CN116819394A - Power cable aging diagnosis monitoring method and system - Google Patents
Power cable aging diagnosis monitoring method and system Download PDFInfo
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- CN116819394A CN116819394A CN202311069081.6A CN202311069081A CN116819394A CN 116819394 A CN116819394 A CN 116819394A CN 202311069081 A CN202311069081 A CN 202311069081A CN 116819394 A CN116819394 A CN 116819394A
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- 230000002159 abnormal effect Effects 0.000 claims abstract description 81
- 238000012423 maintenance Methods 0.000 claims abstract description 58
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- 238000001931 thermography Methods 0.000 claims abstract description 23
- 238000010586 diagram Methods 0.000 claims abstract description 16
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention provides a power cable aging diagnosis monitoring method and a system, which relate to the field of cable monitoring, wherein the method comprises the following steps: monitoring the grounding current of the outer sheath of the cable, and judging whether the grounding current of the outer sheath is abnormal; when the grounding current of the outer protective layer is judged to be abnormal, the fault position of the cable is positioned; starting temperature monitoring equipment corresponding to the fault position of the cable; determining the type of cable faults according to a thermal imaging diagram fed back by temperature monitoring equipment; if the type of the cable fault is a cable body fault, monitoring the test current of the cable when the specified voltage is connected; and analyzing the aging degree of the cable according to the test current, and generating a corresponding maintenance strategy. After the faults are determined, the current between the cable core and the spiral steel belt is further measured, and the larger the test current is, the more serious the aging degree is, the reasonable maintenance strength is correspondingly set, the manpower resources are distributed and maintained in a targeted mode, and the maintenance efficiency is improved.
Description
Technical Field
The invention relates to the technical field of cable monitoring, in particular to a power cable aging diagnosis monitoring method and system.
Background
With the increasing application of power cables in urban network transformation, the cables are used as main bodies of urban power supply networks, and the reliability of the operation of the cables is directly related to the stability of the whole power system. In the operation environment, the cable is affected by various factors such as electricity, heat, chemistry, machinery and the like in the environment, and the aging phenomenon is unavoidable.
After the power cable is aged, the problems of the aging state, the operation reliability and the like of the power cable become key problems focused by operation and maintenance staff, and the problems of whether the insulation condition of the power cable is good, whether defects and faults exist, how to diagnose and position the power cable and the like are all hot problems to be solved urgently at present.
The existing monitoring methods are divided into online monitoring and offline monitoring, but no matter which monitoring method is used for positioning local faults, the fault occurrence position or the aging degree of the cable where the fault is located is difficult to determine, and reasonable overhaul and maintenance strategies are not easy to set.
Disclosure of Invention
The invention aims to solve the problems that the existing method is difficult to determine the aging degree of the cable where the fault is located, and is not beneficial to setting a reasonable overhaul and maintenance strategy.
In order to solve the above problems, in one aspect, the present invention provides a power cable aging diagnosis and monitoring method, including:
monitoring the grounding current of the outer sheath of the cable, and judging whether the grounding current of the outer sheath is abnormal;
when the grounding current of the outer protective layer is judged to be abnormal, the fault position of the cable is positioned;
starting temperature monitoring equipment corresponding to the fault position, and monitoring the fault position;
determining the fault type of the cable according to the thermal imaging diagram fed back by the temperature monitoring equipment;
if the fault type of the cable is a cable body fault, monitoring the test current of the cable when the cable is connected with a specified voltage;
and analyzing the aging degree of the cable according to the test current to generate a corresponding maintenance strategy.
Optionally, the monitoring the outer sheath grounding current of the cable, and determining whether the outer sheath grounding current is abnormal includes:
respectively acquiring the grounding currents of the outer protective layer of the cable at a plurality of positions;
calculating unbalance of the outer sheath grounding current at a plurality of positions;
and when the unbalance degree of the grounding current of the outer sheath at a plurality of positions is larger than a preset threshold value, judging that the grounding current of the outer sheath of the cable is abnormal.
Optionally, when the external sheath grounding current is determined to be abnormal, locating the fault position of the cable includes:
when the outer sheath grounding current is judged to be abnormal, positioning a monitoring point where the outer sheath grounding current is abnormal first, and marking the monitoring point as an adjacent abnormal monitoring point, wherein a plurality of monitoring points are arranged on each cable, and a monitoring section is formed between two adjacent monitoring points;
determining monitoring points forming the same monitoring section with the adjacent abnormal monitoring points according to the positions of the adjacent abnormal monitoring points, and marking the monitoring points as adjacent normal monitoring points;
the monitoring segment between the adjacent abnormal monitoring point and the adjacent normal monitoring point is marked as a fault monitoring segment, wherein the fault location is within the fault monitoring segment.
