JP2019124629A - Detector detecting insulation state of power transmission line - Google Patents

Abstract

To provide an insulation state detector that can detect potential insulation defects of a power transmission line early by a simple configuration.SOLUTION: An insulation state detector 10 for a power transmission line according to the present invention includes: a magnetism sensor 11 including a magnetic resistance element, the sensor detecting a change of magnetism generated when a partial discharge including a corona discharge is generated from an insulation-coated power transmission line; and a first filter 13 for removing a frequency band including a characteristic frequency component caused by the partial discharge from the magnetic sensor 11.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an insulation state detection device for detecting a sign of insulation failure of a transmission line.

  Transmission lines may have local insulation failure. There are various causes of poor insulation, such as deterioration of the connection between the power transmission line and the transmission line, deterioration of the insulator such as cross-linked polyethylene, etc. However, various methods have been proposed for early detection of insulation failure. .

  A method of monitoring partial discharges including corona discharge is known as one of methods for early detection of insulation failure of a transmission line. For example, Patent Documents 1 and 2 describe a method of detecting insulation failure at an early stage by detecting a traveling wave generated due to a corona discharge generated in a portion where the insulation performance of the power transmission path is lowered. . A sensor for traveling wave detection has an annular core surrounding a power transmission line, and a first winding and a second winding wound around the annular core, both ends of the first winding being short-circuited, The isolated state of the power transfer path is detected by detecting the signal accompanying the passage of the traveling wave from both ends of the winding.

  Further, in Patent Document 3, an antenna for detecting corona discharge is mounted on a helicopter, and while flying by the helicopter, the antenna is received by an antenna from radio transmission lines and equipment thereof that are generated due to abnormal corona discharge by using the antenna. A method is described for searching for anomalies in overhead transmission lines and their equipment.

Unexamined-Japanese-Patent No. 1-217271 Unexamined-Japanese-Patent No. 1-221680 JP-A-3-237372

  However, in the conventional detection methods described in Patent Documents 1 and 2, it is difficult to install a large number of sensors along the transmission line because the annular core that constitutes the sensors is very expensive. Therefore, in order to specifically identify the insulation failure location, it is necessary to conduct the inspection while attaching and detaching the sensor and changing the installation position on the power transmission line, but the annular core is large and heavy, and Because the mounting work of the is difficult, it takes a lot of labor and time. The detection method described in Patent Document 3 is not suitable for inspection of a transmission line as a public infrastructure because the entire apparatus including the antenna is large, and application to underground transmission lines is also difficult.

  Therefore, an object of the present invention is to provide an insulation state detection device capable of early detecting potential insulation failure of a transmission line with a simple configuration.

  In order to solve the above-mentioned problems, the insulation state detection device for a power transmission line according to the present invention includes a magnetic resistance element, and detects a magnetic change generated when a partial discharge including corona discharge occurs from an insulation coated transmission line. A sensor and a first filter for extracting a frequency band including a characteristic frequency component of the partial discharge from an output signal of the magnetic sensor.

  According to the present invention, the magnetic sensor detects the magnetic change around the transmission line caused by the partial discharge generated at the insulation failure point of the transmission line, so cost reduction of the device can be achieved and installation of the device is easy. It is. In addition, since the first filter for extracting the frequency component caused by the partial discharge from the output signal of the magnetic sensor is provided, the influence of noise caused by the current flowing through the transmission line can be eliminated, and the sign of insulation failure of the transmission line Can be detected early.

  In the present invention, the magnetic sensor is attached to a part of the outer periphery of the power transmission line or a joint portion of the power transmission line, and detects a magnetic change around the power transmission line that occurs when the partial discharge occurs. Even if it is attached to a part of the outer periphery of the grounding wire for grounding the insulating coating part or joint part of the power transmission line, even if it detects the magnetic change around the grounding wire which occurs when the partial discharge occurs. Good. Thereby, a sign of insulation failure of the transmission line can be detected.

