JP6090982B2 - Method for detecting water tree deterioration of power cable using pulse voltage - Google Patents

Description

The present invention relates to how to perform the detection of water tree degradation of the power cable using a pulsed voltage.

  A cross-linked polyethylene insulated cable (CV cable) has been put to practical use as a power cable. When the CV cable is used for a long time under moisture, a deterioration phenomenon called a water tree occurs in the insulator and causes a decrease in insulation performance. As a method for detecting insulation deterioration (water tree deterioration) due to a water tree, a residual charge method has been conventionally known (Patent Document 1).

  The technique disclosed in Patent Document 1 applies a pulse voltage of a frequency higher than the commercial frequency to the power cable and grounds it, accumulates charge in the entire power cable, and discharges the charge in the normal part. This is a technique for diagnosing deterioration based on the charge discharged from the deteriorated part by discharging the charge accumulated in the deteriorated part by applying an AC voltage.

  By using this technology, even a CV cable connected to a gas-insulated switchgear (GIS) can accurately diagnose the deterioration by releasing residual charges. However, a large test apparatus (AC power supply) that generates an AC voltage is required, and the test apparatus itself and the transfer are expensive. In addition, it takes time for changing the setup from the pulse voltage to the AC voltage and time for stepping up and down the AC voltage, which takes time for diagnostic measurement.

  In recent years, when diagnosing deterioration of a power cable, it is desired to reduce the size of the apparatus and shorten the diagnostic measurement time in a state in which an accurate signal output is maintained regardless of the connection to the GIS. For this reason, there is provided a water tree degradation detection device for a power cable and a pulse voltage using a pulse voltage that can accurately measure the degradation of the power cable in an extremely short time without increasing the cost by using an expensive device. At present, there is a need for a method for detecting water tree degradation in power cables used.

JP 2009-186335 A

The present invention has been made in view of the above circumstances, without increasing the cost, power cable water tree using Rupa pulse voltage can be accurately determined water tree degradation of the power cables in a very short time An object is to provide a degradation detection method.

A detection apparatus for carrying out a method for detecting water tree deterioration of a power cable using a pulse voltage according to the present invention applies a first pulse voltage having a pulse width of 0.1 ms or more to the power cable to accumulate charges, And applying a second pulse voltage having a pulse width of 0.1 ms or more to the first voltage applying means for discharging the accumulated electric charge and to the power cable after the electric charge is discharged by the first voltage applying means. A second voltage applying means for releasing the initial residual charge, and a reference pulse voltage having the same waveform and the same polarity as the second pulse voltage are applied to the power cable after the initial residual charge is released by the second voltage applying means. A reference pulse voltage applying means to be applied and a second current value when the initial residual charge is released by the second voltage applying means are measured, and a reference voltage is applied by the reference pulse voltage applying means. A determination means for measuring a reference current value when a voltage is applied, and determining deterioration of the power cable based on the second current value and the reference current value, and the first voltage application means, and The second voltage application unit is connected to each of two power cables via the determination unit, and the determination unit outputs only a signal of a difference between the second current value and the reference current value. It is characterized by.

As a result, the first pulse voltage is applied to accumulate the charge, the charge accumulated by grounding is released, and then the second pulse voltage is applied. The initial residual charge of the charge is released and the second current value is measured. Thereafter, a reference current value is measured by applying a reference pulse voltage. Since the charge voltage is accumulated and the charge is discharged by applying the pulse voltage, the intensity of the signal is increased as compared with the case where the AC voltage is applied.

  The pulse width of the first pulse voltage and the second pulse voltage is preferably set from 0.1 ms to 10 ms. It is also possible to set a pulse width exceeding 10 ms.

  An open / close switch may be provided between the first voltage applying unit and the second voltage applying unit and any one of the power cables. By applying the first pulse voltage with the open / close switch open, no charge is accumulated in the deteriorated part regardless of the deterioration state of the power cable, and then the open / close switch is closed and the second pulse voltage is applied. However, no emission signal is issued because there is no initial residual charge. For this reason, even when the deterioration state of the power cable is not known, it can be applied as a power cable in a state where no deterioration has occurred by operating the open / close switch.

