KR20060017690A - Optical current sensor - Google Patents

Abstract

The present invention is designed to improve the shortcomings of the conventional Faraday rotor type optical current sensor for measuring the electric current of the wire in an optical manner, and the distance from the electric wire in the sensor head part having two Faraday rotors of the same characteristics By placing them at different positions, the difference between the outputs from the two Faraday rotors is the final output to improve the accuracy of current measurement by eliminating the influence of external environment such as temperature, vibration and disturbance magnetic field.

Photocurrent Sensor, Faraday Rotor, Disturbance Field, Temperature Characteristics, Vibration, Garnet, Magnetic Field, Optical Fiber, Differential Amplification

Description

Optical Current Sensor

1 is a system configuration diagram of an optical current sensor according to Embodiment 1 of the present invention;

2 is a system configuration diagram of an optical current sensor according to Embodiment 2 of the present invention.

3 is a system configuration diagram of an optical current sensor according to Embodiment 3 of the present invention.

4 is a system configuration diagram of a conventional optical current sensor according to Comparative Example 1

※ Explanation of symbols for main parts of drawing

10: photocurrent sensor according to the first embodiment of the present invention

11 signal processing circuit 12 light source

13a, 13b, 13c: optical fiber for light beam transmission 14: sensor head part case

15a, 15b, 15c: Cell width lens

16a, 16b, 16c: PBS 17: electric wire

18a, 18b: Faraday Rotator

19a, 19b, 19c, 19d, 19e: 90 degree refractive prism 20a, 20b: photo detector

21a, 21b, 21c: jig for cell width lens and optical fiber fixing

30: photocurrent sensor according to the second embodiment of the present invention

40: photocurrent sensor according to the third embodiment of the present invention

50: conventional photocurrent sensor according to Comparative Example 1

The present invention relates to an optical current sensor for measuring the electric current of the wire by an optical method. More specifically, the present invention relates to an optical current sensor that measures current by converting a magnetic field due to electric current of a wire into a light intensity using a Faraday rotor.

In recent years, with the rapid growth of the industry, the demand for electric power has increased rapidly, requiring high voltage and high capacity of electric power facilities, and stable supply and efficient use of electric power. In particular, there is a limit to applying the existing electronic sensor technology to achieve the advancement of measurement, control, and protection technology from power generation system, which is a power production facility, to distribution system or consumer. The reason is that under high voltage and high power environment, various impulsive voltages, currents and thunder surges caused by natural meteorological phenomena affect the measurement and control devices of various substations by direct path or indirect electrostatic induction or electromagnetic induction. Because it gives. As a technology capable of solving such a problem, the optical sensor technology has recently been in the spotlight. Optical sensor technology has been evaluated as a technology suitable for power equipment such as light characteristics, that is, broadband, low loss, explosion proof, high insulation, non-inductive, meticulous, light weight, ease of repair and matching with optical application technology. .

The optical current sensor is divided into the magnetostrictive coated fiber optic method and the Faraday rotor method according to the method of detecting the magnetic field of the electric wire through which the electric current flows.In the Faraday rotor method, the optical fiber itself is used as the Faraday rotor and the garnet or Lead glass is used as a Faraday rotor. The magnetostrictive coating coating method is a method of detecting and measuring the phase change of an optical signal propagating through the magnetostrictive coating coating optical fiber in magnetic field. It has the advantage of having a high degree, but it is weak to external stress and has a structure of signal processing circuit. It is complicated and expensive. There are two types of optical fiber Faraday rotor type, phase detection type and light intensity detection type, and they have excellent characteristics against precision and influence of external environment, but all have clamp structure, so installation is not easy and system configuration is complicated And, there is a disadvantage that a sophisticated signal processing process is required. The method of using garnet or lead glass, etc., related to the present invention as a Faraday rotor has the advantages of simple structure, small size, light weight, and simple installation and signal processing, but relatively influenced by external environment such as temperature, vibration, disturbance magnetic field, etc. It has the disadvantage of receiving a lot.

Accordingly, the present invention is designed to improve the shortcomings of the optical sensor using a garnet or lead glass as a Faraday rotor, and by placing two Faraday rotors having the same characteristics in one sensor head, temperature, vibration In addition, it provides an optical current sensor that is not affected by the disturbance magnetic field.

