JPS62156568A - Optical voltage/electric field measuring instrument - Google Patents

Abstract

PURPOSE:To realize easily a measurement of a DC voltage, and also, to measure an AC voltage with a high accuracy by forming a voltage dissipation electrode in a pair of voltage/electric field measuring electrodes, respectively, connecting a switch between both voltage dissipation electrodes, and also closing this switch immediately before the measurement. CONSTITUTION:A voltage and an electric field which are applied to an optical modulating element 4 immediately before starting a measurement are set to zero temporarily by short-circuiting a glass electrode 2A, a non-modulating state is made and optical power of a base light at that time is derived from an O/E 10, compared by a comparator 11 for constituting a negative feedback with a reference voltage 12, a shift from a prescribed value is corrected, and thereafter, a light emitting element of an E/O 9 is driven to as to go to a reference value of the base light by an E/O driving circuit 9A. At the time of an actual measurement, the base light to which an AC signal has been superposed is applied to the comparator 11 by applying an AC voltage, etc., and the base light itself is varied. Accordingly, at the time of a measurement, a base light correcting value immediately before the measurement is held by a holding circuit 8. Namely, it is because a variation of the base light is small to such an extent that it can be disregarded, when a light voltage measurement is executed immediately after a correction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measuring device for optically measuring voltage or electric field in a power distribution system or the like.

[Conventional technology]

Optical measuring instruments have been adopted as a means for monitoring distribution@, vA voltages, and electric fields in power distribution systems. The advantage of the optical method is that the measured voltage and electric field information is
Transmission is possible without being affected by the voltage or electric field of the power distribution line.

In optical voltage/electric field sensors, the basic light is important. In the conventional method, the average value of the optical reception power P+ is calculated, and the signal component optical power Pt is further divided by Pl to obtain the measured value.
There were problems such as the complexity of the circuit and the inability to measure DC voltage.

Conventional voltage/electric field measuring instruments are limited to "alternating current" measurements for the reasons described below in the method shown in FIG. 3, which measures voltage purely optically. First, we will explain the basic operating principles of optical voltage/electric field sensors and the internal configuration of conventional measuring instruments.

In FIG. 3, the voltage/electric field measuring device includes a reading section 31
．． It is composed of two fibers 34 and 35 and a detection section 36. The detection unit 36 includes a metal oxide crystal having an electro-optic effect, for example, BSO (Bi+.Sing.).
, lithium niobate (LiNbOl), silicon oxide (Si
ng) etc. (hereinafter referred to as optical sensors) are mainly used.

The reading unit 31 further includes electricity E (=el
an electric-to-optical conversion element (hereinafter referred to as rEloJ) 32 that converts electrics into optical zero (=optics);
Conversely, a photoelectric conversion element (hereinafter referred to as "0/
33 (referred to as EJ) and a signal processing circuit 38, which are connected as shown in FIG.

The operation and signal flow are as follows.

First, DC base light is supplied from the reading section 31 to the optical sensor 36 via one optical fiber 34 through the E1032. The direct current base light is so called because the intensity of the light is almost constant and modulation is applied to this light as a base, as will be described later.

Optical sensors consist of several optical components, including crystals,
The base light passes through these optical circuits. At this time, the optical sensor is operated by an applied voltage or electric field. Then, a change in intensity occurs in this base light.

In other words, the amount of change in the optical power output from the optical sensor is in phase with the applied voltage (electric field). Therefore, another optical fiber 35 guides this modulated light to the reading section 31, and the O
If you return it to an electric signal with /E33, you can find the original applied voltage (electric field). However, in reality, the power of light emitted from E1032 does not remain constant.

This is because the loss of optical power changes due to temperature changes and aging of the light emitting diode and laser diode, the length and bending of the optical fiber transmission path, and aging.

Therefore, there are the following two conventional countermeasures against the problem. One is to extract the DC component from the output of the O/E, and use a signal processing circuit to keep this value constant.
This applies negative feedback to Elo's input.

In optical sensors, the degree of modulation with respect to the base light is always constant regardless of the intensity of the base light, so if the DC component of the O/E output is constant, the AC component (signal change)
becomes stable. However, the prerequisite for this is that the fluctuation of the optical power is extremely slow and is closer to a direct current than an alternating current component, and that no direct current component is applied to the optical sensor.

Another method, as shown in FIG. 4, is to divide the AC component of the output of the O/E by the DC component without applying negative feedback.

[Problem that the invention seeks to solve]

Conventional devices can measure alternating current signals stably and precisely in this way, but due to their nature, they cannot measure direct current. In addition, the circuit is complicated, as a division circuit is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device capable of measuring voltage and electric field by means different from conventional methods.

[Means for solving problems]

In order to achieve the above object, the present invention provides an optical voltage/electric field measuring device including an electro-optical sensor, two optical fibers, and a reading section, in which a pair of polarized light beams constituting the electro-optic sensor section is provided. A pair of voltages placed in the gap between the
A voltage dissipation electrode is formed on each of the electric field measuring electrodes, a switch is connected between both voltage dissipation electrodes, and switch driving means is provided for closing the switch immediately before measurement.

More preferably, the voltage/electric field measuring electrode is formed on one surface of a transparent material such as glass, and the voltage dissipation electrode is formed on the other surface of the transparent material.

[Example] The present invention will be specifically described below based on an example shown in the drawings.

FIG. 1 shows an example of a system embodying the method of the present invention using a contact switch.

Of course, the switch can also be a semiconductor switch or the like.

The optical fiber and reading section are the same as in the conventional method, so
The optical sensor section and E/○ circuit will be explained.

The optical sensor section includes an optical fiber 5 that guides the base light emitted from the E109 to the optical sensor section, an optical fiber 6 that guides the optical power signal emitted from the optical sensor section to the reading section, a light modulation element 4 such as an optical crystal, and a tip section. A polarizer 1 that keeps the light plane constant, an analyzer IA that reads polarization information signals, a transparent electrode 2 that applies voltage and electric field to the light modulation element 4, and a voltage that creates a non-modulation condition for the modulation element 4. - It is composed of a transparent electrode 2A for dissipating the electric field.

The voltage/electric field dissipation electrode 2^ is provided to provide insulation from the source to be measured in order to avoid this, since directly short-circuiting the voltage measuring electrode 2 would cause destruction or adverse effects on the source to be measured.

Furthermore, the optical element 4 for optical modulation is expensive, and poor yield during electrode deposition tends to increase the cost. Therefore, by avoiding direct processing of the modulation element and attaching the electrode to low-cost glass, cost and other costs can be reduced. We are aiming to improve this.

Base 4! The reference voltage generated in the lightning voltage generation circuit 12 is supplied to the comparator 11. Hold circuit 8. 21 via E/○ drive circuit 9^
The light emitting elements such as light emitting diodes and laser diodes in section 09 are driven to generate a predetermined base light. O/E 1
0 The reading circuit reads the base light and the optical power signal superimposed on the base light.

The DC reference voltage is determined by comparator 11. Hold circuit 8. E1
A light emitting element such as a light emitting diode or a laser diode of 2109 parts is driven through the 0 drive circuit 9A, and base light is supplied to the sensor part.

The base light supplied to the sensor section is polarized by the polarizer 1, and after the polarization planes are aligned, it enters the light modulation element 4 and is modulated by a modulation voltage, becoming elliptically polarized light. Furthermore, the signal output is detected by the analyzer 18, and the optical fiber 6 outputs the O/E signal.
The signal is guided to the reading section 10 and becomes an electrical signal output.

The above is the basic operation, but the present invention further provides timing as shown in the time chart of FIG.
Immediately before the start of modulation, the voltage and electric field applied to the light modulation element 4 are temporarily brought to zero by shorting the glass electrode 2A, creating a non-modulation state and reducing the optical power of the base light at that time to O/
E10 is calculated, compared with the reference voltage 12 by a comparator 11 constituting negative feedback, and after correcting the deviation from a predetermined value, the E10 drive circuit 9A
The light emitting element 109 is driven so as to have the reference value of the base light.

During actual measurement, the comparator 11 is
Base light with overlapping alternating current signals is applied, and the base light itself fluctuates. Therefore, during measurement, the base light correction value immediately before the measurement is held in the hold circuit 8. That is, if the photovoltage measurement is performed immediately after correction, the variation in the base light is negligibly small.

By the above operation, the base light is always maintained at a predetermined value determined by the reference voltage.

〔Effect of the invention〕

As described above, according to the present invention, when measuring AC voltage, it is possible to accurately measure AC voltage by simply separating and displaying the AC voltage using a simple AC signal separation circuit such as capacitor coupling.

Furthermore, measurement of the DC voltage can be easily realized by using an operational amplifier to extract the difference between the reference voltage and the base DC voltage component when DC is applied.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing its operation, and FIGS. 3 and 4 are block diagrams showing a conventional configuration.

Claims (1)

[Claims] 1. An optical voltage/electric field measuring instrument comprising an electro-optical sensor, two optical fibers, and a reading section, including: a gap between a pair of polarizers constituting the electro-optical sensor section; A voltage dissipation electrode is formed on each of the pair of voltage/electric field measurement electrodes disposed in the electrode, a switch is connected between the two voltage dissipation electrodes, and switch driving means is provided to close the switch immediately before measurement. Optical voltage/electric field measuring instrument. 2. The voltage/electric field measuring electrode is formed on one side of a transparent material such as glass, and the voltage dissipation electrode is formed on the other side of the transparent material. Optical voltage/electric field measuring instrument.