JPH0829459A - Overcurrent detecting method and overcurrent detecting device - Google Patents

Abstract

PURPOSE:To detect an overcurrent without requiring a complicated electric circuit, and also with high accuracy. CONSTITUTION:A polarizer 210 and an analiser 230 are arranged in such a positional relationship that the relative angle between the optical plane of polarization after passing through both the polarizer 210 and a Faraday element 220 and that of the analiser 230 is 90 degrees, and it is constituted in such a way that in the magnitude of the magnetic field produced by the flow of a current in an ordinary load condition, the detection signal based on an optical output becomes zero, and in a large magnetic field by which an overcurrent is passed, the detection signal based on the optical output can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent detecting method and an overcurrent detecting device, and more particularly to an overcurrent detecting a change in Faraday rotation angle due to an overcurrent using a magneto-optical effect element as a change in optical output. The present invention relates to a detection method and an overcurrent detection device.

[0002]

2. Description of the Related Art Conventionally, the measurement of a magnetic field by light utilizes a phenomenon in which a plane of polarization of linearly polarized light traveling in a substance parallel to the direction of the magnetic field is rotated, that is, the Faraday effect. FIG. 3 is a diagram showing the principle thereof. The light linearly polarized by the polarizer rotates its polarization plane by the external magnetic field while propagating in the magneto-optical effect element (Faraday element), and the analyzer rotates the rotation. The light intensity is converted according to the angle φ. The rotation angle φ on this plane of polarization is generally expressed by the following equation 1.

[0003]

Where φ is the Verdet constant of the Faraday element, H is the applied magnetic field, and L is the thickness of the Faraday element. When the relative angle (optical bias) between the polarization directions of the polarizer and the analyzer is φ _B , the light intensity P output from the analyzer is represented by the following equation 2.

[0004]

## EQU2 ## P = P ₀ cos ² (φ _B −φ) where P ₀ is the amount of incident light on the Faraday element. When the optical bias φ _B is set to 45 ° so that the magnetic field detection sensitivity is maximized and the linearity is optimized, the light intensity P output from the analyzer is expressed by the following equation (3).

[0005]

## EQU3 ## P = (1/2) P ₀ (1 + sin2φ) Here, assuming that the magnetic field to be measured is AC magnetic field H = H ₀ sinωt, and 2φ << 1, the light intensity P output from the analyzer is It is represented by the following equation (4).

[0006]

Equation 4] _{P = (1/2) P 0 (} 1 + 2V · H 0 · L · sinωt) Thus, a polarizer, a magneto-optical effect element (Faraday element), by combining an analyzer, the magnitude of the applied magnetic field It is possible to obtain light with an intensity proportional to the intensity.

An optical magnetic field measuring device includes an optical magnetic field sensor unit including a polarizer, a magneto-optical effect element (Faraday element), and an analyzer, and a signal processing unit including an optical transmitter, an optical receiver, an amplifier, and the like. It is composed by. FIG. 4 shows a configuration example of the optical magnetic field measuring device. In FIG. 4, the light emitted from the light emitting diode of the optical transmitter propagates through the optical fiber, and the light intensity is converted by the optical magnetic field sensor unit. The light of which the light intensity has been converted is input to the light receiving element of the optical receiver through the light receiving optical fiber and subjected to light-voltage conversion. The applied magnetic field can be measured by extracting only the light modulation component (AC component) from the voltage signal subjected to the light-voltage conversion.

By the way, the relationship between the amount of light transmitted through the optical magnetic field sensor and the relative angle (optical bias) between the polarizer and the analyzer has the characteristics shown in FIG. As can be seen from this characteristic, the point where the relative angle (optical bias) between the polarizer and the analyzer is π / 4 (45 °) has the maximum linearity (the linearity error is the minimum). A polarizer and an analyzer are used in combination so as to serve as a reference point.