Optionally, the determining the fault type of the cable according to the thermal imaging diagram fed back by the temperature monitoring device includes:
marking an abnormal temperature region with the temperature greater than the limiting temperature according to the temperature distribution condition of the thermal imaging diagram fed back by the temperature monitoring equipment;
counting the number and the area of the abnormal temperature areas;
judging whether the number of the abnormal temperature areas is larger than a preset number or whether the area of the abnormal temperature areas is larger than a preset area;
and when the number of the abnormal temperature areas is larger than the preset number or the area of the abnormal temperature areas is larger than the preset area, judging that the fault type of the cable is the cable body fault.
Optionally, if the fault type of the cable is a cable body fault, monitoring the test current of the cable when the specified voltage is turned on includes:
if the fault type of the cable is a cable body fault, controlling a change-over switch to act, connecting the specified voltage into a circuit formed by a cable core and a spiral copper strip of the fault monitoring section, and acquiring the test current;
and controlling the change-over switch to switch, disconnecting the appointed voltage which is introduced between the cable core and the spiral copper strip, and directly connecting the cable and the spiral copper strip to obtain the release current.
Optionally, analyzing the aging degree of the cable according to the test current, and generating a corresponding repair and maintenance strategy includes:
different specified voltages are connected into a circuit formed by the cable core and the spiral copper strip, so that a plurality of test currents and a plurality of release currents are obtained;
calculating the power-on index of the cable according to the test current and the release current corresponding to the same designated voltage;
calculating the aging degree value of the cable according to the energizing indexes corresponding to different specified voltages;
and determining the aging stage of the cable according to the aging degree value, and correspondingly generating the maintenance strategy.
Optionally, the calculating according to the test current and the release current corresponding to the same specified voltage, the energizing index of the cable includes:
；
wherein K is the energization index, ε is the vacuum dielectric constant, U is the specified voltage applied,for the test current +.>Average value of>For releasing theDischarge current->Average value of (2).
Optionally, the calculating the aging degree value of the cable according to the energizing indexes corresponding to different specified voltages includes:
；
wherein N represents the aging degree value,and->And respectively representing the energizing indexes corresponding to different specified voltages.
Optionally, determining, according to the aging degree value, an aging stage where the cable is located, and correspondingly generating the repair and maintenance policy includes:
judging the aging stage of the cable according to the aging degree value and the unbalance degree of the grounding current of the outer protective layer;
when the aging degree value is equal to 1, judging that the cable is normal, and generating a maintenance strategy of a normal maintenance period;
when the aging degree value is larger than 1 and smaller than a first threshold value or the unbalance degree of the grounding current of the outer protective layer is larger than the preset threshold value, judging that the cable is in an initial aging stage or an intermediate aging stage, generating a maintenance strategy for shortening a maintenance period, and adding position information of the fault monitoring section and the aging degree value of the cable into the maintenance strategy;
and when the aging degree value is larger than the first threshold value, judging that the cable is in an aging end stage, generating a power failure maintenance strategy, and adding the position information of the fault monitoring section and the aging degree value of the cable into the power failure maintenance strategy.
In another aspect, the present invention further provides a power cable aging diagnosis monitoring system, including:
the grounding current monitoring module is used for monitoring the grounding current of the outer sheath of the cable and judging whether the grounding current of the outer sheath is abnormal or not;
the fault positioning module is used for positioning the fault position of the cable when the ground current of the outer protective layer is abnormal;
the thermal imaging analysis module is used for starting the temperature monitoring equipment corresponding to the fault position and monitoring the fault position; the fault type of the cable is determined according to the thermal imaging diagram fed back by the temperature monitoring equipment;
the cable body testing module is used for monitoring the testing current of the cable when the specified voltage is connected if the fault type of the cable is a cable body fault;
and the aging analysis module is used for analyzing the aging degree of the cable according to the test current and generating a corresponding maintenance strategy.
Compared with the prior art, the invention has the following beneficial effects:
according to the power cable aging diagnosis monitoring method and system provided by the invention, the grounding current of the outer protective layer of the cable is monitored to judge whether the grounding current of the outer protective layer is abnormal or not, so that destructive testing on the cable is not needed, and the normal operation of the cable is not influenced; when the grounding current of the outer protective layer is judged to be abnormal, the fault position of the cable is positioned, at the moment, the approximate area where the fault position of the cable is positioned is initially positioned, then a temperature monitoring device corresponding to the fault position is started to monitor the fault position, and the fault type of the cable and the accurate position of the cable fault are determined according to a thermal imaging diagram fed back by the temperature monitoring device; if the fault type of the cable is a cable body fault, monitoring a test current of the cable when the cable is connected with a specified voltage, further measuring the current between a cable core and a spiral steel belt after the fault is determined, analyzing the aging degree of the cable according to the test current, and generating a corresponding maintenance strategy, wherein the larger the test current is, the more serious the aging degree is, the corresponding reasonable maintenance force is set, the manpower resources are distributed and maintained in a targeted mode, and the maintenance efficiency is improved.
