JPH0870269A - Method for measuring fault location of instantaneous unbalance occurred in communication balanced line - Google Patents

Abstract

PURPOSE: To easily determine a fault location with high accuracy independently of a distance of the fault location by using a propagation time of a reflected pulse whose propagation time is minimum among plural pulses thereby measuring the location where an unbalance fault takes place. CONSTITUTION: A communication line reaches a telephone set terminal 10 from an exchange 2 through an underground cable 3, an overhead cable 7, and a leading line 9, and the underground cable 3 is connected at underground connection point 5, and the overhead cable 7 is connected at overhead connection point 8. When the location at which an instantaneous unbalance fault takes place is measured at an underground connection point 5 or an overhead connection point 8, pulses are sent continuously for a shorter period than the occurrence time length of the unbalance fault caused instantaneously to obtain plural reflected pulses appearing on the line on the occurrence of the instantaneous unbalance fault and a propagation time of the reflection pulse whose propagation time is minimum is measured to surely acquire the reflection pulses by the instantaneous unbalance fault and the occurrence location is measured with high accuracy independently of the fault occurrence timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for accurately measuring a fault occurrence position when a momentary unbalanced fault occurs in a balanced communication line.

[0002]

2. Description of the Related Art FIG. 1 is a diagram showing an equipment form of a communication line. 1 is a station building, 2 is a switchboard, 3 is an underground cable, 4 is a manhole, 5 is an underground connection point, 6 is a utility pole, 7 is an overhead cable, 8 is an overhead connection point, 9 is a drop line, and 10 is a telephone terminal. . FIG. 2 is a view of the core wire connecting portion. Reference numeral 31 is a conductor, 32 is an insulating coating, and 33 is a twisted portion.

As shown in FIG. 1, the communication line extends from an exchange 2 to a telephone terminal 10 through an underground cable 3, an aerial cable 7 and a service line 9, while the underground cable 3 is connected to an underground connection point 5 and the aerial cable 7 is They are connected at a virtual connection point 8. At the underground connection point 5 and the aerial connection point 8, the conductors forming the communication line are connected by a connector in recent years, or a method of connecting by soldering after twisting a hand is adopted. The connection shown in Fig. 2 is made only with a simple twist (without soldering), and a large amount of such equipment still remains. At the connection point which is only twisted by hand, the surface of the conductor is oxidized for a long time and an oxide film having a large direct current resistance is partially formed. If the twist connection is loose, such as the number of twists is small, the connection point will momentarily become conductive through the oxide film due to vibrations when the vehicle is running or when the underground connection point 5 is dismantled, and the DC resistance will change instantaneously. An increasing phenomenon occurs. The instantaneous increase in DC resistance may reach from several Ω to several MΩ.
The duration is generally within several tens of ms.

This instantaneous increase in DC resistance is extremely unlikely to occur simultaneously in two conductors forming a communication line, and therefore the line is generally momentarily unbalanced. When the instantaneous imbalance due to such an increase in DC resistance occurs in a digital line which has been increasing in recent years, there is a problem that a data error occurs and the communication quality is deteriorated. Since the above-mentioned phenomena are generally concentrated in a particular loose connection point, the position of such a connection point is measured and searched, and the solder is lifted. The need to do so is increasing.

An example of a conventional technique for measuring the occurrence position of a momentary unbalanced fault will be described with reference to FIGS. FIG. 3 shows a measurement circuit configuration diagram. 11 is L1 core wire, 12 is L2
The core line. The conductor 11 and the conductor 12 form a balanced line. 13
Is a resistance for measurement, and 14 is a DC resistance that appears instantaneously, which is a problem here. Points a, b, c, and E respectively indicate terminals on the measurement end side. In addition, FIG. 4 shows the relationship between the instantaneous fluctuation waveform of the DC resistance and the measured waveform. Indicates a momentary fluctuation waveform of DC resistance ,, a pulse waveform sent between terminals a and b, and a vertical voltage waveform appearing between c and E. Further, indicates the case where the transmission pulse occurs when the DC resistance changes, and indicates the case where the DC resistance fluctuation starts in the middle of the transmission pulse.

When the transmission pulse occurs when the DC resistance changes as shown in (3), the propagation time t of the reflected pulse appearing in the vertical line corresponds to the round-trip propagation time from the cable end in the station to the unbalanced fault occurrence position. Because of this, it is possible to measure the exact momentary imbalance fault location. However, when the DC resistance fluctuation starts in the middle of the transmission pulse as in, the propagation time is measured as t + tg, so the propagation time includes an error tg, and the exact momentary imbalance fault occurrence position is measured. You cannot do it. As described above, the conventional instantaneous unbalanced fault position measurement method may have an error in the propagation time depending on the generation timing of the instantaneous unbalanced fault and the transmission timing of the measurement pulse, and thus the accurate unbalanced fault position may be detected. There was a drawback that the position could not be measured.

As a method of reducing the measurement error tg, a method of reducing the pulse width of the transmission can be considered. However, if the pulse width of the transmitted pulse is made small, the level of the reflected pulse becomes small in a long-distance momentary imbalance fault due to the attenuation of high-frequency components during the pulse propagation, and it is lost in the noise. Becomes difficult. Therefore, there is a performance disadvantage that the position where the unbalanced failure occurs cannot be measured. That is, if the pulse width is increased in order to facilitate the measurement up to a long distance, the error tg is increased accordingly and the measurement error is also increased. Conversely, if the pulse width is small, the measurement error tg is small and the measurement error tg is high. Although the result can be obtained, there has been a problem that it becomes difficult to measure a long distance.

On the other hand, regarding the pulse repetition period,
First, even if a momentary increase in DC resistance occurs during the pulse generation time, the reflected pulse does not occur and the momentary imbalance fault occurrence position cannot be specified. In other words, in order to capture a short interruption with a short duration with a high probability, it is necessary to shorten the pulse repetition period.As a result, the pulse width must also be shortened. It becomes difficult to measure the balance fault. As described above, it has been difficult with the conventional measurement methods to measure the failure position of a momentary unbalanced failure, which has a short occurrence time and is not reproducible, to a long distance with high accuracy.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of accurately measuring the generation position even at a long distance with respect to a momentary increase in DC resistance which is not known when it occurs and disappears. I am trying.

[0010]

According to the measuring method of the present invention, a pulse is sent to a balanced line for communication composed of two conductors for communication, and a reflection appears in a vertical line composed of the two conductors and ground. In the measuring method of the unbalanced fault occurrence position of the communication balanced line for measuring the occurrence position of the unbalanced fault occurred in the line by measuring the pulse propagation time, the occurrence time of the unbalanced fault instantaneously generated Propagation time of a reflected pulse that minimizes the propagation time among the plurality of pulses by transmitting pulses continuously in a cycle shorter than the length and obtaining a plurality of reflected pulses that appear in the vertical line when an instantaneous imbalance fault occurs. Is used to measure the position of occurrence of the unbalanced fault.

[0011]

According to the present invention as described above, the position of the unbalanced fault occurring in the communication line can be easily and highly accurately determined regardless of the distance.

[0012]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 5 shows the difference between the direct current resistance change and the reflected pulse depending on the measurement pulse transmission timing. If there is no change in resistance like pulse 1, a reflected pulse cannot be obtained,
The reflected pulse can be obtained only when the pulse is transmitted when the resistance changes, such as 2, 3, and 4. Also, t3 and t4 of the reflected pulses 3 and 4 are accurate propagation times from the momentary imbalance fault point, but the propagation time t2 of the reflected pulse 2 is that the momentary imbalance fault occurred during the pulse transmission. Error td due to When a plurality of pulses are transmitted within the duration of the momentary imbalance fault, the propagation time t of the reflected pulse appearing in the vertical line is distributed as shown in FIG. Here, the shortest propagation time is sometimes the correct propagation time from the disconnection point. Therefore, in order to reliably and accurately capture the propagation time of the reflected pulse, it is necessary to appropriately select the repetition period of the transmitted pulse.

It is necessary to shorten the repetition cycle T in order to capture more reflected pulses having no error as shown by 3 and 4 in FIG. 5 even if one instantaneous imbalance failure occurs. on the other hand,
When the repetition cycle is shortened, when the instantaneous unbalanced fault position is distant, the obtained reflected pulse cannot correspond to the transmitted pulse, and the propagation time cannot be accurately obtained. Therefore, the repetition period T needs to satisfy the following relational expression. Tlmax <T <Tid / n where: Tlmax: Propagation time when a momentary unbalanced fault occurs at the farthest point of the line Tid: Duration of momentary unbalanced fault n: Reflection to be obtained within Tid The number of pulses.

