JPH0789136B2 - Electric power cable accident point detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an apparatus for accurately detecting an accident point such as insulation breakdown of a power cable from a remote location.

[Prior art] In recent years, in order to respond to the increase in power demand and the efficiency of power transmission, 27
With the realization of ultra-high voltage transmission systems of 5kv and 500kv, the transmission capacity of each single transmission system has become extremely large. Therefore, if a ground fault or a short-circuit accident occurs in such a power transmission system and insulation breakdown occurs in the power cable, it is necessary to detect the accident point accurately and quickly to recover the accident in order to maintain stable power supply. Has become an extremely important responsibility.

Conventionally, a pulse-type measurement method has been mainly used as a method for detecting an accident point of a power cable due to a short circuit or a ground fault. In this method, an electric pulse is sent to the power transmission line, a reflected pulse of a certain magnitude and polarity that is reflected from the fault point of the power transmission line, that is, the change point of the characteristic impedance is received, and the reflected pulse The accident point is detected from the reflection time.

[Problems to be Solved by the Invention] However, in the above pulse-type measurement method, the pulse sent to the line is attenuated as it travels through the cable and its waveform is distorted, so that a fault point at a long distance is accurately detected. Is difficult to do.

Further, the measurement method is a method in which measurement is started and an accident point is searched after the occurrence of an accident, that is, after it is known that an abnormality has occurred in the transmission line, and the accident point cannot be found promptly. Similarly, other proposed methods besides the pulse-type measurement method are methods of detecting an accident point after an accident occurs, and are useful for detecting an accident point at the same time as an accident by observing the line at all times. The current situation is that no means has been proposed yet.

[Technical Means] The present invention has been made in view of the above circumstances, and an object thereof is to provide a device for promptly and accurately detecting an accident point of a transmission line due to breakage of a power cable. A plurality of antenna devices that are installed close to the power cable and spaced apart from each other by a predetermined interval, and that receive an electromagnetic wave due to an arc caused by insulation breakdown of the power cable to generate electromotive force, and the plurality of antenna devices. And a forward optical fiber and a backward optical fiber arranged between the detectors, and the backward optical fiber between the detectors has a length twice that of the forward optical fiber. An optical pulse is always input from one end to the forward optical fiber, and an optical pulse receiving means is provided at a terminal of the backward optical fiber, and the forward optical fiber is provided. The return optical fibers are connected to each other so that they can be optically coupled in the detector, and the optical coupling between the forward optical fiber and the return optical fiber is configured to be realized by an electromotive force from the antenna device. Is a power cable accident point detection device.

[Operation] When a dielectric breakdown occurs in the power cable, an arc is generated, and electromagnetic waves are emitted from the dielectric breakdown point. This electromagnetic wave is received by an antenna device installed close to the power cable to generate electromotive force, and only when the electromotive force is generated, that is, when an accident occurs, the forward optical fiber and the return optical fiber are used as electromotive force in the detector. The optical pulse state that is always incident on the forward optical fiber is received by the backward optical fiber terminal, and the fault point is detected in the optical pulse state.

[Examples] The present invention will be described more specifically with reference to the drawings.

FIG. 1 is a block diagram showing the outline of the present invention, in which 1 is a power cable and 31 is an antenna device installed in the vicinity of the power cable 1. The antenna device 31 is electrically coupled to the detector 30 via the lead wire 32, and the detector 30 is connected with the forward optical fiber 21 and the backward optical fiber 22 respectively. A plurality of detectors 30 and antenna devices 31 are provided at appropriate intervals. Between the detectors 30 and 30, the length of the return optical fiber 22 is
It is said to be twice the length of. The light source 5 and the pulse generator 41 are connected to one end of the outward optical fiber 21 so that optical pulses are constantly input, and the one end of the return optical fiber 22 is provided with a pulse counter 42 which is an optical pulse receiving means and a distance display means. The arithmetic unit 6 is connected.

If a dielectric breakdown occurs at a certain point of the power cable 1 and an arc is generated, electromagnetic waves are inevitably emitted at the dielectric breakdown point along with the arc. This electromagnetic wave is received by the antenna device 31 located near the insulation breakdown point and converted into electric power, and the electric power is sent to the detector 30 via the lead wire 32. The forward optical fiber 21 and the backward optical fiber 22 connected to the detector 30 are normally independent optical fiber lines, and the detector 30 merely plays the role of a connector for each line. Only when the generated power is transmitted from the antenna device 31, the forward optical fiber 21 and the backward optical fiber 22 are optically coupled. This optical coupling means will be described later. That is, if an electromagnetic wave is generated due to an arc due to the dielectric breakdown of the power cable 1, the optical pulse input to the forward optical fiber 21 is transmitted to the return optical fiber 22, and this optical pulse is connected to one end of the return optical fiber 22. The signal is received by the pulse counter 42 and the arithmetic unit 6 and the accident point is detected based on the reflection time of the optical pulse and the waveform shape.

The method for detecting an accident point of a power cable according to the present invention has been described above. Next, the apparatus will be described in detail.

FIG. 3 is a diagram showing an example of the device of the present invention, in which a forward optical fiber 21 to which an optical pulse is constantly input and a return optical fiber 22 are installed at appropriate intervals in the laying direction of the power cable 1. The detectors 30 are connected to each other in an optically connectable state. To make it easier to receive the electromagnetic waves that accompany the arc due to the dielectric breakdown,
A plurality of 31 are installed close to each other at a predetermined interval in the laying direction of the power cable 1, and are electrically connected by a lead wire 32 and an electrode 303 to the polarizing substance 301 interposed between the connecting portions of the outward optical fiber 21 of the detector 30. Are combined together. FIG. 2 shows a circuit which is the principle of the closed circuit in this portion. In the figure, a coil is wound around a magnetic material such as ferrite, electromagnetic waves are connected to both ends of the coil, and a polarizing substance is interposed between the electrodes. This polarizing substance is selected as a substance which is transparent when an electric field is not applied and allows light in the arrow direction in the figure to pass therethrough, and reflects light in the arrow direction when an electric field is applied. For example, liquid crystal is used.

FIG. 4A shows a case where the antenna device 31 does not receive an electromagnetic wave, that is, a case where the insulation state of the power cable 1 is normal. In this case, since the electric field is not applied to the deflecting substance 301 in the detector 30 in the forward optical fiber 21 in the forward optical fiber 21, it is possible to proceed in the direction of the arrow shown in the figure according to the principle of the circuit of FIG. Thus, the detector 30 merely serves as a connector for the outgoing optical fiber 21.

FIG. 4B shows a case where the antenna device 31 receives an electromagnetic wave, that is, a case where an abnormality occurs in the insulation state of the power cable 1. In this case, the antenna device 31 generates an electromotive force, and an electric field is applied to the deflecting substance 301 by the electrodes 303, 303, so that the deflecting substance 301 functions to reflect light. The optical pulse reflected by the deflecting substance 301 is further reflected by the reflecting plate 302 as shown by the arrow in the figure, enters the backward optical fiber 22, and is transmitted to the pulse counter 42 and the arithmetic unit 6. The reflection plate 302 has a function of transmitting light from the direction of arrow X in the figure but not transmitting light from the direction of arrow Y. For example, a plate or beam coated with a so-called magic mirror is used. A splitter or the like is used as long as it has the above-mentioned action.

Next, an actual operation example of the device of the present invention will be described with reference to FIG. In FIG. 5, when the optical fiber length of the outward optical fiber 21 between the detectors 30 and 30 'is L, the optical fiber length of the return optical fiber 22 is 2L.
BD-1, BD-2, BD-3, BD-4, BD- described on the power cable 1
5 indicates the dielectric breakdown point, a ₁ , a ₂ , b ₁ , b ₂ , c ₁ , c ₂ are BD-1, BD-
2, The distance from the dielectric breakdown point of BD-3 to the antenna device 31, 31 'is shown. Note that BD-2 is located at the midpoint between BD-1 and BD-3, BD-4 is BD-1 and BD-2, and BD-5 is BD-3.
It is located at the midpoint of each. Antenna device 31,3
1'is actually installed close to the power cable 1, that is, it is sufficiently shorter than the length L between the detectors 30 and 30 ', so the distance relationship is approximated by the following equation.

a ₁ ＝ c ₂ ≒ 0 a ₂ ＝ c ₁ ≒ L b ₁ ＝ b ₂ ≒ L / 2 That is, the above formula is assumed that the dielectric breakdown occurs at the BD-3 point of the power cable 1 and the electromagnetic wave is generated. If illustrated
Light antenna device 31 'on the BD-3 points wave reaches without requiring little time and propagating time and that the electromagnetic wave reaches the antenna device 31 in the path of c _1, the inside outward optical fiber 21 The time it takes for the pulse to propagate from the detector 30 'to the detector 30 is almost the same (both the optical pulse and the electromagnetic wave have the same velocity).
Has the meaning.

FIG. 6 shows an example of the operation of this device when a dielectric breakdown occurs at point BD-1 of the power cable 1 shown in FIG. 30I to 30IV are detectors, a, b, c ... are optical pulses, and the forward optical fiber 21 and the return optical fiber 22 are detectors 30I to 3
The portion connected by the dotted line in 0IV represents that the optical coupling is performed by the operation as described above. The optical pulses a, b, c ... Which are incident on the outward optical fiber 21 may be transmitted at regular intervals, but here, the case where there are two optical pulses between the respective detectors will be described. The arrow in the figure indicates the traveling direction of the optical pulse.

