JPH068839B2 - Accident point detection device for overhead distribution line - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an accident point search device for an overhead distribution line, which applies a high voltage pulse to search for a discharge fault point of the overhead distribution line.

[Prior Art] As a conventional fault point search device for an overhead distribution line, there is a device using a "signal arrival direction detection device" disclosed in, for example, Japanese Patent Laid-Open No. 59-68678. This conventional device will be described with reference to the drawings.

Fig. 8 is a block diagram of this accident point exploration device. (1)
Is an overhead distribution line that appears to have a discharge-to-ground fault, (4A)
And (4B) are electromagnetic wave detection antennas for detecting the electromagnetic waves emitted by the current traveling waves propagating on the distribution line (1) from the accident point, and (5) is the receiving device, and the antennas (4A), (4B) )
And are connected respectively. The waveform (I) in the figure is the distribution line.
The first wave of the fault current flowing through (1) is shown.

(9A) and (9B) are absolute value circuits that output positive voltage signals from the antennas (4A) and (4B), and (10A) and (10B) are absolute value circuits (9A) and (9B). Required pulse width Td by signal input of
A monostable multi-vibrator that outputs a single pulse of (1,
1A) and (11B) are NAND circuit elements in which flip-flop circuits are configured by connecting their input / output terminals. (12
A) and (12B) are inverters that invert the signal level of the input signal and output, and (13A) and (13B) are signal indicators.

Next, the operation of the receiving device (5) will be described.

Assuming now that the antenna (4A) receives the electromagnetic wave earlier than the antenna (4B) by a time difference td, first, the voltage signal output from the antenna (4A) is input to the absolute value circuit (9A). The monostable multivibrator (10A) outputs a single pulse having a required time width Td by the signal output from the absolute value circuit (9A). By inputting this single-shot pulse,
The NAND circuit element (11B) is interlocked, and the output signal of the NAND circuit element (11A) is output for the time width Td of the input pulse, and the signal is inverted by the inverter (12A) to display the signal indicator (13A). Illuminates and displays the accident point direction. Subsequently, when the antenna (4B) receives the electromagnetic wave and outputs a voltage signal, the same operation is performed. However, as described above, the NAND circuit element (11B) is replaced by the NAND circuit element (11B).
Since it is interlocked by A), the signal indicator
(13B) is not input and does not light up.

[Problems to be solved by the invention]

However, in the conventional fault point search device for an overhead distribution line configured as described above, in addition to a regular electromagnetic wave in which a current traveling wave propagating from the ground fault point to the distribution line is generated, for example, a nearby factory However, there is a problem in that noises and the like generated when the switch is opened and closed are received and displayed erroneously.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an accident point search device for an overhead distribution line which is less affected by external noise, particularly pulse noise.

[Means for solving problems]

The overhead distribution line fault point search device according to the present invention comprises means for periodically applying a high voltage pulse to the overhead distribution line, an antenna for receiving an electromagnetic wave generated by a current traveling wave from the distribution line fault point, and Time difference signal output means for outputting a signal having a time difference from the output signal of the antenna, and first arrival signal holding means for continuously outputting the first arrival signal among the output signals of the time difference signal output means and blocking the output of the last arrival signal When,
An automatic reset signal generating means for outputting a reset signal for resetting the first-arrival signal holding means, the automatic reset signal generating means being triggered in synchronization with the operation of the first-arrival signal holding means, and the high voltage pulse applying means The reset signal is set to be output after a predetermined time shorter than the high voltage pulse generation period.

[Action]

