JPH07183836A - Coupling filter device for distribution line carrier communication - Google Patents

Abstract

PURPOSE:To easily perform a matching even when the line impedance of a distribution line changes and to obtain an optimum transmission characteristic in conformable to the status of a line at a site. CONSTITUTION:This device is provided with an insulating transformer 10 provided between one end of the secondary coil 4B of a transformer 4 and a serial capacitor 5, plural compensation capacitors 7A to 7C each having a prescribed capacitance and provided between the secondary coil 10B of the insulating transformer 10 and the secondary coil 4B of the transformer, and a switch means performing a switchover for changing the ratio of the number of turns of the primary coil 10A to that of the secondary coil 10B of the insulating transformer 10 and a switchover for changing a capacitance value by selecting one or more arbitrary capacitors from among the plural compensation capacitors 7A to 7C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coupling filter device for distribution line carrier communication, and more particularly, it enables easy matching even if the line impedance of the distribution line changes so that optimum transmission according to the line situation at the site. The present invention relates to a coupling filter device for distribution line carrier communication, which has characteristics.

[0002]

2. Description of the Related Art Recently, distribution line carrier communication using a distribution line such as a high voltage distribution line as a signal transmission line has been used for applications such as power supply control, system protection, and automatic meter reading of watt hour meters of consumers. It is widely used, and the most economical method is the rail-to-ground coupling method.

In the line-to-ground coupling method, a transceiver is coupled between a distribution line and the ground to transmit information, and as the transceiver, for example, a coupling filter device as shown in FIG. 5 is used.

This coupling filter device schematically shows a circuit on the transmission side, and comprises a transmission power supply 1 for outputting a carrier signal having an angular frequency ω and a transmission voltage E, an internal resistance 2, and an internal capacitance. A signal generating circuit composed of a primary winding 4A constituting a capacitor 3 and a transformer 4, a series capacitor 5 connected to a distribution line 6 and a series capacitor 5, and a transformer constituting a transformer 4 inserted between the two. The secondary winding 4B is provided with a coupling circuit, and the power supply circuit and the coupling circuit are coupled by the transformer 4 having a coupling coefficient k.

In such a combined filter device, it is necessary that the required characteristics of the filter are band pass type, large band gain, and flat. Therefore, the combined filter device must have a line impedance of the distribution line 6. It is designed by presetting each circuit constant so as to meet the above-mentioned conditions at the resonance angular frequency with respect to.

That is, the resistance value of the resistor 2 is R ₁ , the electrostatic capacity of the capacitor 3 is C ₁ , the inductance of the primary winding 4A is L ₁ , the inductance of the secondary winding 4B is L ₂ , and the coupling capacitor 5 is static. When the capacitance is C ₂ , the line impedance is R ₂ , and the resonance angular frequency with respect to the line impedance R ₀ at the time of impedance matching is ω ₀ , each constant relation for obtaining the matching characteristic in the above circuit is as follows.

[Equation 2]

[Equation 3]

[Equation 4] Q ₁ = Q ₂ (4) kQ = 1 (5), the coupling coefficient k is determined by the bandwidth, and is approximately 0.6 to 0.7 when the upper limit frequency / lower limit frequency = 2. The coupling capacitor 5 for high voltage distribution line is currently 0.0
Since 1 μF and 0.05 μF are standardized, if k is determined by the bandwidth from the above equation and ω ₀ and C ₂ are specified, from equations (5), (3) and (1),

[Equation 5] As a result, R ₂ is determined as, and the value of R ₂ other than this is out of conformity.

[0007]

However, according to the conventional coupling filter device for distribution line carrier communication, each circuit constant is preset so that the resonance angular frequency with respect to the line impedance of the distribution line meets the above condition. Therefore, there is an inconvenience that the line impedance is limited to a specific line impedance used at the time of setting, and the line impedance having other line impedance cannot be matched.

That is, a distribution line such as a high-voltage distribution line has a more complicated condition than a transmission line, and line branching, new installation, and modification are frequently performed. Therefore, the transmission characteristic of the line, that is, the line impedance. Changes drastically. Therefore, even if each circuit constant is set in advance according to the line impedance of the distribution line, impedance matching cannot be achieved when the line impedance changes.

FIG. 6 shows that in the circuit described in FIG. 5, line impedance R ₂ = mR ₀ and m is 0.1,
Line output power P (E ² / 4R when changed to 1, 10)
₁ ) G for normalized angular frequency (ω / ω ₀ ) in G
The characteristics are shown. As is clear from this, m = 1
Although the characteristic of is a matching characteristic and satisfies the required characteristic, it can be seen that when the line impedance changes significantly, its transmission characteristic deteriorates and becomes incompatible.

Therefore, an object of the present invention is to provide a coupling filter device for distribution line carrier communication which can easily achieve matching even when the line impedance of the distribution line changes and can obtain optimum transmission characteristics according to the line situation on site. Is to provide.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is capable of easily achieving matching even when the line impedance of a distribution line changes and obtaining an optimum transmission characteristic according to the line situation at the site. , Which is provided between one end of the secondary winding and the series capacitor, and between the secondary winding of the isolation transformer and the secondary winding of the transformer, and has a predetermined capacitance Switching for changing the number of turns of the plurality of compensation capacitors and the primary winding and the secondary winding of the insulation transformer, and switching for changing the capacitance value by selecting one or more arbitrary capacitors from the plurality of compensation capacitors The present invention provides a coupling filter device for distribution line carrier communication equipped with a switching means for carrying out the above.

The switching means is such that the capacitance of the series capacitor is C ₂ , the impedance of the distribution line at the time of impedance matching is R ₀ , and the capacitance of the selected one or more arbitrary capacitors is C _S. , When the line impedance of the distribution line changes to aR ₀ with a as a parameter,
If the winding ratio is

[Equation 6] In addition, the electrostatic capacitance C _S is switched so that the capacitance C _S is C _s = abC ₂ / (ab) with b as a constant.

The insulating transformer may have an autotransformer connected in parallel with its primary winding, in which case the switching means switches the tap of the autotransformer. It is preferable. Further, the series capacitor may be composed of three capacitors connected in parallel and connected to the three-phase distribution line.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A joint filter device for distribution line carrier communication according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a circuit structure of a coupling filter device according to an embodiment of the present invention. In this figure, the same parts as those in FIG. 5 are designated by the same reference numerals and symbols, and a duplicate description will be omitted.

This combined filter device is constructed by including a ground box 14 which houses a signal generating circuit and a switching circuit which are arranged with a transformer 4 interposed therebetween, and a pole box 15 which houses the coupling circuit.

In the ground box 14, a plurality of compensation capacitors 7A, 7B and 7C connected in parallel to one of the secondary windings 4B of the transformer 4 and having different capacitances, and these compensation capacitors 7A, 7B, 7C lead terminals 9A, 9B, 9
C, lead terminals 11A, 11B, 11C connected to the secondary winding of an insulation transformer described later, and lead terminals 9A, 9
B, 9C and lead terminals 11A, 11B, 11C are interlocked to switch the switching circuit composed of a switch 8 and a terminal 12 to which a voltmeter (not shown) is connected, respectively.
A, 12B, and 13A, 13B.

On the other hand, in the pole box 15, the series capacitor 5 and the primary winding 10A connected to the ground potential and the secondary winding 10B connected to the lead terminals 11A, 11B and 11C at predetermined tap positions are connected. It has an insulating transformer 10.

The changeover switch 8 has a capacitance C ₂ of the series capacitor 5 and an impedance R of the distribution line 6 when the distribution line 6 is matched.
₀ , the capacitance of the selected capacitor of the compensation capacitors 7A, 7B, 7C is C _s, and the line impedance of the distribution line 6 changes to aR ₀ with a as a parameter,
When the winding ratio of the primary winding 10A and the secondary winding 10B of the insulating transformer 10 is 1 for the primary winding 10A

[Equation 7] And the electrostatic capacitance C _s of the compensation capacitor 7
So that C _s = abC ₂ / (ab) with b as a constant, the lead terminals 11A, 11B, 11C and one or more of the lead terminals 9A, 9B, 9C are interlocked and cut. It is supposed to be replaced.

