JPH0472416B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power distribution line transmission device that uses a power distribution line as a transmission line, and particularly relates to a power distribution line transmission device that uses a power distribution line as a transmission line, and particularly relates to a power distribution line transmission device that uses a power distribution line as a transmission line, and in particular, a power distribution line transmission device that uses a power distribution line as a transmission line. The present invention relates to a power distribution line transmission device suitable for.

[Prior Art] In general, many domestic power distribution systems are essentially ungrounded systems, and are not actually grounded or are grounded through a high resistance. In such non-grounded distribution line systems, Japanese Patent Publication No. 49-38495 and Japanese Unexamined Patent Application Publication No. 55-55 are proposed as signal transmission devices that use the current and voltage of so-called zero-phase circuits as signals.
The one described in Publication No. 130243 is known. Both change the zero-sequence voltage by tangential impedance between the distribution line and the ground.
In the device shown in the above-mentioned Japanese Patent Publication No. 49-38495,
A low frequency power source is used as a power source for transmission signals,
On the receiving side, only the low frequency signal is discriminated and used as a received signal. Therefore, in order to obtain low frequency power, it is essential to step down the voltage of the distribution line while insulating it with a transformer, convert it to DC with a converter, and create low frequency power again. converter,
Since rectifying capacitors, amplifiers, etc. are required, the size of the device cannot be avoided.

In order to avoid increasing the size of such a device, the device shown in the above-mentioned Japanese Patent Laid-Open Publication No. 130243/1983 has been proposed. This device uses a commercial frequency power source as the power source for the transmission signal, whereas the above-mentioned devices use a low frequency power source as the power source for the transmission signal, thereby avoiding an increase in the size of the device. Below, the relevant JP-A-Sho
The device described in Japanese Patent No. 55-130243 will be explained.

As shown in FIG. 1, the voltage transformed by a transformer 1 is sent to distribution lines 3, 4, 5 via a bus 2,
A zero-sequence current detector 50 is provided on the power distribution line 5, and a master station 6 is provided that uses the zero-sequence current _I0 detected from the zero-sequence current detector 50 as a transmission reception signal. Further, a switch _S1 is connected to one line of the distribution line 5 near the master station 6 via an impedance 7, and when this switch _S1 is closed by a signal from the master station 6, the impedance 7 is grounded. be done.

On the other hand, a slave station 8 is provided at a suitable distance from the master station 6 to detect a zero-sequence current on the distribution line and to detect a transmission signal generated by the master station 6. Similar to the master station 6, this slave station 8 is also configured such that one line of the distribution line 5 having the same phase as the master station 6 can be grounded via an impedance 7 by a switch _S2 .

Now, by opening and closing the switch _S2 in the slave station 8 using a transmission code signal of "1, 0", the impedance 7 is grounded and a slight change in the zero-sequence current is generated. In the master station 6, a zero-sequence current detector 50 detects the minute change in the zero-sequence current generated by the slave station 8, and receives a transmission signal from the slave station 8.

[Problem to be solved by the invention] The device described in the above-mentioned Japanese Patent Application Laid-Open No. 55-130243 has the following problems:
Signals can be transmitted with an extremely simple configuration without requiring a low frequency power source.

However, the capacity between each three-phase line of a distribution line and the ground differs for each line depending on the configuration of the distribution system on the load side. Zero-sequence voltage and zero-sequence current (hereinafter referred to as residual zero-sequence components) are generated.
Therefore, the zero-sequence current and voltage generated by the device described in JP-A-55-130243 become relatively small due to the presence of the residual zero-sequence component, and the S/N ratio decreases significantly. , signal detection becomes practically impossible.

To avoid this, you can reduce the impedance 7 and increase the injection signal, but normally,
Protection relays on distribution lines detect faults in distribution lines by detecting when the residual zero-sequence component exceeds a predetermined value. no means can be adopted.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power distribution line transmission device that can solve the problems in the prior art described above, can be made compact, and can reliably send and receive signals.

