DE1153809B - Method for reducing the currents induced by an adjacent power line in the inner conductors of coaxial lines, in particular dwarf tubes, with remote direct current feed, which are arranged in telecommunication cables - Google Patents

Description

GERMAN

PATENT OFFICE

St 18006 Vmd / 21c

REGISTRATION DATE: JUNE 27, 1961

NOTICE THE REGISTRATION AND ISSUE OF THE EDITORIAL: SEPTEMBER 5, 1963

Very thin coaxial lines with an outer diameter of less than 5 mm, so-called Dwarf tubes, for the transmission of several hundred carrier frequency channels in telecommunication cables used. Such dwarf tubes are fed remotely at intervals of a few kilometers and therefore unmanned, e.g. B. submerged in the ground transistor intermediate amplifiers connected, so that it is sufficient that the to arrange manned main amplifier offices at large distances of about 60 km and more. The remote supply expediently takes place from the manned booster offices by means of direct current to the Inner conductors of the dwarf tubes, whereby the outer conductors remain insulated to avoid induction effects in the Circuits inner conductor — outer conductor as close as possible avoid. The inner conductors are switched through on the long stretches between the manned offices, and it can therefore not be avoided that through adjacent, in particular parallel power lines, especially in the case of Short circuits, in spite of the isolated outer conductors acting as shielding in the inner conductors, currents are induced, the size of which far exceeds the permissible level for such transistor circuits.

_{The invention consists in a method for reducing these currents with the characteristic that inductances (L e} ) with small effective resistances (R _e ) are distributed between the coaxial outer conductor and the metal outer sheath of the telecommunication cable at the feeding main amplifier offices or at as uniform intervals as possible over the entire cable route ) , the size of which results from the following equations:

^Le ~ tfCÜI '

^ ^4Q

where Q is the ratio of the currents for R _e
and R _e = 00.

A similar method has so far only been proposed for multi-core telecommunication cables with insulated metal outer sheaths to reduce the voltages in the wire bundle-cable sheath circuit. In contrast, only one other method is known for the selective interference suppression of concentric broadband cables influenced by high frequency transmitters with outer conductors isolated from earth, namely the connection of a network between methods for reducing the energy induced by an adjacent power line
Currents in the inner conductors of coaxial lines, especially dwarf tubes,

with remote direct current supply,
which are arranged in telecommunication cables

Applicant:

Standard Elektrik Lorenz Aktiengesellschaft, Stuttgart-Zuffenhausen

Dr.-Ing. Erwin Widl, Korntal (Württ.),
has been named as the inventor

Outer conductor and earth, with the help of which the interference between the outer conductor and earth caused by the source of interference Voltage itself is used to generate the compensation voltage which is opposite in phase.

The figures of the drawing are intended to better illustrate the invention.

Fig. 1 shows the connection of inductances at the end of a shown schematically only by lines Telecommunication cable with only one dwarf tube;

2 shows in the form of a three-dimensional sketch the case of a telecommunication cable with four dwarf tubes;

FIG. 3 shows, based on FIG. 1, the switching on of inductances at every second intermediate amplifier;

Finally, FIG. 4 shows the equivalent circuit diagram of a repeater point that is thus between two superadjacent repeater points existing partial four-pole.

Fig. 1 shows in detail, schematically, the distribution of the current induced in the inner conductor 1 of a dwarf tube by the power line 0, which is superimposed on the remote supply direct current and thereby endangers the amplifiers. The full current curve J ₁ relates to the case of the insulated outer conductor 2 without connected inductances and the dashed curve J _{1 to} the case with inductances shown as complex resistances R _e at the cable ends between the outer conductor 2 and the cable sheath 3. The case is shown here that the cable jacket

309 670/262

is isolated from earth E; however, this isolation is not absolutely necessary.

In the course of the inner conductor of the dwarf tube, whose

Length 2 -r- = 1, there is a large number of intermediate amplifiers T and a main amplifier H at each of their two ends. As a result of the current J ₀ flowing in the power line 0, the inner conductor is calculated at location x, from the middle of the route, the current / (x) generates. In the manned main dining amplifier offices H are the inductive resistors S between the outer conductor and the metal Kabemantel? _e = Ä _e -f- jojL _{e arranged} with the smallest possible effective resistance R _e , which according to the new method, with a suitable choice, cause a significant reduction in the current / {x) in the form indicated by the curve J _1.

To clarify the effectiveness of such a circuit, reference is made to the formula for the current / (x) for electrically short lines, where the line sizes belonging to the circuits are indicated by foot indices: For example, if you are dealing with a system in which for / = 50 Hz and with a main amplifier field length / = 60 km e.g. B. a kilometric capacity value

C ₂₃ = 0.1

is to be assumed, and the current ratio Q should not be greater than 0.01, which is tantamount to the fact that the induced current should be reduced to Vioo, so one calculates

L _e = 6.7 henry,
i? _e ^ 21.2 ohm.

Since there are often several, i.e. η dwarf tubes in the same cable, the outer conductors of which are in direct contact with each other, the ao above formulas for these are as follows:

L _e =

J (X) =

<s

5 ^4ß

23 '

1 · η

Xk

1 + 21

(1)

Since it is technical alternating current with frequencies from 16 ² Ia to 60 Hz, the assumption of electrically short lengths is justified.

