JP2857687B2 - Power line carrier signal transmission method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for transmitting a power line carrier signal using a high-voltage distribution line as a signal transmission path. The present invention relates to a power line carrier signal transmission method and apparatus capable of performing stable signal transmission even in a system state in which a zero-phase voltage changes even during transmission.

[0002]

2. Description of the Related Art As a conventional power line carrier signal transmission device, a zero-phase voltage change in a three-phase high-voltage distribution line at the time of signal transmission as described in Japanese Patent Application Laid-Open No. Sho 62-171236, "Power Line Carrier Transmission Device". In some cases, the impedance element of the zero-sequence voltage generating circuit is switched so that the size of the minute is about 1% of that at the time of occurrence of a complete ground fault. A demodulation circuit for reproducing a signal transmitted from a zero-sequence voltage change as described in JP-A-2-72728 "Power line carrier signal transmission device" has been proposed. Or higher order frequencies.

[0003]

When the impedance of the distribution line to the ground is stable, communication is possible even at about 0.1 to 0.3%. A method is conceivable. However, when trying to lower the level of the zero-sequence voltage by the conventional technique, the following problem occurs. That is, when salt damage occurs in the distribution line and the insulation of the insulator deteriorates, the ground impedance fluctuates. In this case, since the zero-phase voltage of the distribution line fluctuates asynchronously, the output signal of the filter circuit that detects the change in the zero-phase voltage also fluctuates asynchronously.

[0004] When salt damage occurs in the distribution line in this way, the impedance to ground fluctuates due to insulation deterioration of the insulator,
Permanent noise is generated in the output of the change in the zero-phase voltage detected from the distribution line. If data transmission / reception is performed using a zero-phase carrier signal in such a system state, the signal component waveform may be affected by the transmission / reception, and transmission data may not be correctly reproduced.

FIG. 5 shows an example of an actually measured waveform of a change in the zero-phase voltage which is the output of the demodulation circuit in the conventional power line carrier signal transmission device. FIG. 7A shows a variation output when the impedance to the ground is stable. The ratio (k2 / k1) between the variation output k2 and the noise component k1 during signal transmission, that is, S /
The output waveform has an N ratio of about 10. Also, FIG.
This is an output waveform when the ground impedance fluctuates, the S / N ratio drops to 3 to 4, and the output of the change in the zero-sequence voltage is affected by the noise component.

As described above, when the output level (noise component) at the time of non-transmission due to the change in the ground impedance becomes large, the change k2, k2 'in FIGS. 5A and 5B is constant in the conventional apparatus. Because it is managed to be a value,
When the noise component k1 'increases as shown in FIG.
There is a problem that the S / N ratio is reduced and the transmission reliability is deteriorated.

The present invention has been made in view of such circumstances, and a power line carrier signal transmission method and method capable of maintaining high transmission reliability even when the ground impedance fluctuates due to salt damage to a distribution line. It is intended to provide a device.

[0008]

SUMMARY OF THE INVENTION A power line carrier signal transmission method according to the present invention comprises a master station installed in a distribution substation, and a master station located at an arbitrary position on a three-phase high-voltage distribution line from the distribution substation. A slave station having the same configuration is provided, a three-phase high-voltage distribution line is used as a transmission line, and a change in the zero-phase voltage on the three-phase high-voltage distribution line is used as a transmission signal, so that the signal transmitting station transmits a zero-phase voltage on the three-phase high-voltage distribution line. In a power line carrier signal transmission method in which a signal is transmitted between a master station and a slave station by changing a phase voltage, the master station generates noise, which is fluctuation of a zero-phase voltage on a three-phase high-voltage distribution line when a signal is not transmitted. The level of the component is measured, and the level of the signal component at the time of signal transmission is calculated based on the level of the noise component so as to have a preset S / N ratio, and the three-phase high-voltage distribution is performed according to the level of the signal component. Changing the zero-sequence voltage on the line And it features.

In the power line carrier signal transmission method according to the present invention, the master station determines a ratio of a signal component obtained from the three-phase high-voltage distribution line when the signal is transmitted to a noise component obtained from the three-phase high-voltage distribution line when the signal is not transmitted. A plurality of set values for determining an S / N ratio are prepared in advance, and when calculating the level of a signal component at the time of signal transmission, one of the plurality of set values is selected according to the purpose of signal transmission. Is calculated.

