JP2001051006A - Method of contrasting coaxial cables - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for removing connectors, enable the contrasting of a coaxial cable to be performed even during working, enable the contrasting of cables to be performed even in an environment poor in grounding and enable works conventionally difficult to be executed by one person to be performed in a method of contrasting the coaxial cable. SOLUTION: An a-c signal source is connected to an outer conductor and the ground at the terminal end of a coaxial cable 4 for a communication system using the coaxial cable 4, a clamp type leak meter 11, etc., is used to detect at parts with concentrated wirings such as overhead or pole distributors 3, or at connection points, etc., difficult to determine whether or not the cable is a user's one, and thereby the contrasting of coaxial cable 4 is enabled, without stopping the system or removing cables, i.e., even during working. The neutral point of a commercial power source is made out and this is passed via the ground of a pole transformer to enable the forming of a loop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a cable control method for communication wiring using a coaxial cable such as a CATV, a cable broadcast, and a coaxial Ethernet (registered trademark) LAN.

[0002]

2. Description of the Related Art Generally, in CATV and cable broadcasting, one-way communication is performed from a center, and when viewed from a user, the cable does not have a specific cable or core wire to the center, and is distributed overhead or installed on a pole. The same signal from the center was distributed by the device. For this reason, at the time of laying, it is not necessary to identify which user's house the cable is in the distribution part, and at present, the cable is not managed for the user.

[0003] Recently, there are some which perform two-way communication,
Unlike communication systems such as telephones, transmission lines are shared by adding an ID (identification code) to a signal to be transmitted. Therefore, the need to manage cables is low, and it is not managed for users. It was the current situation.

For this reason, when a failure occurs in a specific user or when a cable for a specific user is removed, a user who should control the cable of which connector of the distributor (hereinafter referred to as the user). As a method of confirming whether it is connected, search visually or remove the connector at the user's home, short-circuit, confirm the uncertainty, remove the connector of the distributor and check the DC resistance There was a risk of erroneous cutting. In addition, since it is necessary to remove the connector, it has been difficult to control the user who is using the device.

[0005] In addition, it is difficult to perform the control by a single worker when performing the control by such a method, and it is usually necessary for the worker to check on both sides of the user's house and the distribution part. Also, in the conventional cable identification device, it is necessary to equip the connector with a tap for taking out the center conductor in advance,
There is an economic problem, and it is necessary to suspend the service for the user who is equipped with the tap or the like.

[0006] These problems have also arisen at the connection point of a single cable, etc., in addition to the collective portion of coaxial cables, even when the cable is unknown if it is the cable of the corresponding user.

Further, the conventional cable contrast method using the ground at low frequency or direct current cannot be used in a place where the ground cannot be taken at the user's house. In addition, a measurement method using a high frequency usually requires a dedicated measurement device and is expensive.

In the conventional measuring method using a current flowing through a closed circuit via a ground, if grounding is impossible, it is necessary to check the ground side of a commercial power outlet and connect one end of an AC signal source thereto. There was a danger to the human body if the polarity was wrong.

[0009]

As described above,
The conventional method of contrasting cables had to remove the connector. For this reason, the service has to be temporarily interrupted by removing the connector. In addition, there is a possibility that a trouble may be caused by accidentally removing a connector of another user. Further, the conventional cable contrast method using the ground at low frequency or direct current cannot be used in a place where the ground cannot be obtained at the user's house.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the need for removing a connector by comparing coaxial cables using only their outer conductors, and to allow coaxial cables to be compared even during operation. It is another object of the present invention to make it possible to compare cables even in an environment with insufficient grounding, to solve the above-mentioned various problems, and to make it possible for one person to work alone, which has been difficult in the past.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method of contrasting a coaxial cable according to the present invention is described. Connected between the outer conductor and the ground, detecting the current flowing through each coaxial cable at the collective portion or connection portion of the coaxial cables, and judging the coaxial cable having the largest current as the coaxial cable to the user. I do.

According to the present invention, in a communication system using a coaxial cable, an AC signal source is connected to an external conductor and a ground at an end side of the coaxial cable, and wiring such as an overhead or a pole distributor is assembled. Even when it is difficult to determine whether the cable is the cable of the user at the connection point of the portion or the single cable, etc., the cable pulled into the user's house can be detected by detecting the cable using a clamp type leak meter or the like. Identify without stopping the system or disconnecting cables. That is, the coaxial cable can be compared even during operation. Claim 1
Includes the inside of the distributor and its vicinity, and the connecting portion also includes the inside of the cable connector and its vicinity.

