JPS5897664A - Voltage measuring device - Google Patents

Abstract

PURPOSE:To obtain a voltage measuring device having high reliability and superior surge resistance and noise resistance and is not influenced by the loss of an optical transmission system, by frequency modulating the voltage signal of a high potential part and transmitting the result in the form of a light output. CONSTITUTION:When an AC high voltage is applied between a conductor 1 and a reference potential, voltages are induced at electrodes 2 and 3 at specified distance apart from the conductor 1 and when the polarity is positive or negative, an electroluminescence element 4 or 5 performs respectively electric field light emission. This light emission turns phototransistors TRs 8 and 9 conductive to hold the potentials of the electrodes 2 and 3 nearly at zero. The, the electroluminescence element turns off and the TRs 8 and 9 are cut off to induce voltages at electrodes 2 and 3 again, repeating said operation thereafter. The frequency-modulated light signal is transmitted to a remote point through optical fiber cables 12 and 13 and converted by photodetectors 14 and 15 into electric signals, which are inputted to a polarity inverting circuit 20 through waveform shaping circuits 16 and 17, AND circuit 18, and frequency-voltage converting circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage measuring device for measuring the voltage of a high potential section of an electrical device such as a substation to which a high voltage is applied.

Conventionally, this type of voltage measuring device includes a voltage transformer,
There are measurement devices that are directly connected to the applied source, such as a capacitor partial voltage, and the output signal is also transmitted electrically, or purely optical measurement devices that use electro-optical elements (using the Pockels effect). The former had the negative effect of noise intrusion due to surges, etc. In order to avoid this, a method is also used in which electrical signals are converted into optical signals and transmitted near the measuring part (instrument transformer, etc.), but in this case, a power source is required for the conversion. there were. In the latter case, although there is no drawback like the former, the voltage information is amplitude-modulated, so slight changes in loss in the transmission system
This had the disadvantage of causing errors.

This invention was made in order to eliminate the above-mentioned drawbacks, and includes transmitting optical signals in order to improve noise resistance, requiring no power supply in the detection section, and using optical signals that are not amplitude modulated. To provide a ground pressure measurement device that is frequency modulated without any frequency modulation.

An embodiment of the present invention shown in the drawings will be described below.

In the figure, (1) is a conductor charged to a high potential, (2)
(3) is a pair of electrodes separated from the conductor (1) by a predetermined distance, (
4) (5) is an electroluminescent element, (6) (
7) are the limiting resistances when the phototransistor (8J (9) is turned on, QQqυ is the diode, and the conductor (1)
The polarities of the phototransistors (3) and (9) and diodes are changed so that they operate alternately depending on the alternating current voltage. (
6) α difference is the optical fiber cable, α◆ (to) is the light receiving element that converts the light transmitted by the optical fiber cable @α4 into an electrical signal, αQαη is the waveform that makes the output of the light receiving element α4)Qf9 a constant amplitude Shaping circuit (B), (G) is an AND circuit that adds the outputs of the waveform shaping circuit αΦαη, 011! AN
A conversion circuit that converts the frequency of the output of circuit D into a voltage, a polarity inversion circuit that inverts the polarity of the output of the conversion circuit Ql only during the period when there is a pulse in the output of the waveform shaping circuit αη, and Qυ the output of the waveform shaping circuit aη. During the pulse period, there is a polarity identification circuit which sends a signal to the polarity inversion circuit (e).

Next, the operation will be explained. In the figure, when high AC ground pressure is applied between a conductor (1) and a reference potential (earth potential here), a voltage is applied to electrodes (2) and (3) that are separated by a certain distance from the conductor (1). is induced. By the way, if the glL poles (2) and (3) have the same shape, the same voltage will be induced. To explain about the -e,vet pole (2) side, when the polarity of the electrode (2) is positive, the ground pressure induced in the electrode (2) is applied to both ends of the electroluminescent element (4), The electroluminescent element (4) emits electroluminescence.

This light emission is transmitted by an optical fiber cable (2) and is received by a phototransistor (8). When the phototransistor (3) receives light, the phototransistor (8) becomes conductive and the potential of the electrode (2) is reduced to approximately zero. Resistor (6) is phototransistor (8)
This is a limiting resistor for protecting the phototransistor (3) from overcurrent when it becomes conductive. Next, the electrode (
When the potential of 2) becomes zero, the electroluminescent element (4) stops emitting light, the phototransistor (8) is cut off, and a voltage is induced in the electrode (2) again. repeats the same action. Here, the conductor (
If the single pole (2) and electroluminescence 51 (4) are appropriately selected so that the number of the above-mentioned repeated blinking operations is sufficiently large with respect to the alternating current cycle of (1), the voltage of the conductor (1) can be increased. (positive polarity) will be frequency modulated. Note that this means that the voltage across the electroluminescent element (4) corresponds to the applied voltage of the conductor (<1) due to the charging time constant due to the capacitance and resistance of the electroluminescent element (4) itself. In other words, the higher the voltage applied to the conductor (1), the faster it is charged, and when a certain ground pressure is reached, the electroluminescent element (4) will emit light. ) blinks when the conductor (1
) is frequency modulated by the ground pressure. Note that when the polarity of the voltage on the conductor (1) is negative, the diode αO becomes conductive and the electroluminescent element (4) does not emit light. Tortoise fllI (3) @ Ha* The operation is similar to the pole (2) side, but when the polarity of the voltage on the conductor (1) is negative, the electroluminescent element (5) blinks.

The frequency-modulated optical signal is transmitted to a remote location via optical fiber cable (2) Q3, and is then sent to photodetector α4 (15).
is converted into an electrical signal. The converted signals are each 0
The waveform shaping circuit a00η converts the signal into a sharp pulse with a constant amplitude. Use an AND circuit for these two signals.

When added, a signal is obtained in which the ground pressure of the conductor (1) is frequency modulated in a full-wave rectified form. Convert this signal (b) path Q
1 to convert it into a voltage signal similar to that of the multi-conductor (1).

However, since the voltage of the conductor (1) is in a full-wave rectified form, the polarity of the output of the conversion circuit Ql is inverted by the polarity inverting circuit (1) during the period when the output of the waveform shaping circuit w4aη has a pulse m. do. The polarity identification circuit is, for example, composed of a low-pass filter and a waveform shaping circuit with a cutoff frequency between the frequency of the pulse group output from the waveform shaping circuit αη and the frequency of the voltage of the conductor (1), and a polarity inversion circuit. It provides a signal that inverts the polarity. Note that this embodiment shows the basic configuration, and does not include, for example, adding a Schmitt circuit to the phototransistor in order to sharpen the blinking of the electroluminescent element (4).

In the above embodiment, an electroluminescent element is used as a light emitting element that converts the voltage induced in the electrode into an optical signal, but a light emitting diode may also be used. In this case, an external capacitor and resistor are added to determine the light emission time constant.

In addition, in the above embodiment, a phototransistor is used as a light-receiving element that receives light emitted from an electroluminescent element and reduces the electrode potential to zero, but a phototransistor such as a photodiode or cadmium cell, which has a small resistance value due to light, may also be used. It is also possible to use a different element.

As mentioned above, this invention can detect the voltage of the high potential part without contact, and the voltage signal of the high potential part is frequency modulated and transmitted as optical output without using a power supply in the detection part, so it is reliable. It has high resistance to noise, is unaffected by loss in the optical transmission system, and can perform highly accurate voltage measurements.

[Brief explanation of drawings]

The figure is a configuration diagram showing an embodiment of the present invention. In the figure, (1) is a conductor (live part'), (21 (3
) is a single pole, (4) and (5) are electroluminescent elements (light emitting elements), @α3 is an optical fiber, 04αω is a light receiving element, αQα is a waveform shaping circuit, and α1 is a conversion circuit. Agent Shin Kuzuno −

Claims (1)

[Scope of Claims] (131m!) A pair of III!l provided at a predetermined distance from a live part of the device, a light emitting element connected between each electrode and a reference potential, and a light emitting element connected between each electrode and a reference potential; a first light receiving element arranged to receive light emitted from the light emitting element and electrically connected to both ends of the light emitting element; an optical fiber that receives the light emitted from the light emitting element and transmits it to a remote location; light of the optical fiber; A second light-receiving element that receives light, a waveform shaping circuit that shapes the waveform of the electrical output signal of the second light-receiving element, and a conversion circuit that converts the frequency of this waveform shaping circuit into a voltage. Measuring device. (2. In claim 1, a voltage measuring device characterized in that an electroluminescent element is used as a light emitting element. (3) In claim 1, a voltage measuring device characterized in that an electroluminescent element is used as a light emitting element. A voltage measuring device characterized by using a light emitting diode. (4) A voltage measuring device according to claim 1, characterized in that a phototransistor or a photodiode is used as the first light receiving element. (5) A voltage measuring device according to claim 1, characterized in that an element such as a cadmium cell whose resistance decreases due to light is used as the first light receiving element.