[Means for Solving the Problems] In order to achieve the above object, the present invention arranges a plurality of stations consisting of a master station and a slave station along an ungrounded distribution line, and provides a zero-phase circuit of the ungrounded distribution line. In the distribution line transmission device for transmitting signals between each station using A signal transmitting section that generates a desired zero-phase signal by the above-mentioned zero-phase circuit, and a signal receiving section that receives a signal from the own station or another station are provided, and the signal receiving section is provided with a zero-phase signal obtained from the zero-phase circuit and a signal receiving section that receives a signal from the own station or another station. a product calculation circuit that calculates a product with a reference signal taken out from the ungrounded distribution line; a filter circuit that removes a second harmonic component from the output of this product calculation circuit; The switch is characterized by comprising a signal demodulation section configured with a signal derivation circuit that removes the zero-phase signal component when the switch is in the open state and derives only the zero-phase signal when the switch is in the closed state. do.

[Operation] When transmitting and receiving signals between each station, when the switch of one station is opened or closed, the switch and the impedance are connected in series to one phase of the distribution line.
Opening and closing of the switch may cause a ground fault, causing fluctuations in the current and voltage of the zero-phase circuit.

The signal receiving section of the other station receives the current and voltage of the zero-phase circuit as a zero-phase signal, and separately,
A product calculation circuit (a circuit that outputs a voltage proportional to the product of the instantaneous values of two input analog signals) integrates a reference signal extracted from one phase or between lines of a distribution line and created. As a result, a signal in which a DC component and a second harmonic component proportional to the product of the respective maximum values of the zero-phase signal and the reference signal are superimposed is obtained.

Of this signal, the second harmonic is removed by the filter circuit, and of the remaining DC component, the DC component due to the stationary residual zero-sequence component is removed by the signal derivation circuit, and is finally output from the signal derivation circuit. The signal generated is the same as the opening and closing of a switch at the signal generating station.

Among the above operations, the zero-phase signal, the reference signal, and the signal obtained by their product are shown in a vector relationship diagram showing the magnitude and phase relationship in FIG. 2 as follows.

The received waveform of the zero-phase signal, which is the received signal at the receiving end, is composed of the signal vector, which is the zero-phase signal component, generated by the switch opening and closing at the transmitting end, and the residual zero-phase component, which is constantly generated in the distribution line. It is the vector sum with the stationary residual vector.
Therefore, by storing the waveform of the stationary residual vector in an alternating current manner and subtracting it from the vector sum in an analog manner, only the signal vector can be detected as an information signal. However, since alternating current storage of waveforms is circuit-complex, in the present invention, a reference signal is generated as described above, and the residual zero-sequence component is converted into a DC component based on the product of this reference signal and the zero-phase signal. It is something to remember.

Here, if the vector of the reference signal (reference vector) is in phase with the signal vector, the reference vector is expressed as shown in the figure. At all times (when the switch is open), the DC component signal represented by the in-phase component vector' is detected by multiplying the residual zero-phase component represented by the stationary residual vector and the reference signal represented by the reference vector. on the other hand,
When a signal vector is generated by the signal transmitting switch, the zero-phase signal becomes a signal of the sum of the residual zero-sequence component expressed by the vector sum and the fluctuation due to the switch closure, and is calculated by multiplying this sum signal and the reference signal. , a DC component signal represented by an in-phase component vector ' is detected. Hereinafter, by subtracting the in-phase component vector' from the in-phase component vector', a signal component proportional to the signal vector can be obtained as an information signal.

Note that the reference vector that is in phase with the signal vector is determined by the impedance, since the zero-sequence voltage and zero-sequence current that occur when one line of the distribution line is grounded through an impedance, and the zero-sequence current have a constant relationship with the phase voltage. Once determined, it can be easily obtained by inputting the phase voltage or line voltage and shifting the phase using a phase shift circuit. For example, when the impedance is a capacitor, the zero-sequence voltage is in-phase with the phase voltage,
The zero-sequence current has a 90 degree lead relationship with the phase voltage.

[Embodiment] An embodiment of the present invention will be described below based on the circuit configuration diagram shown in FIG. 3 and the operation waveform diagram of each part shown in FIG. 4.

