RU2688897C1 - Optical cable in lightning protection cable - Google Patents

Abstract

FIELD: optics.SUBSTANCE: group of inventions relates to fibre-optic communication lines. Optical cable in lightning protection cable, which provides for minimization of longitudinal magnetic field formed in area of optical fibre when current pulse passes in lightning protection cable, comprises a central tube with optical fibres arranged inside and at least two wires of wires of metal and/or composite materials. Wires are arranged on the central tube so that the twisting direction of adjacent wires of the wires is alternated in the cable. At the same time combination of wire materials in layers, design parameters of wires and twisting steps of coats are selected so that modulus of sum |Σ| electric conductivity corresponding to constituent of formed magnetic field in each of layers, is minimum for given set of structural parameters of layers and properties of materials:, where n is number of wires; k - number of the underbody;is the component of the longitudinal magnetic field of the klayer; Z- resistance of the electric circuit of substitution for the klayer of the optical cable in the lightning-proof cable at passing of the current pulse in the lightning protection cable, depending on the design parameters of the layers, including the diameter of the wire, pitch and the diameter of the layer, and physical properties of wires materials, including electric conductivity and magnetic permeability of material kwire stranding; m- ratio of twisting pitch of klayer of wires, m= h/ D, h- twisting pitch of kwire layer, Dis diameter of circle circumscribed around klayer of wires.EFFECT: technical result consists in ensuring high operational reliability, in attenuating the effect of lightning on transmitting an optical signal and in reducing loss of transmitted information.14 cl, 12 dwg

Description

Technical field

The present invention relates to fiber optic communication lines, in particular to optical cables embedded in a ground wire, and can be used to increase the protection of optical communication systems on overhead power lines during lightning strikes.

Prior art

Typical modern designs of optical cables embedded in a ground wire are a central sealed metal tube with optical fibers, over which one or more flashing consisting of combinations of steel wires clad with aluminum and / or wires of aluminum or aluminum alloy are superimposed.

The function of the central sealed metal tube is to protect the fibers from environmental factors, aluminum-clad steel wires withstand mechanical tensile stress, and aluminum or aluminum-alloy wires are electrical conductors that transport lightning-induced currents from the point of impact to the ground.

The impact of lightning currents in addition to the well-known thermal effect on the cable elements leads to the generation of a pulsed magnetic field inside an optical cable, consisting in the case of a straight-line cable from a longitudinal (axial) component. Recent studies and information provided by telecom operators indicate that a rapidly changing longitudinal magnetic field adversely affects the transmission of information over the fiber using a compression format for light polarizations, i.e. there is a loss of transmitted information. The phenomenon is caused by the rapid rotation of the axis of polarization of light in a fiber under the influence of a varying magnetic field parallel to the axis of the fiber, in accordance with Faraday law.

The angle of rotation of the plane of polarization of light in an optical fiber depends on the magnitude of the intensity of the longitudinal component of the magnetic field and is:

,

,

where: V- Verde constant V = 0.7 × 10 ^-6 rad / km; H is the longitudinal component of the magnetic field strength in an optical fiber, A / m; l is the length of the optical fiber exposed to the field, m

When a lightning strike occurs, the magnetic field picture on the central axis of an optical cable is determined by its design, in which each layer of wire behaves like a solenoid, and the currents flowing in each layer create on the central axis of the optical cable mainly longitudinally directed magnetic field components. The angle of rotation of the polarization plane on the axis of the solenoid, in which the current flows, is:

,

,

- длина соленоида, м.where: V-Verde constant V = 0.7 × 10 ^-6 rad / A; n is the number of turns per unit length of the solenoid 1 / m; I is the current flowing in the coil of the solenoid, A;

- length of the solenoid, m

The selection of wire parameters in the windings and the direction of wire twist significantly reduces the amplitude of the magnitude of the longitudinal component of the pulsed magnetic field with a corresponding weakening of the effect of lightning on the transmission of the optical signal.

Electromagnetic processes occurring in the cable can be described by processes occurring in the circuits and further investigated by the method of the theory of electrical circuits. In this case, each wire is considered as a set of inductors in which substitution currents flow from a lightning strike, and each layer can be represented by a passive two-port network, and a set of cable wire strands can be represented by a cascade connection of single-type four-pole networks. The task of finding the minimum magnitude of the magnetic field is reduced to finding the minimum value of the modulus of the total conductivity of the electrical equivalent circuit.

As the nearest technical solution is considered a utility model disclosed in patent RU 145245 U (IPC G02B 6/44, published 06.06.2014). The patent discloses an optical cable embedded in a ground wire, containing an optical module in the form of a sealed tube, with optical fibers laid inside it, filling the internal volume of the tube with a hydrophobinol filler. Around one optical fiber module or several metal elements are twisted around the optical module. The sealed tube of the optical module is made of stainless steel or aluminum, or the steel tube can be enclosed in aluminum, and the layers applied to the sealed tube can be made of steel wire clad with aluminum or aluminum, or aluminum alloy, or combined combinations of steel wire clad with aluminum and wires made of aluminum or aluminum alloy.

The disadvantage of these cables is that the optical fibers of the cables are susceptible to electromagnetic interference caused by lightning strikes, which leads to communication failure and, therefore, loss when using such cables as part of high-speed transmission systems with polarization separation of light signals due to the effect of an electromagnetic pulse arising from a lightning strike.

