JPH09145770A - Accident point spotting device for transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To spot the accident point of a transmission line caused by a thunderbolt from a substation by detecting the surge current generated by the thunderbolt with a detection coil incorporated in a thunderbolt detecting sensor and impressing a detecting signal larger than a threshold upon the optical fiber of an optical fiber composite overhead ground wire after modulating the plane of polarization of the signal. SOLUTION: When a steel tower A2 provided with no thunderbolt detecting sensor 2 is struck by lightning, a surge current flows toward steel towers A1 and A5 through an optical fiber overhead ground wire 1 and a secondary current is generated in a detection coil 3 incorporated in the sensor 2 and inputted to a drive circuit 4. The circuit 4 counts 12 the detecting time of secondary current the output level of which is higher than a threshold, binarizes 14 the counted detecting time, oscillates 15 the signal carrying the information, and impresses the signal upon an optical fiber 5 in a ground wire after modulating the plane of polarization of the signal by means of an external light modulating section 6. At a substation, the distribution of the surge current in a transmission line is found upon receiving the signal and specifies the steel tower A2 struck by lightning. Therefore, even when steel towers A2 -A4 are struck by lightning, the towers can be specified with sensors 2 near the towers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line accident point locating device capable of locating an accident point such as a ground fault or a short circuit of a transmission line caused by a lightning strike at a substation.

[0002]

2. Description of the Related Art In recent years, the demand for stable supply of electric power has been increasing more and more, and therefore, high reliability is maintained even in power transmission lines. However, it is difficult to eliminate the failure of power transmission lines that are installed in a wide area and are exposed to a severe natural environment. In particular, when a lightning strike occurs, an accident such as a ground fault or a short circuit may occur, which may lead to a very serious accident such as stopping power transmission. When these accidents occur, it is desired to restore them promptly, and therefore a system for immediately locating the accident place is required.

Conventionally, for example, a system for locating an accident on a power transmission line has been shown in FIGS. 9 and 10. The accident point detection sensor F includes a CT (penetrating current transformer) B installed on a GW (ground wire) A, an amplifier C, and A / D converters D and E / O for converting current analog information into digital information. It is composed of a conversion unit E. The surge current flowing in the ground wire A when a lightning strike occurs is detected by the feedthrough current transformer B, and after A / D conversion, the E / O conversion unit E
Is transmitted as an optical signal.

The accident point detection sensor F is installed in each steel tower (usually every 3 to 4) in which a connection box for an optical fiber overhead ground wire is installed. The signals from the plurality of accident point detection sensors F are collected in the optical data multiplex transmission device G, multiplexed with the signals from the adjacent optical data multiplex transmission devices, and then sent to the substation I.

[0005]

The conventional fault locator for power transmission line has the following problems. . In order to use the optical fiber H of the optical fiber composite overhead ground wire that has already been installed, the detection sensor F can be arranged only in the steel tower where the connection box is placed. Therefore, the detection limit is the interval at which the detection sensor F is arranged, and the detection sensor F
When a lightning strike occurs on a steel tower where is not located, it is difficult to accurately locate the accident point.

[0006] In principle, it is also possible to identify the steel tower where the detection sensor F is not arranged from the signal arrival time difference at the substation side, but for that purpose it is necessary to identify the time difference of 1 μs or less, and also for signal transmission. It is actually difficult because it requires an extremely wide bandwidth.

[0007] The optical data multiplex transmission apparatus G requires an O / E for reception, a demodulator, an E / O for transmission, and a modulator, which complicates the configuration of the optical data multiplex transmission apparatus G.
There is a problem that a power supply for driving the constituent devices is required and maintenance management becomes difficult.

The object of the present invention is to obtain the surge current distribution on the transmission line caused by a lightning strike on the substation side to identify the steel tower where the lightning strike occurred, and to provide information such as ground faults and short circuits of the transmission line due to the lightning strike. Another object of the present invention is to provide an accident point locating device for a transmission line which can be transmitted by using the optical fiber in the optical fiber composite overhead ground wire, and in which the loss of the transmitted light is almost zero.

[0009]

A fault locator for a transmission line according to claim 1 of the present invention utilizes an optical fiber composite overhead ground wire 1 as shown in FIG. A ground fault caused by a lightning strike at a substation, transmitting short-circuit information.
In a transmission line accident point locator for locating an accident point such as a short circuit, a plurality of lightning strike detection sensors 2 are arranged at predetermined intervals on a transmission line formed by the optical fiber composite overhead ground wire 1, and the lightning strike detection is performed on the substation side. A current distribution detection device for determining a surge current distribution on the power transmission line based on a signal transmitted from the sensor 2 is provided, and the lightning strike detection sensor 2 detects a surge current generated by a lightning strike as shown in FIG.
And a drive circuit 4 that oscillates a signal carrying binarized information according to the length of time when a current of a level equal to or higher than a threshold value is detected, and the drive circuit 4 causes the optical fiber composite overhead wire 1
An optical external modulator 6 for applying a polarization plane modulated signal to the optical fiber 5 therein is provided.

According to the second aspect of the present invention, the transmission line fault locating device transmits the ground fault and short circuit information of the transmission line due to a lightning strike by using the optical fiber composite overhead ground wire 1 as shown in FIG. In an accident point locating device for a transmission line that locates an accident point such as a ground fault or a short circuit caused by a lightning strike at a substation, a plurality of lightning strike detection sensors 2 are arranged at predetermined intervals in a transmission line formed by the optical fiber composite overhead ground wire 1. In addition, a current distribution detection device for determining a surge current distribution on the transmission line based on a signal transmitted from the lightning strike detection sensor 2 is provided on the substation side, and the lightning strike detection sensor 2 detects a lightning strike as shown in FIG. A detection coil 3 that detects a surge current that occurs, a drive circuit 4 that oscillates a signal carrying binarized information according to a current level that is equal to or higher than a detected threshold, and an optical fiber composite aerial ground by the drive circuit 4. line Those having an optical external modulator 6 which applies a polarization modulation signal into an optical fiber 5 in.

[0011]

In the fault locator for a transmission line according to claim 1 of the present invention, the length of time (eg, L ₁ L _{2 in} FIG. 3) at which the detection coil 3 in FIG. )
2 oscillates a signal carrying binarized information from the drive circuit 4 of FIG. 2, and the optical external modulator 6 based on the signal is oscillated.
Since the polarization-modulated signal from the optical fiber is applied to the optical fiber 5 in the optical fiber composite overhead ground wire 1, even if a lightning strike occurs in a steel tower where the lightning strike detection sensor 2 is not arranged, the lightning strike detection sensor around the steel tower is detected. Information about the detection time length of the surge current detected in 2 can be received at the substation side. Therefore, the substation side can obtain the surge current distribution (for example, FIG. 4) on the transmission line, and can identify the steel tower where the lightning strike has occurred.

In this case, since the optical fiber 5 in the existing optical fiber composite overhead ground wire 1 can be used to transmit information such as a ground fault or a short circuit of the transmission line due to a lightning strike, the structure is simplified. Further, since the signal is applied to the optical fiber 5 by polarization plane modulation by the optical external modulator 6, there is almost no loss of transmitted light.

In the transmission line fault locating device according to the second aspect of the present invention, the binarized information is added from the drive circuit 4 according to the current level detected by the detection coil 3 which is equal to or higher than the threshold value. Signal is oscillated, and the polarization plane modulation signal from the optical external modulator 6 based on the signal is applied to the optical fiber 5 in the optical fiber composite overhead ground wire 1, so that the lightning strike detection sensor 2 is not installed in the tower. Even if a lightning strike occurs in the substation, the substation side can receive information about the detection time length of the surge current detected by the lightning strike detection sensor 2 around the steel tower. Therefore, the substation side can obtain the surge current distribution on the transmission line, and can identify the steel tower where the lightning strike occurred.

Also in this case, since the information such as the ground fault and the short circuit of the power transmission line due to the lightning strike is transmitted by using the optical fiber in the existing optical fiber composite overhead ground wire, it can be realized with an extremely simple structure. Further, since the signal is applied to the optical fiber 5 by the polarization plane modulation by the optical external modulator 6, there is almost no loss of transmitted light.

[0015]

First Embodiment A first embodiment of an accident point locating device for a power transmission line according to the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG. 1, a plurality of steel towers A _{1 to} A _n are provided with an optical fiber composite overhead ground wire 1, and an optical fiber connection box 7 is provided on the steel towers A ₁ and A ₅ to detect a lightning strike sensor 2. Is installed.

As shown in FIG. 2, the lightning strike detection sensor 2 detects a surge current generated by a lightning strike and a current above a preset threshold value (FIG. 3). Drive circuit 4 which oscillates a signal carrying binarized information according to the lengths of time L ₁ and L ₂ , and a polarization plane modulation signal to optical fiber 5 in optical fiber composite overhead ground wire 1 by drive circuit 4. And an external optical modulator 6 for applying

The drive circuit 4 of FIG. 2 is a current / voltage converter 1
1, a counter 12, a reference signal generator 13 for outputting a reference signal having a predetermined threshold value, a binarization circuit 14 for converting the signal into a 3-bit binarized signal, and an oscillator 15.

[0018]

[Description of Operation of First Embodiment] For example, when a lightning strike occurs in the steel tower A ₂ in FIG. 1, a surge current flows through the optical fiber overhead ground wire 1 toward the steel tower A ₁ and the steel tower A ₅ , which causes the surge current to flow.
A secondary current is generated in the detection coil 3 of. This secondary current is converted into a voltage proportional to the secondary current in the current / voltage converter 11 and output, and the output level is measured to be equal to or higher than the threshold value generated from the reference signal generator 13. The time (L ₁ and L _{2 in} FIG. 3) is counted by the counter 12. The times L ₁ and L ₂ are expressed as, for example, 3-bit binarization information in the binarization circuit 14 of FIG. 2, and a high frequency voltage is applied from the oscillator 15 to the optical external modulator 6 by carrying this information. The optical signal propagating in the optical fiber 5 (FIG. 2) in the fiber overhead ground wire 1 is polarization-modulated.

In the above case, 3-bit information can be sent by changing the oscillation time of the signal for driving the optical external modulator 6 or by modulating the carrier with a different frequency. The oscillation time and different modulation frequencies are as shown in Table 1, for example.

Further, by changing the carrier frequency for each of the two or more lightning strike detection sensors 2 in FIG. 1, the lightning strike detection sensor 2 driven by the lightning strike can be identified on the substation side. For example, in the lightning strike detection sensor 2 of the steel tower A ₁ ,
Of the surge electric wave waveform W ₁ is detected, the detection time L ₁ in the surge current waveform W ₁ is binarized with 3 bits, and the optical external modulator 6 is driven by placing it on the carrier frequency f ₁ and the tower A
The lightning strike detection sensor 2 of ₅ detects the surge current waveform W ₂ of FIG. 3 and detects the detection time L ₂ in the surge current waveform W ₂ .
Is binarized and placed on the carrier frequency f ₂ to drive the optical external modulator 6. Specifically, for example, the carrier frequency f ₁ = 170M
Hz and f ₂ = 170.4 MHz.

[0021]

[Table 1]

An example of the optical external modulator 6 of FIG. 2 is shown in FIGS. This is a thin-film lower electrode 22 and a thin-film piezoelectric body 2 on one surface 26a of a support substrate 26 made of quartz glass.
3. The upper electrode 24 is laminated in this order, and the leads 27a and 27b for introducing an electric signal for driving the piezoelectric body 23 are attached to the lower electrode 22 and the upper electrode 24, respectively.

Examples of the material of the lower electrode 22 and the upper electrode 24 include A1, Au and Cu, and examples of the material of the piezoelectric body 23 include ZnO and PVDF (polyvinylidene fluoride). Each of the lower electrode 22, the piezoelectric body 23, and the upper electrode 24 can be formed by a known film forming method such as a sputtering method, a vacuum evaporation method, or a CVD method.

A single mode optical fiber 28 (optical fiber 5 of the optical ground wire 1) is arranged directly below the piezoelectric body 23 and the upper electrode 24 on the other surface 26b (FIG. 8) of the supporting substrate 26. ing. Specifically, the support substrate 2
The other surface 26b of the optical fiber 6 and the optical fiber 28 are placed in contact with each other, and the portion of the optical fiber 28 having a desired length is placed in the fiber 2
The optical fiber 28 is fixed to the support substrate 26 by being covered with a substance 29 having a specific acoustic impedance close to that of the specific acoustic impedance of 8. The specific acoustic impedance referred to here is the product of the propagation velocity of a sound wave and the propagation medium.
Examples of the substance 29 include a substance obtained by depositing fine particles of quartz glass on the outer periphery of the optical fiber 28 and firing the fine particles to vitrify.

Specific materials, dimensions, etc. of the optical external modulator 6 are as follows, for example. Support substrate Quartz thickness 1 mm, 20 × 20 mm Lower part, upper electrode A1 thickness 0.5 μm Piezoelectric material ZnO thickness 8 μm

In this optical external modulator 6, a high frequency signal from the oscillator 25 of FIG. 2 is supplied to the lead 27 of FIG. 7 of the optical external modulator 6.
When applied through a and 27b, a periodic pressure is applied from the piezoelectric body 23 to the optical fiber 28, and this external force causes a refractive index distribution in the optical fiber 28, which causes
The plane of polarization of the light passing through 8 is modulated. The polarization-modulated light can be electrically processed by being subjected to OE conversion after being converted to intensity modulation through an analyzer on the receiving side such as a substation.

In this optical external modulator 6, since the stress is applied to the optical fiber 28 by the piezoelectric element, the power consumption of the drive circuit 4 for driving the optical external modulator 6 can be extremely small. For example, it will be possible to operate for several years using only lithium batteries. Further, it is possible to add a function of periodically oscillating to the lightning strike detection sensor 2 in order to confirm whether or not the drive circuit 6 itself is functioning normally from the surplus power of the power supply.

FIG. 4 shows an example of the surge current distribution on the transmission line obtained by using the above-mentioned accident point locating device. Thus, the steel tower A ₁₁ where the lightning strike occurred can be specified by estimating the steel tower having the maximum value.

[0029]

Embodiment 2 of the present invention will be described with reference to FIGS. 5 and 6 as a second embodiment of the fault locating device for a power transmission line according to the present invention. In this embodiment, as in FIG. 1, a large number of steel towers A _{1 to} A _n are installed with an optical fiber composite overhead ground wire ₁ , and a lightning strike detection sensor 2 is installed on the steel towers A ₁ and A ₅ provided with an optical fiber connection box. Has been done.

In the second embodiment, the lightning strike detection sensor 2 is different from the lightning strike detection sensor 2 of the first embodiment. That is, as shown in FIG. 5, the lightning strike detection sensor 2 of the second embodiment responds to a detection coil 3 for detecting a surge current caused by a lightning strike and a current level above a preset threshold value (FIG. 6). Drive circuit 4 that oscillates a signal carrying binarized information
And an optical external modulator 6 for applying a polarization plane modulation signal to the optical fiber 5 in the optical fiber composite overhead ground wire 1 by the drive circuit 4.
Is provided.

The drive circuit 4 of FIG. 2 is a current / voltage converter 1
1, a comparator 31, a reference signal generator 13 for outputting a reference signal having a predetermined threshold value, a binarization circuit 14 for converting a 3-bit binary signal, and an oscillator 15.

[0032]

[Description of Operation of Second Embodiment] For example, when a lightning strike occurs in the steel tower A ₂ in FIG. 1, a surge current flows through the optical fiber overhead ground wire 1 toward the steel tower A ₁ and the steel tower A ₅ , whereby the surge current shown in FIG. A secondary current is generated in the detection coil 3 of. The secondary current is converted into a voltage proportional to the secondary current in the current / voltage converter 11 and is output, and the output level thereof is the comparator 31.
Is compared with a threshold value (FIG. 5) generated from the reference signal generator 13, and a value equal to or higher than the threshold value is binarized.
4 is represented as, for example, 3-bit binary information,
A high-frequency voltage is applied to the optical external modulator 6 from the oscillator 15 by carrying this information, and the optical signal propagating in the optical fiber 5 (FIG. 5) in the optical fiber overhead ground wire 1 is polarization plane modulated.

Also in this case, 3-bit information can be sent by changing the oscillation time of the signal for driving the optical external modulator 6 or by modulating the carrier with a different frequency. Table 2 shows the oscillation time and the different modulation frequencies.

[0034]

[Table 2]

Also in the case of the second embodiment, as in the case of the first embodiment, by changing the carrier frequency for each of the two or more lightning strike detection sensors 2 in FIG. Can be identified on the substation side. For example, the lightning strike detection sensor 2 pylons A ₁ detects the surge wave waveform W ₁ of FIG. 6, is placed on the surge wave waveform W carrier frequency f ₁ by binarizing the detection time L ₁ in 3 bits in _first light By driving the external modulator 6, the lightning strike detection sensor 2 of the tower A ₅ detects the surge current waveform W ₂ of FIG.
Driving the optical external modulator 6 Place the detection time L ₂ in the surge wave waveform W ₂ into binary to the carrier frequency f _2. For example, carrier frequency f ₁ = 170 MHz, f ₂ = 170.4
MHz.

Optical external modulator 6 in FIG. 5 of the second embodiment
Is the same as the optical external modulator shown in FIGS.

[0037]

According to the accident point locating device for a power transmission line of claim 1 of the present invention, even if a lightning strike occurs in a steel tower where no lightning strike detection sensor is arranged, a lightning strike detection sensor arranged in a neighboring steel tower. Since information about the detection time length of the surge current detected in 2 can be received at the substation side, it is possible to identify the steel tower where the lightning strike has occurred from the surge current distribution on the transmission line.

According to the accident point locating device for a power transmission line of claim 2 of the present invention, even if a lightning strike occurs in a steel tower where no lightning strike detection sensor is arranged, the lightning strike detection sensor 2 arranged in the neighboring steel towers Since the substation side can receive the intensity information of the detected surge current, it is possible to identify the steel tower where the lightning strike occurred from the surge current distribution on the transmission line.

In any of the first and second aspects of the invention, since the optical fiber of the existing optical fiber composite overhead ground wire 1 can be used for construction, practical application is easy.

In each of the first and second aspects of the invention, since the signal is applied to the optical fiber 5 by polarization modulation by the external modulator 6, a plurality of lightning strike detection sensors 2 are inserted in the measurement system. However, the power of the light transmitted through the fiber 5 is hardly lost.

[Brief description of the drawings]

FIG. 1 is a schematic view of a steel tower portion of a transmission line accident locator according to the present invention.

FIG. 2 is a schematic diagram of a first embodiment of a lightning strike detection sensor in a transmission line accident location device of the present invention.

FIG. 3 is an explanatory diagram of a waveform of a surge current detected by the transmission line fault locating device according to claim 1 of the present invention.

FIG. 4 is an explanatory diagram of a distribution of surge current on the power transmission line analyzed on the receiving side of the fault locating device for the power transmission line according to the present invention.

FIG. 5 is a schematic diagram of a second embodiment of a lightning strike detection sensor in a transmission line accident location device of the present invention.

FIG. 6 is a waveform explanatory diagram of a surge current detected by the fault locator for a power transmission line according to claim 2 of the present invention.

FIG. 7 is a front side perspective view of an optical external modulator in the transmission line fault locating device of the present invention.

FIG. 8 is a rear side perspective view of the optical external modulator in the transmission line fault locating device of the present invention.

FIG. 9 is an explanatory diagram of a conventional accident point locating system for a power transmission line.

FIG. 10 is an explanatory diagram of another example of a conventional fault point locating system for a power transmission line.

[Explanation of symbols]

 1 Optical fiber composite overhead ground wire 2 Lightning strike detection sensor 3 Detection coil 4 Drive circuit 5 Optical fiber 6 Optical external modulator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeaki Nishikawa 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. An optical fiber composite overhead ground wire (1) is used to transmit ground fault and short circuit information of a transmission line to a substation due to a lightning strike, and the substation has an accident such as a ground fault or a short circuit based on the information. In a transmission line accident point locating device capable of locating points, a plurality of lightning strike detection sensors (2) are arranged at predetermined intervals on a transmission line formed by the optical fiber composite overhead ground wire (1), and the lightning detection sensors (2) are arranged on the substation side. A current distribution detection device for determining a surge current distribution on the power transmission line based on a signal transmitted from the lightning strike detection sensor (2) is provided, and the lightning strike detection sensor (2) detects the surge current (3)
And a drive circuit (4) that oscillates a signal carrying binarized information according to the length of time that a current of a level equal to or higher than a threshold value is detected, and an optical fiber composite aerial ground by the drive circuit (4). A fault locator for a power transmission line, comprising an optical external modulator (6) for applying a polarization plane modulated signal to an optical fiber (5) in the line (1). 2. An optical fiber composite overhead ground wire (1) is used to transmit ground fault and short circuit information of a transmission line due to lightning to a substation, and the substation has an accident such as a ground fault or a short circuit based on the information. In a transmission line accident point locating device capable of locating points, a plurality of lightning strike detection sensors (2) are arranged at predetermined intervals on a transmission line formed by the optical fiber composite overhead ground wire (1), and the lightning detection sensors (2) are arranged on the substation side. A current distribution detection device for determining a surge current distribution on the power transmission line based on a signal transmitted from the lightning strike detection sensor (2) is provided, and the lightning strike detection sensor (2) detects the surge current (3)
And a drive circuit (4) for oscillating a signal carrying binarized information according to a detected current level equal to or higher than a threshold value,
An accident point of a transmission line characterized by comprising an optical external modulator (6) for applying a polarization plane modulation signal to an optical fiber (5) in an optical fiber composite overhead ground wire (1) by a drive circuit (4) Orientation device.