JP2008216145A - Partial discharge detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partial discharge detection method capable of detecting a pulse signal based on partial discharge from a power distribution cable connection apparatus at high sensitivity. <P>SOLUTION: The partial discharge is measured by connecting detection impedance 6 to a voltage detection terminal 101 provided to a voltage detection part 100 and a metal case 10 via signal lines 4, 5 to prevent decrease in detection sensitivity of the partial discharge signal due to stray capacitance, thereby measuring the detection signal based on the partial discharge at high sensitivity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention particularly relates to deterioration diagnosis of a connection device for a power distribution cable.

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

  As a conventional method of diagnosing insulation deterioration of distribution cable connection equipment, insulation is provided for distribution cable connection equipment by providing electrodes on the outside of the housing, detecting potential fluctuation signals of the electrodes, and taking the difference of signals for three phases. Some perform a deterioration diagnosis (see, for example, 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 the field work, it is difficult to detect the partial discharge of the power distribution cable connection device with high accuracy. 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.
JP-A-6-123756 JP 2000-2743 A

  However, according to the insulation deterioration diagnosis of a conventional power distribution cable connection device, the pulse signal cannot be detected with high sensitivity because the pulse signal based on partial discharge is detected via a remote device or floating capacitance. There is a problem.

  Therefore, the objective of this invention is providing the partial discharge detection method which can detect the pulse signal based on the partial discharge from the cable connection apparatus for power distribution with high sensitivity.

  In order to achieve the above object, the present invention provides a partial discharge detection method for measuring partial discharge by connecting a detection impedance to a power detection unit provided in an aerial cable connection body and a metal case of the aerial cable connection body.

  In order to achieve the above-mentioned object, the present invention connects a detection impedance to a voltage detection unit provided in an insulating cylinder of a distribution-type mold discon direct connection type terminal connection part for distribution and a part different from the voltage detection part of the insulation cylinder. A partial discharge detection method for measuring partial discharge is provided.

  In order to achieve the above object, the present invention provides a partial discharge detection method for measuring a partial discharge in a non-contact manner by providing an electromagnetic wave detection antenna in the vicinity of a power detection unit of a distribution cable connection device.

  ADVANTAGE OF THE INVENTION According to this invention, the pulse signal based on the partial discharge from the cable connection apparatus for power distribution can be detected with high sensitivity.

(First embodiment)
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 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 104 that protects the voltage detection terminal 101 from the external environment. The protective cover 104 is rotatably supported on the metal case 10 via a shaft 105.

  The voltage detection unit 100 uses the capacitance of the insulating layer 112 provided immediately below the voltage detection terminal 101 as a coupling capacitor, so that the external semiconductivity around the voltage detection terminal 101 that is electrically insulated from the voltage detection terminal 101 is used. The layer 111 is configured so that the measurement loop is small and the partial discharge signal can be detected with high sensitivity.

  The partial discharge measuring circuit is connected to the conductor portion of the trunk cable insertion portion 120 and the metal case 10 to inject a calibration pulse signal, and to the branch cable insertion portion 125 to be used as a test sample. A voltage applying transformer 3, a detection impedance 6 electrically connected to the terminal connection portion 102 of the overhead cable connector 1 and the metal case 10 via signal lines 4 and 5, and a detection impedance 6 are connected. A tuning amplifier 7 and a waveform monitor 8 that performs visual display based on the output signal of the tuning amplifier 7 are provided.

  Next, the operation of the above configuration will be described. First, the protective cover 104 of the voltage detection unit 100 is opened, and the signal lines 4 and 5 are connected to the voltage detection terminal 101 and the metal case 10. Next, only noise is detected with no partial discharge and with the calibration pulse oscillator 2 stopped. This noise detection is performed at the detection impedance 6 from the detection terminal 101 and the metal case 10 via the signal lines 4 and 5, and a detection signal is output from the detection impedance 6 to the tuning amplifier 7. The tuning amplifier 7 tunes and amplifies at a selected measurement frequency. The amplified detection signal is output to the waveform monitor 8 so that the frequency spectrum (NI (f)) for the noise is visually displayed on the display screen.