Drawings
FIG. 1 shows a schematic diagram of a cable in an embodiment of the invention;
fig. 2 is a schematic flow chart of a power cable aging diagnosis monitoring method according to an embodiment of the invention.
Reference numerals illustrate: 1. a cable core; 2. an inner semiconductive layer; 3. an insulating layer; 4. an outer semiconductive layer; 5. spiral copper strips; 6. a filler; 7. a center-fill; 8. an inner sheath; 9. armoring a flat steel belt; 10. and an outer protective layer.
Detailed Description
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. While the invention is susceptible of embodiment in the drawings, it is to be understood that the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided to provide a more thorough and complete understanding of the invention. It should be understood that the drawings and embodiments of the invention are for illustration purposes only and are not intended to limit the scope of the present invention.
It should be understood that the various steps recited in the method embodiments of the present invention may be performed in a different order and/or performed in parallel. Furthermore, method embodiments may include additional steps and/or omit performing the illustrated steps. The scope of the invention is not limited in this respect.
The term "including" and variations thereof as used herein are intended to be open-ended, i.e., including, but not limited to. The term "based on" is based at least in part on. The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "alternative embodiments". Related definitions of other terms will be given in the description below. It should be noted that the terms "first," "second," and the like herein are merely used for distinguishing between different devices, modules, or units and not for limiting the order or interdependence of the functions performed by such devices, modules, or units.
It should be noted that references to "one", "a plurality" and "a plurality" in this disclosure are intended to be illustrative rather than limiting, and those skilled in the art will appreciate that "one or more" is intended to be construed as "one or more" unless the context clearly indicates otherwise.
Fig. 1 shows a schematic structure of a cable, in which three or even a plurality of cables can be included in each cable, each cable includes a cable core 1 disposed at a central position, the cable core 1 is externally covered with a multi-layer structure, an inner semiconductive layer 2, an insulating layer 3, an outer semiconductive layer 4 and a spiral copper strip 5 are sequentially disposed from inside to outside, a central filler 7 is further disposed in the middle of the three cables, the three cables are covered by an inner sheath 8, a filler 6 is filled between the three cables and the inner sheath 8 and the central filler 7, the outer layer of the inner sheath 8 is sequentially covered with a flat steel tape armor 9 and an outer sheath 10, the cable is only shown in the figure, in other cable structures, more or fewer cables can be covered in the inner sheath 8, and the structure of each cable can be specifically designed and adjusted according to different functions.
Fig. 2 is a schematic flow chart of a power cable aging diagnosis monitoring method according to an embodiment of the present invention, where the power cable aging diagnosis monitoring method includes:
s1: monitoring the grounding current of the outer sheath of the cable, and judging whether the grounding current of the outer sheath is abnormal;
when the cables are laid, leads are arranged at the starting end, the joint and the position of the terminating end of each cable, the outer protective layer is grounded at each position by the leads, and a current monitoring instrument is connected to the grounding leads and has the function of uploading data, such as an intelligent ammeter, an intelligent ammeter and the like. When the cable is aged, the insulating layer 3 is corroded, or in the long-time operation process, the cable is electrified and heated, so that the insulating layer 3 is aged, when current is introduced into the cable core 1, local high voltage can puncture the insulating layer 3 to enable current to overflow, the outer protective layer 10 is affected, the accumulated charges of the outer protective layer 10 change, current can be formed in the process of leading the charges into the ground, once the cable is aged, the current in the cable core 1 is unstable due to charge interaction with the ground, however, under normal conditions, three-phase current in the cable is stable and cannot leak, therefore, the grounding current cannot generate larger fluctuation, and whether the grounding current uploaded by the current monitoring instrument at a plurality of positions is consistent or whether the grounding current at a plurality of positions is in a balanced state can be judged, so that whether the cable is in a normal condition can be judged.
S2: when the grounding current of the outer protective layer is judged to be abnormal, the fault position of the cable is positioned;
when the abnormal ground current is monitored, the position of the cable fault can be positioned by checking the position of the abnormal ground current; for example, since the current monitoring meters are provided at the cable connection sites, which corresponds to dividing one long cable into a plurality of segments, when current is conducted from one end to the other, ground current starts to be abnormal from the position where the cable fails, so that the fault position can be located. It should be noted that the fault location located at this time is located between two monitoring points, and the fault location cannot be located completely accurately. Because the local position of the cable is abnormal in current, the fault range is gradually enlarged in the process of transmitting the current through the cable, and the aging speed of the cable is accelerated.