  If there is a difference between the second current value and the reference current value, it is determined that there is an initial residual charge and the power cable has deteriorated. If there is no difference between the second current value and the reference current value, It is determined that there is no initial residual charge and no water tree degradation has occurred in the power cable.

  Therefore, a pulse voltage that can accurately determine the water tree deterioration of the power cable in a very short time by simply measuring the difference between the second current value and the reference current value without increasing the cost. It becomes a water tree deterioration detection device of the power cable using

Then, after the initial remaining charge is released by the pre-Symbol second voltage applying means, to the power cable before the application of the reference pulse voltage by the reference pulse voltage applying means, said by the first voltage applying means first And a third voltage applying means for releasing a residual charge by applying a third pulse voltage having a polarity opposite to that of the pulse voltage and having the same waveform, wherein the determining means is configured by the second current value and the third voltage applying means. Deterioration of the power cable is determined based on the reference current value after releasing the residual charge.

As a result, deterioration is determined based on a difference signal between the reference current value after the residual charge (many charges) is released by the application of the third pulse voltage and the second current value. The signal output can be increased and the signal output can be increased, and deterioration can be easily determined.

The front Symbol first voltage applying means, said second voltage applying means, the reference pulse voltage applying means, said third voltage applying means, the power cable power stored in the capacitor as the pulse voltage by closing the switch It is characterized by applying to.

The upper limit to the pulse width of the pulse voltage, and characterized in that a 10ms is a half cycle of the commercial AC voltage.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a method for detecting water tree deterioration of a power cable using a pulse voltage, and applying a first pulse voltage having a pulse width of 0.1 ms or more to the power cable. And discharging a charge accumulated by the ground, and applying a second pulse voltage having a pulse width of 0.1 ms or more to the power cable after the charge is released to release an initial residual charge, A third pulse voltage having the same polarity and opposite polarity as the first pulse voltage is applied to the power cable after the initial residual charge is released to release the residual charge, and then the third pulse voltage is applied. to the power cable after residual charge is released Te, upon applying the second pulse voltage of the same waveform and the same polarity of the reference pulse voltage, the power cable is required to detect the water tree degradation, before When the first pulse voltage, the second pulse voltage, the third pulse voltage, and the reference pulse voltage are applied, the second current value when the second pulse voltage is applied and the reference pulse voltage are applied While the current value corresponding to the difference value of the reference current value is measured, the first pulse is applied to the power cable that has the same capacitance and no water tree deterioration as the power cable that needs to detect the water tree deterioration. Apply a voltage, the second pulse voltage, the third pulse voltage, and the reference pulse voltage to detect a current value in the opposite direction of the current value corresponding to the difference between the second current value and the reference current value The current value waveform of the power cable that needs to detect water tree degradation and the current value of the power cable that has the same capacitance and no water tree degradation as the power cable that needs to detect water tree degradation Waveform When the current value waveform appears, the water tree deterioration is detected on the assumption that the current value waveform based on the discharge of the electric charge accumulated in the power cable that needs to detect the water tree deterioration appears. It is characterized by that.

  For this reason, a pulse voltage that can accurately determine the deterioration of the power cable in an extremely short time is used by simply measuring the difference between the second current value and the reference current value without increasing the cost. This is a method for detecting water tree deterioration in power cables.

Pulse voltage water tree deterioration detecting method of power cables with the present invention, without increasing the cost, it is possible to accurately determine the water tree degradation of the power cables in a very short time.

It is a schematic block diagram of the apparatus which implements the water tree deterioration detection method of the power cable using the pulse voltage which concerns on one Example of this invention. It is a figure showing the time-dependent change of the power-applied state of the water tree deterioration detection method of the power cable using the pulse voltage which concerns on one Example of this invention. It is a conceptual diagram of electric charge discharge | release. It is a figure showing a time-dependent change of switch operation. It is a graph showing the relationship between a pulse width and a detected charge amount. It is a conceptual diagram of a current detection situation. It is a conceptual diagram of a current detection situation. 1 is a specific configuration diagram of an apparatus that performs a water tree deterioration detection method for a power cable using a pulse voltage according to an embodiment of the present invention. It is a conceptual diagram of a current detection situation. It is a conceptual diagram of a current detection situation. It is a principal part block diagram of the reference example of the apparatus which implements the water tree deterioration detection method of an electric power cable. It is a schematic block diagram explaining an example of a usage example.

