JPS6279373A - Faulty section discriminator for transmission line - Google Patents

Abstract

PURPOSE:To detect a faulty section surely, by a method wherein a magnetic field-light conversion means is provided at both ends of a section with a fixed transmission line and the light being converted is converted to electricity and applied to an exclusive OR circuit through a high amplification factor circuit to compare the integrated value of the OR outputs with a reference voltage. CONSTITUTION:Optical magnetic field sensors 2a and 2b are set at both end points A and B of a section L with a fixed transmission line and the sensor outputs are transmitted to signal processing circuits 4a and 4b with optical fiber cables 3a and 3b with two cores. The circuits 4a and 4b convert an optical signal into an electrical signal to be transmitted to a discriminator circuit 5. The signal transmitted to the circuit 5 is shaped in the waveform through amplifiers 6a and 6b of a high amplification factor to be introduced to an exclusive OR circuit 7. After integrated with an integrator 8, the OR output is inputted into a comparator 9 to be compared with a fixed reference voltage. This enables accurate decision on the presence of a grounding fault and the faulty section.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a power transmission line section discrimination device.

[Conventional technology]

An example of a pipeline aerial power transmission line (hereinafter referred to as GIL)! /;explain. The GIL is constructed by holding a center conductor and a metal sheath with an insulating spacer, and filling an area between the center conductor and the metal sheath with an insulating gas, such as SFe gas.

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

In such a GIL, a ground fault may occur even though a sufficient withstand voltage t1) is established, and countermeasures against this are required.

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

The conventional method for this type of countermeasure is to install current transformers (hereinafter referred to as CT) at both ends of a defined section, and to
There is a device that detects the fault point using the signal current from the T.

[Problem that the invention seeks to solve]

However, in this method using CT, the signal processing circuit that detects and judges signals from the CT and the CTCT are exposed and attached to the high-voltage line, so contact between the CT and the high-voltage line and physical destruction of the CT may occur. Misjudgment may occur. Another drawback was that the shape of the CT was large.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned method using two CTs, and to provide an accident section discriminating device that has a simple configuration and does not cause erroneous judgments.

[Means for solving problems]

In summary, this invention replaces two CTs, installs magnetic field detection sensors at both ends of a predetermined GIL section, and transmits the signals from these two magnetic field detection sensors through optical fibers. The signal is transmitted to a conversion circuit, and based on the signal from this conversion circuit, a determination circuit including an exclusive OR circuit determines the presence or absence of a ground fault and the fault section.

The objects and structural features of the present invention will become clearer from the detailed description given below with reference to the drawings.

[Embodiments of the invention]

FIG. 1(5) is a configuration diagram of an accident section discriminating device using an optical magnetic field sensor, which is an embodiment of the present invention. 1st
In Figure (4), the interval of GILl is monitored. Optical magnetic field sensors 2 are installed at both end points A and B of the section, respectively.
a and 2b are installed.

The optical output corresponding to the sheath current derived by both magnetic field sensors 2a and 2b is transmitted to signal processing circuits 4a and 4b through Z-core optical fiber cables 3a and 3b, respectively. The signal processing circuits 4a and 4b convert the optical signals transmitted through the optical cables 3a and 3b, respectively, into electrical signals corresponding to the optical signals, and transmit the electric signals to the discrimination circuit 5. The determination circuit 5 determines the presence or absence of a ground fault and the ground fault section based on the transmitted signal.

FIG. 1(B) is a block diagram of the configuration of the discrimination circuit 5 of FIG. 1(A). The discrimination circuit 5 includes an amplifier 6 that shapes and amplifies the signal input from points A and B into a square wave.
a, 6b, and an exclusive OR circuit 7 for the signals derived from the amplifiers 6a, 6b. This exclusive OR circuit 7
The output signal is integrated by an integrator 8 and applied to a comparator 9 for comparison with a constant reference potential. If the input signal thereof is higher than a certain reference potential, the comparator 9 provides a logic level signal of ``High'' to the AND circuit 10. A
The ND circuit 10 inputs the signal from the comparator 9 and a signal obtained by inverting the signal of the relay circuit 30, which becomes conductive at the time of a ground fault and one side of which is grounded, by an inverting circuit 31.

Based on the signal from the AND circuit 10, a display circuit 12 displays the presence or absence of a ground fault and the ground fault section.

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

FIG. 2 is a diagram showing the basic operating principle of a magnetic field sensor. Linearly polarized light having a constant polarization direction A is applied to a Faraday element 13 made of, for example, a BSO single crystal. A magnetic field H is applied to this Faraday element 13 in parallel to the traveling direction of the 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. Therefore, the transmitted light of this Faraday element 13 becomes linearly polarized light in the vibration direction B. The strength of the magnetic field is H, and the length of the Faraday element 18 is l.

If the Verdet constant is Ve, then the rotation angle y is 0=Ve −
H-6...It is represented by (1).

FIG. 3 is a structural diagram of a magnetic field sensor that utilizes this Faraday rotation. The magnetic field sensor 2 uses a BSO single crystal as the Faraday element 13. This Faraday element 13 has a dielectric multilayer reflective film 14 except for the incident light side and the transmitted light side.
covered with A polarizer 15 is installed on the incident light side of the Faraday element 13 to convert the incident light into linearly polarized light. Further, on the transmitted light side, an analyzer 16 whose optical axis forms an angle of 45° with the polarizer 15 is installed. An optical rotator 17 is placed between the analyzer 16 and the Faraday element 13, which rotates the optical axis of transmitted light by a certain angle.

The transmittance T (intensity ratio of transmitted light and incident light) of this sensor 2 is T = (1+ sin 2 i ) / 2- f2
It is represented by 1. 2 Under the condition of summer << 1, equation (2)
is T=(1+2g)/2 (3). Here, when the magnetic field H is an alternating magnetic field expressed by H6sinωt, the transmittance T is calculated from equations (1) and (3), T= (
1+2Ve −Ho sin ωt −1))
/2. Therefore, by determining the ratio (modulation depth) of the DC component and AC component of the transmitted light, the magnetic field strength HO can be determined.

FIG. 4 is a basic configuration diagram of a magnetic field sensor circuit that uses the magnetic field sensor 2 described above to determine the magnitude of the applied magnetic field H. Fourth
In the figure, a constant potential signal is applied from a signal processing circuit 18 to a 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 provides an electrical signal responsive to this transmitted light to the signal processing circuit 18. The signal processing circuit 18 controls the voltage applied to the light emitting diode 19 so that the DC component of this electric signal becomes a predetermined value, and instead of calculating the ratio of the DC component to the AC component, the magnetic field sensor 2 is calculated from only the AC component. It outputs an electrical signal according to the magnitude and frequency of H applied to it.

This 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, a change in the strength Ha of the magnetic field H corresponds to a 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, by detecting and determining the signal derived by the signal processing circuit 18, it is possible to detect a change in the magnitude of the sheath current.

Figure 5 shows points A and B at all times (when no ground fault occurs), at ground faults within the section, and at ground faults outside the section.
2 is a diagram listing the current waveforms and the output signal waveforms of the signal processing circuits 4a and 4b.

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

First, when a ground fault occurs, the relay circuit 30 becomes conductive. This first determines whether an accident has occurred.

Next, we will discuss how to determine the area of a ground fault.

When a ground fault occurs within the section, the output waveforms of the signal processing circuits 4a and 4b differ in phase by 180 degrees from each other, as shown in FIG. This signal is shaped into a pulse shape and amplified by amplifiers 6a and 6b. This amplified signal is subjected to an exclusive OR operation by an exclusive OR circuit 7. Therefore, the output of the exclusive OR circuit 7 becomes a wide pulse signal with a high output level. Integrator 8 performs an integration operation only when its input is at a positive level. Therefore, as shown in FIG. 6, the output signal waveform of the integrator 8 is a triangular wave at this time, and a portion of its output level exceeds the reference setting value of the comparator 9. Therefore, the display circuit 12 uses a signal from the AND circuit 10, which inputs the output signal of the comparator 9 and the signal from the relay circuit 30, to display an accident using a light emitting diode (LED) and a buzzer (BZ).

On the other hand, when the ground fault is outside the section, the inputs to the differential amplifier 7 are almost in phase, as shown in FIG. Therefore, at this time, the output signal from the exclusive OR circuit 7 remains unchanged no matter how high the level of the human input signal is.

At this time, since the circuits subsequent to the exclusive OR circuit 7 derive the same signals as usual except for the signal from the relay circuit 30, no ground fault indication appears. Due to this,
It is determined that the ground fault occurred outside the section.

Although it is possible to detect transmission line accident sections in this way,
If there is a failure in the signal processing circuit 4a+4b determination circuit 5 and an accident occurs in interval 0, the accident interval cannot be detected.

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

Normally sample and hold circuits 21a, 21b and 0S
The control signal 25 of C24 is kept low, and the sample hold circuit 21a.

21b operates as a Ga in OdB amplifier, and 0
The output of SC24 is maintained at OV. Therefore LED1
A current (usually direct current) flows through the LEDs 9a and 19b in accordance with the respective current control signal levels.

On the other hand, when performing a failure self-diagnosis of the device, the control signal 25 is set to High, and the LEDs 19a are turned on in the sample and hold circuits 21a and 21b.

The current control signal of each LED 19b is held, and a commercial frequency signal is output at 05C24. Therefore, the output of the differential amplifier 22a is output from the sample hold circuit 21.
It is the value obtained by adding the output of 05C24 to the inverted output of a.

On the other hand, the output of the differential amplifier 22b becomes a value obtained by subtracting the output of 05C24 from the inverted output of the sample hold circuit 21b by the inverting amplifier 23. In this way, LED19a
, and a current having a DC component with a phase difference of 180° flows through the LED 19b. At this time, outputs corresponding to the currents of the LEDs 19a and 19b are obtained from the PD 20a and the FD 20b, respectively, that is, outputs similar to those in the area fault. It becomes possible to self-diagnose equipment failures.

In addition, although the magnetic field induced by the sheath current of the conduit aerial power transmission line was detected in the above example, the same effect can be obtained in other power transmission lines if the magnetic field induced by the conductor current is detected. It will be done.

〔Effect of the invention〕

As described above, in this invention, an optical magnetic field sensor is used in place of the CT of the conventional CT system, and an amplifier with a large amplification degree is installed immediately before the input section of the exclusive OR circuit to determine the section of the ground fault. The output signal provided by the exclusive OR circuit is integrated by an integrator and compared with a reference potential by a comparator.

Therefore, the device configuration is small and simple, and the integrator connected after the exclusive OR circuit makes it possible to misjudge even if the signal from the signal processing circuit contains a slight phase difference or a slight DC component. Not only is it possible to reliably determine the presence or absence of a ground fault and the ground fault section, but also it is possible to self-diagnose the failure of the device.

[Brief explanation of drawings]

FIG. 1(4) is a block diagram of an accident section discriminating device which is an embodiment of the present invention. FIG. 1(B) is a block circuit diagram of the configuration of the discrimination device shown in FIG. Figure 2 is similar to Figure 1 (A
) is a diagram showing the principle of an optical magnetic field sensor. Figure 3 shows the (14) landscaping of the optical magnetic field sensor in Figure 1 (A). Figure 4 is the magnetic field sensor circuit diagram. Figure 5 shows the current at points A and H in Figure 1 (3). 6 is a diagram showing waveforms and output signal waveforms of the signal processing circuit. FIG. 6 is a diagram showing the waveforms of FIG. 1 (
It is a figure which shows the output waveform of the differential amplifier and integrator of B). FIG. 7 is a block diagram of the signal processing circuit of the present invention. In the figure, 1 is GILX 2, 2a, 2b are optical magnetic field sensors, 4a, 4b are signal processing circuits, 5 is a discrimination circuit,
6a and 6b are amplifiers, 7 is an exclusive OR circuit, 8 is an integrator, 9 is a comparator, IO is an AND circuit, and 30 is a relay circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. 1st sub (A) 2nd Henka 3 Figure 4 Figure 6

Claims (5)

[Claims] (1) A magnetic field-to-light conversion means installed at each end of a defined section of a power transmission line and converting a magnetic field induced by a current flowing through the power transmission line into an optical signal, and a magnetic field-to-light conversion means an optical-to-electrical conversion signal that converts the signal from the optical-to-electrical conversion means into an electrical signal; two amplification means having a high amplification degree that shapes the signal from the optical-to-electrical conversion means into a pulse shape and amplifies the signal; circuit means for obtaining an exclusive OR of the signal derived by the amplifying means; integrating means for integrating the signal derived by the exclusive OR circuit; and comparing the signal derived by the integrating means with a constant reference potential. An accident section determination device for a power transmission line, comprising a comparison means. (2) a means for detecting a ground fault; and a means for indicating, in response to the output of the ground fault detection means and the output of the comparison means, that the point of the ground fault is within or outside the predetermined section. The fault section determination device for a power transmission line according to claim 1, further comprising means. (3) The fault section determination device for a power transmission line according to claim 1 or 2, wherein the magnetic field-light conversion means is an optical magnetic field sensor that utilizes the Faraday effect. (4) A magnetic field-light conversion means installed at each end of a defined section of a power transmission line and converting a magnetic field induced by a current flowing through the power transmission line into an optical signal, and a magnetic field-light conversion means an optical-to-electrical conversion signal that converts the signal from the optical-to-electrical conversion means into an electrical signal; two amplification means having a high amplification degree that shapes the signal from the optical-to-electrical conversion means into a pulse shape and amplifies the signal; circuit means for obtaining an exclusive OR of the signal derived by the amplifying means; integrating means for integrating the signal derived by the exclusive OR circuit; and comparing the signal derived by the integrating means with a constant reference potential. An accident section determination device for a power transmission line, comprising a comparison means and a failure self-diagnosis means for detecting the presence or absence of a failure in a device corresponding to each of the above-mentioned means. (5) The self-diagnosis means is means for supplying commercial frequency light having different phases to optical magnetic field sensors installed at both ends of the predetermined section, respectively. Accident section detection device for power transmission lines.