JPS6350765A - Optical fiber zero phase current transformer - Google Patents

Abstract

PURPOSE:To obtain a small-sized light wt. safe zero phase current transformer, by winding an optical fiber around a three-phase distribution line so as to surround the same and connecting a signal converter between both ends thereof. CONSTITUTION:An optical fiber zero phase current transformer 2A is constituted of the single mode optical fiber 4 wound around a three-phase distribution line 1 and the signal converter 5 connected between both ends of the optical fiber 4. The converter 5 has a light emitting element 6, a polarizer 7, a light receiving element 9 and an electronic circuit 10 mounted therein. The light emitted from the element 6 is linearly polarized by the polarizer 7 permitting the passage only of light of a wave component in one direction to be incident to the optical fiber 4. When a magnetic field is applied to the optical fiber 4, the plane of polarization thereof rotates in proportion to the magnetic field applied by Faraday effect. Now, when an earth accident is generated, as the result of the flowing of a zero phase current to the distribution line 1, the circumference integration of the magnetic field surrounding said line 1 becomes the value proportional thereto and the plane of polarization of the linearly polarized light passing through the optical fiber 4 also receives the rotation proportional to the zero phase current and the electric signal photoelectrically converted by the element 9 through the detector 8 also changes to make it possible to detect the zero phase current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical fiber zero-phase current transformer for detecting a ground fault in a %Tlc three-phase distribution line.

[Conventional technology]

Figure 3 is a configuration diagram showing a conventional zero-phase current transformer, as shown on page 79 of ``Instrument Transformers'' by Mihoji Ikeda, published by Denkishoin in April 1960, for example. , f is a three-phase distribution line, and each phase line (/&), (/b
)A/c). C) is a conventional zero-phase current transformer, consisting of an iron core CM through which the J-phase power distribution @ (/) is passed, and a primary winding (C 2) wound with VC on this iron core (s/). (, 71 is a primary load such as an h-holding relay connected between both ends of the primary windings (2) of the zero-phase current transformer (, 2).

The conventional zero-sequence current transformer (C) is configured as described above, and first, the principle of detecting zero-sequence current will be explained. 3
Each phase distribution line (/l) (/a), (/b'J, (I
In steady state, the current flowing through C> is only the positive phase component and the negative phase component. The magnetic flux induced in the iron core (2/) is induced by a magnetic field that is a combination of magnetic fields proportional to the positive and negative phase currents of each phase, so the magnetic flux in the iron core (2/) at steady state is zero. It is. Therefore, the secondary winding (here) with K windings on the iron core (s/)
No current flows through.

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

The zero-phase current transformer (C) is used to detect ground faults in the three-phase distribution line (C) by enclosing the three-phase distribution line (1) with high sensitivity and detecting ground faults in the three-phase distribution line (C). The 3-phase distribution line (C) where the ground fault occurred was disconnected to prevent the accident from spreading.

[Problem that the invention seeks to solve]

In recent years, even when a ground fault occurs, there has been a demand for means that can quickly and accurately locate the point of the fault in order to limit the power outage section as much as possible and shorten the restoration time. For this reason, zero-phase current transformers (-) are installed not only in substation premises, but also in
It is necessary to install many pieces in the middle of the phase distribution line (C). However, because the conventional zero-phase current transformer (C) has a structure in which the three-phase distribution line (C) is surrounded by seven iron cores (-/), The iron core (C/) is too large to be installed on an outdoor distribution pole, and the conductive iron core (2/) surrounds the three-phase distribution line (C), which increases the risk of accidents in the event of a lightning strike, etc. There were problems such as causes.

This invention was made to solve these problems, and provides an optical fiber zero-phase current transformer that is suitable for installation on power distribution poles, is lightweight, and has no risk of aggravating or inducing accidents. The purpose is to obtain.

[Failure to solve the problem]

The optical fiber zero-phase current transformer according to the present invention winds an optical fiber to surround a three-phase distribution line instead of the iron core and primary winding of a conventional zero-phase current transformer, and emits light between both ends of the optical fiber. A signal converter including an element and a light receiving element is connected.

[For production]

Optical fibers can be used to measure magnetic fields because they have a Faraday effect in which the plane of polarization of linearly polarized light passing through them rotates in proportion to the magnetic field applied to the optical fibers.

〔Example〕

FIG. 1 is a block diagram partially showing the configuration of an embodiment of the present invention, and as in the case of FIG. ) is each phase wiring of the three-phase distribution line c). (A) is an optical fiber zero-phase current transformer according to the present invention, in which a single-mode optical fiber (hereinafter referred to as optical A signal converter (s) connected between both ends of this optical fiber (gl)
). This signal converter (jl) includes a light emitting element (6) such as a light emitting diode, a light receiving element (ql) that converts the connection between the output side of this light emitting element (6) and one end of the optical fiber Kl, and this light receiving element (ql), which converts the connection into electricity. It has a built-in electronic circuit (10) that converts the electric signal obtained by the element (?) into a signal proportional to the zero-sequence current.

