, the greater the problem. As lightning strikes this antenna 10 and discharges to ground, a large electric held is set up along the coaxial lead-in wire 16 and g=ound wire I2. At right angles to this pleetrxe field is an exceptionally strong Lnagnetic field which surrounds all of the cable.
1n addition, lightning f~Ilows the straightest, closest and best path to ground. Any sharp bends, twists or turns of the ground wire sets ug resistance to the quicii dischar;e. Sep P3g~ 2D1 Of The ~l~~g Book, re:er:..~d LO abOVe. T h1S
resistance usually causes the discharge to jump off the ground wire with the bend and into a path of least resistance.
In EP-A-0 07I 435 a power cable is disclosed which includ;s an inner conductor and a choke conductor wound about said inner conductor in a spiral fashion but not being in direct wntact wit.~Z the internal conductor.
fP-A-'712212b discloses similar elements to EP-A-0 071 435.
OBJECTS OF THE IN'VENTYOh' It is one object of this invention to provide an improved lightning retardant cable.
a ~.~~c~ S~
P~'' __ _ _ __ _ _ _ _ _ _ . .,, ,......, CA 02270562 1999-04-30 ' -2a-It is anott~ez object to provide a lightning retardant cable wRich deals with both electric and magnetic fields caused by ligbtnin.g.
~;r~.
_ ;,, r,, , .
WO 98l19314 PCT/IB97/00184 In accordance with one form of this invention there is provided a lightning retardant cable which includes at least one internal conductor. The internal conductor may be a signal conductor or a power conductor. A signal conductor conducts a signal containing information. A power conductor conducts current for operating devices and equipment.
A choke conductor is provided. The choke conductor is wound about the internal conductor in the shape of a spiral. The choke conductor is not in contact with the internal conductor. The choke conductor presents a high impedance to the electrical current caused by lightning when the lightning strikes near the cable.
Preferably, the internal conductor is made of metal for conducting electrical signals or current, although the internal conductor may be an optical fiber.
It is also preferred that a spiraled shield be placed underneath the choke conductor. The spiraled shield is also wound about the internal conductor, but in an opposite direction to the choke conductor. The adjacent windings of the shield are not in electrical contact with one another and act as another choke.
Preferably, 90~
angles are formed at the crossing points between the choke conductor and the shield.
The choke conductor dissipates the electric field caused by the lightning strike. The shield performs two functions. It acts as a choke in the opposite direction of the choke conductor and thus enhancing the cancellation process and it acts as a Faraday Cage to greatly reduce the associated magnetic field.
It is also preferred that one side of the shield he insulated so that when the shield is wound about the cable a winding is not in electrical contact with the previous or next winding. This forms a choke shield.
It is also preferred that an overall outer jacket be provided for the cable and that a ground conductor be attached to the outer jacket.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as the invention is set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may be better understood in reference to the accompanying drawings in which:
FIGURE 1 is a simplified electrical diagram showing a prior art antenna signal transmission and grounding system;
FIGURE 2 is a simplified electrical diagram showing the antenna signal transmission and grounding system of the subject invention;
FIGURE 3 is also a simplified electrical diagram showing the antenna signal transmission and grounding system of the subject invention;
FIGURE 4 is a side elevational view of the lightning retardant cable of the subject invention;
FIGURE 5 is a side elevational view of an alternative embodiment of the lightning retardant cable of the subject invention;
FIGURE 6 is a side elevation view of another alternative embodiment of the lightning retardant cable of the subject invention;
FIGURE 7 is a side elevational view of yet another alternative embodiment of the lightning retardant cable of the subject invention;
FIGURE 8 is a cross sectional view of the spiraled shield of Figures 5, 6 and 7;
FIGURE 9 is a side elevational view of another alternative embodiment of the lightning retardant cable of the subj ect invention for a power application.
DESCRIPTION OF THE PREFERRED EMBODIIVViENTS
Referring now more particularly to Figure 3 which relates to an embodiment of the invention where the lightning retardant cable is a communication cable, there is provided antenna signal transmission and grounding system 24 for grounding antenna 10. As previously indicated, antenna IO may also be a satellite WO 98/19314 PCTlIB97/00184 dish or another device for receiving signals from the air. System 24 includes lightning retardant cable 26, which is the cable of the subject invention and will be described in more detail below. Lightning retardant cable 26 is attached to antenna at connector lead box 28. Cable 26 is also connected to standard antenna 5 discharge unit 30. A typical antenna discharge unit 30 is a Tru Spec commercially available from C Z Labs. A coaxial cable 32 is connected to the discharge unit and to electronic equipment (not shown).
