JPH03222631A - Lightning-protection method for plural communication devices using ac power supply - Google Patents

Abstract

PURPOSE:To prevent lightning surge voltage from being generated between unspecific communication devices even in a communication system, where plural communication devices are connected, by providing precedence in arrester operating voltage of the communication device and further specifying the method of connecting a grounding cable to the earth from the communication device. CONSTITUTION:In the case of a lightning surge intruding from an AC power line 3, lightening surge voltage is applied between the AC power line 3 and internal circuits 1-1, 8-1 or earth terminals 1-2, 8-2. However, since an arrester 5-1 of the lowest operating voltage is set In a primary communication device 1, this arrester 5-1 is first operated. in the case of a lightning surge intruding from a communication cable 2, the lightning surge is allowed to flow out to the earth 7 from a grounding point of the primary communication device 1, but potential is generated between the AC power line 3 and the earth terminals 1-2, 8-2 by the increasing potential at the grounding point. However, also in this case, the lightning surge, passing through the arrester 5-1, is allowed to flow out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lightning protection method for a communication system in which a plurality of communication devices using AC power are connected and used.

[Conventional technology] In recent years, communication devices have become more electronic and multifunctional.

The number of communication devices that use AC power is increasing.Because lightning surge voltage intrudes from both the communication line and the AC9 source line, communication devices that use AC power have the trap of conventional stand-alone telephones that are connected to only one communication line. They are exposed to harsher environments compared to other countries, and highly reliable lightning protection measures are desired.

Figure 4 is an example of a conventional lightning protection method when a communication device using AC power is used alone, where 1 is the communication device using AC power, 1-1 is the internal circuit of the communication device, and 1-2 is the communication device. Ground terminal of the device, 2 is a communication cable, 2-1 is a cable core, 2-2 is a cable sheath, 3 is an AC power line, 4 is an arrester for the communication cable core, 5 is an arrester for the AC power line, 6 is an arrester for the AC power line. The ground wire, 1, is the earth. This method is generally called the Pi/Yas arrester method, and is applied to home telephones, facsimiles, and the like.

In the communication device using AC power in Fig. 4, arresters 4 and 5 are used to protect the internal circuit 1-1 of the communication device from lightning surge voltage that enters from the communication line cable 2 or the AC power line 3. According to the lightning surge resistance of 1-1, the operating voltage is set slightly lower than that. Therefore,
These arrester operating voltages often vary depending on the individual device pressure.

Next, FIG. 5 shows an example of a conventional communication system in which a plurality of communication devices using AC power are connected within the same premises or in a house, where 1 is the primary communication device connected to the communication cable first, 8 is the other communication device, and 8 is the primary communication device connected to the communication cable first. The communication device 9 is an interface cable between the communication devices. 9. Let 6-1 be the grounding wire of the communication device 1, 6-2 be the grounding wire of the communication device 8, and 6-3 be the grounding wire connecting the communication devices 1 and 8, and let the impedance of each grounding wire be Zl, Let Zl and Z3. Vl.

v2 is the arrester operating voltage between the AC@@@ line 3 and the ground terminal 1-2.8-:1 of the communication devices 1 and 8, respectively. 8
-1 is an internal circuit of another communication device, and 5-1 and 5-Z are arresters for the AC power line.

As an example of such a communication system, 1 is a communication line termination device, and 8 is an AC'i! having various functions. A case can be considered in which communication devices using a single source are connected to each other.

Conventional arrester designs and ground wire connection methods are designed for the individual devices shown in Figure 4, so even in the case shown in Figure 5, simply connect the communication devices individually designed in Figure 4, or 9. Regarding grounding to the earth, grounding is done from arbitrary devices to the earth due to construction circumstances, and at present there is no clear design method.

[Problem to be solved by the invention] When a lightning surge enters from an AC power line or a communication line, the arrester of the communication device with the lowest operating voltage operates first, and from there the lightning surge is directed to the ground and transmitted to the ground line with low impedance. Current will flow out, but in the conventional communication system, the ground impedances Zl, Z2 . The values of Z3 and the arrester operating voltages v and v2 are unspecified and vary, and the communication device where the arrester operates and the current flow path are not determined initially, so in some cases, the arrester operates far away from the communication device where the arrester operates. There were cases where lightning surge current flowed to the ground point.

