JP2008216144A - Method of exposing interfacial defect of aerial cable connection body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of exposing an interfacial defect of an aerial cable connection body capable of securely exposing the defect when diagnosing insulation deterioration to prevent incorrect determination. <P>SOLUTION: Because the defect is made apparent by applying mechanical vibration to the aerial cable connection body 1 in such a state in which a line is live, the insulating performance is precisely grasped. Further, the trouble of pulling out a cable from the aerial cable connection body 1 to visually observe the interface may be dispensed with. Accordingly, it contributes to reduction of maintenance costs resulting from simplified diagnosis work and reduction of costs resulting from increased efficiency of diagnosis business without restrictions of diagnosing time while not interrupting the power transmission of the line during the maintenance and inspection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for revealing an interface defect of a power cable, particularly an aerial cable connector for power distribution.

   In the distribution high-voltage overhead cable branch connection body (hereinafter referred to as “cable branch connection body”), when insulation deterioration progresses, partial discharge occurs at the insulation deterioration portion. Therefore, the insulation deterioration diagnosis in the cable branch connector has been performed by detecting the occurrence state of the partial discharge.

  As a conventional method for diagnosing insulation deterioration of cable branch connections, insulation deterioration diagnosis of cable branch connections is made by providing electrodes on the outside of the housing, detecting potential fluctuation signals of the electrodes, and taking the difference of the signals for the three phases. (For example, refer to Patent Document 1).

  According to the method of Patent Document 1, since noise components are removed from signals measured in the field and only signals due to partial discharge are detected, insulation deterioration diagnosis can be performed easily and accurately.

  Moreover, when environmental noise is large in field work, it is difficult to accurately detect the partial discharge of the cable branch connector. Therefore, there is a type that detects a high-frequency current signal from a current transformer attached to a cable and diagnoses the degree of insulation deterioration based on the waveform pattern and frequency spectrum (see, for example, Patent Document 2).

  According to the method of Patent Document 2, the S / N ratio between the partial discharge signal and the environmental noise is improved, so that even a small partial discharge can be diagnosed with high accuracy.

  Moreover, it is known that the insulation degradation site | part will produce a difference in the generation | occurrence | production situation of a partial discharge by a dry state and an infiltration state. Therefore, a method for determining the deterioration state based on the electrical conductivity of the insulating portion has been proposed (see, for example, Patent Document 3).

According to the method of Patent Document 3, when the electrical conductivity of the ground side external semiconductive rubber fitting portion is lowered, it is determined that the deterioration of the insulating portion is progressing.
JP-A-6-123756 JP 2000-2743 A JP-A-7-104028

  However, according to the conventional insulation deterioration diagnosis of cable branch connections, a deterioration signal corresponding to the defect is not always generated at the time of diagnosis. However, there is a problem that the quality of insulation characteristics cannot be judged correctly.

  High-voltage cable lines for distribution use have a relatively low operating electric field, so the progress of insulation deterioration is slow. Usually, the deterioration signal is measured regularly and the magnitude is compared with the judgment criteria to determine the quality of the insulation characteristics. is doing. However, the deterioration signal generated from the defective part does not occur continuously, but tends to increase gradually while repeating generation and stoppage. It is also possible that is stopped.

  As described above, when the degradation signal is stopped by chance at the measurement timing, there is a defect that it is erroneously determined as a “healthy product” even though the defect is generated. In addition to this, there are many facilities on the actual line where high voltage is applied around the object to be measured, and it is also concerned that the deterioration signal generated in the surrounding equipment of the object to be measured is induced and detected. Is done.

  Accordingly, it is an object of the present invention to provide a method for revealing interface defects in an aerial cable connection body that can surely reveal defects during diagnosis of insulation deterioration or the like and prevent erroneous determination.

  In order to achieve the above object, the present invention provides a first step of performing a degradation signal measurement of an aerial cable connection body and a second step of applying a disturbance to a predetermined part of the aerial cable connection body during the execution of the degradation signal measurement. And a third step of observing the signal output status of the degradation signal measurement based on the application of the disturbance, a method for revealing interface defects in an aerial cable connector is provided.

  ADVANTAGE OF THE INVENTION According to this invention, a defect can be reliably exposed at the time of diagnosis, such as insulation deterioration, and a misjudgment can be prevented.

  When a degradation signal is intermittently generated in an aerial cable connector as a measurement object, the appearance of the degradation signal changes (increases or decreases) by applying mechanical vibration as a disturbance. From this, it is possible to determine whether the signal is a suspicious deterioration signal such as noise that occurs in an aerial cable connection body or its peripheral equipment, and is detected by guiding it to the aerial cable connection body, or a true deterioration signal. Can manifest. This is because in the case of a suspicious deterioration signal, the detection signal does not change even when mechanical vibration is applied.

  FIG. 1 is a diagram showing a partial discharge detection circuit and an aerial cable connection body to be diagnosed according to an embodiment of the present invention.