A ground wire 34 connects the antenna discharge unit 30 to ground clamps 36 and 38. Ground clamp 38 is, in turn, connected to ground rod 39. In 10 addition, the antenna mast 40 is connected to ground clamp 38 through ground wire 42.
Figure 2 is similar to Figure 3, but illustrates some of the details of cable 26. In the communication cable embodiment of this invention, cable 26 is preferably a coaxial cable, although, cable 26 could be a fiber optic cable or twin lead cable) A communication cable must include at least one signal conductor. In the preferred communication cable embodiment of this invention, however, cable 26 is a coaxial cable. Figure 2 illustrates the center conductor 44. Center conductor 44 is the signal conductor and is connected to terminal box 46 attached to the mast of the antenna 10. Signal conductor 44 is connected through antenna discharge unit 30 to coaxial cable 32. Spiraled choke conductor 56 surrounds signal conductor 44 and is connected to antenna discharge unit 30 which, in turn, is connected to ground conductor 34. Cable 26 will be discussed in more detail below.
Figure 4 shows lightning retardant cable 26 having signal center conductor 44 which is surrounded by foam dielectric 50. A standard coaxial cable shield 52 surrounds the dielectric 50. Insulated jacket 54 surrounds shield 52. A
choke conductor 56 is wound about outer jacket 54 in a spiraled fashion. An overall outer insulated jacket may be placed over the cable to provide protection for the cable. The choke conductor 56 should be large enough to handle the high currents caused by lightning without melting. Choke conductor 56 should be at least 17 gauge and preferably is 10 gauge. Preferably the choke conductor is made of copper.
If the choke conductor is made of a bundle of round copper wires, the bundle should be equivalent to at least 17 gauge wire or larger.
Referring now to Figure 2, if lightning strikes antenna 10, the energy of that strike would normally be split, that is, one-half would follow ground wire 42 and the other half would follow cable 26 to ground rod 39. However, since cable 26 forms an electrical choke due to spiraled choke conductor 56, that is, conductor 56 actually chokes out the flow of current due to its high impedance to lightning current which has a very fast rise time, the majority of the surge follows ground wire 42 to ground and does not follow cable 26 to ground. One-half of the energy from the strike that would start down cable 26 after a lightning strike would quickly be cancelled out by the action of the choke. Each time the choke conductor 56 is twisted around the cable, it causes the electric field generated by the lightning to interact upon itself, thus blocking the flow of current.
As with any electrical discharge, there is an electric field, as well as a magnetic field at right angles to the electric field. Lightning causes a tremendously large magnetic field due to the huge discharge of electric current. Figure 5 shows an alternative embodiment of the lightning retardant cable of the subject 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 center signal conductor 44, dielectric 50, standard coaxial cable shield 52 and coaxial cable jacket 54. A
substantially flat spiraled wrapped shield 58 is wound over the top of coaxial cable jacket 54.
As shown by a cross section of the spiraled shield 58 in Figure 8, the shield includes a conductive top metal portion 60 which is insulated by a plastic insulation 62 on the bottom. Thus the shield may be spiraled upon itself without causing an electrical short. Metal portion 60 of shield 58 is preferably made of aluminum or copper. Shield 58 is commercially available.
Choke conductor 56 is spiraled over the top of shield 58 in the opposite direction to the spiral of shield 58. Preferably, both shield 58 and choke conductor 56 are spiraled at 45 ~ angles with respect to signal conductor 44. Thus the shield and the choke conductor cross at 90 ~ angles. Alternatively, the spirals for both the choke conductor and the shield could be adjusted to various angles to maximize inductance _7_ depending on the desired effect.
' In the embodiment of Figure 5, choke conductor 56 is in electrical contact with the metallic portion 60 of shield 58. However, in the embodiment of Figure 6, an insulated jacket 64 is provided between spiraled shield 58 and choke conductor 56 and a small drain wire 61 is placed in contact with shield 58 between shield 58 and jacket 64. The drain wire 61 enables one to conveniently terminate the shield. In the design shown in Figures 5 through 8, both electric and magnetic fields are addressed. The electric field is addressed by the spiraled choke conductor which, as indicated above, functions as an electrical choke. The magnetic field is addressed by the spiraled shield 58, which acts as a Faraday Cage. Also, the spiraled shield acts as a flat choke in the opposite direction of the spiraled electrical choke 56, thus enhancing the cancellation effect. Therefore, shield 58 has two functions.
As indicated above, preferably, the shield 58 is preferably at a 45 ~
angle with respect to center transmission signal conductor 44 and is spiraled in counterclockwise wrap. The choke conductor 56 is preferably also at a 45 ~
angle with respect to center conductor 44, but is spiraled in the opposite direction around the shield 58, i. e. , clockwise. The directions in which the choke conductor and signal conductor are wound could be reversed. The result is a 90 ~ angle between the magnetic shield and the electric choke.
