JP2023039678A - Deterioration diagnosis method and device of high-voltage cable - Google Patents

Abstract

To specify not only the deterioration degree but also the type and spot of deterioration for a high-voltage cable.SOLUTION: A deterioration diagnosis method of a high-voltage cable comprises: separating both ends of a conductor of a high-voltage cable from a power system when performing deterioration diagnosis of the age-deteriorated high-voltage cable as it is in the laid state, and making a dielectric tangent diagnostic device and a partial discharge diagnostic device connectable in a switchable manner to the high-voltage cable; determining the deterioration degree from dielectric tangent obtained by the dielectric tangent diagnostic device connected to the high-voltage cable; performing partial discharge diagnosis by the partial discharge diagnostic device connected to the high-voltage cable by being switched from the dielectric tangent diagnostic device when the determined deterioration degree is equal to or greater than a prescribed degree; determining the deterioration of the entire cable when the partial discharge is not detected in the partial discharge diagnosis; and determining the deterioration in a partial discharge spot specified in the partial discharge diagnosis when the partial discharge is detected in the partial discharge diagnosis.SELECTED DRAWING: Figure 2

Description

The present invention relates to a deterioration diagnosis method for preventing electrical accidents caused by insulation deterioration of a high-voltage cable, and a deterioration diagnosis apparatus used in the method.

Steelworks have many high voltage cables that are 30 to 40 years old and are still in use. The degree and manner of deterioration of high-voltage cables vary greatly depending on the laying conditions, such as buried, culvert (underdrain), and aerial. If the insulation of high-voltage cables deteriorates and causes ground faults or short circuits, it will not only affect production but also cause fires.

Insulation deterioration of high-voltage cables is caused by poor insulation due to improper construction of cable joints, water tree deterioration of the insulation layer in the case of CV cables (cross-linked polyethylene insulated vinyl sheath cables), and OF cables (oil-filled cables). If there is, there is insulation paper deterioration.

Patent Literature 1 discloses a diagnostic device and diagnostic method for determining the degree of progress of deterioration of a power cable using the dielectric loss tangent (tan δ) method. Dielectric loss tangent (tan δ) is defined as tan δ = Ir/Ic = 1/ωCRp, where Ic is the current flowing through the ideal capacitor C and Ir is the current (energy loss) flowing through the parasitic resistance Rp in parallel with the ideal capacitor. is the number to be used. In this diagnostic device, both ends of the conductor of an installed power cable in which both ends of the conductor are connected to the electric power system via another cable and the separating device and the sheath is grounded are electrically separated from the electric power system by the separating device. and measure the dielectric loss tangent between the separating device to which one end of the conductor is connected and the sheath with an ordinary measuring instrument, and then correct the measured value by considering the components of other cables and separating devices. , the dielectric loss tangent of only the power cable is obtained, and degradation diagnosis is performed from the dielectric loss tangent.

Patent Document 2 discloses an orientation system and an orientation method for measuring the partial discharge of a power cable using a partial discharge diagnosis method and locating the location where the partial discharge occurs. In this orientation system, a pair of electrode plates are wound around at least two locations separated in the longitudinal direction of a CV cable whose both ends of the conductor are connected to the electric power system. Then, the high-frequency partial discharge signal propagated through the CV cable is detected by each pair of electrode plates, and from the detection time difference of those partial discharge signals and the propagation speed of the partial discharge signal obtained in advance, the location where the partial discharge occurs is determined. Oriented.

JP 2017-122738 A JP 2014-035243 A

However, although the degree of deterioration of the cable can be determined by measuring the dielectric loss tangent (tan δ), it is not possible to specify the type of deterioration, such as water tree deterioration or joint deterioration, and the location of deterioration. On the other hand, in the detection of the partial discharge signal, although it is possible to identify the location of deterioration of the cable, it is not possible to identify the degree or type of deterioration such as water tree deterioration in which partial discharge does not occur.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for diagnosing deterioration of a high voltage cable and a deterioration diagnosing device used in the method, which can specify not only the degree of deterioration of a cable but also the type and location of deterioration.

