JPS5951208B2 - Single core power cable twisting and cross bond installation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a cable twisting and cross-bond connection method in a single-core cable cable three-phase power transmission line installed in a non-equilateral triangular arrangement when cable twisting and metal sheath cross-bonding are used together. Regarding improvements.

In a conventional power transmission line like this, one section has three cable spans, and there are ordinary junction boxes (hereinafter abbreviated as NJ) that are grounded at the connection points at both ends of the section, and two connection points within the section. An insulated junction box (hereinafter abbreviated as IJ) was placed in the

Therefore, two IJs were used for each three spans of one phase of cable.

Compared to NJ, IJ (a) has a complicated structure and is therefore more expensive; (b) connection work is more complicated; and (c) in addition to cable connection work, cross-bond connections and cable anti-corrosion layer protection equipment are required. Therefore, there are disadvantages such as high construction costs.

The present invention assumes that 6 cable spans are one section, and connects NJ to ground at the connection points at both ends of the section, and IJ at the connection points every 2 cable spans from the end of the section.
At the other three connection points, non-grounded NJs are placed.

In this method, 2 IJs are installed per 6 spans of 1 phase of cable.
Since this method uses half of the number of IJs used in the past, it is possible to provide an inexpensive power transmission line.

Note that, as an additional effect of the present invention, the induced voltage of the metal sheath is reduced, but the amount of reduction is not a significant enough feature to be listed as an effect of the present invention.

Figure 1 is a twisted and cross-bond connection diagram of a single-core cable cable three-phase power transmission line installed in a non-equilateral triangular arrangement when conventional cable conductor twisted and metal sheath cross-bonded connections are used together. 1 is a single-core cable, 2 is a cable conductor, 3 is a metal sheathed cross bond wire, 4 is a grounding wire for the NJ to be grounded, E is a connection point where the NJ is grounded by the grounding point 4, ■ is the IJ is placed connection point, A,
B and C indicate the installation positions of single-core cables.

Note that in the drawing, illustrations of NJ and IJ are omitted.

The section sandwiched by grounding NJ, that is, connection points E-1 and E
-2 consists of three spans of cable (1), and at connection points I-1 and I-2 within the section, cable conductor 2
are twisted together, and the metal sheaths are also connected by cross bond wires 3.

To explain the direction of the twisted frame, connection points E-1 and I
The conductor that was at position A during -1 is placed at position B in the next subsection, that is, between -1 and I-2, and similarly the conductor that was at position B is placed at position C. , and the conductor that was at position C is now placed at position A.

Further, the metal sheath is cross-bonded in a direction that reverses the twisting of the cable conductor.

That is, the cable sheath at position A is connected to the cable sheath at position C, the sheath at position B is connected to the sheath at position A, and the sheath at position C is connected to the sheath at position B.

The direction of rotation of the cable conductor twisting and the cross-bonding of the metal sheath at the next connection point I-2 is the same as that at point I-1.

As a power transmission line, this is repeated with three spans of cable consisting of connection points E-1 and E-2 as one section, and two IJs are used for each three spans of cable.

FIG. 2 is a twisted frame and cross-bond connection diagram of a three-phase power transmission line of a single-ventricular capeple according to the present invention, and the same numbers and symbols as in FIG. 1 represent the same parts as in FIG. 1, N
indicates the connection point where an ungrounded NJ is placed.

Note that in FIG. 2, as in FIG. 1, the illustrations of NJ and IJ are omitted.

The section sandwiched by grounding NJ.

That is, between connection points E-1 and E-2, there are 6 spans of cable, and at connection points I-1 and I-2 every 2 cable spans from connection point E-1, IJ is connected, and at other connection points N-1. , N-2 and N-3, non-grounded NJs are arranged.

At connection points I-1 and I-2, twisting and cross-bond connections are made in the same manner as in the conventional system shown in FIG.

At the connection points N-1, N-2 and N-3, the cable conductor and the metal sheath are both twisted in the same direction as the cable conductor at the connection point I.

As a power transmission line, one section consists of six cable spans consisting of connection points E-1 and E-2, and this is repeated, and two IJs are used per six cable spans.

Next, we will compare the voltage induced in the metal sheath with the conventional method.

The induced voltage e1 generated in the metal sheath in the conventional method is (
In the formula 11), the induced voltage e in the case of the method according to the present invention is
2 is shown by equation (12).

In this 1, ゛Xm=2W (loge-)xlO' (Ω/k
m) a = 2W (1 oge2) XIF4 (Ω/km
) W = 2πf S: Cable center spacing rm: Average radius of metal sheath f: Transmission system frequency i: Conductor current In general, induced voltage becomes a problem when the cable center spacing is large, and Xm > a If the amount of reduction Δe of the induced voltage is calculated under the following conditions, the equation (13) is obtained. From the equation (13), it can be seen that the induced voltage is always reduced, but the amount of reduction is small.

As an example, when a single-core cable with a metal sheath average radius of 48 mm is laid horizontally in parallel with a center spacing of 340 mm, and a current of 105 OA flows through this conductor, the sheath induced voltage is estimated to be 125 V/km with the conventional method. On the other hand, the method according to the present invention generates 122V/km.

That is, although it is reduced, it is not a significant feature to be listed as an effect of the present invention.

The stranded and cross-bonded installation method according to the present invention as described above can reduce the number of IJs, which are complicated in structure, expensive, and time-consuming to construct, by half compared to the conventional method, making it easier and cheaper to construct power transmission lines. It has the effect of

[Brief explanation of drawings]

Figure 1 is a wiring diagram of cable conductor twisting and metal sheath cross bonding in a conventional non-equilateral triangular array single-ventricular capacitor three-phase power transmission line, where 1 is a single-ventricular capacitor, 2 is
is a cable conductor, 3 is a metal sheathed cross bond wire, 4 is a
is the grounding wire of the ordinary junction box, E is the connection point where the ordinary junction box to be grounded is placed, ■ is the connection point where the insulated junction box is placed, A
, B and C indicate the installation positions of single-core cables. FIG. 2 is a wiring diagram of cable conductor twisting and metal sheath cross bonding in a non-equilateral triangular array single-cardiac cable cable three-phase power transmission line according to the present invention, and the same numbers and symbols as in FIG. The same parts as those in FIG. 1 are shown, and N indicates a connection point where an ungrounded normal connection box is placed.

Claims (1)

[Claims] 1. In a three-phase power transmission line installed in a non-equilateral triangular arrangement that uses twisted single-core cable cables and cross-bond connections of their metal sheaths, two insulated junction boxes are installed in one section sandwiched by a grounded ordinary junction box. 3. Divide into 3 small sections, place one non-grounded normal junction box in each small section, and connect the same cable for each phase at the point of each insulated junction box and the ungrounded normal junction box. A single-core cable cable twisting and cross-bonding installation method in which the cables are twisted in the direction of rotation, and the cross-bond connections of the metal sheaths are made in the opposite direction of the cable twisting at these insulating junction box points.