Referring now more particularly to Figure 7, for ease of installation, a ground wire 66 may be made as a component of the cable 26. Ground wire 66 is attached to the outer jacket 65 of the cable and is embedded in plastic which forms part of the extruded jacket 65. The ground wire 66 runs the length of the cable. The ground wire is set apart from the main cable so that it may easily be detached and attached to a grounding 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 primarily discusses communication cable applications of the invention. Figure 9 shows a lightning retardant cable 69 of the subject invention for power applications. Internal conductor 70 and 72 are power conducts which are normally heavier gauge than communication conductions.
Often WO 98l19314 PCTlIB97100184 _g_ a gravel conductor (not shown) is placed adjacent to the power conductors.
Conductors 70 and 72 are covered by insulated jacket 74. Choke conductor 56 is spiraled about jacket 74 in the same fashion as shown and described in reference to Figure 4. In addition, the shield arrangement shown in Figures 5, 6 and 7 may 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 therein. It will be understood, however, that the embodiments of the invention are exempliflcations of the invention only and that the invention is not limited thereto. It is to be understood therefore that it is intended in the appended claim s to cover all modifications as fall within the true spirit and scope of the invention.
LIGHTNING RETARDANT CABLE
BACKGROUND OF THE INVENTION
This invention relates to electrical cable. More particularly, it relates to electrical cable which retards lightning so that the cable is not substantially affected by the lightning and, in the case of communication cable, the communication signal on a signal conductor within the cable is not substantially affected, as well as its associated equipment.
While this invention is applicable to both power and communication cable, most of the detailed discussion herein will focus on communication cable used in conjunction with an antenna.
As used herein, the term antenna includes television and radio antenna, satellite dishes and other devices which receive electromagnetic signals. A
major problem associated with an antenna is caused by lightning striking the antenna. Often the high current associated with the lightning will travel through the communication cable which is attached between the antenna and electronic equipment. This current will damage the electronic equipment.
According to The Lightning Book, by Peter E. Viemeister, self induction in a conductor may occur during a lightning strike. This occurs because lightning currents may rise at a rate of about 15,000 amperes in a millionth of a second. For a straight conductor with the usual cross section, this surging current can produce nearly 6,000 volts per foot of wire, which is enough to jump an insulated gap to a nearby conductor, such as the center conductor, in a coaxial cable.
Currently lightning protection cable is more focused on the installation of cable within a system. The National Electric Code attempts to insure a proper path for lightning to discharge, thus reducing the damage of 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 lightning strike. Even though -- - - ~-- - -- - ~CA 02270562 1999-04-30 -~ ---electrical codes provide suggestions an installing and grounding equipment, their primary focus is providing a stxaight path to gxound for lightning to discharge and eliminating the differences of potential between the two items.
~igttre 1 is an example of a home TV antenna installation according to the National Electric Code. If lightning were to strike antenna 10, half of the charge would be on ground wire I2 which is attached to the mast 14 of the antenna.
and the other half would be on the coaxial cable's outer shield lb which is connected to the antenna terminals 18. Theoretically, the current on coaxial cable 16 would Liavel to antenna discharging unit 20 and then through grounding conductor 22. The canter conductor or signal conductor of the coaxial cable, however, is unprotected, which means that damage to the electronics in the receiver and other components with the home is likely. Furthermore, the longer the lead-in wire, the greater the problem. As lightning strikes this antenna 10 and discharges to ground, a large electric held is set up along the coaxial lead-in wire 16 and g=ound wire I2. At right angles to this pleetrxe field is an exceptionally strong Lnagnetic field which surrounds all of the cable.
1n addition, lightning f~Ilows the straightest, closest and best path to ground. Any sharp bends, twists or turns of the ground wire sets ug resistance to the quicii dischar;e. Sep P3g~ 2D1 Of The ~l~~g Book, re:er:..~d LO abOVe. T h1S
resistance usually causes the discharge to jump off the ground wire with the bend and into a path of least resistance.
In EP-A-0 07I 435 a power cable is disclosed which includ;s an inner conductor and a choke conductor wound about said inner conductor in a spiral fashion but not being in direct wntact wit.~Z the internal conductor.
fP-A-'712212b discloses similar elements to EP-A-0 071 435.
OBJECTS OF THE IN'VENTYOh' It is one object of this invention to provide an improved lightning retardant cable.
a ~.~~c~ S~
P~'' __ _ _ __ _ _ _ _ _ _ . .,, ,......, CA 02270562 1999-04-30 ' -2a-It is anott~ez object to provide a lightning retardant cable wRich deals with both electric and magnetic fields caused by ligbtnin.g.