Summary of the Invention

The technical problem solved by the proposed invention is the elimination of these disadvantages of the known optical cables embedded in the ground wire, and the creation of an optical cable embedded in the ground wire, which provides high operational reliability, which consists in increasing the resistance of the optical cable to the effects of short circuit current operation during a lightning strike, by lowering the amplitude of the longitudinal component of the pulsed magnetic field, which will lead to appropriately reducing the effect of lightning on the transmission of the optical signal and will reduce the loss of transmitted information when using cables in systems with polarization separation of light signals.

According to the first embodiment of the invention, said technical result is achieved in that the optical cable in a ground wire, minimizing the longitudinal magnetic field generated in the area of the optical fiber during the passage of a current pulse in a ground wire, contains:

central tube with optical fibers located inside it,

at least two poviv wires from metal and / or composite materials placed on the central tube so that

the cable provides alternation of the direction of twisting of the adjacent layers of the wires,

at the same time, the combination of wire materials in the strands, the design parameters of the wires, and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings, is minimal for a given set of design parameters of the windings and material properties:

, (1)

, (one)

where: n - the number of windings wires;

k - number of dressing;

- составляющая продольного магнитного поля k-ого повива;

- component of the longitudinal magnetic field of the k-th layer;

- сопротивление электрической схемы замещения для k-го повива оптического кабеля в грозозащитном тросе при прохождении импульса тока в грозозащитном тросе, зависящее от конструктивных параметров повивов, включающих диаметр провода, шаг скрутки и диаметр повива, и физических свойств материалов проволок, включающих электропроводность и магнитную проницаемость материала k-го повива проволок;

- resistance of the electrical equivalent circuit for the k-th fiber sheet of the optical cable in the ground wire during the passage of a current pulse in the ground wire depending on the design parameters of the layers, including the wire diameter, twist pitch and the diameter of the sheet, and the physical properties of the wire materials, including electrical conductivity and magnetic permeability material of the k- th layer;

m _k - the multiplicity step of twisting the k-th dressing wire,

m _k = h _k / D _k ,

h _k - the twist pitch of the k-th layer of wires,

D _k - the diameter of the circle described around the k-th dressing wire.

Preferably, the wires of metal and / or composite materials have different electrical conductivity.

Preferably, in the optical cable, wires from metallic materials used in the coatings contain steel wire having a protective anticorrosion coating and aluminum alloy wire.

Preferably, the steel wires used in the windings, having a protective anti-corrosion coating, are made of steel clad with aluminum.

The use of wires made of composite materials.

Preferably, the central tube in which the optical fibers are placed is made of metal.

According to the second embodiment of the invention, said technical result is achieved by the fact that an optical cable in a ground wire, minimizing the longitudinal magnetic field generated in the area of the optical fiber during the passage of a current pulse in a ground wire, contains:

central element in the form of wire or hollow tube

at least three poviv wires from metal and / or composite materials placed on the central element, so that the specified cable provides alternation of the direction of twisting of adjacent poviv wires,

at least one tube with optical fibers placed in one of the layers of the wires,

the optical cable contains so many windings that the number of windings external to the winding containing the tube / tubes with optical fibers and furthest from the central element is two,

at the same time, the combination of wire materials in the strands, the design parameters of the wires, and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings is minimal for a given set of design parameters of windings and material properties:

, (2)

, (2)

where: n - the number of windings wires;

k - number of dressing;

- составляющая продольного магнитного поля k-ого повива;

- component of the longitudinal magnetic field of the k-th layer;

- сопротивление электрической схемы замещения для k-го повива при прохождении импульса тока, обусловленного внешним воздействием, зависящее от конструктивных параметров повивов, включающих диаметр провода, шаг скрутки и диаметр повива, и физических свойств, включающих электропроводность и магнитную проницаемость, материала k- го повива проволок;

- resistance of the electrical equivalent circuit for the k-th layer during the passage of a current pulse caused by an external effect, depending on the design parameters of the layers, including the wire diameter, twist pitch and the diameter of the sheet, and physical properties, including electrical conductivity and magnetic permeability, of the k -th sheet material wire;

m _k - the multiplicity step of twisting the k-th dressing wire,

m _k = h _k / D _k ,

h _k - the twist pitch of the k-th layer of wires,

D _k - the diameter of the circle described around the k-th dressing wire,

1 / Z _k = 0 for the k-th layer of wires having at least one tube with optical fibers placed in this layer.

Preferably, the wires of metal and / or composite materials have different electrical conductivity.

It is preferable that the wires of metallic materials used in the windings contain steel wire having a protective anti-corrosion coating and aluminum alloy wire.

Preferably, the steel wires used in the windings, having a protective anti-corrosion coating, are made of steel clad with aluminum.

The use of wires made of composite materials.

It is possible that the optical cable additionally contains at least one tube with optical fibers placed in another of the wire filaments, while the optical cable contains so many layers that the number of layers external to the layer containing the tube / tubes with optical fibers and most remote from the central element, was equal to two.

