JPH02133024A - Connecting part of power cable - Google Patents

Abstract

PURPOSE:To prevent the affection of external noise and the like and facilitate the detection of abnormal current by a method wherein an outer conductor is provided on the shielding layer of a cable and the outer conductor is insulated from the left side and the right side in the lengthwise direction of the cable in a conjunction box while the shielding layer is cut off in the lengthwise direction of the same. CONSTITUTION:A connecting part shielding layer 11 is conducted to the shielding layer 3 of a power cable C and is cut off lengthwise in the metal case 13 of a connecting part at a position 11a. The outer conductor 12 of the connecting part is conducted to an outer conductor 4 and is insulated lengthwise at a position 12a. The metal case 13, conducted to a metallic sheath 6, is provided at the outside of the outer conductor 12 of the connecting part through an insulating layer. Charging current and noise current from the conductor are conducted through the outer conductor 12. The currents are cancelled by penetrating the lead wires 15 of the outer conductor through an optical CT 16 from reverse direction. When corona discharge is generated in either side of a conjunction box A, the optical CT 16 detects a pulse current accompanied by the corona discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a connection part of a power cable that makes it possible to detect abnormal current in a power cable for underground power transmission.

(Prior Art and Problems to be Solved) Generally, a power cable has a shielding layer grown outside the insulation layer, and a metal sheath is provided on the shielding layer, and the shielding layer and the metal sheath are electrically the same. It has a structure that creates a potential.

Power cables in which an outer conductor is provided on the shielding layer have also been put into practical use, but in this case as well, the outer conductor and the metal sheath are designed to have the same potential.

In conventional power cables in which the shielding layer or outer conductor as described above is constructed to have the same potential as the metal sheath,
Abnormal current caused by an abnormal phenomenon at the cable section or cable connection section flows into the metal sheath of the cable and the external metal case of the junction box. However, since the metal sheath and external metal case are easily affected by external noise, it is difficult to detect abnormal current, and this has not been implemented to date.

The inventor of the present invention has newly proposed a power cable that solves these problems and facilitates the detection of abnormal currents associated with abnormal phenomena.

FIG. 1 is a cross-sectional view of a concrete example of the newly proposed power cable.

In the drawings, (l) is a conductor, (2) is an insulating layer, and (3)
is a shielding layer, and (4) is an external conductor provided on the shielding layer (3), which has sufficient capacity to flow the charging current of the cable. A metal sheath (6) is provided on the outside of the external conductor (4) with an insulating layer (5) interposed therebetween.

In such a power cable (C), the metal sheath (6) and the outer conductor (4) are completely insulated, so that abnormal current flows through the outer conductor (4). At this time, the outer conductor (4)
Since it is shielded by the metal sheath (6), it is not affected by external noise and the like, making it easy to detect abnormal current.

(Means for Solving the Problems) The present invention provides a power cable connection section that realizes abnormal current detection in a line using the power cables as described above, and its first feature is as follows: An external conductor is provided on the cable shielding layer, and a metal sheath is provided on the outside through an insulating layer.The external conductor is insulated from left to right in the length direction within the connection box. The shielding layer is also cut in the length direction within the connection box, lead wires are connected to each of the left and right external conductors, and an optical CT is provided to pass through these lead wires.

A second feature of the present invention is that the above-mentioned connection portion A and the outer conductor are completely integrated in the length direction within the connection box, and
The shielding box is also cut in the length direction within the junction box, and the power cable connection parts B with arresters installed between the metal cases of the junction boxes of the outer conductors are installed alternately in the length direction of the cables. be.

FIG. 2 is a diagrammatic longitudinal sectional view of a specific example of the connecting portion A according to claim (1) of the present invention.

In the drawing, (I1) is a connecting part shielding box provided in communication with the shielding layer (3) of the power cable (C). Edge cutting (Ila) in the length direction regardless of the part (IJ)
) has been done. (12) is a connection external conductor provided in communication with the external conductor (4) of the power cable (C), and is insulated in the length direction (12
a) It has been done. The metal sheath (6
) is provided with a metal case (I3) communicating with it.

