JP4092142B2 - Photovoltage measuring device, electric power or electric energy measuring device, and electrical equipment protection system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical voltage measuring device, an electric power or electric energy measuring device using the optical voltage measuring device, and an electrical equipment protection system.
[0002]
[Prior art]
2. Description of the Related Art In recent years, optical measuring instruments that optically measure voltage and current are installed in electric stations such as power stations, substations, and switching stations. FIG. 7 is a perspective front view showing a schematic structure of a conventional optical voltage measuring device. This optical voltage measuring device includes a sensor unit, a light emitting unit, a light receiving unit, and a light emitting side and light receiving side signal processing circuit (not shown), and an object to be measured is applied between electrode terminals 34 described later. Applied voltage Vm. The sensor unit includes a polarizer 3, a quarter-wave plate (also referred to as “λ / 4 plate”) 25, an electro-optic crystal 26, and an analyzer 27 arranged on the same optical axis in order from the light incident side. ing. A pair of electrodes 32 is deposited on the electro-optic crystal 26, and each electrode 32 is electrically connected to a pair of electrode terminals 34 by lead wires 33. That is, the applied voltage Vm from the electrode terminal 34 is applied to the electro-optic crystal 26. As the material of the electro-optic crystal 26, Bi12SiO20 (BSO), KDP, LiNbO3 having natural birefringence, LiTaO3, or the like is used.
[0003]
The light emitting unit includes an E / O circuit including a light emitting element such as an LED (Light Emitting Diode) as the light source 1, and an optical fiber 28a, a ferrule 29a, a GRIN lens 30a, and a holder 31a arranged on the same optical axis. And a side optical system. The light receiving unit converts an output-side optical system including the optical fiber 28b, the ferrule 29b, the GRIN lens 30b, and the holder 31b disposed on the same optical axis, and an optical signal emitted from the output-side optical system into an electrical signal. And an O / E circuit including the detector 11.
[0004]
Each optical component in the input side optical system of the light emitting unit and the output side optical system of the light receiving unit has optical axis surfaces in contact with each other bonded by an adhesive. Further, in the sensor unit of the optical voltage measuring device, the optical components that are arranged on the same optical axis, that is, the polarizer 3, the quarter wavelength plate 25, the electro-optic crystal 26, and the analyzer 27 are also in contact with each other. All surfaces are bonded with adhesive. Here, the optical axis surface means a surface perpendicular to the optical axis, and there are two light incident surfaces and light output surfaces for each optical component (the same applies hereinafter).
[0005]
The light emitting side and light receiving side signal processing circuits are connected to the sensor unit by a light emitting unit and a light receiving unit, respectively. At this time, the input side optical axis surface of the polarizer 3 of the sensor unit is the optical axis surface of the GRIN lens 30a of the light emitting unit, and the output side optical axis surface of the analyzer 27 of the sensor unit is the optical axis of the GRIN lens 30b of the light receiving unit. The surfaces are bonded to each other by an adhesive. The sensor unit, the input side optical system in the light emitting unit, and the output side optical system in the light receiving unit are mechanically fixed to a case (not shown). In general, an epoxy or urethane resin is used as an adhesive for each optical component.
[0006]
Next, the operation principle of the optical voltage measurement apparatus having the above configuration will be described. For example, when an LED having a central wavelength of 0.85 μm is used as the light source 1 in the light emitting unit, the non-polarized light of the LED is emitted from the light source 1 and passes through the input side optical system of the light emitting unit and the polarizer 3 of the sensor unit. It becomes linearly polarized light. The linearly polarized light passes through the quarter-wave plate 25 and becomes circularly polarized light, and the circularly polarized light passes through the electro-optic crystal 26 and then becomes elliptic according to the strength of the applied voltage Vm from the electrode terminal 34 to the electro-optic crystal 26. And becomes elliptically polarized light.
[0007]
The elliptically polarized light is received by the detector 11 after passing through the analyzer 27 of the sensor unit and the output side optical system of the light receiving unit. The amount of light output from the analyzer 27 corresponds to the polarization state of the light passing through the electro-optic crystal 26. Since this polarization state changes depending on the voltage Vm applied to the electro-optic crystal 26, the change in the amount of light output from the analyzer 27 is monitored via the optical fiber 28b on the light receiving side, and the optical signal is converted into an electric signal by the detector 11. The voltage Vm applied to the electro-optic crystal 26 can be measured by calculating the degree of modulation of the amount of light when converting to a signal. Here, the modulation degree of the light quantity is a ratio of the AC component and the DC component in the light quantity.
