JPS6046900B2 - Signal transmission method using power lines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission system for transmitting various signals for measurement or control using power transmission lines as signal transmission paths.

Figure 1 shows one of the conventional signal transmission methods using power transmission lines.
As an example, in Figure 1, 1''6, J-W!
1. Equivalent circuit shown as a constant circuit above, 2 is a transmission signal receiver installed on the power transmission side, 3 is a transmission signal transmitter installed on the power reception side, and 4 is a transmission signal receiver installed on the power reception side. 5 is a power transmission line that is also used as a signal transmission path, TO is a transformer, P is
, P2 is a power receiving terminal for power from a power company or a private power generator, etc., P5 and P6 are power feeding terminals to the load 4 side via the transformer TO, P, , P are power receiving terminals on the load 4 side (power receiving side) It shows.

In addition, in the equivalent circuit 1 of the power transmission line 5, C2, Cs, C4
is the capacitance, R1, R2, and R3 are the insulation resistances, and in the receiver 2, Po is the signal ground signal receiving terminal, T2
is a signal relay transformer, Cl is a capacitor, P3 in the transmitter 3 is a signal ground signal sending terminal, Ti is a signal relay transformer, and Co is a capacitor. In each of the transformers TO, Ti, and T2, P indicates the primary side and S indicates the secondary side, respectively.

Normally, one wire of the power company's power transmission line connected to the power receiving terminals P, Po is grounded, but the power transmission line 5 is connected to the transformer T.
Both wires are insulated from the ground so that power is received through the wire.

However, as shown in equivalent circuit 1, it is usually impossible to escape that both wires are pseudo-grounded through a certain impedance. Electric power for operating the load 4 is supplied from an electric power company or the like to the power receiving terminals Pl and P2, interrupted by the transformer TO, and then supplied to the load 4 via the power transmission line 5.

．． :8 Also, the signal is transmitted from the transmitter 3 to the receiver 2 via one line of the power transmission line 5. Signals are sent from the transmitter 3 to the receiver 2 using a return-to-ground method in which one wire is grounded.
That is, by the following route. In the conventional example explained above, the capacitance C of the equivalent circuit 1 of the power transmission line represented by the lumped constant circuit is
2 and insulation resistance R1 in parallel impedance or capacitance C
The parallel impedance of 3 and insulation resistance R2 is transformer T2
When the impedance on the P side (primary side) of the transformer TO and the impedance of the capacitor C1 cannot be ignored, the voltage on the S side (secondary side) of the transformer TO which is relaying power is transferred to the next path, that is, C2. /R1 one earth-T2 (P side)-C1-T
0 (S side), a current due to the transmitted power flows through the P side of the transformer T2 of the receiver 2, and a voltage is induced on the S side of the transformer T2, which becomes noise on the receiving side.

That is, the signal-to-noise ratio of the received signal output between the receiving terminal P4 of the receiver 2 and the ground becomes small, that is, the noise level becomes large compared to the level of the signal to be transmitted, which is extremely inconvenient. Depending on the type of electric wire, such as an overhead cable or a submarine cable, the values of each element in the equivalent circuit shown in the lumped constant circuit above will vary, causing fluctuations in the noise voltage. The impedance of the transmitter 3 side or . It is difficult to take measures to improve the signal-to-noise ratio on the receiver 2 side, etc., and the conventional method of transmitting and receiving signals using one line of the power transmission line has a fatal drawback in terms of noise countermeasures. are doing.
The present invention has developed a signal transmission method that eliminates the above drawbacks. This provides an easy way to do so.

FIG. 2 shows a circuit diagram of an embodiment of the present invention. The difference from FIG. At receiver 2, capacitors Cl and C7
The signals are received from both lines of the power transmission line 5 through the capacitors CO, C6 and Cl, C7.
The value of is such that the above signal is transmitted in the same phase on both lines of the power transmission line 5 by the ground return method (i.e.,
The bridge consisting of the capacitors CO, C6, Cl, and C7 and the ground insulation impedance is set to a value that balances the bridge, and the electrical connection between both power transmission lines and the ground is set on the receiver 2 side. A capacitor C8 is added to finely adjust the degree of unbalance to maintain balance as much as possible.

Further, the signal transmission line is configured by connecting capacitors C6 and C1 and capacitors CO and C7 in series to each of both lines of the power transmission line, and both lines of the above-mentioned transmission line a become a parallel signal transmission line for the above-mentioned signal. is transmitted from the signal sending terminal P3 to the signal receiving terminal P4 in a ground return method.

In Figure 2, C7・R1=C1・R2, C2・C7=
C1・C3 and CO・R1=C6・R2, C2・CO=
Capacitors CO and C are connected so that the relationship of C6 and C3 is established.
By setting the values of l, C6, and C7, a bridge equilibrium condition is established between the S side of transformer T1, the P side of transformer T2, and both lines of the power transmission line, and a signal is sent to both lines of the power transmission line. Since the signals are sent in the same phase, no transmission voltage or line noise appears on the S side of the transformer T1 and the P side of the transformer T2.

Note that the capacitor C8 is for finely adjusting errors in the above relationship. In this way, capacitors CO, Cl, C
6 and C7 in an adjustable manner, and furthermore, the capacitor C
8's fine-tuning greatly improved the signal-to-noise ratio.

That is, in the conventional single-wire transmission system, it is impossible to avoid deterioration in the transmission quality of the signal caused by power transmitted through the power transmission line or line noise, but with the present invention, the transmission quality from the transmitting side cannot be avoided. r + r mouth s in that the signal is configured so that it is transmitted in the same phase from both lines of the power transmission line to the ground, and the receiving side is also configured to receive the above-mentioned transmitted signal from both lines of the power line to the ground in the same phase. ; TlOA+0A provides a signal transmission system in which signal transmission quality can be maintained at a high level, and the present invention has extremely significant effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional signal transmission method, and FIG. 2 is a circuit diagram showing a signal transmission method according to an embodiment of the present invention. (Main symbols), 1...Equivalent circuit showing the power line as a pseudo lumped constant circuit, 2...Receiver, 3...
・Transmitter, 4... Load on power line, 5...
・Power transmission line, TO... Power relay transformer, T1
...Signal transmission relay transformer, T2...
Signal reception relay transformer, C2, C3, C4...
・Pseudo capacitance of power transmission line 5, Rl, R2, R3...
Insulation resistance of power transmission line 5, CO, Cl, C6, C7, C8・
...Capacitor.

Claims (1)

[Scope of Claims] 1. In a signal transmission method that uses power transmission lines to transmit signals using a return-to-ground method, power is transmitted from the power transmission side via a transformer to both sides of the power transmission line. Both wires are insulated from the ground, and a signal transmission path is formed between both wires of this power transmission line and the ground, and the transmitter and both wires of the power transmission line are connected, and the receiver is connected to both wires of the power transmission line. In order for the signal to be transmitted in the same phase on both lines of the power transmission line, a bridge is formed by a coupling element between the transmitter and receiver and both lines of the power transmission line, and the ground insulation impedance of both lines of the power transmission line. A signal transmission method using power lines that is characterized in that an equilibrium condition is established. 2. Claim 1, characterized in that the transmitter's signal output line and both power transmission lines are coupled by capacitors, and the receiver's signal input line and both power transmission lines are coupled by capacitors. A signal transmission method using power lines as described in .