JPS60233574A - Accident point detecting device of single core metallic sheath cable - Google Patents

Abstract

PURPOSE:To decrease the time and expense required for searching an accident by installing a current transformer to each link plate, and detecting with the current transformer a current flowing in the direction opposite to the steady state in direction to a metallic sheath of each section when a ground-fault accident is generated. CONSTITUTION:An electric conductor 12a of a single core cable 12 is divided into prescribed intervals in intermediate connecting parts 15a, 15b, also as for a metallic sheath 12b of the cable 12, the part of the connecting parts 15a, 15b is insulated electrically and a link box 13 is connected, and the connection of a cross-bond system is executed. That is to say, the other end of a link plate 13a whose one end is connected to a C phase is connected to one end of the sheath 12b, and the other end of the plate 13a whose one end is connected to a B phase is connected to the other end of the sheath 12b. When a ground-fault accident is generated between the connecting parts 15a, 15b, a current flowing through the electric conductor 12a flows toward the accident point by the arrow of a full line, and a current flowing in the direction opposite to the direction before the the accident is generated is detected by a current transformer 13d of an A phase being in the connecting part 15b. In such a way, the time and expense required for searching an accident can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Application of the Invention The present invention relates to a fault point detection device for a single-core metal gieskegel for detecting a fault point in a single-core metal sheathed cable.

(b) Prior Art Conventionally, ground faults occurring in single-core cables have been detected as follows. In FIG. 1, a current transformer 3 is installed near a terminal connection 2 of a single-core cable 1 sheathed with metal, and an intermediate connection 4 is attached to the cable 1 at a predetermined interval. It is provided. When a ground fault occurs in the cable 1, the current transformer 3 detects the fault current and sends it to a control panel (not shown) to indicate the occurrence of a cable fault. At the same time, a circuit breaker (not shown) operates to electrically interrupt the cable 1. Next, the fault point of the interrupted cable is detected using a known device such as the Murray loop method.

(C) Problem Since the current transformer 3 is provided only at the terminal connection 2 of the cable 1, a ground fault may occur in the cable 1 between the terminal connection 2 and 2 depending on the current transformer 3. It is only possible to judge whether or not the accident occurred, and the search for the accident point will be the future of Malaysia.
It relied on tests such as the loop method. This had the disadvantage that it took time to prepare equipment, investigate the location of ground faults, and search for cable faults.

Furthermore, the ground insulation resistance of the fault point of the cable 1 may be high, and in this case, it is difficult to search for the fault point.

(2) Purpose This invention was made based on the above-mentioned circumstances, and its purpose is to provide a single-core metal cable that makes it easy to search for fault points in cables and that requires less time to search for fault points. - To provide an accident point detection device for a scale gel.

(E) Embodiment Hereinafter, an embodiment of the present invention will be explained based on FIGS. 2 to 5. FIG. 2 shows the terminal connection part 11, i1
A single-core metal sheathed power cable (hereinafter referred to as cable) 12 for each phase of A phase, B phase, and C phase is shown, and the metal sheath at each intermediate connection part eliminates sheath loss due to sheath current. Therefore, they are usually connected using a cross-bond method.

Cross bond method is link box 1 for cross pond
3 and a link box 14 for grounding.

As shown in FIG. 3, the link box 13 is
, C are attached, and a pound wire 13C is connected to each terminal 13h provided at both ends of each link plate 13α. A current transformer 13cL is attached to detect the direction of the current flowing through the link plate 13α.

Each bond wire 13c of this link plate 13 is cross-bonded to the metal sheath of each three-phase cable 12, as shown in FIG.

Further, as shown in Fig. W and 4, the link box 14 is equipped with three link plates 14α corresponding to each phase of A, B, and C, and terminals 14h are attached to both ends of each link plate 14α. installed. and,
One terminal 14h of each link plate 14α is connected to each other and grounded, and each link plate 1
A ground wire 14C is connected to the other terminal 14h of the terminal 4α. Further, a current transformer 14d is attached to each link plate 14α to detect the direction of current flowing therein. Each of the ground wires 14C is connected to the metal sheath of the cable 12 of each phase of A, B, and C.

