JPS6258222B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a safety circuit for telephone subscribers that effectively prevents the fuse from blowing when an impact current flows in, promotes normal discharge of a lightning arrester discharge element, and discharges the lightning to the ground. The present invention relates to a fault current interrupting method that achieves the purpose of safety by properly blowing out the fuse in response to a sustained current inflow.

The basic configuration of the current security circuit for telephone subscribers is that a fuse F is inserted in series in the line connecting the outside line L and the internal line I, as shown in Figure 1, and the internal line side of the fuse is used for lightning protection discharge. Element A is grounded, and in response to the inflow of shock current caused by lightning, etc., the lightning protection discharge element A is discharged to promote discharge to the ground, and in addition, it is designed to prevent the inflow of sustained current caused by high voltage contact, etc. is designed to cut off high pressure by blowing fuse F. However, at present, even in the case of an inflow of shock current due to lightning, if the energy is large, fuses often blow. Fuse blowouts caused by lightning often occur over a wide area affected by lightning, and moreover, often occur in mountainous areas with relatively poor transportation, so the losses required for maintenance and operation are extremely large.

Therefore, the present invention provides a fuse detour circuit for discharging the shock current to the ground without passing through the fuse F in the above-mentioned basic safety circuit, thereby accurately preventing the fuse from blowing due to lightning as described above, and at the same time, when a sustained current flows in. The connection point of this detour circuit is melted by the discharge heat of the lightning arrester, and the heat flows into the fuse side, and the fuse is blown normally, and the high voltage is cut off, so that the detour circuit opens when the sustained current flows in. The present invention provides a method for interrupting fault current in a telephone safety circuit, which allows reliable and sensitive operation. That is, FIG. 2 shows a specific circuit example of the above invention with one side line L.
In the safety circuit consisting of the fuse F and the lightning protection discharge element A explained in Figure 1, as shown in Figure 2, the lightning protection discharge element A' of the safety circuit is shown as -I. A bypass intermediate electrode b is provided which faces the line electrode a and the earth electrode c in the same gas atmosphere, and the line electrode a is connected to the inner line side I of the fuse F, the earth electrode c is grounded, and one end is connected to the fuse. A fuse detour circuit B is connected to the outside line side L of F, and the other end is connected to the intermediate electrode b.
The connection point S between the fuse bypass circuit B and the intermediate electrode b is connected with a low melting point metal such as solder. Therefore, when an impact current flows in due to lightning, discharge necessarily occurs through the fuse detour circuit.
That is, fuse bypass circuit B → connection point S → intermediate electrode b
→It is configured so that discharge through the earth electrode c and discharge to the earth can be obtained, and when a sustained current flows in due to high voltage contact, etc., the fuse detour circuit B causes a preceding discharge between the bypass intermediate electrode b and the earth electrode c. , the connection point S between the fuse detour circuit B and the intermediate electrode b is thermally fused by the discharge heat of the lightning arrester A', and at the same time as the fuse detour circuit is cut off, the preceding weak weakening between the line electrode a and the intermediate electrode b is generated in advance. Using discharge (glow discharge) as a trigger, line electrode a → earth electrode c
This system quickly induces a sustained discharge between the two, thereby blowing out the fuse, thereby appropriately shutting off the high voltage.

Even if a disconnection force P is constantly applied to the connection point S between the fuse bypass circuit B and the intermediate electrode b of the three-pole lightning arrester A', in order to improve the disconnection caused by the fuse blowout. good.

The fuse detour circuit B is extremely simply constructed by simply connecting the conducting wire to the intermediate electrode b of the three-pole arrester A' using a low melting point metal as described above. In order to enable external connection of the conducting wire, a part of the intermediate electrode b may be made to protrude outside the lightning arrester, and a terminal portion may be provided.

Based on the above principle, Figure 3 shows the lines L ₁ - I ₁ and L ₂ -
This shows the case where the above safety circuit is configured between I _{and 2} . That is, using a pentode discharge tube as a common lightning protection discharge element A'', and based on the above principle circuit diagram, a conductor is connected to the intermediate electrode b interposed between the line electrode a and the earth electrode c on the line L ₁ - I ₁ side. One end is connected with a low melting point metal to constitute a first fuse detour circuit, and also a line
One end of the conducting wire is connected to the intermediate electrode b' interposed between the line electrode a' and the ground electrode c on the L ₂ - _I 2 side using a low melting point metal to form a second fuse detour circuit, and the same as above. If a sustained current due to high voltage contact flows into the fuse detour circuit B ₁ or B ₂ , the connection point S ₁ or S ₂ made of the low melting point metal is quickly fused by the discharge heat of the lightning arrester, and the fuse F ₁ or _F2 . However, in this case, compared to the case where individual lightning protection discharge elements are used for lines L ₁ - I ₁ and L ₂ - I ₂ , a single five-pole lightning protection discharge element A'' is used as a common lightning protection discharge element for both lines. By using it as an element, when an impulse current or a sustained current flows into each line with a time difference, it is possible to immediately induce a discharge between electrodes b' → c following a discharge between electrodes b → c. , due to the superimposed discharge heat, both connection points
The melting of S ₁ and S ₂ can be made more sensitive.