The following applies to the inner conductor — outer conductor circuit approximated

Ul ₁₂ ^ R ₁₂ , © i2 f *> j. (O C _12. (2)

The following applies to the external conductor – cable sheath circuit approximated

3R ₂₃ SoA ₂₃ , © ₂₃ sa j ω C ₂₃ . (3)

r _K is the cable reduction factor of the inner conductor, t ₁₂ is the resulting reduction factor. In order to characterize the reducing effect, it is sufficient, This means that in this case the inductances reduced to the rc-th part are connected between the outer conductors, which are in direct contact with one another, and the metal cable sheath. If, for example, a four-tube cable is involved, as shown in Fig. 2, the following applies to dwarf tubes with the mathematical assumptions mentioned earlier:

Le = 1.68 henry,

R _e <5.3 ohms.

consider the ratio Q of the currents for St _e = 00:

J (*

C ₂ y

—J

In order to achieve the greatest possible reducing effect, one must choose:

u- ^4th

CO ² C ₂₃ / '

Re <

ω C ₂₃ /

The effective resistance of the inductance should, as emphasized again, be as small as possible. Even an approximation to the values of these formers would already have a significant reduction effect. It should also be pointed out that the same reduction effect can be achieved in the case of only partial or non-uniform influencing by the energy conduction by means of corresponding, non-uniformly selected inductances L _e.

The method according to the invention is true at; \ (oL _e and for ₅₀ telecommunication cables with dwarf tubes of particular interest and therefore shown in their example; however, it can also be used for coaxial cables with larger cross-sections, e.g. the 2.6 / 9.5- Tube.

Since there are many accessible intermediate amplifier points with thin coaxial lines, there is also the possibility of distributing the transverse inductances as evenly as possible along the entire length of the cable, thereby creating a kind of transverse winding. FIG. 3 shows such a case in which a shunt inductance L _q with the effective resistance i? ", Which is to be made as small as possible, is connected to every second intermediate amplifier point Tl... Tm between the outer conductor and the cable sheath. One then has to deal with m short sections of length s , to which all line sizes are to be related according to FIG. 4. If I is the total length, then m = Ils subsections are available, where in the present-

(5)

5 6

the case λ ^{1 is} the distance between two superadjacent repeaters. The following then applies: 3ΐι ..> sä s ■ R ₁₂ ,,

®i _a 1 Rs S ■ j co C ₁₂ ir 1 Co ₃ f j ω Lq = S ■ C ₂₃ , 'J CO IL ₂₃ CO ² Lo * e Rq - ( ■> ³ L _? ²

The group of equations then applies to the current J (χ):

2 1 4

"Γι 2, ~ 1 + St ''

81 '=

The ratio Q of the currents for iR _g = R _g + jcoL _s r = zjw L _a and 9t _ff = oo is here:

In order to achieve the greatest possible reducing effect, one must choose:

¹ η = ö

ω · ⁴ · C ₂₃ co · C ₂₃

The fact that the longitudinal distribution of the transverse inductances (transverse winding) also enables the method to be used for electrically long cable sections results from the generally applicable group of equations for the current / (x) :

J (x) ~ ^ΰ " ^Γ

cosh γί ₂

τη

cosh y ₂₃ · -— · coshyi2 · x - cosh γ ' _ν , · ----- · cosh ^ ₃ · χ

m,, m

If one puts in the bracket expression γ ₂₃ «a O, which is allowed if one not only fulfills the conditional equation (10) for L _q , but also the effective resistance R _q and the loss angle of the dielectric

If you choose as small as possible between the outer conductor and the cable sheath, the expression in brackets will be approximately zero regardless of χ.

In this case, it doesn't seem to matter whether it is be a uniform or an uneven, z. B. only partially influenced by the Energieleitung acts.

Claims (5)

PATENT CLAIMS: 55 1. A method for reducing the currents induced by an adjacent power line in the inner conductors of coaxial lines, in particular dwarf tubes, with direct current remote feed, which are arranged in telecommunication cables, characterized in that between the coaxial outer conductor and the metal outer sheath of the telecommunication cable at the feeding main amplifier offices or in Inductivities (L ₁ ,) with small effective resistances (R ₁ ) can be switched, the size of which results from the following equations: R ψ ω C ₂₃ / '(5) where Q is the ratio of the currents for 3l _e ^ ijcoL _e and di _e = co. 2. The method according to claim 1, characterized in that in the case of η coaxial lines, in particular dwarf tubes, the inductances reduced to the η-th part between the outer conductor in direct contact with one another and the metal cable jacket are connected according to the following equations: re C ₂ Jn 3. The method according to claim 1, characterized in that in the case of uniform Distances according to FIG. 3 distributed over the entire cable route inductivities their size 7 8 is determined according to the following equations: 4. The method according to claim 1 or 2, characterized ₁ characterized in that in the case of an arrangement of the L _g - ■ ■ £ -,, inductances in the main amplifier offices ^ω ^ ²³ an uneven influence by the 5 energy conduction the reduction effect through R ; p _ ^ L speaking unevenly chosen inductances ω Ci ₃ ' (19) is achieved. 1 sheet of drawings © 309 670/262 8.63