FIG. 5 shows a partial schematic enlarged view of the configuration of the A-phase cable 12 shown in FIG. In FIG. 5, the conductors 12α of the cable 12 are divided at predetermined intervals at intermediate connecting portions 15α and 15h. Further, the metal sheath 12h of the cable 12 is electrically insulated at the intermediate connecting portions 15α and 15h, and the link box 13 is connected thereto. That is, one end of the link plate 13α connected to the C phase and the other end of the link plate 13α connected to the B phase are connected to one side of the insulated metal sheath 126, and the other end of the link plate 13α connected to the B phase is connected to the insulated metal sheath 12h. are respectively connected to the other side of the .

If there is no fault in the cable 12, the current will flow through the conductor 1.
2α from the left to the right in FIG. 5. As a result, a voltage is induced in the metal sheath 12b, and a sheath current flows through the metal sheath 12b from the cloth to the left in FIG.

At this time, the intermediate connection portion 15α.

Each current transformer 13Li in each link box 13 provided in the section 15h detects current in the same direction.

If a ground fault occurs between the intermediate connections 15α and 15b of the cable 12, the current flowing through the conductor 12α flows toward the fault point as indicated by the solid line arrow in FIG. Therefore, a sheath current shown by a broken line in FIG. 5 in the opposite direction to the arrow flows through the metal sheath 12h. As a result, each current transformer (hereinafter referred to as A
A current in the same direction as before the ground fault occurred is detected in the phase current transformer (hereinafter referred to as phase current transformer) 13d. On the other hand, current in the direction opposite to that before the occurrence of the ground fault is detected in the human-phase current transformers 13CL located at the intermediate connections 15. That is, in each section separated by the link box 13 provided on the cable 12, the direction of the current detected by the A-phase current transformer 13d is reversed from the normal direction of the current (in FIG. 5). A for (counting from left to right)
This means that a ground fault has occurred in the section immediately to the left of the phase current transformer 13d.

Similarly, ground faults in the B phase and C phase can also be detected.

(F) Effects As explained above, according to this invention, since the current transformer is attached to the link plate in the link box that performs cross-bonding to the metal sheath of the single-core cable, ground faults in the single-core cable can be avoided. Accident points can be detected in sections to which link plates are connected. Therefore, the section where the accident occurred can be easily detected without using conventional equipment such as the Murray loop method, and time and costs can be reduced. In particular, this invention is more effective as the length of the single-core cable becomes longer, since the section where the accident occurs can be limited to a shorter length than the length of the cable.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing conventional single-core cable accident detection, Figure 2 is a schematic diagram of the cross-bond method for single-core cables,
FIG. 3 is a schematic diagram of a link box for cross bonding according to the present invention, FIG. 4 is a schematic diagram of a link box for earthing, and FIG. 5 is an explanatory diagram of fault point detection according to the present invention. 12...Single core metal sheath electrical cable, 12α...
Conductor, 12b... Metal sheath, 13... Link box for cross bond, 13α... Link plate, 1
3b...terminal, 13C...bond wire, 13d
,...Current transformer, 14...Earth link box, 14α...Link plate, 14b...Terminal, 14C...Earth wire, 14d...Current transformer, 15α, 15b...・Intermediate connection part. Patent applicant: Sumitomo Electric Industries, Ltd. Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] The single-core cable is divided into multiple sections by electrically insulating the metal sheath of the single-core cable from each other at predetermined intervals, and a link plate for cross-bonding is interposed at each section position, using the cross-bonding method. In a single-core metal sheath cable connected to the metal sheath of a single-core cable of another phase, a current transformer is attached to each link plate, and when a ground fault occurs in the single-core cable, the metal sheath of each category is A failure point detection device for a single-core sheathed cable, characterized in that a section where a ground fault occurs is detected by detecting current flowing in the opposite direction to that in a normal state using each of the current transformers.