JPS63290023A - Method for transmitting power transmission-distribution line information - Google Patents

Abstract

PURPOSE:To lower a used carrier frequency, and to reduce a radio wave radiation from a power transmission distribution line, and at the same time, to reduce the cost of an equipment since a coupling capacitor is eliminated and voltage resistance is not necessitated as well by supplying a signal current in a non-resonant state to a coupling line installed separately from the power transmission distribution line and in parallel with it. CONSTITUTION:A signal line 4 allows the signal current I1 to flow through a closed circuit consisting of an overhead each wire 1 - a steel tower 2A - the earth 5 - the steel tower 2. Since a power transmission line 3 is installed in parallel with the overhead earth wire 1, an electromagnetic coupling is generated between both, and a signal voltage V2 and a transmission current I2 are induced on the power transmission line 3 by the signal current I1 and they are propagated along the power transmission line 3. At a receiving point, an induced current induced inversely on the overhead earth wire 1 by the transmission current I2 on the power transmission line 3, is detected by the current transformer 11 and is regenerated by a receiver 12. Thus, since the frequency of an electric signal propagating on the power transmission distribution line can be extremely lowered and the radio wave radiation can be reduced and at the same time, the coupling capacitor can be omitted, and the voltage resistance is not necessitated as well, the cost can be reduced, and a constitution and a maintenance can be simplified.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for transmitting information on power transmission and distribution lines, and in particular, the present invention relates to a method for transmitting information on power transmission and distribution lines, and in particular, it utilizes mutual inductive coupling between coupling lines and power transmission and distribution lines to transmit various electrical signals ( The present invention relates to a power transmission/distribution line information transmission method for propagating and transmitting information (information) on power transmission/distribution lines.

(Prior Art) Recently, there has been a growing demand for transmitting information along power transmission and distribution lines (signals from faulty section detectors, information on flash flashes caused by lightning, etc.) to maintenance staff stations in as short a time as possible.

In order to meet this demand, communication cables, 0P
Transmission systems using GW (overhead ground wire embedded in optical cables), optical cables, etc. are being adopted.

However, since these transmission systems are expensive, it has been considered to use already installed power transmission and distribution lines as transmission paths for the information.

The use of high-voltage power transmission and distribution lines as information transmission paths to transmit electrical signals on carrier waves has been widely known as the power line transport method. In that case, it is necessary to couple a carrier wave modulated with an electrical signal to a power transmission/distribution line, or to take out a modulated carrier wave from a power transmission/distribution line.

For this purpose, a capacitor coupling method and a distributed coupling (or antenna) method have been proposed.

In the capacitor coupling method, a modulated carrier wave is directly coupled and injected into a high voltage line via a capacitor.

On the other hand, the distributed coupling method connects the modulated carrier wave to a coupling line installed separately from the 7U power line, such as an overhead line installed in parallel with the power line, and resonates when the tip is short-circuited or the tip is open. The power line is coupled to the coupling line in a distributed manner.

Furthermore, the modulated carrier wave transmitted via the power line is extracted using the same configuration as described above, but in a procedure reverse to that described above.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

In the power line carrier method, the higher the frequency of the carrier wave, the better the transmission characteristics.
The KH2 frequency band was used.

However, recently, restrictions on radio wave radiation emitted from power transmission and distribution lines have become stricter, and on the other hand, the lower the frequency, the smaller the radio wave radiation, so low carrier wave bands of about tens of KHz or less are often used.

In the case of such a low frequency band, not only the transmission characteristics deteriorate, but also the following problems occur.

(1) In the capacitor coupling method, the coupling capacitor is expensive and large.

(2) In distributed coupling, a resonant circuit is usually constructed between one span of a steel tower, so as the carrier frequency decreases,
Not only does the impedance (capacitance and inductance components) that must be added for resonance increase, but the length of the coupling wire that is placed parallel to the power line is approximately constant (i.e., approximately equal to the distance of one span of the steel tower, or (less than that), the degree of coupling deteriorates and the transmission efficiency decreases.

The present invention has been made to solve the above-mentioned problems.

(Means and operations for solving problem 1) In order to solve the above problem, the present invention electromagnetically couples the coupling line and the power transmission/distribution line not by distributed coupling but by mutual induction. , a closed circuit is formed by the coupled wire, the steel tower, and the ground, and by inserting a signal source (the electrical signal itself or a modulated carrier wave current source) into this closed circuit, a signal current is caused to flow through the coupled wire in a non-resonant state. It is characterized by the fact that it is

As a result, according to the present invention, the frequency of electrical signals propagating on power transmission and distribution lines can be significantly lowered to reduce radio wave radiation, and coupling capacitors can be omitted and withstand voltage is not required, resulting in cost reduction and configuration. Maintenance can be simplified. Furthermore, it becomes easy to add transmitting points and receiving points along the power transmission and distribution lines.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing the transmission line configuration of an embodiment of the present invention;
FIG. 2 is an equivalent circuit diagram for explaining its operation, and FIG. 3 is a diagram showing a specific example of the coupling circuit.

In FIG. 1, an overhead ground wire 1 and a power transmission line 3 are installed on steel towers 2.2A, . . . , 2N. In this figure, the overhead ground wire 1 is drawn below the power transmission line 3 to simplify the drawing, but in reality, the overhead ground wire 1 is installed above the power transmission line 3.

Furthermore, in this specification, the term "steel tower" does not literally mean that it is made of iron, but rather that it supports power lines such as power transmission lines and distribution lines, as well as overhead ground wires, and also supports itself or an appropriate ground wire. A utility pole that has the function of grounding an overhead ground wire through a support pole.

The signal source 4 is inserted between the overhead ground wire 1 and the steel tower 2 and supplies a signal current to the overhead ground wire 1. As shown in Figure 2,
Overhead ground wire 1 for signal source 4. Steel tower 2.2A and earth 5
are connected in series and form a closed circuit.

On the other hand, near the receiving point, a current transformer 1 for signal detection
1 or the overhead ground wire 1, and its detection output is supplied to the receiving device 12.

Note that the coupling capacitor 17 and the signal detector 18 may be provided at the receiving point instead of the current transformer 11 and the receiving device 12, and the coupling capacitor 17 connects the signal detector 18 directly to the power transmission line 3. It functions to capture the signal current flowing through the power transmission line 3 into the signal detector 18.

The signal source 4 outputs a modulated carrier wave obtained by modulating the electrical (information) signal itself to be transmitted or a carrier wave with a low frequency of, for example, 10 KHz or less, which does not cause a problem, with the electrical signal.

As is clear from the figure, this signal source 4 is connected to the overhead ground wire 1.
- A signal current 11 is passed through a closed circuit consisting of the steel tower 2A, the ground 5, and the steel tower 2.

Since the power transmission line 3 is installed parallel to the overhead ground wire 1,
An electromagnetic coupling occurs between the two, and a signal voltage 2 and a transmission current 12 are induced on the power transmission line 3 by the signal current generator, and these are propagated along the power transmission line 3. At the receiving point, an induced current (3) induced on the overhead ground wire 1 by the transmission current (2) on the power transmission line 3 is detected by the current transformer 11 and reproduced by the receiving device 12.

Alternatively, the transmission current I2 on the power transmission line 3 may be taken into the signal detector 18 via the coupling capacitor 17 and reproduced, or the signal current flowing to the neutral point of a transformer (not shown) may be detected. You can also.

An example of a coupling circuit device at a transmission point will be explained with reference to FIG.

The secondary winding of the coupling transformer 9 is connected to the overhead ground wire 1-tower 2A-
It is inserted in series into a closed circuit consisting of the ground 5 and the steel tower 2, and its primary winding is connected to the output end of the transmitter 10.

The shorting relay 8 is responsive to a control signal from the transmitter 10;
During the period when no transmission is being performed, 2 of the coupling transformer 9
The next winding is shorted and left open during transmission.

Therefore, during transmission, from the transmitter 10 to the coupling transformer 9
As a result, the signal current 11 is injected into the overhead ground wire 1 via
The overhead ground wire 1 also functions as a coupling wire, but during other periods, the secondary winding of the coupling transformer 9 is short-circuited, so the overhead ground wire 1 functions as a normal overhead ground wire.

In the transmission line configuration shown in Figure 1, The voltage of signal source 4 is The ground return impedance of the transmitting overhead ground wire 1 is Z.

s The current flowing through the transmission overhead ground wire 1 is 11, and the mutual impedance between the overhead ground wire 1 and the transmission line 3 at the transmission point is 21. gs The voltage induced in the transmission line 3 by the current I is v2. The self-impedance of the transmission line 3 is 21 The induced current flowing in the transmission line 3 at the transmission point is 12, the current attenuation constant between the transmission and reception points is α, and the ground return impedance of the overhead ground wire 1 at the reception point is gr. If the mutual impedance is 21 mgr, the signal current flowing in the transmission line 3 at the receiving point is 11r, and the signal current flowing in the overhead ground wire at the receiving point is 13, then I! ″″vo/Zgs・■2″″Zlig8×11・l2sllv2/Z8.

I String α x 1.

er e ■3″″ZI1grXI8. /Zgr, the current 13 induced in the overhead ground wire 1 at the receiving point can be expressed by the following equation.

1 −V Xα xZ xZ /(Z XZ, XZ
) IIIgs mgr c
By the way, as is well known, the overhead ground wire 1 has about 2 to 5% of the commercial frequency current flowing through the power transmission line 3 even in normal times due to mutual induction of the commercial frequency current flowing through the power transmission line 3. A current is induced to flow.

Most of its frequency components are the fundamental wave of the commercial frequency and its harmonics, and its spectrum is 3K, except in special cases.
It is distributed below Hz.

Therefore, it is desirable to use a carrier wave with a frequency of 3 KHz or higher in order to identify the signal current from this and improve the S/N ratio of transmission.

When there is one overhead ground wire 1, the ground return impedance of one tower section (for example, between 2 and 2A in Figure 1) is
, including the grounding resistance of 2A, is approximately 100Ω or less (however,
(in a frequency band of 10 KHz or less). In addition, in a three-phase, two-circuit transmission line system, if six power lines for two circuits installed in parallel are collectively regarded as one equivalent transmission line, this equivalent transmission line and the overhead ground wire The mutual impedance with 1 is 8 in the 5-6 KHz frequency band.
The value is approximately Ω/kpm.

Since the average length of one steel tower section is about 250 m, the mutual impedance of this section can be estimated to be about 2Ω. Therefore, the first. In FIG. 2, if a signal current 11 of IA is passed through the overhead ground wire 1, a signal voltage V2 of about IA×2Ω−2v will be induced in the power transmission line 3.

This signal voltage v2 is then transmitted via the power transmission line 3 toward the receiving point.

Further, in general, the power transmission line 3 is not a pure series of lines, but is branched in various directions at a substation, so that the signal voltage propagated on the power transmission line 3 is reflected at the branch point. Not only that, but the state of the branch also changes, so the frequency characteristics or transmission characteristics of the power transmission line 3 vary greatly.

A well-known spread spectrum communication method is suitable as a communication method that can be applied to a transmission path where the frequency characteristics vary significantly as described above.

As is well known, the spread spectrum communication method is a method in which the transmitting side spreads signal components over a wide band and transmits them, and the receiving side receives the spread signals all at once. (for example, satellite communications).

Among the spread spectrum communication methods, the ones particularly suitable for the present invention are (1) the Chilb method in which the carrier frequency is continuously changed within a predetermined range at each scheduled time interval, and (2) the Chilb method in which the carrier frequency is changed continuously within a scheduled range at each scheduled time interval. There is a hopping method that switches frequencies discontinuously.

Above, an example was described in which one transmitting point and one receiving point were provided along the overhead ground wire 1 and the power transmission line 3, but the receiving point may be located at multiple locations along the power transmission line 3. It goes without saying that the power transmission line 3 may be branched. Also,
Transmission points can also be installed at multiple locations.

Furthermore, the present invention can be applied not only to the above-mentioned power transmission lines but also to power distribution lines. Even in the case of power transmission and distribution lines that do not have overhead ground wires, a new overhead line is installed parallel to the power transmission and distribution lines and mutually inductively coupled with the power transmission and distribution lines, and a signal current or modulated carrier current is connected to this line. The present invention can be carried out by allowing the water to flow.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) Although the overhead ground wire is used as a coupling wire, since the resonance phenomenon is not utilized, the carrier frequency used can be lowered and radio wave radiation from the power transmission and distribution lines can be reduced.

(2) Since the signal voltage induced in the power transmission and distribution lines by inductive coupling propagates on the power transmission and distribution lines, it is possible not only to effectively utilize the low attenuation characteristics and structural stability of the power transmission and distribution lines, but also to use Since the carrier frequency can be lowered, the transmission characteristics are more stable than in the case of high frequencies, and changes due to weather are also reduced.

(3) Since no coupling capacitors or withstand voltages are required, equipment costs are reduced, and it is easy to add transmitting and receiving points in the middle of power transmission and distribution lines, further simplifying maintenance. I can do something.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the transmission line configuration of an embodiment of the present invention;
FIG. 2 is an equivalent circuit diagram for explaining its operation, and FIG. 3 is a diagram showing a specific example of the coupling circuit. 1... Overhead ground wire, 2.2A, 2N... Steel tower, 3...
・Power transmission line, 4...Signal source, 5...Earth, 9...Coupling transformer, 10...Transmitter, 12...Receiving device Patent attorney Michito Hiraki and 1 other person to correct the procedure (Spontaneous) April 2, 1988 1. Indication of the case Patent Application No. 124422/1982 2. Name of the invention Transmission and distribution line information transmission method 3. Person making the amendment Relationship to the case Patent applicant Nishim Electronics Industry Co., Ltd. Company 4, Agent 3-3-23 Nishi-Shinjuku, Shinjuku-ku, Tokyo 5. Subject of amendment 6. Contents of amendment (1) Next to "Transformer not shown" on page 9, line 10 of the specification (GPT) Add J. (2) On page 14, line 7, ``applicable...publicly known'' was amended to ``transmission of information has traditionally been technically difficult, but for example''. (3) In line 8 of the same page, ``The method is appropriate.'' has been amended to ``Advances in communication technology have made information transmission possible and practicality has increased.'' (4) Figures 1, 2, and Figure 3 has been corrected as shown in the attached sheet.

Claims (5)

[Claims] (1) A signal current is supplied in a non-resonant state to a coupled line constructed separately from and parallel to the power transmission/distribution line, and the signal current is supplied to the power transmission/distribution line by mutual induction between the power transmission/distribution line and the coupled line. A power transmission and distribution line information transmission method characterized by inducing a signal current and propagating this signal current on a power transmission and distribution line. (2) The power transmission/distribution line information transmission method according to claim 1, wherein the signal source that supplies the signal current to the bond line is inserted into a closed circuit that includes the bond line and the ground. (3) The power transmission/distribution line information transmission method according to claim 2, wherein the signal current is a modulated carrier current modulated by the information signal to be transmitted. (4) The power transmission/distribution line information transmission method according to claim 3, wherein the carrier wave has a frequency of about 10 KHz or less. (5) The power transmission and distribution line information transmission method according to claim 3, wherein the carrier wave has a frequency higher than the frequency of the current induced in the overhead ground wire by the commercial frequency current flowing in the power transmission and distribution line.