JPS6315809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission monitoring system in a carrier end station device for power transmission line protection.

Conventionally, the transmission monitor method for monitoring the transmission output signal in a transmission line protection carrier end station device used to send and receive signals of a protective relay that detects a fault in the transmission line and shuts off the switch is shown in Figure 1. The configuration shown in the block diagram was used. In the figure, 1 is a transmitting circuit, 2 is a transmitting amplifier that amplifies the output of the transmitting circuit 1, 3 is a transmitting monitor circuit connected to the output side of the transmitting amplifier 2, 4 is a receiving circuit,
5 is a hybrid circuit for transmitting/receiving coupling for joining a 4-wire circuit and a 2-wire circuit, 6 is a line filter, and 7 is an isolation transformer.

In the device configured in this way, the output signal of the transmitting circuit 1 is amplified by the transmitting amplifier 2, and its output is led to the transmitting monitor circuit 3 to monitor the transmitting output. It is sent out to the line through a wave transformer 6 and an isolation transformer 7. On the other hand, the received signal input via the isolation transformer 7 and the line filter 6 is transferred to the hybrid circuit 5.
and is introduced into the receiving circuit 4 and also applied to the transmission monitor circuit 3. Here, the impression level of the transmission monitor circuit 3 is to detect not only a complete cutoff of the transmission output, but also a drop in power due to some kind of failure, for example, when the transmission power is reduced to 1/3.
It is set at 10dB drop point.

Therefore, when the reception input level applied to the transmission monitor circuit 3 is equal to or higher than the impression level of the transmission monitor circuit 3, the transmission circuit 1 or the transmission amplifier 2
Even if a failure occurs and the original transmission level drops below the set level, it cannot be detected because it is a received signal, so it cannot function as a transmission monitor.

In view of the above points, the present invention provides a transmission monitoring system designed to solve such problems, in which a transmission output monitoring circuit is connected to a balanced wiring network of a hybrid circuit for transmission and reception coupling, and the reception input signal is monitored. This allows only the transmitted output signal to be monitored without being affected. Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing one embodiment of the transmission monitoring system according to the present invention. In Figure 2, the first
The same reference numerals as in the figure indicate corresponding parts, and 8 is a transmission output monitoring circuit connected to the balanced wiring network of the hybrid circuit 5 for transmitting and receiving coupling.

Next, the operation of the embodiment shown in FIG. 2 will be explained. First, the output signal of the transmitting circuit 1 is transmitted to the transmitting amplifier 2.
The output is amplified by the hybrid circuit 5, passed through the line filter 6, and sent to the line via the isolation transformer 7, and the divided signal is transmitted to the balanced wiring network side of the hybrid circuit 5. The signal is applied to the monitoring circuit 8 to monitor the transmission output.

On the other hand, the received signal input via the isolation transformer 7 and the line filter 6 is divided by the hybrid circuit 5, and its output is applied to the receiving circuit 4 and the transmitting amplifier 2, respectively.

Here, the received input signal in the direction of the transmission output monitoring circuit 8 connected to the balanced wiring network side of the hybrid circuit 5 is attenuated by the wrap-around attenuation of the hybrid circuit 5, so it has a sufficiently small value with respect to the transmission signal. , the transmitted signal can be monitored regardless of the received input level.

As is clear from the above description, according to the present invention, the disadvantage is that the transmission monitor malfunctions due to the received signal when the transmission output level is cut off or decreased by using a simple configuration without using complicated means. This has been improved and it is possible to monitor only the transmitted output signal without being affected by the received input signal, so the practical effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional transmission monitoring system, and FIG. 2 is a block diagram showing an embodiment of the transmission monitoring system according to the present invention. 1... Transmission circuit, 2... Transmission amplifier, 4... Receiving circuit, 5... Hybrid circuit, 6... Line filter, 7... Isolation transformer, 8... Transmission output monitoring circuit.

Claims (1)

[Claims] 1. A transmission monitoring system in a carrier terminal station device for power transmission line protection that transmits and receives signals via a hybrid circuit for transmitting and receiving coupling, characterized in that a transmission output monitoring circuit is connected to a balanced connection network of the hybrid circuit for transmitting and receiving coupling. .