JPS62123364A - Optical voltmeter - Google Patents

Abstract

PURPOSE:To measure accurately and extensively high voltages including HF components, by receiving an element beam of light generated by right-angle intersection of polarized light elements in linear and parallel directions, among those beams of light passing through a Pockels element, by 2 photoelectric convertors. CONSTITUTION:A voltage subjected to be measured is applied to a pair of electrodes 17, 18 embracing a Pockels elements 16 and a beam of linearly polarized light running to the main axis of right-angle intersection refractive index through an angle of 45 deg. is irradiated to the element 16 in the direction in with it crosses an electric field and among the beams passing through the element 16, an element beam parallel to the linearly polarized light direction and right-angle intersecting element beam are received respectively by the photoelectric convertors 27, 28. And, each output wave form of the photoelectric convertors 27, 28 is stored in a wave memory 31 and a value of difference of light quantities of these element beams divided by the sum of the light quantities of these element beams and a value of coefficient indicating the Pockels effect using a conversion table stored preliminarily in a memory element by a digital arithmetic operating apparatus 32 from a temperature of the element 16 stored preliminarily in the memory element are read out and an applied voltage can be obtained by the calculation for the given equation.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical voltmeter that measures high voltage using a first-order electro-optical effect (Pockels effect), and particularly relates to an optical voltmeter that measures high voltage using a first-order electro-optical effect (Pockels effect), and particularly relates to an optical voltmeter that measures high voltage by expanding the measurement range and improving measurement accuracy. This invention relates to an optical voltmeter that can be used to

[Technical background of the invention and its problems]

As the voltage of power systems becomes higher, the test voltage of power equipment tends to increase. In addition, surge voltages are generated in grids due to the opening and closing of circuit breakers, etc., so when considering the insulation of power equipment, it is often necessary to measure these high voltages (~1000kV) and high frequency (~10MH2) voltages. ing.

As one such high voltage measurement technique, optical voltmeters using the Pockels effect have recently come into use. This voltmeter is 'L t NbO3,8i+2 S i 020. K
This is an application of the Pockels effect, in which when a voltage is applied to a Bockels element such as a DP, the optical phase difference between the two component lights in the direction of the principal axis of refractive index of light propagating through the Pockels element depends on the applied voltage. . This optical voltmeter has excellent insulation properties and has the advantage of being able to relatively easily measure high voltages in actual power systems.

The principle of this optical voltmeter will be explained in more detail with reference to FIG. Light guided through an optical fiber from a laser device (not shown) is converted into linear tin light IrJ by a polarizer 1. This direct aS light! 0 is the direction of the two principal axes of refractive index in which the plane of polarization of the Pockels element 2 is perpendicular to the Pockels element 2, that is, X.

The light is incident in the Z-axis direction at an angle of 45° to the Y-axis direction. When a voltage V to be measured is applied to the electrodes 3.4 arranged on both sides of the Pockels element 2 in the X-axis direction, the optical phase difference Δφ between the X and Y components of the output light of the Pockels element 2 changes. .

The size of this Δφ is Δφ−(rλ/d)V (1)
It is expressed as Here, r is a coefficient indicating the magnitude of the Pockels effect determined by the Pockels constant, the direction of the light beam, and the orientation of the Pockels element, °C is the length of the Pockels element 2 in two directions, and d is the thickness in the X direction. Therefore, the applied voltage V can be determined by measuring the optical phase difference Δφ.

Therefore, the output light from the Pockels element 2 is divided by, for example, a Wollaston prism 5 into a component 11 perpendicular to the polarization direction of the input light and a component 2 parallel to it. here,
If the P and S directions of the Wollaston prism are matched with the X and Y directions, the powers of 11 and I2 are respectively -I ro (1-CO32 (-+ Δ φ ) ) -
10(1-5in2Δφ) ・(2)-IO(
1+ cos2 (-+Δcb) )-I+ (1
+5in2Δφ) (3). Here, Ia is the power of input light.

When these It and I2 are converted into electrical signals by a photodetector and amplified by a differential amplifier, the output E becomes E-2I (15in2Δφ - (4). Here, in the range of Δφ (1), E"F21 B 2Δφ +410 (r ffi/d) V
-(5), and the output E of the differential amplifier becomes an output proportional to the voltage ■ applied to the Pockels element 2.

However, in such optical voltmeters, the intensity of the light output from the laser often fluctuates, and for this reason (5
) There was a problem in that Io in the equation fluctuated, resulting in a very large measurement error.

Therefore, in order to remove this error, the power of the input light is 10
is constantly monitored, and the output of the differential amplifier is divided using a 1JEf device, or (12-1ri)/(12+11> gon2(r℃/d)V...(■) Efforts have been made to remove the effects of fluctuations in Io.

However, this method has the disadvantage that the lower measurement limit of the voltmeter is determined by the noise of the divider, and that the divider is
There was a problem in that it could not respond to frequencies as high as 0 MHz.

In addition, with conventional optical voltmeters, linearity is compensated only within the range of Δφ (1), and for example, when it reaches Δφ - 20°, the measurement error reaches about 2%. Therefore, the voltage measurement range is narrow. There was a drawback.

Furthermore, LiNbO, which has high sensitivity as a Pockels element,
3, the value of r fluctuates as the temperature changes due to the influence of birefringence due to temperature, so the measurement error caused by this cannot be ignored.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an optical voltmeter that can measure high voltages containing high frequency components over a wide measurement range and with high accuracy.

[Summary of the invention]

The present invention applies a voltage to be measured to a pair of electrodes attached to sandwich a Pockels element, and applies an electric field to linearly polarized light at an angle of 45° to the orthogonal principal axis of the refractive index of the Pockels element. Among the light incident in a direction perpendicular to the direction and transmitted through the Pockels element, component light parallel to the linear polarization direction and component light perpendicular to the linear polarization direction are respectively received by two photoelectric converters. An optical voltmeter configured to measure the voltage value applied to the electrode from each output of the optical voltmeter is characterized by comprising the following means.

That is, the optical voltmeter according to the present invention includes a wave memory that stores each output waveform of the photoelectric converter, a temperature sensor that measures the temperature of the Pockels element, and the two components stored in the wave memory. A digital calculation device that calculates the magnitude of the applied voltage using a conversion table from a value obtained by dividing the difference in light m by the sum of the light amounts of the two component lights and the temperature detected by the temperature sensor. This is what I did.

〔Effect of the invention〕

According to the present invention, the wave memory stores the light intensity waveforms of the two component lights with respect to the instantaneous voltage waveform, and the processing that was conventionally performed by a divider is digitally performed by a digital arithmetic unit. There is no need to use a divider, measurement errors can be extremely reduced, and problems caused by the processing speed of the divider can be avoided.

In addition, in the present invention, since the voltage value is obtained from the two component lights and the temperature sensor data using a conversion table, the optical phase difference between the components in the orthogonal refractive index principal axis direction of the transmitted light of the Pockels element Even when Δφ is large, accurate converted values can be obtained. Therefore, the measurement range is Δφ
(There is no need to limit the measurement range to 1, and the measurement range can be expanded.

Furthermore, according to the present invention, the temperature compensation of the measured value is performed using information from the temperature sensor, so that measurement accuracy can also be improved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an optical voltmeter according to this embodiment. In the figure, reference numeral 11 denotes a laser device, and a light output section thereof is connected to one end of an optical fiber cable 13 via an optical fiber connector 12 with a microlens. The other end of this optical fiber cable 13 is also connected to the entrance portion of a polarizer 15 via an optical fiber connector 14 with a microlens. The polarizer 15 has a function of converting incident light into linearly polarized light. A Pockels element 16 is connected to the output portion of the polarizer 15 .

This Pockels element 16 and the polarizer 15 are such that the plane of polarization of the output light from the polarizer 15 is at an angle of 45'' with respect to the two mutually orthogonal principal refractive index axes of the Pockels element 16, that is, the X axis and the Y axis. and Pockels element 1
The optical axis of the light incident on 6 coincides with the two axes. The Pockels element 16 has a pair of electric currents tii7. IS is attached, and this electronic mi7. The voltage to be measured is applied to is. A polarizing beam splitter 19 is connected to the output end of the Pockels element 16. The polarizing beam splitter 19 is arranged so that at least one of its two orthogonal principal axis directions of refractive index coincides with the principal axis direction of the refractive index of the polarizer 15 . The beam splitter 19 has a function of separating the output light from the Pockels element 16 into two main axis direction components and emitting each component light 11 and 12 from two output ends. One end of an optical fiber cable 21 is connected to one output end of the polarizing beam splitter 19 via an optical fiber connector 20 with a microlens.
Also, a total reflection mirror 22 is provided at the other output end. One end of an optical fiber cable 24 is connected via an optical fiber connector 23 with a microlens. The other ends of these two optical fiber cables 21.24 are respectively connected to photoelectric converters 27.28 via microlensed optical fiber connectors 25.26. These photoelectric converters 27 and 28 are composed of, for example, a photomultiplier tube, an avalanche photodiode, etc., and convert light into electric current. The outputs from these photoelectric converters 27 and 28 are input to a wave memory 31 via amplifiers 29 and 30, respectively. The output from the wave memory 31 is input to the arithmetic unit 32. On the other hand, in order to measure the temperature of the Pockels element 16, a temperature sensor 33 is attached to the total reflection mirror 22, and the output from this temperature sensor 33 is also input to the above-mentioned performance device 32. Furthermore, this arithmetic unit 32 has a display gt for displaying the calculation results.
34 is connected.

In the optical voltmeter according to this embodiment configured as described above, the laser device! ! The output light from 11 is guided into the inside of the optical fiber cable 13 by the optical fiber connector 12,
Further, the light is shaped into parallel light by an optical fiber connector 14 and is incident on a polarizer 15 . The light In converted into linearly polarized light by the polarizer 15 enters the Pockels element 16 at an angle of 45° with respect to its principal axis direction. At this time, Pockels element 1
6, an optical phase difference Δφ occurs between the two orthogonal polarized light components at the output end of the Pockels element 16, as shown in equation (1) above, and the output of the Pockels element 16 At the edges, it becomes elliptically polarized light.

The polarizing beam splitter 19 is composed of this Pockels element 16.
The output light is separated into a component light 11 perpendicular to the polarization direction of the human radiation light 1o and a component light 12 parallel to it. Each of these component lights 11 and 12 is photoelectrically converted by photoelectric converters 27 and 28, respectively.

Amplifiers 29 and 30 perform N current-to-voltage conversion,
For example, it is composed of a transducer amplifier. The outputs of amplifiers 29 and 30 are input to wave memory 31.

The wave memory 31 is configured as shown in FIG. 2, for example. In other words, the input signal of each component light is
The signal is inputted to an A/D converter 43 via an input attenuator 41 and an amplifier 42, and A/D converted at a predetermined sample time. The obtained digital data is stored in the storage device 44.
is stored at a predetermined sample timing. memory 114
The data stored in 4 is outputted at a predetermined timing via an output control circuit 45. In addition, amplifier 4
The output of No. 2 is also given to the trigger circuit 46. The trigger circuit 46 outputs a trigger pulse to the timing control circuit 47 when a surge voltage or the like is applied, and causes the timing control circuit 47 to start operating. The timing control circuit 47 sends a predetermined timing pulse to the A/D converter 4.
3. The signal is applied to the storage device W144 and the output control circuit 45 to control them.

Next, the processing unit M32 performs the following processing to calculate the voltage value V applied to the electrodes 17 and 18.

First, as shown in FIG. 3, each component light data 11.12 is input from the wave memory 31, and temperature data T is input from the concentration sensor 33 (51).

In the arithmetic unit 32, Ic=(12-It)/(I2-Is)-5i
The calculation n2Δφ (7) is performed (52). Since this calculation is performed digitally rather than by a divider, the measurement error is determined solely by the noise of the photoelectric converters 27 and 28. This noise is smaller than that of a conventional divider.

Next, read out the value of r corresponding to the temperature T detected by the temperature sensor 33 from the r characteristic table (conversion table) stored in advance in the storage element (53), and use the conversion table to convert V- (d/(2rffi)) sin'lc ・(s
) is performed to find the applied voltage (54).

Here, we do not assume Δφ (1, so Δφ≦π/2
Accurate measurements can be obtained within the range of .

Once the voltage ■ has been determined as described above, it is displayed on the display device 134.

According to the above embodiment, the instantaneous voltage fluctuation is accurately captured by the wave memory 31, and furthermore, this data is digitally operated to obtain the voltage value V, so that a wide range can be obtained as described above. This enables large and highly accurate measurements.

Note that the present invention is not limited to the embodiments described above.

In the above embodiment, a polarizing beam splitter is used to separate the output light of the Pockels element 16 into each component light, but a Wollaston prism may be used instead. Further, other optical means can be modified and implemented in various ways without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an optical voltmeter according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a wave memory in the voltmeter, and FIG. 3 is a calculation device in the voltmeter. FIG. 4 is a diagram for explaining the basic principle of an optical voltmeter using a Pockels element. 1.15... Polarizer, 2.16... Pockels element, 3.4.17.18... Electrode, 5... Wollaston prism, 11... Laser device, 12.14.2
0゜23.25.26...Optical fiber connector, 13
゜21.24... Optical fiber cable, 19... Polarizing beam splitter, 22... Total reflection mirror, 28.
29...Photoelectric converter, 33...Temperature sensor. Figure 3 Figure 4

Claims (1)

[Claims] A Pockels element, a pair of electrodes attached to sandwich the Pockels element and to which a voltage to be measured is applied;
means for inputting linearly polarized light at an angle of 5° in a direction perpendicular to the direction of the electric field; and means for receiving component light parallel to and perpendicular to the linear polarization direction of the light transmitted through the Pockels element, respectively. In an optical voltmeter, the optical voltmeter is equipped with two photoelectric converters that perform photoelectric conversion, and measures the voltage value applied to the electrode from each output of these photoelectric converters, and each output waveform of the photoelectric converter is a wave memory for storing, a temperature sensor for measuring the temperature of the Pockels element, a value obtained by dividing the difference in the amount of light between the two component lights stored in the wave memory by the sum of the amounts of the two component lights, and the temperature sensor for measuring the temperature of the Pockels element; An optical voltmeter comprising: a digital arithmetic unit that calculates the magnitude of the applied voltage from the temperature detected by the temperature sensor using a conversion table.