  Preferably, the insulation state detection device according to the present invention further comprises a second filter for extracting a frequency band including a commercial frequency component from an output signal of the magnetic sensor. In this case, the first filter is a band pass filter or a high pass filter that passes characteristic frequency components due to the partial discharge, and the second filter is a low pass filter that passes the commercial frequency components. preferable. According to this configuration, it is possible to simultaneously monitor the sign of insulation failure of the transmission line and the commercial current, and to improve the functionality of the insulation state detection device.

  The magnetic sensor preferably includes a Wheatstone bridge circuit of four magnetoresistive elements. According to this configuration, it is possible to offset the voltage drop due to parasitic resistance and improve the sensitivity. In addition, since the direction of each of the four magnetoresistive elements is set so that the detection sensitivity of the magnetism generated around the power transmission line is maximized, a minute magnetic change can be detected with high sensitivity.

  Preferably, the insulation state detection device according to the present invention further comprises an instrumentation amplifier for amplifying an output signal of the magnetic sensor. According to this configuration, a minute output signal from the magnetic sensor can be received with high impedance and reliably amplified in a wide band.

  The insulation state detection device according to the present invention includes a peak hold circuit that holds a peak level of the output signal filtered by the first filter for a certain period of time, and a comparator that compares the output signal whose peak level is held with a threshold. It is preferable to further include an alarm unit that outputs an alarm signal when the output signal is larger than a threshold. According to this configuration, it is possible to determine and notify the presence or absence of a sign of insulation failure of the transmission line.

  In the present invention, preferably, the alarm unit includes a wireless communication unit that wirelessly transmits the alarm signal. According to this configuration, the management server can easily collect alarm signals from the plurality of insulation state detection devices installed at substantially equal intervals along the power transmission line, thereby identifying insulation failure points on the power transmission line. can do.

  According to the present invention, it is possible to provide an insulation state detection device capable of early detection of potential insulation failure of a power transmission line with a simple configuration.

FIG. 1 is a schematic view of the configuration of a transmission line insulation state detection system according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the insulation state detection device according to the first embodiment of the present invention. FIG. 3 is a circuit diagram showing the configuration of the insulation state detection device of FIG. 2 (excluding the alarm unit). FIG. 4 is a block diagram showing the configuration of the insulation state detection device according to the second embodiment of the present invention. FIG. 5 is a circuit diagram showing the configuration of the insulation state detection device of FIG. 4 (excluding the alarm unit). FIG. 6 is a schematic view showing another example of the method of attaching the insulation state detection device. FIG. 7 is a block diagram showing the configuration of the insulation state detection device according to the third embodiment of the present invention. FIG. 8 is a circuit diagram showing a configuration of the insulation state detection device of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of the configuration of a transmission line insulation state detection system according to an embodiment of the present invention.

  As shown in FIG. 1, the insulation state detection system 1 includes a plurality of insulation state detection devices 10 (10A to 10D) attached to the outer peripheral surface of the power transmission line 2 and a plurality of insulation state detection devices 10 (10A to 10D) And a management server 5 connected to the relay station 3 via a communication network 4 such as the Internet. The plurality of insulation state detection devices 10 are disposed along the power transmission line 2 at substantially equal intervals. Since the detection result of the insulation state of the power transmission line 2 by the insulation state detection device 10 is transferred to the management server 5 via the relay station 3, the management server 5 facilitates information on insulation defects from the plurality of insulation state detection devices 10 Can be collected. Also, when the insulation state detection device 10 can not communicate wirelessly to the relay station 3 due to the distance or the communication state, it also enables multi-hop routing for transmitting information of the insulation state detection device 10 like a bucket brigade. .

  The power transmission line 2 is, for example, a underground power transmission line, and includes a core 2 a and an insulation coating 2 b. Although the insulation state of the core wire 2a is maintained by being surrounded by the insulation covering portion 2b, local discharge of the insulation covering portion 2b causes partial discharge such as corona discharge from the power transmission line 2. When the partial discharge occurs at the insulation failure point X, the insulation state detection devices 10C and 10D close to the insulation failure point X detect a magnetic change around the power transmission line 2 caused by the partial discharge, so the insulation state detection device 10C And 10D, it can be determined that there is an insulation failure point X. As described above, in order to identify the insulation failure point, detection must be performed at a plurality of points on the power transmission line 2. In the case where the detection operation is performed while replacing the current sensor using the annular core as in the prior art. Work efficiency is very bad. However, partial discharge can be easily detected by always providing the insulation state detection devices 10 at equal intervals along the power transmission line 2 as in the present embodiment.

  FIG. 2 is a block diagram showing the configuration of the insulation state detection device according to the first embodiment of the present invention. Moreover, FIG. 3 is a circuit diagram which shows a structure (except the alarm part 16) of the insulation state detection apparatus of FIG.

  As shown in FIGS. 2 and 3, the insulation state detection device 10 includes a magnetic sensor 11, an instrumentation amplifier 12, a filter 13, a peak hold circuit 14, a comparator 15, and an alarm unit 16. A wireless communication unit 16a is included. These components of the insulation state detection device 10 are housed in a very small package of, for example, about 10 × 10 mm, and attached to the outer peripheral surface of the power transmission line 2 (the surface of the insulation coating 2 b). The means for supplying power to the insulation state detection device 10 is not particularly limited, and may be a combination of an environmental battery and a secondary battery, or may be a primary battery.

  The magnetic sensor 11 is configured using a magnetoresistive element whose resistance value changes according to magnetism. In the present embodiment, since the magnetic sensor 11 is configured using a Wheatstone bridge circuit of four magnetoresistive elements M1 to M4, the sensitivity can be improved by canceling the voltage drop due to parasitic resistance. Also, since each of the four magnetoresistive elements M1 to M4 is installed in the direction in which the detection sensitivity of the magnetism generated around the transmission line 2 is maximized, it is possible to detect minute magnetic changes with high sensitivity. is there.

  An output signal of the magnetic sensor 11 is input to the instrumentation amplifier 12. Unlike a common operational amplifier, the input impedance of the in-amp 12 is very high, so it is possible to receive a minute output signal from the magnetic sensor 11 with high impedance and reliably amplify in a wide band.

  The filter 13 is a band pass filter (BPF) and passes a frequency band including characteristic frequency components caused by partial discharge and blocks the other bands. This makes it possible to eliminate the influence of noise such as commercial frequency (50 Hz or 60 Hz) generated by the current flowing through the transmission line 2 and signals other than the purpose, and to improve the detection accuracy of the sign of insulation failure.

  It is known that the frequency band of partial discharge including corona discharge is a band of several MHz to 1 GHz or more. However, among the partial discharges generated inside the epoxy resin of the cross-linked polyethylene used for the insulation coating portion 2b of the actual transmission line cable, the frequency component of the partial discharge accompanied with the electrical tree progress leading to the accident is 200 to 450 MHz. Also, the frequency component of the partial discharge generated in the insulating oil is considered to be prominent at around 150 MHz. Therefore, the frequency passband of the band pass filter needs to be determined in consideration of the type of partial discharge and the material of the insulating covering portion 2b.

  The peak hold circuit 14 holds the peak level of the filtered output signal for a certain period of time. The peak signal is compared with the threshold by the comparator 15, and if it is larger than the threshold, a detection signal is output. The alarm unit 16 to which the detection signal is input outputs an alarm by light, sound or the like. Further, preferably, the alarm unit 16 includes a wireless communication unit 16a that transmits an alarm signal wirelessly. In this case, as shown in FIG. 1, the wirelessly transmitted alarm signal is transmitted to the management server 5 via the relay station 3.

