JP2014163914A - Accident point orientation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly accurate accident point orientation by reducing an orientation error caused by a bi-potential method.SOLUTION: An accident point orientation device includes: surge arrival clock-time detection parts 113, 114 for approximating, when a surge wave 104 detected at ends A, B of an underground cable 102 exceeds two different thresholds, an intersection between a zero level and a line passing through an intersection between the surge wave 104 and both of the thresholds to a clock-time when the surge wave 104 reaches the ends A, B. Further, an accident point position is oriented by: calculating an accident point position using a difference between surge wave arrival clock-times obtained by the surge arrival clock-time detection parts 113, 114 approximating and using a propagation speed of the surge wave 104 at the underground cable 102; and performing correction processing in accordance with a distance between the calculated accident point position and a given position.

Description

  The present invention relates to an accident point locating device for locating an accident point of a power carrying underground cable.

Conventionally, underground cables have been used to carry electric power underground. The underground cable lays a power cable in a cave or the like and transports the power underground. A cable accident may occur due to dielectric breakdown due to secular change or the like.
Therefore, an accident point locating device having a function of locating a point where the underground cable accident occurs (accident point) has been developed.

In conventional accident location systems, a technique is used to detect surge currents that are generated when dielectric breakdown (ground fault) occurs in the underground cable by means of current sensors arranged at both ends of the underground cable. ing.
When a ground fault occurs in the underground cable, a surge current having a steep rise propagates from the accident point toward both ends of the underground cable. Since this surge current propagates at a speed determined by the structure and material of the underground cable, the surge current reaches both ends of the underground cable by detecting the surge current with current sensors arranged at both ends. By detecting the time difference, the location of the accident point can be determined.

The distance X from a predetermined position (for example, one terminal part) to the accident point is obtained by the following equation (see Non-Patent Document 1).
X = (L−Vs · (T−T _L )) / 2 (1)
Where T is the time difference until the surge current reaches each end of the underground cable (surge arrival time difference), L is the length of the underground cable, Vs is the propagation speed of the surge current in the underground cable, and _TL is This is the difference in transmission time between both optical fibers connecting the photocurrent sensor and the accident point locating device arranged at both ends of the underground cable.

If it is possible to accurately detect the arrival time of the surge current, it is possible to accurately locate the accident point using the above equation (1). However, in practice, the waveform of the surge current propagating through the underground cable becomes dull due to the influence of the skin effect as the propagation distance increases.
Since the time when the photocurrent sensor detects a surge current exceeding a predetermined threshold is recognized as the surge current arrival time (surge arrival time), when such waveform dullness occurs, the surge arrival time is recognized later than the actual time. As a result, there is a problem that the orientation accuracy is lowered.
As a method of more accurately detecting the surge arrival time in order to cope with such waveform dullness, by setting the intersection of the two thresholds and the surge current and the zero level as the surge arrival time. There is a two-potential method for locating an accident point (see Patent Document 1 and Non-Patent Document 2).

FIG. 5 is an explanatory diagram for explaining the two-potential method. In the two-potential method, as shown in FIG. 5, when the surge current 104 exceeds a predetermined first threshold value L1 and then rises as it is and exceeds the next second threshold value L2, these two threshold values L1, L2 and In this method, the intersections K1 and K2 with the surge current 104 are connected to draw a straight line, and the intersection tr between the straight line and the zero level is determined as the surge arrival time. According to the two-potential method, it is possible to make the error smaller than when the time when the first threshold value L1 is exceeded is set as the surge arrival time, and it is possible to reduce the fault location error.
Non-Patent Document 3 describes the behavior when a square wave voltage generated at the ground fault point propagates through the underground cable.

