JPH03852Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial field of application) This invention is applicable to communication lines such as PCM transmission lines.
The present invention relates to a protection circuit for protecting repeaters from abnormal voltages that enter cables due to lightning surges, single line ground faults in power transmission lines, etc.

(Conventional technology) Conventionally, in communication lines such as PCM transmission lines,
A repeater is installed in the middle of the communication line to compensate for signal attenuation. Figure 3 shows an example of this type of transmission path.
3 is a repeater, L ₁ ~ L ₄ , L ₁ ′ ~ _{L 4} ′ is a cable, T ₁ ~
T ₆ is a transformer, A ₁ to _{A 4} are cables L ₁ , L ₂ , L ₁ ′,
A detonator to absorb the abnormal voltage that enters L ₂ ′,
S ₁ to _{S 4} are surge absorption elements such as varistors, Z ₁
~Z ₄ respectively indicate the impedance for current limiting.

In this transmission line, a DC power supply B is connected between the neutral points of the secondary windings of the transformers T ₁ and T ₅ on the terminal stations 11A and 12B side, and the resulting DC current is connected to the signals of the cables L ₁ and L ₂ . From the neutral point of the primary winding of the transformer _T2 to the resistor R, the Zener diode is superimposed on the
ZD, the neutral point of the secondary winding of the transformer T ₃ and the cables L ₁ ′, L ₂ ′, so that the voltage drop generated across the series circuit consisting of the resistor R and the Zener diode ZD is transferred to the relay 13. power source, and at the same time make effective use of cables.

In this transmission line, when an abnormal voltage as shown in the figure enters cable L ₁ or L ₂ due to a lightning surge, for example, the arrester A ₁ or A ₂ discharges and releases the surge current to the ground, and then relays it. Vessel 1
This prevents abnormal voltage from being applied to 3. Here, the surge absorbing elements S ₁ and S ₂ operate to absorb the surge voltage until the lightning arresters A ₁ and A ₂ operate. In addition, the other lightning arrester A ₃ , A ₄ and surge absorption element S ₃ , S ₄ are connected to the receiving side cable L ₁ ′ or
A similar protective operation is performed when abnormal voltage enters L ₂ '. Although not shown,
Other similarly configured repeaters, lightning arresters, surge absorbing elements, etc. are also connected between the cables L ₃ , L ₄ and L ₃ ′, L ₄ .

(Problem that the invention attempts to solve) However, when absorbing abnormal voltage, the detonator
There is no problem if the discharge characteristics of A ₁ to _{A 4} , especially the discharge starting voltage, are uniform, but in the case of this type of arrester, as shown in Fig. 4, a certain arrester has a voltage V ₁ ,
There are significant variations in the discharge start voltage, such as one detonator discharges at time t ₁ while another detonator starts discharging at voltage V ₂ and time t ₂ .

For this reason, for example, if the discharge starting voltage of the receiving side surge arresters A ₃ and A ₄ is lower than that of the transmitting side surge arresters A ₁ and A ₂ , the abnormal voltage that has entered the cable L ₁ or L ₂ Lightning arresters A ₃ and A ₄ on the receiving side discharge first, and the resulting surge current flows through cable L ₁ or
From L ₂ the primary winding of the transformer T ₂ , the resistor R and the Zener diode ZD, the secondary winding of the transformer T ₃ ,
It will flow to the ground via lightning arresters A ₃ and A ₄ ,
This reduces the resistance R and the Zener diode
There was a risk that repeater 13 would become inoperable due to the destruction of ZD.

In order to prevent this, another detonator _A5 is connected in parallel to the series circuit of _the resistor R and the Zener diode ZD as shown in _FIG . An attempt has also been made to discharge this arrester _A5 using the voltage E across the circuit to prevent a large current from flowing through the resistor R and the Zener diode ZD for a long period of time, but even in this circuit, the voltage E A large surge current flows into the series circuit until the discharge starting voltage of the arrester _A5 is reached, and this causes the resistor R to
There was also the problem that the Zener diode ZD was destroyed.

The present invention was proposed to solve the above problems, and its purpose is to create a single abnormal voltage absorbing element such as a detonator, which is connected between the sending and receiving cables of the transmission line and the ground. Abnormal voltage that enters the cable is reliably absorbed by
To provide a protection circuit for a repeater that prevents surge current from flowing into a power supply circuit of the repeater.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for connecting a transmission line between a transmitting side cable and a receiving side cable via a transformer, and between the transformer. In a repeater equipped with a power supply circuit that supplies power with a voltage drop due to flowing direct current, a first diode bridge connected between the cables on the transmitting side and the cables on the receiving side. A second diode bridge, an abnormal voltage absorbing element connected between the output terminals of the first and second diode bridges, and a reverse connection to the output terminals of the first and second diode bridges. diodes connected to each other and grounded, and configured such that the terminal voltage of the abnormal voltage absorbing element during operation is lower than the terminal voltage of the power supply circuit.

(Function) In the present invention, the terminal voltage during operation of abnormal voltage absorbing elements such as detonators connected between the transmitting side cable and receiving side cable of the transmission line and the ground is configured using resistors, Zener diodes, etc. By setting the terminal voltage lower than the terminal voltage of the power supply circuit of the repeater, the surge current is prevented from flowing to the power supply circuit side, thereby protecting the repeater from abnormal voltage.