~;r~.
_ ;,, r,, , .
WO 98l19314 PCT/IB97/00184 In accordance with one form of this invention there is provided a lightning retardant cable which includes at least one internal conductor. The internal conductor may be a signal conductor or a power conductor. A signal conductor conducts a signal containing information. A power conductor conducts current for operating devices and equipment.
A choke conductor is provided. The choke conductor is wound about the internal conductor in the shape of a spiral. The choke conductor is not in contact with the internal conductor. The choke conductor presents a high impedance to the electrical current caused by lightning when the lightning strikes near the cable.
Preferably, the internal conductor is made of metal for conducting electrical signals or current, although the internal conductor may be an optical fiber.
It is also preferred that a spiraled shield be placed underneath the choke conductor. The spiraled shield is also wound about the internal conductor, but in an opposite direction to the choke conductor. The adjacent windings of the shield are not in electrical contact with one another and act as another choke.
Preferably, 90~
angles are formed at the crossing points between the choke conductor and the shield.
The choke conductor dissipates the electric field caused by the lightning strike. The shield performs two functions. It acts as a choke in the opposite direction of the choke conductor and thus enhancing the cancellation process and it acts as a Faraday Cage to greatly reduce the associated magnetic field.
It is also preferred that one side of the shield he insulated so that when the shield is wound about the cable a winding is not in electrical contact with the previous or next winding. This forms a choke shield.
It is also preferred that an overall outer jacket be provided for the cable and that a ground conductor be attached to the outer jacket.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as the invention is set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may be better understood in reference to the accompanying drawings in which:
FIGURE 1 is a simplified electrical diagram showing a prior art antenna signal transmission and grounding system;
FIGURE 2 is a simplified electrical diagram showing the antenna signal transmission and grounding system of the subject invention;
FIGURE 3 is also a simplified electrical diagram showing the antenna signal transmission and grounding system of the subject invention;
FIGURE 4 is a side elevational view of the lightning retardant cable of the subject invention;
FIGURE 5 is a side elevational view of an alternative embodiment of the lightning retardant cable of the subject invention;
FIGURE 6 is a side elevation view of another alternative embodiment of the lightning retardant cable of the subject invention;
FIGURE 7 is a side elevational view of yet another alternative embodiment of the lightning retardant cable of the subject invention;
FIGURE 8 is a cross sectional view of the spiraled shield of Figures 5, 6 and 7;
FIGURE 9 is a side elevational view of another alternative embodiment of the lightning retardant cable of the subj ect invention for a power application.
DESCRIPTION OF THE PREFERRED EMBODIIVViENTS
Referring now more particularly to Figure 3 which relates to an embodiment of the invention where the lightning retardant cable is a communication cable, there is provided antenna signal transmission and grounding system 24 for grounding antenna 10. As previously indicated, antenna IO may also be a satellite WO 98/19314 PCTlIB97/00184 dish or another device for receiving signals from the air. System 24 includes lightning retardant cable 26, which is the cable of the subject invention and will be described in more detail below. Lightning retardant cable 26 is attached to antenna at connector lead box 28. Cable 26 is also connected to standard antenna 5 discharge unit 30. A typical antenna discharge unit 30 is a Tru Spec commercially available from C Z Labs. A coaxial cable 32 is connected to the discharge unit and to electronic equipment (not shown).
A ground wire 34 connects the antenna discharge unit 30 to ground clamps 36 and 38. Ground clamp 38 is, in turn, connected to ground rod 39. In 10 addition, the antenna mast 40 is connected to ground clamp 38 through ground wire 42.
Figure 2 is similar to Figure 3, but illustrates some of the details of cable 26. In the communication cable embodiment of this invention, cable 26 is preferably a coaxial cable, although, cable 26 could be a fiber optic cable or twin lead cable) A communication cable must include at least one signal conductor. In the preferred communication cable embodiment of this invention, however, cable 26 is a coaxial cable. Figure 2 illustrates the center conductor 44. Center conductor 44 is the signal conductor and is connected to terminal box 46 attached to the mast of the antenna 10. Signal conductor 44 is connected through antenna discharge unit 30 to coaxial cable 32. Spiraled choke conductor 56 surrounds signal conductor 44 and is connected to antenna discharge unit 30 which, in turn, is connected to ground conductor 34. Cable 26 will be discussed in more detail below.
Figure 4 shows lightning retardant cable 26 having signal center conductor 44 which is surrounded by foam dielectric 50. A standard coaxial cable shield 52 surrounds the dielectric 50. Insulated jacket 54 surrounds shield 52. A
choke conductor 56 is wound about outer jacket 54 in a spiraled fashion. An overall outer insulated jacket may be placed over the cable to provide protection for the cable. The choke conductor 56 should be large enough to handle the high currents caused by lightning without melting. Choke conductor 56 should be at least 17 gauge and preferably is 10 gauge. Preferably the choke conductor is made of copper.
