JPS6040246B2 - How to lay underground communication lines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for canceling or reducing electromagnetic induced voltage in a communication line installed alongside an underground power transmission line.

Conventionally, as a measure to reduce electromagnetic induced voltage on communication lines,
The so-called Kamishiyaheshi, which is a communication line with a copper tape or aluminum tape as a conductive layer and a soft iron tape or steel strip as a magnetic layer, a method in which both ends of the conductive layer are grounded with low resistance using a cable, and induced voltage suppression. Safety devices such as wire theory were used, but especially in the case of the former, it was necessary to reduce the resistance of the conductive layer by making the copper tape or aluminum tape thicker to improve the effectiveness. Alternatively, it is necessary to use a soft iron tape or steel strip with high magnetic permeability as the magnetic layer, which increases the cost of the cable and increases the weight as the outer diameter increases. In addition to having disadvantages such as poor flexibility, cumbersome handling, and being uneconomical, such electromagnetic shields and cables must be used with both ends grounded, and their performance is limited by grounding. Performance was not very favorable as it was greatly influenced by the magnitude of resistance.

In addition, in the latter case, the equipment cost per line increases due to the amount of induction and its insulation, which is not economical, and it is especially uneconomical for multi-pair cables. . This invention was made to eliminate these drawbacks, and provides a method for laying communication lines without applying any special electromagnetic shielding or security devices to the communication lines. The purpose of this invention is to provide a method for laying a communication line that achieves a predetermined electromagnetic shielding effect.

Next, one embodiment of this invention will be explained with reference to the drawings.
The electromagnetic induced voltage due to the three-phase underground transmission line is
B}, the magnitude and polarity of the real and imaginary parts of the induced voltage vary depending on the relative positional relationship with the R phase, S phase, and T phase of the power transmission line.
Then, focusing on the fact that the induced voltage has three phase relationships: (a + gong), (a-ib), and (1a-kong), we can communicate at fixed length intervals as shown in Figure 2. Laying the tracks by alternating their positions (hereinafter referred to as cross-laying).

) to cancel out or reduce the yield voltage for each given length within a given length. In this case, as shown in 'B}, the communication line should be symmetrical about the S phase of the power transmission line, and its position should not only be directly above the R phase or T phase, but also have enough margin to be shifted to some extent. degree. Furthermore, to explain in detail, the absolute value of the induced voltage when the S-phase is symmetrically crossed at the point of 1 with respect to the total length 1 is as shown in Small Insert Journal XI.

-4 (V) (However, 1: Angular frequency, 1: Length (object),
1: Phase current of the power transmission line (■, R・S・T: separation distance from each phase), and its distribution diagram is shown in Fig. 3.

That is, when the cables are laid at equal intervals, there is a position where the induced voltage becomes zero. If this is expressed on the coordinate axes in Figure 3, it is a point of interest.As a specific example, if the phase spacing of the underground power transmission line is 25 (ground), the position directly above the R phase and T phase, approximately 1
If the wires are crossed at the position of 7.7 (inhibition), it is possible to make the electromagnetic transfer voltage zero. Next, an experimental example will be explained. Table 1 shows the actual measured values of the electromagnetic induction voltage during non-cross laying and crossing laying in FIG.

Table 1 Furthermore, Table 2 shows the actual measured values of the electromagnetic induction voltage when the cables were laid without crossing and when they were laid with crossing in FIG.

Table 2 As described above, this invention has the following effects.

'11 Electromagnetic induced voltage can be canceled out or reduced simply by laying communication lines across power transmission lines at appropriate intervals, so it can be sufficiently avoided and effective in practice.

(2) Therefore, since there is no need to provide a special shield or layer to the communication line, it is possible to provide an economical communication line that is light in weight, has a small outer diameter of 4 mm, and has good flexibility.

[3' Also, it is extremely reliable as it is not affected by the cable structure or grounding resistance as in the past.

■ Since communication lines can be brought closer to power transmission lines, excavation costs can be reduced.

[5] During maintenance work on communication lines inside a manhole, the maximum yield voltage applied to the human body is only the voltage generated over one manhole section at most, so the risk level is extremely low.

'6} As described above, since the amount of dielectricity can be canceled out or reduced, a safety device such as an induced voltage suppression coil is not required.

[Brief explanation of the drawing]

Figure 1 is a diagram of the electromagnetic conduction voltage distribution diagram generated by the R phase, S phase, and T phase of the 3-phase underground power transmission line.
B}' An explanatory diagram showing each imaginary part, Figure 2 shows the principle of crossing. The horizontal example is a plan view showing that the power transmission line is laid parallel to the T-phase, the legs are a cross-sectional view showing the positional relationship with the power transmission line, and Figure 3 is a cross-sectional view showing that the legs are laid in parallel on top of the T-phase transmission line. FIG. 4 is an explanatory diagram showing an example of a simulation experiment of cross installation, and FIG. 5 is an explanatory diagram showing an example of a beautiful experiment in an actual system. . In addition, 1... power transmission line, 2... communication line,
2'...Communication line when not crossing, 3...
··voltmeter. Atsushi 1 Figure Skin 2 Illustration 3 Figure Kai 4 Figure Tsutsuzu

Claims (1)

[Claims] 1 As shown in Figure 3, the axis passing through the center of the three-phase power lines (R.S.T.) arranged in a straight line at equal intervals on the same plane is X, and the axis passing through the center of the power line S arranged in the center is If the axis perpendicular to the axis X is Y, the power line (R.S.T.)
A method for laying an underground communication line, characterized in that communication lines are laid alternately in locations where the relationship Y^2=X^2-1/2 holds true, with the S phase symmetrical.