After being made into linearly polarized light by While moving through C≠),
Its plane of polarization rotates in proportion to the applied magnetic field. The linearly polarized light that has undergone rotation of the plane of polarization and is emitted from the other end of the original fiber (gl) passes through the analyzer (t) and is converted into an electrical signal by the light receiving element (9). Waves in one direction 4) Only the J1 component of light passes through, so the path of the light passing through the analyzer is the rotation angle of the plane of polarization! ic
Accordingly, the electric signal obtained by the light receiving element (9) also changes.

In steady state, if the magnetic field surrounding the 5.7-phase wiring is integrated around the line, it becomes zero, so the polarization received by the polarized light passing through the 3-phase distribution line The rotation of the wavefront also becomes zero at the output end of the optical fiber.

However, when a ground fault occurs in the 3-phase distribution line (C), as a result of the flow of the Vc5 thick phase current, the circuit integral of the magnetic field surrounding it becomes a value proportional to the zero-sequence current, and the optical fiber (≠) The polarization plane of the linearly polarized light passing through is also rotated in proportion to the zero-sequence current, and the electrical signal photoelectrically converted by the light receiving element (te) through the analyzer fffl also changes, making it possible to detect the zero-sequence current.

Next, FIG. 1, which is a block diagram partially showing another embodiment (B) of the present invention, will be described. (t*
) is a single-mode optical fiber that is wound around a three-phase distribution line and whose surface is coated with magnetostrictive material.
B") is this optical fiber coated with magnetostrictive material (4
is a light emitting element (6) and a solar fiber coated with magnetostrictive material (ψA)
The optical distributor (/) is connected between one end of the optical fiber ζψA) coated with a p-magnetostrictive material and the other end of the photodetector (?A).
) is an optical multiplexer connected between the Light emitting element (6)
The light emitted from the is split by a light splitter (//), one passes through a magnetostrictive material-coated optical fiber (taA), and the other is connected between the light splitter (l/) and the photosynthesizer (/-). An optical multiplexer (/
It is combined with the light from the magnetostrictive material-coated solar fiber (U) in the photodetector element (R1) and photoelectrically converted.

Usually, a solar fiber coated with magnetostrictive material (rH,'+, (qs
) Since the optical fiber lengths are the same, the light that passes through the optical multiplexer (/co) VC reaches the optical multiplexer (/co) at the same time. Because the fiber length changes, there is a difference in the time between the light passing through the magnetostrictive material-coated optical fiber (u*) and the light passing through the magnetostrictive material-coated optical fiber (uB), reaching the optical multiplexer (/co) VC. A phase difference occurs between the two lights. This phase difference is proportional to the magnitude of the zero-sequence current, so by detecting this phase difference, it is possible to output the J phase. This method Matsuha Tsuender
Although called an interference system, a heterogain detection method or a homodyne detection method is used as a method for extracting the phase difference of light as an electrical output, and a laser and an avalanche photodiode are used as a light emitting element and a light receiving element.

〔Effect of the invention〕

As explained above, by providing an optical fiber surrounding the Ic and J phases, and a signal converter including a light emitting element and a light receiving element, the present invention can reduce the zero of a three-phase distribution line without using an iron core as in the conventional case. Since the phase current can be detected, an optical fiber zero-phase current transformer that is small, lightweight, and safe because the optical fiber is an insulator can be obtained, and it can also be installed on distribution poles, which was previously difficult. There is.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram partially showing one embodiment of the present invention; Fig. 1 is a block diagram partially showing another embodiment; Fig. 3 is a conventional block diagram; FIG. 2 is a configuration diagram showing a zero-phase current transformer of FIG. In the figure, (C is the J phase arrangement string line (CoA) and (sB”
) is an optical fiber zero-phase current transformer, (q) is an optical fiber, (t
tA) and ('IB') Y'i magnetostrictive material coated optical fibers, (5) and (5A) are signal converters, (6) is a light emitting element,
(7) is a polarizer, (g) is an analyzer, (?1 is a light receiving element,
(10) is an electronic circuit, (//) is an optical distributor, (/ko')
f'i is a photosynthesizer. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. 1 ;3 line RL- with line 2A 7 fill with 1L phase 1 hole 7 fill 0 2B: f fiber” zero chant 1 whisper 4A, 4
B Discretion ↑ 10 perfect i Iil to ηA7

Claims (3)

[Claims] (1) An optical fiber zero characterized by comprising an optical fiber wound so as to surround a three-phase distribution line, and a signal converter connected between both ends of the optical fiber and including a light emitting element and a light receiving element. Phase current transformer. (2) The signal converter includes a polarizer connected between the output side of the light emitting element and one end of the optical fiber, and an analyzer connected between the other end of the optical fiber and the input side of the light receiving element. An optical fiber zero-phase current transformer according to claim 1, characterized in that the optical fiber zero-phase current transformer includes: (3) The optical fiber according to claim 1, wherein the optical fiber is a single mode optical fiber whose surface is coated with a magnetostrictive material, and the signal converter utilizes Matsuhatsu-Ender interference. Fiber zero-phase current transformer.