[0008]
By the way, it is rather rare for the above-described photovoltage measuring device to function alone in an electric station, and in combination with the photocurrent measuring device, power, electric energy, or reactive power is measured, impedance is calculated, and distance is calculated. It is generally used to operate a protection system for electrical equipment called a relay. Like the photovoltage measuring device, the photocurrent measuring device is a measuring instrument using light, but its principle and configuration are completely different. Next, a conventional example of a photocurrent measuring device will be described.
[0009]
Several types of photocurrent measuring devices have been proposed, but those equipped with a Sagnac interferometer composed of an optical fiber coil have attracted attention. The Sagnac interferometer is composed of an optical fiber coil, and has been used as a rotation detection of a moving body as an optical fiber gyroscope, but has a characteristic of reacting to a magnetic field generated by an electric current in addition to the rotation detection. Therefore, current measurement can be performed using this characteristic. The operating principle of current measurement with a Sagnac interferometer is as follows. That is, when a magnetic field is applied to an optical fiber coil, which is a transparent material, the polarization plane is rotated by the Faraday effect, and the rotation angle of the polarization plane is proportional to the strength of the magnetic field and the light passage distance. Due to the rotation of the polarization plane, a phase difference is generated between the left-handed light and the right-handed light that circulates around the optical fiber coil. By detecting this phase difference, a magnetic field applied to the optical fiber coil is generated. It becomes possible to measure the original current.
[0010]
Such a Sagnac interference type photocurrent measuring device will be specifically described with reference to FIG. As shown in FIG. 8, a light source 1 is disposed in a Sagnac interferometer-type current measuring device, and a coupler 2 is connected to the light source 1 as a beam separating means for branching light from the light source 1. A Sagnac interferometer composed of an optical fiber coil is connected to the coupler 2 via a polarizer 3 and a polarization-maintaining fiber coupler 4. The Sagnac interferometer is provided with a phase modulator 10 and a sensor fiber 19 surrounding the current path 20, and first and second quarter-wave plates 17 and 18 are disposed on both sides of the sensor fiber 19. ing. The first and second quarter-wave plates 17 and 18 are configured to output circularly polarized light when linearly polarized light is input via a polarizing filter, and output linearly polarized light when circularly polarized light is input. The coupler 2 is connected to a detector 11 that converts an optical signal into an electrical signal. Further, a synchronous detector 35 is connected to the detector 11. The synchronous detector 35 is connected to an oscillating circuit 36 that supplies a reference signal to the synchronous detector 35.
[0011]
In the Sagnac interferometric current measuring device having the above configuration, the light emitted from the light source 1 reaches the polarization plane preserving fiber coupler 4 through the polarizer 3 and circulates in the reverse direction in the Sagnac interferometer. That is, it is sent as left-handed light and right-handed light. Of these, the counterclockwise light is first phase-modulated by the phase modulator 10, and the phase-modulated counterclockwise light passes through the second quarter-wave plate 18 and enters the sensor fiber 19, and goes counterclockwise. Then, the light passes through the first quarter-wave plate 17, the polarization-maintaining fiber coupler 4, the polarizer 3, and the coupler 2 and reaches the detector 11 to be received. On the other hand, the clockwise light passes through the first quarter-wave plate 17 and enters the sensor fiber 19, rotates clockwise and passes through the second quarter-wave plate 18 and then the phase modulator. 10, the phase-modulated clockwise light passes through the polarization-maintaining fiber coupler 4, the polarizer 3, and the coupler 2 and reaches the detector 11 to be received.
[0012]
When a magnetic field is applied to the sensor fiber 19 between the counterclockwise light and the clockwise light after circulating around the sensor fiber 19, a phase difference is generated, and the polarization-maintaining fiber coupler 4 and the polarizer 3 cause a phase difference. As a result of the interference, the phase-modulated light whose light intensity has changed is received by the detector 11. The phase-modulated light reaching the detector 11 is photoelectrically converted into an electrical signal here. The electrical signal photoelectrically converted by the detector 11 is input to the synchronous detector 35. The synchronous detector 35 obtains a detection output having a phase difference proportional to the magnetic field applied to the sensing fiber 19 by using the signal supplied from the oscillation circuit 36 as a reference signal (for details of phase modulation, refer to Japanese Patent Application No. 10-1999). -162419 and Japanese Patent Application No. 11-197244). As described above, in the Sagnac interference type current measuring device, circularly polarized light is incident and propagated from both ends of the current detection coil, causes both lights having a phase difference to interfere with each other, and the applied magnetic field is based on the change in the light intensity. Can be measured.
[0013]
[Problems to be solved by the invention]
By the way, both the photovoltage measuring device and the photocurrent measuring device are often used in a severe outdoor environment, and are required to have excellent temperature characteristics. Specifically, it is desired that the change in relative error is ± 1% or less and the phase change is 1 ° or less at −20 ° C. to 80 ° C. However, in the conventional optical voltage measuring apparatus, there are many factors that cause errors in sensitivity and phase due to temperature changes. For example, there is a change in refractive index due to stress at the bonding portion in a quarter-wave plate or an electro-optic crystal, a change in birefringence in the quarter-wave plate, and a change in thermal drift or offset in the electronic circuit portion. Further, in the case of an electro-optic crystal having natural birefringence such as LiNbO3, the incident light may be misaligned. Therefore, there has been a demand for an optical voltage measuring device that exhibits excellent environmental resistance and operates stably even in harsh environments. Moreover, the behavior differs between the conventional optical voltage measuring device and the current measuring device. For this reason, when calculating | requiring electric power and impedance combining both, the error tends to become large, and it has caused the fall of measurement accuracy.
[0014]
In addition, the voltage measuring device has a problem in the voltage dividing method. That is, since the electro-optic crystal used for voltage measurement is mechanically weak and expensive, it is not performed by applying a high voltage such as 500 kV to the electro-optic crystal as it is. This is applied to the electro-optic crystal after being lowered to a voltage that does not require a long insulation distance of about 100 V with a voltage divider. However, in such a method using a voltage divider, the insulation resistance, response speed, and measurement accuracy are limited by the voltage divider while using an optical measurement means, and the benefits of lightization can be enjoyed. Has become difficult.
[0015]
Therefore, the group at the University of Tokyo has proposed the voltage measuring device shown in FIG. 9 in “Pockels High-Voltage Measurement System”, IEEE Transaction on Power Delivery, Vol.15, N0.1 (2000). The basic principle configuration is the same as that of the voltage measuring apparatus shown in FIG. 7, but has a feature in the portion of the electro-optic crystal that detects the voltage. That is, a plurality of disc-shaped electro-optic crystals are arranged between the high-voltage electrodes, and the voltage is measured by measuring the electro-optic effect generated by the plurality of crystals. According to such a voltage measuring apparatus, it is possible to measure the voltage between the electrodes by integrating the electric field although it is incomplete. However, in this voltage measuring apparatus, since a relatively long distance between the electrodes is propagated by the beam into the gas, an error is likely to occur due to the influence of beam fluctuation.
[0016]
Similarly, a method that does not perform spatial propagation of long optical paths while integrating the electric field is "230 kV optical voltage transducer using a distributed optical electric field sensor system", Transmission and Distribution Conference and Exposition, 2001 IEEE / PES, Volume : 1, 2001. This is characterized in that a plurality of electric field sensors are placed in an insulator as shown in FIG. 10 and the electric field is integrated, and a plurality of independent electric field sensors are arranged to measure the voltage proposed by the group of the University of Tokyo mentioned above. Different from the device. Although the specific configuration of the electric field sensor is not described in this paper, it is expected that the influence of beam fluctuation can be reduced, and high accuracy can be expected. However, a plurality of sets of light sources, optical systems, light receivers, and electronic circuits are necessary, which not only increases the price, but also increases the number of parts may directly lead to a decrease in reliability.
[0017]
As described above, the photovoltage measuring device has a sensitivity error and a phase error due to environmental changes including temperature as described above. Further, since the behavior of the photovoltage measuring device is different from that of the current measuring device, it is easy to widen errors in measuring power and impedance, and the measurement accuracy is deteriorated. Furthermore, when a voltage divider is used for the measurement, the voltage resistance restricts insulation resistance, response speed, and measurement accuracy. In addition, photovoltage measuring devices aimed at voltage dividers have been proposed, but light propagation in long-distance gas is required, and many light sources and optical systems are required. There was a problem with reliability.
[0018]
The present invention has been proposed in order to solve the above-described problems of the prior art, and its purpose is to be resistant to environmental changes including temperature changes, and to operate stably. It is an object of the present invention to provide a highly accurate and highly reliable photovoltage measuring device which can avoid limitations on insulation resistance, response speed, and measurement accuracy due to the voltage divider by omitting the voltage divider.
Another object of the present invention is to realize a power or power amount measuring apparatus and an electrical equipment protection system that improve measurement accuracy and reliability by aligning phase characteristics of current and voltage.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 causes the electro-optic element to which a voltage to be measured is applied to transmit polarized light that circulates in opposite directions via a polarization plane preserving fiber coupler, In an optical voltage measuring apparatus that obtains the voltage by causing interference between both lights having a phase difference caused by light transmission, on both ends of the electro-optic element The light of the component which rotated the incident polarization plane 45 degrees is emitted. The first and second Faraday rotators are arranged, and the first Faraday rotator and the second Faraday rotator are The polarization planes of the light incident on the electro-optic element from opposite directions through the polarization-preserving fiber coupler are rotated by 45 ° in the opposite direction, and the polarization plane of the light emitted from the electro-optic element is 45 in the opposite direction. Rotate the original polarization The electro-optic element is applied with a voltage applied to the light in the reverse direction based on the polarization plane of the light rotated in the reverse direction 45 ° by the first and second Faraday rotators. Proportional Phase difference And output from the electro-optic element to the polarization-preserving fiber coupler. Receives light in both forward and reverse directions, and adjusts the intensity of the light due to the phase difference. It is characterized by connecting a detector that outputs an electrical signal based thereon.
In the first aspect of the invention, by disposing a Faraday rotator on both ends of the electro-optic element and transmitting polarized light that circulates in the opposite direction, it has the same configuration as the Sagnac interference type current measuring device, The voltage can be measured. Therefore, it is possible to realize a voltage measuring device that is excellent in environmental resistance and does not require a voltage divider. Moreover, it is possible to directly use techniques such as noise reduction and drift reduction that have been developed in Sagnac interference type gyro sensors and current measuring devices, and it is possible to improve measurement accuracy and operational reliability.
[0020]
According to a second aspect of the present invention, in the optical voltage measuring device according to the first aspect, a plurality of electro-optical elements are arranged and these electro-optical elements are optically connected in series.
According to the invention of claim 2, in addition to the invention of claim 1, the sum of arbitrary electric fields and voltages can be obtained by connecting a plurality of electro-optic elements as sensor units in series. it can. For this reason, simplification of a system is easy and reliability improves further.
[0021]
According to a third aspect of the present invention, in the optical voltage measuring device according to the second aspect, Faraday rotators are arranged on both sides of the plurality of electro-optic elements, and these Faraday rotators are optically connected in series. Yes.
According to the third aspect of the invention, in addition to the first aspect of the invention, a plurality of Faraday rotators arranged between the electro-optic elements are connected in series, whereby a plurality of series-connected electro-optics are provided. The polarization azimuth between the elements can be the same for both the light that rotates clockwise in the Sagnac interferometer and the light that rotates counterclockwise. Therefore, the influence of the birefringence change in the optical path between the electro-optic elements can be suppressed, and a highly accurate photovoltage measuring device can be realized.
[0022]
An apparatus for measuring electric power or electric energy according to the invention of claim 4 is characterized by using the optical voltage measuring apparatus according to any one of claims 1 to 3.
According to the power or power amount measuring device of claim 4, the optical voltage measuring device is used as a voltage measuring unit of the power or power amount measuring device, so that the optical voltage measuring unit side and the photocurrent measuring unit side are optical. Components and electronic circuits can be shared. Since the electro-optic effect and the Faraday effect act on the current / voltage without time delay, there is no need to perform phase compensation. Therefore, the phase characteristics of current and voltage can be made uniform, and the phase difference between current and voltage can be accurately detected. As a result, electric power or electric energy can be measured with high accuracy.
[0023]
According to a fifth aspect of the present invention, there is provided a protection system for an electric device using the optical voltage measuring device according to any one of the first to third aspects.
According to the fifth aspect of the present invention, the photovoltage measuring device and the photocurrent measuring device can be realized with the same configuration. Therefore, the phase relationship between the voltage and current can be accurately captured, and the protection system can be highly accurate.
[0024]
According to a sixth aspect of the present invention, in the electrical equipment protection system according to the fifth aspect, the impedance up to the fault point is measured in combination with a predetermined photocurrent measuring device, the fault point is determined from the impedance, and the electric equipment is It is characterized by protection.
According to such a sixth aspect of the invention, the voltage / current phase relationship can be accurately measured, and the impedance can be measured with high accuracy. Therefore, the accident point can be accurately determined, and the protective operation can be performed more stably.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be specifically described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same member as the structural member shown in the prior art example of FIG.7 and FIG.8, and description is abbreviate | omitted.
[0026]
[1] First embodiment
(1-1) Configuration
The first embodiment corresponds to the invention of claim 1, and FIG. 1 is a configuration diagram of the first embodiment. In the first embodiment, the EO element 8 to which a voltage to be measured is applied is caused to transmit polarized light that circulates in opposite directions via the polarization plane preserving fiber coupler 4, and a phase difference is generated by this light transmission. A Sagnac interference type optical voltage measuring device that obtains a voltage by interfering the two lights, and first and second Faraday rotators 5 and 6 that rotate the polarization plane by 45 ° are arranged on both ends of the EO element 8. And transmitting light. The light source 1, the coupler 2, the polarizer 3, the polarization-maintaining fiber coupler 4, the phase modulator 10 and the detector 11 are common to the Sagnac interference type photocurrent measuring apparatus shown in FIG. .
[0027]
One EO element 8 is disposed in the Sagnac interferometer and is based on a lithium niobate waveguide. In the first Faraday rotator 5 and the second Faraday rotator 6, the rotation directions of the polarization planes are reversed. Furthermore, an electronic circuit 12 is connected to the detector 11. The electronic circuit 12 is configured to calculate the voltage 7 applied to the EO element 8 based on the electrical signal converted by the detector 11.
[0028]
(1-2) Operation
In the first embodiment having the above configuration, the light emitted from the light source 1 passes through the coupler 2 and is linearly polarized by the polarizer 3. The light emitted from the polarizer is branched by the polarization maintaining fiber coupler 4 into light propagating clockwise through the Sagnac interferometer and light propagating counterclockwise through the Sagnac interferometer. The light propagating clockwise through the Sagnac interferometer is rotated by 45 ° in the plane of polarization by the first Faraday rotator 5 and the phase difference proportional to the applied electric field due to the electrooptic effect in the EO element 8 to which the voltage 7 is applied. Receive. At this time, the incident polarization direction to the lithium niobate waveguide is the same as the intrinsic birefringence axis of the waveguide. This light is again rotated by the second Faraday rotator 6 in the direction of polarization of 45 ° and in the opposite direction to the first Faraday rotator 5, becomes the original polarization direction, and is coupled to the polarization maintaining fiber 9. . The clockwise light coupled by the polarization maintaining fiber 9 is further phase-modulated by the phase modulator 10 and reaches the polarization maintaining fiber coupler 4.
[0029]
On the other hand, the light propagating counterclockwise through the Sagnac interferometer passes through the optical path completely opposite to the light propagating clockwise through the Sagnac interferometer, and again propagates counterclockwise through the Sagnac interferometer with the polarization-maintaining fiber coupler 4. Interferes with light. At this time, the light propagating counterclockwise through the Sagnac interferometer is rotated by 45 ° by the second Faraday rotator 6 and coupled to the EO element 8 by the lithium niobate waveguide. It propagates in the lithium niobate waveguide with a polarization orthogonal to the propagated light, and a phase difference due to the electro-optic effect opposite to that of the clockwise light is given. The interference light that has passed through the polarization-maintaining fiber coupler 4 passes through the polarizer 3 and the coupler 2 again, and is converted into an electrical signal by the detector 11. The electronic circuit 12 calculates and outputs an applied voltage from this electrical signal.
[0030]
(1-3) Effects
According to the first embodiment as described above, the Sagnac interferometer is used as in the current measuring apparatus shown in FIG. 8 except for the EO element 8 and the Faraday rotators 5 and 6 which are sensor units. All optical components and electronic circuits can be made identical. For this reason, it is easy to obtain a photovoltage measuring device having the same characteristics as those of the Sagnac interference type photocurrent measuring device. Therefore, excellent characteristics can be exhibited even under severe environmental conditions including temperature changes. In addition, since a voltage divider is not required, the limitations on insulation resistance, response speed, and measurement accuracy associated with the installation of the voltage divider can be eliminated, and the merit of opticalization can be fully enjoyed.
[0031]
By the way, the point to be noted in the voltage measuring apparatus according to the first embodiment is that the polarization of light that circulates around the Sagnac interferometer clockwise and counterclockwise is the same. This is because if the polarizations are different, a time difference occurs between the light that circulates clockwise and the light that circulates counterclockwise, and accurate voltage measurement cannot be performed. For this reason, in the first embodiment, the polarization-maintaining fiber 9 is used as the optical fiber to be used. The polarization plane preserving fiber 9 is a fiber having a large linear birefringence, and the polarization is preserved along the birefringence axis when the polarization is incident on the birefringence axis. Both the light and counterclockwise light can propagate the same polarization. The present invention can also be realized by propagating depolarized light in a single mode fiber by the method disclosed in Japanese Patent Application No. 2000-098820.
[0032]
Furthermore, since the first embodiment is basically a Sagnac interferometer, it is needless to say that techniques such as noise reduction and drift reduction in a Sagnac interference type gyro sensor and current measuring device that have already been developed can be used as they are. . For example, it is possible to perform zero-point method measurement by serrodyne modulation, modulation using a harmonic of modulation, stabilization of light quantity, and the like. In the first embodiment, the polarization is fixed by the high birefringence fiber and the waveguide, and there is no fear of polarization fluctuation and optical axis deviation. For this reason, the problem of change in birefringence due to optical path deviation, which has been a problem with conventional photovoltage measuring devices, can not occur, and even electro-optic crystals with natural birefringence should be used without problems. Can do. Moreover, since the phase modulator 10 is used in the first embodiment, it is effective for improving the sensitivity at the time of a small signal.
[0033]
[2] Second embodiment
(2-1) Configuration
The second embodiment corresponds to the invention of claim 2, and FIG. 2 is a configuration diagram of the second embodiment. The structural feature of the second embodiment is that two EO elements 8 are arranged in a Sagnac interferometer, and these EO elements 8 are optically connected in series. At this time, the birefringence axis is aligned with both the EO elements 8 and the polarization maintaining fiber 9. Since the configuration and operation from the light source 1 to the electronic circuit 12 have the same configuration as the first embodiment and perform the same operation, the same reference numerals are given and description thereof is omitted. Further, in the second embodiment, the phase modulator 10 is not used, but the relationship between the voltage and the sensor output is merely a cosine function to a sine function, and a modulator is not necessarily required.
[0034]
(2-2) Effects
According to the second embodiment, the sum of voltages applied to the EO elements 8 can be detected by connecting the EO elements 8 in series. Therefore, when the electric field is integrated to obtain a voltage, it can be detected simply by connecting the EO elements for detecting each electric field in series, and a simple system can be constructed. Therefore, a highly reliable electric field integration type photovoltage measuring device can be obtained. Also, one of the EO elements 8 can be used for applying a reference voltage for performing the null method.
[0035]
[3] Third embodiment
(3-1) Configuration
The third embodiment corresponds to the invention of claim 3, and FIG. 3 is a configuration diagram of the third embodiment. Since the configuration and operation from the light source 1 to the electronic circuit 12 are the same as those in the second embodiment, the same reference numerals are given and description thereof is omitted. The difference from the second embodiment is that third and fourth Faraday rotators 13 and 14 are further arranged between the EO elements 8 optically connected in series.
[0036]
(3-2) Effects
In the second embodiment, the light propagating clockwise through the Sagnac interferometer and the polarization of the light propagating counterclockwise are orthogonal in the polarization-maintaining fiber connecting the EO elements. In the third embodiment, by adding the third and fourth Faraday rotators 13 and 14 between the two EO elements 8, both the light propagating clockwise in the Sagnac interferometer and the light propagating counterclockwise are obtained. The same polarized wave propagates through the polarization maintaining fiber 9 connecting the EO elements 8. Therefore, this is effective when the change in linear birefringence in the polarization-maintaining fiber 9 cannot be ignored in measurement.
[0037]
[4] Fourth embodiment
(4-1) Configuration
By the way, the present invention is not limited to the waveguide type sensor, and can also be realized by using spatially propagated light as shown in FIG. In addition, since the basic composition in 4th Embodiment is the same as 1st Embodiment, the same number is attached | subjected to the member of the same function, and description is abbreviate | omitted.
[0038]
In the fourth embodiment, instead of using the polarization maintaining fiber 9, light is propagated by a spatial beam. For branching light, a partial reflection mirror 15 having a reflectance of about 50% is used instead of the coupler. The electro-optic crystal 26 uses a bulk material as it is, and a voltage in the lateral direction is applied to the optical path. Further, a folding mirror 16 is used to construct a Sagnac interferometer.
[0039]
(4-2) Effects
According to such a fourth embodiment, since the radio wave of light is a spatial beam, handling is more complicated than in the first embodiment, but the same signal processing system as the Sagnac interferometric current measuring instrument However, it can be expected that the same effect as the above embodiment can be expected.
[0040]
[5] Fifth embodiment
(5-1) Configuration
The fifth embodiment shown in FIG. 5 is a power or power amount measuring apparatus using the first embodiment, and corresponds to the invention of claim 4. In addition, since the part which measures a voltage is the same as 1st Embodiment, it attaches | subjects the same number and abbreviate | omits description. Further, since the current measurement part is the same as that in FIG. In the fifth embodiment, power is calculated using the multiplier 21 from the output of the voltage measurement device and the output of the current measurement device.
[0041]
(5-2) Effects
As is apparent from FIG. 5, most of the components are the same in the voltage measuring device and the current measuring device. Since the electro-optic effect and the Faraday effect act on the current / voltage without time delay, there is no need to perform phase compensation. That is, the phase error generated in the electronic circuit 12 works in the same direction in the current measuring device and the voltage measuring device, and the phase difference between the current and voltage is accurately detected. As a result, the measurement error can be made very small when the multiplier 21 calculates the power from the outputs of the voltage measuring device and the current measuring device. This means that highly accurate power measurement can be performed more simply. Therefore, in the fifth embodiment, it is only necessary to design so that the sensitivity is stable, which can contribute to the reduction of the number of parts and the improvement of the reliability.
[0042]
[6] Sixth embodiment
(6-1) Configuration
6th Embodiment respond | corresponds to invention of Claim 6, It is a power transmission line distance relay using the said 3rd Embodiment, Comprising: The protection system of an electric equipment is comprised. In FIG. 6, the voltage measurement part is the same as that of the third embodiment, so the same number is assigned and the description is omitted. Further, since the current measurement part is the same as that in FIG.
[0043]
The sensing fiber 19 of the photocurrent measuring device is attached to the upper part of the insulator 22 and maintains insulation from the ground. Three EO elements 8 included in the voltage measuring device are attached to the inside of the insulator, and are configured to measure the voltage by equivalently integrating the electric field between the transmission line as the current path 20 and the ground. . The electronic circuit 12 is installed in a field board 23 installed near the root of the insulator 22. In the field panel 23, a ground fault relay 24 for calculating voltage / current based on signals from both measuring devices is arranged.
[0044]
(6-2) Effects
In the sixth embodiment, as in the fifth embodiment, since most of the components are the same in the voltage measuring device and the current measuring device, there is no need to perform phase compensation, and the current-voltage The phase difference can be accurately detected. The ground fault relay 24 calculates voltage / current based on signals from both measuring instruments. When the power transmission system is operating normally, this calculated value shows a sufficiently large value. However, once a ground fault or short circuit accident occurs, a large current flows through the transmission line, and this value becomes small. At the time of ground fault and short circuit, this value is equal to the impedance to the ground fault point and the short circuit point. That is, the distance from this value to the accident point can be obtained. When an accident within the protection section of the relay is assumed due to the determined distance, the relay operates the circuit breakers at both ends of the accident section (not shown) to remove the accident section. The signal used is the ratio of voltage and current signals, and relative accuracy becomes a problem. For this reason, as shown in the sixth embodiment, the merit of performing measurement with substantially the same configuration for both voltage and current is great. In the sixth embodiment, phase information can be acquired accurately. Therefore, it is possible to accurately determine the aspect and direction of the accident, and it is possible to further improve the reliability.
[0045]
【The invention's effect】
As described above, according to the photovoltage measuring device of the present invention, it is resistant to environmental changes such as temperature changes, can operate stably, and further, by eliminating the voltage divider, insulation resistance by the voltage divider Thus, it is possible to obtain a highly accurate and highly reliable photovoltage measuring device that can avoid limitations on response speed and measurement accuracy. In addition, according to the present invention, it is possible to realize a power or power amount measuring apparatus and an electrical equipment protection system in which measurement accuracy and reliability are improved by aligning current / voltage phase characteristics.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment according to the present invention.
FIG. 2 is a configuration diagram of a second embodiment according to the present invention.
FIG. 3 is a configuration diagram of a third embodiment according to the present invention.
FIG. 4 is a configuration diagram of a fourth embodiment according to the present invention.
FIG. 5 is a configuration diagram of a fifth embodiment according to the present invention.
FIG. 6 is a configuration diagram of a sixth embodiment according to the present invention.
FIG. 7 is a configuration diagram of a conventional photovoltage measuring device.
FIG. 8 is a configuration diagram of a conventional Sagnac interference type photocurrent measuring device.
FIG. 9 is a configuration diagram of a conventional photovoltage measuring device.
FIG. 10 is a configuration diagram of a conventional photovoltage measuring device.
[Explanation of symbols]
1 ... Light source
2 ... Coupler
3 ... Polarizer
4. Polarization plane preserving fiber coupler
5 ... First Faraday rotator
6 ... Second Faraday rotator
7 ... Voltage
8 ... EO element
9 ... Polarization-maintaining fiber
10 ... Phase modulator
11 ... Detector
12 ... Electronic circuit
13 ... Third Faraday rotator
14 ... Fourth Faraday rotator
15 ... Partial reflector
16 ... Folding mirror
17: First quarter wave plate
18: Second quarter wave plate
19 ... sensor fiber
20 ... Current path
21 ... Multiplier
22 ... Reiko
23. On-site board
24 ... Distance relay
26 ... Electro-optic crystal
27 ... Analyzer
34 ... Electrode terminal
35 ... Synchronous detector
36. Oscillation circuit

Claims (6)

Polarized light that circulates in opposite directions is transmitted to an electro-optic element to which a voltage to be measured is applied via a polarization plane preserving fiber coupler, and both light beams having a phase difference are caused to interfere with each other by the transmitted light. In the photovoltage measuring device for obtaining
First and second Faraday rotators that emit light having a component obtained by rotating the incident polarization plane by 45 ° are disposed on both ends of the electro-optic element,
The first Faraday rotator and the second Faraday rotator rotate the polarization plane of the light incident on the electro-optic element from the opposite directions via the polarization plane preserving fiber coupler 45 ° in the opposite direction, The polarization plane of light emitted from the electro-optic element is rotated by 45 ° in the reverse direction to obtain the original polarization direction,
The electro-optic element is based on the polarization plane of light rotated 45 ° in the reverse direction by the first and second Faraday rotators, and gives a phase difference proportional to the applied voltage to the light in the reverse direction, respectively. And
The polarization-preserving fiber coupler is connected to a detector that receives light in both forward and reverse directions output from the electro-optic element and outputs an electric signal based on the intensity of the light due to the phase difference. Photovoltage measuring device. The photovoltage measuring device according to claim 1, wherein a plurality of the electro-optic elements are arranged and these electro-optic elements are optically connected in series. 3. The photovoltage measuring device according to claim 2, wherein Faraday rotators are arranged on both sides of the plurality of electro-optical elements, and these Faraday rotators are optically connected in series.   An apparatus for measuring electric power or electric energy, wherein the optical voltage measuring apparatus according to claim 1 is used.   A protection system for electrical equipment, wherein the optical voltage measuring device according to any one of claims 1 to 3 is used.   6. The electrical equipment protection system according to claim 5, wherein an impedance up to an accident point is measured in combination with a predetermined photocurrent measuring device, and the electrical equipment is protected by locating the accident point based on the impedance.

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