When a cross-linked polyethylene insulated cable (CV cable) is used as a power cable for a long time under moisture, a degradation phenomenon called water tree (water tree degradation) occurs in the insulator. An apparatus that performs the deterioration detection method of this embodiment is an apparatus that determines whether or not water tree deterioration has occurred in the CV cable.

An apparatus for carrying out a method for detecting water tree deterioration of a power cable using a pulse voltage according to the present invention is characterized by the following configuration.

  Charge is accumulated by applying a first pulse voltage with a pulse width of 0.1 ms or more (preferably 0.1 ms to 10 ms) to the power cable, and discharging the accumulated charge by grounding (first voltage applying means) Then, a second pulse voltage having a pulse width of 0.1 ms or more (preferably 0.1 ms to 10 ms) is applied to the power cable after the charge is released to release the initial residual charge (second voltage applying means). .

  The pulse widths of the first pulse voltage and the second pulse voltage can be set to a pulse width exceeding 10 ms.

  Thereafter, a third pulse voltage having the same polarity and opposite polarity as the first pulse voltage is applied to the power cable to release the residual charge (third voltage applying means), and the power cable after the residual charge is released A reference pulse voltage having the same waveform and the same polarity as the second pulse voltage is applied (reference pulse voltage applying means).

  Then, if there is a difference between the second current value when the initial residual charge is released and the reference current value when the reference pulse voltage is applied, it is assumed that the charge remains in the deteriorated portion. Judge that the cable has deteriorated. That is, the deterioration of the power cable is determined based on the second current value and the reference current value (determination means).

  A water tree deterioration detection device for a power cable will be described with reference to FIG. FIG. 1 shows a schematic configuration (circuit configuration) of a water cable deterioration detection device for a power cable using a pulse voltage according to an embodiment of the present invention.

  As shown in the figure, the water tree degradation detection device (degradation detection device) 11 includes a first application mechanism 12 including a first voltage application unit and a third voltage application unit, a second voltage application unit, and a reference pulse voltage. It is constructed by a second application mechanism 13 that constitutes the application means.

  The 1st application mechanism 12 has the 1st switch 21, the 2nd switch 22, the 3rd switch 23, and the 4th switch 24, and the 4th switch 24 is provided in the CV cable 6 side as a sample. The first switch 21 is connected to a first resistor 25a and a first power supply 25b whose negative side is grounded, and the second switch 22 is connected to a second resistor 26a and a second power source 26b provided on the positive side, and the first power source 25b. The second power source 26b is a DC power source in which a positive electrode and a negative electrode are connected to the opposite polarity.

  A third resistor 27 is provided on the anti-ground side of the third switch 23, and the opposite side of the fourth switch 24 to the CV cable 6 is grounded via the fourth resistor 28. A first capacitor 29 is provided between the third resistor 27 and the fourth resistor 28.

  On the other hand, the 2nd application mechanism 13 has the 5th switch 15, the 6th switch 16, and the 7th switch 17, and the 7th switch 17 is provided in the CV cable 6 side. The fifth switch 15 is connected to a fifth resistor 18 a and a fifth power source 18 b whose positive side is grounded, and a sixth resistor 19 is provided on the opposite side of the sixth switch 16. The opposite side of the seventh switch 17 from the CV cable 6 is grounded via the seventh resistor 20. A second capacitor 30 is provided between the sixth resistor 19 and the seventh resistor 20.

  Based on FIGS. 2 and 3, the basic operation of the deterioration detection device 11 and the state of charge will be described. FIG. 2 shows the change over time in the power application state of the power cable deterioration detection method using the pulse voltage according to one embodiment of the present invention, and FIG. 3 shows the concept of charge discharge.

  As shown in FIG. 2, the first pulse voltage (negative charge accumulation pulse) with a pulse width of 0.1 ms to 10 ms (the upper limit can exceed 10 ms) is applied to the CV cable 6 to charge. While accumulating, the electric charge accumulated by grounding is discharged (first voltage applying means). If water tree deterioration has occurred in the CV cable 6, electric charges remain accumulated at the deteriorated portion.

  As shown in FIG. 3, by the application of the first pulse voltage, charges are accumulated in the undegraded portion 7 (dotted line) and the water tree degraded portion 8 of the CV cable 6, and the charges accumulated in the portion 7 due to grounding. 7a is released. The charges 8a and 8b of the water tree degradation portion 8 remain accumulated.