If the choke conductor is made of a bundle of round copper wires, the bundle should be equivalent to at least 17 gauge wire or larger.
Referring now to Figure 2, if lightning strikes antenna 10, the energy of that strike would normally be split, that is, one-half would follow ground wire 42 and the other half would follow cable 26 to ground rod 39. However, since cable 26 forms an electrical choke due to spiraled choke conductor 56, that is, conductor 56 actually chokes out the flow of current due to its high impedance to lightning current which has a very fast rise time, the majority of the surge follows ground wire 42 to ground and does not follow cable 26 to ground. One-half of the energy from the strike that would start down cable 26 after a lightning strike would quickly be cancelled out by the action of the choke. Each time the choke conductor 56 is twisted around the cable, it causes the electric field generated by the lightning to interact upon itself, thus blocking the flow of current.
As with any electrical discharge, there is an electric field, as well as a magnetic field at right angles to the electric field. Lightning causes a tremendously large magnetic field due to the huge discharge of electric current. Figure 5 shows an alternative embodiment of the lightning retardant cable of the subject 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 center signal conductor 44, dielectric 50, standard coaxial cable shield 52 and coaxial cable jacket 54. A
substantially flat spiraled wrapped shield 58 is wound over the top of coaxial cable jacket 54.
As shown by a cross section of the spiraled shield 58 in Figure 8, the shield includes a conductive top metal portion 60 which is insulated by a plastic insulation 62 on the bottom. Thus the shield may be spiraled upon itself without causing an electrical short. Metal portion 60 of shield 58 is preferably made of aluminum or copper. Shield 58 is commercially available.
Choke conductor 56 is spiraled over the top of shield 58 in the opposite direction to the spiral of shield 58. Preferably, both shield 58 and choke conductor 56 are spiraled at 45 ~ angles with respect to signal conductor 44. Thus the shield and the choke conductor cross at 90 ~ angles. Alternatively, the spirals for both the choke conductor and the shield could be adjusted to various angles to maximize inductance _7_ depending on the desired effect.
' In the embodiment of Figure 5, choke conductor 56 is in electrical contact with the metallic portion 60 of shield 58. However, in the embodiment of Figure 6, an insulated jacket 64 is provided between spiraled shield 58 and choke conductor 56 and a small drain wire 61 is placed in contact with shield 58 between shield 58 and jacket 64. The drain wire 61 enables one to conveniently terminate the shield. In the design shown in Figures 5 through 8, both electric and magnetic fields are addressed. The electric field is addressed by the spiraled choke conductor which, as indicated above, functions as an electrical choke. The magnetic field is addressed by the spiraled shield 58, which acts as a Faraday Cage. Also, the spiraled shield acts as a flat choke in the opposite direction of the spiraled electrical choke 56, thus enhancing the cancellation effect. Therefore, shield 58 has two functions.
As indicated above, preferably, the shield 58 is preferably at a 45 ~
angle with respect to center transmission signal conductor 44 and is spiraled in counterclockwise wrap. The choke conductor 56 is preferably also at a 45 ~
angle with respect to center conductor 44, but is spiraled in the opposite direction around the shield 58, i. e. , clockwise. The directions in which the choke conductor and signal conductor are wound could be reversed. The result is a 90 ~ angle between the magnetic shield and the electric choke.
Referring now more particularly to Figure 7, for ease of installation, a ground wire 66 may be made as a component of the cable 26. Ground wire 66 is attached to the outer jacket 65 of the cable and is embedded in plastic which forms part of the extruded jacket 65. The ground wire 66 runs the length of the cable. The ground wire is set apart from the main cable so that it may easily be detached and attached to a grounding 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 primarily discusses communication cable applications of the invention. Figure 9 shows a lightning retardant cable 69 of the subject invention for power applications. Internal conductor 70 and 72 are power conducts which are normally heavier gauge than communication conductions.
Often WO 98l19314 PCTlIB97100184 _g_ a gravel conductor (not shown) is placed adjacent to the power conductors.
Conductors 70 and 72 are covered by insulated jacket 74. Choke conductor 56 is spiraled about jacket 74 in the same fashion as shown and described in reference to Figure 4. In addition, the shield arrangement shown in Figures 5, 6 and 7 may 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 therein. It will be understood, however, that the embodiments of the invention are exempliflcations of the invention only and that the invention is not limited thereto. It is to be understood therefore that it is intended in the appended claim s to cover all modifications as fall within the true spirit and scope of the invention.