  The aerial cable connector 1 is provided for branching a branch cable from a trunk cable, and includes a metal case 10 having a voltage detection unit 100 that is made of aluminum and detects a partial discharge signal, and a metal case. The connector body 11 is housed in the body 10.

  The connecting body 11 is connected via a center conductor sleeve 121 connected to a conductor of a trunk cable (not shown) inserted from a trunk cable insertion portion 120 provided on the trunk line side, and the center conductor sleeve 121 and a tulip contact 122. It has a conductor branch part 123 and a branch cable insertion part 125 connected to the branch side of the conductor branch part 123 and is covered with a rubber unit 110 comprising an outer semiconductive layer 111, an insulating layer 112, and an inner semiconductive layer 113. The metal case 10 is configured to be accommodated.

  The voltage detection unit 100 includes a voltage detection terminal 101 that is a metal terminal provided so as to be in contact with the insulating layer 112 of the rubber unit 110, and an openable / closable protective cover 102 that protects the voltage detection terminal 101 from the external environment. The protective cover 102 is rotatably supported on the metal case 10 via a shaft 104.

  The partial discharge measuring circuit is connected to the branch cable insertion part 125, and the signal transformers 4 and 5 are connected to the voltage transformer 2 for applying a voltage to the specimen, the voltage detection terminal 101 of the overhead cable connector 1, and the metal case 10. And a waveform monitor 8 having a display unit for performing visual display based on an output signal of the tuning amplifier 7.

  FIG. 2 is a flowchart showing a partial discharge measurement operation in the aerial cable connector shown in FIG.

  First, the protective cover 102 of the voltage detection unit 100 is opened, the signal line 4 is connected to the voltage detection terminal 101, the signal line 5 is connected to the metal case 10, and the voltage transformer 2 is connected to the branch cable insertion unit 125. The branch cable is inserted (S101), and partial discharge measurement is started (S102).

  Next, as the partial discharge measurement step, the power transformer 2 is operated to apply power to the trunk cable (S103).

  Next, as a disturbance applying step, mechanical vibration as a disturbance is applied to the root of the branch cable inserted into the branch cable insertion portion 125 using the principle of insulator (S104).

  By applying power while measuring the partial discharge in this way, a detection signal corresponding to the occurrence state of the partial discharge is output. The tuning amplifier 7 tunes and amplifies at a selected measurement frequency. The amplified detection signal is output to the waveform monitor 8. The operator observes the state of occurrence of insulation deterioration by monitoring the signal waveform displayed on the waveform monitor 8 (S105). The observation is continued until a certain time has elapsed since the start of the observation of the insulation deterioration (S106: No), and is terminated after the lapse (S106: Yes).

  FIG. 3 is a partially enlarged view showing the branch cable insertion portion shown in FIG. As shown in the figure, when an external force 21 is applied to the branch cable 20 as indicated by an arrow in a state where the branch cable 20 is inserted into the metal case 10, mechanical vibration is generated in the entire metal case 10 using the branch cable insertion portion 125 as a fulcrum. It is transmitted.

  Fig. 4 shows the observed waveforms at the time of partial discharge measurement when there is a defect at the interface between the rubber unit of the aerial cable connector and the insulator surface of the cable inserted in the trunk cable insertion part and branch cable insertion part. (A) is a waveform when mechanical vibration is not applied, and (b) is a waveform when mechanical vibration is applied. In the figure, the monitor display screen 50 shows the waveform of the applied voltage 51, the leakage current 52 as reference data, and the partial discharge detection signal 53 obtained from the voltage detection terminal.

  The dielectric breakdown of the aerial cable connector 1 is mainly caused by the interface breakdown with the cable, and the cause is the occurrence of defects (interface gap) due to the inclusion of foreign matter or the thinning of parts. Therefore, when a defect is generated at the interface, the defect can be revealed by stimulating the interface, and as a method for that, it is easy to add mechanical vibration due to impact as a disturbance to the measurement object. And it has been confirmed by the present inventors that it is effective.

  In a state where no mechanical vibration is applied, there is a case where a partial discharge signal is not detected even though there is a defect as shown in FIG. 4A, but mechanical vibration is applied to the branch cable 20 as shown in FIG. When added, a pulse-like signal 53P appears in the partial discharge detection signal 53 as shown in FIG. 4B, and it can be seen that a defect at the interface is manifested by applying mechanical vibration.

  FIG. 5 shows an observation waveform at the time of partial discharge measurement when the interface between the rubber unit of the aerial cable connection body and the insulator surface of the cable inserted into the trunk cable insertion part and the branch cable insertion part is normal. (A) is a waveform when no mechanical vibration is applied, and (b) is a waveform when mechanical vibration is applied.

  As shown in FIG. 5, when the interface state is normal, no pulse signal is detected regardless of the presence or absence of mechanical vibration, and it can be seen that the cable is in a good connection state. From this, while measuring the insulation resistance between the cable center conductor and the installation potential of the aerial cable connector 1, by applying a disturbance to the object to be measured, the presence or absence of a change in the insulation resistance measurement value is observed. It is also possible to specify a deterioration point and a failure (destruction) point.

  In addition, the above-described defect manifesting method can be applied to a line to which a plurality of overhead cable connectors 1 are connected.

  As an application example thereof, for example, in a line to which a plurality of aerial cable connectors 1 are connected, a voltage is applied while measuring a degradation signal such as a partial discharge signal or a loss current of the test object line, and each aerial cable connector 1 mechanical vibrations are sequentially added as disturbances. During this operation, when the behavior of the detection signal being monitored changes, it can be determined that a defect occurs in the overhead cable connector that applies mechanical vibration.

  Also, the method for applying the disturbance is not limited to the above-described mechanical vibration applied to the measurement object, and may be a disturbance caused by heating or cooling the measurement object, for example. In this case, the defect is revealed based on changing the interface gap between the rubber unit 110 of the overhead cable connector 1 and the surface of the cable insulator based on the temperature change of the measurement object. Also about the site | part which applies mechanical vibration, it is not limited to the root of the above-mentioned branch cable, Other places, such as the metal case 10, may be sufficient.

  According to the above-described embodiment of the present invention, it is possible to reveal defects by applying mechanical vibration to the aerial cable connector 1 in a state where the line is utilized, so that the insulation performance can be accurately grasped. it can. Also, it is possible to save the trouble of pulling out the cable from the aerial cable connector 1 and visually observing the interface, and reducing maintenance costs by making it possible to easily perform diagnostic work without stopping power transmission on the track during maintenance and inspection. In addition, it contributes to cost reduction by improving the efficiency of diagnosis work by not being restricted by diagnosis time.

  In the embodiment described above, the method of applying a disturbance at the time of partial discharge measurement in the aerial cable connector 1 has been described. However, the present invention is not limited to partial discharge measurement, and at the time of measurement of loss current change or ground line current change. Even when a disturbance is applied at the time of measurement, it is effective as a method for making defects appear and making a correct deterioration diagnosis possible.

  Moreover, although FIG. 1 demonstrated the case where the power transmission transformer 2 was prepared separately from a track | line, for example, the hot-line operation | work using the commercial transformer provided in the actual track | line is also possible.

FIG. 1 is a diagram showing a partial discharge detection circuit and an aerial cable connection body to be diagnosed according to the first embodiment. FIG. 2 is a flowchart showing a partial discharge measurement operation in the aerial cable connector shown in FIG. FIG. 3 is a partially enlarged view showing the branch cable insertion portion shown in FIG. Fig. 4 shows the observed waveforms in the partial discharge measurement operation when there is a defect at the interface between the rubber unit of the aerial cable connector and the insulator surface of the cable inserted in the trunk cable insertion part and branch cable insertion part. (A) is a waveform when mechanical vibration is not applied, and (b) is a waveform when mechanical vibration is applied. FIG. 5 shows an observation waveform in the partial discharge measurement operation when the interface between the rubber unit of the aerial cable connection body and the insulator surface of the cable inserted into the trunk cable insertion part and the branch cable insertion part is normal. (A) is a waveform when no mechanical vibration is applied, and (b) is a waveform when mechanical vibration is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Overhead cable connection body, 2 ... Power transformer, 4,5 ... Signal line, 6 ... Detection impedance, 7 ... Tuning amplifier, 8 ... Waveform monitor, 10 ... Metal case, 11 ... Overhead cable connection body, 20 ... Branch Cable, 21 ... External force, 100 ... Detecting section, 101 ... Detecting terminal, 102 ... Protective cover, 104 ... Shaft, 110 ... Rubber unit, 111 ... External semiconductive layer, 112 ... Insulating layer, 113 ... Internal semiconductive layer 120 ... trunk cable insertion part, 121 ... central conductor sleeve, 122 ... tulip contact, 123 ... conductor branch part, 125 ... branch cable insertion part

Claims (5)

A first step of performing a degradation signal measurement of an aerial cable connector;
A second step of applying a disturbance to a predetermined part of the aerial cable connection body during execution of the deterioration signal measurement;
And a third step of observing the signal output status of the degradation signal measurement based on the application of the disturbance.   2. The method for revealing interface defects in an aerial cable connector according to claim 1, wherein in the second step, the disturbance is applied to a cable insertion portion as the predetermined portion.   2. The method for revealing interface defects of an aerial cable connector according to claim 1, wherein the first step performs the degradation signal measurement based on a partial discharge in the aerial cable connector.   2. The method for revealing interface defects of an aerial cable connection according to claim 1, wherein the first step performs the deterioration signal measurement based on a loss current change in the aerial cable connection.   2. The method for revealing interface defects in an aerial cable connector according to claim 1, wherein the first step performs the deterioration signal measurement based on a ground line current change in the aerial cable connector.

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