Therefore, when the current to be detected is
The amount of current flowing through the electric wire can be detected by detecting the magnetic field generated by this current and taking out an output proportional to the magnetic field. When the optical magnetic field sensor is used for such a purpose, it is necessary to use it so that the relative angle (optical bias) between the polarizer and the analyzer is π / 4 (45 °).

[0010]

For this reason, when an overcurrent is to be detected, the light intensity is converted by the photomagnetic field sensor and then input to the light receiving element for light-voltage conversion, and the light-voltage conversion is performed. The voltage signal is amplified and then filtered to compare noise-free voltage signal with the reference signal, and if the voltage signal is larger than the reference signal, an overcurrent signal is generated. There was a problem that an electric circuit was needed. In addition, there is a problem that the electric circuit becomes complicated. Further, when the overcurrent is determined, the voltage signal that has been amplified and passed through the filter is compared with the reference signal, which causes a problem in the overcurrent determination accuracy.

Further, depending on the circuit element used, it is necessary to consider the temperature characteristic of the circuit element, which causes a problem of high cost. Furthermore, in order to ensure the reliability of this type of sensor, it has to be inspected periodically, and the maintenance thereof is not easy. Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to make it possible to detect an overcurrent with high accuracy without requiring a complicated electric circuit.

[0012]

A first feature of the configuration of the present invention is an overcurrent detection method for detecting a change in Faraday rotation angle due to an overcurrent as a change in optical output using a magneto-optical effect element. Therefore, the polarizer and the analyzer are arranged in such a positional relationship that the relative angle between the polarization plane of the light after passing through the polarizer and the magneto-optical effect element and the polarization plane of the analyzer is 90 degrees, and a normal load is applied. The detection signal based on the optical output is set to zero in the magnitude of the magnetic field generated by the current flowing in the state, and the detection signal based on the optical output is obtained in the large magnetic field generated by the overcurrent flowing. There is something I did.

A second feature of the present invention is an overcurrent detecting a change in Faraday rotation angle due to an overcurrent by using a magneto-optical effect element having no natural optical rotatory power as a change in optical output. A detection method, in which the polarizer and the analyzer are arranged in a positional relationship such that the relative angle of the polarization planes of the polarizer and the analyzer is 90 degrees, and a current flows in a normal load state. The detection signal based on the optical output is set to zero in the magnitude of the generated magnetic field, and the detection signal based on the optical output is obtained in the large magnetic field generated by the overcurrent.

A third feature of the present invention is an overcurrent detecting device which detects a change in Faraday rotation angle due to an overcurrent as a change in optical output by using a magneto-optical effect element. , A polarizer that linearly polarizes the light emitted by the light source, a magneto-optical effect element that Faraday-rotates the light linearly polarized by the polarizer according to the strength of the magnetic field, and the magneto-optical It has an analyzer that converts the light Faraday-rotated by the effect element into a light intensity corresponding to the Faraday rotation angle, and a light-receiving element that emits an output signal when the light intensity from the analyzer becomes a predetermined value or more. The optical polarization plane after passing through the optical element and the magneto-optical effect element and the polarization plane of the analyzer have a relative angle of 90 degrees.

Further, the fourth structural feature of the present invention is as follows.
An overcurrent detection device for detecting a change in Faraday rotation angle due to an overcurrent as a change in optical output by using a magneto-optical effect element having no natural optical rotatory power, the light emitting source emitting light, and the light emitting source. The linearly polarized light emitted by the polarizer, the magneto-optical effect element that does not rotate the linearly polarized light by the Faraday according to the strength of the magnetic field, and the natural optical activity. An analyzer that converts the light Faraday-rotated by the magneto-optical effect element into a light intensity corresponding to the Faraday rotation angle, and a light-receiving element that emits an output signal when the light intensity from the analyzer exceeds a predetermined value. That is, the polarizer and the analyzer are arranged in such a positional relationship that the relative angle between the polarization planes of the polarizer and the analyzer is 90 degrees.

