JPH0616065B2 - Accident section identification device for power lines - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transmission line section discriminating apparatus.

[Conventional technology]

A pipeline air transmission line (hereinafter, referred to as GIL) will be described as an example. The GIL is configured by holding an insulating spacer between the central conductor and the metallic sheath, and filling an insulating gas, for example SF ₆ gas, in the section formed by the central conductor and the metallic sheath.

Since such a GIL is used in a sheath solid bond, a sheath current of approximately the same size as the conductor current flows in the sheath in the opposite direction.

In such a GIL, a ground fault may occur even though a sufficient withstand voltage structure is taken, and a countermeasure against this may be necessary.

Therefore, when a ground fault occurs, it is necessary to monitor whether a ground fault occurs in a predetermined GIL section or a ground fault occurs outside the section connected to this GIL section.

As a conventional method of this type of countermeasure, a current transformer (hereinafter referred to as CT) is installed at each end of a predetermined section, and this C
There is a device that detects an accident point by a signal current from T.

[Problems to be solved by the invention]

However, in the method using this CT, the distance between the signal processing circuit that detects and determines the signal from the CT and the CT is long, and the signal lead wire is an electric wire, so noise may be picked up in the middle of the process. Since the CT is exposed and attached to the high-voltage line, an erroneous determination may occur due to contact between the CT and the high-voltage line or physical destruction of the CT. Also, CT
It also had the drawback of being large in shape.

[Object of the Invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the method using two CTs, and to provide an accident section determination device having a simple structure and free from erroneous determination.

[Means for solving problems]

In summary, the present invention is changed to two CTs, a magnetic field detection sensor is installed at each end of a predetermined GIL section, and signals from the two magnetic field detection sensors are optically-electrically transmitted by an optical fiber. The determination circuit, which transmits the signal to the conversion circuit and includes the exclusive OR circuit, determines the presence / absence of a ground fault and the fault section by a signal from the conversion circuit.

Objects and structural features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

Example of Invention

FIG. 1 (A) is a configuration diagram of an accident section discriminating apparatus using an optical magnetic field sensor, which is an embodiment of the present invention. Fig. 1
In (A), the section L of GILI is monitored. Section L
Optical magnetic field sensors 2a and 2b are installed at both end points A and B, respectively. The optical outputs corresponding to the sheath currents derived by the magnetic field sensors 2a and 2b are transmitted to the signal processing circuits 4a and 4b by the two-fiber optical fiber cables 3a and 3b. The signal processing circuits 4a and 4b are the optical cable 3
The optical signals respectively transmitted by a and 3b are converted into electric signals corresponding to the optical signals and transmitted to the discrimination circuit 5. The determination circuit 5 determines the presence or absence of a ground fault and the ground fault section on the basis of the transmitted signal.

FIG. 1 (B) is a configuration block circuit diagram of the discrimination circuit 5 of FIG. 1 (A). Discrimination circuit 5 has amplifiers 6a, 6 for shaping the signal input from points A and B into a square wave and amplifying it.
b and the exclusive OR circuit 7 of the signals derived by the amplifiers 6a and 6b. The output signal from the exclusive OR circuit 7 is integrated by the integrator 8 and given to the comparator 9 for comparison with a constant reference potential. When the input signal of the comparator 9 is higher than the constant reference potential, the comparator 9 outputs "Hi"
The AND circuit 10 supplies the signal of gh ".
Inputs the signal from the comparator 9 and the signal obtained by inverting the signal of the relay circuit 30 which is in a conductive state at the time of the ground fault and whose one is grounded by the inverting circuit 31. The display circuit 12 displays the presence / absence of a ground fault and the ground fault section in response to a signal from the AND circuit 10.

First, an optical magnetic field sensor applied to the present invention will be described.

FIG. 2 is a diagram showing the basic operation principle of the magnetic field sensor. Linearly polarized light having a constant polarization direction A is given to the Faraday element 13 made of, for example, a BSO single crystal. A magnetic field H is applied to the Faraday element 13 in parallel with the traveling direction of incident light. When the incident light passes through the Faraday element 13, Faraday rotation occurs, and the vibration direction A of the incident light is rotated by a certain angle φ. Therefore, the transmitted light of the Faraday element 13 becomes linearly polarized light in the vibration direction B. When the magnetic field strength is H, the length of the Faraday element 13 is 1, and the Verdet constant is Ve, the rotation angle φ is represented by φ = Ve · H · l (1).

FIG. 3 is a structural diagram of a magnetic field sensor utilizing this Faraday rotation. The magnetic field sensor 2 uses a BSO single crystal as the Faraday element 13. The Faraday element 13 has a dielectric multilayer reflection film 14 except for the incident light side and the transmitted light side.
Covered with. On the incident light side of the Faraday element 13, a polarizer 15 that converts the incident light into linearly polarized light is installed. On the transmitted light side, an analyzer 16 whose optical axis forms an angle of 45 ° with the polarizer 15 is installed. Between the analyzer 16 and the Faraday element 13, an optical rotator 17 for rotating the optical axis of the transmitted light by a certain angle is attached.

The transmittance T (intensity ratio of transmitted light and incident light) of the sensor 2 is expressed by T = (1 + sin2φ) / 2 (2). Under the condition of 2φ << 1, formula (2) becomes T = (1 + 2φ) / 2 (3). Here, when the magnetic field H is an alternating magnetic field represented by H ₀ sin ωt, the transmittance T is T = (1 + 2Ve · H ₀ sin ωt · l) / 2 from the equations (1) and (3). Therefore, by obtaining the ratio (modulation depth) of the DC component and the AC component of the transmitted light, the magnetic field strength H ₀
Can be asked.

FIG. 4 is a basic configuration diagram of a magnetic field sensor circuit that obtains the magnitude of the applied magnetic field H using the magnetic field sensor 2 described above. Fourth
In the figure, a constant potential signal is applied from the signal processing circuit 18 to the light emitting diode 19. In response to this signal, the light emitting diode 19 makes an optical signal of a constant intensity enter the magnetic field sensor 2 through the optical fiber cable 3. The transmitted light of the magnetic field sensor 2 is transmitted to the photodiode 20 through the optical fiber cable 3. The photodiode 20 gives an electric signal in response to the transmitted light to the signal processing circuit 18. In the signal processing circuit 18, the voltage applied to the light emitting diode 19 is controlled so that the direct current component of the electric signal becomes a predetermined value, and instead of obtaining the ratio of the direct current component and the alternating current component, the magnetic field sensor 2 is used. H applied to
The electric signal according to the magnitude and the frequency of is output.

The applied magnetic field H is induced by the sheath current.
Therefore, since the strength of the magnetic field H is proportional to the magnitude of the sheath current, the change in the strength H ₀ of the magnetic field H corresponds to the change in the sheath current. That is, the level of the voltage signal derived by the signal processing circuit 18 corresponds to the magnitude of the sheath current. Therefore, it is possible to detect the change in the magnitude of the sheath current by detecting and determining the signal derived by the signal processing circuit 18.

FIG. 5 shows points A and B at all times (when a ground fault does not occur), a ground fault inside the section L, and a ground fault outside the section L.
FIG. 4 is a list of current waveforms and output signal waveforms of signal processing circuits 4a and 4b in FIG.

FIG. 6 is a diagram showing output signal waveforms of the exclusive OR circuit 7 and the integrator 8 in the ground fault at all times and in the section L. The operation of the discriminating circuit 5 will be described below with reference to FIG. 1 (B), FIG. 5 and FIG.

First, when a ground fault occurs, the relay circuit 30 becomes conductive. As a result, the presence or absence of an accident is first determined.

Next, the ground fault section discrimination will be described.

When there is a ground fault in the section L, the output waveforms of the signal processing circuits 4a and 4b are 180 ° out of phase with each other, as shown in FIG. This signal is pulse-shaped and amplified by the amplifiers 6a and 6b. The exclusive OR circuit 7 obtains an exclusive OR of the amplified signals. Therefore, the output of the exclusive OR circuit 7 is a wide pulse signal having a high output level. The integrator 8 performs the integrating operation only when its input is at a positive level. Therefore, the sixth
As shown in the figure, at this time, the output signal waveform of the integrator 8 is a triangular wave, and a part of its output level is the comparator 9
The standard setting value of is exceeded. Therefore, the display circuit 12 displays an accident by the light emitting diode (LED) and the buzzer (BZ) by the signal from the AND circuit 10 which inputs the output signal of the comparator 9 and the signal from the relay circuit 30.

On the other hand, when the ground fault is outside the section L, the phases of the inputs to the differential amplifier 7 are almost uniform as shown in FIG. Therefore, at this time, the output signal from the exclusive OR circuit 7 does not change from the normal state, no matter how high the level of the input signal is.
At this time, the circuit subsequent to the exclusive-OR circuit 7 derives the same signal as the signal except for the signal from the relay circuit 30, so that the ground fault is not displayed. By this,
It is determined that the ground fault has occurred outside the section L.

In this way, it is possible to detect a power line accident section,
When an accident occurs in the section L when the signal processing circuits 4a and 4b determination circuit 5 has a failure, the failure section cannot be detected.

FIG. 7 shows an embodiment of the present invention, in which the signal processing circuit 4a,
4b, the failure diagnosis of the determination circuit 5 is made possible.

Sample hold circuits 21a and 21b and OS
The control signal 25 of C24 is kept low, the sample and hold circuits 21a and 21b operate as a Gain 0 dB amplifier, and the output of the OSC 24 is kept at 0V.
Therefore, a current (usually a direct current) according to each current control signal level flows through the LEDs 19a and 19b.

On the other hand, when the device self-diagnosis is performed, the control signal 25 is set to High and the sample and hold circuits 21a and 2a
1b holds the current control signals of the LEDs 19a and 19b, respectively, and the OSC 24 outputs a signal of the commercial frequency. Therefore, the output of the differential amplifier 22a has a value obtained by adding the output of the OSC 24 to the inverted output of the sample hold circuit 21a. On the other hand, the output of the differential amplifier 22b becomes a value obtained by subtracting the output of the OSC 24 from the inverted output of the sample hold circuit 21b by the inverting amplifier 23. In this way, a current having a DC component with a phase difference of 180 ° flows through the LEDs 19a and 19b. At this time, PD
20a and PD20b have LED19a and LED, respectively.
An output corresponding to the 19b current, that is, an output similar to the accident in the section L is obtained. The device self-diagnosis becomes possible.

Although the magnetic field induced by the sheath current of the pipeline air transmission line was detected in the above example, if the magnetic field induced by the conductor current is the detection target, the same effect can be obtained in other transmission lines. To be

〔The invention's effect〕

As described above, according to the present invention, an optical magnetic field sensor is used in place of the conventional CT CT, and an amplifier having a large amplification degree is used as the ground fault section determination immediately before the input section of the exclusive OR circuit. Is connected in series with the output signal of the exclusive OR circuit and is integrated by the integrator and compared with the reference potential by the comparator. Therefore, even if the signal from the signal processing circuit has a small phase difference and a slight DC component due to the small and simple device configuration and the integrator connected to the subsequent stage of the exclusive OR circuit, a misjudgment is made. In addition to being able to reliably determine the presence or absence of a ground fault and the determination of a ground fault section, it is also possible to perform a self-diagnosis of a device failure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (A) is a configuration diagram of an accident segment discriminating apparatus according to an embodiment of the present invention. FIG. 1 (B) is a block circuit diagram of the configuration of the discrimination device of FIG. 1 (A). FIG. 2 is a diagram showing the principle of the optical magnetic field sensor of FIG. Figure 3 is Figure 1
It is a structure diagram of an optical magnetic field sensor of (A). FIG. 4 is a magnetic field sensor circuit diagram. Figure 5 shows points A and B in Figure 1 (A).
3 is a diagram showing a current waveform in FIG. 4 and an output signal waveform of a signal processing circuit. FIG. 6 is a diagram showing output waveforms of the differential amplifier and the integrator of FIG. 1 (B) at the time of normal operation and at the time of communication within the section L. FIG. 7 is a block diagram of the signal processing circuit of the present invention. In the figure, 1 is a GIL, 2, 2a and 2b are optical magnetic field sensors, 4a and 4b are signal processing circuits, 5 is a discrimination circuit, and 6
a and 6b are amplifiers, 7 is an exclusive OR circuit, 8 is an integrator, 9 is a comparator, 10 is an AND circuit, and 30 is a relay circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Front page continued (72) Inventor Takuji Hara 1-3-3 Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Electric Industries, Ltd. Osaka Works (56) Reference JP-A-60-131475 (JP, A) Japanese Patent Publication Flat 3-67231 (JP, B2)

Claims (5)

[Claims] 1. A magnetic field-optical conversion means that is installed at each end of a defined section of a power transmission line and that converts a magnetic field induced by a current flowing through the power transmission line into an optical signal, and the magnetic field-optical conversion. An opto-electrical conversion signal for converting the signal from the means into an electric signal, and two amplifying means having a high amplification degree for shaping the signal from the opto-electrical converting means in a pulse shape and amplifying it. Circuit means for obtaining an exclusive OR of the signals derived by the two amplifying means, integrating means for integrating the signal derived by the exclusive OR circuit, and a signal derived by the integrating means with a constant reference potential. A transmission line accident section determination device including a comparison means for comparing. 2. A ground fault detection unit, and the ground fault point is inside or outside the predetermined section in response to the output of the ground fault detection unit and the output of the comparison unit. The transmission line accident section determination device according to claim 1, further comprising: 3. The magnetic field-light conversion means is an optical magnetic field sensor utilizing the Faraday effect.
The transmission line accident section determination device according to item 2 or item 2. 4. A magnetic field-optical conversion means which is installed at each end of a defined section of the power transmission line and which converts a magnetic field induced by a current flowing through the power transmission line into an optical signal, and the magnetic field-optical conversion. An opto-electrical conversion signal for converting the signal from the means into an electric signal, and two amplifying means having a high amplification degree for shaping the signal from the opto-electrical converting means in a pulse shape and amplifying it. Circuit means for obtaining an exclusive OR of the signals derived by the two amplifying means, integrating means for integrating the signal derived by the exclusive OR circuit, and a signal derived by the integrating means with a constant reference potential. An accident section discriminating device for a power transmission line, which comprises a comparing means for comparing and a fault self-diagnosing means for detecting the presence or absence of a failure of the device corresponding to each of the above means. 5. The self-diagnosis means is means for supplying light of commercial frequencies having different phases to optical magnetic field sensors installed at both ends of the determined section. The transmission line accident section detection device described in.