In general, a Faraday rotor type photocurrent sensor uses a Faraday rotor to rotate the polarization plane of the light beam passing therein in proportion to the intensity of the magnetic field caused by the electric current of the wire, and the degree of rotation of the polarization plane Measure the current in the wire by converting it into a change in light intensity using a analyzer.

If the current I flows in a straight line, the magnetic field B generated around the lead is given by the ampere law as follows.

----------------------------------------(1)

----------------------------------------(One)

--------------------------------------(2)

--------------------------------------(2)

---------------------------------- (3 )Therefore, the magnetic field at the distance r from the conductor can be expressed by the following equation.

---------------------------------- (3)

meter)/amp 이며 진공중의 투자율 이다. 따라서, 상기 광 전류센서로부터의 출력전압 V는 다음식과 같이 나타낼 수 있다.Where π is the circumference and μ ₀ = 4πＸ10 ^-7 (Tesla

meter) / amp and permeability in vacuum. Therefore, the output voltage V from the photocurrent sensor can be expressed as follows.

--------------------------------------(4)

--------------------------------------(4)

는 비례상수이다. 이때, 만일, 온도, 진동, 외란자계등의 외부환경의 변화에 의한 영향을 고려 한다면 출력 전압 V는 다음식으로 표현할 수 있다.
here

Is a proportionality constant. At this time, if considering the effects of changes in the external environment, such as temperature, vibration, disturbance magnetic field, the output voltage V can be expressed by the following equation.

------------------------(5)

------------------------ (5)

,

,

,

는 각각 외부온도, 진동, 외란자계, 기타 외부환경의 변화에 의한 출력전압의 변동을 나타낸다. here,

,

,

,

Are the fluctuations in output voltage due to changes in external temperature, vibration, disturbance magnetic field, and other external environment.

,과

는 (5)식을 이용하여, 다음식으로 주어진다.Now, in order to offset the fluctuation of the output voltage against such a change in the external environment, two Faraday rotors having the same characteristics are installed in one sensor head part, one of which is a Faraday rotor 1 relatively close to the wire. If installed at a distance, for example r ₁ , and the other Faraday rotor 2 is relatively far from the wire, for example r ₂ , the output voltages from Faraday rotors 1 and 2

,and

Is given by the following equation.

-------------------------(6)

------------------------- (6)

-------------------------(7)

------------------------- (7)

〈

인 것을 고려하면, (6)식의 우변 제1항은 (7)식의 우변 제1항 보다 크다는 것, 즉 페러데이 회전자1에 페러데이 회전자2에 비해 보다 큰 자계가 걸리는 것을 알 수 있다. 그러나, 온도, 진동, 외란자계, 기타외부환경에 의한 영향은 페러데이 회전자1 과 2가 설치된 센서헤드부 전체에 미치는 것이므로, 페러데이 회전자1과 2에 동일하게 작용하여, (6), (7)식에 나타낸 것과 같이, (6), (7)식의 우변 제2항, 제3항, 제4항, 제5항은 동일하게 주어진다. In the formula (6), (7)

〈

In consideration of the fact that the right side paragraph 1 of Eq. (6) is larger than the right side claim 1 of Eq. (7), that is, the Faraday rotor 1 has a larger magnetic field than that of the Faraday rotor 2. However, since the effects of temperature, vibration, disturbance magnetic field, and other external environment are on the entire sensor head part where the Faraday rotors 1 and 2 are installed, they act in the same way on the Faraday rotors 1 and 2, (6), (7 As shown in the equation, the right side items 2, 3, 4, and 5 of (6) and (7) are given the same.

과

의 차

를 구하면
Thus, the output voltage from Faraday rotors 1 and 2

and

Car

If you find

-----------------------------------(8)

-----------------------------------(8)

The influence of temperature, vibration, disturbance magnetic field, and other external environment is canceled, and the output value due to the difference of the magnetic field applied to the Faraday rotors 1 and 2 is obtained. Since it is proportional to the current I flowing, the electric current I of a wire can be measured with high precision, without the influence of an external environment change.

Optical current sensor according to the present invention, the light source; An input optical fiber for transmitting the light beam emitted from the light source, and a parallel optical lens for making the light beam emitted from the input optical fiber into a parallel light beam; A polarizing beam splitter (PBS) for dividing the parallel light beam into two polarizing beams; A Faraday rotor 1 installed at a relatively close distance from an electric wire and transmitting one of the polarization beams divided by the PBS, and rotating the polarization plane of the polarization beam in proportion to the magnetic field generated by the electric current of the electric wire; A Faraday rotor 2 installed at a relatively long distance from the wire and transmitting another one of the polarization beams divided by the PBS, and rotating the polarization plane of the polarization beam in proportion to the magnetic field generated by the electric current of the wire; ; An analyzer 1 for converting the degree of rotation of the polarization plane of the polarization beam passing through the Faraday rotor 1 into light intensity; An analyzer 2 for converting the degree of rotation of the polarization plane of the polarizing beam transmitted through the Faraday rotor 2 into light intensity; A focusing lens 1 for focusing the light beam transmitted through the analyzer 1; A focusing lens 2 for focusing the light beam transmitted through the analyzer 2; An output side optical fiber 1 for transmitting the light beam transmitted through the focusing lens 1; An output side optical fiber 2 for transmitting the light beam transmitted through the focusing lens 2; A photodetector 1 for converting a light beam transmitted through the output optical fiber 1 into an electrical signal; A photodetector 2 for converting the light beam transmitted through the output optical fiber 2 into an electrical signal; And a signal processing circuit which differentially amplifies the electric signals obtained by the photodetector 1 and the photodetector 2 to obtain a voltage output.

A laser diode or a light emitting diode (LED) may be used as the light source, and a small lens such as a cell width lens and a green lens may be used as the parallel light lens and the focusing lens, and the Faraday rotator may be a garnet, glass, or ZnSe. , Bi ₁₂ SiO ₂₀ , Bi ₁₂ GeO _20, etc. may be used, and PBS or polarizer may be used as an analyzer, glass or plastic optical fiber may be used as an optical fiber, and a photodiode may be used as a photodetector. .

Hereinafter, a preferred embodiment of the photocurrent sensor according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a system configuration diagram of an optical current sensor 10 according to Embodiment 1 of the present invention, its configuration and operation principle are as follows.

The light beam starting from the light source 12 connected to the signal processing circuit 11 is transmitted by the input side optical fiber 13a to the sensor head portion 14, as shown by the arrow in Fig. 1, and the input side cell width lens 15a. This results in a parallel light beam. The parallel light beam is separated into two polarized beams by the input side PBS 16a, and the polarized beams refracted by 90 degrees by the input side PBS 16a, one of which is installed Faraday rotor 1 relatively far from the electric wire 17. The polarizing plane of the polarizing beam is rotated in proportion to the relatively weak magnetic field generated by the electric current of the electric wire 17 and is transmitted to the Faraday rotor 1 (18a), and then the output side PBS1 (16b). The degree to which the polarization plane is rotated is converted into the light intensity. At this time, the output side PBS (16b) is installed to rotate 45 degrees with respect to the input side PBS (16a) so that when the degree of rotation of the polarization plane of the polarization beam is converted to the light intensity, the change in the light intensity is made in a linear portion Apply optical bias. The light beam passing through the output side PBS1 16b is refracted by the 90 degree refracting prism 19a, focused by the output side cell width lens 1 15b, and reaches the photodetector 1 20a via the output side optical fiber 13b. Is converted into an electrical signal. On the other hand, the other one of the polarization beams divided by the input side PBS 16a is refracted by the 90 degree refraction prism 2 19b, and then the Faraday rotor 2 18b provided at a relatively close distance from the wire 17 is mounted. While transmitting, after the polarization plane of the polarization beam is rotated in proportion to the relatively strong magnetic field generated by the electric current of the electric wire 17, the degree of rotation of the polarization plane by the output side PBS2 16c is converted into light intensity. . At this time, the output side PBS2 (16c) is also installed to rotate 45 degrees with respect to the input side PBS (16a), when the degree of rotation of the polarization plane of the polarization beam is converted to the light intensity, the change in the light intensity is linear The optical bias is applied to the part. The light beam that has passed through the output side PBS2 16c is refracted by the 90 degree refraction prism 3 (19c), focused by the output side cell width lens 2 (15c), and passed through the output side optical fiber 2 (13c) to the photodetector 2 (20b). ) Is converted into an electrical signal. The signal processing circuit 11 then amplifies the difference between the electrical signals obtained by the photodetector 1 20a and the photodetector 2 20b to obtain a voltage signal proportional to the current of the wire 17.