[0010] Furthermore, the power line carrier signal transmission device of the present invention further comprises:
Among the three-phase high-voltage distribution lines from the distribution substation, one phase is used as a reference, and a plurality of three-phase high-voltage distribution lines connected to the ground via switching means in order to change the ground impedance of this reference phase. A zero-phase voltage generation circuit having an impedance element, and a ground-to-ground voltage of each phase of a three-phase high-voltage distribution line are taken out.
A master station having a demodulation circuit for detecting a system zero-phase voltage from the voltage between the ground and detecting and decoding a change in the system zero-phase voltage and a measurement circuit for measuring a change in the system zero-phase voltage is used for power distribution. A substation having the same configuration as the master station is installed at an arbitrary position on the three-phase high-voltage distribution line from the distribution substation, and the three-phase high-voltage distribution line is used as a transmission line. In a power line carrier signal transmission device in which a change in a zero-phase voltage generated in a system by a zero-phase voltage generation circuit is used as a transmission signal, a master station takes in an output signal of a measurement circuit, and outputs a zero-phase signal from a measurement circuit output during non-transmission. The level of the noise component due to the voltage fluctuation is measured, and the level of the signal component at the time of transmission is calculated based on the level of the noise component so as to have a preset S / N ratio. Zero phase voltage Characterized in that it has a control means for selecting an impedance element for zero-phase voltage generation circuit.

Further, in the power line carrier signal transmission device of the present invention, the control means includes a ratio of a signal component obtained from the output of the measurement circuit during transmission to a noise component obtained from the output of the measurement circuit during non-transmission. Preparing a plurality of set values for determining the / N ratio in advance, and selecting and calculating one of the plurality of set values according to the purpose of signal transmission when calculating the level of a signal component during transmission It is characterized by.

[0012]

In the power line carrier signal transmission method and apparatus having the above configuration, the master station measures the level of the noise component, which is the fluctuation of the zero-phase voltage on the three-phase high-voltage distribution line during non-transmission, and determines the level of this noise component. Based on this, the level of the signal component at the time of transmission is calculated so as to have a preset S / N ratio, and the zero-phase voltage on the three-phase high-voltage distribution line is changed according to the level of the signal component.

In the power line carrier signal transmission method and apparatus having the above configuration, the ratio of the signal component obtained from the three-phase high-voltage distribution line when the master station transmits the signal to the noise component obtained from the three-phase high-voltage distribution line when the signal is not transmitted is transmitted. A plurality of setting values for determining the S / N ratio are prepared in advance, and one of the plurality of setting values is selected according to the purpose of signal transmission when calculating the level of the signal component at the time of transmission. Is calculated based on the selected set value.

Therefore, according to the present invention, high transmission reliability can be maintained even if salt damage occurs to the distribution line and the ground impedance fluctuates.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of a power line carrier signal transmission device according to the present invention. In FIG. 1, the power line carrier signal transmission device includes a master station device 10 and a slave station device 20.

The master station device 10 installed on the side of the main transformer 1 in the distribution substation includes a zero-phase voltage generating circuit 11 for generating a zero-phase voltage in the system, and a zero-phase voltage ( V0) and a zero-phase reception voltage dividing circuit 12 for extracting a reference phase voltage (VA), a control command and a measurement command are transmitted to the slave station device 20, and return information from the slave station device 20 is received. And a low-pressure controller 13 for processing.

The low-voltage control unit 13 includes a demodulation circuit 14
It comprises a measurement circuit 15 and a master station transmission / reception control circuit 16.

On the other hand, the slave station device 20 installed at an arbitrary position on the high-voltage distribution line 2 has the same structure as the zero-phase voltage generation circuit 11 and the zero-phase reception voltage dividing circuit 12. It is composed of a zero-phase reception voltage dividing circuit 22 having a configuration, and a low-voltage control unit 23 that receives a control command and a measurement command from the master station device 10, performs control and measurement, and performs a return process to the master station device 10. I have.