According to a third embodiment of the invention, said technical result is achieved in that the optical cable in a ground wire, minimizing the longitudinal magnetic field generated in the area of the optical fiber during the passage of a current pulse in a ground wire, contains:

central element in the form of a tube with optical fibers,

at least three poviv wires from metal and / or composite materials placed on the central element,

at least one tube with optical fibers placed in one of the layers of the wires,

while in the optical cable is provided by the alternation of the direction of twisting of the adjacent layers of the wires,

the cable contains so many windings that the number of windings external to the winding containing the tube with optical fibers is equal to two,

at the same time, the combination of wire materials in the strands, the design parameters of the wires, and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings is minimal for a given set of design parameters of windings and material properties:

, (3)

, (3)

Where:

n is the number of windings wire;

k - number of dressing;

- составляющая продольного магнитного поля k-ого повива;

- component of the longitudinal magnetic field of the k-th layer;

- сопротивление электрической схемы замещения для k-го повива при прохождении импульса тока, обусловленного внешним воздействием, зависящее от конструктивных параметров повивов, включающих диаметр провода, шаг скрутки и диаметр повива, и физических свойств, включающих электропроводность и магнитную проницаемость, материала k-го повива проволок;

- resistance of the electrical equivalent circuit for the k-th layer during the passage of a current pulse due to an external influence, depending on the design parameters of the layers, including the wire diameter, twist pitch and the diameter of the sheet, and physical properties, including electrical conductivity and magnetic permeability, of the k- th sheet material wire;

m _k - the multiplicity step of twisting the k-th dressing wire,

m _k = h _k / D _k ,

h _k - the twist pitch of the k-th layer of wires,

D _k - the diameter of the circle described around the k-th dressing wire,

1 / Z _k = 0 for the k-th layer of wires having at least one tube with optical fibers placed in this layer.

Preferably, the wires of metal and / or composite materials have different electrical conductivity.

It is preferable that the wires of metallic materials used in the windings contain steel wire having a protective anti-corrosion coating and aluminum alloy wire.

Preferably, the steel wires used in the windings, having a protective anti-corrosion coating, are made of steel clad with aluminum.

The use of wires made of composite materials.

The proposed optical cable in the ground wire ensures the minimum electromagnetic impact on the cable optical fiber and, accordingly, reduces the angle of rotation of the polarization axis of the optical signal, increases noise immunity and reduces the loss of information when using cables in systems with separation of light signals from lightning strikes.

The proposed principles for the selection of cable designs make it possible to reduce the effect of an electromagnetic pulse arising from a lightning strike on optical fibers of high-speed fiber-optic communication systems using polarization separation of optical signals. In general, the proposed design choice principle allows to increase the operational reliability of high-speed fiber-optic communication systems.

Brief Description of the Drawings

The invention is further explained in the description of the preferred embodiments with reference to the accompanying drawings, in which:

FIG. 1A depicts an electric circuit for replacing cable stitches for pulsed lightning currents;

FIG. 1B depicts a four-port circuit in the electric circuit of the layouts;

FIG. 2 shows the first embodiment of an optical cable in a ground wire with a central tube with optical fibers (cross section) and two layers of wires having different directions of twisting;

FIG. 3 depicts a second embodiment of an optical cable in which the optical cable comprises a central element in the form of a wire, wherein the tubes with optical fibers are placed in a sheet adjacent to the central element (cross section);

FIG. 4 shows a second embodiment of an optical cable in which the optical cable comprises a central element in the form of a hollow tube, wherein the tubes with optical fibers are arranged in two layers adjacent to the central element (cross section);

FIG. 5 shows a third embodiment of an optical cable in a grounding cable with a central tube with optical fibers, which further comprises at least one tube with optical fibers located in a layer adjacent to the central tube (cross section);

FIG. 6 shows a functional diagram of a test facility, in which an optical cable is used in a ground wire with a central tube with optical fibers, to which an optical radiation source and an optical signal polarization analyzer are connected;

FIG. 7 schematically depicts a test facility, showing two versions of optical cables suspended in supports, in a ground wire, the first option containing a cable with one twist, and the second version containing a cable with two flashing;

FIG. 8 shows the electrical impulse supplied to the cable during testing;

FIG. 9 depicts the trail on the Poincaré sphere for the duration of the current pulse for a cable containing one twisted wire;

FIG. 10 depicts the normalized components of the Stokes for the duration of the current pulse for a cable containing one twisted wire;

FIG. 11 depicts the trail on the Poincaré sphere for the duration of the current pulse for a cable containing two layers of wire;

FIG. 12 depicts the normalized components of the Stokes for the duration of the current pulse for a cable containing two layers of wires.

Theoretical justification of the proposed technical solution

The claimed design is described using the method of representing mesh screens of cables in the form of equivalent circuits, representing a cascade connection of quadrupoles, assuming that the equivalent circuit of laying the wires of a cable during the flow of a pulsed lightning electric current in it is the same as when a high-frequency induced current flows. In this case, the description differs from the point of view that the interaction of the fields from each of the strand wires in the inner region of the cable is considered, while the strand wires are regarded as having different directions of twisting and weakly interacting with each other.

(1) представляет собой упрощенное выражение для эквивалентной проводимости электрической схемы замещения повивов проволок кабеля. Электрическая схема представляет собой последовательное соединение n четырехполюсников (фиг. 1А, фиг. 1В), по числу повивов проволок кабеля, где каждый повив k в кабеле описывается Г-образным четырехполюсником 2, в котором каждое из параллельно подключенных комплексных сопротивлений

Г-образных четырехполюсников представляют собой импеданс витков проволок, из которых состоит повив k кабеля, а последовательно включенные комплексные сопротивления

Г-образных четырехполюсников учитывают индуктивную связь между соседними повивами проволок кабеля, при этом, в формуле (1) влияние соленоидов, образованных повивами с протекающими в них импульсными токами, на магнитное поле во внутренней области кабеля считают независимым друг от друга и влиянием индуктивной связи между повивами пренебрегают. Полное эквивалентное сопротивление электрической схемы замещения повивов проволок кабеля с учетом взаимной индуктивной связи смежных повивов выражается лестничной дробью:Formula

