JPH063475B2 - Optical fiber zero-phase current transformer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical fiber zero-phase current transformer that detects a ground fault in a distribution line, particularly a three-phase distribution line.

[Prior Art] FIG. 2 shows a configuration of a conventional zero-phase current transformer shown on page 79 of "Transformer for Instrument" by Miho Ikeda, which was illuminated by Densho Shoin in August, 1937, for example. Figure, in the figure (1)
Is a three-phase power distribution line, and consists of each phase power line (1a), (1b), (1c). (2) is a conventional zero-phase current transformer, which is an iron core (21) through which the three-phase distribution line (1) penetrates and 2 wound around the iron core (21).
It consists of a secondary winding (22). (3) is the secondary winding of the zero-phase current transformer (2) (2
It is a secondary burden such as protection relays connected between both ends of 2).

The conventional zero-phase current transformer (2) is configured as described above. First, the principle of detecting the zero-phase current will be described. Three
The currents flowing through the phase distribution lines (1a), (1b), (1c) of the phase distribution line (1) are only the positive and negative phase components in a steady state. Since the magnetic flux induced in the iron core (21) is induced by a magnetic field that is a combination of magnetic fields proportional to the positive and negative phase currents of each phase, the magnetic flux in the iron core (21) at steady state is zero. . Therefore, no current flows in the secondary winding (22) wound around the iron core (21).

Next, when a ground fault occurs in the three-phase distribution line (1), a zero-phase current that does not become zero even if the three-phase currents are combined flows, so a magnetic flux is induced in the iron core (21). A secondary current proportional to the zero-phase current flows through the secondary winding (22).

The zero-phase current transformer (2) is provided with an iron core (21) that collectively surrounds the three-phase distribution line (1), so that the zero-phase current that flows when a ground fault as described above occurs is highly sensitive. Is to detect the ground fault of the three-phase distribution line (1) by disconnecting the three-phase distribution line (1) installed in the premises of the substation where the ground fault occurred and to prevent the spread of the accident. There is.

[Problems to be Solved by the Invention] In recent years, even in the event of a ground fault, there is a demand for means that can detect the accident point early and accurately in order to limit the power outage section and shorten the recovery time as much as possible. Has been done. Therefore, it is necessary to install a large number of zero-phase current transformers (2) not only in the substation premises but also in the middle of the three-phase distribution line (1). But,
The conventional zero-phase current transformer (2) is a three-phase distribution line (1) with one iron core (21).
Due to the structure surrounded by, the iron core (21) is too large to be installed on the outdoor distribution pole, and the iron core (21) of the conductor is 3
Since the phase distribution line (1) is surrounded, there is a problem that it may cause an accident to spread due to the occurrence of lightning.

The present invention has been made to solve such a problem, and is suitable for being installed on a distribution pole, is lightweight,
Moreover, it is an object of the present invention to obtain an optical fiber zero-phase current transformer in which there is no fear of expanding or inducing an accident.

[Means for Solving Problems] In the optical fiber zero-phase current transformer according to the present invention, a magnetostrictive material is applied to the surface instead of the iron core and the secondary winding of the conventional zero-phase current transformer. An optical fiber surrounds a three-phase distribution line, and an optical distributor and a light emitting element, an optical multiplexer and a light receiving element are connected to each end thereof.

[Operation] In a three-phase distribution line accident, only the magnetostrictive material-coated optical fiber receives a magnetic field proportional to the zero-phase current, and the magnetostrictive material on the surface expands and contracts, which changes the optical fiber length.
The light passing through the magnetostrictive material-coated optical fiber and the light passing through another magnetostrictive material-coated optical fiber have a difference in time to reach the optical multiplexer, so that a phase difference occurs between the two lights. Since this phase difference is proportional to the magnitude of the zero-phase current, it is possible to detect the zero-phase current of the three-phase distribution line by detecting this phase difference.

[Embodiment] FIG. 1 is a block diagram partially showing an embodiment of the present invention. As in the case of FIG. 2, (1) is a three-phase distribution line, and (1a), (1b) , (1C) are electric wires for each phase of the three-phase distribution line (1). ( 2B ) is an optical fiber zero-phase current transformer according to the present invention. The three-phase distribution line (1) surrounds the three-phase distribution line (1).
A single-mode optical fiber that is wound around and has a surface coated with a magnetostrictive material [hereinafter referred to as a magnetostrictive material coated optical fiber. ] (4A) and a signal converter (5A) connected between both ends of this magnetostrictive material-coated optical fiber (4A). This signal converter (5A) is a light emitting element such as a light emitting diode (6), and an optical distribution connected between the output side of this light emitting element (6) and one end of the magnetostrictive material coated optical fiber (4A). (11), an optical multiplexer (1 ) connected to the other end of the magnetostrictive material coated optical fiber (4A)
2), the light receiving element (9) that is connected to the output side of this optical multiplexer (12) and converts light into electricity, and the electric signal obtained by this light receiving element (9) is converted into a signal proportional to the zero-phase current. Electronic circuit to convert (1
0), and another magnetostrictive material-coated light that is connected between the optical distributor (11) and the optical multiplexer (12) and has the same processing and the same length as the magnetostrictive material-coated optical fiber (4A). Built-in fiber (4B).

In the optical fiber zero-phase current transformer (2B) configured as described above, the light emitted from the light emitting element (6) is divided by the optical distributor (11), one of which is a magnetostrictive material-coated optical fiber (4A). Other magnetostrictive material applied on the other side between the optical distributor (11) and the optical multiplexer (12), and the magnetostrictive material applied on the optical multiplexer (12) through the optical fiber (4B). The light from the optical fiber (4A) is combined and photoelectrically converted by the light receiving element (9).

Normally, the light passing through the magnetostrictive material-coated optical fibers (4A) and (4B) has the same optical fiber length, so at the same time the optical multiplexer (12)
However, in the event of a three-phase power distribution line (1) accident, only the magnetostrictive material-coated optical fiber (4A) receives a magnetic field proportional to the zero-phase current, and the magnetostrictive material-coated optical fiber (4A) is removed. As it expands and contracts, and the optical fiber length changes accordingly, the light that passes through the magnetostrictive material-coated optical fiber (4A) and the light that passes through another magnetostrictive material-coated optical fiber (4B) enter the optical multiplexer (12). Since there is a difference in the arrival time, there is a light phase difference between the two lights. This phase difference is proportional to the magnitude of the zero-phase current.
It is possible to detect the zero-phase current in (1). This method is called the Matsuhatsu Ender interference system, but the heterodyne detection method or the homodyne detection method is used as a method for extracting the phase difference of light as an electrical output, and the laser and the avalanche photodiode are used as the light emitting element and the light emitting element. used.

[Advantages of the Invention] As described above, according to the present invention, a magnetostrictive material-coated optical fiber surrounding a three-phase distribution line, a light emitting element and a light distributor, a light receiving element and an optical multiplexer, and other magnetostrictive material coated By providing a signal converter including an optical fiber,
Since the zero-phase current of the three-phase distribution line can be detected without using an iron core as in the past, a compact, lightweight, and safe optical fiber zero-phase current transformer can be obtained because the optical fiber is an insulator. There is an effect that it can be installed on a distribution pole, which was difficult in the past.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram partially showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional zero-phase current transformer. In the figure, (1) is a 3-phase distribution line, (2B) is an optical fiber zero-phase current transformer, (4A) and (4B) are magnetostrictive material coated optical fibers, (5A)
Is a signal converter, (6) is a light emitting element, (9) is a light receiving element, (10) is an electronic circuit, (11) is an optical distributor, and (12) is an optical multiplexer. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An optical fiber which is wound so as to surround a three-phase distribution line and whose surface is coated with a magnetostrictive material, an optical distributor connected to one end of this optical fiber, and an optical distributor connected to this optical distributor. A light emitting element, an optical multiplexer connected to the other end of the optical fiber, a light receiving element connected to the optical multiplexer, and a light receiving element connected between the optical distributor and the optical multiplexer, the same as the optical fiber. An optical fiber zero-phase current transformer, comprising: a signal converter having another optical fiber having a length and having a surface coated with a magnetostrictive material;