Further, a midpoint of the commercial power supply is created, which can be formed as a loop via the ground of the pole transformer, and the commercial power supply frequency signal is attenuated at the output portion of the AC signal source. By equipping the circuit, it is possible to solve the above-mentioned problems by making it possible to compare cables even in an environment with insufficient grounding, without being aware of the polarity of the commercial power outlet and without causing leakage of the commercial power. is there.
The middle point of the capacitor in claim 2 refers to a portion of the wiring between the two capacitors and the wiring branched from the wiring, which is inside the common mode noise filter and in the vicinity of the filter.

The above-mentioned means uses a current passing through the ground, and in an environment where the external conductor is grounded at one end (the distributor side) such as a CATV, a grounding operation for measurement is required. Available without.

Further, by using an AC signal source in a frequency band of 1 KHz to 10 KHz, measurement can be performed with only a slight change to a commercially available clamp-type leak meter. Can be performed.

In addition, by performing intermittent oscillation for 1 second to 10 seconds or using a clamp-type leak meter with reduced sensitivity in the frequency range of the commercial power supply, it is possible to discriminate between the steady-state leakage current and the user's home side. This eliminates the need for an operator to operate the oscillator.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 shows an example of a configuration for carrying out the method of the present invention. By using the configuration of FIG. 1, the cable drawn into the user's house can be specified without stopping the communication system or removing the cable, that is, even during operation. In FIG. 1, 1,1 ′ is a utility pole,
2 is an overhead suspension wire (steel wire), 3 is a distributor, 4 is a trunk coaxial cable, 4 ₁ , 4 ₂ ,... Are coaxial cables to the user's house, and 4 _i is a coaxial to the user's house as a user. A cable 5, 5 is the user's home as a user, 5 'is another user's home, 6 is a security device for the user's home, and 6' is a security device for another user's home. Reference numeral 7 denotes an oscillator as an AC signal source, which is a connection point to the protector 6 at the end of the coaxial cable 4 _i to the user's house, and is connected between the outer conductor of the coaxial cable and the ground 8. 9 is a ground resistance between the oscillator 7 and the earth 8 (resistance value = C), 9 'is a ground resistance between the overhead suspension line 2 and the earth 8' (resistance value = A), 10 and 10 'are protectors 6 , 6 ′ and the grounds 8 _i , 8 _{i +1} (resistance = B). Reference numeral 11 denotes a clamp type leak meter for detecting a current, which is set on a cable 4 _i to the user's house in the figure.

In the configuration of FIG. 1, the output value of the clamp type leak meter 11 is set to 2 mA as an example at the connection point X of the oscillator 7 (the wiring connecting the outer conductor of the coaxial cable 4 _i and the oscillator 7). The adjustment is performed, and the current value is measured at the portion Y of the distributor 3 (the portion of the coaxial cable inside the distributor 3 and in the vicinity of the distributor 3) which is the aggregate portion of the cables. In oscillator 7 the connection point X is connected to an outer conductor of the coaxial cable 4 _i, usually without removing the connection part of the connector, i.e., while maintaining the operating state, can be connected. At this time, the AC signal flows through the outer sheath of the coaxial cable 4 _i to the user's home 5, enters the distributor 3, and connects the ground 8 ′ (through the grounding resistor 9 ′) of the overhead suspension line 2 to the other user's home 5. 'Ground 8 _{i + 1} (ground resistance 1
0 '). Current i ₁ flowing to the ground 8 of the overhead catenary 2 '2mA * B / (A +
B), the current i ₂ flowing through the ground 8 _{i + 1} of the other user's house 5 'becomes 2mA * A / (A + B ).

Normally, the ground resistance A is smaller than the ground resistance B, and the ground resistance C may be low enough to allow a current necessary for detection to flow. When the ground resistance B of the user's house 5 is low, the ground wire of the protector 6 is removed. In the figure, a state where the ground wire is removed is indicated by a cross. When the ground resistance B is sufficiently large with respect to A, the current flowing through the cable 4 _{i + 1} to another user's house is close to zero.

The sum of the incoming current and the outgoing current is equal.
The reading of the clamp-type leak meter 11
The cable closest to 2mA is the cable to the user's home 5.
Le 4 _iCan be determined. Here, for convenience,
Although the case where there is one other user's house 5 'has been described,
Of the clamp-type leak meter 11
The cable whose reading is closest to 2 mA is
Cable 4_iIt can be said.

Since this current value is very small, it has no effect on the human body. If the current value is such that it cannot be determined as a leak even if it flows into the earth leakage breaker via a terminal device or the like, especially 2
It need not be mA. Further, the indicated value of the clamp-type leak meter 11 and the true current value do not need to be the same.
Actually, by using a sufficiently high frequency (for example, 10 KHz) with respect to the commercial power supply frequency, detection of the earth leakage breaker can be avoided.

As is clear from this figure, the outer conductor of each coaxial cable is common to the casing of the distributor 3 and is connected to the ground 8 'via the overhead suspension line 2 and the installation resistor 9'. Therefore, there is no need to carry out grounding work to implement this measure.

[0023]

Embodiment 2 FIG. 2 shows another configuration example for carrying out the method of the present invention. By using the configuration of FIG.
This makes it possible to compare cables even in an environment where grounding is insufficient, such as when the ground resistance of the cable is high. FIG. 2 shows a configuration in a case where it is difficult to secure the ground. In FIG.
The same reference numerals are used for the same components as those in FIG. 7 'is an oscillating section of the oscillator 7, and 12 is a common mode noise filter. The ground side of one end of the output of the oscillator 7 is connected to a ground terminal Z (a wiring between the two capacitors 13 and a wiring branched from the wiring) which is a middle point of the capacitor 13 built in the common mode noise filter 12 on the commercial power supply side. Of the common mode noise filter 12 and a portion near the filter 12). The value of a commonly used capacitor is, for example, about 0.01 μF farad, and 300
Although it has a high resistance of about K ohms,
For a frequency of about KHz, it will be about 1600 ohms,
It is possible to obtain the current necessary for the work at a safe voltage (several volts).

The common mode noise filter 12
The resistance due to the inductance component of the coil portion and the pole transformer 14 is also in a low range. Thereby, the oscillator 7
1 through the capacitor 13 and the ground via the ground 8 ₀ (passing the ground resistance 9 ₀ (resistance value = D)) of the pole transformer 14 of the commercial power supply.
It is possible to perform the same cable comparison as the above. In this case, the current passes through the power outlet 15 of the earth leakage breaker in each home, but the current value is sufficiently small (about 2 mA) with respect to the normal detection current of 15 to 30 mA, and the frequency is sufficiently high with respect to the commercial power supply frequency. By using (for example, 10 KHz), detection of the earth leakage breaker can be avoided.

Further, by providing a circuit for attenuating a commercial power supply frequency signal as shown in FIG. 5 at the output portion of the AC signal source 7, it is possible to prevent a leakage current from flowing through the AC signal source 7. And perform safe measurement.

In the circuit of FIG. 5, one output terminal of the oscillator output portion 7 'of the oscillator 7 has a capacitor 17 for blocking a DC component from the oscillator output portion 7', a resistor 18 for limiting a short-circuit current, The other output terminal is connected to the middle point Z of the capacitor 13 and the output level adjusting variable resistor 1 is connected in series to the output level adjusting variable resistor 19.
9 is connected to the other end. 21 and 22 are output terminals of the circuit.

At this time, since the potential at the midpoint Z is half the commercial power supply voltage (usually 100 V for home use in Japan), when the capacitors 20 and 20 'are not used, the oscillator output and the preceding voltage are connected in series. Is dangerous when a current flows. Therefore, by utilizing the characteristics of a capacitor whose resistance value increases as the frequency decreases, the capacitors 20 and 20 'are inserted to attenuate the current in the commercial power supply frequency band, thereby enabling safe measurement.

The current i flowing through the ground 8 'of the overhead suspension line 2
₁ is 2 mA * B / (A + B), and the current i ₂ flowing to the ground 8 _{i + 1} of the other user's house 5 ′ is ₂ mA * A / (A + B). Normally, ground resistance A <ground resistance B, and ground resistance D
Is usually several hundred ohms. Ground resistance B of the user's house 5
If is low, remove the ground wire of the protector 6. In the figure, the removed state is indicated by a cross. If the grounding resistance B is sufficiently larger than A, the cable 4 _{i + 1} to another user's house
The current flowing through becomes closer to zero.

As in the case of FIG. 1, even when there are a plurality of other user homes, the indicated value of the clamp type
The cable closest to the mA can be said to be the cable 4 _i to the user home 5.

[0030]

[Embodiment 3] FIG. 3 shows another configuration example for carrying out the method of the present invention. FIG. 3 shows a configuration in which a determination is made when a strand (suspension line) ground is used.

In FIG. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals. Reference numeral 16 denotes a strand (suspension) ground, which removes the strand ground 16 connected to the protector 6 and connects the ground side of the oscillator 7. In this state, when a commercial power supply is used as shown in FIG. 2, the current is distributed to other paths.
The resistance from the coaxial outer conductor of _i to the strand ground 16 is at most several tens of ohms, and almost no current flows through other coaxial cables.

In general, when it is difficult to secure the ground directly below the protector, such a connection is made. Even if the strand ground 16 is temporarily removed in front of the protector 6 to perform the measurement, communication is affected. There is no. In the figure, the removed state is indicated by a cross. In this case, the current can flow without passing through the ground resistance, so that the output load resistance of the oscillator 7 becomes close to 0 ohm.

[0033] Thus, except the appropriate cable little current dispersion, it is possible to identify the coaxial cable 4 _i to more securely the user's home. However, since there is a possibility that the oscillator may be damaged due to a load short circuit, it is necessary to use a device having output protection.

[0034]

[Embodiment 4] FIG. 4 shows another configuration example for carrying out the method of the present invention. FIG. 4 shows a means and a state for determining when there is a steady leakage current. As shown in Fig. 4, by using an AC signal oscillator capable of intermittent output and a clamp-type leak meter with reduced sensitivity in the commercial power frequency band, the cable can be reliably identified even when leakage current exists. Make it possible.

In FIG. 4, the same components as those in FIGS. During rainfall, etc., the leakage current from the power line laid on the telephone poles 1
, And may reach nearly 100 mA at the maximum, and it is difficult to determine a current of about 2 mA.

Therefore, the output of the oscillator is intermittently operated, and the variation can be observed by observing the fluctuation. The resolution of a commercially available leak meter is 0.1 in the 200 mA range even for inexpensive ones.
mA, and it is sufficiently possible to read a variation of 2 mA to 10 mA. For example, the leakage feedback current is 80m
A, the case where the leakage current in the user home 5 is 3 mA and the current when the output of the oscillator 7 is ON is 2 mA will be described. '200 ohm resistance value A, the grounding resistance 10' grounding resistor 9 when the the 500 ohm resistance value B, when the output ON, the current i ₁ flowing to the ground 8 of the overhead catenary 2 '(2 mA + 80 mA
−3 mA) * B / (A + B) = about 56.4 mA, and the current i ₂ flowing to the ground 8 _{i + 1} of the other user's house 5 ′ is ( ₂ mA + 8
0 mA−3 mA) * A / (A + B) = approximately 22.6 mA, which is larger than the measured value of the original cable of 5 mA, and cannot be determined by a normal method.

However, by interrupting the oscillator 7, when the output is OFF, the current i ₁ flowing to the ground 8 'of the overhead suspension line 2 is about 55 mA, and flows to the ground 8 _{i + 1} of the other user's house 5'. The current i ₂ is about 22 mA, which is 3 mA for the original cable. When this is compared as the difference at the time of ON, the difference of the current i ₂ flowing to the ground 8 _{i + 1} of the other user's house 5 ′ is about 0.6 mA, and the difference is 2 mA in the original cable, so that it is possible to determine. Become.

Even when there are a plurality of other user's homes, the cable having the largest difference between the indicated values of the clamp type leak meter 11 can be said to be the cable 4 _i to the user's home 5.

In consideration of the reaction speed of the leak meter 11, the stability against the load of the oscillator 7, and the visibility, the ON / OFF is automatically repeated at intervals of 1 second to 10 seconds, so that even a single worker can perform the discrimination work. Can be performed.

Also in this case, by providing a circuit for attenuating the commercial power supply frequency signal shown in FIG. 5 on the output side of the AC signal source 7, it is possible to prevent the leakage current from flowing through the AC signal source 7. And safe measurement, and prevents the value of steady-state leakage current from changing due to fluctuations in the internal impedance of the AC signal source 7 due to oscillation output adjustment and intermittent oscillation output, thereby affecting the measured value. I do.

In the circuit of FIG. 5, the resistance between the output terminals 21 and 22 in the commercial power frequency band is
When 0 and 20 'are not used, the resistance value of the variable resistor 19 for adjusting the output level changes depending on the resistance value, which causes the steady-state leakage current to fluctuate and the measurement value to become inaccurate.
There is a possibility that the circuit will flow a leakage current. Therefore, by utilizing the characteristics of a capacitor whose resistance value increases as the frequency decreases, the capacitors 20 and 20 'are inserted to attenuate the current in the commercial power frequency band, thereby enabling safe measurement.

Further, by slightly modifying the amplification section of a commercially available clamp-type leak meter and using a measuring instrument which suppresses the reaction in the frequency band of the commercial power supply, it is possible to perform the detection more reliably. You can also.