Claims (28)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
WHAT I/WE CLAIM AS MY/OUR INVENTION:
1. A lightning retardant cable (26) comprising:
at least one internal conductor (44);
a choke conductor (56); said choke conductor (56) wound about said internal conductor (44) in the shape of a spiral; said choke conductor (56) not being in direct contact with said internal conductor (44); said choke conductor (56) presenting a high impedance to electrical current caused by lightning when lightning strikes near said cable (26); and a spiraled shield (58) adjacent to said choke conductor (56); said spiraled shield (58) being wound about said internal conductor (44); said spiraled shield (58) not in direct contact with said internal conductor (44).
at least one internal conductor (44);
a choke conductor (56); said choke conductor (56) wound about said internal conductor (44) in the shape of a spiral; said choke conductor (56) not being in direct contact with said internal conductor (44); said choke conductor (56) presenting a high impedance to electrical current caused by lightning when lightning strikes near said cable (26); and a spiraled shield (58) adjacent to said choke conductor (56); said spiraled shield (58) being wound about said internal conductor (44); said spiraled shield (58) not in direct contact with said internal conductor (44).
2. A cable (26) as set forth in Claim 1, wherein said internal conductor (44) is made of a material which conducts electrical current.
3. A cable (26) as set forth in Claim 2, wherein said internal conductor (44) is a signal conductor.
4. A cable (26) as set forth in Claim 2, wherein said internal conductor (44) is a power conductor.
5. A cable (26) as set forth in Claim 3, wherein said signal conductor (44) is at least one optical fiber for conducting light.
6. A cable (26) as set forth in Claim 2, further including an electrical insulation layer (54) located between said internal conductor (44) and paid choke conductor (56).
7. A cable (26) as set forth in Claim 1, wherein said choke conductor (56) has a diameter of at least 17 gauge.
8. A cable (26) as set forth in Claim 7, wherein said internal conductor (44) is a signal conductor, a coaxial cable shield (52) surrounds said signal conductor, and an outer jacket (54) covers said shield, whereby said cable (26) is a coaxial cable.
9. A cable (26) as set forth in Claim 1, wherein said choke conductor (56) is spiraled at an angle of approximately 45° with respect to said internal conductor (44).
10. A cable (26) as set forth in Claim 1, wherein said spiraled shield (58) is in the form of a flat conductor.
11. A cable (26) as set forth in Claim 10, wherein at least one side of said flat conductor (58) has electrical insulation attached thereto.
12. A cable (26) as set forth in Claim 11, wherein said choke conductor (26) is in contact with the uninsulated side of said flat conductor of said spiraled shield (58).
13. A cable (26) as set forth in Claim 11, further including an insulation layer (64) located between said choke conductor (56) and said spiraled shield (58).
14. A cable (26) as set forth in Claim 1, wherein said spiraled shield (58) and said choke conductor (56) are wound in opposite directions.
15. A cable (26) as set forth in Claim 14, wherein said spiraled shield (58) and said choke conductor (56) cross one another at an angle of approximately 90°.
16. A cable (26) as set forth in Claim 14, further including an outer jacket (65) covering said cable.
17. A cable (20) as set forth in Claim 1, further including a ground conductor (66) attached to the outer portion of said cable (26).
18. A cable (26) as set forth in Claim 16, further including a ground conductor (66); said ground conductor (66) attached to the said outer jacket (65).
19. A cable (26) as set forth in Claire 14, wherein the spiral angles of said choke conductor (56) and said shield (58) may be adjusted to maximize inductance.
20. An antenna signal transmission and grounding system comprising the lightning retardant cable (26) of Claim 1 wherein said internal conductor (44) is a signal conductor for conducting a signal containing information.
21. A system as set forth in Claim 20, wherein said signal conductor (44) is made of a metallic material which conducts electrical and including an electric insulation layer (64) located between said signal conductor (44) and said choke conductor (56).
22. A system as set forth in Claim 20, wherein said spiraled shield (58) is in the form of a flat electrical conductor.
23. A system as set forth in Claim 22, wherein at least one side of said flat conductor is electrically insulated.
24. A system as set forth in Claim 20, wherein said spiraled shield (58) and said choke conductor (56) are wound in opposite directions.
25. A system as set forth in Claim 24, wherein said spiraled shield (58) and said choke conductor (56) cross one another at an angle of approximately 90°.
26. A system as set forth in Claim 20, further including said spiraled shield (58) and said choke conductor (55) being wound in opposite directions, an overall outer jacket (65) covering said cable (26), and a ground conductor (66), said ground conductor (66) attached to said overall outer jacket (65).
27. A system as set forth in Claim 24, further including a ground conductor (66) attached to the outer portion of said cable (26).