(1) is a simplified expression for the equivalent conductivity of an equivalent circuitry for layering wire wires. The electrical circuit is a serial connection n quadrupoles (Fig. 1A, Fig. 1B), according to the number of windings of the cable wires, where each curl k in the cable is described by a L-shaped quadrupole 2, in which each of the parallel-connected complex resistances

L-shaped quadrupoles represent the impedance of the turns of the wires that make up the curled cable k, and the series resistances connected in series

L-shaped quadrupoles take into account the inductive coupling between adjacent layers of cable wires, while in formula (1) the influence of solenoids formed by layers with pulsed currents flowing through them on the magnetic field in the internal area of the cable is considered independent of each other and the effect of inductive coupling between swelling neglected. Full equivalent resistance of the electric circuit of replacing the layers of the cable wires, taking into account the mutual inductive coupling of the adjacent layers, is expressed by ladder fraction:

(4)

(four)

- представляют собой погонные комплексные электрические сопротивления схемы замещения повивов кабеля ;Where:

- represent the linear complex electrical resistance equivalent circuit of cable layers;

- полное эквивалентное сопротивление схемы замещения повивов проволок кабеля;

- total equivalent resistance of the equivalent circuit of wire stitches;

- сопротивление замещения k-го повива проволок кабеля;

- replacement resistance of the k- th wire of the cable;

- сопротивление связи k-го повива проволок кабеля с повивом k-1,

- the resistance of the connection of the k-th dressing wire cable with lay-down k-1,

n - the number of povivov wires in the cable;

= jωL _k , L _{k 1} = µ ₀ m _k ² F _{k 1} ; L _{k 2} = µ ₀ m _k ² F _{k 2} , L _k = L _{k 1} +L _{k 2,}

= jωL _k , L _{k 1} = µ ₀ m _k ² F _{k 1} ; L _{k 2} = µ ₀ m _k ² F _{k 2} , L _k = L _{k 1} + L _{k 2,}

where is l _k  - the inductance of the connection of the k-th layer of wire cable with a lay-up k-1 total,

L _{k one,} L _{k 2}  - coupling inductance of the k-th lay-up of the wire cable with a lay-up k-1 for wires, where the index is 1 for wires from material A, for example, from steel clad with aluminum, and index 2 for wires from material B, for example, from an aluminum alloy;

F _{k one} F _{k 2} - cross-sectional area betweenk-m povivom wire and crotchk-1 for materials A and B, respectively;

for k = 1 , the values are the values of the connection of the first layer of wires with the central tube, the cross-sectional areas represent the areas between the first layer and the central tube.

;

;

;

;

;

;

Where:

- сопротивление замещения k-го повива проволок кабеля для материалов А и В;

- replacement resistance of the k- th layer of cable wires for materials A and B;

- импеданс витка проволоки k-го повива проволок кабеля для материалов А и В;

- impedance of a wire coil of the k- th layer of cable wires for materials A and B;

- внешняя индуктивность витка проволоки k-го повива проволок кабеля для материалов А и В;

- external inductance of a wire coil of the k- th layer of cable wire for materials A and B;

- количество витков на единицу длины проволоки k-го повива проволок кабеля;

- the number of turns per unit length of the wire of the k- th wire of the cable;

- периметр витка проволоки k-го повива проволок кабеля для материалов А и В;

- perimeter of a wire coil of the k- th layer of cable wires for materials A and B;

- диаметр проволоки k-го повива проволок кабеля для материалов А и В;

- wire diameter of the k- th layer of cable wire for materials A and B;

- расстояние между соседними проволоками k-го повива проволок кабеля из материалов А и В;

- the distance between adjacent wires of the k- th layer of cable wires of materials A and B;

- удельное сопротивление материалов А и В проволок кабеля;

- resistivity of materials A and B cable wires;

- эквивалентная глубина проникновения для материалов А и В проволок кабеля;

- equivalent penetration depth for materials A and B cable wires;

µ _0, µ _1, µ ₂ - absolute and relative magnetic permeability for materials A and B wire cables, respectively;

ω is the circular frequency of the alternating electric current.

The condition for achieving the minimum of the field is expressed in the minimum value of the equivalent resistance of the electric circuit for replacing the layers of the cable wires:

,

,

which corresponds to the mutual compensation of oppositely directed replacement currents in parallel branches of the equivalent circuit.

Description of preferred embodiments of the invention

According to the first embodiment of the invention, the optical cable 3 (FIG. 2) in the ground wire minimizing the longitudinal magnetic field generated in the area of the optical fiber during the passage of the current pulse in the ground wire contains the central tube 4 with optical fibers 5 located inside it.

On the central tube 4 there are at least two layers of 6 and 7 wires made of metal and / or composite materials. The layers 6 and 7 are arranged so that the cable 3 is provided with an alternation of the direction of twisting of the adjacent layers 6 and 7, i.e. clockwise and counterclockwise.

The wires used in metallic coatings contain metallic steel wire 8 having a protective anticorrosion coating and aluminum alloy wire 9.

In order to improve the properties of the cable, wires from composite materials, for example, with microfibers from aluminum oxide in the composition of aluminum wire, can be used to increase its strength characteristics.