Since the apparatus for detecting a fault point of an overhead distribution line according to the present invention comprises the above-mentioned means, the first-come-first-served signal holding means is provided by a regular signal input based on reception of an electromagnetic wave generated by a current traveling wave from the fault point of the distribution line. The automatic reset signal generation circuit is triggered in synchronism with the setting of the reset signal, and the reset signal is output a predetermined time before the input of the next regular input signal that is periodically input to the first-arrival signal holding circuit. Is output to reset the first-arrival signal holding circuit.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. The same reference numerals as those in the conventional example indicate the same or corresponding portions. In Fig. 1, (1) is an overhead distribution line that seems to have a discharge-to-ground fault and is in a power failure state. (3) is an accident equipment connected to the unknown point B of this distribution line (1), for example, a discharge ground fault, and (2) is a high-voltage pulse applying means for periodically generating high-voltage pulses ( It is a power supply device) and is connected to the distribution line (1) at a point A, and the distribution line (1) is charged by applying one high-voltage pulse. (4A) and (4
B) is an electromagnetic wave detection antenna that detects an electromagnetic wave generated by a current traveling wave propagating from the accident point on the distribution line (1), and usually uses a loop antenna with an appropriate distance l (m). , For example, they are installed on the roof of the car (7) in series with respect to the traveling direction of the car (7). (8) is the arrival time difference td of the signals received by the pair of antennas (4A) and (4B)
Therefore, it is a receiving device for discriminating the direction of the accident point, which is connected to the antennas (4A) and (4B) via coaxial cables (6A) and (6B), respectively, and is mounted on the automobile (7). The waveform (I) in the figure shows the first wave of the fault current flowing through the distribution line (1).

FIG. 2 is a block diagram of the receiving device (8), and (9) is a time difference signal output means for inputting the output signals of the antennas (4A) and (4B) and outputting a signal having two time differences. In this embodiment, an absolute value circuit (9) that widens an input signal and always outputs a positive voltage signal regardless of the polarity of the input signal (9
It is composed of A) and (9B). (14A) and (14B) are inverters that shape the output signals of these absolute value circuits (9A) and (9B) and invert them at high and low levels to output, and (15) are these inverters (14A). ), (14B) is a first-arrival signal holding means for continuously outputting the first-arrival signal among the output signals of the time difference signal output means (9) and blocking the output of the later-arrival signal. In the example above inverters (14A), (14B)
Of the RS flip-flop which outputs the high level voltage signal from the output terminal Q until it is set by inputting the low level voltage signal of It is composed of circuit elements (16A) and (16B) and a pair of NAND circuit elements (11A) and (11B) that form a flip-flop circuit that receives these output signals as inputs.

(13) is a signal display means for displaying the direction of the accident point. In this embodiment, the signal display means is composed of a signal display (13A), (13B) consisting of an LED element and its protective resistor, etc., and an inverter (12A) or Lights up only when high level voltage is input from (12B). (17) is an automatic reset signal generating means for resetting the first-arrival signal holding means (15),
By inputting the AND circuit element (18) that receives the outputs of the ND circuit elements (11A) and (11B) and the low level voltage signal of this AND circuit element (18), the leading edge of this input signal rises. By inputting the monostable multivibrator (19), which is triggered by the down-link and outputs a single-shot pulse signal of the time width Te, and the output pulse signal of this monostable multivibrator (19), the trailing edge of this input pulse signal rises. It is composed of a monostable multivibrator (20) which is triggered by the downward movement and outputs a single pulse having a time width Tr. (21) is a switch for manual reset, (22) is a switch for this manual reset
(21) and an output signal of the above-mentioned monostable multivibrator (20), which is an AND circuit element.
The output terminal of (22) is connected to the RS flip-flop circuit element.
Connect to (16A) and (16B) reset terminals.

The monostable multivibrator (19) has a variable resistor (23) and a capacitor (24) for arbitrarily setting the time width Te of the output pulse signal, and the monostable multivibrator (20) has an output pulse. A resistor (25) and a capacitor (26) are provided to set the time width Tr of the signal to an appropriate value. In the figure, Vcc indicates the power source of the circuit.

Next, the operation will be described. In Fig. 1, the overhead power distribution line (1) in the power failure state is connected to the high-voltage pulse applying means (power supply device) (2).
When charging is performed by periodically applying a high voltage pulse at and the ground fault is discharged at the fault equipment (3), the ground fault current due to the charge charged on the distribution line (1) flows into the fault point B. The rise of the first wave of the transient current in this ground fault discharge is generally extremely steep, and the distribution line (1) is connected from the accident point B to the voltage application point A.
Direction and the direction C on the side opposite to the voltage application point in the form of a current traveling wave. A car (7) equipped with a pair of antennas (4A) and (4B) and a receiving device (8) goes from the point A to the point C opposite to the point where the point is directly below the overhead distribution line (1). The current that propagates through the distribution line (1) when it is located at an arbitrary point D between the voltage application point A and the accident point B, assuming that it is traveling in parallel along the distribution line (1). When the electromagnetic waves emitted from traveling waves are received by the above antennas (4A) and (4B), the antenna on the accident point B side
(4A) receives first and the other antenna (4B) receives the time difference td.
Just delayed to receive. When the antennas (4A) and (4B) receive the electromagnetic waves when the vehicle (7) is located on the side C opposite to the charging point from the accident point B, the antenna (4
B) receives earlier than the other antenna (4A) by the time difference td. Therefore, of the pair of antennas (4A) and (4B), the direction of arrival of the current advance wave is determined by determining which of the electromagnetic waves emitted by the current traveling wave propagating from the accident point was received first. That is, the direction of the accident point can be detected. Since the direction of the fault point can be detected each time a high-voltage pulse is applied by the above-mentioned voltage applying device (2), the antennas (4A) and (4B) and the receiving device (8) are mounted as described above. If the vehicle (7) runs from the charging point (2) along the overhead distribution line (1) while detecting the direction of the accident point, the antenna that receives the electromagnetic waves first will receive the antenna (4B) rather than the antenna (4B). By changing to (), the ground fault accident point B can be searched.

This operation will be described in detail below with reference to Figs. 2 and 3. Figs. 3 (a) and 3 (c) show the electromagnetic waves generated from the distribution line (1) based on the ground fault discharge at the accident point (3). That is, it relates to a normal signal input, and (b) relates to a noise signal.

First, the case of normal signal input will be described. In this case, it is assumed that the car (7) equipped with the antennas (4A), (4B) and the receiving device (8) is located in the vicinity of the point D between the voltage application point A and the ground fault accident point B. It is assumed that the antenna (4A) receives the electromagnetic wave generated by the current traveling wave propagating through the distribution line (1) from the fault accident point B ahead of the antenna (4B) by a minute time difference td (eg, 10 ns). Then, the above antenna (4A),
Signals such as those shown in A ₀ and B ₀ in Fig. 3 (a) are output from (4B), and the absolute value circuit (9
From A) and (9B), the signals of the same time difference td converted to the positive and positive polarity as shown in Fig. 3 (A) A ₁ and B ₁ are output, and are output by the inverters (14A) and (14B). Fig. 3 (b) A ₂ , B
_The waveform is shaped and inverted as shown in FIG. 2 and input to the respective input terminals of the RS flip-flop circuit elements (16A) and (16B). RS flip-flop circuit element (16A),
(16B) is set by the low level voltage signal input, and holds the input signal by itself and outputs it from output terminal Q of FIG. 3 (a) A ₃ , B ₃
Output a high level voltage signal as shown in, and this signal is N
It is inputted to the AND circuit elements (11A) and (11B), respectively. Since the input signals of these NAND circuit elements (11A) and (11B) have a time difference of td, the NAND circuit (11A) to which the first-arrival signal is input as shown in A ₄ and B ₄ of FIG. There outputs a low-level voltage signal operates, is inverted by the inverter (12A), the signal indicator high voltage signal such shown in FIG. 3 (b) a ₅ constitute a signal display unit (13) ( The signal indicator (13A) lights up to indicate the direction of the accident point. Next, the NAND circuit element (1
Since 1B) is interlocked by the NAND circuit element (11A) which has already been activated by the input of the first-arrival signal, it does not output as shown in B ₄ in FIG. 3 (A) (high level state),
Accordance connexion subsequent signal indicator (13B) are not do not light display input as shown in Figure 3 B _5. The NAND circuit element (11
The output states of (A) and (11B) do not change even if a signal is input again to the respective input terminals of the RS flip-flop circuit elements (16A) and (16B). 16B)
It is held until a reset signal is input to the reset terminal of the.

Next, the operation of the automatic reset signal generating means (17) will be described. To the input terminal of the monostable multivibrator (19),
When the output signals (low level voltage) of the NAND circuit elements (11A) and (11B) are input via the AND circuit element (18),
The monostable multivibrator (19) outputs a pulse signal of a high level voltage having a predetermined time width Te as shown in C ₂ in FIG. 3 (b) C from the output terminal Q at the rising edge of the leading edge of the input signal. The signal is input to the input terminal of the monostable multivibrator (20). This monostable multivibrator
At the trailing edge of the trailing edge of this input signal, (20) outputs a pulse signal of a low level voltage having a time width Tr as shown by C ₃ in FIG. 3 (a) from the terminal.

This signal is input to the terminals of the RS flip-flop circuit elements (16A) and (16B) through the AND circuit (22), and the RS flip-flop circuit elements (16A) and (16B) are reset. The RS flip-flop circuit element (16
The operating time from the set to the reset of (A) and (16B) is determined by the time width Te of the output pulse signal of the monostable multivibrator (19), which is outside the monostable multivibrator (19). It can be set arbitrarily with the attached variable resistor (23). The time width Tr of the output pulse signal of the monostable multivibrator (20) is set to a sufficient time (for example, several ms) for surely resetting the RS flip-flop circuit elements (16A) and (16B). . The RS flip-flop circuit elements (16A), (16B) can be manually reset by operating the switch (21).

Next, a case will be described in which the loop antennas (4A) and (4B) receive external noise due to, for example, opening and closing of electric switches.

Figure 3 (b) monostable multivibrator as shown in C ₂
If the time width Te of the output pulse signal of (19) is set to a time shorter than the regular signal input period by a predetermined time, the noise signal (b) will be output from the loop antennas (4A) and (4B) to the third position. Figure (b) A
It is output as shown in ₀ and B ₀ , and absolute value circuits (9A) and (9B)
Is Zohaba the positive polarity as shown in FIG. 3 (b) A _1, B ₂ by the inverter (14A), FIG. 3, which is waveform-shaped and inverted by (14B) (ii) A _2, B ₂ Even if a signal such as shown in (4) is input to the RS flip-flop circuit elements (16A) and (16B), the RS flip-flop circuit elements (16A) and (16B) are
Figure (b) is A _3, B excisional is in operation by normal input signal as shown in ₃ (b), the output signal of such which does not change, the subordinate connexion annunciator (13A) is displayed erroneously There is no.

That is, RS flip-flop circuit elements (16A), (16A)
Until B) is set by the regular input signal and reset by the output pulse signal of the monostable multivibrator (20), the receiving device (8) is not affected by external noise at all. Therefore, the time width Te of the output pulse signal of the monostable multivibrator (19) is almost equal to or slightly longer than the cycle of the normal input signal, that is, the cycle Tp of the high voltage pulse generation of the high voltage pulse applying means (2). If set to a short predetermined time value, a receiver (8) that is hardly affected by pulsed external noise can be obtained. The above Te is ideally set to the value of the inner ring as close to Tp as possible, but in consideration of the influence of the variation of the high voltage pulse generation period of the high voltage pulse applying means (2) and the like, usually Te = 0.9 to 0.99. It is set to Tp (for example, Tp = 4 sec).

FIG. 4 shows another embodiment. In this embodiment, the first-arrival signal holding means (15) is provided with a pair of reset terminal D type negative edge trigger type flip-flop circuit elements (31A), (31B) (hereinafter D). A flip-flop circuit element) is used to connect each inverting output terminal to the other input terminal D and to use the clock input terminal as an input terminal, and this first-arrival signal holding means (1
In order to expand the time difference of the time difference signal in the previous stage of 5), each pair of monostable multivibrators (10A), (10B) and NAND circuit elements (11A), (11B) that form a flip-flop circuit.
Have been inserted. Furthermore, automatic reset signal generating means (17)
Instead of the AND circuit element (18) in the automatic reset signal generating means (17) in the embodiment of FIG. 2, an OR circuit element (32)
It is configured by using.

FIG. 5 shows time charts in the receiver (8) of the embodiment of FIG. 4, where (a) and (c) relate to a regular input signal, and (b) relate to a noise signal. The feature of the embodiment shown in FIG. 4 is that the absolute value circuits (9A) and (9B) constituting the time difference signal generating means (9) output FIG.
_A small time difference td (for example, 10 ns or less) as shown by B ₁ and B ₁ is output at the fifth stage at the output stage of the NAND circuit elements (11A) and (11B).
As shown in (a) and (b) A ₃ and B ₃ , the time difference Td (for example, several ms) is enlarged, and in the case of a regular input signal, the output signals of these are input to obtain the above D- flip flop circuit element (31A), (31B) is as shown in FIG. 5 (b) a _4, B ₄ actuated by the falling of the leading edge of the input signal,
The purpose is to securely hold the first-arrival signal and block the output of the second-arrival signal. Then, one of the high-level output signals of these D-flip-flop circuit elements (31A) and (31B) is passed through the OR circuit element (32) to the monostable multivibrator (1
By inputting to terminal B of 9), the time width of the output pulse signal of the monostable multivibrator (19) as shown in C ₂ and C _{3 of} FIG. 5 as in the case of the embodiment shown in FIG. Te
(It can be set arbitrarily with the variable resistor (23), and it is set to be short for a predetermined time although it is almost equal to the cycle of the regular input signal.)
After a time corresponding to, the low level pulse signal of the time width Tr is output from the monostable multivibrator (20) to the AND circuit element (22).
Through the D-flip-flop circuit element (31A), (31
It is possible to reset these circuit elements (31A) and (31B) at the same time by inputting them to B) at an arbitrarily set time. Therefore, the noise signal is input and the loop antenna (4
From (A) and (4B), when the signals shown in Fig. 5 (b) A ₀ and B ₀ are output, the NA is the same as in the case of normal signal input.
ND circuit element (11A), FIG. 5 at the output stage (11B) A _3, B
_{Even when} a signal such as ₃ is output, the D-flip-flop circuit elements (31A) and (31B) are in operation and their output states do not change. Therefore, this embodiment is also the embodiment shown in FIG. In the same manner as above, an operation that is not affected by pulsed external noise can be obtained.

FIG. 6 shows still another embodiment, in which the loop antenna (4) is installed such that the normal direction of its antenna surface is perpendicular to the traveling direction of the vehicle (7) in which it is mounted and parallel to the ground. It consists of one antenna. The time difference signal output means (9) outputs the output signal of the loop antenna (4) by amplifying and reversing the polarity of the output signal and outputting the inverted signal by the inversion amplifier (34). A thickening means (33) consisting of an inverse thickener (35) for inverting and outputting, and the above-mentioned inverse thickener
This embodiment differs from the embodiment shown in FIG. 2 in that it is composed of a pair of half-wave rectifying means (36A) and (36B) for half-wave rectifying the output signals of (34) and (35).

In the embodiment shown in FIG. 6, from the accident point (3) to the overhead distribution line (1)
When the electromagnetic wave emitted by the current traveling wave propagating through the loop antenna (4) is received by the loop antenna (4), the polarity of the first wave of the output voltage of the loop antenna (4) is determined by the traveling direction of the current traveling wave. The time difference signal output means (9) inputs the output signal of the loop antenna (4) and determines the direction of the fault point from the polarity of the first wave of the input signal and has a time difference. Of the two signals, the signal corresponding to the fault point direction of the overhead distribution line is output first. That is,
The amplification means (33) inputs the output signal of the loop antenna (4) and outputs two signals having different polarities, and these signals are half-waved by half-wave rectification means (36A) and (36B), respectively. By rectifying and outputting, between these two output signals, it is inevitably 1/2 of the cycle of the output signal of the loop antenna (4).
By utilizing the fact that there is a time difference between the half wave rectification means (36A) if the polarity of the first wave of the output signal of the loop antenna (4) is negative, the half wave rectification means (36A) The time difference signal is output before the rectifying means (36B). Therefore, this receiving device (8) also operates in the same manner as in the case of the embodiment shown in FIG. 2 and obtains the same effect.

Further, FIG. 7 shows another embodiment, and like the embodiment of FIG. 6, the direction of the fault point of the overhead distribution line (1) is determined by the polarity of the first wave of the output voltage of the loop antenna (4). However, the amplification means that constitutes the time difference signal output means (9)
Instead of the inverting amplifier (35) of the amplifier (33) of the embodiment shown in FIG. 6, (33) is replaced by a non-inverting amplifier (37) that only increases the input signal, Moreover, the input terminal of the non-inverted amplifier (37) is connected to the input terminal of the inverted amplifier (34), and the first-arrival signal holding means (15) is a pair of D type positive edge trigger system. Flip flip circuit element (38
A) and (38B) are used to connect each of these inverting output terminals to the other input terminal D, and in addition, the inverters (14A), (14B) shown in FIG. (12
The difference from the embodiment shown in FIG. 6 is that A) and (12B) are omitted.

In the embodiment shown in FIG. 7, the amplifying means (33) has a different structure from the amplifying means (33) shown in FIG. 6 as described above, but the output signal of the loop antenna (4) is input to increase the amplitude. The functions of outputting a pair of signals that are wide and have different polarities are the same, and the half-wave rectifying means (36A) and (36B) provide a time difference equivalent to 1/2 of the cycle of the output signal of the loop antenna (4). The time difference signal having is output. The first-arrival signal holding means (15) is provided with a positive edge trigger type D-type flip-flop circuit element (31
C) and (31D) are different from the embodiment shown in FIG. 4, except that these circuit elements (31C) and (31D) are activated by the rising edge of the leading edge of the input signal. Obviously, it operates as in the case of the embodiment of FIG. The 7th
The receiver (8) of this embodiment shown in the figure is composed of the monostable multivibrators (10A) and (10B) shown in FIG.
The circuit elements (11A) and (11B) are omitted, but this is usually because the time difference between the output signals of the time difference signal output means (9) of this embodiment is relatively large (for example, 100 ns or more), and the first-arrival signal hold This is because it is not necessary to increase the time difference between the input signals in the preceding stage of the means (15). However, the negative edge trigger type D type flip-flop circuit elements (31A) and (31B) are used as the first-arrival signal holding means (15), and the monostable multivibrator (10A), (10B) and NAND are provided in the preceding stage. It can be put to practical use by inserting the circuit elements (11A) and (11B).

〔The invention's effect〕

As described above, according to the present invention, the automatic reset signal is synchronized with the setting of the first-arrival signal holding means by the regular input signal based on the reception of the electromagnetic wave generated by the current traveling wave from the fault point of the distribution line. When the generating means is triggered and the next regular input signal, which is periodically input, is input to the first-arrival signal holding means, a reset signal is output at a predetermined time, which is close to the time when the first-arrival signal holding means is output. Since resetting is performed, it is possible to prevent the problem of erroneous display due to the influence of the pulsed external noise signal, and it is possible to obtain a highly reliable fault point search device for overhead distribution lines.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining the concept of an accident point search device for an overhead distribution line according to the present invention, FIG. 2 is a block diagram showing one embodiment of the accident point search receiver used in the present invention, and FIG. A time chart showing the operation of the input and output ends of the receiving device shown in FIG. 2, and FIGS. 4, 6, and 7 are blocks showing other embodiments of the receiving device for detecting an accident point used in the present invention. 5 and 5 are time charts showing the operation of the input and output ends of the receiver shown in FIG. 4, and FIG. 8 is a block diagram of the conventional receiver. In the figure, (1) is an overhead distribution line, (2) is a high-voltage pulse applying means (voltage-applying device), (3) is a ground fault equipment, (4), (4A), (4B) are loop antennas, ( 8) is a receiving device, (9) is a time difference signal output means, (13) is a signal display means, (15) is a first-arrival signal holding means, and (17) is an automatic reset signal generating means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A high voltage pulse applying means for periodically applying a high voltage pulse to an overhead distribution line in a power failure state to cause a ground fault discharge at an accident point, and an electromagnetic wave generated by a current traveling wave from the accident point of the distribution line. An antenna for receiving, a time difference signal output means for outputting a time difference signal according to the output signal of the antenna, a first arrival signal for continuously outputting the first arrival signal among the output signals of the time difference signal output means, and preventing the output of the last arrival signal. The holding means and the reset signal for triggering in synchronization with the operation of the first-arrival signal holding means and outputting the reset signal for resetting the first-arrival signal holding means after a predetermined time shorter than the high-voltage pulse generation period of the high-voltage pulse applying means An apparatus for detecting an accident point on an overhead distribution line, which is provided with an automatic reset signal generating means set as necessary. 2. A first monostable multivibrator which outputs a pulse signal having a predetermined time width when triggered by a voltage change at a leading edge of an input signal.
The output pulse signal of the second monostable multivibrator is composed of a second monostable multivibrator which outputs a pulse signal triggered by a voltage change at the trailing edge of the output pulse signal of the first monostable multivibrator. The fault point search device for an overhead distribution line according to claim 1, wherein the reset signal of the first-arrival signal holding means is used.