Here, each constant was set as follows. (1) f ₀ = 7 kHz (2) ω ₀ = 2π × 7 × 10 ³ = 44 × 10 ³ (3) k = 0.65 (4) b = 1 (5) C ₂ = 0.05 × 3 = 0.15 μF (6) R ₀ = 98.5Ω In this case, a, R ₂ , and
100% of the primary winding 10A of C _S and the insulation transformer 10
Table 1 shows numerical examples of the winding ratio β% of the secondary winding 10B in such a case.

[Table 1]

The terminals 12A, 12B and 13A,
13B is used when setting and operating in the best transmission state at each installation site, and in the case of the transmitting side shown in the figure, a voltmeter is connected between terminals 13A and 13B so that It suffices to switch the changeover switch 8 so as to obtain the maximum voltage. On the receiving side (not shown), a voltmeter is connected between the terminals 12A and 12B at a constant transmission signal level from the distribution line 6. It suffices to switch the changeover switch 8 so that the maximum voltage is obtained.

FIG. 2 shows an equivalent circuit of the coupling filter device of FIG. In this circuit, 7 is a compensation capacitor for switching the capacitance, 16 is a varying line impedance, and the line impedance can be represented by aR ₀ . That is, R ₀ is a constant value and a matching impedance value, and a is a parameter.
Corresponds to 1 <a <100 for m <10. Isolation transformer 10

[Equation 8] And the equivalent circuit as shown in FIG. 3 is formed.

That is, the variable line impedance 16
Becomes a constant value R ₀ , and the capacitance of the series capacitor 5 is a.
It becomes C ₂ . Here, the capacitance C _S of the compensation capacitor 7
And the combined capacitance C of the electrostatic capacitance aC ₂ of the series capacitor 5
_0, when C ₀ = bC ₂ as arbitrarily chosen constant b, the capacitance of the compensation capacitor _{7, C S = abc 2 / (} a-b) (7) where the a> b. Therefore, if the value of the electrostatic capacitance C _S of the compensation capacitor 7 is switched to the relationship of the expression (7) corresponding to a, the distribution line 6
Since the equivalent series capacitor bc ₂ with the inductance L ₂ of the secondary winding 4B of the transformer 4 becomes constant with respect to the change of the line impedance R ₂ of the above, corresponding to the equations (1) to (5),

[Equation 9]

[Equation 10]

[Equation 11] From Q ₁ = Q ₂ = Q (11) kQ = 1 (12)

[Equation 12] Then, b can be selected and R ₀ can be determined with respect to the designation of k, ω, and C ₂ .

In this way, when the line impedance of the distribution line 6 changes to aR ₀ with a as a parameter, the capacitance of the series capacitor 5 is C ₂ , the matching impedance of the distribution line 6 is R ₀ , and the compensation capacitors 77A, 7B. , 7C, where C _s is the capacitance of the selected one or more capacitors, the primary winding 10A and the secondary winding 10B of the isolation transformer 10.
Turns ratio

[Equation 13] And the electrostatic capacitance C _s of the compensation capacitor 7
Is switched by the changeover switch 8 so that C _s = abC ₂ / (ab) with b as a constant, it is possible to achieve matching with the line impedance on site and obtain optimum transmission characteristics. be able to.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, three-phase distribution lines 6R, 6S, 6T are used.
Is connected to the series capacitors 5A, 5B, and 5C to form a ground return circuit, and the autotransformer 17 connected to the secondary winding 10B of the insulating transformer 10 is connected to the ground box 1.
Installed in 4 and indirectly insulated transformer 1 at its tap
The winding ratio of 0 is switched by the changeover switch 8.