(Example) An example of the present invention will be described below with reference to the drawings. First, Figure 1 shows a communication line such as a PCM transmission line using the present invention, and in the figure, L ₁ , L ₂
indicates a cable connected to a terminal station on the transmitting side (not shown), L ₁ ′, L ₂ ′ indicates a cable connected to a terminal station on the receiving side, and these cables L ₁ , L ₂ ,
L ₁ ′ and L ₂ ′ are connected to the repeater 1 via transformers Ta and Tb. A power supply circuit 2 consisting of a resistor R and a Zener diode ZD is connected to the power terminal of this repeater 1, and a cable cable is connected as in the conventional case.
L ₁ , L ₂ , L ₁ ′, L ₂ ′ and the primary winding of transformer Ta,
It is configured to take out the voltage drop due to the direct current supplied via the secondary winding of the transformer Tb as the power supply voltage of the repeater 1.

On the other hand, a first diode bridge consisting of diodes _D1 to _D4 is connected between cables _L1 and _L2 on the transmitting side.
A second diode bridge DB ₂ consisting of diodes D ₅ to _{D 8} is connected between the cables L ₁ ′ and L _{2 ′} on the receiving side, and these diode bridges DB ₁ , DB ₂ are respectively connected to both ends of an abnormal voltage absorbing element 3 such as a detonator. Furthermore, a diode D ₁₀ is reversely connected to the connection point of the diodes D ₁ and D ₂ , and a diode D ₉ is similarly connected to the connection point of the diodes D ₃ and D ₄ .
Diode D ₁₁ is connected to the connection point of diodes D ₅ and D ₆ .
However, a diode D ₁₂ is connected in reverse to the connection point of diodes D ₇ and D ₈ . That is, the diodes D ₉ to _{D 12} are reversely connected to each output terminal of the diode bridges DB ₁ and DB ₂ , and the other ends of these diodes D ₉ to _{D 12} are collectively grounded. .

In addition, impedance Z such as a neutralizing coil or resistor, and surge absorbing elements S, S such as a varistor are connected to the cables L ₁ , L ₂ , L ₁ ′, and L 2 _′ , respectively. The point is connected to the cathode of diode D ₉ or the anode of diode D ₁₁ . Here, the impedance Z and the surge absorbing elements S, S are provided as appropriate, and are not necessarily essential to the configuration of the present invention.

Next, this operation will be explained. Now, in Figure 2, which shows the main part of Figure 1, if a positive abnormal voltage enters cable L ₁ or L ₂ on the transmitting side due to a lightning surge, etc., the abnormal voltage absorbing element 3 will discharge and conduct. , the surge current flows to the ground via the path of diode D ₁ or D ₂ → abnormal voltage absorbing element 3 → diode D ₁₂ . On the other hand, if a positive abnormal voltage enters the cable L ₁ ′ or L ₂ ′ on the receiving side, the surge current will flow to the ground via the path of diode D ₅ or D ₆ → abnormal voltage absorption element 3 → diode D ₉ . It flows. At this time, the terminal voltage of the abnormal voltage absorbing element 3
Va, in other words, the arc voltage of the detonator is about 10V or less, whereas in the power supply circuit 2, its terminal voltage Vb is dominated by the terminal voltage of the Zener diode ZD and is usually about 10V or more, causing abnormal voltage. Since the potential is higher than that of the non-grounded end of the absorption element 3, the surge current does not flow into the power supply circuit 2 side.
All of this will escape to the ground via the abnormal voltage absorbing element 3.

Next, when _a negative abnormal voltage enters _the cable L ₁ or L ₂ , the cable L _{1 or} If a surge current flows through L ₂ and, on the other hand, a negative abnormal voltage enters cable L ₁ ′ or L ₂ ′, the connection from ground to diode
D ₁₁ → Abnormal voltage absorption element 3 → Diode D ₈ or
A surge current flows through the cable L ₁ ′ or L ₂ ′ through the path D ₇ , and in this case as well, no surge current can flow into the power supply circuit 2 .

In this embodiment, the case where a detonator is used as the abnormal voltage absorbing element 3 has been described, but any device that can obtain a predetermined terminal voltage lower than the terminal voltage of the power supply circuit 2 during operation (conducting) may be used. For example, it is also possible to use a plurality of varistors etc. connected in series.

(Effects of the invention) As detailed above, according to the invention, surge current can be released to the ground by the abnormal voltage absorbing element without affecting the power supply circuit of the repeater in any case. Destruction can be prevented and the repeater can always operate normally.

In addition, since the required circuit elements are only a single abnormal voltage absorbing element, some diode bridges, and diodes, the structure is extremely simple and can be provided at low cost.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
This figure is a circuit diagram of the main part, FIGS. 3 and 5 are circuit diagrams showing a conventional example, and FIG. 4 is an explanatory diagram of discharge starting characteristics of a detonator. 1...Repeater, 2...Power circuit, 3...Abnormal voltage absorption element, _L1 , _L2 , _L1 ', _L2 '...Cable,
Ta, Tb...Transformer, R...Resistor, ZD...Zener diode, _DB1 , _DB2 ...Diode bridge, _D1 - _D12 ...Diode, Z...Impedance, S...Surge absorption element.

Claims (1)

[Claims for Utility Model Registration] Connected via a transformer between a cable on the transmitting side and a cable on the receiving side of a transmission line, and supplying power with a voltage drop due to a direct current flowing between the transformer. In a repeater equipped with a power supply circuit, a first diode bridge connected between the cables on the transmission side, a second diode bridge connected between the cables on the reception side, and the first and second diode bridges connected between the cables on the transmission side. an abnormal voltage absorbing element connected between each output terminal of the second diode bridge;
and a diode that is reversely connected to each output terminal of the second diode bridge and grounded, and the terminal voltage of the abnormal voltage absorbing element during operation is lower than the terminal voltage of the power supply circuit. A protection circuit for a repeater, characterized in that it is configured as follows.