JP2843451B2 - Optical fiber cable for high voltage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a high voltage optical fiber cable suitable for use in a place where a high voltage is applied.

[0002]

2. Description of the Related Art Conventionally, when it is necessary to measure the current or voltage flowing through a high-voltage transmission line such as a line or a bus in a transmission line, a substation, a power plant, or the like, and to monitor the current or voltage with a ground management facility. A technique is known in which an optical output signal from a sensor such as an optical CT or an optical PT provided on a transmission line is transmitted to a grounding side by an optical fiber inserted through a central portion of an insulator. If the optical fiber built-in insulator that inserts the optical fiber in the center cannot be installed near the power transmission line, and the space between the sensor provided on the transmission line and the optical fiber built-in insulator is wired, the optical fiber must be installed outdoors. Because it is exposed to harsh environments, usually, considering the weather resistance, mechanical strength, cost, etc., cover with steel cored aluminum stranded wire or simply aluminum stranded wire, or use metal reinforcing material along optical fiber. A reinforcing optical fiber is used in which a metal reinforcing material and an optical fiber are integrally coated with a fluororesin or the like. Here, such a reinforced optical fiber covered with a steel cored aluminum stranded wire or an aluminum stranded wire has a small outer diameter, so when a high voltage is applied, the air around the reinforced optical fiber undergoes dielectric breakdown, and corona discharge occurs. easy. The occurrence of a visible corona scares nearby residents, and the occurrence of radio noise voltage (RIV) also damages residents. Therefore, in order to suppress these corona discharges, optical fiber cables for high voltage use thicker aluminum stranded wires, aluminum stranded wires or fluororesin coatings with steel cores, or use lightweight shield tubes made of aluminum, etc. It is designed to be thicker by further coating on the aluminum stranded wire, aluminum stranded wire, and fluororesin coating.

When a voltage is applied to a conductor, the lines of electric force concentrate on the surface of the conductor, and the gradient of the potential on the surface of the conductor is as shown in the following equation (1).

Gmax = V / rlog (D / r) Gmax = Gradient of surface potential of conductor (kV / mm) V = Maximum value of normal to ground voltage (kV) r = Radius of conductor (cm) D = 2 of ground height Times (cm)

[0004] Here, 154k which is often used at present is used.
V-type, 275 kV-type, and 500 kV-type voltage transmission lines are connected to sensors and connected to sensors to provide optical fiber cables (using aluminum or other smooth metal stranded wires) and change the radius of the optical fiber cables. Then, the surface potential gradient of the optical fiber cable was calculated. Table 1 shows the calculation results.

[0005]

[Table 1]

Generally, the surface potential gradient of a conductor when a visible corona is generated is said to be 20 kV / cm. Therefore, if the surface potential gradient is set to 18 kV / cm or less in view of the tolerance of 10%, corona does not occur in the optical fiber cable connected to the transmission line. From Table 1 above, the thickness of the optical fiber cable at this time is about 17 mm or more in the 154 kV system and about 32 mm in the 275 kV system.
As described above, a diameter of about 62 mm or more is required for the 500 kV system.

[0007]

However, increasing the thickness of the optical fiber cable as in the above-mentioned conventional method requires a member for covering the optical fiber, for example, an aluminum stranded wire with a steel core, or an increase in the amount of aluminum coating material. In addition to this, the load of the optical fiber cable itself is applied to the joint between the sensor and the optical fiber and the optical fiber outlet of the optical fiber built-in insulator, and the structure becomes large to cope with the load, and damage may occur in this part The nature increases. The present invention has been made in view of the above-described conventional problems, and can reduce the material by reducing the weight of a high-voltage optical fiber cable having a thickened reinforced optical fiber coating, and can completely prevent the occurrence of corona discharge. An object of the present invention is to provide an optical fiber cable for high voltage.

[0008]

In order to achieve the above object, according to the present invention, a high-voltage optical fiber cable is formed by adding a predetermined diameter to a reinforced optical fiber having a metal coating or a metal reinforcing material on the optical fiber. A configuration in which the shield tube having the shield tube is attached at one or more intervals and the length of the interval is set to a length at which the reinforcing optical fiber of the portion provided with the interval is shielded by the shield tube adjacent to the interval. And The correlation between the radius of the shield tube and the surface potential gradient of the shield tube is as shown in the above formulas and Table 1. The diameter of the shield tube in the present invention is such that the surface potential gradient of the shield tube does not cause corona. This is a value previously calculated from the above equation 1 for each voltage class so as to obtain the surface potential gradient.

[0009]

The optical fiber cable for high voltage of the present invention is a cable in which a shield tube is provided at a certain interval on a reinforced optical fiber having a metal coating or a metal reinforcing material on the optical fiber and coated with a fluororesin. The use of less coating material and the lower weight of the cable itself compared to conventional high-voltage optical fiber cables with a thicker overall coating of the cable, thus reducing the load burden on the cable attachment area. Can be.
Further, in the present invention, as shown in FIG. 1, when a space of length A is provided in the shield tube 11 having a diameter d designed and calculated so as to have a surface potential gradient that does not generate corona, the space formed in this space portion is formed. The length A of the interval is set so that the equipotential lines C do not become dense enough to generate corona near the reinforcing optical fiber, so that corona does not occur in the high-voltage optical fiber cable. When the diameter of the shield tube is increased, the length A of the interval between the shield tubes can be increased, so that the number of the shield tubes to be attached can be reduced, and the efficiency in production is improved. However, needless to say, if the diameter of the shield tube is too large, the shield tube becomes heavy.