[0016]

In the present invention configured as described above, the detection signal based on the optical output is set to zero when the magnitude of the magnetic field generated by the current flowing in the normal load state is zero. In a large magnetic field generated by the flow of current, a detection signal based on the optical output can be obtained.
You will be able to get the off signal. Since the on / off signal switching corresponding to the presence / absence of the overcurrent is instantaneously performed, the overcurrent can be detected instantaneously.

Further, the polarizer and the magneto-optical effect element are arranged such that the relative angle between the plane of polarization of light after passing through the magneto-optical effect element and the plane of polarization of the analyzer is 90 degrees, or that there is natural optical rotatory power. When a magneto-optical effect element is not used, the relative angle between the polarization planes of the polarizer and the analyzer is 90.
The light receiving element detects the presence or absence of optical output from the analyzer and outputs an overcurrent signal from this light receiving element. No special circuit is required, and the accuracy of overcurrent determination is remarkably improved.

Furthermore, since a complicated electric circuit is not used at all, it is not necessary to consider the temperature characteristic of the electric circuit, so that this kind of device can be manufactured at a low cost. Further, since no complicated electric circuit is used, the reliability of the sensor is improved, and its maintenance is easy, which is a remarkable effect.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an overcurrent detecting device of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of an embodiment of an overcurrent detection device of the present invention. The overcurrent detection device of the present embodiment includes a light emitting source 100, a polarizer 210, and a magneto-optical effect element 220 including a Faraday element. And analyzer 23
The optical magnetic field sensor 200 is composed of 0 and the light receiving element 300. The polarizer 210 and the analyzer 230 are made of a dielectric film or natural calcite, and the light receiving element 300 is a photodiode, a phototransistor, a light firing thyristor, etc. that detects the light intensity and converts it into an electric signal. Various photodetectors are preferably used.

Further, as the magneto-optical effect element 220, as the Faraday element having a self-rotating property, BSO, BG
O or the like is used. Further, as a Faraday element having no self-optical activity, a lead glass, a diamagnetic substance such as As ₄ Se or ZnSe, a ferromagnetic substance such as YIG, Tb-YIG, Bi-YIG, or FR-5 glass, CdMnTe or the like is used. A magnetic material or the like is used. Further, as the light emitting source 100, a He-Ne laser, an Ar ion laser, a laser diode, a light emitting diode (LED) or the like is preferably adopted.

Here, for example, B is used as a Faraday element.
When SO is used, the emission source 100 is 0.85 μ
A light source having a wavelength of m is used, and C is used as a Faraday element.
In the case of using dMnTe, the light emitting source 100 has a density of 0.
When a light source having a wavelength of 6 to 0.8 μm is used and lead glass is used as the Faraday element, a light source having a wavelength of 0.85 μm is used as the light emitting source 100.

In FIG. 1, a He-Ne laser, an Ar ion laser, a laser diode, a light emitting diode (LE
The light emitted from the light emitting source 100 made of D) or the like enters the polarizer 210 made of a dielectric film or natural calcite. The light incident on the polarizer 210 is linearly polarized by the polarizer 210 and then incident on the magneto-optical effect element 220 including the Faraday element described above. This Faraday element 2
The plane of polarization of the light incident on 20 undergoes Faraday rotation according to the strength of the magnetic field generated by the current flowing through the current-carrying conductor 400.

The light Faraday-rotated by the Faraday element 220 is incident on an analyzer 230 made of a dielectric film or natural calcite, and is converted into a light intensity according to the Faraday rotation angle by the analyzer 230. Then, the light is incident on the light receiving element 300 composed of a photodiode, a phototransistor, a light ignition type thyristor, etc.
With 0, the light intensity above a predetermined value is detected and converted into an electric signal.