  Next, the calibration pulse oscillator 2 is operated to inject a calibration pulse into the aerial cable connector 1. The calibration pulse is detected by the detection impedance 6 through the signal lines 4 and 5, and the detection signal amplified through the tuning amplifier 7 is output to the waveform monitor 8, whereby the frequency spectrum (SI (F)) is visibly displayed on the display screen.

From the above results, the S / N ratio is obtained by the following equation.
S / N = SI (f) / NI (f) --- (1)

  FIG. 2 shows the result of partial discharge measurement with a defect in the aerial cable connector shown in FIG. 1, (a) shows a spectrum image of a waveform monitor based on calibration pulse injection, and (b) shows calibration. The figure which shows the S / N ratio spectrum image of the waveform monitor based on pulse injection, (c) is a figure which shows the measurement frequency and its detection sensitivity of a partial discharge.

  As shown in FIG. 2A, the noise spectrum is displayed on the display unit screen 80 of the waveform monitor by performing the noise measurement and the measurement in the state where 30 pC of the calibration pulse is injected on the aerial cable connector 1 as described above. 81 and a calibration pulse spectrum 82 were obtained. Further, when the display unit screen 80 is switched to the S / N ratio spectrum display, the S / N ratio spectrum 83 is displayed as shown in FIG. 2B, and the optimum partial discharge measurement frequency is obtained from the result. Is around 35 MHz, and the S / N ratio was 20 dB. Therefore, it can be seen that the noise level is as low as about 3 pC.

  In addition, as shown in FIG. 2C, when the partial discharge measurement was performed with the measurement frequency set to 1 MHz with respect to the detection sensitivity with respect to the measurement frequency, the noise was large at 30 pC or more, and the injected calibration pulse was detected. Can not do it. On the other hand, when partial discharge measurement was performed with the measurement frequency set to 10 MHz, a detection result with less noise of 10 pC was obtained. As is clear from FIG. 2B, it can be seen that the present technique using a small coupling capacitor can provide a high S / N ratio at a measurement frequency of 5 MHz or more.

  FIG. 3 is a diagram showing a calibration curve of the partial discharge charge amount of the aerial cable connection body provided with a defect. It was confirmed that the signal saturation level at the partial discharge measurement frequency of 35 MHz was 250 pC or more.

  FIG. 4 shows an observation waveform at the time of partial discharge measurement using a sample in which water droplets are mixed as a simulated defect at the interface between the branch cable (not shown) and the insulating rubber of the aerial cable connector in the aerial cable connector shown in FIG. FIG. In the figure, the waveform of the applied voltage 85, the ground line current 86, and the partial discharge detection signal 87 obtained from the voltage detection terminal is shown on the display screen 80. The partial discharge measurement frequency in this case was set to 15.6 MHz because the external noise at 35 MHz was large. As a result, the waveform of the detection signal 87 based on the partial discharge appears in the first quadrant and the third quadrant of the observed waveform.

  The partial discharge measurement frequency is determined by the capacitance of the coupling capacitor on which the voltage detection unit 100 operates. The partial discharge voltage generated in the measurement object is determined by the voltage dividing ratio between the coupling capacitor and the detection impedance. However, since the impedance of the coupling capacitor is inversely proportional to the frequency, the relationship that the detection impedance is greater than the impedance of the coupling capacitor is established. Otherwise, sufficient voltage is not generated across the detection impedance, and it is difficult to detect the partial discharge signal with high sensitivity.

(Effects of the first embodiment)
According to the first embodiment described above, in the aerial cable connector 1, the detection impedance 6 is connected to the voltage detection terminal 101 provided in the voltage detection unit 100 and the metal case 10 via the signal lines 4 and 5. By measuring the discharge, the detection signal based on the partial discharge can be measured with high sensitivity.