The combination of materials A and B wires 8 and 9 in windings 6 and 7, the design parameters of the wires and the steps of twisting the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings 6, 7 is minimal for a given set of design parameters of the windings and material properties:

, (1)

, (one)

where: n - the number of windings wires;

k - number of dressing;

- составляющая продольного магнитного поля k-ого повива;

- component of the longitudinal magnetic field of the k-th layer;

- сопротивление электрической схемы Z _{c 1} , Z _{l 1} (фиг. 1) замещения для k-го повива оптического кабеля в грозозащитном тросе при прохождении импульса тока в грозозащитном тросе, зависящее от конструктивных параметров повивов, включающих диаметр ʺdʺ провода, шаг скрутки и диаметр ʺDʺ повива, и физических свойств материалов А и В проволок, включающих электропроводность и магнитную проницаемость материала k-го повива проволок;

- resistance of the electrical circuit Z _{c 1} , Z _{l 1} (Fig. 1) of the replacement for the k-th optical fiber cable in the ground wire during the passage of a current pulse in the ground wire depending on the design parameters of the windings, including the diameter ʺ d ʺ of the wire, the twist spacing and diameter ʺDʺ poviva, and the physical properties of the materials A and B of the wires, including the conductivity and magnetic permeability of the material of the k -th sheet of wires;

m _k - the multiplicity step of twisting the k-th dressing wire,

m _k = h _k / D _k ,

h _k - the twist pitch of the k-th layer of wires,

D _k - the diameter of the circle described around the k-th dressing wire.

представляет собой импеданс витков проволок 8 и 9, из которых состоит k-й повив кабеля, а последовательно включенные комплексные сопротивления Г-образных звеньев учитывают индуктивную связь между соседними повивами 6 и 7 кабеля.As indicated above, the technical solution is based on the cable replacement electric circuit, which is a cascade connection of n quadrupoles according to the number of strands of the optical cable, where each twisted wire in the optical cable 3 is described by a L-shaped quadrupole, in which each of the parallel-connected complex resistances G -shaped links

represents the impedance of the turns of the wires 8 and 9, of which the k -th winding of the cable consists, and the series-connected complex resistances of the l-shaped links take into account the inductive coupling between the adjacent layers 6 and 7 of the cable.

Wire 8 and 9 of metal and composite materials have different electrical conductivity.

The central tube 4, in which the optical fibers 5 are placed, is made of metal and ensures the tightness of the optical fibers 5.

The function of the central sealed metal tube 4 is to protect the optical fibers 5 from environmental factors, steel wires 8 clad with aluminum resist the mechanical tensile load, and aluminum alloy wires 9 are electrical conductors that transport lightning-induced currents from the point of impact to the ground point.

According to the second embodiment of the invention, the optical cable in the ground wire 10 (FIG. 3), which minimizes the longitudinal magnetic field generated in the location area of the optical fiber during the passage of a current pulse in the ground wire, contains a central element 11, which in the described embodiment is designed as a wire , and at least three layers 12, 13, 14 of wires from metal or composite materials placed on the central element 11. In the described embodiment, the central element 11 is made in wire form. The cable 10 also provides the alternation of the direction of twisting of the adjacent stitches 12, 13, 14 wires.

In the embodiment shown in FIG. 3, the optical cable 10 contains two tubes 15 with optical fibers 16 placed in one layer 12 adjacent to the central element 11. At the same time, the number of layers external to the sheet 12 containing tubes 15 with optical fibers and most distant from the central element 11 is equal to two.

The wires made of metallic materials used in the windings 12, 13, 14 contain steel wire 17, which has a protective anti-corrosion coating, and wire 18, made of aluminum alloy.

It is allowed to use wires from composite materials, for example, with microfibers from aluminum oxide in the composition of aluminum wire, in order to increase its strength characteristics.

The combination of materials A and B wires in the windings 12, 13, 14, the design parameters of the wires and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings, is minimal for a given set of design parameters of the windings and material properties:

, (2)

, (2)

where: n - the number of windings wires;

k - number of dressing;

- составляющая продольного магнитного поля k-ого повива;

- component of the longitudinal magnetic field of the k-th layer;

- сопротивление электрической схемы замещения для k-го повива при прохождении импульса тока, обусловленного внешним воздействием, зависящее от конструктивных параметров повивов, включающих диаметр ʺdʺ провода, шаг скрутки и диаметр ʺD повива, и физических свойств, включающих электропроводность и магнитную проницаемость, материала k-го повива проволок;

- resistance of the electrical equivalent circuit for the k-th layer during the passage of a current pulse caused by an external influence, depending on the design parameters of the layers, including the diameter ʺ d ʺ of the wire, twist pitch and diameter D of the layer, and physical properties, including electrical conductivity and magnetic permeability, of material k goviva wires;

m _k - the multiplicity step of twisting the k-th dressing wire,

m _k = h _k / D _k ,

h _k - the twist pitch of the k-th layer of wires,

D _k - the diameter of the circle described around the k-th dressing wire,

1 / Z _k = 0 for the k-th layer of wires having at least one tube with optical fibers placed in this layer.

Wire from metal and / or composite materials also have different electrical conductivity.

FIG. 4 shows a variant of an optical cable 19 in a ground wire that contains a central element 20 in the form of a hollow tube and four layers 21, 22, 23 and 24 wires of metal and / or composite materials placed on the central element 20. Cable 19 also provides alternation orientation of adjacent layers 21, 22, 23 and 24 wires and the indicated layers are multidirectional.