  When the power transmission line 2 is a high-voltage power transmission line of three-phase alternating current, a large number of power transmission lines 2 in which three are combined are wired together. At this time, it is preferable that the plurality of insulation state detection devices 10 attached to the individual power transmission lines 2 be installed at substantially the same position in the wiring direction of each power transmission line. Moreover, the insulation state detection apparatus 10 may detect not only the partial discharge of the power transmission line 2 to which itself is attached, but also the partial discharge from the adjacent power transmission line 2. That is, the insulation state detection device 10 common to a plurality of power transmission lines 2 may be used.

  Further, the wireless communication unit 16 a of the alarm unit 16 may be provided as a common external device for the plurality of insulation state detection devices 10. Alternatively, the entire alarm unit 16 may be provided as a common external device to the plurality of insulation state detection devices 10. By preparing the wireless communication unit 16 a or the alarm unit 16 common to the plurality of insulation state detection devices 10, the miniaturization and cost reduction of each insulation state detection device 10 can be achieved.

  FIG. 4 is a block diagram showing the configuration of the insulation state detection device 10 according to the second embodiment of the present invention. FIG. 5 is a circuit diagram showing the configuration of the insulation state detection device 10 of FIG. 4 (excluding the alarm unit 16).

  As shown in FIGS. 4 and 5, the feature of the insulation state detection device 10 is that the filter 13 is a high pass filter (HPF), and passes a frequency band higher than the characteristic frequency component caused by the partial discharge, The point is to block a low frequency band lower than the frequency pass band. Even with such a configuration, the influence of noise such as commercial frequency (50 Hz or 60 Hz) generated by the current flowing through the transmission line 2 or signals other than the purpose can be eliminated, and detection accuracy of the sign of insulation failure is enhanced. be able to.

  FIGS. 6A and 6B are schematic views showing another example of the installation method of the insulation state detection device 10.

  As shown to Fig.6 (a), the insulation state detection apparatus 10 may be attached not to power transmission line itself but to joint part 2C of power transmission line 2A, 2B. Moreover, as shown in FIG.6 (b), the insulation state detection apparatus 10 may be attached to the ground wire 6 extended from the joint part 2C of power transmission line 2A, 2B. Generally, a long power transmission line is configured by connecting short power transmission lines, a joint 2C connecting ends of two power transmission lines is protected by an insulating cover (connection box), and the insulating cover is grounded. It is grounded via line 6. By the insulation state detection apparatus 10 being attached to such a joint part 2C or the ground wire 6, the insulation failure of the power transmission line 2 can be detected indirectly.

  As described above, the insulation state detection device 10 according to the present embodiment has the magnetic sensor 11 that detects the magnetic change generated by the partial discharge of the transmission line 2 and the frequency characteristic of the partial discharge from the output signal of the magnetic sensor 11 And a filter 13 for extracting the component, and an alarm is output when the peak level of the filtered output signal is larger than the threshold, so that partial discharge from the transmission line 2 can be detected. Can be detected early.

  FIG. 7 is a block diagram showing the configuration of the insulation state detection device according to the third embodiment of the present invention. FIG. 8 is a circuit diagram showing a configuration of the insulation state detection device of FIG.

  As shown in FIGS. 7 and 8, the feature of the insulation state detection device 10 is that the device further includes a filter 13B (second filter) and a buffer 18B that constitute a commercial current detection unit. Further, a buffer 18A is provided at the subsequent stage of the filter 13A (first filter) for extracting frequency components due to partial discharge from the output signal of the magnetic sensor 11, and the peak hold circuit 14, the comparator 15 and the alarm unit 16 are omitted. It is done. The other configuration is the same as that of the first embodiment.

  The filter 13B is a low pass filter that passes a low frequency band including a commercial frequency and blocks a higher frequency band. The buffer 18B outputs a detection signal caused by the commercial current. As described above, a band pass filter (or high pass filter) can be used as the filter 13A.

  It is preferable that the insulation state detection apparatus 10 by this embodiment is attached to the outer peripheral surface of the power transmission line 2 or its vicinity. When it is attached to the joint portion 2C of the power transmission line 2 or the ground line 6, the commercial current detection unit can not be operated properly.

  The buffer 18A outputs a detection signal caused by the partial discharge. When it is determined based on the output signal of the buffer 18A whether or not partial discharge is generated, the peak hold circuit 14 is compared with the rear stage of the buffer 18A (or the filter 13A) as in the first embodiment. The device 15 and the alarm unit 16 may be provided in order. Furthermore, a determination circuit for determining whether or not the commercial current normally flows also in the commercial current detection unit may be provided at the rear stage of the buffer 18B (or the filter 13B).

  A conventional magnetic sensor using an annular core has frequency characteristics determined by the material of the core, and can not have wide-band frequency characteristics. However, in the case of a magnetic sensor using a magnetoresistive element as in the present invention, since its frequency band is several GHz or more, it is possible to take out any band from a wide frequency band. The configuration is feasible.

  As described above, since the insulation state detection device 10 according to the present embodiment further includes the commercial current detection unit including the filter 13B, not only the partial discharge but also the commercial electric current amount from the output signal of the magnetic sensor 11 It can be detected. That is, the sign of insulation failure of the transmission line 2 and the commercial current can be simultaneously monitored, and the functionality of the insulation state detection device 10 can be improved.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. It is needless to say that they are included in the scope.

  For example, in the above embodiment, the magnetic sensor 11 is configured using four magnetoresistive elements M1 to M4, but the number of magnetoresistive elements is not particularly limited and may be any number.

DESCRIPTION OF SYMBOLS 1 insulation state detection system 2, 2, 2A, 2B power transmission line 2C joint part 2a core 2b insulation coating part 3 relay station 4 communication network 5 management server 6 grounding wire 10, 10A-10D insulation state detection device 11 magnetic sensor 12 instrumentation amplifier 13 , 13A, 13B filter 14 peak hold circuit 15 comparator 16 alarm unit 16a wireless communication unit 18A buffer 18B buffer M1 to M4 magnetoresistance element X insulation failure point

Claims (9)

A magnetic sensor that includes a magnetoresistive element and detects a magnetic change that occurs when a partial discharge including a corona discharge occurs from an insulation coated transmission line;
And a first filter for extracting a frequency band including a characteristic frequency component of the partial discharge from an output signal of the magnetic sensor.   The magnetic sensor is attached to a part of the outer periphery of the power transmission line or a joint portion of the power transmission line, and detects a magnetic change around the power transmission line generated when the partial discharge occurs. Insulation detection device.   The insulation state detection device according to claim 1, further comprising a second filter that extracts a frequency band including a commercial frequency component from an output signal of the magnetic sensor. The first filter is a band pass filter or a high pass filter that passes characteristic frequency components due to the partial discharge,
The insulation state detection device according to claim 3, wherein the second filter is a low pass filter that passes the commercial frequency component.   The magnetic sensor is attached to a part of an outer periphery of a ground wire for grounding the insulating covering portion or the joint portion of the power transmission line, and detects a magnetic change around the ground wire when the partial discharge occurs. The insulation state detection apparatus according to any one of claims 1 to 4, wherein   The insulation state detection device according to any one of claims 1 to 5, wherein the magnetic sensor includes a Wheatstone bridge circuit of four magnetoresistive elements.   The insulation state detection apparatus according to any one of claims 1 to 6, further comprising an instrumentation amplifier that amplifies an output signal of the magnetic sensor. A peak hold circuit that holds a peak level of the output signal filtered by the first filter for a predetermined time;
A comparator that compares the output signal whose peak level is held to a threshold;
The insulation state detection device according to any one of claims 1 to 7, further comprising: an alarm unit that outputs an alarm signal when the output signal is larger than a threshold.   The insulation state detection device according to claim 8, wherein the alarm unit includes a wireless communication unit that wirelessly transmits the alarm signal.

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