Here, the polarizer 210 and the analyzer 230 are arranged so as to have the following positional relationship.
That is, when the Faraday element 220 made of BSO, BGO or the like and having a self-optical activity is used as the Faraday element 220, the polarizer 210 and the Faraday element are considered in consideration of the rotation of the polarization plane due to the self-optical activity of the Faraday element 220. The optical polarization plane after passing 220 and the polarization plane of the analyzer 230 are arranged in such a positional relationship that the relative angle is 90 degrees. Further, as the Faraday element 220, lead glass,
As ₄ Se, ZnSe, YIG, Tb-YIG, Bi-
In the case of using the Faraday element 220 having no self-rotating property such as YIG, CdMnTe, FR-5 glass, the polarizer 2 is used.
10 and the analyzer 230 are arranged in such a positional relationship that the relative angle of the polarization plane is 90 degrees.

Since the polarizer 210 and the analyzer 230 are arranged in such an arrangement relationship, as shown in FIG. 2, the plane of polarization of the light after passing through the polarizer 210 and the Faraday element 220 and the analyzer 230. The output light output from the analyzer 230 is zero at the point where the relative angle between the plane of polarization is 90 degrees and the point where the relative angle between the planes of polarization of the polarizer 210 and the analyzer 230 is 90 degrees.

Here, when a normal load current is flowing through the current-carrying conductor 400, the magnetic field generated by this current is small, so the Faraday rotation range of the Faraday element 220 is within the range A in FIG. 2A. Therefore, the output light output from the analyzer 230 has a small light intensity as shown by A in FIG. 2 (b), and thus the output light from A in FIG. 2 (b) is small.
When the light intensity is low as shown in
00 does not reach the minimum illuminance at which the light-receiving element 300 operates, the light-receiving element 300 cannot detect the light intensity and does not output its output signal.

In such a state, when an accident such as a short circuit or a ground fault occurs and an overcurrent flows through the current-carrying conductor 400,
Since the magnetic field generated by this overcurrent is large, the Faraday rotation angle of the Faraday element 220 is as large as B in FIG. 2A, and therefore the output light output from the analyzer 230 is shown in B of FIG. 2B. The light intensity is high. At a high light intensity as shown by B in FIG. 2 (b), the light receiving element 300 is in an operating state, and the light receiving element 300 detects the light intensity and emits its output signal.

As described above, in this embodiment, the signal based on the optical output is set to zero in the magnitude of the magnetic field generated by the current flowing in the normal load state, and the overcurrent flows. Since a signal based on the optical output is obtained in a large magnetic field generated thereby, it is possible to obtain an on / off signal corresponding to the presence or absence of overcurrent. Since the on / off signal switching corresponding to the presence / absence of the overcurrent is instantaneously performed, the overcurrent can be detected instantaneously.

Further, the polarizer 210 and the Faraday element 220 are arranged in such a positional relationship that the relative angle between the polarization plane of the light after passing through the Faraday element 220 and the polarization plane of the analyzer 230 is 90 degrees.
Alternatively, when a magneto-optical effect element having no natural optical rotatory power is used, the polarizer 210 and the analyzer 230 are replaced by the polarizer 21.
0 and the analyzer 230 are arranged in such a positional relationship that the relative angle of the plane of polarization is 90 degrees, the presence or absence of optical output from the analyzer 230 is detected by the light receiving element 300, and the light receiving element 30 is detected.
Since the overcurrent signal is generated from 0, no complicated electric circuit for overcurrent detection is required, and the accuracy of overcurrent determination is remarkably improved.

Furthermore, since a complicated electric circuit is not used at all, it is not necessary to consider the temperature characteristic of the electric circuit, and this type of device can be manufactured at a low cost. Further, since no complicated electric circuit is used, the reliability of the sensor is improved, and its maintenance is easy, which is a remarkable effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an overall configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing an output light intensity of an example of the present invention, in which (a) is a relative angle between an optical polarization plane after passing through a polarizer and a magneto-optical effect element and a polarization plane of an analyzer, and the output light intensity. And (b) is a diagram showing the relationship between the output light intensity and the relative angle between the polarization planes of the polarizer and the analyzer, and (b) is a diagram showing the relationship between the energizing current and the output light intensity.