In the embodiment shown in FIG. 4, the optical cable 19 contains two tubes 25 with optical fibers placed in one layer 21 adjacent to the central element 20. Additionally, cable 19 contains four tubes 26 with optical fibers placed in layer 22. In this case, the number of layers external to winding 22, containing the tube 26 with optical fibers, and the most distant from the central element 20, is equal to two.

According to the third embodiment of the invention (FIG. 5), the optical cable 27 in the ground wire, minimizing the longitudinal magnetic field generated in the area of the optical fiber during the passage of a current pulse in the ground wire, contains a central element 28 in the form of a tube with optical fibers and at least at least three layers 29, 30, 31 wires from metal and / or composite materials placed on the central element 28.

The cable 27 contains at least one tube with optical fibers, placed in one of the layers of the wires, in the described embodiment, the cable 27 contains two tubes 32 with optical fibers, placed in the layer 29 adjacent to the central element 28.

In this case, the optical cable 27 provides the alternation of the direction of twisting of the adjacent layers 29, 30, 31 wires. The number of layers external to the layer 29, containing tubes 32 with optical fibers, was two.

The metal wires used in the coatings contain steel wire 33, which has a protective anti-corrosion coating, and aluminum alloy wire 34.

The use of wires made of composite materials.

The combination of materials A and B wires 33 and 34 in the windings, the design parameters of the wires and the steps of twisting the windings are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings is minimal for a given set of design parameters of windings and material properties:

, (3)

, (3)

Where:

n is the number of windings wire;

k - number of dressing;

- составляющая продольного магнитного поля k-ого повива;

- component of the longitudinal magnetic field of the k-th layer;

- сопротивление электрической схемы замещения для k-го повива при прохождении импульса тока, обусловленного внешним воздействием, зависящее от конструктивных параметров повивов, включающих диаметр ʺdʺ провода, шаг скрутки и диаметр ʺD повива, и физических свойств, включающих электропроводность и магнитную проницаемость, материала k-го повива проволок;

- resistance of the electrical equivalent circuit for the k-th layer during the passage of a current pulse caused by an external influence, depending on the design parameters of the layers, including the diameter ʺ d ʺ of the wire, twist pitch and diameter D of the layer, and physical properties, including electrical conductivity and magnetic permeability, of material k goviva wires;

m _k - the multiplicity step of twisting the k-th dressing wire,

m _k = h _k / D _k ,

h _k - the twist pitch of the k-th layer of wires,

D _k - the diameter of the circle described around the k-th dressing wire,

1 / Z _k = 0 for the k-th layer of wires having at least one tube with optical fibers placed in this layer.

The wires of metal and / or composite materials A and B have different electrical conductivity.

In poviv of a wire from metal materials contain the steel wire having a protective anticorrosive covering, and a wire from an aluminum alloy.

The use of wires made of composite materials.

Testing of the structures of the optical cable built into the ground wire against the effects of impulse currents simulating the effects of lightning

The impact of lightning currents in addition to the well-known thermal effect on the cable elements leads to the generation of a pulsed magnetic field inside an optical cable, consisting in the case of a straight-line cable from a longitudinal (axial) component.

As indicated above, recent studies and information provided by telecom operators indicate that a rapidly changing longitudinal magnetic field adversely affects the transmission of information over a fiber using a compression format based on light polarizations. The cause of the problem is the rapid rotation of the axis of polarization of light in the fiber under the influence of a changing magnetic field parallel to the axis of the fiber, in accordance with the Faraday law.

Since the picture of the magnetic field in the center of the optical cable is determined by its design, in which each layer behaves like a solenoid, the selection of wire parameters in the layers and the alternation of wire stranding directions significantly reduces the amplitude of the pulsed magnetic field with a corresponding attenuation of the lightning effect on the optical signal transmission.

The purpose of the test is to compare the change in the angles of rotation of the polarization of light in optical fibers under the influence of pulsed currents in one- and two-beam designs of an optical cable, where adjacent layers have opposite twisting directions.

Installation Description

The functional diagram of the installation 35 is shown in FIG. 6. Installation 35 consists of a segment 36 of the optical cable, the optical fibers of which are connected in block 37 optical connection in the ring. In block 37, a continuous optical signal from the optical radiation source 38 is supplied to the optical fibers of the cable 36, the phase of the optical signal at the cable output is estimated by the optical signal polarization analyzer 39, also connected to the cable through the optical connection unit 37.

A pulse discharge current from the pulse current source 41 is supplied to the layers of the optical cable section 36 through terminals 40. Under the action of a pulsed discharge current imitating a lightning current, the polarization axis of the optical signal in the cable 36 is rotated; this rotation is determined by the optical signal polarization analyzer 39.

Two cable samples 36 having different designs were tested and the test results were compared.

Installation 35 (Fig. 7) contains supports 42, 43, 44, 45 for mounting optical cables in a ground wire in a suspended state. On these supports are placed two samples 46 and 47 of optical cables in ground wire, with sample 46 being a single cable and placed on supports 42, 44, and sample 47 being a two-cable placed on supports 43, 45.

Cables 46, 47 are suspended using rocker arms 48, 49, respectively, using insulators 50, 51 and spiral clamps 52, 53, respectively.

Each sample 46, 47 is suspended between the respective supports 42, 44 and 43, 45 using standard coupling and spiral fittings in two "threads", so that both ends of each sample 46 and 47 of the cable are connected to the test bench 54. The distance between the supports 42 and 44, as well as 43 and 45 is about 50 m, and, as indicated, the cables 46, 47 are insulated from the supports using insulators 50, 51, respectively. Optical fibers containing twelve single-mode fibers of the G.652 standard in each of samples 46, 47 are connected by welding into a ring and form a continuous optical line about 1.2 km long.