In this way, the output voltage of the Faraday rotor 2 (18b) located at a relatively close distance from the wire has a value greater than the output voltage of the Faraday rotor 1 (18a) located at a relatively long distance, but the two output signals Since the same output signal is distorted in the external environment such as temperature change, vibration, disturbance magnetic field, etc., when the difference value between the two output signals is the final output, the change components of the output due to the external environment cancel each other, The magnetic field generated, i.e., the current, can be detected with high accuracy.

2 is a block diagram of an optical current sensor according to Embodiment 2 (30) of the present invention. Compared with Embodiment 1 (10) of the present invention, the optical current processor according to Embodiment 2 (30) of the present invention reduces the number of optical components by changing the position of the input / output optical fiber. Same as 10).

3 is a block diagram of a photocurrent sensor according to Embodiment 3 (40) of the present invention. Compared with Embodiment 1 (10) of the present invention, the optical current processor according to Embodiment 3 (40) of the present invention simplified the configuration of the optical system by changing the position of the input / output optical fiber, and the operation principle was Embodiment 1 Same as (10).

4 is a configuration diagram of an optical current sensor according to Comparative Example 1 (50). Comparative Example 1 (50) is a conventional method of the Faraday rotor-type photocurrent sensor, consisting of one Faraday rotor (18a), the light beam starting from the light source 12 through the input side optical fiber 13a is a cell width lens It becomes a parallel beam at 15a, and passes through the input side PBS 16a, the Faraday rotor 18a, and the output side PBS 16b in order to obtain the intensity of light intensity according to the intensity of the magnetic field applied to the Faraday rotor 18a. It is converted, and is then transmitted to the signal processing circuit through the output side optical fiber 13b through the 90 degree refraction prism 19a and the output side cell width lens 15b, and then is output as a voltage value after signal processing. In this case, changes in the external environment such as ambient temperature, vibration, disturbance magnetic field affect the Faraday rotor or optical system, and the measured value is distorted to increase the measurement error.

As described above, according to the optical current sensor according to the present invention, two Faraday rotors are installed in one sensor head part at different positions from the electric wires, and thus the difference between the signals obtained by the two Faraday rotors can be determined. As a final output, by canceling the influence of external environmental factors, such as temperature, vibration, disturbance magnetic field, there is an effect that can measure the current of the wire with high accuracy.

Claims (2)

A light source; An input optical fiber for transmitting the light beam emitted from the light source, and a parallel optical lens for making the light beam emitted from the input optical fiber into a parallel light beam; PBS for dividing this parallel light beam into two polarizing beams; A Faraday rotor 1 installed at a relatively close distance from an electric wire and transmitting one of the polarization beams divided by the PBS, and rotating the polarization plane of the polarization beam in proportion to the magnetic field generated by the electric current of the electric wire; A Faraday rotor 2 installed at a relatively long distance from the wire and transmitting another one of the polarization beams divided by the PBS, and rotating the polarization plane of the polarization beam in proportion to the magnetic field generated by the electric current of the wire; ; An analyzer 1 for converting the degree of rotation of the polarization plane of the polarization beam passing through the Faraday rotor 1 into light intensity; An analyzer 2 for converting the degree of rotation of the polarization plane of the polarizing beam transmitted through the Faraday rotor 2 into light intensity; A focusing lens 1 for focusing the light beam transmitted through the analyzer 1; A focusing lens 2 for focusing the light beam transmitted through the analyzer 2; An output side optical fiber 1 for transmitting the light beam transmitted through the focusing lens 1; An output side optical fiber 2 for transmitting the light beam transmitted through the focusing lens 2; A photodetector 1 for converting a light beam transmitted through the output optical fiber 1 into an electrical signal; A photodetector 2 for converting the light beam transmitted through the output optical fiber 2 into an electrical signal; A photocurrent sensor comprising a signal processing circuit for differentially amplifying an electrical signal obtained by the photodetector 1 and the photodetector 2 to obtain a voltage output. The optical current sensor of claim 1, wherein the Faraday rotor 1 and the Faraday rotor 2 are a Faraday rotor selected from the group consisting of garnet, glass, ZnSe, Bi ₁₂ SiO ₂₀ , and Bi ₁₂ GeO ₂₀ .

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