S3: starting temperature monitoring equipment corresponding to the fault position, and monitoring the fault position;
when the cable normally operates, the temperature distribution in the cable is even, the temperature is slightly higher than the temperature in the middle of the cable only at the cable connection position, because the accumulation and the transmission blockage of charges can be generated at the cable connection position, but when the cable is aged, the situation that the high voltage breaks through the insulating layer 3 to cause the current to flow out can be generated at the local position on the cable, at the moment, the charges can be accumulated at the position where the current leakage occurs, the temperature is higher than the temperature at the normal position of the cable, and at the moment, the specific position of the fault can be identified through temperature detection.
It should be noted that, a plurality of temperature monitoring devices are arranged at different positions of the cable, the temperature monitoring devices need to operate to collect thermal imaging images, then the specific fault positions are analyzed and positioned by analyzing the received thermal imaging images, if the temperature monitoring devices are always in the operation process, a relatively high memory and a relatively high processor are required to be configured for the system, and the service life of the monitoring devices can be shortened when the temperature monitoring devices are operated for a long time, so that the temperature monitoring devices are set to be started only when the cable is monitored to be possibly abnormal.
S4: determining the fault type of the cable according to the thermal imaging diagram fed back by the temperature monitoring equipment;
specifically, when the thermal imaging image is analyzed, local high-temperature places can be found, the local high-temperature places can be fault positions, but not all the high-temperature places are fault positions, because the temperature of the cable connection positions is slightly higher than that of the middle part of a normal cable, if the high-temperature positions are uniformly and regularly distributed, the high-temperature positions can be cable connection positions, when the high-temperature positions in the thermal imaging image are unevenly distributed, and the number of the high-temperature areas is obviously more than that of the cable connection positions, the fault in the cable body can be judged at the moment.
S5: if the fault type of the cable is a cable body fault, monitoring the test current of the cable when the cable is connected with a specified voltage;
when the body of the cable breaks down, the ageing degree of the cable cannot be judged at this moment, whether current exists between the cable core 1 and the spiral copper strip 5 or not and the loss degree of the current can be further measured, because ageing is mainly that the insulating layer 3 loses protection effect, or because flaws exist between the insulating layer 3 and the inner semiconductive layer 2 and the outer semiconductive layer 4 in the cable production manufacturing process, in the process of long-term current conveying, charges can be accumulated at flaws, the flaw area is expanded to the insulating layer 3, and once high voltage or external electric field interference is encountered, the flaw area is broken down, so that the insulating layer 3 is damaged and aged. Therefore, a low voltage can be introduced into the cable, the current introduced into the cable is smaller, charge aggregation can be generated when the current passes through the defect area, when the defect area and the insulating layer 3 are broken down easily (namely, the ageing degree is serious), the current can reach the spiral copper strip 5 through the inner semiconductive layer 2, the insulating layer 3 and the outer semiconductive layer 4, so that the spiral copper strip 5 is electrified, the cable core 1 and the spiral copper strip 5 are communicated with a power supply through wires from the outside, a current loop can be formed between the cable core 1 and the spiral copper strip 5, the ageing degree of the cable can be reflected by measuring the current formed between the cable core 1 and the spiral copper strip 5, because the worse the ageing is, the worse the insulating effect of the insulating layer 3 is, and the larger the current formed between the cable core 1 and the spiral copper strip 5 is.
S6: and analyzing the aging degree of the cable according to the test current to generate a corresponding maintenance strategy.
When the cable is normal, the cable can be maintained according to a normal overhaul period (such as one-year inspection); if the cable is found to have ageing, but the ageing is not serious, when the cable is in the early or middle stage of ageing, more problems of the cable can be prevented by shortening the overhaul period, for example, the overhaul period is shortened to 9 months or half a year, and more attention is paid to the ageing position; when the cable is severely aged and is in the end stage of aging, the cable is likely to be severely damaged at any time so that the cable cannot work, and power failure is required for maintenance or replacement, and particularly maintenance and replacement of an aged area are paid attention.
In the embodiment, by monitoring the grounding current of the outer protective layer of the cable, whether the grounding current of the outer protective layer is abnormal or not is judged, destructive testing is not needed to be carried out on the cable, and normal operation of the cable is not affected; when the grounding current of the outer protective layer is judged to be abnormal, the fault position of the cable is positioned, at the moment, the approximate area where the fault position of the cable is positioned is initially positioned, then a temperature monitoring device corresponding to the fault position is started to monitor the fault position, and the fault type of the cable and the accurate position of the cable fault are determined according to a thermal imaging diagram fed back by the temperature monitoring device; if the fault type of the cable is a cable body fault, monitoring a test current of the cable when the cable is connected with a specified voltage, further measuring the current between the cable core 1 and the spiral copper strip 5 after determining that the fault exists, analyzing the aging degree of the cable according to the test current, and generating a corresponding maintenance strategy, wherein the larger the test current is, the more serious the aging degree is, the corresponding reasonable maintenance force is set, the manpower resources are distributed and maintained in a targeted mode, and the maintenance efficiency is improved.