Japanese Patent No. 3527432

Sumitomo Electric No.105, page 11-18, published in October 1971, “Instantaneous fault location method for power cables” Electric Cooperative Research Vol. 34, No. 6, p. 77 “Fault Locator Location Reliability Improvement Measures” Page 55, "Introduction to Progressive Waves" published by Denki Shoin in April 1955

The distance from the accident point to one terminal part A of the underground cable and the distance to the other terminal part B, that is, the distance by which the surge current propagates from the accident point to each terminal part A, B differs depending on the accident point position.
Since the degree of bluntness of the surge current waveform depends on the propagation distance, if there is a difference in the degree of blunting of the surge current waveform at both terminals A and B as shown in FIG. The magnitudes of the errors ε1 (= tr1−t1) and ε2 (= tr2−t2) of the surge arrival times at the terminal units A and B are different.

In order to perform the fault location with high accuracy, it is necessary to detect the surge arrival time difference T in the equation (1) with high accuracy, but (ε2−ε1) in the following equation becomes an error term.
T = tr2-tr1 = t2-t1 + (ε2-ε1) (2)
Here, t1 is the true arrival time of the surge current to the terminal part A, t2 is the true arrival time of the surge current to the terminal part B, tr1 is the arrival of the surge current to the terminal part A calculated by the two-potential method Time, tr2 is the surge current arrival time to the terminal B calculated by the two-potential method, ε1 is an error included in the surge arrival time to the terminal A calculated by the two-potential method, and ε2 is calculated by the two-potential method It is an error included in the surge arrival time at the terminal unit B.

FIG. 7 shows the relationship between the error of the surge current arrival time difference T generated by the two-potential method and the fault point position due to the difference in waveform blunting at both terminals A and B, and the influence of the error of the surge current arrival time difference T on the orientation accuracy. Shown in
As shown in the figure, when the accident point is in the vicinity of the terminal portion A of the underground cable 102, the degree of blunting of the surge current waveform is small at the terminal portion A (A end), but at the other terminal portion B (B end). growing. For this reason, a positive error occurs in the surge arrival time difference T obtained by the two-potential method, and a negative error occurs in the orientation distance from the equation (1).

On the other hand, when the accident point is in the vicinity of the terminal part B of the underground cable 102, the degree of blunting of the surge current waveform is large in the terminal part A but small in the terminal part B. For this reason, a minus error occurs in the arrival time difference T obtained by the two-potential method, a plus error occurs in the orientation distance, and a plus error occurs in the orientation distance from the equation (1).
When the accident point is in the vicinity of the center of the underground cable 102, the degree of blunting of the surge current waveform is about the same for both terminal portions A and B. For this reason, the influence on the arrival time difference T obtained by the two-potential method is offset, and the error of the orientation distance is small.

  The present invention is made by paying attention to the fact that the degree of blunting of the surge current waveform at both terminal portions A and B of the underground cable 102 differs depending on the distance from the terminal portions A and B of the underground cable 102 to the accident point. Therefore, an object of the present invention is to enable highly accurate accident location by correcting so as to reduce an error (location error) caused by the two-potential method when the accident point is localized.

  According to the present invention, when the surge wave detected at one end of the underground cable exceeds two different thresholds, the intersection of the straight line passing through the intersection of the surge wave and each threshold and the zero level is When the first surge arrival time detection unit that approximates the time when the surge wave reaches one terminal unit and the surge wave detected by the other terminal unit of the underground cable both exceed two different thresholds, A second surge arrival time detection unit that approximates the point of time when the surge wave arrives at the other terminal unit, and the first surge arrival time detection; The difference between the arrival time of the surge wave obtained by approximation by the section and the arrival time of the surge wave obtained by approximation by the second surge arrival time detection section and the propagation speed of the surge wave in the underground cable are used. The Accident point characterized by comprising an accident point locating unit for calculating the dead point position and locating the accident point position by performing correction processing according to the distance between the calculated accident point position and the predetermined position An orientation device is provided.

  According to the accident point locating apparatus according to the present invention, it is possible to reduce the locating error caused by the two-potential method, and to perform highly accurate accident point locating.