Fig. 3 shows the signal receiving section of the master station 6 or slave station 8, and it receives a zero-phase signal (zero-phase current or zero-phase voltage).
It is equipped with a signal demodulation section that receives the input from the distribution line 5 and reproduces the open/closed state of the switch _S1 or _S2 . In addition,
Although such a signal receiving section is provided in all stations, here, signal demodulation in the master station 6 when the switch _S2 is opened and closed in the slave station 8 will be explained.

The signal receiving section in FIG. 3 receives a zero-sequence signal as a transmission signal (in the example shown, the zero-sequence current I ₀ is input from the zero-sequence current detector 50, but this may also be a zero-sequence voltage). Then, one of the voltages between arbitrary phases or lines (in the illustrated example, the voltage V _a of the a-phase) is taken in as a reference signal by the voltage divider 9 . Of these, the zero-sequence current I ₀ is taken into the first filter 11 as a voltage signal V _ip via a resistor R ₁ provided between the output terminals of the zero-sequence current detector 50 . The first filter 11 extracts only the fundamental wave component from the two captured signals V _ip and V _a , but the reason for removing lower harmonics and higher harmonics will be explained later. This is important in faithfully reproducing the transmitted signal.

Here, FIG. 4a shows the open/close state of the switch S ₂ in the slave station 8, and during this opening/closing, the current is introduced into the product calculation circuit 12 via the distribution line 5, the zero-sequence current detector 50, and the filter 11. The resulting voltage signal V _ip is shown in FIG. 4b. Since there is a residual zero-sequence component in the power distribution system, the voltage signal is switched to switch S ₂ as shown in Figure 4b.
It is not only detected when closed (ON),
It is also detected when switch _S2 is open (OFF). Among these, the voltage signal V _ip when the switch S ₂ is in an open state is a residual zero-sequence component V _ir that is constantly generated in the distribution line, and is a fixed component determined by the configuration of the distribution system. On the other hand, the voltage signal detected when the switch is closed is composed of the zero-sequence component V _is as a transmission signal generated by connecting the impedance 7 to the ground, and the residual zero-sequence component V _ir.
It is a composite signal of Therefore, for demodulation,
It is only necessary to remove V _ir and extract only V _is .

For this separation, the product calculation circuit 12 in FIG. 3 multiplies the voltage signal V _ip and the reference signal V _a shown in FIG. As a result, a composite signal of the second harmonic component V _f2 and the DC component V _fp determined by the two AC magnitudes |V _ip |, |V _a | and the phase difference θ is obtained. This is clear from the fact that when the signals V _ip and V _a are expressed as equations (1) and (2), respectively, the signal (V _ip・V _a ) that is the product of both is expressed as equation (3). .

V _ip = |V _ip | sinωt …(1) V _a = |V _a |sin (ωt+θ)…(2) V _ip・V _a = (1/2) |V _ip | |V _a | {cos(2ωt+θ) )
+cosθ} …(3) In this embodiment, the transmission signal (switch
DC component as a signal related to ON, OFF)
This focuses on V _fp , and the second filter 13
, the AC component V _f2 is removed and only the DC component V _rp is taken out.

As shown in Figure 4 f, the DC component V _fp is proportional to the magnitude of the residual zero-phase component V _ir when the switch is off, and is proportional to the magnitude of the residual zero-phase component V _ir and the transmission zero-phase signal V when the switch is _on . The size of the vector sum of _is | V _ir + V _is |
is proportional to. Therefore, the residual zero-phase component at all times |V _ir |
By storing and removing it from the output of the second filter 13, the original transmission signal |V _is | can be extracted only when the switch is turned on.

Therefore, in this embodiment, the second filter circuit 1
3 and the non-inverting input of the comparator circuit 14,
Integrating circuit consisting of resistor 23 and capacitor 22, and resistors 24, 25, 26, 27, 28
and a subtraction circuit consisting of operational amplifiers 29, 30, and 31. Resistor 23 and capacitor 2
The time constant of the integrator circuit consisting of Continue to hold _ir |

The operational amplifier 30 is used as a voltage follower, and is designed to input the output voltage of the integrating circuit and a high input resistance, and serves as one input of the subtracting circuit. On the other hand, the output of the operational amplifier 30 is connected to the inverting input of the operational amplifier 31 via the resistor 27.