The low voltage control unit 23 includes a demodulation circuit 25,
And a slave station transmission / reception control circuit 24. The demodulation circuit 14 (demodulation circuit 25) includes a band-pass filter (BPF1) 30, a band-pass filter (BPF2) 31 for extracting a fundamental wave component from the input reference phase voltage VA and zero-phase voltage V0 as shown in FIG. , A multiplying circuit 32, a first filter circuit 33 for removing a double frequency component and extracting a DC component, a second filter circuit 34 for detecting a change in the DC voltage, and a second filter circuit 34. And a waveform shaping circuit 35 that reproduces and outputs digital "1" and "0" data (RD) as binary signals from the output signal of.

The operation of the power line carrier signal transmission device having the above configuration will be described with reference to FIG. The divided output of the reference phase voltage VA of the high-voltage distribution line 2 is input to the low-voltage control unit 13 of the master station device 10, and in synchronization with this, the master-station transmission and reception control circuit 16
Controls ON / OFF of the switch SW0 of the zero-phase voltage generation circuit 11 according to the transmission data. Switch SW0 to O
By performing N and OFF control, any one of the capacitors C1 to C3 is inserted between the ground and a zero-phase voltage having a phase opposite to that of the reference phase is generated in the system.

On the other hand, the reference phase voltage (VA) and the zero-phase voltage (V0) are input to the low-voltage controller 23 of the slave station device 20 via the zero-phase reception voltage dividing circuit 22. Now, in response to the reference phase voltage signal VA as shown in FIG. 3A, the switch SW0 of the zero-phase voltage generation circuit 11 is turned OFF as shown in FIG.
When data is transmitted by controlling N and OFF, a zero-phase voltage V0 is generated (FIG. 3C). In the demodulation circuit 25 of the slave station device 20, the multiplication circuit 32 has a band-pass filter (B
The reference phase voltage signal VA and the zero-phase voltage signal V0 are taken in via the PF1) 30 and the band-pass filter (BPF2) 31, and a signal containing a frequency component and a DC component twice as high as these signals is output (FIG. D)). Here, in the multiplication circuit 32, the reference phase voltage signal VA is supplied to the negative input terminal and the zero-phase voltage signal V
0 is input to the positive input terminal, and the “presence” and “absence” of the zero-phase voltage signal correspond to the “presence” and “absence” of the DC component. Only the DC component of the output signal of the multiplying circuit 32 is extracted by the first filter circuit 33, and a DC component output corresponding to the presence or absence of the zero-phase voltage signal V0 is obtained.
(FIG. 3E). Next, the second filter circuit 34 obtains an output signal proportional to the DC component, that is, a change in the zero-phase voltage signal (FIG. 3F). Second filter circuit 34
Is output from the waveform shaping circuit 35 to the positive or negative detection level L.
1, L2 (the output signal is set to logic "1" when the change output is equal to or higher than the level L1, and the output signal is set to logic "0" when the change output is equal to or lower than the level L2). The signal is reproduced (FIG. 3 (G)). The digital “1” demodulated by the demodulation circuit 25 in this manner,
The "0" signal (RD) is input to the slave station transmission / reception control circuit 24, and the slave station transmission / reception control circuit 24
Receives information sent from.

On the other hand, the digital "1" and "0" signals transmitted from the slave station
The master station transmission / reception control circuit 16 receives the same operation by the zero-phase reception voltage dividing circuit 12 and the demodulation circuit 14 as in the slave station apparatus.

Data transmission and reception between master station device 10 and slave station device 20 are performed as described above. Control of switches SW1 to SW3 in zero-phase voltage generation circuits 11 and 21 is performed as follows. . That is, the measuring circuit 15 in FIG. 2 takes in the change output 17 of the demodulation circuit 14 and performs full-wave rectification of the output 17 to output a DC component voltage signal k proportional to the magnitude of the zero-phase voltage signal V0. I do. The master station transmission / reception control circuit 16 determines the magnitude of the change in the zero-phase voltage in the distribution system based on the output voltage value of the measurement circuit 15, and generates the zero-phase voltage in accordance with the magnitude of the change in the zero-phase voltage. The switching control of the switches SW1 to SW3 of the circuit 11 is performed. Now, when the ground impedance changes and the zero-sequence voltage fluctuates in the distribution line 2, the rectified output of the measurement circuit 15 outputs the noise component at the level of k1 even during non-transmission, as shown in FIG. 4B. .