A method for diagnosing deterioration of a high-voltage cable according to the present invention, which aims to solve the above problems advantageously, comprises:
When diagnosing the deterioration of a high-voltage cable that has deteriorated over time while it is still installed,
Disconnecting both ends of the conductor of the high-voltage cable from the power system to enable switching connection between a dielectric loss tangent (tan δ) diagnostic device and a partial discharge diagnostic device for the high-voltage cable,
Determining the degree of deterioration from the dielectric loss tangent obtained by the dielectric loss tangent diagnostic device connected to the high voltage cable,
If the determined degree of deterioration is equal to or higher than a predetermined level, the partial discharge diagnosis is performed by the partial discharge diagnosis device connected to the high-voltage cable by switching from the dielectric loss tangent diagnosis device,
If partial discharge is not detected in the partial discharge diagnosis, it is determined that the entire cable has deteriorated due to water tree deterioration or insulating paper deterioration,
When partial discharge is detected by the partial discharge diagnosis, it is determined that deterioration such as insulation failure or insulation breakdown occurs at the partial discharge location specified by the partial discharge diagnosis.

Further, the high-voltage cable deterioration diagnosis device of the present invention is
A device for use in the method for diagnosing deterioration of a high-voltage cable that has deteriorated over time, while diagnosing the deterioration of the high-voltage cable in an installed state,
A dielectric loss tangent (tan δ) diagnostic device and a partial discharge diagnostic device are provided so that both ends of the conductor can be switched and connected to the high-voltage cable disconnected from the power system.

According to the method for diagnosing deterioration of a high-voltage cable of the present invention, when diagnosing the deterioration of a high-voltage cable that has deteriorated over time while it is still installed, both ends of the conductor of the high-voltage cable are separated from the power system, and the dielectric loss tangent ( tan δ) A diagnostic device and a partial discharge diagnostic device can be switched and connected, and first, the degree of deterioration is determined from the dielectric loss tangent obtained by the dielectric loss tangent diagnostic device connected to the high-voltage cable, and the determined degree of deterioration is greater than or equal to a predetermined value. Then, switch from the dielectric loss tangent diagnostic device to the partial discharge diagnostic device connected to the high-voltage cable and perform partial discharge diagnosis. If a partial discharge is detected in the partial discharge diagnosis, it is judged as deterioration such as insulation failure or insulation breakdown at the specified partial discharge diagnosis, so the deterioration of the high voltage cable Not only the degree of deterioration, but also the type and location of deterioration can be identified, which enables determination of renewal of the high-voltage cable, so that electrical accidents caused by deterioration of the high-voltage cable can be prevented. In addition, since the deteriorated portion can be specified, the replacement range of the high-voltage cable can be limited, and the replacement cost can be reduced.

According to the high-voltage cable deterioration diagnosis device of the present invention used in the above-described high-voltage cable deterioration diagnosis method, both ends of the conductor can be switched and connected to the high-voltage cable disconnected from the power system, and the dielectric loss tangent (tan δ) Since the diagnostic device and the partial discharge diagnostic device are provided, the high-voltage cable deterioration diagnostic method can be implemented, and not only the degree of deterioration of the high-voltage cable but also the type and location of deterioration can be specified. Since it is possible to determine whether the cable has been renewed, it is possible to prevent electrical accidents caused by deterioration of the high-voltage cable. In addition, since the deteriorated portion can be specified, the replacement range of the high-voltage cable can be limited, and the replacement cost can be reduced.

In the apparatus for diagnosing deterioration of a high-voltage cable of the present invention, the degree of deterioration is determined from the dielectric loss tangent obtained by the dielectric loss tangent diagnostic apparatus, and the presence or absence of detection of partial discharge in the partial discharge diagnostic apparatus and the detection location. and/or a determination device for determining the type of deterioration of the In this way, at least one of the degree of deterioration and the type of deterioration can be determined automatically and objectively, which is preferable because maintenance of the high voltage cable can be performed rationally. .

Further, in the apparatus for diagnosing deterioration of a high-voltage cable of the present invention, the dielectric loss tangent (tan δ) diagnosing apparatus and the partial discharge diagnosing apparatus are switched and connected to the high-voltage cable disconnected from the electric power system at both ends of the conductor. It may have a device. This is preferable because the switching connection between the dielectric loss tangent (tan δ) diagnostic device and the partial discharge diagnostic device can be easily and quickly performed by the switching connection device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of a high-voltage cable deterioration diagnosis device according to an embodiment of the present invention, which is used in a high-voltage cable deterioration diagnosis method according to an embodiment of the present invention; 4 is a flow chart showing a diagnostic procedure in the method for diagnosing deterioration of a high-voltage cable according to the embodiment; It is a graph which illustrates the result of the dielectric tangent (tan-delta) diagnosis in the deterioration diagnosis method of the high voltage cable of the said embodiment. 4 is a graph illustrating a damped oscillation voltage for partial discharge diagnosis in the method for diagnosing deterioration of a high-voltage cable according to the embodiment; It is a graph which illustrates the result of the partial discharge diagnosis in the deterioration diagnosis method of the high voltage cable of the said embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing the configuration of a high-voltage cable deterioration diagnosis apparatus according to an embodiment of the present invention, which is used in a high-voltage cable deterioration diagnosis method according to an embodiment of the present invention.

