JPH03105261A - Signal processing circuit for optical zero-phase current-voltage sensor - Google Patents

Abstract

PURPOSE:To detect a fault existing for a long period by sampling a zero-phase value by CPU at a frequency containing an error of a commercial frequency when the fault occurring in an arbitrary phase is discriminated on the basis of a change in a current value or a voltage value of each phase of a three-phase alternating current. CONSTITUTION:A sensor signal processing circuit is constructed of three optical fiber sensor 1, 2 and 3 each detecting a current or a voltage of each phase of a three-phase alternating current of which the phases shift at 120 deg. from each other, three LEDs 4, 5 and 6 supplying light to the sensors, three driving amplifiers 7, 8 and 9 for driving these LEDs, three light-sensing diodes 10, 11 and 12 sensing the light from the optical fiber sensors, three light-sensing amplifiers 13, 14 and 15 amplifying signals of these diodes, an A/D converter 16 digitizing signals inputted from these amplifiers, CPU 17 for an arithmetic processing, and a comparator 18 making a trigger generated when an arbitrary phase crosses zero. By constructing the circuit in this way, an apparent zero phase is removed and a true zero is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an optical zero-sequence current system that determines an accident that has occurred in any phase based on changes in the instantaneous sum of current values or voltage values of each phase of a three-phase alternating current. The present invention relates to a voltage sensor signal processing circuit.

BACKGROUND ART FIG. 4 shows a circuit configuration diagram of a conventional example. This conventional example uses three LEDs that supply light to optical fiber sensors 1, 2.3.
4, 5.6, and three drive amplifiers 7 that drive them.
8.9 and 3 which receives the optical signal from the optical fiber sensor.
three light-receiving diodes 10, 11.12 and three light-receiving amplifiers 13, 1 for amplifying the signals of these light-receiving diodes.
4.15, an A/D converter 16 that digitizes the signals amplified by these light receiving amplifiers, a CPU 17 that processes these digital signals, a clock generator 19 based on the commercial frequency, and an optical system zero. It constitutes a phase current voltage sensor signal processing circuit.

In this conventional example, the frequency of three-phase alternating current is the commercial frequency 50
Assuming that r-{ z or 60 f{ z is fixed, a conversion trigger is applied to the A/D converter 16, and the CPU 17 detects the current value or voltage value of each phase. The light reception signals from the optical fiber sensors 1, 2.3 are not necessarily zero at the three-phase f port due to variations in sensitivity between the sensors and the influence of multiple layers. For this reason, in this conventional example, as shown in Fig. 5, the zero phase is determined using the waveform of one cycle before the clock generator 19 as a reference frequency, and an accident that occurs in any phase due to a change in this zero phase is detected. I am trying to determine.

That is, in this conventional example, the zero-phase value, which is the instantaneous three-phase sum of the light reception signals from the optical fiber sensors 1, 2, and 3, has an apparent Since zero-sequence values appear, in order to remove these apparent zero-sequence values and detect the true zero-sequence value due to an accident that occurred in an arbitrary phase, the zero-sequence value of one cycle before is removed as shown in Figure 5. Using this value as a reference synchronization, the CPU 17 calculates and processes the difference from the sample point data at the same position. In order to detect a fault occurring in any phase, according to the algorithm shown in Figure 6, when the true zero-sequence voltage exceeds a threshold, the reference period for calculating the true zero-sequence value is set to the pre-fault period. Fixed to one cycle. This is due to an accident occurring in any phase as shown in Figure 5.
If we take the period in which the true zero-phase value changes as the reference period,
This is done to prevent the zero-phase value from becoming zero again from the next cycle onward, making it impossible to detect an accident.

Problem to be Solved by the Invention However, when the zero-sequence voltage exceeds the threshold value and the zero-sequence current does not exceed the threshold value, as shown in FIG. .3 to 3, the time difference between the 3 manual detection cycles becomes large.

In addition, the sample point data of the zero phase value is generated by the clock generator 19.
Therefore, since the commercial frequency is fixed at 50 Hz or 60 Hz, the true frequency of the reference period includes a sample point shift due to the error frequency of the commercial frequency. Therefore, the larger the time difference between the reference period and the period detected and compared by the CPU 17, the more the error is accumulated, and as shown in FIG. Regardless, the threshold is detected to be exceeded due to an error, resulting in an erroneous detection of an accident. In order to prevent this, in this conventional example, fault detection is stopped before the accumulated error exceeds the threshold, but as a result, the zero-sequence voltage exceeds the fault detection threshold, and the zero-sequence current is If the threshold is not exceeded, there is a problem that accident detection cannot be performed for a long time.

Means for Solving the Problems A first aspect of the present invention includes three optical fiber sensors that detect the current or voltage of each phase of three-phase alternating current whose phase is shifted by 120 degrees, and these optical fiber sensors. 3 supplying light to
three LEDs, three drive amplifiers that drive these LEDs, three light receiving diodes that receive optical signals from the three optical fiber sensors, and three that amplify the signals of these light receiving diodes. and an A/D that digitizes the signals amplified by these three light receiving amplifiers.
a converter, a CPU for processing the digital signal, and means for detecting the frequency of the three-phase alternating current every cycle;
It consists of means for applying a conversion trigger to the A/D converter in synchronization with the detected period, and samples the optical signal value from the optical fiber sensor read by the CPU without being affected by fluctuations in the three-phase AC frequency. It is characterized by being configured as follows.

Further, in a second aspect of the present invention, the CPU calculates and detects fluctuations in the three-phase AC frequency from specific range data of three-phase AC current values or voltage values detected from the three optical fiber sensors, and By making the timing at which the conversion trigger is applied to the A/D converter proportional to the calculation result, the optical signal value from the optical fiber sensor read by the CPU is sampled without being affected by fluctuations in the three-phase AC frequency. It is characterized by

Furthermore, the third invention of the present invention is characterized in that the CPU calculates and detects fluctuations in the three-phase AC frequency based on specific range data of three-phase AC current values or voltage values detected from the three optical fiber sensors; By increasing or decreasing the timing at which the conversion trigger is applied to the A/D converter by the minimum unit of the sample clock depending on the increase or decrease of the calculation result, the optical signal value from the optical fiber sensor read by the CPU can be adjusted to the fluctuation of the three-phase AC frequency. It is characterized by being configured so that it can be sampled without being influenced.

According to the first aspect of the present invention, since the CPU samples the zero-sequence value at a frequency that includes an error of the commercial frequency,
Since the reference period does not include deviations due to errors in the commercial frequency, faults can be detected over a long period of time even when the zero-sequence voltage exceeds the fault detection threshold but the zero-sequence current does not exceed the fault detection threshold.

According to the second aspect of the present invention, the frequency including errors in the commercial frequency is detected by fluctuations in the voltage value or current value from the sensor, and the CPU samples the zero-phase value.
Since the reference period does not include deviations due to errors in the commercial frequency, faults can be detected over a long period of time even when the zero-sequence voltage exceeds the fault detection threshold but the zero-sequence current does not exceed the fault detection threshold.

According to the third aspect of the present invention, the frequency including the commercial frequency error is detected by the fluctuation of the voltage value or current value from the sensor, and the frequency error is detected regardless of the accuracy of the sampled data. Since the CPU samples the zero-sequence value at a frequency that minimizes the deviation, the reference period does not include the error deviation of the commercial frequency, so the zero-sequence voltage exceeds the fault detection threshold and the zero-sequence current Even if the detection threshold is not exceeded, accident detection can be performed for a long period of time.

Embodiment FIG. 1 shows a circuit block diagram in a first embodiment of the present invention. The optical zero-phase current/voltage sensor signal processing circuit of this embodiment includes three optical fibers 1.2.3 that detect the current or voltage of each phase of a three-phase alternating current whose phase is shifted by 120 degrees, and Three LEDs 4.5.6 that supply light to the optical fiber sensors 1 and 2.3, and three drive amplifiers that drive these LEDs 4.5.6? , 8.9, three light receiving diodes 10, 11.12 that receive optical signals from the optical fiber sensor 1.2.3, and three light receiving diodes 10, 11.12 that amplify the signals of these light receiving diodes 10, 11.12. Receiving amplifier 1
3, 14. 15, an A/D converter 16 that digitizes the signals input from these, a CPU 17 that processes the digitized signal values, and an arbitrary phase of the frequency of the three-phase alternating current that is zero. The comparator 18 generates a trigger when crossed, and the output from the comparator l8 is connected to C.
The CPU 17 applies a 12-point conversion trigger to the A/D converter 16 for each output pulse of the comparator 18, as shown in FIG. 8, for example.

According to this embodiment, as shown in FIG. 8, in order to remove the apparent zero phase and detect the true zero phase, the difference between the reference period and the sample point at the same position of the period being detected is calculated. In this case, it is possible to remove the error included in the difference between the sample points at the same position due to the commercial frequency including an error.

Therefore, even if the time difference between the reference period and the period under detection is large, the accumulation of the above-mentioned errors is eliminated, so that accident detection can be carried out over a long period of time.

FIG. 2 shows a circuit block diagram in a second embodiment of the present invention. The optical zero-phase current/voltage sensor signal processing circuit of this embodiment has a configuration in which the comparator 18 is removed from the first embodiment, and the CPU 17 performs The three-phase AC frequency is determined, and conversion triggers at 12 points are applied to the A/D converter 16 in proportion to this frequency, as shown in FIG. 9, for example.

According to this embodiment, as shown in FIG. 9, the data values a, b, which cross zero every three cycles of the zero-phase value, which is the instantaneous sum of three phases of current values or voltage values manually inputted to the CPU 17, ,,a
4, b Find the average frequency for three periods from the slope of the four points. Then, in proportion to this frequency, the A/D converter ■6
Apply the conversion trigger to .

With this method, as in the first embodiment, even if the time difference between the reference period and the period under detection is large, the accumulation of the above-mentioned errors is eliminated, so that accident detection can be carried out over a long period of time.

FIG. 3 shows a circuit block diagram in a third embodiment of the present invention. The optical zero-phase current/voltage sensor signal processing circuit of this embodiment is constructed by using an A/D converter 16 having a relatively lower resolution than that of the second embodiment. Yes, the CPU 17 calculates the average frequency of the three-phase AC using the same method as in the second embodiment. And this frequency is the first
As shown in FIG. 0, if the average frequency is higher than the average frequency found in the previous three cycles, it is decreased by the minimum count clock value of the CPU 17. If the average frequency is small, it is increased by the minimum count clock value. Based on the count clock value determined by these determinations, the
/A conversion trigger is applied to the D converter 16.

With this method, the frequency determined by the relatively low-order A/D converter 16 is used, and as in the second embodiment, even when the time difference between the reference period and the period under detection is large, the above-mentioned error is detected. Accidents can be detected over a long period of time.

Effects of the Invention Since the present invention has the above configuration and operation, it is possible to detect an accident over a long period of time when the zero-sequence voltage exceeds the fault detection threshold and the zero-sequence current does not exceed the fault detection threshold.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram showing a first embodiment of the present invention, Fig. 2 is a circuit block diagram showing a second embodiment of the invention, and Fig. 3 is a circuit block diagram showing a second embodiment of the present invention.
Fig. 4 is a circuit block diagram showing the third embodiment of the present invention, Fig. 4 is a circuit block diagram showing the conventional example, Fig. 5 is a waveform diagram for detecting an accident in the conventional example, and Fig. 6 is an accident discrimination in the conventional example. A flowchart showing an outline, FIG. 7 is a waveform diagram for misjudging accident detection in the conventional example, FIG. 8 is a waveform diagram for detecting an accident according to the first embodiment of the present invention, and FIG. 9 is a waveform diagram for detecting an accident according to the first embodiment of the present invention. FIG. 10 is a waveform diagram for detecting an accident according to a third embodiment of the present invention. 1.2.3...Optical fiber sensor, 4.5.6
...LED, 7,8.9...Drive amplifier, 10.1112...Light receiving diode, 13
, 14.1 5... Light receiving amplifier, 1 6... A/D converter, 1st Figure 1 7... CPU, 1 8... Comparator .

Claims (3)

[Claims] (1) Three optical fiber sensors that detect the current or voltage of each phase of three-phase alternating current whose phase is shifted by 120 degrees, three LEDs that supply light to these optical fiber sensors, and Three drive amplifiers that drive the LEDs, three light receiving diodes that receive optical signals from the three optical fiber sensors, three light receiving amplifiers that amplify the signals of these light receiving diodes, and these three. an A/D converter that digitizes the signal amplified by the light-receiving amplifier; a CPU that processes the digital signal; a means for detecting the frequency of the three-phase alternating current every cycle; The device comprises means for applying a conversion trigger to the A/D converter in synchronization with the A/D converter, and is configured to sample the optical signal value from the optical fiber sensor read by the CPU without being affected by fluctuations in the three-phase AC frequency. An optical zero-phase current/voltage sensor signal processing circuit characterized by: (2) Three optical fiber sensors that detect the current or voltage of each phase of three-phase alternating current with a phase shift of 120 degrees, three LEDs that supply light to these optical fiber sensors, and Three drive amplifiers that drive the LEDs, three light receiving diodes that receive optical signals from the three optical fiber sensors, three light receiving amplifiers that amplify the signals of these light receiving diodes, and these three. It consists of an A/D converter that digitizes the signal amplified by the three light-receiving amplifiers, and a CPU that processes this digital signal.
The CPU calculates and detects fluctuations in the three-phase AC frequency from specific range data of the three-phase AC current value or voltage value detected from the optical fiber sensors, and calculates the timing to apply a conversion trigger to the A/D converter. An optical zero-phase current/voltage sensor characterized in that it is configured to sample an optical signal value from an optical fiber sensor read by a CPU without being affected by fluctuations in three-phase AC frequency by making it proportional to the result. signal processing circuit. (3) Three optical fiber sensors that detect the current or voltage of each phase of three-phase alternating current whose phase is shifted by 120 degrees, three LEDs that supply light to these optical fiber sensors, and Three drive amplifiers that drive the LEDs, three light receiving diodes that receive optical signals from the three optical fiber sensors, three light receiving amplifiers that amplify the signals of these light receiving diodes, and these three. It consists of an A/D converter that digitizes the signal amplified by the three light-receiving amplifiers, and a CPU that processes this digital signal.
The CPU calculates and detects fluctuations in the three-phase AC frequency from specific range data of the three-phase AC current value or voltage value detected from the optical fiber sensors, and calculates the timing to apply a conversion trigger to the A/D converter. Due to the increase or decrease in results,
An optical method characterized in that the optical signal value from the optical fiber sensor read by the CPU is sampled without being affected by fluctuations in the three-phase AC frequency by increasing or decreasing only the minimum unit of the sample clock. Zero-phase current and voltage sensor signal processing circuit.