The operational amplifier 29 and the resistors 24 and 25 constitute an inverting amplifier, which serves as another input to the subtraction circuit. Since the resistors 24 and 25 are chosen to have the same value, the inverting amplifier output is the inverted output of the second filter circuit 13.

The output of operational amplifier 29 is connected via resistor 26 to the inverting input of operational amplifier 31. The circuit consisting of the operational amplifier 31 and the resistors 26, 27, 28 has the same resistance value as the resistors 26, 27, 28, so that the output of the operational amplifier 29 (the fourth
The result obtained by adding the inverted output of the signal f shown in the figure and the output of the operational amplifier 30 is inverted and input to the operational amplifier 31.

FIG. 4h shows the output of the operational amplifier 31, that is, the output of the subtraction circuit. As is clear from this waveform diagram, the difference between one input waveform of the subtraction circuit (f in Fig. 4) and the other input waveform (g in the same figure) is the output of the subtraction circuit as shown in h of the same figure. That is why it is done.

With respect to this subtraction circuit output, the detection voltage 19 at the inverting input of the comparator circuit 14 is connected to the control voltage 18 by the resistor 15
The voltage is divided by R ₂ and 16R ₃ , and the residual zero-sequence component |V _ir | and the output voltage when the switch is turned on |V _ir +V _is
By setting it to the middle of the difference between |, Figure 4 i
As shown in the figure, output information of "1" and "0" corresponding to the on/off information of the switch can be taken out to the terminal 17. According to this embodiment, the detection voltage of the comparator circuit is
It can be set regardless of the size of the residual zero phase component.

Note that by removing harmonics from the input of the product calculation circuit 12, it is possible to prevent harmonics from being mixed in as a DC component error caused by the product of inputs of the same order.

[Effects of the Invention] According to the present invention, a low frequency power source is not required, the device can be made smaller, and since it is not affected by residual zero-phase components, highly sensitive and reliable signal transmission can be performed.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of the distribution line signal transmission equipment.
FIG. 2 is a vector relationship diagram explaining the magnitude and phase relationship of each signal, FIG. 3 is a circuit configuration diagram of a signal receiving section of a distribution line transmission device according to an embodiment of the present invention, and FIG.
The figure is a signal waveform diagram of each part shown in FIG. 3. 2...Bus bar, 5...Distribution line, 9...Voltage divider, 1
DESCRIPTION OF SYMBOLS 1...First filter circuit, 12...Product calculation circuit, 13...Second filter circuit, 14...Comparison circuit, 22...Capacitor, 23...Resistor, 2
9, 30, 31... operational amplifier, 50... zero-phase current detector.

Claims (1)

[Claims] 1. In a distribution line transmission device in which a plurality of stations consisting of a master station and a slave station are arranged along an ungrounded distribution line, and signals are transmitted between the stations using a zero-phase circuit of the ungrounded distribution line, the Each station includes a signal transmission unit that is composed of a series circuit of an impedance and a switch connected between one line of the ungrounded distribution line and the ground, and generates a desired zero-phase signal by opening and closing the switch, and a signal transmission unit that generates a desired zero-phase signal by opening and closing the switch, and and a signal receiving section for receiving a signal from the non-grounded distribution line, and the signal receiving section includes a product operation for calculating the product of the zero-phase signal obtained from the zero-phase circuit and the reference signal taken out from the ungrounded distribution line. a filter circuit that removes a second harmonic component from the output of the product calculation circuit; and a filter circuit that removes the zero-phase signal component when the switch is in an open state from the output of the filter circuit, and closes the switch. 1. A power distribution line transmission device comprising: a signal demodulation section configured with a signal derivation circuit that derives only the zero-phase signal when the zero-phase signal is in a positive state.