[0026]

As described above, according to the coupling filter device for distribution line carrier communication of the present invention, an insulating transformer provided between one end of the secondary winding of the transformer and the series capacitor,
A plurality of compensation capacitors provided between the secondary winding of the isolation transformer and the secondary winding of the transformer and having a predetermined capacitance;
And a switching means for switching the winding ratio of the primary winding and the secondary winding of the insulating transformer and switching the electrostatic capacitance value by selecting one or more arbitrary capacitors from the plurality of compensation capacitors. Therefore, even if the line impedance of the distribution line changes, matching can be easily achieved, and the optimum transmission characteristics according to the line situation can be obtained in the field.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is an equivalent circuit diagram of FIG.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a conventional coupling filter device for distribution line carrier communication.

FIG. 6 is a graph showing changes in transmission characteristics when line impedance changes in the conventional coupling filter device for distribution line carrier communication.

[Explanation of symbols]

1 Transmitting Power Supply 2 Internal Resistance 3 Capacitor 4 Transformer 4A Primary Winding 4B Secondary Winding 5 Series Capacitor 6 Distribution Line 7 (7A, 7B, 7C) Compensating Capacitor 8 Changeover Switch 9A, 9B,
9C Lead terminal 10 Insulation transformer 10A Primary winding 10B Secondary winding 11A, 11B, 11C Lead terminal 12A, 12B, 13A, 13B terminal 14 Ground box 15 Pillar box

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Yuichi Shimizu 1-3-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Co., Inc. Within Tokyo Electric Power Co., Inc.

Claims (3)

[Claims] 1. A distribution line carrier in which a primary winding of a transformer is connected to a transmission power supply, one end of the secondary winding is connected to a distribution line through a series capacitor, and the other end is connected to a ground potential. In a coupling filter device for communication, an insulating transformer provided between one end of a secondary winding of the transformer and the series capacitor, a secondary winding of the insulating transformer, and a secondary winding of the transformer. A plurality of compensating capacitors having a predetermined electrostatic capacity, switching for changing the turns ratio of the primary winding and the secondary winding of the insulating transformer, and one or more of the plurality of compensating capacitors. Switching means for selecting an arbitrary capacitor and changing the capacitance value is provided, wherein the switching means has capacitance C _{2 of} the series capacitor, impedance R _{0 of} the distribution line at the time of impedance matching, The one selected The capacitance of any capacitor above the C _S, when the line impedance of the distribution line is changed to aR ₀ to a as a parameter, the turns ratio is ## EQU1 ## In addition, the electrostatic capacitance C _S has a configuration in which switching is performed in conjunction with each other so that C _s = abC ₂ / (ab) with b as a constant. Combined filter device for distribution line carrier communication. 2. The isolation transformer has an autotransformer connected in parallel with its primary winding, and the series capacitor is composed of three capacitors connected to a three-phase distribution line. 3. The coupling filter device for distribution line carrier communication according to claim 1. 3. A signal generating circuit for generating a carrier signal having a predetermined carrier frequency, a switching circuit for coupling the signal generating circuit with a transformer having a predetermined coupling ratio to input the carrier signal, and the switching circuit. A coupling circuit having an insulating transformer for injecting the carrier signal input to the circuit into a distribution line through a series capacitor, and the switching circuit is configured to change the winding ratio of the primary winding and the secondary winding of the insulating transformer. And a capacitance value switching unit for changing the electrostatic capacitance value of the compensation capacitor, which is arranged inside the winding ratio switching unit, and the winding ratio switching unit, the signal generating circuit, the transformer, the switching circuit, When the line impedance of the distribution line that has been matched with the combined impedance of the coupling circuit and the series capacitor is changed by a certain change value from the matching value, the turns ratio cutoff is performed according to the change value. Means together with the changing the turns ratio, the capacitance value switching means the capacitance value distribution line carrier communication coupling filter apparatus characterized by being configured to implement impedance matching by changing the.