As shown in FIG. 6 (a), when the dielectric breakdown occurs at the BD-1 point of the power cable 1, the electromagnetic wave generated there instantly is received by the antenna device (not shown) of the detector 30I, and the detector 30I is detected. The forward optical fiber 21 and the return optical fiber 22 are optically coupled therein. That is, as shown in FIG. 6B, the optical pulses a and b are incident on the return optical fiber 22. At the same time, when the optical pulse c reaches the detector 30I, BD
The electromagnetic wave from point -1 reaches the antenna device (not shown) of the detector 30II, and the forward optical fiber 21 and the backward optical fiber 22 are optically coupled in the detector 30II. In other words, the light pulse e and the following are incident on the return optical fiber 22 by the detector 30II. As a result, as shown in FIG. 6 (c), the light pulses a and g are just detected by the detector 30.
In II, the optical pulses b and h, c and i, and d and j are multiplexed in the same way and then transmitted in the return optical fiber 22. The light pulses d and below are reflected by the detector 30II, and thereafter, the light pulses k, l ... Continue to be incident on the return optical fiber 22 until the emission of electromagnetic waves by the arc due to the dielectric breakdown ends in order. It should be noted that each of the detectors is provided with a certain threshold, and the detectors 30III and 30IV are set so as not to operate with respect to the electromagnetic wave from the breakdown point BD-1. If the emission of the electromagnetic wave ends when the optical pulse 1 passes through the detector 30II, the optical pulse group shown in FIG. 6D is transmitted to the return path optical fiber 22.

FIG. 7 shows the BD-2 point of the power cable 1, that is, the detector 30.
It shows the operation when a dielectric breakdown occurs at a point that is midway between I and 30II. 7 (a) to (c), BD
-When the electromagnetic wave due to the dielectric breakdown is radiated at two points, the electromagnetic wave is simultaneously received by the antenna device of the detectors 30I and 30II, and the forward optical fiber 21 and the backward optical fiber 22 are optically coupled in the respective detectors 30I and 30II. Will be done. That is, the light pulses a and b are detected by the detector 30I, and the light pulses c and below are detected by the detector 30I.
The light is incident on the return optical fibers 22 at 30II. Then, optical pulses a and g, b and h are sequentially combined, and then
Until the emission of the electromagnetic wave from the BD-2 point ends, the light pulse i or less continues to be incident on the return optical fiber 22 at the detector 30II. If the emission of the electromagnetic wave ends when the light pulse j passes through the detector 30II, the return optical fiber 22
The optical pulse group shown in FIG. 7D is transmitted to.

FIG. 8 shows the line length from BD-1 which is the midpoint between the breakdown points BD-1 and BD-2 shown in FIG.
It shows the operation when dielectric breakdown occurs at the point on the right of L / 4. In FIGS. 8 (a) to 8 (c), when an electromagnetic wave due to dielectric breakdown is radiated by BD-4, the electromagnetic wave is first detected by the detector 30I.
The forward optical fiber 21 and the backward optical fiber 22 are optically coupled in the detector 30I. Furthermore, before the optical pulse d reaches the detector 30II, BD
Since the electromagnetic wave from the −4 point is received by the antenna device of the detector 30II, the light pulse d or less is incident on the backward optical fiber 22 by the detector 30II. Therefore, the optical pulses a and g, b and h, and c and i are sequentially multiplexed and transmitted through the return optical fiber 22, and thereafter the optical pulse j or less is returned by the detector 30II until the emission of the electromagnetic wave from the BD-4 ends. It will continue to enter the optical fiber 22. If the emission of the electromagnetic wave ends when the light pulse k passes through the detector 30II, the optical pulse group shown in FIG. 8 (d) is transmitted to the return path optical fiber 22.

Fig. 9 shows the line length from BD-5, which is the midpoint between the breakdown points BD-2 and BD-3 shown in Fig. 5, that is, BD-3.
It shows the operation when dielectric breakdown occurs at the point on the left of L / 4. 9 (a) to 9 (c), when an electromagnetic wave due to insulation breakdown is radiated by BD-5, the electromagnetic wave is first detected by the detector 30II.
The optical fiber 21 and the return optical fiber 22 are optically coupled in the detector 30II. That is, the light pulse d or less is incident on the return optical fiber 22 by the detector 30II. Further, the optical pulse c is detected by the detector 30.
Since the electromagnetic wave from the BD-5 point is received by the antenna device of the detector 30I before reaching I, the optical pulse c is detected by the detector 30I.
Therefore, it is incident on the return optical fiber 22 (the optical pulses a and b are not incident). Therefore, the optical pulses c and i are combined and transmitted through the return optical fiber 22, and then BD-5
The optical pulse j or less will continue to be incident on the return optical fiber 22 at the detector 30II until the emission of the electromagnetic wave from the above is finished. If the emission of the electromagnetic wave ends when the optical pulse k passes through the detector 30II, the return path optical fiber 22 has
The optical pulse group shown in FIG. 3D is transmitted.

That is, FIG. 6 (d), FIG. 7 (d), FIG. 8 (d),
As can be seen from FIG. 9 (d), since the number of optical pulses combined varies depending on the position of the insulation breakdown point between the detectors 30I and 30II, insulation is performed by counting the number of combined optical pulses. You can know the position of the breaking point.

Further, in the case of this embodiment, since the optical fiber length of the return optical fiber 22 between the detectors is twice as long as the optical fiber length of the outward optical fiber 21, the optical fiber of the return optical fiber 22 remains slack if actually laid as it is. Therefore, for example, a method is used in which the optical fiber of the outward optical fiber 21 is inserted into the core of the coaxial spacer and the optical fiber of the return optical fiber 22 is wound around the outer periphery of the spacer to eliminate the looseness of the optical fiber.

Although the present embodiment has described the case where there are two optical pulses between the detectors of the outward optical fiber 21, this is not limited to the present embodiment either, and the number of optical pulses can be increased to increase the number of detectors. It is possible to improve the position detection accuracy of the dielectric breakdown point between the two. That is, when the number of light pulses is two, the position detection accuracy of the dielectric breakdown point between the detectors is limited to detecting the four positions described with reference to FIGS. 6 to 9, but by increasing the number of light pulses, it becomes more detailed. The position of the dielectric breakdown point can be detected.

The position of the dielectric breakdown point between the detectors can be detected by the above-mentioned optical pulse, but the distance from the measurement site to the dielectric breakdown point of the power cable 1 is different from that of another optical pulse with an interval between the optical pulses. It is possible to measure by adding a discrimination pulse). That is, the reflection time of this identification pulse is measured by the arithmetic unit 6 and the pulse counter 42, which are optical pulse receiving means at the terminal of the return optical fiber 22, and the detector closest to the dielectric breakdown point from the optical pulse sending side (first 6 to 9, the distance to the detector 30II) is obtained, and the position from the detector to the dielectric breakdown point is detected by counting the number of combined optical pulses. The distance to the dielectric breakdown point is detected.

[Effect] According to the present invention, the dielectric breakdown point is detected by receiving an electromagnetic wave due to an arc, which is inevitably generated by the dielectric breakdown of the power cable, by the antenna device installed close to the power cable. Therefore, the power cable line is constantly monitored, and the accident point can be detected promptly after the accident. Further, since the device of the present invention is configured by the optical fiber, the influence of the attenuation of the optical pulse which is the detection signal of the accident occurrence and the external noise is extremely small, and the accident point can be detected accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the outline of the accident point detection method of the present invention, FIG. 2 is a circuit diagram showing the operating principle of electromagnetic waves in the detector of the present invention, and FIG. FIG. 4A is a diagram showing a state of the detector when the antenna device does not receive the electromagnetic wave, and FIG. 4B is a diagram showing a state of the detector when the antenna device receives the electromagnetic wave. 5 to 9 are explanatory views for explaining the actual operation of the device of the present invention. 1 ... Power cable, 21 ... Outgoing optical fiber, 22 ...
Return optical fiber, 30 ... Detector, 31 ... Antenna device

Claims (2)

[Claims] 1. A device for detecting an accident point such as a dielectric breakdown of a power cable, wherein a plurality of devices are installed close to the power cable at a predetermined interval and electromagnetic waves generated by an arc caused by the dielectric breakdown of the power cable. An antenna device for receiving an electromotive force, a detector electrically coupled to each of the plurality of antenna devices, a forward optical fiber and a return optical fiber disposed between the detectors, Between the detectors, the return optical fiber has a length that is twice the length of the forward optical fiber, the optical pulse is always input to the forward optical fiber from one end, and the optical pulse receiving means is provided at the terminal of the return optical fiber. The forward optical path and the return optical fiber are connected to each other so that they can be optically coupled in the detector. Optical coupling, the fault point detection system for a power cable, characterized by comprising a such is realized by the electromotive force configuration from the antenna device with. 2. The detector is internally provided with a polarizing substance that causes an optical change due to an electromotive force from an antenna device, and the forward optical fiber and the return optical fiber are coupled only when the polarizing substance optically changes. The accident point detection device for a power cable according to claim (1).