  In the first embodiment, the partial discharge measurement of a single aerial cable connector has been described. However, the partial discharge measurement based on the configuration described in the first embodiment is performed for a plurality of aerial cable connectors. The partial discharge measurement signals obtained as a result may be compared.

  Moreover, although FIG. 1 demonstrated the case where the power transmission transformer 3 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.

(Second Embodiment)
FIG. 5 is a diagram illustrating a partial discharge detection circuit according to a second embodiment of the present invention and a molded die-con connection-type terminal connection part (MDS-CH) insulating cylinder for power distribution to be diagnosed.

  This MDS-CH insulation cylinder 20 is used for multi-branch opening / closing of a high-voltage underground distribution line installed in a distribution supply box such as a high-voltage cabinet, and is provided around a cable 31 at a terminal connection portion. The internal semiconductive rubber 22, the insulating rubber 23, and the external semiconductive rubber 24 are laminated, and the voltage detection terminal 101 is brought into contact with the insulating rubber 23 exposed by cutting away a part of the external semiconductive rubber 24. The voltage detection terminal 100 is provided, and the voltage detection terminal 101 is insulated from the external semiconductive rubber 24 through an insulating rubber 103. The external semiconductive rubber 24 is electrically connected to the external semiconductive layer 34 of the cable 31.

  The voltage detection unit 100 uses the capacitance of the insulating rubber 23 provided immediately below the voltage detection terminal 101 as a coupling capacitor, so that the external semiconductivity around the voltage detection terminal 101 electrically insulated from the voltage detection terminal 101 is obtained. The rubber 24 is configured so that the measurement loop is small and the partial discharge signal can be detected with high sensitivity.

  The partial discharge measurement circuit includes a calibration pulse oscillator 2 that is electrically connected to the central conductor 32 of the cable 31 near the MDS-CH insulating cylinder 20 and the external semiconductive rubber 24 and injects a pulse signal for calibration, and the cable 31. The signal transformer 4 connected to the central conductor 32 of the power supply transformer 3 for injecting a signal pulse for partial discharge measurement, the terminal connection part 102 of the voltage detection part 100 and the external semiconductive rubber 24 in the vicinity of the voltage detection part 100. 5, a detection impedance 6 that is electrically connected via 5, a tuning amplifier 7 connected to the detection impedance 6, and a digital oscilloscope 9 that displays a waveform based on an output signal of the tuning amplifier 7.

  The operation of the above configuration is performed in the same manner as the measurement operation for the aerial cable connector described in the first embodiment. First, only noise is detected with no partial discharge and with the calibration pulse oscillator 2 stopped. This noise detection is performed with the detection impedance 6 from the terminal connection portion 102 connected to the detection terminal 101 and the external semiconductive rubber 24 via the signal lines 4 and 5, and a detection signal is output from the detection impedance 6 to the tuning amplifier 7. Is done. The tuning amplifier 7 tunes and amplifies the detection signal using the selected measurement frequency as the tuning frequency. The amplified detection signal is output to the digital oscilloscope 9, so that the frequency spectrum (NI (f)) corresponding to the noise is visually displayed on the display screen.

  Next, the calibration pulse oscillator 2 is operated to inject a calibration pulse into the center conductor 32 and the external semiconductive rubber 24. The calibration pulse is detected by the detection impedance 6 through the signal lines 4 and 5, and the detection signal amplified through the tuning amplifier 7 is output to the digital oscilloscope 9, whereby the frequency spectrum (SI (F)) is visibly displayed on the display screen. Further, the S / N ratio is obtained from the frequency spectrum (SI (f)) of the calibration pulse and the frequency spectrum (NI (f)) of the noise by the above-described equation (1), and is visually displayed on the digital oscilloscope 9.

  6 shows the result of the partial discharge measurement of the MDS-CH insulating cylinder shown in FIG. 5, (a) is a diagram showing a spectrum image of a digital oscilloscope, and (c) is the measurement frequency of the partial discharge and its detection sensitivity. FIG.