  As shown in FIG. 2, after the electric charge accumulated by the ground is released, the second pulse voltage (positive polarity) having a pulse width of 0.1 ms to 10 ms (the upper limit can exceed 10 ms) is applied to the CV cable 6. A depolarizing pulse) is applied to release an initial residual charge that is a part of the charge accumulated in the deteriorated portion (second voltage applying means). A current value at the time of releasing the initial residual charge by application of the second pulse voltage is measured (second current value: determination means).

  As shown in FIG. 3, by application of the second pulse voltage, a part of the charge 8a accumulated in the water tree degradation portion 8, that is, the initial residual charge in the portion adjacent to the portion 7 not degraded ( A one-dot chain line) is emitted. Then, the current value at this time is measured.

  Thereafter, as shown in FIG. 2, the third pulse voltage (positive charge discharging pulse) having the same waveform as the first pulse voltage but opposite in polarity is applied to the CV cable 6, and the remaining accumulated in the deteriorated portion. The charge (residual charge) is released (third voltage applying means).

  As shown in FIG. 3, by applying the third pulse voltage, the remaining charge 8b (two-dot chain line) accumulated in the water tree degradation site 8 is released. Then, the current value at this time is measured.

  As shown in FIG. 2, a reference pulse voltage (positive reference pulse) having the same waveform and polarity as the second pulse voltage is applied to the CV cable 6 after the residual charge has been released (reference pulse voltage applying means). . The current value due to the application of the reference pulse voltage is measured (reference current value: determination means). If all the residual charges are released by applying the third pulse voltage, the reference current value becomes zero.

  Then, if there is a difference between the second current value when the initial residual charge is released and the reference current value when the reference pulse voltage is applied, it is assumed that the charge remains in the deteriorated portion and the CV It is determined that the cable 6 has deteriorated. That is, the presence or absence of deterioration of the CV cable 6 is determined based on the second current value and the reference current value (determination means).

  Based on FIG. 4 and FIG. 5, the state of the switch in the application of the first pulse voltage, the second pulse voltage, the third pulse voltage, and the reference pulse voltage will be described.

  FIG. 4 shows the change over time of the switch operation, and FIG. 5 shows the relationship between the pulse width and the detected charge amount. 4A is a time chart of the switching state of the switch when the first pulse voltage is applied, and FIG. 4B is the time of the switching state of the switch when the second pulse voltage or the reference pulse voltage is applied. FIG. 4C is a time chart of the open / close state of the switch when the third pulse voltage is applied.

  The opening / closing state of the switch when the first pulse voltage is applied will be described.

  As shown in FIG. 4A, between time t1 and time t2, the first switch 21 connected to the first power supply 25b whose negative electrode side is grounded is closed, and negative charge is accumulated in the first capacitor 29. . After the first switch 21 is opened at time t2, the fourth switch 24 is closed, so that the voltage of the first capacitor 29 can be applied.

  From time t3 to time t4, the third switch 23 is closed, and a voltage (pulse voltage) is applied to the CV cable 6 while the third switch 23 is closed. Then, the pulse width is set by setting the capacitance of the first capacitor 29 and the CV cable 6 and the fourth resistor 28, and a pulse voltage (negative positive charge accumulation pulse) is applied for a short time. At time t5, the fourth switch 24 is opened, and the state in which a voltage can be applied to the CV cable 6 ends.

  By the operation of the switch shown in FIG. 4A, a desired time (time set according to the capacitance of the first capacitor 29 and the CV cable 6 and the fourth resistance 28 from time t3 to time t4). In the meantime, a pulse voltage (first pulse voltage) is applied, charges are accumulated in the CV cable 6, and charges accumulated by the ground are released.

  The switching state of the switch when applying the second pulse voltage or the reference pulse voltage will be described.

  As shown in FIG. 4B, between time t11 and time t12, the fifth switch 15 connected to the fifth power source 18b whose positive electrode side is grounded is closed, and positive charge is stored in the second capacitor 30. . After the fifth switch 15 is opened at time t12, the seventh switch 17 is closed, and the voltage of the second capacitor 30 can be applied.

  Between time t13 and time t14, the sixth switch 16 is closed, and a voltage (pulse voltage) is applied to the CV cable 6 while the sixth switch 16 is closed. The pulse width is set by setting the capacitance of the second capacitor 30 and the CV cable 6 and the seventh resistor 20, and a pulse voltage is applied for a very short time. At time t15, the seventh switch 17 is opened, and the state in which a voltage can be applied to the CV cable 6 ends.

  By the operation of the switch shown in FIG. 4B, a desired time (a time set in accordance with the capacitance of the second capacitor 30 and the CV cable 6 and the seventh resistor 20 between time t13 and time t14). ), The second pulse voltage is applied to release the initial residual charge, or the reference pulse voltage is applied after the residual charge is released. A current value by applying the second pulse voltage and a current value by applying the reference pulse voltage are measured.

  When the pulse width of the second pulse voltage or the reference pulse voltage is set to 10 ms, 10 ms corresponds to a half cycle of a commercial AC voltage of 50 Hz. As shown in FIG. 5, the amount of charge detected increases as the pulse width increases. When the pulse width is longer than 1 ms, the detected charge amount hardly increases, so the upper limit of the pulse width is not limited to 10 ms.

  For this reason, in this embodiment, the pulse width of the second pulse voltage or the reference pulse voltage is set to 1 ms to 10 ms, for example, 1 ms. Thereby, the current value can be reliably measured with the minimum power.

  The opening / closing state of the switch when the third pulse voltage is applied will be described.

  As shown in FIG. 4C, between time t21 and time t22, the second switch 22 connected to the second power supply 26b whose positive electrode side is grounded is closed, and positive charge is accumulated in the first capacitor 29. . After the second switch 22 is opened at time t22, the fourth switch 24 is closed, and the voltage of the first capacitor 29 can be applied.

  Between time t23 and time t24, the third switch 23 is closed, and a voltage (pulse voltage) is applied to the CV cable 6 while the third switch 23 is closed. Then, the pulse width is set by setting the capacitance of the first capacitor 29 and the CV cable 6 and the fourth resistor 28, and a pulse voltage (positive charge discharging pulse) is applied for a short time. At time t25, the fourth switch 24 is opened, and the state in which a voltage can be applied to the CV cable 6 ends.

  FIG. 6 shows the waveform of the current value of the CV cable 6 in which no water tree deterioration has occurred, and FIG. 7 shows the waveform of the current value of the CV cable 6 in which water tree deterioration has occurred.

  In the deterioration detection apparatus 11 described above, the first pulse voltage is applied to the CV cable 6 to accumulate charges, and after the charges accumulated by the ground are discharged, the second pulse voltage is applied. If water tree deterioration has occurred in the CV cable 6, the initial residual charge of the residual charges accumulated in the deteriorated portion is released, and the second current value is measured. Thereafter, by applying a reference pulse voltage, a reference current value associated with the discharge of the residual charge accumulated in the deteriorated portion after the initial residual charge is released is measured.

  If there is a difference between the second current value and the reference current value, it is determined that the initial residual charge is present and the water tree degradation portion 8 is present in the CV cable 6, and the second current value and the reference current value are determined. If there is no difference, it is determined that there is no initial residual charge and the CV cable 6 does not have the water tree degradation portion 8.

  For this reason, the existence of the water tree deterioration portion 8 of the CV cable 6 (water tree deterioration of the CV cable 6) can be performed in a very short time by simply measuring the difference between the second current value and the reference current value without increasing the cost. Occurrence) can be accurately determined.

  Then, the occurrence of water tree deterioration is determined based on the signal of the difference between the reference current value after the residual charge (many charges) is released by the application of the third pulse voltage and the second current value. The difference in current value is increased, the signal output can be increased, and the occurrence of water tree deterioration can be easily determined.

  That is, when water tree degradation does not occur in the CV cable 6, there is no difference between the second current value and the reference current value, so that only the value of the current value due to the application of the first pulse voltage is shown in FIG. A waveform 31 is obtained. When water tree degradation has occurred in the CV cable 6, there is a difference between the second current value and the reference current value, and therefore, as shown in FIG. The waveform 32 having a value corresponding to 1 is a synthesized waveform.

