JP2002005984A - Identification method for accident point and accident phase line in power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems in a conventional accident point identification method, in which a sufficient detection level cannot be secured for a system having multiple branches and a large number of installed apparatuses because of great incident pulse attenuation and a reflection wave from an accident point cannot be determined among various reflection waves. SOLUTION: A pulse having a width wider than a time for reciprocating propagation of an incident wave through a measurement line is propagated as an incident wave 1 to an accident phase line 3, and a reflection wave 2 is obtained in an accident point 4. The polarity of the reflection wave 2 is reversed if an impedance in the accident point is higher than that of the line 3, and the reflection wave is propagated in the opposite direction so as to be overlapped to the incident wave consequently, and form then on, turned into a reflection wave 5 increasing in a level. In a sound phase fine in which no accident is caused, the reflection wave is propagated in the same way as the incident wave, so that the accident point can be identified easily from a time difference between a current increment starting point and an incident point when a differential current waveform between the current waveforms of the accident phase and the sound phase detected in the incident point is found, and consequently, high detection accuracy can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of locating a fault point and a fault phase line in a power system, mainly a high-voltage distribution system.

[0002]

2. Description of the Related Art In locating a fault point of a cable, focusing on the fact that impedance changes at the fault point, limiting the line in which the fault has occurred, applying a high-frequency pulse from one end of the cable, There is a pulse radar method for calculating an accident point from the difference between the arrival times of reflected waves generated at the accident point and the accident point.
Also, in systems with many branches and many installed devices, such as overhead insulation lines, high DC voltage is incident on the line, and the current flowing into the accident point at each point (branch point, etc.) is measured. There is a method of sequentially tracking the fault point while checking the presence or absence of the current or the direction of the current.

[0003]

According to the pulse radar method using high-frequency pulses, as shown in FIG. 6 (a), when the method is carried out in a system in which a large number of branch units 6 and installation equipment, for example, transformers 7, are installed. The detection level of the reflected wave from the accident point cannot be secured due to the attenuation at the branch and the large attenuation due to the transformer. FIG. 6B shows this state, in which the incident waves A,
The reflected wave B from the branch, the reflected wave C from the transformer, and the reflected wave D from the accident point gradually attenuate and the detection level decreases, and the reflected wave from the accident point is determined from these reflected waves. Can not. For this reason, this method cannot be used in a branch line or a section where equipment is installed. On a line with many branches and many devices installed, a method of applying a high DC voltage to the line and measuring the current level sequentially at each location to locate the fault point is used. With the work of ascending poles, the exploration takes a long time and the recovery is delayed. Further, when the fault point has a high impedance due to disconnection, there is a problem that the fault point cannot be located because no current flows. The present invention solves the drawbacks of the prior art, and provides a novel method that can detect a reflected wave generated at an accident point by a pulse radar method even on a line with many branches and many installation devices, thereby shortening an accident recovery time. The purpose is to do.

[0004]

