JP3201729B2 - How to use the optical sensor system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using an optical sensor system for measuring a physical quantity such as a current or a voltage of a transmission line or a distribution line.

[0002]

2. Description of the Related Art There is a device using an optical sensor as a device for measuring electric current or voltage of an electric wire. When measuring current, an optical sensor is provided in the magnetic field, and when measuring voltage, an optical sensor is provided in the electric field. Then, light is output from the light emitting element, and unmodulated light is sent to the optical sensor via the optical fiber. The optical sensor is modulated in a magnetic field or an electric field, and provides the modulated light to a light receiving element via an optical fiber. The light receiving element converts the incident modulated light into an electric signal. By observing the light modulation rate, it is possible to measure the value of a current or a voltage, which is a physical quantity to be measured.

FIG. 5 shows the relationship between some measured physical quantities (magnetic field and electric field) and the detection principle of an optical sensor. Optical phenomena of the optical sensor include the Faraday effect, Pockels effect, interference phenomenon, and the like.
Some use phase. Since light is used for the measurement system, a measurement device based on such a principle is employed in a field where high insulation properties, explosion proof properties, and electromagnetic noise resistance are required.

FIG. 6 shows a principle diagram of a voltage sensor using such an optical sensor. The voltage sensor 60 basically includes a polarizer 61, a quarter-wave plate 62, an electro-optical element 63, and an analyzer 64. Light from a light emitting element (not shown) is converted by the polarizer 61 into linearly polarized light. This light passes through the quarter-wave plate 62 and is converted into circularly polarized light. When a voltage for measurement is not applied to the electro-optical element 63 which is an optical sensor, the light of this circularly polarized light passes through the electro-optical element 63, and then the light quantity is reduced by ６４ by the analyzer 64.
Is output.

When a voltage for measurement is applied to the electro-optical element 63, the refractive index of the electro-optical element 63 changes. Since the electro-optical element 63 has birefringence, the polarization state of the light transmitted through the electro-optical element 63 depends on the magnitude of the applied voltage, as P _{0 to} P ₋ and P _{0 to} P ₊ in FIG. To change. That is, the state changes from circularly polarized light to elliptically polarized light to linearly polarized light to elliptically polarized light to circularly polarized light.

FIG. 7A shows an actual structure of a voltage sensor 70 as an example of an optical sensor for detecting an electric field intensity.
As shown in FIG. 7B, light of a constant intensity from the optical fiber 71 is converted into parallel light by the lens 72, and is converted into a polarizer (PBS).
73, quarter-wave plate 74, electro-optical element (LiNbO3) 75
Is input to And the light modulated by the electric field
The light enters the lens 77 via the analyzer (PBS) 76, and the modulated light as shown in FIG.

An apparatus that includes the above-described optical sensor, outputs light, performs signal processing of modulated light, and measures a physical quantity is hereinafter referred to as an optical sensor system, and the configuration thereof will be specifically described. As shown in FIG. 8, for example, a conventional optical sensor system 81 includes an E / O circuit 83 having a light source, and a light for intensity-modulating light incident from the E / O circuit 83 according to a measured physical quantity V such as current or voltage. The sensor 82 includes an O / E circuit 84 that converts incident light from the optical sensor 82 into an electric signal, and an arithmetic circuit 85 that calculates a modulation degree of the optical sensor 82 using an output signal of the O / E circuit 84. . Then, a spectrum analyzer 87 is connected to the output terminal of the O / E circuit 84 as needed.

The conventional method of adjusting and using the optical sensor system is such that, when a physical quantity V is applied to the optical sensor 82 to improve the measurement accuracy of a minute physical quantity, the E / O circuit 83 and the O / O circuit 83 / E circuit 84 minimizes noise, that is, the ratio of signal S to noise N (SN
R) was to be as large as possible.

FIG. 9 shows an operation procedure showing a conventional adjustment and use method when measuring the physical quantity V using the optical sensor system 81 described above. First, in the first step S21, the measured physical quantity V = v is applied to the optical sensor 82. Then, the arithmetic circuit 85 calculates the degree of modulation of the optical sensor 82 from the output signal of the O / E circuit 84, converts it into a value v of the measured physical quantity V, and outputs it.

When the measurement accuracy is adjusted, the process proceeds to step S22, where the output signal of the O / E circuit 4 is input to the spectrum analyzer 87. In step S23, the spectrum analyzer 87 outputs the alternating current (AC) component Vac of the input signal.
And a direct current (DC) component Vdc. When the process proceeds to step S24, Vac / Vac /
The Vdc value is obtained as the S / N value. And the obtained S / N
The value is compared with a target S / N value SNR.

In step S24, if the S / N value is SN
If it is smaller than R, the process proceeds to step S25. In step S24, if the S / N value is equal to or higher than the SNR, it is determined that adjustment is unnecessary. When the process proceeds to step S25, the light amount of the E / O circuit 83 and the noise generation amount of the O / E circuit 84 are adjusted while checking the S / N value obtained by the spectrum analyzer 87. Then, returning to step S21,
The same processing is performed. If the S / N value becomes equal to or more than the SNR in step S24, the adjustment of the optical sensor system 81 is completed, and the measurement of the physical quantity V is started.

With the measured physical quantity V = v applied, the signal S including the noise N is input to the spectrum analyzer 87, and the spectrum is analyzed. Then, it is necessary to separate the noise component and the signal component and calculate the S / N value.

[0013]

However, as in the prior art, the SNR
In order to improve the measurement accuracy of a minute physical quantity by using the index as an index, an expensive device such as a spectrum analyzer 87 for separating the signal S and the noise N is required. In addition, since the relationship between the magnitude of the measured physical quantity and the SNR that is an index of the required measurement accuracy is unknown, the SNR may be increased more than necessary, causing a cost increase of the optical sensor system. Conversely, if the SNR is insufficient for the required accuracy, the measurement accuracy of the optical sensor system varies. In addition, in order to attach an optical sensor system to each phase of a three-phase distribution line and measure the current and voltage of each phase to obtain a zero phase, it is necessary to use a plurality of optical sensor systems.
In such a case, there is a problem that a large measurement error is caused.

The present invention has been made in view of such a conventional problem, and realizes a method of using an optical sensor system capable of measuring a physical quantity while securing necessary and sufficient measurement accuracy by a simple method. The purpose is to:

[0015]

In order to solve such a problem, the invention according to claim 1 of the present application is directed to a light for modulating the intensity of incident light according to the physical quantity V when the physical quantity V is applied from the outside. A sensor, an E / O circuit for outputting light for measurement to the optical sensor, and receiving modulated light from the optical sensor;
A modulation degree M of the optical sensor is calculated from an O / E circuit for converting to an electric signal and a modulation component Vac and a DC component Vdc output from the O / E circuit, and the modulation degree M is converted into a value of a physical quantity V. And an arithmetic circuit for outputting the modulated component Vaco of the output signal of the O / E circuit by the arithmetic circuit in a state where the physical quantity V is not applied to the optical sensor. The component Vdc is extracted, and the ratio between the modulation component Vaco and the DC component Vdc in a state where the physical quantity V is not applied is calculated as a noise light quantity ratio Vaco / Vdc , and the noise light quantity ratio of the optical sensor to the physical quantity V with a desired measurement resolution is set as a target. A noise light amount ratio np is set, and the E / O circuit is controlled so that the value of the noise light amount ratio Vaco / Vdc becomes equal to or less than the target noise light amount ratio np .
Adjust the light output noise generation amount of the O / E circuit, after the characteristics adjustment of the said E / O circuit O / E circuit, of the photosensor obtained by applying the physical quantity V to the light sensor By the value of the modulation degree M = Vac / Vdc , the physical quantity V
Is calculated and output .

Further, the invention described in claim 2 of the present application is characterized in that the E
The / O circuit adjusts the characteristics by adjusting the intensity of the optical output, and the O / E circuit adjusts the characteristics by reducing the amount of noise generation to a predetermined value or less.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for using an optical sensor system according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram of an optical sensor system 1 used in the present embodiment. The optical sensor system 1 includes an optical sensor 2, an E / O circuit 3, an O / E circuit 4, an arithmetic circuit 5, and an optical fiber 6. This is the same as the conventional example.

The E / O circuit 3 is, for example, a light emitting diode (L
ED) as a light source. The optical fiber 6 includes a light projecting fiber that supplies light from the E / O circuit 3 to the optical sensor 2 and a light receiving fiber that guides light from the optical sensor 2 to the O / E circuit 4. The optical sensor 2 is a sensor that changes the intensity of incident light from the E / O circuit 3 according to the measured physical quantity V. As described with reference to FIG. 5, the optical sensor 2 includes an optical voltage sensor using the Pockels effect, a photocurrent sensor using the Faraday effect, a waveguide-type optical voltage sensor, and the like.

