JPH0139296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-strength nonmagnetic sheathed cable junction box and a method for grounding a nonmagnetic sheathed cable line using the junction box.

[Conventional technology and its issues]

When transmitting three-phase power using a conventional three-line underground cable, in order to reduce or eliminate the sheath current induced in the sheath, A, B, and C are formed using ordinary metal sheathed power cables as shown in Figure 3. Normal junction box (usually grounded) 1, 2, 3, for each phase of
4, 5, 6 and insulated junction box (usually ungrounded) 7,
8, 9, 10, 11, and 12 respectively, and between the insulating junction boxes 7, 8, and 9, and also between the insulating junction boxes 7, 8, and 9.
Cross bonding is performed between 0, 11, and 12, and an earth arrester 13 is connected to the ground 14 in the insulating connection box as a corrosion protection layer protection device for protecting the corrosion protection layer from abnormal voltage generated in the sheath. . However, since the conventional insulating junction box uses the insulating insulating tube 31 between the two divided metal cases, its shape becomes large, and the hole in which it is housed also becomes large.

On the other hand, when using a cable whose cable sheath is made of a high-strength non-magnetic metal such as stainless steel, the sheath has a high impedance and almost no sheath current flows through the sheath, so a solid bond is sufficient for each junction box. A cross bond using an insulating connection box as shown in FIG. 3 is not necessary. However, if a return conductor is provided under the cable sheath to secure an abnormal current path during an abnormality, for example, a ground current path, a conventional insulated junction box must be used for cross-bonding. In this case as well, since an insulating insulating tube is used, the shape of the insulating junction box becomes large, resulting in a drawback that the volume of the hole for housing the box becomes large.

In order to solve the above-mentioned drawbacks, the present invention provides a cable connection circuit in which a plurality of power cables are laid in parallel and a return conductor is inserted under a high-strength non-magnetic cable sheath, and a junction box is cross-bonded. The present invention provides a completely novel and useful junction box configuration and a method for grounding a cable line using the same.

[Means to solve the problem]

(1) Junction box A junction box consisting of a metal case for cross-bonding power cables in which the return conductor is placed under a high-strength non-magnetic sheath, and divided into two in the length direction, each with opposite connection ends. A high-strength non-magnetic conductor, comprising: a through-hole for a lead-out conductor connected to each of the return conductors; further, an insulating pushing is provided in the through-hole; and a grounding terminal is provided at one of the opposing connection ends. The purpose is to use it as a junction box for sheathed cables.

(2) How to ground a cable line using the junction box: Lay multiple power cables in parallel with a return conductor under a high-strength non-magnetic cable sheath.
In addition, in a cable line having a cross-bonded junction box, the opposing return conductors in the junction box are individually electrically pulled out of the junction box, and the pulled-out conductors or wires are used to connect the cross of each junction box. This is a method of grounding a high-strength non-magnetic sheathed cable line, which is characterized by bonding and grounding the junction box.

〔Example〕

This will be explained in detail with reference to the drawings. Figure 1 is for cross-bonding of high-strength non-magnetic sheathed cables, and is a cross-sectional view of a part of a junction box divided into two parts, in which 15 is a junction box for connecting opposing high-strength non-magnetic sheathed cables, and 16 is a connection box. The box container includes a cable insulating core 17, an insulating reinforcing layer 18, and a sheath 19 made of a high-strength nonmagnetic material such as plastic or stainless steel, and the pleated stainless steel sheath is shown in the drawing. 20 is a return conductor provided under the sheath, and 21 is wired so that it is insulated by a take-out conductor or lead wire that is in contact or connected to the bottom of the return conductor 20, or that it does not come into contact with other objects. Reference numeral 22 represents a wire outlet insulating bushing attached to the upper part of the junction box container 16, and represents a wire outlet, and a similar conductor outlet 23 (not shown) is provided on the opposite side of the lower part of the same junction box. 2
4 is a ground terminal provided in a part of the connection box, 25 is the ground, 26 is a lead connecting part between the connection box container 16 and the high-strength non-magnetic sheath, and 27 is a corrosion-resistant layer.

Therefore, in the above junction box, the opposing return conductor ends of the connecting cables are insulated from each other and pulled out separately to form the junction box and grounded.

Figure 2 is a circuit diagram in which the junction box equipped with the above grounding terminal is inserted into a three-phase high-strength non-magnetic sheathed cable circuit and cross-bonded. Each phase is A, B, C with power supply.
shall be. 29 is a high-strength non-magnetic sheathed cable, 1
5 _A , 15 _B , 15 _C , 15' _A , 15' _B , and 15' _C are connection boxes according to the present invention, respectively, and have conductor wires 30 connected to two mutually insulated return conductor outlets 22 and 23. Cross bonding is performed by

Therefore, at all times, most of the current induced in the sheath 19 and the return conductor 20 flows through the return conductor 20,
(This is because when comparing the impedance of the sheath 19 and that of the return conductor 20, the impedance of the sheath 19 is about 20 to 30 times higher.) The flow then sequentially flows through the take-out conductor 21 and the conducting wire 30, forming a cross bond. Form.

Next, abnormal surge voltage generated in the sheath 19 and return conductor 20 during a track accident, lightning strike on the track, opening/closing of the track, etc. flows to the ground 25 via the sheath 19, connection container 16, and grounding terminal 24. becomes.

〔Effect of the invention〕

The junction box for high-speed non-magnetic sheathed cables and the method of grounding the cable line using the same according to the present invention are such that a plurality of power cables each having a return conductor inserted under a high-strength non-magnetic sheath are laid in parallel. The opposite end of the return conductor in each junction box is electrically taken out to the outside of each junction box to perform cross bonding of each junction box, and the junction box is grounded. No earth arrester is required, and no sheath current is induced in the sheath.
Furthermore, since the junction box is compact, the hole for housing the junction box can be made smaller.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a portion of a junction box used in the high-strength non-magnetic sheath cable grounding method of the present invention, and Fig. 2 is a three-phase diagram showing an embodiment of the high-strength non-magnetic sheath cable grounding method of the present invention. Circuit Diagram of Underground Power Transmission Line FIG. 3 is a circuit diagram showing a conventional method of grounding a three-phase underground power transmission line. 1, 2, 3, 4, 5, 6 are ordinary junction boxes for ordinary metal sheathed power cables, 7, 8, 9, 10, 1
1 and 12 are insulated junction boxes, 13 and 14 are lightning arresters, 15 and 15' are junction boxes of the present invention for high-strength non-magnetic sheathed cables, and 16 are junction box containers;
7 is a cable insulated core, 19 is a high-strength non-magnetic sheath, 20 is a return conductor under the sheath, 21 is a take-out conductor or conducting wire connected to the return conductor, 22, 23
is the outlet insulating bushing.

Claims (1)

[Claims] 1. A junction box consisting of a metal case for cross-bonding a power cable in which a return conductor is inserted under a high-strength non-magnetic sheath, and divided into two in the length direction,
A through hole is provided at both ends of each opposing connection end for a lead-out conductor to be connected to each of the return conductors, an insulating bushing is provided in the through hole, and a grounding terminal is provided at one of the opposing connection ends. Connection box for high-strength non-magnetic sheathed cable. 2. Laying multiple power cables in parallel with a return conductor inserted under a high-strength non-magnetic cable sheath,
In a cable line having a cross-bonded junction box, each of the return conductors facing inside the junction box is electrically routed outside the junction box,
A method of grounding a high-strength non-magnetic sheathed cable line, comprising cross-bonding each junction box with the drawn-out conductor or conducting wire and grounding the junction box.