The left and right connecting portion outer conductors (l2
) to each of the lead wires (l5), and then attach the metal case (
I3) through the bushing (l4), and pull it out from the opposite direction as shown in the figure.
It is penetrated by an optical CT (16) provided outside. CT ahead (
18) is connected to an electrical/optical converter (17) with a built-in pulsed current detector and a transmission terminal (18), and the optical signal is transmitted to the central monitoring station via an optical fiber (19). .

FIG. 3 is a diagrammatic longitudinal cross-sectional view of another specific example of the connecting portion A similar to FIG. 2. This specific example differs from FIG. 2 in that the optical CT (+6) that passes through the leader line (l5) is provided in the metal case (13) of the connection part.

(Function) In the connection part of the power cable of the present invention having the above-described structure, the connection part external conductor (I2) is connected to the outer metal case (
13), only the charging current and abnormal current will flow without being affected by external noise. In this case, charging can be carried out by passing the leader wires (15) of the left and right outer conductors (12), which are insulated (12a) in the length direction, into an optical CT (ordinary CT may be used) from the opposite direction as shown in the figure. Currents and noise currents from conductors are also canceled, corona 7I due to abnormal phenomena in cables and connections! Only current can be detected.

(Example) FIG. 5 shows a specific example of a power cable line stability detection system using the connection part A of the present invention.

As shown in the drawing, in the length direction of the power cable (C),
The connections A shown in FIGS. 2 and 3 and the connections B shown in FIG. 4 are installed alternately.

As shown in Fig. 4, the connection part B is connected to the shielding layer (3) of the cable in a metal case (l3) that communicates with the metal sheath (8) of the cable, and has an edge cut (Ila) L in the length direction.
The connecting part shielding ffl (11) and the connecting part outer conductor (I2) communicating with the outer conductor (4) of the cable and insulated in the length direction (12a),
) and the outer metal case (13) are insulated. An arrester (2) is provided between each of the left and right external conductors (I2) insulated in the length direction and the outer metal case (13).
0).

As mentioned above, a charging current and a noise current from the conductor flow through the external conductor (l2) of the connection part, but these currents are passed through the optical CT (If
t) is canceled by penetrating it. Therefore, if corona discharge occurs on either side of connection A,
The optical CT (lft) detects the pulse current accompanying this.

When the pulsed current detector connected to connection part A detects the pulsed current accompanying the corona discharge, an electrical/optical converter (
It is converted into an optical signal at the transmission terminal (I8) and transmitted to the central monitoring station (21) via the optical fiber cable (I8), where it is compared with the detection data of the adjacent connection point A at the central monitoring station (2l). to determine the corona discharge occurrence section.

(Effects of the Invention) As explained above, by providing the power cable connection part of the present invention, abnormal phenomena in power cables such as OF cables and Cv cables and their connection parts can be prevented in advance before electrical breakdown occurs. It is extremely effective in terms of maintenance of power cable lines.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a power cable according to the present invention. 2 and 3 are both diagrammatic longitudinal cross-sectional views of specific examples of the connection portion of the power cable of the present invention. FIG. 4 is a diagrammatic longitudinal cross-sectional view of another specific example of the connecting portion according to the present invention. FIG. 5 is a diagrammatic explanatory diagram of an abnormality detection system for power cable lines using the connection section of the present invention. l1... connection part shielding layer, l2... connection part outer conductor,
+3...Metal case, 14...Bushing,! 5.
...Leader line, 1B...Optical CT117...Converter, l
8...Transmission end, +9...Optical fiber cable, 2
0...Arrester, 21...Central observation post. Toru 1 Bungan 2 Zuhakuzu

Claims (2)

[Claims] (1) An external conductor is provided on the cable shielding layer, and a metal sheath is provided on the outside through an insulating layer.The external conductor is insulated from side to side in the length direction within the connection box. At the same time, the shielding layer is also edged in the length direction within the connection box, leader wires are connected to each of the left and right external conductors, and an optical CT is provided that penetrates these leader wires. Power cable connection. (2) The connecting portion A according to claim (1) and the outer conductor are insulated in the length direction in the connection box, and the shielding layer is also cut in the length direction in the connection box, and the outer conductor is insulated in the length direction in the connection box. 1. A power cable connection portion B, which is provided with an arrester between each of the power cable connection portions B and a metal case of a connection box, and is alternately installed in the length direction of the cable.