In the above embodiment, the case where the user is at the user's home has been described. However, the user may be at a factory or a store, and the underground cable may be replaced with an underground cable instead of the overhead cable and the pole transformer. A terrestrial transformer may be used, and it is difficult to determine whether or not the cable is a cable to the user's home at a connection point of a single cable, not limited to a portion where wiring is gathered (a plurality of cables are connected to the user's house). If the cables are bundled and pulled toward the user's home, and the connectors of each cable are at a short distance, etc.), the cable may be used to confirm whether the cable is for the user's home, Obviously, changes can be made without departing from the spirit of the invention.

[0044]

According to the present invention, the coaxial cable can be compared without using a complicated dedicated measuring instrument and without installing a device for detection in advance. For this reason, it is possible to reduce the possibility that another user's cable is accidentally disconnected during the contrast operation.

When performing the control work, there is no need to remove the cable, and there is no need to interrupt the service.
That is, the coaxial cable can be compared even during operation.

Even in a place where it is difficult to secure the ground, it is possible to perform a cable contrast operation by using the configuration shown in FIGS.

It is possible to use an AC signal source that performs intermittent output,
By using a current detection device with reduced sensitivity in the commercial frequency band, it is possible to perform cable contrast work even when there is a leak current.

[0048] Even a single operator can reliably identify the cable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example for implementing a method of the present invention.

FIG. 2 is a diagram showing an example of a configuration for implementing the method of the present invention in an environment with insufficient grounding.

FIG. 3 is a diagram showing a configuration example for implementing the method of the present invention when a strand (suspension wire) ground is used.

FIG. 4 is a diagram showing an example of a configuration for implementing the method of the present invention that can be determined even when a steady leakage current flows.

FIG. 5 is a diagram showing a configuration example of a circuit for attenuating a commercial power frequency signal according to the present invention.

[Explanation of symbols]

1, 1 'telephone pole 2 overhead suspension line (steel wire) 3 distributor 4 trunk coaxial cable 4 ₁ , 4 ₂ , ... coaxial cable to user's house 4 _i coaxial cable to the user's house to be contrasted 5 user's house 5 'other user's home 6 protector for the user's home, 6' protector 7 oscillator 8, 8 for other users house ', 8 _0, 8 _i, between 8 _{i + 1} ground 9 oscillator 7 and ground 8 grounding resistor 9 'overhead catenary 2 and ground 8' ground resistance 10, 10 'protector 6,6' and ground 8 _i, 8 _{i + 1} ground resistance 11 clamped leak meter between 12 noise filter 13 between Condenser 14 Pole-mounted transformer 15 Power outlet of earth leakage breaker 16 Strand (suspension line) ground 17 Capacitor 18 Resistance 19 Variable resistor for output level adjustment 20, 20 'Capacitor 21, 22 Output terminal A, B, C, D Resistance value i ₁ Current flowing to ground 8 'of overhead suspension line 2 i ₂ Current flowing to ground 8 _{i + 1} of other user's house 5' X Connection point of oscillator 7 Y Collective part of cable Z Built-in noise filter 12 Mid point of condenser 13

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukinori Uekusa 1-3-1 Gotenyama, Musashino-shi, Tokyo NTT Advanced Technology Co., Ltd. (72) Inventor Shinobu Mego Chiyoda-ku, Tokyo 2-2-2, Otemachi F-term within NTT Corporation (reference) 2G014 AA08 AB34 AC07

Claims (7)

[Claims] In a communication wiring configuration using a coaxial cable, an AC signal source is connected between an outer conductor and a ground at the end of the coaxial cable to a user, and flows through each coaxial cable at a collective portion or a connecting portion of the coaxial cable. A method for comparing coaxial cables, comprising detecting an electric current and judging a coaxial cable having the largest electric current as a coaxial cable to the user. 2. When connecting the AC signal source between the outer conductor at the end of the coaxial cable to the user and the ground, the ground is connected to the ground of the transformer via the middle point of the capacitor with the built-in common mode noise filter of the commercial power supply. The method according to claim 1, wherein the connection is performed. 3. The method according to claim 2, wherein a circuit for attenuating a commercial power frequency signal is provided at an output portion of the AC signal source. 4. The coaxial cable control method according to claim 1, wherein the AC signal source is connected to a strand ground when connecting between the outer conductor and the ground at the end of the coaxial cable to the user's house. 5. The coaxial cable according to claim 1, wherein an AC signal source having a ground resistance serving as a load of about 0 ohm to 3 kohm in a frequency band of about 1 KHz to 10 KHz is used. Method. 6. An AC signal source which performs intermittent output for about 1 to 10 seconds is used.
A method for contrasting the described coaxial cable. 7. The method according to claim 1, wherein the current is detected by using a current detecting device having reduced sensitivity in a commercial frequency band.