The potential difference between communication devices is determined by the impedance of a grounding wire that interconnects the communication devices and the value of the current flowing therethrough. For this reason, in conventional communication systems, the outflow path of lightning surge current is not determined.

An unexpected grounding current may flow through the grounding wire, creating a large potential difference between the communication devices, resulting in the problem of destruction of the connection between the interface cable and the communication device.

This problem occurs when a plurality of communication devices are connected, and is a problem that goes unnoticed in conventional individual communication device designs.

In view of the above, an object of the present invention is to provide a method for setting the operating voltage of an arrester and a method for connecting a grounding wire so that lightning surge voltage does not occur between unspecified communication devices even in a communication system that connects a plurality of communication devices. An object of the present invention is to provide a lightning protection method for multiple communication devices using an improved AC source.

Means and Effects for Solving the Problem] In order to achieve the above-mentioned object, the present invention provides a communication system in which a plurality of communication devices using AC power are connected and used within the premises or home of rFfJ-. A of the primary communication device that is first connected to the communication cable that has been pulled in
Set the arrester operating voltage between the C power supply line and the ground terminal to be lower than the arrester operating voltage of other communication devices, and use the primary communication device as a grounding point to ground all other communication devices. The system is characterized in that the wire is connected to the grounding wire of the primary communication device, and the arrester operating voltage of the communication device is ranked, and the method of connecting the grounding wire from the communication device to the ground is specified. The main feature of this technology is that it clearly limits the outflow path of lightning surges from conventional technology.

[Example 1] FIG. 1 is a diagram explaining a first example of the present invention. In FIG. 1, the same parts as those in FIG. 5 will be described with the same reference numerals. In FIG. 1, the arrester operating voltage v1 between the AC power line 3 and the ground terminal 1-2 of the primary communication device 1 that is first connected to the communication cable 2 is the arrester operating voltage v2 of the other communication devices 8. Set lower. f9. For grounding, connect the ground terminal 1-2 of the primary communication device to the ground 7, and connect the ground terminal 8 of the other communication device 8 to this ground terminal 1-2.
-2 through the grounding wire 6-3, and this grounding terminal 1-
In cases other than 2, there is no grounding point to the earth 7.

In FIG. 1, first consider the case where a lightning surge enters from the AC power line 3. In this case, the lightning surge voltage is applied to the Act source line internal circuit 1- of each communication device 1, 8.
1.13-1 or between the ground terminals 1-2.8-2, but the arrester 5-2 with the lowest operating voltage is connected to the primary communication device 1.
1, this arrester 5-1 operates first, and a lightning surge current flows toward the ground 7. In this case, in FIG. 1, since the primary communication device 1 is the only grounding point to the earth 1, the lightning surge current does not flow to the other communication devices 8.

All communication devices connected to ground point No. 2 are at the same potential.

Next, consider a case in which a lightning surge enters from the communication cable 2. In this case, lightning flows from the grounding point of the primary communication device 1 to the earth 1, but the potential at the grounding point rises due to the grounding impedance z of the earth 7, and the AC power line 3
A potential difference occurs between the ground terminal 1-2, and the ground terminal 1-2, 8-2 of each communication device. However, in this case as well, in FIG. 1, since the arrester 5-1 with the lowest operating voltage is the primary communication device IK,
The lightning surge current flows through the arrester 5-1 of the primary communication device, and no lightning surge current flows to the other communication devices 8. Therefore, it is possible to prevent potential differences from occurring between communication devices.

In addition, in FIG. 1, the primary communication device 1 is connected to the communication cable 2.
However, even when there is no communication cable, a specific communication device is regarded as the primary communication device, its arrester operating voltage is set lower than that of other communication devices, and the arrester operating voltage is set lower than that of other communication devices. The same effect as in Fig. 1 can be obtained by using the grounding point as the grounding point. Also.

Regarding the communication device 8, if the lightning surge resistance reliability of the internal circuit 8-1 is high, the arrester 5-2 can be removed.

If a communication device other than the primary communication device is used as a grounding point or if the arrester operating voltage is set low, lightning surge current will flow from the primary communication device to the grounding wire between the grounded communication devices. To flow.

The same problem as the conventional one shown in FIG. 5 occurs, so care must be taken.

! FIG. 82 shows experimental results showing the effects of the embodiment of the present invention. In Figure 2, the first
A lightning surge voltage (waveform 1 x 40 μs) is applied between the AC power line and the ground, respectively, and the communication device 1
The potential difference between communication devices 1 and 8 is measured by changing the impedance z3 of the grounding wire connecting between and 8, and curve A is the same as that shown in FIG. This is the case where Z1=100Ω and ZJ=10, and there are two grounding points.

The potential difference between communication devices is smaller in curve A than in curve B, and the effect of the present invention can be confirmed.

Next, FIG. 3 shows a second embodiment of the present invention, in which 10 is A
This is an arrester exclusively for the C power line. In Figure 3, A
C power line dedicated arrester 10th is installed at the inlet of the C power supply 1s3 in the premises, and its operating voltage VJi is the arrester operating voltage V1.8 of the communication device 1.8 located in the same premises. Set to a voltage lower than V2.

Also in FIG. 3, internal circuits 1-J of communication devices 1 and 8
, 8-1 lightning surge resistance reliability, Arrester 5
-1.5-2 can be removed.

Regarding the grounding method, the grounding of the AC power line dedicated arrester IO and the grounding of the communication cable 2 are made the same grounding point, and all the grounding wires of the primary communication device 1 and other communication devices 8 are connected to this grounding point.

In the configuration shown in FIG. 3, since none of the communication devices 1.8 serves as an outflow path for lightning surge current, there is an advantage that adverse effects such as electromagnetic induction due to lightning surge current can be avoided.

[Effects of the Invention] As explained above, in the present invention, when a plurality of overconfidence devices are used in the same premises, the arrester operating voltage of the primary communication device connected first to the communication cable 9 is set to the lowest, and the Since the terminal is grounded only at the terminal, even if lightning surge enters from either the AC power line or the communication cable, the lightning surge current will not flow around to other communication devices, and the outflow path can be limited. Additionally, all communication devices within the premises can be kept at the same potential at all times, providing highly reliable lightning protection.

This also applies to conducted interference waves that enter from AC power lines or communication cables, and by applying the present invention, it can be expected that the interference resistance will be improved.

[Brief explanation of drawings]

Fig. 1 is a configuration explanatory diagram showing one embodiment of the present invention, Fig. 2 is a characteristic diagram showing an example of the effects of the present invention in comparison with conventional effects, and Fig. 3 is a diagram showing another embodiment of the present invention. Fig. 4 is a configuration explanatory diagram showing an example of lightning protection measures when a conventional communication device using AC power is used alone, and Fig. 5 shows a conventional communication device using AC power in the same premises or in a house. FIG. 2 is a configuration explanatory diagram showing an example of a lightning protection method when a plurality of lightning protection devices are connected. J...Primary communication device 51-1 which uses AC power and is first connected to the communication cable...Internal circuit of the primary communication device, 1-2...Internal circuit of the primary overconfidence device ground terminal,
2...Communication cable5. ? -1-...Communication cable core 1tA, z-x...Communication cable sheath, 3...
AC power line %4... Communication cable arrester, 5...
・AC power line arrester, 6...Grounding wire, 6-1...
- Grounding wire of the primary communication device, 6-2... Grounding wire of other communication devices, 6-3... Grounding wire connecting the primary communication device and other communication devices, 7... Earth, 8...Communication device using AC power other than the primary communication device, 9...Interface cable, 10...Arrester exclusively for AC power line, Vl...Arrester operating voltage of the primary communication device. v2: Arrestor operating voltage of other communication devices, z: Grounding impedance of the primary communication device. z2...Grounding impedance of other communication devices, z
3... Impedance of grounding wire 6-3.

Claims (1)

[Claims] In a communication system in which multiple communication devices using AC power are connected within the same premises or in a house, the connection between the AC power line and the ground terminal of the primary communication device that is first connected to the communication cable brought in from outside the premises. The arrester operating voltage is set lower than the arrester operating voltage of other communication devices, and the grounding wire of all other communication devices is connected to the grounding point of the primary communication device with the above-mentioned primary communication device as a grounding point to the ground. A lightning protection method for multiple communication devices using an AC power source, characterized in that the devices are connected to a grounding wire.