The O / E circuit 4 is a circuit for converting incident light from the optical sensor 2 into an electric signal. The arithmetic circuit 5 is O / E
This circuit calculates the modulation factor M of the optical sensor 2 from the modulation component Vac and the DC component Vdc of the output signal of the circuit 4, converts the modulation factor M into a measured physical quantity V, and outputs it. The degree of modulation M is substantially equal to Vac / Vdc. The measured physical quantity V is, for example,
For example, in the case of an AC voltage, the modulation component Vac does not include a DC component.
Therefore, it is called an AC component Vac.

FIG. 2 is an operation procedure showing a method of using the optical sensor system 1 configured as described above. First, in the first step S11, the measurement physical quantity V is not applied (V =
0) The following processing is performed in the state. That is, the next step S12
Then, the arithmetic circuit 5 calculates the AC component of the output signal of the O / E circuit 4.
Vaco and DC component Vdc are extracted. Then, the value of Vaco / Vdc when V = 0 is obtained as a noise light amount ratio.

Here, Vdc indicates a light component that is not modulated by the external physical quantity V by the optical sensor 2, and may be considered as a signal component when V = 0. Vaco is O when the measured physical quantity V = 0.
The AC component output from the / E circuit 4 can be considered as a noise component generated in a circuit from the E / O circuit 3 to the O / E circuit 4 via the optical sensor 2.

The noise light amount ratio of the optical sensor with respect to the desired resolution is defined as the target noise light amount ratio np. In step S13, the actually measured noise light amount ratio Vaco / Vdc is compared with the target noise light amount ratio np. Noise light amount ratio Vaco
If the value of / Vdc exceeds the target noise light amount ratio np, the process moves to step S14. In step S14, the light amount of the E / O circuit 3 and the noise generation amount of the O / E circuit 4 are adjusted so that the value of the noise light amount ratio Vaco / Vdc becomes equal to or less than the target noise light amount ratio np. Then, after adjustment, step S1
Returning to 1, the same processing is continued.

In step S13, the noise light amount ratio V
When the value of aco / Vdc becomes equal to or less than the target noise light amount ratio np, the process proceeds to step S15, and the physical quantity V to be measured is applied to the optical sensor 2. Then, the arithmetic circuit 5 calculates the modulation degree M = Vac / Vdc from the output signal of the O / E circuit 4, converts the calculation result into a value of the measured physical quantity V, and outputs the value.

Here, the light amount adjustment of the E / O circuit 3 is L
This is to adjust the drive current of the ED, and the adjustment of the noise generation amount of the O / E circuit 4 includes from the adjustment of the gain to the change of the element and the change of the circuit configuration.

FIG. 3 is a graph showing the relationship between the ideal modulation degree which changes according to the magnitude of the measured physical quantity V, the desired measurement accuracy (ratio error), and the noise light amount ratio ( Vaco / Vdc). In the figure, the magnitude of the physical quantity to be measured corresponds to the ideal modulation factor of the optical sensor 2 of the intensity modulation method described above. The measurement accuracy is proportional to the ratio error, which is a deviation from linearity. For example, in order to measure a physical quantity V having a modulation factor of 0.06% or more within a ratio error of 1.0% as shown in FIG.
^It can be seen that it is better to set it to ^-4 or less.

FIG. 4 is a graph showing the relationship between the ideal modulation degree corresponding to the measured physical quantity V, the noise light amount ratio Vaco / Vdc, and the measured modulation degree corresponding to the actual measurement result of the measured physical quantity V.

The relationship between the ideal modulation degree and the physical quantity V differs between the optical sensors 2 of various intensity modulation systems. For example, in the case of an optical voltage sensor using the Pockels effect, the rated voltage 1
When the modulation degree at the time of 00V is designed to be 1.75%, a predetermined noise light amount ratio for measuring a voltage of 5V or more with an error of 1% or less is 1.23 × 10 ⁻⁴ or less.

As described above, if the relationship between the magnitude of the physical quantity V, the desired measurement accuracy, and the noise light amount ratio is known in advance, it is not necessary to increase the cost more than necessary, and the desired measurement can be performed at the minimum cost. An accurate optical sensor system is obtained.