The test bench 54 contains a pulse current source 41, an optical radiation source 38 at a wavelength of λ = 1550 nm (EXFO FOT600) and an optical signal polarization analyzer 39 (Keysight N7781B). The pulse current source 41 contains a power source 55, a capacitor 56 connected through the thyristor 57 during the tests either to the single layer cable 46, or to the external double sheet cable 47 (not shown). The capacitor 56 is also connected with a voltmeter 58.

The installation works as follows.

The optical signal is fed into the optical fibers of the cable 46 or 47 from the output of the source 38 of optical radiation.

An electrical impulse is generated by a source of 41 pulsed current, i.e. capacitor 56 (0.1F x 50V), and through the thyristor 57 is applied to terminal 40 to the layers of the optical cable. An electric pulse passes through the fabric of the optical cable 46 or 47. The discharge current is controlled by a stepwise series connection of a set of resistances 59 from 0.1 Ohm to 1 Ohm. The shape of the electrical pulse (Fig. 8) is controlled by a digital oscilloscope 60 with a display 61 of the voltage drop across the series-connected resistances 59.

Depending on the size of the series-connected resistances 59, the front of the current pulse has a duration of 0.8-1.7 ms.

Since for the operation of the optical signal transmission system the rate of change of the polarization state is important, its behavior on the front part of the current pulse, where the changes are most rapid, is of most interest.

A display 62 is connected to the analyzer 39 for polarizing optical signals.

Test results

As indicated above, the tests were carried out on two samples 46, 47. Both cable samples 46, 47 contain optical fibers of the G.652 standard, placed in a steel tube and welded in a ring.

Sample Description

Sample 46 Single Cable

The direction of the left side (counterclockwise), central steel tube, with a diameter of 3.2 mm, around six wires with a diameter of 3 mm of steel clad with aluminum. The diameter of the sheet is 9.2 mm, the twist pitch is 90 mm, the length of the optical fiber in the cable sample, according to optical reflectometry, is 1.186 km.

Sample 47 dual cable

The 1st winding left (counterclockwise), the same as that of the single-coat one, the second winding right (clockwise) contains twelve wires with a diameter of 3 mm. The outer diameter of the sheet is 15.2 mm, the twist pitch is 160 mm, the length of the optical fiber in the cable sample, according to optical reflectometry, is 1.172 km.

The number of rounds external to the central tube with optical fibers is two.

.Structural parameters of stitches, including the wire diameter, twist pitch and outer plate diameter, constituting 15.2 mm, as well as the physical properties of the wire material, including the electrical conductivity and magnetic permeability of the material of the k- th wire, are selected so that

.

Results

Sample Single Cable

The magnitude of the current pulse is 83 A. In FIG. 10 shows the normalized Stokes components S1, S2, S3, and FIG. 9 shows the trace F1 on the Poincaré sphere during the duration of the pulse.

The angle of rotation of the polarization axis Δϕ is proportional to the length of the trace on the Poincare sphere in the plane of the coordinates S ₁ and S ₂ and is:

,

,

where: ϕ _n and ϕ _to - the initial and final position of the angle of rotation of the polarization axis at the initial and final points of time of external influence.

When taking into account changes in the phase rotation of the optical signal during the action of the front of the electric current pulse (Fig. 8),

S _1N = -0.453; S _2N = -0.185; S _1k = -0.252; S _2k = -0.718; we get Δϕ ₁ = 0.43 happy = 24.2

Sample double-ply cable.

The magnitude of the current pulse is 91 A. In FIG. Figure 11 shows the trace F2 on the Poincaré sphere for the duration of the current pulse.

It can be seen that the F2 trace on the Poincare sphere for the second two-sample sample 47 is much shorter than the F1 track on the Poincare sphere for the first single-sample sample 46, which indicates a smaller angle of rotation of the polarization plane of the optical signal of the two-pole cable. The points H1 and H2 on the curves F1 (FIG. 9) and F2 (FIG. 10) show the final state of the polarization parameters of the signal at the end of the pulse. The values of the Stokes parameters S1, S2, S3 are shown in Fig.9 and Fig.10 in the upper right corner. When taking into account changes in the phase rotation during the pulse front, using the last set of formulas to calculate the phase change of the optical signal, taking into account S _1n = 0.675; S _2N = -0.401; S _1k = 0.556; S _2k = -0.406; we obtain the angle of rotation of the polarization axis Δϕ ₂ = 0.047 rad = 2.7 °. That is, the angle of rotation of the polarization axis Δϕ for a two-ply cable with respect to a single-coil is less by about 9 times.

Conclusion

Thus, it can be seen that at approximately the same impact of the actual pulsed current and at the same input signal power, the angle of rotation of the polarization plane of the optical signal for the two-cable cable design is much smaller than for the single-felted one, which is explained by the mutually compensating action of the strands having different directions of twist on the magnitude of the magnetic field inside the windings, as well as the structural parameters of the windings, including the wire diameter, the twist pitch and the diameter of the external winding, physical properties of the wire material, including electrical conductivity and magnetic permeability material.

Industrial Applicability

An optical cable in a ground wire can be effectively used to protect optical communication systems on overhead power lines during lightning strikes.