According to the present invention, in an accident point locating method using a pulse radar method, a pulse whose width is set to be equal to or longer than a time required for an incident wave to reciprocate propagate on a measurement line is detected at an incident point. By providing the differential current waveform from the current waveforms of the fault phase and the healthy phase and obtaining the reflected wave at the fault point from the differential current waveform, a method is provided for easily locating the fault point even on lines with many branches and many installed equipment. Is what you do. Here, the measurement line is a line to be measured on which a pulse is incident. In the case of a three-phase line, a pulse is incident on each phase line. A line that is not present is called a healthy phase line, a current waveform detected on the fault phase line is called a fault phase current waveform, and a current waveform detected on the healthy phase line is called a healthy phase current waveform. Although various shapes of the pulse are conceivable, a shape that rises at a constant gradient is preferable. According to the fault point locating method of the present invention using the pulse, the differential current waveform starts to change continuously from the time when the reflected wave is generated at the fault point. For this reason, the distance D to the fault point is determined by calculating the time difference Δt between the incident point and the point where the differential current waveform starts to change continuously, where k is the propagation speed of the incident wave on the measurement line. , Can be easily obtained from the following equation. D = (△ t / 2) · k In particular, in a system with many branches, the sensitivity can be easily improved by increasing the pulse gradient. Also, by setting the pulse width to be equal to or longer than the time during which the incident wave reciprocates in the measurement line, that is, equal to or longer than the time during which the incident wave is reflected at the end of the measurement line and returns to the incident point, the phase of each phase line is reduced. The current level of the reflected wave detected at the point of incidence can be easily distinguished between the fault phase and the sound phase because a large difference occurs between the fault phase and the sound phase after the time when the wave propagates back and forth through the measurement line,
The accident phase track can be located.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an incident pulse used in the present invention.
The width is set to be equal to or longer than the time during which the incident wave propagates back and forth through the measurement line. The pulse shown in FIG. 1 is shown as a measurement line as shown in FIG.
When the incident wave 1 is incident from the incident point, the incident wave 1 propagates through the fault phase line 3, but when it reaches the fault point 4, it is reflected here, propagates in the opposite direction to the incident wave, and returns to the incident point. At this time, when the fault point is in the ground state, the reflected wave 2 is the incident wave 1 because the impedance at the fault point is lower than that of the measurement line.
Has the opposite polarity and propagates in the opposite direction, and as a result, is superposed with the same polarity as the incident wave 1. FIG. 2B shows this state. Assuming that the time for the incident wave to reciprocate between the incident point and the accident point is Δt, the reflected wave at the accident point is superimposed on the incident wave after a time (Δt / 2), and thereafter has a constant gradient depending on the shape of the incident pulse. And the superimposed reflected wave 5 is further increased. Pulse wave 1 indicated by a dotted line in FIG.
Indicates an incident wave propagating through the measurement line when no accident occurs. The reflected wave returning to the point of incidence is detected as a current waveform, the one detected on the faulty phase line where the fault occurred is used as the fault phase current waveform, and the one detected on the healthy phase line where no fault has occurred is detected as the faulty phase. Assuming the current waveform, the difference current waveform is as shown in FIG. The differential current waveform detected at the incident point is a waveform that rises at a constant gradient after a time Δt from the incident point. Therefore, assuming that the propagation speed of the incident wave on the measurement line is k, the distance D from the incident point to the accident point is D
Is determined by D = (△ t / 2) · k. Since the reflected wave at the fault point obtained from the differential current waveform in FIG. 3 has a shape rising with a constant gradient, the reflection start point, that is, the fault point may be obtained as the current increase start point, and the detection is easy. Accident points can be located with high accuracy.

When a branch is present in the measurement line, the level of the differential current waveform is reduced at the branch point because the transmission level of the reflected wave from the accident point is attenuated together with the transmission level of the incident wave, but the gradient of the incident pulse is reduced. By increasing the value, the detection level can be easily improved. If a transformer is present on the measurement line, the impedance of the transformer is low in the high-frequency region (several tens of kHz or more), so the attenuation of the high-frequency component is large, and the level attenuation of the change start point of the reflected wave at the accident point is large. Nevertheless, the level after that is large, and a high reflection level can be obtained. Further, after the high frequency component is impaired by the first transformer, the attenuation of the level of the change start point of the reflected wave at the accident point due to the influence of the second and subsequent transformers becomes small. Therefore, the orientation error does not change significantly. In addition, the location error can be reduced by subtracting a constant value from the measured value Δt in consideration of the influence of the first transformer or by estimating the propagation speed used for calculating the fault point late.

Next, a method for locating a faulty phase line will be described with reference to FIG. FIG. 4A shows a level change with time of an incident wave propagating in the fault phase line.
The pulse wave shown in FIG. 1 incident from the incident point S is reflected at the accident point F and superimposed on the incident wave, and the level increases, and further increases at a constant gradient with time. Since the width of the incident pulse is set to be equal to or longer than the time for the incident wave to reciprocate in the measurement line, the level continues to increase even after the time for the incident wave to reach the end T of the measurement line elapses. On the other hand, FIG. 4 (b) shows a level change of an incident wave propagating in a sound phase line in which no accident has occurred with the passage of time. In this case, the incident wave is constant with time according to the waveform of the incident pulse. It only changes with a gradient, and after the incident wave reaches the end T of the measurement line, the reflected wave is superimposed on the incident wave. However, the reflected wave has the same polarity as the incident wave and is in the opposite direction, and as a result, the level of the superimposed reflected wave does not increase. Therefore, comparing the current waveforms of the accident phase and the healthy phase detected at the incident point,
Since the detection level after the time when the incident wave travels back and forth between the incident point and the end of the measurement line greatly differs, the current waveforms of the fault phase and the sound phase can be easily distinguished, and the fault phase line can be located. . In the above example, the case where the impedance at the fault point is low is described.However, when the fault point is in a high impedance state due to disconnection, it is considered that the detection level of the current waveform in the fault phase decreases due to the reflected wave at the fault point. Can be handled. That is, if a difference current waveform is obtained, in this case, a continuous decrease start point is an accident point.

The incident pulse has the shape shown in FIG. 1, a sine square wave shown in FIG. 5A as a monotonically rising pulse, a rising waveform shown in FIG. 5B as a saturated waveform, and a pulse shown in FIG. FIG. 5 (c) combining (a) and (b)
5D, or a pulse having a waveform having a constant value after rising in the order of μS as shown in FIG. 5D.

[0009]

According to the present invention, the following remarkable effects are obtained. 1. The start point at which the incident wave reflects at the fault point can be easily located as the start point of a continuous change from the differential current waveform obtained from the detected current waveforms of the fault phase and the sound phase, so that high positioning accuracy can be obtained. 2. Since the detection sensitivity can be easily improved by increasing the gradient of the incident pulse, the fault point can be located even on a line with many branches and large loss. 3. Since there is only one discontinuous point, for example, a rising point where the pulse shown in FIG. 1 rises with a constant gradient, the transformer is less affected by the transformer, and high positioning accuracy can be secured. 4. By setting the pulse width to be equal to or longer than the time during which the incident wave propagates back and forth in the measurement line, the fault phase line can be easily located.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing an example of an incident pulse used in the present invention.

FIGS. 2A and 2B are diagrams for explaining an accident point locating method according to the present invention; FIG.
FIG. 4B is a diagram showing that an incident wave becomes a reflected wave of the opposite polarity at the fault point, and FIG. 4B is a diagram showing that the incident wave is superimposed on the reflected wave at the fault point and the level increases after the fault point.

FIG. 3 is a view showing a differential current waveform obtained from current waveforms of an accident phase and a healthy phase.

4A and 4B are diagrams showing a level change of an incident wave propagating in each phase line, wherein FIG. 4A is a diagram showing an accident phase line and FIG. 4B is a diagram showing a healthy phase line.

FIG. 5 is a diagram showing another example of an incident pulse used in the present invention.

FIGS. 6A and 6B are diagrams for explaining fault point localization by a conventional pulse radar method, wherein FIG. 6A shows that an incident pulse is reflected at each point, and FIG. 6B shows each point detected at the incident point; FIG. 5 is a diagram showing reflected pulses and their levels.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incident wave 2 Reflected wave 3 Fault phase line 4 Fault point 5 Reflected wave superimposed on incident wave 6 Branch part 7 Transformer A Incident wave B Reflected wave from branch point C Reflected wave from transformer installation point D Fault point Reflected wave from F F Accident point S Incident point T Edge

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akio Sakaba 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Koichi Sato 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture No. Hitachi Cable, Ltd. General Research Laboratory (72) Inventor Kazuo Kotani 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Hitachi Cable, Ltd. General Research Laboratory F-term (reference) 2G033 AA02 AB01 AB05 AC02 AD08 AE02 AF01 AG00 5G047 AA01

Claims (5)

[Claims] A pulse having a width equal to or longer than a time required for an incident wave to reciprocate on a measurement line is incident on the measurement line, and a differential current waveform is calculated from a current waveform of an accident phase detected at an incident point and a current waveform of a healthy phase. An accident point locating method characterized in that an accident point is located by calculating a reflected wave at the accident point from the differential current waveform. 2. A pulse having a width equal to or longer than the time required for an incident wave to reciprocate on a measurement line is incident on the measurement line, and a difference current waveform is obtained from a current waveform of an accident phase and a current waveform of a healthy phase detected at an incident point. An accident point locating method characterized in that an accident point is located by finding a start point of a continuous change in the differential current waveform. 3. The pulse has a rising shape with a constant gradient,
3. The fault point locating method according to claim 1, wherein the incident wave is a pulse having a width equal to or longer than a time required for reciprocating propagation through the measurement line. 4. A pulse having a width equal to or longer than the time required for the incident wave to reciprocate propagate on the measurement line, and the reflected wave detected by the line of each phase after the time the incident wave reciprocates on the measurement line. Accident-phase line locating method that identifies the current waveform of the fault phase by comparing the current levels and locates the fault-phase line. 5. The pulse has a rising shape with a constant gradient,
5. The fault-phase line localization method according to claim 4, wherein the incident wave is a pulse having a width longer than a time required for the wave to propagate back and forth on the measurement line.