Similarly, in the case of the photocurrent sensor utilizing the Faraday effect, a predetermined noise light amount ratio can be easily obtained from the relationship between the measured current (magnetic field) and the ideal modulation degree.

In the case of the optical sensor system 1 in which the DC component corresponding to the amount of light received by the O / E circuit 4 is standardized, the noise light amount ratio is O / O when the physical quantity V is not applied.
This corresponds to the ratio of the standard values of the AC component and the DC component of the output signal of the E circuit 4. The measurement modulation degree in this case is defined by the ratio between the standard values of the AC component and the DC component of the output signal of the O / E circuit 4.

In the case of a waveguide type optical voltage sensor or the like, the measured physical quantity V is a voltage or an electric field. In this case, the magnitude of the voltage or the electric field is not measured from the degree of modulation of the sensor, but from the phase difference angle between the two light waves. Since both the modulation degree and the phase difference angle are almost linear to the measured physical quantity V, if the modulation degree in the present embodiment is converted into the phase difference angle and replaced, the noise amount ratio of the desired measurement accuracy can be similarly obtained. it can. In addition, if the parameter has a linear relationship with the physical quantity V, the measured physical quantity V can be easily converted into the modulation factor. Conversely, the modulation degree is changed to the physical quantity V
May be converted into a parameter that changes linearly with respect to the measurement physical quantity V, and the relationship between the parameter that changes linearly with the measured physical quantity V, the noise light amount ratio, and the ratio error may be derived.

[0032]

As described above, according to the present invention, by adjusting the easily measurable parameter called the noise light amount ratio, it is not necessary to increase the cost for reducing noise more than necessary, and it is possible to reduce the cost. The optical sensor system having the above accuracy can be realized. In addition, when the physical quantities to be measured are the voltage and current of the power line, the measurement accuracy can be adjusted without bringing special measuring equipment to the site.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical sensor system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure for adjusting and using the optical sensor system according to the embodiment.

FIG. 3 is a characteristic diagram illustrating a relationship between an ideal modulation factor, a noise light amount ratio, and a ratio error of the optical sensor system according to the present embodiment.

FIG. 4 is a characteristic diagram illustrating a relationship between an ideal modulation factor, a noise light amount ratio, and a measurement modulation factor of the optical sensor system according to the present embodiment.

FIG. 5 is a classification table showing a detection principle of an optical sensor.

FIG. 6 is a configuration diagram of a voltage sensor.

FIG. 7 is a sectional view showing a structure of a main part of the voltage sensor.

FIG. 8 is a configuration diagram of a conventional optical sensor system.

FIG. 9 is a flowchart showing a procedure for adjusting and using a conventional optical sensor system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical sensor system 2 Optical sensor 3 E / O circuit 4 O / E circuit 5 Arithmetic circuit 6 Optical fiber

Claims (2)

(57) [Claims] 1. An optical sensor that modulates intensity of incident light according to a physical quantity V when a physical quantity V is applied from the outside, an E / O circuit that outputs measurement light to the optical sensor, and the optical sensor. An O / E circuit for receiving the modulated light from the O / E circuit and converting the modulated light into an electric signal; a modulation component Vac and a DC component V output from the O / E circuit.
a calculation circuit for calculating the modulation degree M of the optical sensor from dc , converting the modulation degree M into a value of a physical quantity V, and outputting the value. In the state where V is not applied, the modulation circuit Vac of the output signal of the O / E circuit is output by the arithmetic circuit.
o and extracts the DC component Vdc, the ratio of the modulation component Vaco the DC component Vdc of the state of not applying the physical quantity V is calculated as a noise light quantity ratio Vaco / Vdc, noise light quantity of the light sensor for a physical quantity V of a desired measurement resolution The ratio is set as a target noise light quantity ratio np, and the light output of the E / O circuit is set so that the value of the noise light quantity ratio Vaco / Vdc becomes equal to or less than the target noise light quantity ratio np.
And the noise generation amount of the O / E circuit, and after adjusting the characteristics of the E / O circuit and the O / E circuit, the modulation degree of the optical sensor obtained by applying the physical quantity V to the optical sensor. A method of using the optical sensor system, wherein the value of the physical quantity V is calculated and output based on the value of M = Vac / Vdc . 2. The E / O circuit adjusts characteristics by adjusting the intensity of light output, and the O / E circuit adjusts characteristics by reducing the amount of noise generation to a predetermined value or less. The method for using the optical sensor system according to claim 1, wherein: