JPS63266323A - Magneto-optical measuring instrument - Google Patents

Abstract

PURPOSE:To exactly measure the temp. at a current measurement point by using a Faraday element of which the optically rotatory power is changed by a temp. change as an optical sensor. CONSTITUTION:The light emitted from a light transmitter 1 having a light source consisting of a laser diode or light emitting diode passes an optical fiber 2, then a polarizer 3, the Faraday element 4 and an analyzer 5 and arrives at a light receiver 7 having a light receiving element such as photodiode or phototransistor by passing an optical fiber 6. A magnetic field and temp. are simultaneously measurable by separating the DC component and AC component of the output of the receiver 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical measuring device capable of simultaneously measuring current or magnetic field and temperature of a conductor.

[Conventional technology]

Measuring the temperature rise of electric motors driven by high voltage, the high-voltage side winding of transformers, or the contact parts of pole-mounted switch contacts of power distribution lines is a test of the reliability of these devices.

This is essential for diagnosing whether reliability and operation are normal or abnormal.

Conventionally, an indirect method has been adopted in which the current value of these devices is measured and the temperature rise is measured based on the fluctuation of the current value.

[Problem that the invention seeks to solve]

However, as in the case of a switch contact, there is not necessarily a correlation between the current value and the temperature rise. Therefore, in order to diagnose whether the device is operating normally, it is necessary to directly measure not only the current but also the temperature. but,
Temperature measurement of high-voltage, large-current circuits, particularly the temperature inside the windings, has the problem that accurate values cannot be easily measured using conventional thermocouples or the like due to insulation and noise issues.

The present invention not only measures the current or magnetic field, but also accurately measures the temperature at the current measurement point simultaneously without being influenced by insulation or electromagnetic induction, and requires special equipment and measuring equipment for temperature measurement. It is an object of the present invention to provide a device that can easily measure current or magnetic field and temperature simultaneously without installing a device.

[Means for solving problems]

To achieve this object, the present invention provides an optical system that includes a light source, a light sensor, and a light receiver, and transmits a light signal from the light source using an optical fiber as a transmission path. A polarizer, a Faraday element, and an analyzer are arranged in order along the direction, and the Faraday element is made of a material whose optical rotation changes with temperature changes, and the element length of the Faraday element is determined by its optical rotation. The angle is (π/4)±nπ(n=0.1.2.・
. The magnetic field is characterized by a configuration in which the direct current component is detected as a temperature component, and the amplitude of the alternating current component is detected as an amount proportional to the magnetic field.

[Effect]

The magneto-optical measuring device of the present invention has a current/magnetic field detection section configured with an optical sensor, and converts the detected current or magnetic field and temperature information into an optical signal, in order to ensure voltage resistance of a high voltage circuit. This is a high-voltage circuit measurement device that converts the signals, transmits these two signals to the low-voltage part through the same optical fiber, and separates the two pieces of information after converting them into electrical signals.

FIG. 1 is a schematic diagram showing the basic principle of the present invention. Light emitted from an optical transmitter 1 having a light source consisting of a laser diode or a light emitting diode passes through an optical fiber 2,
Polarizer 3. After passing through Faraday element 4 and analyzer 5,
The light passes through an optical fiber 6 and reaches an optical receiver 7 having a light receiving element such as a photodiode or a phototransistor. The optical power input to the optical receiver 7 at this time is: P = Po (L + cos2θ)
......(1). However, polarizer 3. The analyzer 5 is assumed to be a parallel Nicol analyzer. Here, θ is the rotation angle when the plane of polarization passes through the Faraday element 4.

This rotation angle θ is equal to the optical rotation angle θ1. If the Faraday rotation angle due to the external magnetic field is θ, then θ=θ, +θ, ・・・・・・・・・・・・・・・
...(2). Here, the optical rotation angle θ1 near room temperature
to θ, = (π/4)±nπ+ to θ7...
...Adjust the Faraday element length so that it becomes (3). However, koT is a change in the angle of optical rotation due to temperature (θT), and k is a constant determined by the Faraday element. For example, k is negative in B G O (Bi, 2Ge 020) crystal. FIG. 5 shows an example of a temperature change in the optical rotation angle of a BGO crystal. In this case, the left-handed optical rotation angle was expressed as positive.

On the other hand, the Faraday rotation angle θ is as follows: θ, = V, HL ・・・・・・・・・・・・
...(4). However, vr is the Verdet constant, H
is the magnetic field in the core gap, and L is the Faraday element length.