In one embodiment of the present invention, the monitoring the outer sheath grounding current of the cable, and determining whether the outer sheath grounding current is abnormal includes:
respectively acquiring the grounding currents of the outer protective layer of the cable at a plurality of positions;
specifically, a current monitoring instrument is arranged at a plurality of connection points of the cable, and the magnitude of the grounding current is monitored in real time, so that a plurality of grounding currents of the outer protective layer at different positions can be obtained at the same time.
Calculating unbalance of the outer sheath grounding current at a plurality of positions;
and when the unbalance degree of the grounding current of the outer sheath at a plurality of positions is larger than a preset threshold value, judging that the grounding current of the outer sheath of the cable is abnormal.
Specifically, when calculating the unbalance of the grounding current of the outer sheath at a plurality of positions, the grounding current of the previous monitoring point can be subtracted from the grounding current of the next monitoring point, then the current difference between the two adjacent grounding currents is obtained, the current difference is statistically analyzed, the fluctuation range of the current difference is seen, the fluctuation value is obtained by subtracting the maximum value of the current difference from the minimum value of the current difference, the unbalance of the current fluctuation can be obtained by dividing the fluctuation value by the minimum value of the current difference, and when the unbalance exceeds a preset threshold value, the abnormal grounding current of the outer sheath of the cable is judged. By the method, the abnormal condition of the cable can be timely and rapidly monitored, the monitoring is accurate, the false alarm condition is reduced, and unnecessary repair or maintenance is avoided.
In one embodiment of the present invention, when it is determined that the outer sheath grounding current is abnormal, locating the fault location of the cable includes:
when the outer sheath grounding current is judged to be abnormal, positioning a monitoring point where the outer sheath grounding current is abnormal first, and marking the monitoring point as an adjacent abnormal monitoring point, wherein a plurality of monitoring points are arranged on each cable, and a monitoring section is formed between two adjacent monitoring points;
specifically, the current is transmitted from one end to the other end in the cable, the current value in the cable is at a normal value before the fault position, but when the current passes through the fault position, the current is leaked, so that the grounding current is large, the change of the current can be obviously detected at the moment, when the charge is leaked, the grounding current at the fault point is most obviously changed, the position of the monitoring point is probably not just at the position of the fault point, but the current change is larger at the monitoring point which is closer to the fault point, so that the front-back change of the grounding current can be compared, and the monitoring point corresponding to the grounding current with the large change is adjacent to the abnormal monitoring point.
Determining monitoring points forming the same monitoring section with the adjacent abnormal monitoring points according to the positions of the adjacent abnormal monitoring points, and marking the monitoring points as adjacent normal monitoring points; specifically, since two monitoring points constitute one monitoring segment, when an adjacent abnormal monitoring point is located, an adjacent normal monitoring point corresponding to the adjacent abnormal monitoring point can be found.
The monitoring segment between the adjacent abnormal monitoring point and the adjacent normal monitoring point is marked as a fault monitoring segment, wherein the fault location is within the fault monitoring segment. Because a monitoring point may belong to a plurality of monitoring segments, when the monitoring segment where the fault point is located is not determined, the monitoring segments where the adjacent abnormal monitoring points belong can be temporarily marked as fault monitoring segments, so that the range of the fault position is preliminarily limited, the range of further monitoring and analysis is reduced, and the analysis calculation amount is reduced.
In one embodiment of the present invention, the determining, according to the thermal imaging diagram fed back by the temperature monitoring device, the fault type of the cable includes:
marking an abnormal temperature region with the temperature greater than the limiting temperature according to the temperature distribution condition of the thermal imaging diagram fed back by the temperature monitoring equipment; in general, according to a production test of a cable, the temperature generated during normal operation of the cable does not exceed a certain temperature, the temperature is set to be a limiting temperature, when the local temperature generated during operation of the cable exceeds the limiting temperature, abnormal operation of the cable in the local area is indicated, the abnormal areas are marked, the areas are all places needing more attention during daily maintenance, and the time for one-by-one investigation during maintenance is reduced and the maintenance efficiency is improved by transmitting marking information to maintenance staff.
Counting the number and the area of the abnormal temperature areas; it should be noted that, even if the cable is operating normally, a local temperature rise is inevitably generated at the cable joint position, at this time, the temperature at the cable joint is slightly higher than the temperature in the middle of the cable, at this time, the cable joint cannot be determined as a fault area, but the number of cable joints is recorded when the cable is built, so when the number or area of the abnormal temperature points exceeds the recorded number of cable joints or the total area of cable joints, an additional high temperature area is represented, namely, the cable is faulty.