  The MDS-CH insulation cylinder 20 is calibrated on the display screen 90 of the digital oscilloscope as shown in FIG. 6A by performing noise measurement and measurement with 10 pC of the calibration pulse injected as described above. A pulse spectrum 91, a noise spectrum 92, and an S / N ratio spectrum 93 were obtained. According to the S / N ratio spectrum 93, a signal intensity ratio of 20 dB (corresponding to a detection sensitivity of 1 pC) or more is obtained at 2 MHz or more.

  Moreover, as shown in FIG. 6B, when the partial discharge measurement was performed with the measurement frequency set to 1 MHz with respect to the detection sensitivity with respect to the measurement frequency, the noise was large at 10 pC or more, and the injected calibration pulse was detected. Can not do it. On the other hand, when partial discharge measurement was performed with the measurement frequency set to 10 MHz, a detection result with a low noise of 1 pC was obtained. As is clear from FIG. 6A, it can be seen that the MDS-CH insulating cylinder 20 can obtain a high S / N ratio at a measurement frequency of 2 MHz or more.

(Effect of the second embodiment)
According to the second embodiment described above, the signal wires 4 and 5 are connected to the voltage detection terminal 101 and the external semiconductive rubber 24 provided in the voltage detection unit 100 for the MDS-CH insulating cylinder 20 as well as the overhead cable connector. By measuring the partial discharge by connecting the detection impedance 6 through the detection signal, the detection signal based on the partial discharge can be measured with high sensitivity.

  FIG. 7 is a diagram showing a partial discharge detection circuit according to a third embodiment of the present invention and a distribution-type molded diescon direct connection type termination connection part (MDS-CH) insulation cylinder to be diagnosed. FIG. 4B is a schematic diagram showing an equivalent circuit around the MDS-CH insulating cylinder and the antenna.

  In the third embodiment, a solenoid coil antenna (hereinafter referred to as “antenna”) 40 as a non-contact detection unit is provided in the vicinity of the voltage detection unit 100 of the MDS-CH insulating cylinder 20. Here, the distance between the voltage detector 100 and the antenna 40 shown in FIG. 7A is set to 10 cm.

  Also for the above-described configuration, noise measurement and measurement in a state where a calibration pulse is injected by 10 pC are performed as in the second embodiment. The antenna 40 outputs a signal received from the power detection unit 100 to the detection balun 13 through the signal lines 4 and 5. A detection signal amplified via the preamplifier 14 is output from the detection balun 13 to the spectrum analyzer 15, whereby the noise spectrum and the calibration pulse spectrum are visually displayed on the display screen.

  FIG. 8 is a diagram showing a frequency spectrum image in the spectrum analyzer. Here, the spectrum at the time of partial discharge by 4.1 kV charging and the spectrum at the time of no charging are visibly displayed on the same screen, and the difference between the two spectra indicates the signal level increased by the partial discharge. Show. The figure shows that the partial discharge signal was detected up to 200 MHz. As a result of converting the sensitivity of the partial discharge measurement at the time of this measurement, it was confirmed that detection sensitivities of 3 to 7 were obtained.

(Effect of the third embodiment)
According to the third embodiment described above, even when the antenna 40 that receives the electromagnetic wave radiated from the power detection unit 100 of the MDS-CH insulating cylinder 20 is provided and the partial discharge measurement is performed in a non-contact manner, the second implementation is performed. The partial discharge signal can be detected with the same sensitivity as that of the first embodiment. This is because in a high frequency band such as an electromagnetic wave, the impedance is very small even with a small stray capacitance as shown in FIG.