In order to completely prevent the corona discharge of the conductor, the surface potential gradient of the conductor is set at 18 in consideration of the influence of rain or the like.
According to the description in Table 1, the diameter d of the shield tube 11 of the high-voltage optical fiber cable is about 20 mm or more in the 154 kV system.
In a 275 kV system, about 32 mm or more is required, and in a 500 kV system, about 62 mm or more. However, if the diameter of the shield tube is too large, the number of shield tubes provided in a unit length of the optical fiber cable is reduced, but the weight of the shield tube is increased, and the amount of material used is increased. Therefore, in the case of the 154 kV system, about 20 to 35 mm, 27
It is preferable that the width be about 32 to 45 mm for a 5 kV system and about 62 to 80 mm for a 500 kV system. In addition, if the length of the shield tube is long L, a large amount of the material of the shield tube is required and the load of the high voltage optical fiber cable itself becomes large, while if the length L is short, many shield tubes are provided. Since it must be performed, the production is complicated, and the design may be made arbitrarily in consideration of this point.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, and the effects thereof will be described with reference to the drawings. Example 1 A reinforced optical fiber (having a cross-sectional area of 55 mm ² ) in which an optical fiber is coated with aluminum containing a steel core has a length (L).
A high-voltage optical fiber cable in which an aluminum shield tube 11a having a diameter of 50 mm and a diameter (d) of 35 mm is discontinuously applied at intervals indicated by a length A is prepared. Was measured.
The measurement result is shown in FIG. 2 (reference numeral 11a in the figure). According to this graph, the high-voltage optical fiber cable covered with the shield tube 11a has a visible corona required for a 154 kV line if the interval length A is up to 150 mm (about four times the diameter d of the shield tube). Dissipation voltage 8
It shows a visible corona extinction voltage of 9 kV (154 kV × 1 / √3) or more, and can suppress generation of corona.

Example 2 An optical fiber cable for high voltage was prepared in the same manner as in Example 1 using an aluminum shield tube 11b having a length (L) of 100 mm and a diameter (d) of 35 mm, and the interval A was varied. Then, the visible corona annihilation voltage was measured, and the measurement result is shown in FIG. 2 (reference numeral 11b in the figure). According to this graph, the generation of corona can be suppressed if the interval length A of the high-voltage optical fiber cable to which the shield tube 11b is attached is up to 150 mm (about four times the diameter d of the shield tube).

Embodiment 3 An optical fiber cable for high voltage using an aluminum shield tube 11c having a length (L) of 150 mm and a diameter (d) of 35 mm is the same as that of the first and second embodiments. The measurement was performed, and the measurement result is shown in FIG. 2 (reference numeral 11c in the figure). According to this graph, the generation of corona can be suppressed if the interval length A of the optical fiber cable for high voltage to which the shield tube 11c is attached is up to 150 mm (about four times the diameter d of the shield tube).

Example 4 A high voltage applied discontinuously at intervals indicated by length A in the same manner as in Example 1 using an aluminum shield tube 11d having a length (L) of 140 mm and a diameter (d) of 45 mm. Optical fiber cable was prepared, the visible corona annihilation voltage was measured by changing the length A of the interval, and the measurement results were shown in FIG.
(Reference numeral 11d in the figure). According to this graph, the high-voltage optical fiber cable having the shield tube 11d is required for a 275 kV system line if the interval length A is up to 150 mm (about 3.3 times the diameter d of the shield tube). Visible corona annihilation voltage 159 kV (27
5 kV × 1 / √3) or higher, indicating a visible corona extinction voltage of
Corona generation can be suppressed.

Example 5 A high voltage applied discontinuously at intervals of length A as in Example 1 using an aluminum shield tube 11e having a length (L) of 150 mm and a diameter (d) of 80 mm. Optical fiber cable was prepared, the visible corona annihilation voltage was measured by changing the length A of the interval, and the measurement results were shown in FIG.
(Reference numeral 11e in the figure). According to this graph, the high-voltage optical fiber cable having the shield tube 11e attached thereto is required for a 500 kV line if the interval length A is up to 180 mm (about 2.3 times the diameter d of the shield tube). Visible corona annihilation voltage 289 kV (50
0 kV × 1 / √3) or higher, which indicates a visible corona extinction voltage,
Corona generation can be suppressed.

As described above, if a high-voltage optical fiber cable is formed by attaching a shield tube to an optical fiber with a metal coating or a reinforcing optical fiber provided with a metal reinforcing material at intervals, and forming a high-voltage optical fiber cable, the conventional cable coating can be eliminated. Compared with a high-voltage optical fiber cable that is thickly applied as a whole, the amount of coating material used can be reduced and the weight of the cable itself can be reduced, so that the load burden on the cable attachment portion and the like can be reduced. Further, even if an interval is provided in the shield tube, by setting the interval length A so that the equipotential lines C formed in this interval are not so dense as to generate a corona near the reinforcing optical fiber, a high voltage can be obtained. Does not impair the corona generation prevention effect of the optical fiber cable.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment of an optical fiber cable for high voltage according to the present invention.

FIG. 2 is a graph illustrating a relationship between a length A of a shield tube interval of a high-voltage optical fiber cable according to the present invention and a visible corona extinction voltage.

[Explanation of symbols]

10: reinforced optical fiber, 11: shield tube, A
... shield tube spacing length, d ... shield tube diameter, L ... shield tube length, C ... equipotential lines.

Claims (1)

(57) [Claims] 1. A shielded tube having a predetermined diameter is attached to an optical fiber having a metal coating or a metal reinforcing material and a reinforcing tube provided with a metallic reinforcing material at one or more intervals. A high-voltage optical fiber cable, wherein the length of the reinforcing optical fiber in the space provided is set to be shielded by a shield tube adjacent to the space.