JPH0778515B2 - Accident location method of underground railway - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for locating an accident on an underground track,
More specifically, it relates to the provision of such a method that is useful for locating the ground fault point of a cable that constitutes an underground line.

[Conventional technology]

A cable that constitutes an underground line has a metal sheath such as an aluminum sheath on the cable core, and measures the current flowing in the conductor of the cable core, that is, the conductor current, and the current flowing in the metal sheath, that is, the sheath current, separately Is particularly important in the method of locating the ground fault section from the ground fault current distribution at the time of the ground fault.

That is, the ground fault accident point can be estimated from the distribution of the zero-phase current flowing through the conductor of the cable core or the metal sheath,
In reality, most of the ground fault current flowing in the conductor flows through the metal sheath as a return path, so the conductor current and sheath current are combined even when measured from the outer circumference of the cable with a current transformer (CT) or magnetic field sensor. It has been considered that effective measurement is impossible because the detected and canceled current components are detected.

Therefore, in general, at the insulation connection (IJ) where the metal sheath is cut off in the length direction of the cable, the current flowing through the cross-bond wire connected for the twisting of the sheath circuit is changed by a current transformer (CT), etc. The method of obtaining the zero-phase current of the sheath circuit and determining the fault zone was adopted by measuring with.

[Problems to be Solved by the Invention]

However, in such a method, the measurement point is limited to the insulation connection portion, and the location of the accident point is limited to the section of insulation connection portion-insulation connection portion.

In other words, since the conductor current and the sheath current can be separated only at the insulated connection, the ground fault fault location is limited to the insulated connection and the span of the insulated connection, and the normal connection (NJ) In the section including, it was difficult to determine which side of the span the accident was occurring with the grounded ordinary connection as the boundary.

Therefore, in the above method, when it is desired to locate the faulty section in the line including the ordinary connecting portion, it is necessary to replace the ordinary connecting portion with the insulating connecting portion, and it cannot be said to be widely applicable.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a completely new method that enables to locate posterior points before and after a normal connecting portion in a line including the normal connecting portion.

[Means and actions for solving the problem]

According to the present invention, the magnetic field in the conductor axial direction generated by the segment twist of the segment conductor of the cable forming the underground line is picked up by the sensor coil wound on the cable, and the fault current flowing in the conductor is thereby caused. The orientation and size of the cable are detected and the fault point of the cable is located.

The above means in the present invention is based on the following findings.

That is, since the segments are twisted as conductors in the ultra high voltage cable constituting the underground line, a magnetic field is generated in the conductor axial direction due to the twisting of the segments. On the other hand, in a metal sheath such as an aluminum sheath provided on the cable core, an electric current that cancels the magnetic field created by the conductor flows.

However, in reality, since the metal sheath, such as an aluminum sheath, has a resistance, the magnetic field is not completely canceled by the sheath. It has been found that the magnetic field of a weak conductor can be detected.

The present invention enables the location of the fault point by knowing the distribution of the conductor current at the time of the fault by thus detecting the weak magnetic field in the axial direction of the conductor appearing on the cable surface. Furthermore, the fault currents can be located more easily by combining the conductor currents for each line and creating a zero-phase current distribution.

〔Example〕

The attached drawings show an embodiment of a method for locating an accident on an underground track according to the present invention at a sensor coil mounting portion.

The cable 1 is configured by forming a metal sheath 5 such as an aluminum sheath on a cable core 4 mainly composed of a conductor 2 and an insulator 3, and forming a plastic anticorrosion layer 6 on the metal sheath 5. The sensor coil 7 is directly wound around the surface of the anticorrosion layer 6.

The conductor 2 of the cable core 1 is usually formed by twisting a plurality of segments 2a. Based on the current flowing in the conductor due to the segment twist, not only the magnetic field in the plane orthogonal to the base but also the conductor An axial magnetic field is generated. The magnetic field of the axial component is linked with the sensor coil 7 wound around the surface of the anticorrosion layer 6.

The sensor coil 7 is wound on the anticorrosion layer 6 in a state of intersecting at right angles with the conductor axial direction in order to interlink with the magnetic field of the conductor axial direction component, and the magnetic field of the conductor axial direction component is metallic. Since the sheath 5 is canceled by a considerable amount and becomes weak on the surface of the anticorrosion layer 6, many turns are arranged by the number of turns sufficient to pick up the weak magnetic field.

Here, when the magnetic flux interlinking with the sensor coil 7 is φ, a voltage of n × δφ / δt is induced in the coil. Note that n is the number of turns of the coil.

Therefore, information on the magnitude and phase of the current in the conductor can be known based on the current due to the voltage induced in the sensor coil 7.

〔The invention's effect〕

According to the underground line locating method of the present invention described above, since the sensor coil for picking up the magnetic field in the conductor axial direction is provided on the surface of the cable, the conductor current can be detected at any position of the cable, Therefore, there is an effect that an arbitrary section can be located even if it is a normal connection part.

[Brief description of drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are partially cutaway front elevational views showing an embodiment of a method of locating an accident on an underground track according to the present invention. In the figure, 1 is a cable, 2 is a conductor, 2a is a segment, 3 is an insulator, 4 is a cable core, 5 is a metal sheath, 6 is a plastic anticorrosion layer, and 7 is a sensor coil.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirosuke Saito 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Tadashi Ikeda Hitachi City, Hidaka, Ibaraki Prefecture 5-1-1, Machi, Hitachi Cable Co., Ltd. Hidaka Factory

Claims (1)

[Claims] Claim: What is claimed is: 1. A sensor coil wound around a cable picks up a magnetic field in the conductor axial direction generated by segment twisting of a segment conductor of a cable that constitutes an underground line, whereby the direction and magnitude of a fault current flowing through the conductor. Method for locating the fault point of the cable by detecting the height of the fault and locating the fault point of the cable.