Judging whether the number of the abnormal temperature areas is larger than a preset number or whether the area of the abnormal temperature areas is larger than a preset area;
when the number of the abnormal temperature areas is larger than the preset number or the area of the abnormal temperature areas is larger than the preset area, judging that the fault type of the cable is the cable body fault;
when the number of the abnormal temperature areas is smaller than or equal to the preset number and the area of the abnormal temperature areas is smaller than or equal to the preset area, when the number of the abnormal temperature areas is reduced, the fact that some connecting positions do not work or do not work normally is indicated, and at the moment, the type of the faults of the cable can be judged to be cable terminal faults or cable connector faults or the cable can be judged to work normally.
In this embodiment, the fault type of the cable is determined by analyzing the thermal imaging chart, when the cable body has an abnormal temperature region, the trend that the cable body starts to age is illustrated, the cable with a problem can be accurately and specifically screened, the overhaul range of maintenance personnel is reduced, the working efficiency is improved, at this time, further analysis on the aging degree of the cable is needed, and a reasonable maintenance strategy is arranged.
In one embodiment of the present invention, if the fault type of the cable is a cable body fault, monitoring the test current of the cable when the specified voltage is turned on includes:
if the fault type of the cable is a cable body fault, controlling a change-over switch to act, connecting the specified voltage into a circuit formed by a cable core and a spiral copper strip of the fault monitoring section, and obtaining the test current, wherein the change-over switch is arranged in a passage formed by the cable core and the spiral copper strip, the fixed end of the change-over switch is directly connected with the cable core, one end of a first movable end of the change-over switch is connected with one end of a power supply, the other end of the power supply is connected with the spiral copper strip, one end of a second movable end of the change-over switch is directly connected with the spiral copper strip, one end of the first movable end and one end of the second movable end are connected with each other and connected with each other in parallel, the current detection meter is connected in series between a grounding point and the spiral copper strip, the current detection meter continuously transmits the tested current to a system, and the system can obtain continuous current data. Since the amount of charge leakage or the amount of charge loss due to aging of the cable is smaller than the current value in the case of high voltage and large current, a smaller voltage can be applied to the cable so as to clearly observe the leakage of charge, and the measured current value is smaller, the change is sensitive, and the degree of difference between the front and rear changes can be observed.
And controlling the change-over switch to switch, disconnecting the appointed voltage which is introduced between the cable core and the spiral copper strip, and directly connecting the cable and the spiral copper strip to obtain the release current.
Specifically, when the switch switches the specified voltage into the circuit where the cable core and the spiral copper belt are positioned, the power supply generates charges to move in the cable, the current value in the cable is not a constant value, but is larger in the initial stage of voltage switching, when the charges move to a fault position, charge aggregation is generated, and when the current aggregation is not increased to a certain extent in a fault area, the current gradually decreases and tends to be stable; after the control change-over switch is switched, the power supply is not connected between the cable core 1 and the spiral copper strip 5 any more, at the moment, the charges in the cable start to recover to a free state, and still generate charge movement to form smaller current, the redundant charges can be led out of the circuit through the grounding, the charges accumulated at the fault position can flow to the grounding end from the fault position, and at the moment, the measured release current can be gradually reduced until the measured release current becomes zero; therefore, when the test current and the release current are obtained, the time for the power supply to be connected into the circuit where the cable core and the spiral copper belt are positioned is maintained until the test current is stable, the charge accumulation amount at the fault position reaches the maximum, and the obtained release current is relatively accurate. Under the normal condition of the cable, the charge cannot be accumulated, only a small amount of charge is reserved in the cable or the charge cannot be reserved, the release current is small and the existence time is short, and the set release current can be zero; when the cable fails, after the protection of the insulating layer 3 is reduced, charges can accumulate in the failure area, and the formed release current is larger and the existing time is prolonged.
In one embodiment of the present invention, the analyzing the aging degree of the cable according to the test current, and generating the corresponding repair and maintenance policy includes:
different specified voltages are connected into a circuit formed by the cable core and the spiral copper strip, so that a plurality of test currents and a plurality of release currents are obtained; the power supply of the circuit where the access cable core 1 and the spiral copper strip 5 are located can be set as a variable power supply, and the voltage value can be adjusted according to the requirement, for example, the designated voltage can be set to be different values such as 1V, 3V or 4V.
Calculating the power-on index of the cable according to the test current and the release current corresponding to the same designated voltage; the current index indicates how easily the electric charge in the cable flows.
In particular, the method comprises the steps of,；
wherein K is the energization index, epsilon is the vacuum dielectric constant, and U is the applied specified voltage; the test current is a continuously varying value,for the test current +.>Average value of (2); in addition, the release current is also a continuously varying value, < >>For the release current +.>Average value of (2). Epsilon is a constant and the specified voltage U is also a constant, so the current index is only related to the average value of the current.