28. A system as set forth in Claim 20, wherein said choke (55) and said spiraled shield (58) are insulated from one another.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/741,536 US5744755A (en) | 1996-10-31 | 1996-10-31 | Lightning retardant cable |
| US08/741,536 | 1996-10-31 | ||
| PCT/IB1997/000184 WO1998019314A1 (en) | 1996-10-31 | 1997-02-28 | Lightning retardant cable |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2270562A1 true CA2270562A1 (en) | 1998-05-07 |
Family
ID=24981100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002270562A Abandoned CA2270562A1 (en) | 1996-10-31 | 1997-02-28 | Lightning retardant cable |
Country Status (23)
| Country | Link |
|---|---|
| US (1) | US5744755A (en) |
| EP (1) | EP0935807A1 (en) |
| JP (1) | JP2001503191A (en) |
| KR (1) | KR20000052957A (en) |
| CN (1) | CN1240047A (en) |
| AP (1) | AP9901545A0 (en) |
| AU (1) | AU1730897A (en) |
| BR (1) | BR9712400A (en) |
| CA (1) | CA2270562A1 (en) |
| CU (1) | CU22671A3 (en) |
| CZ (1) | CZ155899A3 (en) |
| EA (1) | EA199900434A1 (en) |
| EE (1) | EE9900181A (en) |
| HU (1) | HUP0000796A2 (en) |
| IL (1) | IL129640A0 (en) |
| IS (1) | IS5039A (en) |
| NO (1) | NO992093L (en) |
| NZ (1) | NZ335958A (en) |
| OA (1) | OA11042A (en) |
| PL (1) | PL333062A1 (en) |
| SK (1) | SK58899A3 (en) |
| TR (1) | TR199900962T2 (en) |
| WO (1) | WO1998019314A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6278599B1 (en) * | 1996-10-31 | 2001-08-21 | Mag Holdings, Inc | Lightning retardant cable and conduit systems |
| US6894226B2 (en) * | 1998-04-06 | 2005-05-17 | Sumitomo Electric Industries, Ltd. | Coaxial cables, multicore cables, and electronic apparatuses using such cables |
| US6414239B1 (en) | 2000-02-23 | 2002-07-02 | Mag Holdings, Inc. | Method and apparatus for reducing the magnetic field associated with an energized power cable |
| WO2007059600A1 (en) * | 2005-11-23 | 2007-05-31 | Rizk Farouk A M | Lightning protection device: wet/dry glow-based streamer inhibitor |
| US7307211B1 (en) | 2006-07-31 | 2007-12-11 | Coleman Cable, Inc. | Served braid leakage current detecting cable |
| CN103474975B (en) * | 2013-09-28 | 2016-05-25 | 成都星河科技产业有限公司 | A kind of thunder-lightning nano magnetic choke apparatus |
| KR101381805B1 (en) * | 2013-12-12 | 2014-04-07 | 기찬정보통신(주) | Apparatus and method for monitoring ground line |
| KR102507846B1 (en) * | 2016-03-08 | 2023-03-10 | 삼성디스플레이 주식회사 | Cable module for display device |
| US10209328B2 (en) | 2016-05-27 | 2019-02-19 | General Electric Company | Systems and methods for common mode traps in MRI systems |
| US10379181B2 (en) * | 2016-05-27 | 2019-08-13 | General Electric Company | Systems and methods for common mode traps in MRI systems |
| KR102602065B1 (en) * | 2017-11-06 | 2023-11-14 | 엘에스전선 주식회사 | Marking Cable and Distance Estimation System Using The Same |
| CN109004339A (en) * | 2018-06-26 | 2018-12-14 | 合肥聚能电物理高技术开发有限公司 | The production tooling and its manufacture craft of the Faraday shield of spiral wave antenna |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3297814A (en) * | 1964-11-02 | 1967-01-10 | Northern Electric Co | Semi-conducting sheath selfsupporting cable |
| US3351706A (en) * | 1965-03-18 | 1967-11-07 | Simplex Wire & Cable Co | Spaced helically wound cable |
| US3484679A (en) * | 1966-10-03 | 1969-12-16 | North American Rockwell | Electrical apparatus for changing the effective capacitance of a cable |
| US4119793A (en) * | 1976-04-26 | 1978-10-10 | Electric Power Research Institute, Inc. | Transmission line breakdown voltage |
