JPH0797125B2 - Positioning method of fault location coil in underground power transmission line - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for locating a fault section locating coil in an underground power transmission line.

[0002]

2. Description of the Related Art A cable constituting an underground power transmission line has a metal sheath such as an aluminum sheath or a wire shield on a cable core. The technique of measuring the current flowing through the wire shield and the like separately from the conductor current is important especially in the method of locating the fault section from the ground fault current distribution at the time of the ground fault.

That is, the ground fault fault section in the underground power transmission line is distributed along the cable (current distribution, phase distribution) of the current flowing in the cable conductor or wire shield (generally, zero-phase current obtained by three-phase synthesis). However, in reality, most of the current flowing through the conductor at the time of an accident flows through the wire shield as a return path, so that a penetration type current transformer (CT) or magnetic field sensor is applied from outside the cable. Even if the measurement is made by (2), the conductor current and the current flowing in the wire shield are combined and offset, which makes effective measurement difficult.

Therefore, conventionally, a current flowing through a wire shield or the like is detected by attaching a CT to a cross bond wire in an insulating connection portion or a ground wire in a terminal portion, or a current flowing in a conductor is detected by a magnetic field sensor attached in the same place. Had been detected.

However, in this method, the detection section is limited. Therefore, recently, there has been proposed a method in which the detection section can be freely set, that is, a method in which the current flowing through the wire shield and the current flowing through the conductor can be detected separately in an arbitrary portion of the cable. that is,
This is a method of detecting a current flowing through the wire shield by picking up a magnetic field in the cable axis direction generated along the twist of the wire shield of a cable forming an underground power transmission line by a detection coil wound around the circumference of the cable.

This method will be described below with reference to the drawings. FIG. 4 is a side view showing a cross section of the upper half portion showing only the mounting portion of the detection coil in order to explain the fault section locating method of the underground power transmission line. That is, cable 1
A wire shield 5 is provided on a cable core 4 mainly composed of the conductor 2 and the insulator 3, and a plastic anticorrosive layer 6 is coated on the wire shield 5. The detection coil 7 is wound directly on the surface of the plastic anticorrosion layer 6 for detection. Since the wire shield 5 is twisted around the cable core 4, not only the magnetic field on the plane orthogonal to the cable but also the axial magnetic field is generated based on the current flowing therethrough. The magnetic field of this axial component is interlinked with the detection coil 7 wound around the surface of the plastic anticorrosion layer 6,
The current flowing through the wire shield 5 is detected.

[0007]

By the way, in such fault location of an underground power transmission line, the phase distribution or absolute value distribution of the zero-phase current obtained by three-phase synthesis of the ground fault currents flowing through the wire shield is used. . In particular, in the case of a cable having an S-Z twisted wire shield, the direction of the axial magnetic field is reversed on the S twist (right twist) and the Z twist (left twist), and its size also changes depending on the position ( S
Therefore, in order to accurately obtain the zero-phase current, it is necessary to clearly determine the mounting position of the detection coil.

However, in the past, there was no suitable means for specifying this mounting position.

The present invention has been made in view of the above circumstances, and provides a new detecting coil position determining means used for fault section localization in an underground power transmission line having an SZ twisted wire shield. With the goal.

[0010]

According to the present invention, the axial magnetic field generated by the twisting of the wire shield of the cable constituting the underground power transmission line is picked up by the detection coil wound around the cable circumference, and flows in the wire shield. In the method of detecting the direction and magnitude of the current, when the wire shield is SZ twisted, a pulsed current is passed through the wire shield and the detection coil is fixed at a position where the output directions are the same, and measurement is performed. It's something that you do.

[0011]

[Practical example] First, the state of the output waveform detected by the detection coil provided on the circumference of the cable due to the twisting of the wire shield of the cable forming the underground power transmission line will be described. In FIG. 5A, the wire shield 5 of the cable 1 is formed in SZ twist. Now, it is assumed that the detection coil 7 is installed on the S twist (right twist) and the detection coil 7'is installed on the Z twist (left twist). Then, when a pulsed waveform current shown in FIG. 5 (b) is applied to the wire shield 5, the polarities of the output waveforms detected by the detection coils 7 and 7'are respectively shown in FIGS. 5 (c) and 5 (d).
As shown in (1), an output waveform with a 180 ° phase shift will be obtained. Therefore, in order to obtain the zero-phase current, it is necessary to fix the detection coils 7 and 7'in such positions that the directions of the singular points of the output waveforms of the respective phases are the same. That is, it is necessary that all the detection coils attached to the cables of each phase are arranged on the wire shield in the same twist direction.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a method for positioning a detection coil according to an embodiment of the present invention. In this figure, the detection coil is positioned in the A phase. First,
The small penetrating transformer 10 is arranged on the cross bond wire 9 of the A-phase insulating connection portion 8. After that, a current having a mark M (singular point) having a waveform shown in FIG. Then, while observing the output waveform of the detection coil 7, the detection coil 7 is fixed at a position where, for example, a mark M is present on the lower side similar to the waveform shown in FIG.

Next, in the B phase, as shown in FIG. 3, the small through transformer 10a is arranged on the cross bond wire 9a of the B phase insulating connection portion 8a. And the transformer 10
As in the case of the A phase, a current having a mark M shown in FIG. In this way, while watching the output waveform of the detection coil 7 ', the detection coil 7'is fixed at a position where the mark M is on the lower side and the output is at an appropriate level, as in the case of the input waveform. . The detection coil can be similarly positioned for the C phase.

In the example shown in FIG. 1, for example, a current having a waveform shown in FIG.
In other words, if it is an S twist, all the detection coils are mounted on the S twist, but in reality, if the singular points of the output waveforms of the detection coil are in the same direction, the fault section can be located, so the detection coil output If the orientation of the wiring to the end is also taken into consideration, it is possible to mount and position on the Z twist. In this way, by positioning the detection coils by catching the points where the currents injected from the feed-through transformer attached to the cross bond wires are in the same direction, all the detection coils of each phase are wired in the same twisting direction. Can be placed on the shield. Regarding the current waveform injected from the cross bond wire, it suffices if there is a difference in the detected waveform between when the detection coil is on the S twist wire shield and when it is on the Z twist wire shield. 180 °
Anything that does not overlap the original waveform when the phase is shifted and the polarity is inverted may be used. For example, the waveform may have a mark as shown in FIG.
A unipolar waveform as shown in FIG. 7 or a pulse waveform as shown in FIG. 7 may be used.

[0015]

As described above, according to the positioning method for the fault section locating coil in the underground power transmission line of the present invention, S- which cannot be dealt with by the prior art.
Even in an underground power transmission line having a Z-strand wire shield, it is possible to easily position the detection coil and perform reliable location of an accident section.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining a procedure used in a coil positioning method of the present invention,

FIG. 2 is a waveform diagram showing an example of a waveform of a current flowing through a wire shield,

FIG. 3 is a circuit diagram for explaining a procedure used for a coil positioning method in another phase of FIG.

FIG. 4 is a side view showing the configuration of a wire shielded transmission line in an upper half section in section;

5 (a), (b), (c), and (d) are waveform diagrams showing states of waveforms observed on S twist and Z twist,
(A) is a top view showing the twisted state of the wire shield and the positional relationship of the detection coil, (b) is the input current waveform, (c) is S
Waveform on twist, (d) Waveform on Z twist,

FIG. 6 is a waveform diagram showing an example of a waveform of a current passed through a wire shield,

FIG. 7 is a waveform diagram showing an example of a waveform of a current passed through a wire shield.

[Explanation of symbols]

 1 Cable 2 Cable Conductor 3 Cable Insulator 4 Cable Core 5 Wire Shield 6 Plastic Corrosion Protection Layer 7, 7'Detection Coil 8, 8a, 8b Insulation Connection Section 9, 9a Cross Bond Wire 10 Penetrating Transformer for Energization

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadayoshi Ikeda 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture “Inside the Electric Wire Research Laboratory, Hitachi Cable, Ltd.” (72) Inventor Yasuo Sekii Hidaka, Hitachi City, Ibaraki Prefecture 5-1-1, Machi "Inside the Electric Cable Laboratory, Hitachi Cable" (72) Inventor Hideo Sato 5-1-1, Hidakacho, Hitachi City, Ibaraki "Inside the Hitachi Cable Electric Cable Laboratory" (72) Inventor Shin Hara 5-1-1, Hidaka-cho, Hitachi, Ibaraki “Inside the Hitachi Cable Electric Wire Co., Ltd.” (72) Inventor Shiro Tanno 5-1-1, Hidaka-cho, Hitachi, Hitachi, Ibaraki (72) Inventor Keiichi Ouchi 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture "Inside the Hitachi Cable Electric Wire Research Laboratory"

Claims (1)

[Claims] 1. An axial magnetic field generated by twisting of a wire shield of a cable constituting an underground power transmission line is picked up by a detection coil wound around the circumference of the cable, and thereby the direction and magnitude of a current flowing through the wire shield are determined. In the method of detecting and locating the faulty section, if the wire shield is SZ twist, current with a singular point is applied to the wire shield, and it is obtained by the detection coil of each phase.
That in a position such that the orientation of the singular point is identical in the output waveform, a method of positioning fault section locating coil in underground transmission lines, characterized in that so as to fix the phase of the detection coil.