Calculating the aging degree value of the cable according to the energizing indexes corresponding to different specified voltages; because the higher the voltage, the stronger the potential that is formed, the shorter the residence time of the charge at the fault and the reduced amount of accumulation at the fault, so that the cable energization index becomes large. When the cable is not aged and is normal, no charge aggregation phenomenon is generated, and no matter how large the voltage is, the power-on index is kept at a relatively stable level, so that the aging degree value is always kept at about 1; when the cable starts to age, a problem occurs at certain positions in the cable, when a current passes through a fault point, charge aggregation is formed at the fault point, and the more serious the aging degree is, the smaller the voltage is, the larger the released current is; the lower the ageing, the higher the voltage and the lower the discharge current.
In particular, the ageing process of the cableThe degree value is:the method comprises the steps of carrying out a first treatment on the surface of the Wherein N represents the ageing degree value, < >>And->And respectively representing the energizing indexes corresponding to different specified voltages. For example, the power-on index corresponding to the specified voltage of 3V is divided by the power-on index corresponding to the specified voltage of 2V to obtain a ratio, which refers to the aging degree of the cable.
And determining the aging stage of the cable according to the aging degree value, and correspondingly generating the maintenance strategy.
In this embodiment, determining, according to the aging degree value, an aging stage in which the cable is located, and correspondingly generating the repair and maintenance policy includes:
judging the aging stage of the cable according to the aging degree value and the unbalance degree of the grounding current of the outer protective layer;
when the aging degree value is equal to 1, judging that the cable is normal, and generating a maintenance strategy of a normal maintenance period;
when the aging degree value is larger than 1 and smaller than a first threshold value or the unbalance degree of the grounding current of the outer protective layer is larger than the preset threshold value, judging that the cable is in an initial aging stage or an intermediate aging stage, generating a maintenance strategy for shortening a maintenance period, and adding position information of the fault monitoring section and the aging degree value of the cable into the maintenance strategy;
when the aging degree value is larger than the first threshold value, judging that the cable is in an aging end stage, generating a power failure maintenance strategy, if the cable is continuously used at this time, the cable is possibly damaged and stopped at any time, and the cable is required to be subjected to power failure maintenance, and the position information of the fault monitoring section and the aging degree value of the cable are added in the power failure maintenance strategy.
In another embodiment of the present invention, there is also provided a power cable aging diagnosis monitoring system including:
the grounding current monitoring module is used for monitoring the grounding current of the outer sheath of the cable and judging whether the grounding current of the outer sheath is abnormal or not;
the fault positioning module is used for positioning the fault position of the cable when the ground current of the outer protective layer is abnormal;
the thermal imaging analysis module is used for starting the temperature monitoring equipment corresponding to the fault position and monitoring the fault position; the fault type of the cable is determined according to the thermal imaging diagram fed back by the temperature monitoring equipment;
the cable body testing module is used for monitoring the testing current of the cable when the specified voltage is connected if the fault type of the cable is a cable body fault;
and the aging analysis module is used for analyzing the aging degree of the cable according to the test current and generating a corresponding maintenance strategy.
The power cable aging diagnosis and monitoring system has similar technical effects to the power cable aging diagnosis and monitoring method, and is not described in detail herein.
Although the invention is disclosed above, the scope of the invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications will fall within the scope of the invention.
Claims (10)
1. A power cable aging diagnosis monitoring method, characterized by comprising:
monitoring the grounding current of the outer sheath of the cable, and judging whether the grounding current of the outer sheath is abnormal;
when the grounding current of the outer protective layer is judged to be abnormal, the fault position of the cable is positioned;
starting temperature monitoring equipment corresponding to the fault position, and monitoring the fault position;
determining the fault type of the cable according to the thermal imaging diagram fed back by the temperature monitoring equipment;
if the fault type of the cable is a cable body fault, monitoring the test current of the cable when the cable is connected with a specified voltage;
and analyzing the aging degree of the cable according to the test current to generate a corresponding maintenance strategy.
2. The power cable aging diagnosis and monitoring method according to claim 1, wherein the monitoring of the outer sheath grounding current of the cable, determining whether the outer sheath grounding current is abnormal, comprises:
respectively acquiring the grounding currents of the outer protective layer of the cable at a plurality of positions;
calculating unbalance of the outer sheath grounding current at a plurality of positions;
and when the unbalance degree of the outer sheath grounding current at a plurality of positions is larger than a preset threshold value, judging that the outer sheath grounding current of the cable is abnormal.
3. The power cable aging diagnostic monitoring method according to claim 2, wherein when it is determined that the outer sheath ground current is abnormal, locating the fault location of the cable comprises:
when the outer sheath grounding current is judged to be abnormal, positioning a monitoring point where the outer sheath grounding current is abnormal first, and marking the monitoring point as an adjacent abnormal monitoring point, wherein a plurality of monitoring points are arranged on each cable, and a monitoring section is formed between two adjacent monitoring points;
determining monitoring points forming the same monitoring section with the adjacent abnormal monitoring points according to the positions of the adjacent abnormal monitoring points, and marking the monitoring points as adjacent normal monitoring points;
the monitoring segment between the adjacent abnormal monitoring point and the adjacent normal monitoring point is marked as a fault monitoring segment, wherein the fault location is within the fault monitoring segment.
4. The method for diagnosing and monitoring aging of a power cable according to claim 1, wherein the determining the type of the fault of the cable according to the thermal imaging diagram fed back by the temperature monitoring device comprises:
marking an abnormal temperature region with the temperature greater than the limiting temperature according to the temperature distribution condition of the thermal imaging diagram fed back by the temperature monitoring equipment;
counting the number and the area of the abnormal temperature areas;
judging whether the number of the abnormal temperature areas is larger than a preset number or whether the area of the abnormal temperature areas is larger than a preset area;
and when the number of the abnormal temperature areas is larger than the preset number or the area of the abnormal temperature areas is larger than the preset area, judging that the fault type of the cable is the cable body fault.
5. The power cable aging diagnosis monitoring method according to claim 3, wherein if the kind of fault of the cable is a cable body fault, monitoring a test current of the cable when a specified voltage is turned on comprises:
if the fault type of the cable is a cable body fault, controlling a change-over switch to act, connecting the specified voltage into a circuit formed by a cable core and a spiral copper strip of the fault monitoring section, and acquiring the test current;
and controlling the change-over switch to switch, disconnecting the appointed voltage which is introduced between the cable core and the spiral copper strip, and directly connecting the cable and the spiral copper strip to obtain the release current.
6. The method of claim 5, wherein analyzing the aging degree of the cable according to the test current, and generating a corresponding repair maintenance strategy comprises:
different specified voltages are connected into a circuit formed by the cable core and the spiral copper strip, so that a plurality of test currents and a plurality of release currents are obtained;
calculating the power-on index of the cable according to the test current and the release current corresponding to the same designated voltage;
calculating the aging degree value of the cable according to the energizing indexes corresponding to different specified voltages;
and determining the aging stage of the cable according to the aging degree value, and correspondingly generating the maintenance strategy.
7. The power cable aging diagnosis monitoring method according to claim 6, wherein the calculation based on the test current and the release current corresponding to the same specified voltage, the power index of the cable includes:
；
wherein K is the energization index, ε is the vacuum dielectric constant, U is the specified voltage applied,for the test current +.>Average value of>For the release current +.>Average value of (2).
8. The power cable aging diagnosis monitoring method according to claim 6, wherein the calculating the aging degree value of the cable according to the energization indexes corresponding to the different specified voltages includes:
；
wherein N represents the aging degree value,and->And respectively representing the energizing indexes corresponding to different specified voltages.
9. The method for diagnosing and monitoring aging of a power cable according to claim 6, wherein determining an aging stage in which the cable is located according to the aging degree value, and correspondingly generating the repair and maintenance policy, comprises:
judging the aging stage of the cable according to the aging degree value and the unbalance degree of the grounding current of the outer protective layer;
when the aging degree value is equal to 1, judging that the cable is normal, and generating a maintenance strategy of a normal maintenance period;
when the aging degree value is larger than 1 and smaller than a first threshold value or the unbalance degree of the grounding current of the outer protective layer is larger than the preset threshold value, judging that the cable is in an initial aging stage or an intermediate aging stage, generating a maintenance strategy for shortening a maintenance period, and adding position information of the fault monitoring section and the aging degree value of the cable into the maintenance strategy;
and when the aging degree value is larger than the first threshold value, judging that the cable is in an aging end stage, generating a power failure maintenance strategy, and adding the position information of the fault monitoring section and the aging degree value of the cable into the power failure maintenance strategy.
10. A power cable degradation diagnostic monitoring system, comprising:
the grounding current monitoring module is used for monitoring the grounding current of the outer sheath of the cable and judging whether the grounding current of the outer sheath is abnormal or not;
the fault positioning module is used for positioning the fault position of the cable when the ground current of the outer protective layer is abnormal;
the thermal imaging analysis module is used for starting the temperature monitoring equipment corresponding to the fault position and monitoring the fault position; the fault type of the cable is determined according to the thermal imaging diagram fed back by the temperature monitoring equipment;
the cable body testing module is used for monitoring the testing current of the cable when the specified voltage is connected if the fault type of the cable is a cable body fault;
and the aging analysis module is used for analyzing the aging degree of the cable according to the test current and generating a corresponding maintenance strategy.
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