A specific example of use of the deterioration detection device 11 will be described with reference to FIGS. FIG. 8 shows a specific configuration (circuit configuration) of an apparatus for carrying out a method for detecting water tree deterioration of a power cable using a pulse voltage according to an embodiment of the present invention, and FIG. 9 shows that water tree deterioration has occurred. FIG. 10 shows a waveform of a current value when measuring a CV cable 6 in which water tree deterioration has occurred.

  As shown in FIG. 8, a CV cable 6 that needs to detect water tree deterioration is connected to the deterioration detection device 11 via an ammeter 34. A CV cable 35 having the same capacitance as that of the CV cable 6 without water tree deterioration is connected to the ammeter 34 in a state opposite to the CV cable 6.

  Since the CV cable 6 and the CV cable 35 are connected to the ammeter 34 in the reverse direction, when a pulse voltage is applied, a waveform of a current value corresponding to the accumulated charge (waveform 31 in FIGS. 6 and 7) Is offset.

  When the water tree deterioration has not occurred in the CV cable 6, as shown in FIG. 9, the waveform of the current value corresponding to the accumulated charge is canceled and the waveform does not appear, and the second current value and the reference current value are The waveform of the current value corresponding to the difference value does not appear. That is, no waveform corresponding to the current appears even when a pulse voltage is applied.

  When water tree degradation has occurred in the CV cable 6, as shown in FIG. 10, the waveform of the current value corresponding to the accumulated charge is canceled and the waveform does not appear, and the second current value and the reference current value A waveform 32 of the current value corresponding to the difference value appears. That is, only the current value waveform 32 based on the discharge of the electric charge accumulated in the water tree degradation portion 8 appears.

  For this reason, it is possible to detect only an electrical signal related to water tree degradation by simply measuring the difference between the second current value and the reference current value, and to detect water tree degradation without incurring costs. Can be done accurately.

A reference example provided with an open / close switch will be described with reference to FIGS.

  FIG. 11 shows a main configuration of a water tree deterioration detecting device for a power cable provided with an open / close switch, and FIG. 12 shows a schematic configuration in a state applied to detection of water tree deterioration of a three-phase cable. The same members as those shown in FIGS. 8 to 10 are denoted by the same reference numerals.

  The deterioration detection apparatus 11 (see FIG. 11) includes connection lines 65 and 66 connected to the CV cable 6 via the ammeter 34. The connection lines 65 and 66 are connected to the ammeter 34 in the reverse direction. Has been. One connection line 65 (upper side in the figure) is provided with an open / close switch 61. For example, a CV cable 6 having a water tree degradation portion 8 is connected to the connection line 65 via an open / close switch 61, and for example, a CV cable having a water tree degradation portion 8 is connected to the connection line 66. 6 is connected.

  By applying the accumulation pulse voltage (first pulse voltage) with the open / close switch 61 open, charges are accumulated in the water tree degradation portion 8 of the CV cable 6 connected to the connection line 66, and the connection is established. Electric charges are not accumulated in the water tree degradation portion 8 of the CV cable 6 connected to the line 65.

  By closing the open / close switch 61 and applying a pulse voltage for discharge (second pulse voltage), the charge accumulated in the water tree degradation site 8 of the CV cable 6 connected to the connection line 66 is released, Since no charge is accumulated in the water tree deterioration portion 8 of the CV cable 6 connected to the connection line 65, no charge is released even when a pulse voltage for discharge (second pulse voltage) is applied.

  Thereby, the CV cable 6 connected to the connection line 65 can be used as a CV cable in which water tree deterioration has not occurred, and the water tree deterioration of the CV cable 6 connected to the connection line 66 can be determined. .

  By opening and closing the open / close switch 61 and applying a pulse voltage for accumulation (first pulse voltage) and a pulse voltage for discharge (second pulse voltage), the CV cable 6 in which water tree degradation has occurred It is possible to use a CV cable that does not cause water tree degradation. For this reason, even when the state of water tree deterioration of the CV cable is not known, it is possible to determine the water tree deterioration of the CV cable using a CV cable in which no water tree deterioration has occurred.

  A specific use example will be described with reference to FIG.

  The case where the water tree deterioration of the cable 50 including the three-phase CV cables 51, 52, 53 is determined will be described. Assume that water tree degradation has occurred in all of the CV cables 51, 52, 53.

  The CV cable 51 is connected to the connection line 65, the CV cable 52 is connected to the connection line 66, and the open / close switch 61 is opened. By applying the accumulation pulse voltage (first pulse voltage), charges are accumulated in the water tree degradation portion of the CV cable 52 connected to the connection line 66, and the CV cable 51 connected to the connection line 65 Charges are not accumulated at the site of water tree degradation.

  By closing the open / close switch 61 and applying a discharge pulse voltage (second pulse voltage), the charge accumulated in the water tree deterioration portion of the CV cable 52 is released, and the water tree deterioration of the CV cable 51 is reduced. Since no charge is accumulated in the portion, no charge is released even when a pulse voltage for emission (second pulse voltage) is applied.

  As a result, the CV cable 52 connected to the connection line 65 is used as a CV cable in which no water tree deterioration has occurred, and the water tree deterioration of the CV cable 52 connected to the connection line 66 can be determined.

  The connection of the CV cables 51, 52, 53 to the connection lines 65, 66 is sequentially changed, the open / close switch 61 is opened / closed, the pulse voltage for accumulation (first pulse voltage), and the pulse voltage for discharge (first) By applying the two-pulse voltage), the CV cables 51, 52, and 53 in which water tree deterioration has occurred can be used in a state using a CV cable in which water tree deterioration has not occurred.

  For this reason, even when the state of water tree deterioration of the CV cables 51, 52, 53 of the cable 50 is not known, the CV cable 51 of the cable 50 is used in a state where a CV cable having no water tree deterioration is used on site. It becomes possible to judge the water tree deterioration of 52 and 53.

According to the power tree water tree deterioration detection method using the pulse power cable deterioration detection device 11 described above, it is possible to accurately determine the water tree deterioration of the CV cable 6 in an extremely short time without increasing the cost. become. In addition, detection of a signal is easier than when an AC voltage is applied.

INDUSTRIAL APPLICABILITY The present invention can be used in the industrial field of a method for detecting water tree deterioration of a power cable using a pulse voltage for detecting water tree deterioration of the power cable.

6, 35 CV cable 11 Water tree degradation detector (degradation detector)
12 1st application mechanism 13 2nd application mechanism 15 5th switch 16 6th switch 17 7th switch 18a 5th resistor 18b 5th power supply 19 6th resistor 20 7th resistor 21 1st switch 22 2nd switch 23 3rd switch 24 4th switch 25a 1st resistance 25b 1st power supply 26a 2nd resistance 26b 2nd power supply 27 3rd resistance 28 4th resistance 29 1st capacitor 30 2nd capacitor 34 Ammeter

Claims (1)

Applying the first pulse voltage with a pulse width of 0.1 ms or more to the power cable to accumulate the charge, and discharging the accumulated charge by grounding,
A second pulse voltage having a pulse width of 0.1 ms or more is applied to the power cable after the charge is released to release the initial residual charge,
Applying a third pulse voltage having the same waveform as the first pulse voltage but having the opposite polarity to the power cable after the initial residual charge has been released to release the residual charge,
When applying a reference pulse voltage having the same waveform and the same polarity as the second pulse voltage to the power cable after the residual charge is released by applying the third pulse voltage ,
When the first pulse voltage, the second pulse voltage, the third pulse voltage, and the reference pulse voltage are applied to a power cable that needs to detect water tree deterioration, and the second pulse voltage is applied. While measuring the current value corresponding to the difference between the second current value and the reference current value when the reference pulse voltage is applied,
The first pulse voltage, the second pulse voltage, the third pulse voltage, and the reference pulse are connected to a power cable that needs to detect water tree deterioration and has a capacitance that is equal in capacitance and does not exist. A voltage is applied to detect a current value opposite to the current value corresponding to the difference between the second current value and the reference current value;
Waveform of the current value of the power cable that needs to detect water tree degradation and the waveform of the current value of the power cable that has the same capacitance and no water tree degradation as the power cable that needs to detect water tree degradation Offset
When the current value waveform appears, it is detected that the water tree deterioration is detected on the assumption that the current value waveform based on the discharge of the electric charge accumulated in the power cable that needs to detect the water tree deterioration appears. A method for detecting water tree degradation in power cables using a pulse voltage to be applied.

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