Claims (58)

1. Optical cable in the ground wire to minimize the longitudinal magnetic field generated in the area of the optical fiber during the passage of the current pulse in the ground wire containing: central tube with optical fibers located inside it, at least two layers of metal and / or composite materials placed on the central tube so that the cable provides alternation of the direction of twisting of the adjacent layers of the wire, at the same time, the combination of wire materials in the strands, the design parameters of the wires, and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings, is minimal for a given set of design parameters of the windings and material properties:

, (one) where n is the number of windings wire; k - number of dressing;

- component of the longitudinal magnetic field of the k-th curve;

- resistance of the electrical equivalent circuit for the k-th fiber sheet of the optical cable in the ground wire during the passage of a current pulse in the ground wire depending on the design parameters of the layers, including the wire diameter, twist pitch and the diameter of the sheet, and the physical properties of the wire materials, including electrical conductivity and magnetic permeability material of the k- th layer; m _k - the multiplicity step of twisting the k-th dressing wire, m _k = h _k / D _k , h _k - the twist pitch of the k-th layer of wires, D _k - the diameter of the circle described around the k-th dressing wire. 2. Optical cable in ground wire according to claim 1, in which wires made of metal and / or composite materials have different electrical conductivity. 3. Optical cable in ground wire according to claim 1, in which the wires used in the metal filaments contain steel wire having a protective anti-corrosion coating and aluminum alloy wire. 4. Optical cable in ground wire according to claim 3, in which the steel wires used in the coatings, having a protective anticorrosion coating, are made of steel, clad with aluminum. 5. The optical cable in the ground wire of claim 1, in which the central tube in which the optical fibers are placed, is made of metal. 6. Optical cable in the ground wire to minimize the longitudinal magnetic field generated in the area of the optical fiber during the passage of a current pulse in the ground wire containing: central element in the form of wire or hollow tube at least three poviv wires from metal and / or composite materials placed on the central element, so that the specified cable provides alternation of the direction of twisting of adjacent poviv wires, at least one tube with optical fibers placed in one of the layers of the wires, the optical cable contains so many windings that the number of windings external to the winding containing the tube / tubes with optical fibers and furthest from the central element is two, at the same time, the combination of wire materials in the strands, the design parameters of the wires, and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings, is minimal for a given set of design parameters of the windings and material properties:

, (2) where n is the number of windings wire; k - number of dressing;

- component of the longitudinal magnetic field of the k-th curve;

- resistance of the electrical equivalent circuit for the k-th layer during the passage of a current pulse due to an external influence, depending on the design parameters of the layers, including the wire diameter, twist pitch and the diameter of the sheet, and physical properties, including electrical conductivity and magnetic permeability, of the k- th sheet material wire; m _k - the multiplicity step of twisting the k-th dressing wire, m _k = h _k / D _k , h _k - the twist pitch of the k-th layer of wires, D _k - the diameter of the circle described around the k-th dressing wire, 1 / Z _k = 0 for the k-th layer of wires having at least one tube with optical fibers placed in this layer. 7. Optical cable in ground wire according to claim 6, in which the wires of metal and / or composite materials have different electrical conductivity. 8. Optical cable in ground wire according to claim 6, in which the wires used in the metal filaments contain steel wire having a protective anti-corrosion coating and aluminum alloy wire. 9. The optical cable in the ground wire of claim 8, in which the steel wires used in the coatings, which have a protective anti-corrosion coating, are made of steel clad with aluminum. 10. Optical cable in ground wire according to claim 6, which further comprises at least one tube with optical fibers, placed in another of the strands of wires, at the same time, the optical cable contains so many windings that the number of windings external to the winding, containing a tube / tubes with optical fibers and furthest from the central element, equals two. 11. Optical cable in the ground wire to minimize the longitudinal magnetic field generated in the area of the optical fiber during the passage of a current pulse in the ground wire containing: central element in the form of a tube with optical fibers, at least three poviv wires from metal and / or composite materials placed on the central element, at least one tube with optical fibers placed in one of the layers of the wires, while in the optical cable is provided by the alternation of the direction of twisting of the adjacent layers of the wire (clockwise or against it), the cable contains so many windings that the number of windings external to the winding containing the tube with optical fibers is equal to two, at the same time, the combination of wire materials in the strands, the design parameters of the wires, and the twisting steps of the layers are chosen so that the modulus of the sum | Σ | electrical conductivities corresponding to the components of the formed magnetic field in each of the windings, is minimal for a given set of design parameters of the windings and material properties:

, (3) where n is the number of windings wire; k - number of dressing;

- component of the longitudinal magnetic field of the k-th curve;

- resistance of the electrical equivalent circuit for the k-th layer during the passage of a current pulse due to an external influence, depending on the design parameters of the layers, including the wire diameter, twist pitch and the diameter of the sheet, and physical properties, including electrical conductivity and magnetic permeability, of the k- th sheet material wire; m _k - the multiplicity step of twisting the k-th dressing wire, m _k = h _k / D _k , h _k - the twist pitch of the k-th layer of wires, D _k - the diameter of the circle described around the k-th dressing wire, 1 / Z _k = 0 for the k-th layer of wires having at least one tube with optical fibers placed in this layer. 12. Optical cable in ground wire according to claim 11, in which wires made of metal and / or composite materials have different electrical conductivity. 13. Optical cable in ground wire according to claim 11, in which the wires used in the metal filaments contain steel wire having a protective anti-corrosion coating and aluminum alloy wire. 14. The optical cable in the ground wire of claim 13, in which the steel wires used in the coatings, which have a protective anticorrosion coating, are made of steel clad with aluminum.

Images