Therefore, since the present invention is configured as described above,
When an impact current caused by lightning or the like flows from the outside wire side, it does not flow into the fuse F, but flows into the fuse detour circuits B, B ₁ , B ₂ and the lightning protection discharge elements A',
A'' is discharged and a ground discharge is obtained.As a result, it is possible to accurately prevent the fuse from blowing due to the inflow of shock current, and the ground discharge can complete safety functions such as preventing electric shock and preventing damage to the telephone. Shock current caused by lightning is an instantaneous phenomenon even if its energy is large, and unlike sustained current, the ground voltage rise is not localized but spreads over a wide area affected by lightning. There is no particular need to blow fuses F, F ₁ and F ₂ .
The safety purpose can be achieved by the earth discharge action of lightning protection discharge elements A' and A''.

In addition, in the case of sustained current inflow due to high voltage contact, etc., the lightning protection discharge elements A' and A'' are similarly discharged first via the fuse detour circuits B, B ₁ and B ₂ , and immediately after that , the fuse bypass circuits B, B ₁ , B ₂ and the lightning arrester A′, due to the continuous current inflow.
The connection points S, S ₁ and S ₂ of A″ are precisely fused by the discharge heat of the lightning arresters A′ and A″. As a result, the sustained current flows reliably into the line, flows through the fuse F and the lightning protection discharge elements A' and A'', and causes them to continue to be discharged.
During this sustained discharge, the fuse F reaches the point of melting, and the high voltage is completely cut off between the outside lines L, L ₁ , L ₂ and I, I ₂ , I ₂ of the line.

Further, the present invention achieves the above-mentioned effects, and when a sustained current inflows due to high voltage contact, etc., the fuse detour circuit B causes a preliminary discharge between the bypass intermediate electrode b and the earth electrode c, and therefore connects to the electrode a. The fuse bypass circuit is made safe by ensuring that the connection point S between the fuse bypass circuit B and the intermediate electrode b is thermally fused by the discharge heat of the lightning arrester A' without fear of causing a fault current to flow into the equipment in which the fuse bypass circuit B is connected. At the same time, a sustained discharge between line electrode a and earth electrode c is triggered by the preceding weak discharge (glow discharge) between line electrode a and intermediate electrode b, which causes the fuse to be cut off. The high pressure can be cut off reliably by obtaining a melt cut.

In addition, the fuse detour circuit B is extremely simply constructed by simply connecting the conducting wire to the intermediate electrode b of the three-pole arrester A' using a low melting point metal as described above. In order to enable external connection of the conducting wire, a part of the intermediate electrode b may be made to protrude outside the lightning arrester, and a terminal portion may be provided.

The present invention is based on the existing telephone subscriber security circuit (first
The purpose can be achieved simply by wiring a conducting wire to bypass the fuse F in Figure), and the circuit configuration is extremely simple without the need for any additional parts. Therefore, it does not become a factor of cost increase. A lightning arrester simply adds the number of poles and does not lead to an increase in parts.

[Brief explanation of the drawing]

FIG. 1 is a basic circuit diagram of a conventional security circuit for telephone subscribers, FIG. 2 is a basic circuit diagram showing an embodiment of the present invention, and FIG. 3 is an applied circuit diagram thereof. L...external line side, I...internal line side, F...fuse,
A′, A″…Lightning protection discharge element, a, a′…Line electrode,
b, b'...intermediate electrode for bypass, c...earth electrode,
R, R'...Resistance, S, _S1 , _S2 ...Connection point between the fuse detour circuit, which is fused by the discharge heat of the lightning arrester, and the intermediate electrode of the lightning arrester.

Claims (1)

[Claims] 1. Insert a fuse in series in the line connecting the outside wire side and the inner wire side, and ground the inner wire side of the fuse with a lightning protection discharge element, and blow out the fuse in case of sustained current inflow, and prevent shock current inflow. To prevent this, the discharge of the lightning protection discharge element is obtained to encourage discharge to the earth, and the impulse current and sustained current flowing into the line are passed through a circuit that bypasses the fuse to promote discharge of the lightning protection discharge element and discharge to the earth. In the safety circuit for telephone subscribers, the lightning protection discharge element is provided with a bypass intermediate electrode facing in the same gas atmosphere as the line electrode and the ground electrode, and the bypass intermediate electrode is provided with the above one end. The other end of the detour circuit connected to the outside wire side of the fuse is connected via a low melting point metal, and in response to sustained current inflow, the heat generated by the lightning arrester discharge element connects the fuse detour circuit and the bypass intermediate between the lightning arrester discharge element. A fault current interrupting method characterized in that the connection point with the electrode is fused and the fault current is caused to flow through the fuse to promote sustained discharge of the lightning protection discharge element and to fuse the fuse.