The master station transmission / reception control circuit 10 fetches the noise component k1 before transmission and sets the current switches SW1 to SW1.
From the control state of SW3, the ratio (k2
/ K1) is within (1) the set value, it is determined that the switching control of the switches SW1 to SW3 of the zero-phase voltage generation circuit 5 is appropriate, and the control state of the switches SW1 to SW3 is left as it is, and (2) If the value is equal to or less than the set value, the switches SW1 to SW3 are controlled so that a larger zero-phase voltage is generated. SW3 is controlled to perform data transmission. For example, the case where the set value is 10 will be described. In FIG. 1B, the noise component k1 which is the output of the measurement circuit 15 when the signal is not transmitted is 0.
Assuming that it is equivalent to 01%, the calculated value of the change output k2 of the measuring circuit 15 is as follows: k2 = 0.01% × 10 = 0.1% (1) Therefore, the switches SW1 to SW3 are controlled so as to have a zero-phase voltage change corresponding to 0.1%, and data is transmitted as shown in FIG.

On the other hand, the demodulation circuit 25 in the slave station device 20 determines a positive or negative detection level from the magnitude of the output 17 corresponding to the change, and reproduces the received data correctly as shown in FIG. Therefore, even if the state of the distribution system changes and the noise component increases or decreases, the noise component k1
The signal transmission can be performed while keeping the ratio of the change amount output k2, that is, the S / N ratio constant.

According to this embodiment, since the S / N ratio is kept constant, good signal transmission can be performed even if the noise component increases due to salt damage.

Next, another embodiment of the present invention will be described. In this embodiment, the device configuration is the same as the previous embodiment,
The processing contents of the master station transmission / reception control circuit 10 are modified as follows. That is, a plurality of set values for managing the ratio between the change output k2 of the measurement circuit 15 and the noise component k1, for example, two values of 5 and 10 are prepared, and the values of the master station device 10 and the slave station device 20 are determined. In the case where signal transmission is performed between devices, if the purpose can be achieved by retransmission even if a transmission error occurs, the set value of the S / N ratio is set to 5, and the signal is reliably transmitted to the slave station device 20. When transmission is desired, the set value of the S / N ratio is set to 10, and the zero-phase voltage generation circuit 5 is controlled. With this configuration, for example, when remote monitoring control of the pole switch of the distribution line 2 is performed, most of the signal transmission of the monitoring command that can be achieved by retransmission is performed. Can be reduced.

According to this embodiment, the load on the zero-phase voltage generating circuit can be reduced, and the reliability of the device can be improved. In the above two embodiments, when the S / N ratio is calculated, when the noise component k1 is approached, the change output k2 to be targeted is set.
However, in order to stably operate the device, the minimum value k2 'of the variation output k2 is limited to a level that can be demodulated. Therefore, the change output k of the measuring circuit 15
When the calculation result of 2 becomes equal to or less than the minimum value k2 ', the lower limit limiter is applied so that the actual change output of the measurement circuit 15 becomes k2', so that the output of the measurement circuit 15 at the time of non-transmission is obtained. The unstable operation of the device when a certain noise component k1 approaches zero is eliminated.

When the noise component k1 becomes large,
The generated voltage of the zero-phase voltage also increases, but the upper limit is determined in cooperation with the protection relay. From this, the measurement circuit 15
If the calculation result of the change output k2 is equal to or greater than the upper limit value determined from the cooperation with the protection relay, the limiter is set so as to be equal to the upper limit, thereby coordinating with the protection relay.

Further, when the capacitance to ground changes due to system switching during transmission and the output k2 of the change of the measuring circuit 15 exceeds the upper limit, transmission is immediately stopped to cooperate with the protection relay. .

[0031]

As described above, according to the present invention, the level of the noise component due to the fluctuation of the total system zero voltage when the signal is not transmitted is measured, and the S / S preset based on the level of the noise component is measured. The switching control is performed so that the level of the signal component at the time of transmission is calculated so as to be N ratio, and the impedance element for generating the zero-phase voltage of the zero-phase voltage generating circuit is selected according to the level of the signal component. Therefore, high transmission reliability can be maintained even if the ground impedance fluctuates due to salt damage on the distribution line.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a power line carrier signal transmission device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of a demodulation circuit and a measurement circuit in FIG.