As shown in FIG. 1, the apparatus for diagnosing deterioration of a high-voltage cable according to this embodiment disconnects cable heads 1a provided at both ends of conductors of a high-voltage cable 1 to be diagnosed that has deteriorated over time from a high-voltage switchboard (not shown) of a power system. A tan δ diagnostic unit 2 as a dielectric loss tangent (tan δ) diagnostic device and a partial discharge diagnostic device for diagnosing the deterioration of the high-voltage cable 1 in the state of laying such as buried, culvert (underdrain), or aerial. a partial discharge diagnostic unit 3, a cable head 1a at one end of the conductor of the high-voltage cable 1 and a probe 4 detachably attached to the sheath grounding wire 1b for grounding one end of the sheath around the conductor, and the probe 4 a switching connection device 5 for switching and connecting the cable head 1a and the sheath grounding wire 1b to the tan δ diagnostic unit 2 and the partial discharge diagnostic unit 3, respectively, via electric circuits.

In addition, the apparatus for diagnosing deterioration of high-voltage cables of this embodiment includes a main diagnostic apparatus 6 as a determination apparatus, which is composed of a normal computer that operates based on a program given in advance. The high-voltage cable 1 has a cable joint 1c in the middle, and the tan δ diagnosis unit 2, the partial discharge diagnosis unit 3, and the switching connection device 5 each have a ground wire for grounding the grounded part of the circuit. are doing.

The tan delta diagnostic unit 2 has a known configuration, for example, as described in FIG. is applied and the dielectric loss tangent (tan δ) is measured by a normal method, and then the deterioration diagnosis is performed from the measured dielectric loss tangent. Since the cable head 1a is detached from the high-voltage switchboard in this case, it is not necessary to correct the measured dielectric loss tangent for other cables.

The partial discharge diagnostic unit 3 has a known configuration such as that described in FIG. Apply a damped and oscillating test voltage between the cable head 1a at one end of each of the conductors and the sheath grounding wire 1b, monitor the generation of a partial discharge pulse signal by the test voltage, and check for the presence or absence of a pulse signal due to partial discharge. Then, based on the time difference between the direct wave of the pulse signal and the reflected wave from the other end of the conductor of the high-voltage cable 1, etc., the point of occurrence is located, and deterioration diagnosis is performed.

Then, the main diagnostic device 6 sends a switching signal to the switching connection device 5 via the control cable 7 to connect the cable head 1a and the sheath grounding wire 1b of the high-voltage cable 1 to the tan δ diagnostic unit 2 and the partial discharge diagnostic unit 3, respectively. Along with the switching connection, the tan δ diagnostic unit 2 and the partial discharge diagnostic unit 3 are caused to diagnose the deterioration of the high-voltage cable 1, and the diagnostic results are collected via the communication cable 8 to determine where to update the high-voltage cable 1. , the judgment result is output on the screen display or the like.

The high-voltage cable deterioration diagnosis method of the embodiment described above uses the high-voltage cable deterioration diagnosis device of the embodiment described above to diagnose deterioration of the high-voltage cable 1 according to the diagnostic procedure shown in the flowchart of FIG.

That is, the main diagnostic device 6 sends a switching signal to the switching connection device 5 to first connect the cable head 1a and the sheath grounding wire 1b of the high-voltage cable 1 to the tan δ diagnostic unit 2, and in step S1, the communication cable 8 is connected. tan delta diagnosis unit 2 to perform tan delta diagnosis. In this tan δ diagnosis, the tan δ diagnosis unit 2 applies, as test voltages, three-step AC voltages of 0.5 U ₀ , 1.0 U ₀ , and 1.5 U ₀ where the cable rated voltage of the high-voltage cable 1 is U ₀ . to measure tan δ (dielectric loss tangent). Then, the measured tan δ value is sent to the main diagnostic device 6 via the communication cable 8 . Based on the value of tan δ, the main diagnostic device 6 determines whether or not the degree of deterioration of the high-voltage cable 1 is "good" in the next step S2 according to the tan δ diagnostic criteria defined by IEEE shown in Table 1 below. .

If the result of determination in step S2 is "good", no abnormality due to deterioration of the diagnosed high-voltage cable 1 is recognized. , the tan δ diagnosis is performed periodically for follow-up, and the process returns to step S1.

On the other hand, if the result of determination in step S2 is not "good", the main diagnostic device 6 next determines in step S4 whether the degree of deterioration of the high-voltage cable 1 is "needs caution". _{For example} ^, in the measurement results ^illustrated in _FIG . ^If this is applied to the judgment criteria in Table 1, Δtanδ=10 and the average value at 1.0 U ₀ is 13, so the judgment result is "need attention".

If the result of determination in step S4 is "caution required", the insulation deterioration of the high-voltage cable 1 is progressing, but it is considered that the insulation breakdown will not occur immediately. , the process advances to step S5 to increase the frequency of tan δ diagnosis to follow-up, and returns to step S1.

On the other hand, if the result of determination in step S4 is not a "caution required" determination, then in step S6, the main diagnostic device 6 determines whether the degree of deterioration of the high voltage cable 1 is "severely deteriorated". .

If the result of determination in step S6 is "severely deteriorated", it is considered that water tree deterioration and insulating paper deterioration have spread over the entire cable. The entirety of the high-voltage cable 1 to be determined will be updated." is output.

If the result of determination in step S6 is not a "severely deteriorated" determination, the main diagnostic device 6 sends a switching signal to the switching connection device 5, and then the cable head 1a of the high voltage cable 1 and the sheath grounding wire 1b are connected. are switched and connected to the partial discharge diagnosis unit 3, and in step S8, a command is sent to the partial discharge diagnosis unit 3 via the communication cable 8 to cause the partial discharge diagnosis to be performed.

In this partial discharge diagnosis, as shown in FIG. 4, a partial discharge diagnosis unit 3 is applied between a cable head 1a at one end of a conductor of a high-voltage cable 1 and a sheath grounding wire 1b. is applied to monitor whether or not the partial discharge pulse signal P due to the test voltage T is detected between the cable head 1a and the sheath grounding wire 1b. is applied, i.e., after the test voltage T exceeds a predetermined level at the rise of each wave, when the pulse signal P of the partial discharge is detected within a predetermined time, as illustrated in FIG. The time required for the pulse signal (direct wave) to reach the cable head 1a directly from the partial discharge position after application, and the time for the conductor of the high-voltage cable 1 to travel from the partial discharge position in the direction opposite to the cable head 1a after the test voltage is applied. The time difference between the time when the pulse signal (reflected wave) arrives at the cable head 1a after being reflected at the end or the like is obtained for each wave, and the location of occurrence (the length of the conductor from the cable head 1a to the location of occurrence) is determined from the time difference. is located, and the diagnostic result is sent to the main diagnostic device 6 via the communication cable 8 . For example, in the diagnosis result illustrated in FIG. ) and the pulse signal of the third wave (level P3) are both about 500 m, and it is estimated that the diagnostic result is appropriate.

Based on the diagnosis result, the main diagnostic device 6 determines in the next step S9 whether or not a pulse signal of partial discharge by the test voltage is detected between the cable head 1a and the sheath grounding wire 1b, and determines whether or not the partial discharge is detected. If the pulse signal is not detected, as in the case of the "severe deterioration" determination, it is considered that water tree deterioration and insulating paper deterioration have spread over the entire cable. The entire high-voltage cable 1 will be updated." is output.

On the other hand, in step S9, when the pulse signal of the partial discharge due to the above test voltage is detected, the main diagnostic device 6 proceeds to step S10 and states "partially update the part where the discharge is detected". is output along with the location of occurrence of partial discharge determined by the partial discharge diagnostic unit 3 . Then, the same deterioration diagnosis is performed for the cable head 1a at one end of the other conductor among the plurality of conductors of the high-voltage cable 1 as well.

Therefore, according to the high-voltage cable deterioration diagnosis device of this embodiment and the high-voltage cable deterioration diagnosis method of this embodiment using the same, not only the degree of deterioration of the high-voltage cable 1 but also the type and location of deterioration can be specified. As a result, it is possible to determine whether or not the high-voltage cable 1 should be renewed. Further, since the deteriorated portion can be specified, the replacement range of the high-voltage cable 1 can be limited, and the replacement cost can be reduced.

Moreover, according to the high-voltage cable deterioration diagnosis device of this embodiment and the high-voltage cable deterioration diagnosis method of this embodiment using the same, the degree of deterioration from the tan δ obtained by the tan δ diagnosis unit 2 is determined, and the partial discharge Since the main diagnostic device 6 determines whether or not partial discharge is detected in the diagnostic unit 3 and the type of deterioration from the detection point, the determination of the degree of deterioration and the determination of the type of deterioration can be performed automatically and objectively. Therefore, the maintenance of the high-voltage cable 1 can be rationally performed.

Furthermore, according to the apparatus for diagnosing deterioration of a high-voltage cable of this embodiment and the method of diagnosing deterioration of a high-voltage cable of this embodiment using the apparatus, the tan δ diagnosis unit 2 and the partial discharge diagnosis unit 3 are connected to the electric power system at both ends of the conductor. Since the switching connection device 5 is provided for switching connection to the high-voltage cable 1 disconnected from the main body, the switching connection between the tan δ diagnostic unit 2 and the partial discharge diagnostic unit 3 can be easily and quickly performed by the switching connection device 5.

Although the above has been described based on the illustrated embodiments, the present invention is not limited to the above-described embodiments. Alternatively, the switching connection device 5 may be omitted and the tan δ diagnostic unit 2 and the partial discharge diagnostic unit 3 may be manually switched and connected to the high-voltage cable 1 . Further, the determination by the main diagnostic device 6 may be omitted, and the main diagnostic device 6 may simply cause the tan δ diagnostic unit 2 and the partial discharge diagnostic unit 3 to perform diagnostics and display the results collected from them.

Thus, according to the method for diagnosing deterioration of a high-voltage cable of the present invention, when diagnosing the deterioration of a high-voltage cable that has deteriorated over time while it is still installed, it is possible to specify not only the degree of deterioration of the high-voltage cable, but also the type and location of deterioration. As a result, it is possible to determine whether or not the high-voltage cable should be renewed, so that it is possible to prevent electrical accidents caused by deterioration of the high-voltage cable. In addition, since the deteriorated portion can be specified, the replacement range of the high-voltage cable can be limited, and the replacement cost can be reduced.

According to the high-voltage cable deterioration diagnostic device of the present invention used in the high-voltage cable deterioration diagnostic method, the high-voltage cable deterioration diagnostic method can be implemented. Not only the degree of deterioration of the high-voltage cable, but also the type and location of deterioration can be specified, and the replacement of the high-voltage cable can be determined based on this, so that electrical accidents caused by deterioration of the high-voltage cable can be prevented. In addition, since the deteriorated portion can be specified, the replacement range of the high-voltage cable can be limited, and the replacement cost can be reduced.

1 high-voltage cable 1a cable head 1b sheath grounding wire 1c cable joint 2 tan delta diagnostic unit 3 partial discharge diagnostic unit 4 probe 5 switching connection device 6 main diagnostic device 7 control cable 8 communication cable P pulse signal P1, P2, P3 pulse signal level T test voltage

Claims (4)

When diagnosing the deterioration of a high-voltage cable that has deteriorated over time while it is still installed,
Disconnecting both ends of the conductor of the high-voltage cable from the power system to enable switching connection between the dielectric loss tangent diagnostic device and the partial discharge diagnostic device for the high-voltage cable,
Determining the degree of deterioration from the dielectric loss tangent obtained by the dielectric loss tangent diagnostic device connected to the high voltage cable,
If the determined degree of deterioration is equal to or higher than a predetermined level, the partial discharge diagnosis is performed by the partial discharge diagnosis device connected to the high-voltage cable by switching from the dielectric loss tangent diagnosis device,
If partial discharge is not detected in the partial discharge diagnosis, it is determined that the entire cable is deteriorated,
A method of diagnosing deterioration of a high-voltage cable, wherein when partial discharge is detected in the partial discharge diagnosis, deterioration is determined at a partial discharge location specified in the partial discharge diagnosis. A deterioration diagnosis device used in the method for diagnosing deterioration of a high-voltage cable according to claim 1,
A high-voltage cable deterioration diagnostic device comprising a dielectric loss tangent diagnostic device and a partial discharge diagnostic device capable of switching and connecting both ends of a conductor to the high-voltage cable disconnected from a power system. At least one of determining the degree of deterioration from the dielectric loss tangent obtained by the dielectric loss tangent diagnostic device and determining whether or not partial discharge is detected by the partial discharge diagnostic device and the type of degradation from the detection location is performed. 3. The apparatus for diagnosing deterioration of a high-voltage cable according to claim 2, further comprising a determination device. 4. The apparatus according to claim 2, further comprising a switching connection device for switching and connecting the dielectric loss tangent diagnostic device and the partial discharge diagnostic device to the high-voltage cable disconnected from a power system at both ends of conductors. Deterioration diagnosis device for high-voltage cables.

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