JPH0750142B2 - Power cable accident point detection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an accident point detection method for accurately detecting an accident point such as a dielectric 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. Furthermore, in other proposed methods besides the pulse-type measurement method, similarly, it is a method of detecting an accident point after an accident occurs, which is a useful method for constantly monitoring the line and detecting the accident point at the same time as the accident. 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 of the present invention is to provide a method for promptly and accurately detecting an accident point on a transmission line due to a breakage of a power cable, and its gist Is a plurality of antenna devices that are installed close to the power cable at a predetermined interval and receive electromagnetic waves due to arcs that accompany the breakdown of the power cable to generate electromotive force. While being electrically coupled to the device, respectively, a detector is provided with a forward optical fiber to which an optical pulse and an identification pulse are constantly input from one end, and a backward optical fiber provided with an optical pulse receiving means at a terminal, The electromotive force from the antenna device is transmitted, and the electromotive force optically couples the forward optical fiber and the backward optical fiber in the detector to discriminate the optical pulse from the optical pulse. The optical pulse and the identification pulse are detected by the optical pulse receiving means, the position of the dielectric breakdown point between the detectors is detected in the state of the optical pulse, and the reflection time of the identification pulse is detected. It is a method of detecting an accident point of a power cable, which is characterized by detecting the accident point by obtaining the distance to the detector.

[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 and the identification pulse that are always incident on the forward optical fiber are received by the return optical fiber terminal, and the position of the dielectric breakdown between the detectors in the state of the optical pulse is determined by the reflection time of the identification pulse. The distance to the detector is calculated and the accident point is detected from these.

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

FIG. 1 is a block diagram showing an outline of a method for detecting an accident point of a power cable according to 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 to the forward optical fiber.
21 and the return optical fiber 22 are respectively connected. A plurality of detectors 30 and antenna devices 31 are provided at appropriate intervals. The light source 5 and the pulse generator 41 are connected to one end of the outward optical fiber 21 so that the optical pulse and the identification pulse are constantly input, and the one end of the return optical fiber 22 is a pulse counter 42 which is an optical pulse receiving means and a distance display means. An arithmetic unit 6 including 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 and the identification pulse input to the outward optical fiber 21 will be transmitted to the return optical fiber 22, and the optical pulse and the identification pulse will be returned. Pulse counter 42 connected to one end of optical fiber 22
Also, the position of the dielectric breakdown point between the detectors 30 and 30 is received by the arithmetic unit 6 in the state of the waveform of the optical pulse, and the distance to the detector 30 is obtained by the reflection time of the identification pulse. Is to detect.

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

FIG. 3 is a diagram showing an example of the device of the present invention, in which the forward optical fiber 21 to which the optical pulse and the identification pulse are constantly input and the return optical fiber 22 are appropriately spaced in the laying direction of the power cable 1. The detectors 30 are installed so that they can be optically coupled to each other. In order to make it easier to receive the electromagnetic waves caused by the arc due to the dielectric breakdown, a plurality of antenna devices 31 are installed close to each other at a predetermined interval in the laying direction of the power cable 1, and between the connecting portions of the forward optical fiber 21 of the detector 30. Polarized material 301
The lead wire 32 and the electrode 303 are electrically coupled to each other. 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, electrodes 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, the optical pulse and the identification pulse in the outward optical fiber 21 do not have an electric field applied to the deflecting substance 301 in the detector 30, and therefore, in the direction of the arrow shown in the figure, according to the principle of the circuit of FIG. Going forward, the detector 30 merely serves as a connector for the outbound 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 light pulse and the identification pulse reflected by the deflecting substance 301 are further reflected by the reflecting plate 302 as shown by the arrow in the figure, enter the return optical fiber 22, and are 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.

Then, with reference to FIG.
An actual operation example for detecting the position of the dielectric breakdown point between 30 will be described. For ease of explanation, an operation will be described in the case where the length of the backward optical fiber 22 between the detectors 30 is selected to be twice the length of the forward optical fiber 21, for example. 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- marked on the power cable 1
1, BD-2, BD-3, BD-4, BD-5 indicate dielectric breakdown points a ₁ , a ₂ ,
_{b 1, b 2, c 1} , c 2 denotes the distance from the breakdown point of the BD-1, BD-2, BD-3 to the antenna device 31, 31 '. BD-2 is B
Located at the midpoint between D-1 and BD-3, BD-4 is BD-1 and BD-2, BD-5
Is located at the midpoint between BD-2 and BD-3. Since the antenna devices 31 and 31 'are actually installed close to the power cable 1, that is, they are sufficiently shorter than the length L between the detectors 30 and 30', the distance relationship is approximated as follows.

a ₁ ＝ c ₂ ≈0 a ₂ ＝ c ₂ ≈L b ₁ ＝ b ₂ ≈L / 2 That is, the above equation is supposed to mean that dielectric breakdown occurs at point BD-3 of power cable 1 and electromagnetic waves are generated. For example, BD shown
The antenna device 31 'on the -3 point wave reaches without requiring little time and light pulses propagating time and that the electromagnetic wave reaches the antenna device 31 in the path of c _1, the inside outward optical fiber 21 Is almost the same as the time it takes to propagate from the detector 30 'to the detector 30 (the optical pulse and the electromagnetic wave have the same propagation velocity).

FIG. 6 shows an example of the operation of this device when 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 30IV.
In the figure, the portions connected by dotted lines indicate 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.
The case where there are individual light pulses will be described. The arrow in the figure indicates the traveling direction of the optical pulse.

As shown in Fig. 6 (a), when dielectric breakdown occurs at the BD-1 point of the power cable 1, the electromagnetic wave generated there instantly is detected by the detector.
It is received by the antenna device of 30I (not shown), and the detector 3
The forward optical fiber 21 and the return optical fiber 22 are optically coupled in 0I. 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, the electromagnetic wave from the BD-1 point is an antenna device (not shown) of the detector 30II.
The optical fiber 21
And the return optical fiber 22 are optically coupled. 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 optical pulses a and g are just combined in the detector 30II at the same timing, and then the optical pulses b and h, c and i, The d and j are combined and transmitted through the return optical fiber 22. Light pulses d and below are reflected by the detector 30II, so the light pulses k, l ...
Will continue to be incident on the return optical fiber 22 until the emission of electromagnetic waves due to the arc due to the dielectric breakdown ends. It should be noted that each detector is provided with a certain threshold value, and the detector 30II is applied to the electromagnetic wave from the breakdown point BD-1.
I and 30IV are set not to operate. 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 optical fiber 22.

Fig. 7 shows the BD-2 point of the power cable 1, that is, the detector 30I
It shows the operation when the dielectric breakdown occurs at the point between 30 and 30II. In Figures 7 (a)-(c), BD-2
When an electromagnetic wave due to dielectric breakdown is emitted at a point, the electromagnetic wave is simultaneously received by the antenna devices 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. It will be. 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 30II.
And are respectively incident on the return optical fibers 22. Then, optical pulses a and g, b and h are sequentially combined, and then BD-2
Until the emission of the electromagnetic wave from the 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 optical pulse j passes through the detector 30II, the optical pulse group shown in FIG. 7D is transmitted to the return optical fiber 22.

Fig. 8 shows the breakdown at the BD-4 point, which is the midpoint between the breakdown points BD-1 and BD-2 shown in Fig. 5, that is, at the line length L / 4 right from BD-1. It shows the operation when it occurs. 8 (a) to 8 (c), when the electromagnetic wave radiated by the dielectric breakdown in BD-4 is radiated, the electromagnetic wave is first received by the antenna device of the detector 30I, so that the forward optical fiber 21 and the backward optical fiber are detected in the detector 30I. 22 is optically coupled. Furthermore, since the electromagnetic wave from the BD-4 point is received by the antenna device of the detector 30II before the optical pulse d reaches the detector 30II,
The optical pulse d or less is returned by the detector 30II to the return optical fiber 22.
Will be incident on. 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 breakdown at the BD-5 point, which is the midpoint between the breakdown points BD-2 and BD-3 shown in Fig. 5, that is, at the line length L / 4 left from BD-3. It shows the operation when it occurs. In FIGS. 9 (a) to 9 (c), when the electromagnetic wave radiated by the dielectric breakdown in BD-5 is radiated, the electromagnetic wave is first received by the antenna device of the detector 30II, and therefore the forward optical fiber 21 and the backward optical fiber in the detector 30II. 22 is optically coupled. That is, for the optical pulse d or less, the detector 30II uses the return optical fiber 22.
Is incident on. Further, since the electromagnetic wave from the BD-5 point is received by the antenna device of the detector 30I before the light pulse c reaches the detector 30I, the light pulse c is incident on the return optical fiber 22 by the detector 30I. (Light pulse a, b
Is not incident). Therefore, the optical pulses c and i are combined and transmitted through the return optical fiber 22, and thereafter, the optical pulse j or less continues to be incident on the return optical fiber 22 at the detector 30II until the emission of the electromagnetic wave from the BD-5 ends. . 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. 9D is transmitted to the return optical fiber 22.

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 dielectric breakdown point between the detectors 30I and 30II, detection is performed by counting the number of combined optical pulses. It is possible to know the position of the breakdown point between the vessels.

The operation detailed above is one example of the operation of the present invention, but the ratio of the optical fiber length of the return optical fiber 22 and the optical fiber length of the outward optical fiber 21 between the detectors is not limited to 2: 1 and this ratio is Arbitrary selection (same length is acceptable)
can do. In the case of this embodiment, the optical fiber length of the return optical fiber 22 between the detectors is the return optical fiber.
Since it is twice the optical fiber length of 21, the optical fiber of the return optical fiber 22 will remain slack if it is laid as it is. For example, insert the optical fiber of the outward optical fiber 21 into the core of the coaxial spacer A method of winding the optical fiber of the return optical fiber 22 around the outer periphery of the spacer to eliminate the looseness of the optical fiber is used.

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 operation principle of electromagnetic waves in the detector of the present invention, and FIG. 3 is the installation of the device used in the present invention. FIG. 4A shows an example of the state of the detector when the antenna device does not receive the electromagnetic wave, and FIG. 4B shows a state of the detector when the antenna device receives the electromagnetic wave. FIG. 5 and FIG. 9 to FIG. 9 are explanatory views for explaining the actual operation of the device used in the present invention. 1 ... Power cable, 21 ... Outgoing optical fiber, 22 ...
Return optical fiber, 30 ... Detector, 31 ... Antenna device

Claims (1)

[Claims] 1. An antenna device, which is installed close to a power cable at a predetermined interval, receives an electromagnetic wave due to an arc accompanying an insulation breakdown of the power cable to generate an electromotive force, and the plurality of antennas. While being electrically coupled to the device, respectively, a detector is provided with a forward optical fiber to which an optical pulse and an identification pulse are constantly input from one end, and a backward optical fiber provided with an optical pulse receiving means at a terminal, The electromotive force from the antenna device is transmitted, the forward optical fiber and the backward optical fiber are optically coupled in the detector by the electromotive force, and the optical pulse and the identification pulse are input to the backward optical fiber. The receiving means detects the optical pulse and the identification pulse, detects the position of the dielectric breakdown point between the detectors in the state of the optical pulse, and reflects the identification pulse. Fault point detection method of the power cable, characterized in that to detect the fault point seeking distance to the detector at between.