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 of the present invention. FIG. 2 shows the result of partial discharge measurement with a defect in the aerial cable connector shown in FIG. 1, (a) shows a spectrum image of a waveform monitor based on calibration pulse injection, and (b) shows calibration. The figure which shows the S / N ratio spectrum image of the waveform monitor based on pulse injection, (c) is a figure which shows the measurement frequency and its detection sensitivity of a partial discharge. FIG. 3 is a diagram showing a calibration curve of the partial discharge charge amount of the aerial cable connection body provided with a defect. In the aerial cable connection body shown in FIG. 1, it is a figure which shows the observation waveform at the time of the partial discharge measurement by the sample which mixed the water drop as a simulation defect in the interface of the branch cable which is not shown in figure and the insulation rubber | gum of an aerial cable connection body. FIG. 5 is a diagram illustrating a partial discharge detection circuit according to a second embodiment of the present invention and a molded die-con connection-type terminal connection part (MDS-CH) insulating cylinder for power distribution to be diagnosed. 6 shows the result of the partial discharge measurement of the MDS-CH insulating cylinder shown in FIG. 5, (a) is a diagram showing a spectrum image of a digital oscilloscope, and (c) is the measurement frequency of the partial discharge and its detection sensitivity. FIG. FIG. 7 is a diagram showing a partial discharge detection circuit according to a third embodiment of the present invention and a distribution-type molded diescon direct connection type termination connection part (MDS-CH) insulation cylinder to be diagnosed. FIG. 4B is a schematic diagram showing an equivalent circuit around the MDS-CH insulating cylinder and the antenna. FIG. 8 is a diagram showing a frequency spectrum image in the spectrum analyzer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Overhead cable connection body, 2 ... Calibration pulse oscillator, 3 ... Power transformer, 4, 5 ... Signal line, 6 ... Detection impedance, 7 ... Tuning amplifier, 8 ... Waveform monitor, 9 ... Digital oscilloscope, 10 ... Metal case , 11 ... connection body, 13 ... detection balun, 14 ... preamplifier, 15 ... spectrum analyzer, 20 ... MDS-CH insulating cylinder, 22 ... internal semiconductive rubber, 23 ... insulating rubber, 24 ... external semiconductive rubber, 31 ... Cable, 32 ... Center conductor, 33 ... Insulating layer, 34 ... External semiconductive layer, 40 ... Solenoid coil antenna, 80 ... Display screen, 81 ... Noise spectrum, 82 ... Calibration pulse spectrum, 83 ... S / N ratio Spectrum: 85 ... Voltage applied, 86 ... Ground line current, 87 ... Detection signal, 90 ... Display screen, 91 ... Calibration pulse spectrum, 92 ... External noise spectrum Tol, 93 ... S / N ratio spectrum, 100 ... voltage detector, 101 ... voltage detector, 102 ... terminal connection, 103 ... insulating rubber, 104 ... protective cover, 105 ... shaft, 110 ... rubber unit, 111 ... external Semiconducting layer, 112 ... insulating layer, 113 ... internal semiconducting layer, 120 ... trunk cable insertion part, 121 ... central conductor sleeve, 122 ... tulip contact, 123 ... conductor branch part, 125 ... branch cable insertion part

Claims (6)

  A partial discharge detection method characterized in that a partial discharge is measured by connecting a detection impedance to a voltage detector provided in an aerial cable connector and a metal case of the aerial cable connector.   The partial discharge detection method according to claim 1, wherein in the measurement of the partial discharge, a partial discharge detection frequency is set to 5 MHz or more.   A voltage detector provided in an insulating cylinder of a molded diescon direct connection type terminal connection part, and a partial impedance is measured by connecting a detection impedance to an external shielding layer portion different from the voltage detector of the insulating cylinder. Partial discharge detection method.   The partial discharge detection method according to claim 3, wherein in the measurement of the partial discharge, a partial discharge detection frequency is set to 2 MHz or more.   A partial discharge detection method characterized in that a partial discharge is measured in a non-contact manner by providing an electromagnetic wave detection antenna in the vicinity of a power detection unit of a distribution cable connection device.   The partial discharge detection method according to claim 5, wherein the power distribution cable connection device is an aerial cable connection body or an insulation cylinder of a power distribution molded diescon direct connection type terminal connection portion.

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