For example, if the farthest point on the line is 4 km, Tlm
Under the condition that ax is about 40 μs and Tid is almost several hundreds μs or more, considering that as many reflection pulses as possible without error are captured, the repetition cycle T is optimally 40 μs in this case.

As described above, a plurality of reflected pulses appearing on the vertical line when a momentary imbalance fault occurs by continuously transmitting pulses at a cycle shorter than the time length of the momentary imbalance fault occurrence. By measuring the propagation time of the reflected pulse that minimizes the propagation time, the reflected pulse due to a momentary unbalanced failure can be reliably captured, and its position can be measured with high accuracy regardless of the failure occurrence timing. There is an advantage that can be done.

The accurate propagation time of the reflected pulse from the instantaneous imbalance fault position is ts, and the pulse width of the transmitted pulse is Tw.
(FIG. 5), the propagation time t is ts <t <ts + T depending on the DC resistance change and the timing of sending the measurement pulse.
It is distributed in the range of w. However, as described above, if it is possible to capture multiple error-free reflected pulses (shortest propagation time) during the duration of a momentary unbalanced fault, it is possible to obtain high accuracy even when measuring with a wide pulse width allowed within the repetition period. Can be measured.

As an example, using an experimental line with a momentary unbalanced fault position of 1 km and a momentary unbalanced fault duration of 1 ms, the propagation time of the reflected pulse was measured when the pulse width was 10 μs and 40 μs. 7a and 7b. In this experiment, we measured 20 times in order to clarify the distribution range and the shortest propagation time, but the number of times other than the shortest propagation time is distributed even if there is only one momentary imbalance fault. Therefore, the shortest propagation time does not change.
Even if the pulse width TW is expanded, the shortest propagation time can be used to identify the position of the momentary imbalance fault occurrence. This means that according to this method, it is not necessary to reduce the pulse width of the transmitted pulse in order to achieve high accuracy, and the widest possible pulse width can be used within the repetition period. It also has the great advantage that it enables highly accurate position measurement even for momentary imbalance faults in distance.

[0018]

As described above, according to the present invention,
(1) Since pulses are continuously transmitted in a cycle shorter than the occurrence time length of a momentary imbalance fault, at least two or more reflected pulses can be captured when a momentary interruption occurs. 2) Since the shortest propagation time of the multiple pulses appearing in the vertical line is used, accurate measurement can be performed regardless of the pulse width to be sent. (3) Since the pulse width can be increased, it can be used over long distances. There is an effect that measurement is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an installation form of a communication line.

FIG. 2 is a diagram of a core wire connection portion.

FIG. 3 is a diagram showing a measurement system.

FIG. 4 is a diagram showing a DC resistance fluctuation waveform and a transmission pulse and a reflection pulse.

FIG. 5 is a diagram when there are a plurality of transmission pulses in the DC resistance fluctuation waveform.

FIG. 6 is a diagram showing a distribution of propagation time.

FIG. 7 is a propagation time histogram.

[Explanation of symbols]

 1 station building 2 switcher 3 underground cable 4 manhole 5 underground connection point 6 utility pole 7 aerial cable 8 aerial connection point 9 lead-in wire 10 telephone terminal 11 L1 core wire 12 L2 core wire 13 resistance 14 direct current resistance 31 conductor 32 insulation coating 33 hand twist Department

Claims (1)

[Claims] 1. A pulse is transmitted to a communication balanced line composed of two conductors for communication, and a propagation time of a reflected pulse appearing in a vertical line composed of the two conductors and the ground is measured, whereby In the method of measuring the unbalanced fault occurrence position of the communication balanced line for measuring the occurrence position of the unbalanced fault that occurred in the line, continuously pulse at a cycle shorter than the time length of the momentary unbalanced fault occurrence. A plurality of reflected pulses appearing in the vertical line when a momentary unbalanced fault occurs are transmitted, and the occurrence position of the unbalanced fault is determined by using the propagation time of the reflected pulse having the smallest propagation time among the plurality of pulses. A method for measuring an instantaneous unbalanced fault occurrence position of a balanced line for communication, which is characterized by measuring.