Substituting equations (3) and (4) into equation (2), and then substituting these into equation (1), we get π P = Pa (1+cos(=±20π+2, θ,
+2V, HL) )= Pa (1+5in(2 to θ,
+2V, HL) ). Here, 2 to 0 + 2V
, if HL is small, P # po(1+2 plus θt+2
Vr)IL) *t+e+++t++(5). In this equation (5), the second term is a component due to temperature, and the third term is a variation component due to magnetic field.

Now, if the magnetic field component is AC, the temperature component and the magnetic field component can be separated and H = H, sinωt, so equation (5) is as follows: P =, Pa (1+2 to θy+2VrHoLsinωt
) ...-(6).

Therefore, by converting the signal into an electrical signal in the photodetector and separating the DC component and the AC component, the magnetic field and temperature can be measured simultaneously. Figure 2 shows the situation. Since the magnetic field is proportional to the current, the magnetic field can be converted into a current. As shown in FIG. 1, the DC component is displayed on a temperature display 8, and the AC component is displayed on a current display 9.

〔Example〕

The configuration shown in FIG. 1 is the basic configuration of the present invention, and in reality, it is necessary to calibrate the measured value each time due to fluctuations in optical power and fluctuations in optical circuit, for example, connection loss. To take this measure, the optical system is connected as shown in FIG. In this optical system, the pulse generated by the optical transmitter 1 returns to the optical receiver 7 side by the directional coupler 10.11, and the optical pulse is returned (Japanese Patent Laid-Open No. 61
=Refer to Publication No. 228626).

When this optical pulse is received by the optical receiver 7, the reflected pulse P+ on the end face of the optical sensor 20 consisting of the polarizer 3', the Faraday element 4, and the analyzer 5, that is, the side where the delay line 12 is not included, passes through the sensor 20. Three optical pulses are observed: the transmitted pulse FT which is returned by the sensor, and the pulse P2 which is reflected by the sensor end face on the delay line side. In this case, P
o ” Since there is a relationship of P r or P2, (6)
From the formula, -Oc (θt+2VrHoLsinωt on 1+2)
(7) is obtained, and the influence of Po, that is, the influence of fluctuations in the optical fiber and the light emission power is eliminated.

FIG. 4 shows this. That is, FIG. 4(a) shows the relationship of the optical signal to the temperature change of the optical sensor, and υ in the figure shows the reflected pulse and the transmitted pulse P. , P
The output waveforms of I and P2 are shown.

In addition to the above-mentioned BGO crystal whose optical rotation changes with temperature, the Faraday element used in the present invention includes BSO
(Bi, Si 02°) crystal, etc. can be used.

〔Effect of the invention〕

As explained above, in the present invention, a Faraday element whose optical rotation changes with temperature change is used as an optical sensor, and the Faraday element length is adjusted to the above-mentioned value. Thereby, optical power is separated into a DC component and an AC component, and temperature changes and magnetic fields are detected. Therefore, it is possible to provide a current and temperature measuring device that can not only measure the current of a high voltage circuit but also measure temperature information using the same optical fiber without using additional equipment.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle of the present invention, Fig. 2 is an operating waveform diagram, Fig. 3 is a block diagram of an embodiment of the invention, Fig. 4 is an operating waveform diagram of this embodiment, and Fig. 5 is an operating waveform diagram. It is a graph which shows an example of the temperature change of the optical rotation angle of a BGO crystal. 1: Optical transmitter 2: Optical fiber 3: Polarizer
4: Faraday element 5: Analyzer 6
: Optical fiber 7: Optical receiver 8.9: Temperature display 10, 11: Directional coupler 12: Delay line 20: Optical sensor Patent applicant Anyo Electric Manufacturing Co., Ltd. Agent
Person Masu Kobori (and 2 others) Figure 5 Temperature θT ('C) Figure 1 Whistle 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In an optical system that includes a light source, a light sensor, and a light receiver, and transmits an optical signal from the light source using an optical fiber as a transmission path, the light sensor includes a polarizer, a Faraday An array of elements and analyzers is used, and a material whose optical rotation changes with temperature changes is used as the Faraday element.
n = 0, 1, 2, ...), and the optical power component of the optical signal received from the optical sensor installed in the alternating current magnetic field that is the object to be measured is 1. A magneto-optical measurement device characterized by having a configuration in which an optical receiver separates a DC component and an AC component, and detects the DC component as a temperature component and the amplitude of the AC component as an amount proportional to a magnetic field.