| FR2437686A1 (en) * | 1978-09-29 | 1980-04-25 | Mayer Ferdy | LOSS ELECTRIC ELEMENT, SUCH AS WIRE, CABLE AND SCREEN, RESISTANT AND ABSORBENT |
| US4268714A (en) * | 1979-05-16 | 1981-05-19 | Sumitomo Electric Industries, Ltd. | Shielded wire |
| GB2106306B (en) * | 1981-07-28 | 1985-07-31 | Pirelli General Plc | Improvements in electric cables and installations |
| GB2160011A (en) * | 1984-06-05 | 1985-12-11 | Nat Res Dev | Electrical conductors |
| GB8601270D0 (en) * | 1986-01-20 | 1986-02-26 | Raychem Ltd | High frequency attenuation cable |
| DE3602966A1 (en) * | 1986-01-31 | 1987-08-06 | Kabelmetal Electro Gmbh | METHOD FOR PRODUCING A FLEXIBLE ELECTRICAL LINE |
| US4719319A (en) * | 1986-03-11 | 1988-01-12 | Amp Incorporated | Spiral configuration ribbon coaxial cable |
| US5218167A (en) * | 1986-11-28 | 1993-06-08 | Gasque Jr Samuel N | Cable assembly with lightning protection |
| US5061823A (en) * | 1990-07-13 | 1991-10-29 | W. L. Gore & Associates, Inc. | Crush-resistant coaxial transmission line |
| FR2674365B1 (en) * | 1991-03-21 | 1993-06-04 | Filotex Sa | COAXIAL CABLE WITH LOW LOSSES. |
| JP3146450B2 (en) * | 1993-10-20 | 2001-03-19 | 中部電力株式会社 | Lightning resistant optical fiber composite overhead ground wire |
-
1996
- 1996-10-31 US US08/741,536 patent/US5744755A/en not_active Expired - Lifetime
-
1997
- 1997-02-28 CA CA002270562A patent/CA2270562A1/en not_active Abandoned
- 1997-02-28 EP EP97904539A patent/EP0935807A1/en not_active Withdrawn
- 1997-02-28 EE EEP199900181A patent/EE9900181A/en unknown
- 1997-02-28 AP APAP/P/1999/001545A patent/AP9901545A0/en unknown
- 1997-02-28 SK SK588-99A patent/SK58899A3/en unknown
- 1997-02-28 WO PCT/IB1997/000184 patent/WO1998019314A1/en not_active Application Discontinuation
- 1997-02-28 CZ CZ991558A patent/CZ155899A3/en unknown
- 1997-02-28 HU HU0000796A patent/HUP0000796A2/en unknown
- 1997-02-28 JP JP10520216A patent/JP2001503191A/en not_active Ceased
- 1997-02-28 BR BR9712400-1A patent/BR9712400A/en unknown
- 1997-02-28 IL IL12964097A patent/IL129640A0/en unknown
- 1997-02-28 KR KR1019990703830A patent/KR20000052957A/en not_active Application Discontinuation
- 1997-02-28 NZ NZ335958A patent/NZ335958A/en unknown
- 1997-02-28 AU AU17308/97A patent/AU1730897A/en not_active Abandoned
- 1997-02-28 TR TR1999/00962T patent/TR199900962T2/en unknown
- 1997-02-28 PL PL97333062A patent/PL333062A1/en unknown
- 1997-02-28 CN CN97199354A patent/CN1240047A/en active Pending
- 1997-02-28 EA EA199900434A patent/EA199900434A1/en unknown
-
1999
- 1999-04-29 CU CU1999057A patent/CU22671A3/en unknown
- 1999-04-29 NO NO992093A patent/NO992093L/en not_active Application Discontinuation
- 1999-04-29 IS IS5039A patent/IS5039A/en unknown
- 1999-04-30 OA OA9900093A patent/OA11042A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NO992093L (en) | 1999-05-31 |
| WO1998019314A1 (en) | 1998-05-07 |
| CZ155899A3 (en) | 1999-10-13 |
| US5744755A (en) | 1998-04-28 |
| AU1730897A (en) | 1998-05-22 |
| IL129640A0 (en) | 2000-02-29 |
| AP9901545A0 (en) | 1999-06-30 |
| OA11042A (en) | 2002-02-07 |
| HUP0000796A2 (en) | 2000-07-28 |
| EP0935807A1 (en) | 1999-08-18 |
| NZ335958A (en) | 2000-03-27 |
| CN1240047A (en) | 1999-12-29 |
| TR199900962T2 (en) | 1999-07-21 |
| PL333062A1 (en) | 1999-11-08 |
| EA199900434A1 (en) | 2000-06-26 |
| KR20000052957A (en) | 2000-08-25 |
| BR9712400A (en) | 2000-01-25 |
| IS5039A (en) | 1999-04-29 |
| CU22671A3 (en) | 2001-06-01 |
| EE9900181A (en) | 1999-12-15 |
| SK58899A3 (en) | 2000-03-13 |
| NO992093D0 (en) | 1999-04-29 |
| JP2001503191A (en) | 2001-03-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |