JPH03170881A - Locating method for accident point of underground line - Google Patents

Abstract

PURPOSE:To locate the accident point of a cable by detecting the direction and magnitude of a fault current on the basis of the zero phase current picked up by the sensor coil wound around the iron core arranged to the center of cables assembled in the shape of a pyramid-like stack of three cores in cross section. CONSTITUTION:Cables 10a - 10c having cable conductors are stacked and a sensor wherein a coil 7a is wound around an iron core 8 is arranged to the center of the cables assembled in the shape of pyramid-like stack of three cores in cross section. Since the coil 7a is positioned at an equal distance from the respective cable conductors, the components in the axis direction of the magnetic fields generated by the cables 10a - 10c interlinks the coil 7a in the same ratio as the coil 7a and, therefore, the output proportional to a zero phase component is obtained in the coil 7a. The density of magnetic flux interlinking the coil 7a becomes high by providing the iron core 8a and the sensitivity of the coil 7a is enhanced. By this method, since a current can be directly detected by a pickup coil, this method is extremely effective in the detection of an accident point.

Description

[Detailed description of the invention] The present invention relates to a fault point locating method for underground power transmission lines.

[Prior art] Cables that make up underground lines have a metal sheath such as an aluminum sheath or a wire shield over the cable core, and this technology separates and measures the current flowing through the conductor of the cable core, that is, the sheath current. This is especially important in the method of locating the ground fault section from the ground fault current distribution during a ground fault fault.

In other words, ground faults can be estimated from the distribution of zero-sequence current flowing through the cable core conductor or metal sheath, but in reality, most of the ground fault current flowing through the conductor is attributed to the metal sheath. current transformer (C) from the outer circumference of the cable.
It was thought that effective measurement was impossible because the conductor current and sheath current were combined and the canceled current components were detected after measurements were taken using T) or magnetic field sensors. Therefore, in general, at the insulated joint (IJ) where the metal sheath is interrupted in the length direction of the cable, the current flowing through the cross bond wires connected for twisting the sheath circuit is transferred to a current transformer (CT). A method was adopted in which the zero-sequence current of the sheath circuit was determined by measuring the zero-sequence current of the sheath circuit, and the fault section was determined.

However, in this method, the measurement points are limited to the insulated connections, and the location of the fault point is limited to the area between the insulated connections. In other words, since the conductor current and sheath current can be separated only at the insulated connection, the location of the ground fault area is limited to the insulated connection and the span of the insulated connection, and the normal connection (NJ) It was difficult to determine whether the accident occurred on either side of the span, with the grounded normal connection as the boundary. Therefore, with the above method, if you want to locate a fault section on a track that includes normal connections, it is necessary to replace the normal connection with an insulated connection, and it is difficult to say that it can be used widely. Recently, as an alternative to this method, a new method has been proposed that makes it possible to locate fault points before and after a normal connection on a track that includes a normal connection. That is,
The magnetic field in the direction of the conductor axis generated by the segment twisting of the segment conductors or the twisting of the wire shield of the cable that makes up the underground line is caused to surprise the sensor coil wound on the cable, thereby controlling the direction of the fault current flowing in the conductor. This is a method of locating the point of cable failure by detecting the size of the cable.

This method will be explained below with reference to the drawings.

FIG. 2 is a cross-sectional side view of the upper half showing only the sensor coil mounting portion, in order to explain the fault point locating method for this underground railway. That is, the cable l is placed on a cable core 4 whose main elements are a conductor 2 and an insulator 3.
A metal sheath 5 such as an aluminum sheath is provided, and a plastic anti-corrosion layer 6 is formed on the metal sheath 5, and a sensor coil 7 is directly wound and disposed on the surface of the plastic anti-corrosion layer 6.

The conductor 2 of the cable core 1 is usually constructed by twisting a plurality of segments 2a, 2a, and based on the current flowing through the conductor 2 due to the segment twisting,
Not only a magnetic field in the plane perpendicular to the conductor, but also a magnetic field in the axial direction of the conductor 2 is generated. This axial component magnetic field is interlinked with the sensor coil 7 wound around the surface of the anti-corrosion layer 6. In order to interlink with the magnetic field of the axial component of the conductor, the sensor coil 7 is wound on the brassic anti-corrosion layer 6 so as to cross the conductor axial direction at right angles, and the magnetic field of the axial component of the conductor is Since a considerable amount of the magnetic field is canceled out by the metal sheath 5 and becomes weak on the surface of the plastic anticorrosion layer 6, it is necessary to arrange a large number of turns with a number of turns sufficient to boost this weak magnetic field.

[Problem to be solved by the invention] By the way, the above method is an excellent method, but when the other phases are close to each other, such as in a stacked cable or a Triplex cable, the magnetic flux of the other phases increases. There is a problem that the error becomes large because it is linked to the coil. The present invention has been made in view of the above points, and an object of the present invention is to provide a fault point locating method for underground railway lines that facilitates locating fault points before and after the normal connection in a line including the normal connection. Purpose. [Means for Solving the Problem] In the present invention, the magnetic field in the axial direction of the conductor generated by the segment twisting of the segment conductors of the cable constituting the underground line or the wire twisting of the wire shield is applied to a three-core cable stacked in bales or The direction and magnitude of the fault current can be detected by the zero-sequence current that is surprised by the sensor coil wound around the iron core located at the center of the triplex cable, and the fault point on the cable can be located. This is a method for locating accident points on underground railway lines.

[Embodiments] Hereinafter, embodiments of this invention will be explained based on the drawings. FIG. 1 shows cables 10a, 10b, and 10c having cable conductors 11a, llb, and 11c stacked in a stack, and a coil 7a wound around an iron core 8 on the center plane of the three-core stacked cable as shown in FIG. Place the rotated sensor. therefore,
Since the coil 7a is located equidistant from each cable conductor 11a, llb, llc, each cable 10a, 10b, 1
Since the axial component of the magnetic field generated by 0c will interlink with the coil 7 at the same ratio, the coil 7 will have an output proportional to the zero-phase component. By providing the iron core 8, the density of magnetic flux interlinking with the coil 7a is increased, and the sensitivity of the coil 7 is improved. [Effects of the invention] Normally, ground faults are detected from the distribution of the conductor current or sheath current of the cable, but with this invention, the current can be directly detected using the big-up coil.
This is an extremely effective means of detecting accident points.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining the accident point marking method for underground railway lines of the present invention, FIG. 2 is a perspective view of a big-up coil, and FIG. 3 is a cross-sectional view for explaining the prior art. FIG. 2 is a partially cutaway side view. 1, 10a, 10b, 10c-cable 2, 1 1a,
1 lb, 1 1c = Cable conductor 3...Insulator 4...Cable core 5...Metal sheath 6...Plastic anti-corrosion layer 7.12...Sensor coil

Claims (1)

[Claims] The magnetic field in the conductor axis direction, generated by the segment twisting of the segment conductors of the cables that make up the underground line or the wire twisting of the wire shield, is wound around the iron core placed at the center of the three-core cable stacked in bales or the triplex cable. A method for locating a fault point on an underground line, characterized in that the fault point on a cable is located by detecting the direction and magnitude of a fault current using a zero-sequence current that is surprised up in a sensor coil.