FIG. 3 is a principle diagram showing a Faraday effect.

FIG. 4 is a diagram showing a configuration example of a general optical magnetic field measuring device.

FIG. 5 is a diagram showing a relationship between a relative angle of polarization planes of a polarizer and an analyzer and output light intensity.

[Explanation of symbols]

100 ... Light source, 200 ... Optical magnetic field sensor, 210 ... Polarizer, 220 ... Magneto-optical effect element (Faraday element), 23
0 ... Analyzer, 300 ... Light receiving element, 400 ... Conducting conductor.

Claims (6)

[Claims] 1. An overcurrent detecting method for detecting a change in Faraday rotation angle due to an overcurrent as a change in optical output by using a magneto-optical effect element, which comprises a polarization plane after passing through a polarizer and a magneto-optical effect element. The polarizer and the analyzer are arranged in such a positional relationship that the relative angle between the polarization plane of the analyzer and the plane of polarization of the analyzer is 90 degrees, and the magnitude of the magnetic field generated by the current flowing under the normal load condition is An overcurrent detection method, wherein a detection signal based on an output is set to zero, and a detection signal based on an optical output is obtained in a large magnetic field generated by an overcurrent. 2. An overcurrent detecting method for detecting a change in Faraday rotation angle due to an overcurrent as a change in optical output by using a magneto-optical effect element having no natural optical rotatory power, which comprises a polarizer and an analyzer. The polarizer and the analyzer are arranged in a positional relationship such that the relative angle of the plane of polarization of 90 ° is 90 °, and the magnitude of the magnetic field generated by the current flowing under the normal load condition is detected based on the optical output. An overcurrent detecting method characterized in that a signal is made to be zero, and a detection signal based on an optical output is obtained in a large magnetic field generated by an overcurrent flowing. 3. An overcurrent detection device for detecting a change in Faraday rotation angle due to an overcurrent as a change in light output by using a magneto-optical effect element, wherein the light emission source emits light, and the light emission source emits light. A linearly polarized light of the polarized light, a magneto-optical effect element that linearly polarizes the light linearly polarized by the polarizer according to the strength of the magnetic field, and a light that is Faraday-rotated by the magneto-optical effect element. An analyzer that converts the light intensity according to the rotation angle, and a light receiving element that emits an output signal when the light intensity from the analyzer exceeds a predetermined value, and the light after passing through the polarizer and the magneto-optical effect element. An overcurrent detection device, which is arranged in a positional relationship such that a relative angle between a plane of polarization and a plane of polarization of an analyzer is 90 degrees. 4. An overcurrent detection device for detecting a change in Faraday rotation angle due to an overcurrent as a change in optical output by using a magneto-optical effect element having no natural optical rotatory power, the light emitting source emitting light. A polarizer that linearly polarizes the light emitted by the light emitting source, and a magneto-optical effect element that does not have a spontaneous optical rotation that Faraday rotates the light linearly polarized by the polarizer according to the strength of the magnetic field, An analyzer that converts the light Faraday-rotated by the magneto-optical effect element having no natural optical rotatory power into a light intensity corresponding to the Faraday rotation angle, and an output signal when the light intensity from the analyzer becomes a predetermined value or more. And a light receiving element that emits light, and the polarizer and the analyzer are arranged in a positional relationship such that a relative angle of a polarization plane of the polarizer and the analyzer is 90 degrees. Overcurrent detection device. 5. The light receiving element selected from a photodiode, a phototransistor, and a light ignition type thyristor.
5. The overcurrent detecting device according to claim 3, wherein the overcurrent detecting device is used. 6. The magneto-optical effect element not having the natural optical rotatory power is lead glass, As4Se, ZnSe, YIG, T.
b-YIG, Bi-YIG, FR-5 glass and Cd
The overcurrent detection device according to claim 4, wherein one selected from MnTe is used.