It is a block diagram of an accident point locating device according to an embodiment of the present invention. It is explanatory drawing for demonstrating operation | movement of the accident point location apparatus which concerns on embodiment of this invention. It is a characteristic view for demonstrating operation | movement of the accident point location apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating operation | movement of the accident point location apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating a two-potential method. It is explanatory drawing for demonstrating generation | occurrence | production of the orientation error by a two-potential method. It is explanatory drawing for demonstrating generation | occurrence | production of the orientation error by a two-potential method.

FIG. 1 is a block diagram of an accident point locating device according to an embodiment of the present invention.
In FIG. 1, a power carrying cable for carrying the power of the generator 101 is constituted by an underground cable 102 and an external cable 103 connected to both sides of the underground cable 102.

A pair of photocurrent sensors 105 and 106 are located at a position a predetermined distance in the longitudinal direction from both end portions A and B of the underground cable 102 (corresponding to both end portions of the sheath of the underground cable 102). It arrange | positions so that the underground cable 102 may be circulated.
Each of the photocurrent sensors 105 and 106 is a sensor that detects a current flowing through the underground cable 102 using the Faraday effect.

One end of the ground wire 107 is connected to the sheath of one end portion A of the underground cable 102, and the other end of the ground wire 107 is grounded through the inside of the photocurrent sensor 105.
One end of the ground wire 108 is connected to the sheath of the other end portion B of the underground cable 102, and the other end of the ground wire 108 is grounded through the inside of the photocurrent sensor 106.
In this way, each of the photocurrent sensors 105 and 106 has a ground wire 107 having one end connected to the terminal portions A and B of the underground cable 102 around which the photocurrent sensors 105 and 106 circulate and the other end grounded. , 108 are passed.

The photocurrent sensors 105 and 106 are connected to the accident point locating apparatus main body 100 via optical fiber transmission lines 109 and 110, respectively.
The accident point locator main body 100 includes a first photoelectric conversion unit (0 / E) 111, a second photoelectric conversion unit 112, a first threshold unit 115, a second threshold unit 116, a first surge arrival time detection unit 113, a second A surge arrival time detection unit 114 and an accident point location unit 117 are provided.

A plurality of optical current sensors 105 and 106, a plurality of optical fiber transmission lines 109 and 110 for guiding output signals of the plurality of photocurrent sensors 105 and 106, and a plurality of optical fiber transmission lines 109 and 110 that are inputted via the plurality of optical fiber transmission lines 109 and 110 The accident point locating device 100 is configured by the accident point locating device main body 100 for locating the accident point based on the output signals of the photocurrent sensors 105 and 106.
The photocurrent sensors 105 and 106 have a function of detecting a current flowing through the underground cable 102 and the ground lines 107 and 108 and outputting an optical signal representing the magnitude of the current. When a ground fault occurs in the underground cable 102, the photocurrent sensors 105 and 106 detect the surge current 104, convert it to a corresponding optical signal, and output it to the optical fiber transmission lines 109 and 110.

Since the current flowing through the ground lines 107 and 108 can be detected by the photocurrent sensors 105 and 106 due to the effect of pulling back the ground lines 107 and 108 (grounding the ground line of the terminal portion through the inside of the photocurrent sensor), the photocurrent sensor It is possible to detect a surge current or a ground fault current between the terminal 105 and the terminal unit A or between the photocurrent sensor 106 and the terminal unit B.
The photocurrent sensors 105 and 106 are arranged in the vicinity of the terminal portions A and B, and the ground wires 107 and 108 are short, so that the photocurrent sensors 105 and 106 are substantially arranged in the terminal portions A and B. As a result, the photocurrent sensors 105 and 106 are arranged in the terminal portions A and B, and are configured to be able to detect current over the entire length of the underground cable 102.

The first photoelectric conversion unit 111 has a function of receiving an optical output signal of the photocurrent sensor 105 via the optical fiber transmission path 109, converting the received optical output signal into an electrical signal corresponding to the optical output signal, and outputting the electrical signal. The second photoelectric conversion unit 112 has a function of receiving the optical output signal of the photocurrent sensor 106 via the optical fiber transmission line 110, converting it to an electrical signal corresponding to the optical output signal, and outputting it.
The first threshold unit 115 stores a first threshold L1 that is a first reference level for detecting the surge current 104, and has a function of outputting the first threshold L1 to the surge arrival time detection units 113 and 114. ing. The second threshold value unit 116 is a second reference level for detecting the surge current 104 and stores a second threshold value L2 higher than the first threshold value L1, and the second threshold value L2 is stored in the surge arrival time detection unit 113, 114.

  The first surge arrival time detector 113 calculates the time (surge arrival time) when the surge current 104 detected by the photocurrent sensor 105 reaches the terminal part A based on the two threshold values L1 and L2 by the two-potential method. have. That is, the first surge arrival time detection unit 113, when the surge wave 104 detected at one terminal portion A of the underground cable 102 exceeds both of two different threshold values L1, L2, the surge wave 104 and each threshold value L1, It has a function of approximating the intersection of the straight line passing through the intersection of L2 and the zero level with the time when the surge wave 104 arrives at one terminal portion A.

  The second surge arrival time detection unit 114 has a function of calculating the surge arrival time when the surge current 104 detected by the photocurrent sensor 106 reaches the terminal portion B by the two-potential method based on the two threshold values L1 and L2. ing. That is, when the surge wave 104 detected by the other terminal portion B of the underground cable 102 exceeds both of two different threshold values L1 and L2, the second surge arrival time detection unit 114 detects the surge wave 104 and each threshold value L1, It has a function of approximating the intersection of the straight line passing through the intersection of L2 and the zero level with the time when the surge wave 104 arrives at the other terminal portion B.

The accident point location unit 117 is based on the difference in surge arrival times obtained by approximation by the first surge arrival time detection unit 113 and the second surge arrival time detection unit 114 and the propagation speed of the surge current 104 in the underground cable 102. Then, the accident point position with reference to a predetermined position (terminal portion A in the present embodiment) is calculated, and the calculated accident point position and the predetermined position (for example, the center position of the underground cable 102 or one terminal portion A) Or, it has a function of locating the accident point position by performing a correction process according to the distance of B).
The first and second surge arrival time detection units 113 and 114, the first and second threshold units 115 and 116, and the accident point location unit 117 can be configured by a central processing unit (CPU), a storage unit, and software. it can.

但し、ｅは方形波電圧ＥがＸ（ｍ）伝搬した後の電圧進行波の電圧値、Ｅは方形波電圧進行波の電圧値、ｖは進行波の伝搬速度、ｔは時間（但し、ｔ＞Ｘ／ｖ）、ｅｒｆは誤差関数である。 The principle by which the accident point locating apparatus configured as described above locates the accident point position will be described.
First, the relationship between the error term of the surge arrival time difference T obtained by the two-potential method ((ε2−ε1) in the equation (2) and the accident point position is analyzed.
(1) Surge current waveform analysis As shown in FIG. 2, the voltage e after propagating X (m) through the coaxial cable composed of the conducting wire and the sheath is as follows. (See Non-Patent Document 3).

Where e is the voltage value of the traveling wave after the square wave voltage E has propagated X (m), E is the voltage value of the traveling wave of the square wave voltage, v is the propagation speed of the traveling wave, and t is the time (however, t > X / v), erf is the error function.

但し、Ｚはサージインピーダンス、ａは導線半径（ｍ）、ｈは導線の地上高（ｍ）、σｃは導線の固有抵抗（Ω・ｍ）、σｅはシースの固有抵抗（Ω・ｍ）、μｃは導線の透磁率（μｃ＝１）、μｅはシースの透磁率（μｅ＝１）である。 Further, the distortion constant σ is expressed by the following equation.

Where Z is the surge impedance, a is the conductor radius (m), h is the ground clearance (m), σc is the conductor resistivity (Ω · m), σe is the sheath resistivity (Ω · m), μc Is the magnetic permeability of the conducting wire (μc = 1), and μe is the magnetic permeability of the sheath (μe = 1).

Equation (3) is expressed by the following equation, where t ′ is the elapsed time starting from the time when the traveling wave reaches point X (t = X / v).

Further, the current value i of the traveling current wave is obtained by dividing the voltage e in the expression (3) by the surge impedance Z, as follows:

Further, when E / Z is replaced with a current value I (= E / Z), the following equation is obtained.

Similarly, the current i is obtained by dividing the voltage e of the equation (5) by the surge impedance Z and the following equation.

The surge current waveform after propagation for a predetermined distance can be obtained from the equation (9). As the propagation distance increases, the degree of the dull rise of the surge current waveform increases. The distortion constant σ is a constant determined by the structure and material of the underground cable. For example, in the case of a 275 kV single-core CV cable (2000 sq), from the structure and material, 6.93 × 10 ^{− 8} can be used.

(2) Analysis of arrival time error by the two-potential method The arrival time errors ε1 and ε2 at the terminal portions A and B obtained by the two-potential method differ depending on the difference in propagation distance from the accident point to both terminal portions A and B. .
The time t until the surge current waveform after propagation of X (m) reaches the threshold value L can be expressed by the following equation. However, erf ⁻¹ is an inverse function of erf.

Here, when the two threshold values are L1 and L2 (L1 <L2), the times t _L1 and t _L2 until the surge current reaches the threshold values L1 and L2 can be expressed by the following equations.

Therefore, a straight line passing through the intersections (L1, t _L1 ) and (L2, t _L2 ) of the two threshold values L1, L2 and the surge waveform can be expressed by the following equation.
i = P · t + Q (13)
However, the slope P and the intercept Q are expressed by the following equations.
_{P = (L2-L1) /} (t L2 -t L1)
Q = L2-P · t _L2

The point of intersection of this straight line with the zero level is the error ε of the surge current arrival time obtained by the two-potential method, and is given by the following equation.

When the errors ε1 and ε2 of the arrival times of the respective surge currents at the terminal portions A and B of the underground cable are obtained by the equation (14), the following is obtained.

In the case of underground cable length = L (m), t1 _L1 and t1 _L2 in the above formula (15) are the above formulas (11), (12), where the distance from the accident point to the terminal portion A is X (m). ). Further, t2 _L1 and t2 _{L2 in the} equation (16) are obtained from the equations (11) and (12), where the distance from the accident point to the terminal part B is (L−X) (m).

Therefore, the error εT of the surge arrival time difference T is expressed by the following equation.

When the error εT in the equation (17) is used, the accident point distance X in the equation (1) becomes the following equation, and (−Vs · εT / 2) becomes an error term due to the two-potential method.

FIG. 3 is an example showing the relationship between the accident point distance X from the terminal part A and the orientation error term (−Vs · εT / 2). The example shown in the figure shows the relationship between the accident point distance and the orientation error term (−Vs · εT / 2) in various CV cables having a cable length of 20 km and 2000 sq.
As shown in FIG. 3, the orientation error by the two-potential method is proportional to the distance from the center point of the underground cable to the accident point.

Therefore, as shown in FIG. 4, a correction value that cancels out the error of the two-potential method caused by the blunting of the surge waveform according to the distance from the center position of the underground cable at the accident point position obtained by the conventional two-potential method. By adding (location error) to the accident point distance, highly accurate accident point location becomes possible.
That is, when the accident point is closer to the terminal part A than the center, the orientation error can be reduced by adding a correction value corresponding to the accident point distance (plus correction). In addition, when the accident point is closer to the terminal part B than the center, it is possible to reduce the orientation error by subtracting (minus correction) the correction value corresponding to the accident point distance.

  The correction process is a process for reducing (preferably zero) the orientation error term (−Vs · εT / 2) in the equation (18), but the speed Vs of the surge current 104 depends on the structure and material of the underground cable. Further, εT is a value related to the two threshold values L1 and L2, as shown in the equation (17). Therefore, the correction processing for reducing the orientation error is performed based on a constant determined by the structure and material of the underground cable 102 and two different threshold values L1 and L2.

  As shown in FIG. 4, the correction value divides the distance from the underground cable center distance to the accident point into a plurality of sections and stores correction values corresponding to the respective sections in the accident point locating unit 117 in advance. The correction value of the section corresponding to the accident point position calculated by the two-potential method is obtained, and the correction value is added to or subtracted from the accident point position, whereby the accident point position is calculated with the correction value. May be corrected (step correction). Further, a relational expression (for example, a straight line expression in FIG. 3) relating the accident point distance calculated by the two-potential method and the correction value is stored in advance in the storage unit in the accident point locating unit 117, and the two-potential method The correction value corresponding to the accident point position obtained by the above is calculated using the above equation, and the correction value is added to or subtracted from the accident point position, thereby correcting the accident point position with the correction value. It may be configured.

The operation when the accident point locating process described above is performed by the accident point locating apparatus according to the embodiment of the present invention will be described with reference to FIG.
In FIG. 1, when a ground fault occurs in the underground cable 102, a surge current 104 proceeds from the point of the accident toward both terminal portions A and B.
The surge current 104 is detected by photocurrent sensors 105 and 106 disposed at both terminal portions A and B. The photocurrent sensors 105 and 106 output an optical signal indicating the magnitude of the surge current 104 as an optical output signal.

The first photoelectric conversion unit 111 receives an optical output signal from the photocurrent sensor 105 via the optical fiber transmission path 109, converts the optical output signal into an electrical signal corresponding to the optical output signal, and outputs the electrical signal.
The second photoelectric conversion unit 112 receives the optical output signal from the photocurrent sensor 106 via the optical fiber transmission line 110, converts it into an electrical signal corresponding to the optical output signal, and outputs it.

  As shown in FIG. 5 and FIG. 6, the first surge arrival time detection unit 113 approximates the surge arrival time of the surge current 104 to the terminal part A by the two-potential method based on the first threshold value L1 and the second threshold value L2. The surge arrival time tr1 is obtained. That is, the first surge arrival time detection unit 113 obtains the intersections K1 and K2 between the surge current 104 detected by the photocurrent sensor 105 and the first threshold value L1 and the second threshold value L2, and the straight line passing through the intersection points K1 and K2 is zero. The intersection with the level is calculated as the surge arrival time tr1.

  Similarly, the second surge arrival time detection unit 114 approximates the surge arrival time of the surge current 104 to the terminal portion B by the two-potential method based on the first threshold value L1 and the second threshold value L2, and the surge arrival time. Obtain tr2. That is, the second surge arrival time detection unit 114 obtains the intersections K1 and K2 between the surge current 104 detected by the photocurrent sensor 106 and the first threshold value L1 and the second threshold value L2, and the straight line passing through the intersection points K1 and K2 is zero. The intersection with the level is calculated as the surge arrival time tr2.

  The accident point locating unit 117 calculates the difference between the surge arrival times tr1 and tr2 obtained by approximation by the first surge arrival time detection unit 113 and the second surge arrival time detection unit 114 and the surge current 104 in the underground cable 102. An accident point position is calculated based on a predetermined position (for example, one terminal portion A) based on the propagation speed, and the accident point position is calculated based on the time difference between the surge arrival times and the propagation speed of the surge current 104. At the same time, using the correction data (for example, the stepwise correction values in FIG. 4 or the relational expression for correction) stored in advance, the calculated accident point position and the predetermined position (for example, the underground cable 102). The position of the accident point is determined by performing a correction process according to the distance of the center position. The accident point location unit 117 outputs information indicating the accident point position to the display device or relay as accident point information. As a result, the orientation error due to the waveform dullness corresponding to the transmission distance of the surge current is reduced.

As described above, the accident point locating device according to the embodiment of the present invention is capable of generating a surge when the surge wave 104 detected at one terminal portion A of the underground cable 102 exceeds two different thresholds L1 and L2. A first surge arrival time detection unit 113 that approximates the time tr1 at which the surge wave 104 arrives at one terminal portion A at the intersection of the straight line passing through the intersection of the wave 104 and each of the threshold values L1 and L2 and the zero level; When the surge wave 104 detected at the other terminal portion B of the cable 102 exceeds two different thresholds L1 and L2, the intersection of the straight line passing through the intersection of the surge wave 104 and each of the thresholds L1 and L2 and the zero level The surge wave 104 obtained by approximating the second surge arrival time detection unit 114 that approximates the time tr2 when the surge wave 104 arrives at the other terminal B and the first surge arrival time detection unit 113. The accident point position is calculated using the difference between the arrival time tr1 and the arrival time tr2 of the surge wave 104 obtained by approximation by the second surge arrival time detection unit 114 and the propagation velocity Vs of the surge wave 104 in the underground cable 102. In addition, the accident point position is determined by performing correction processing according to the distance between the calculated accident point position and a predetermined position (for example, the central position of the underground cable 102 or the terminal portion).
Here, the correction process is a process performed by a correction value that cancels out an error caused by a bluntness of a surge waveform obtained based on a constant determined by the structure and material of the underground cable 102 and the two different threshold values L1 and L2. It can be constituted as follows.

As described above, the accident point locating device according to the embodiment of the present invention has a surge in both terminal portions A and B of the underground cable 102 according to the distance from the terminal portions A and B of the underground cable 102 to the accident point. Focusing on the fact that the current 104 waveform has a different degree of dullness, correction is made so as to reduce the orientation error caused by the two-potential method when the accident point is located, so highly accurate accident point location is possible. .
In the present embodiment, an example of a surge current as a surge wave has been described. However, in the case of a surge voltage as well, highly accurate accident location can be performed by performing correction processing in the same manner.

  The present invention is applicable to an accident point locating device for locating an accident point position of an underground cable by a two-potential method.

DESCRIPTION OF SYMBOLS 100 ... Accident point location apparatus main body 101 ... Generator 102 ... Underground cable 103 ... External cable 104 ... Surge current 105, 106 ... Photocurrent sensor 107, 108 ... Grounding Lines 109, 110 ... Optical fiber transmission line 111 ... First photoelectric conversion unit 112 ... Second photoelectric conversion unit 113 ... First surge arrival time detection unit 114 ... Second surge arrival time detection Unit 115... First threshold unit 116... Second threshold unit 117.

Claims (2)

When the surge wave detected at one terminal part of the underground cable exceeds both two different threshold values, the intersection of the straight line passing through the intersection of the surge wave and each threshold value and the zero level is sent to the one terminal part. A first surge arrival time detector that approximates the time when the surge wave arrives;
When the surge wave detected at the other end of the underground cable exceeds two different thresholds, the intersection of the straight line passing through the intersection of the surge wave and each threshold and the zero level is sent to the other end. A second surge arrival time detector that approximates the time at which the surge wave arrives;
The difference between the arrival time of the surge wave obtained by approximation by the first surge arrival time detection unit and the arrival time of the surge wave obtained by approximation by the second surge arrival time detection unit, and the underground cable An accident point position is calculated by calculating the accident point position using the propagation speed of the surge wave, and performing the correction process according to the distance between the calculated accident point position and the predetermined position. Accident location device characterized by comprising.   The correction process is a process performed by a correction value that cancels an error caused by a dullness of a surge waveform obtained based on a constant determined by the structure and material of the underground cable and the two different threshold values. Item 1. The accident location system.

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