3 is a waveform diagram showing an operation state of each unit of the power line carrier signal transmission device shown in FIG.

4 is a waveform chart showing a relationship between transmission / reception data and an output of a measurement circuit in the power line carrier signal transmission device shown in FIG.

FIG. 5 is a waveform diagram showing a signal transmission state in a conventional power line carrier signal transmission device.

[Explanation of symbols]

 2 High-voltage distribution line 10 Master station device 11 Zero-phase voltage generation circuit 12 Zero-phase reception voltage divider 13 Low-voltage controller 14 Demodulation circuit 15 Measurement circuit 16 Master station transmission / reception control circuit 20 Slave station device 21 Zero-phase voltage generation circuit 22 Zero-phase Reception voltage dividing circuit 23 Low voltage control unit 24 Slave station transmission / reception control circuit 25 Demodulation circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Kazuo Nishijima 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant, Hitachi, Ltd. (56) References JP-A-51-21415 (JP, A) JP-A-1-223832 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 3/54-3/56

Claims (4)

(57) [Claims] A master station installed in a distribution substation and a slave station having the same configuration as the master station are provided at an arbitrary position on a three-phase high-voltage distribution line from the distribution substation. The transmission line is used as a transmission line, and the station on the signal transmitting side uses the change in the zero-phase voltage on the three-phase high-voltage distribution line as a transmission signal, and changes the zero-phase voltage on the three-phase high-voltage distribution line to change the master station and the child station. In the power line carrier signal transmission method for performing signal transmission with a station, the master station measures a level of a noise component that is a fluctuation of a zero-phase voltage on the three-phase high-voltage distribution line when the signal is not transmitted, and Calculating the level of the signal component at the time of transmission so as to have a preset S / N ratio based on the level of the signal, and changing the zero-phase voltage on the three-phase high-voltage distribution line according to the level of the signal component. Characteristic power line carrier signal transmission method. 2. The master station sets an S / N ratio, which is a ratio of a signal component obtained on the three-phase high-voltage distribution line during signal transmission to a noise component obtained on the three-phase high-voltage distribution line during non-transmission. A plurality of values are prepared in advance, and when calculating the level of a signal component at the time of transmission, one of the plurality of set values is selected and calculated according to the purpose of signal transmission. 2. The power line carrier signal transmission method according to 1. 3. A three-phase high-voltage distribution line from a distribution substation, with one phase as a reference, and a switching means between the three-phase high-voltage distribution line and the ground to change the ground impedance of the reference phase. A zero-phase voltage generation circuit having a plurality of impedance elements connected thereto, and a ground-to-ground voltage of each phase of the three-phase high-voltage distribution line is taken out, a system zero-phase voltage is detected from the ground-to-ground voltage, and the system zero-phase voltage is detected. A demodulation circuit that captures and decodes the change;
A master station having a measurement circuit for measuring a change in the system zero-sequence voltage is installed in a distribution substation, and the same as the master station at an arbitrary position on a three-phase high-voltage distribution line from the distribution substation. A power line carrier signal transmission device that installs a slave station having the configuration described above and uses a three-phase high-voltage distribution line as a transmission line and a change in zero-phase voltage generated in the system by the zero-phase voltage generation circuit as a transmission signal. The master station captures the output signal of the measurement circuit, measures the level of the noise component due to the fluctuation of the zero-phase voltage from the output of the measurement circuit during non-transmission, and sets a preset S / N based on the level of the noise component. A control means for calculating a level of a signal component at the time of transmission so as to obtain a ratio and selecting an impedance element for generating a zero-phase voltage of the zero-phase voltage generating circuit according to the level of the signal component. Power Line carrier signal transmission device. 4. The control means according to claim 1, wherein said ratio is a ratio between a signal component obtained from said measurement circuit output during signal transmission and a noise component obtained from said measurement circuit output during non-transmission.
A plurality of set values for determining the / N ratio are prepared in advance, and when calculating the level of the signal component at the time of transmission, one of the plurality of set values is selected and calculated according to the purpose of signal transmission. The power line carrier signal transmission device according to claim 3, wherein: