CN113466607A - Three-phase cable intermediate joint moisture state analysis method - Google Patents
Three-phase cable intermediate joint moisture state analysis method Download PDFInfo
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- CN113466607A CN113466607A CN202110549445.5A CN202110549445A CN113466607A CN 113466607 A CN113466607 A CN 113466607A CN 202110549445 A CN202110549445 A CN 202110549445A CN 113466607 A CN113466607 A CN 113466607A
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/11—Locating faults in cables, transmission lines, or networks using pulse reflection methods
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Abstract
The embodiment of the invention provides a three-phase cable intermediate joint damp state analysis method, which comprises the steps of obtaining an initial state positioning spectrogram of each phase of a to-be-detected three-phase cable, loading a simulated working environment on the three-phase cable, repeatedly measuring the to-be-detected three-phase cable at preset time intervals to obtain an intermediate state positioning spectrogram of each phase, analyzing the damp state of the to-be-detected three-phase cable according to the initial state positioning spectrogram and the obtained intermediate state positioning spectrogram of each phase, and obtaining a most-damp joint; and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time. This embodiment passes through many times of measurement on the time scale, can obtain every looks location spectrogram situation of change, and then can detect the cable joint state of weing, and it is more accurate to detect data, can characterize the joint rule of weing.
Description
Technical Field
The invention relates to the technical field of power cable state detection, in particular to a three-phase cable intermediate joint damp state analysis method.
Background
With the continuous promotion of urbanization and large-scale industrial development in China, the electricity consumption of people is increased day by day. In order to meet the demand of people on electric power, compared with the traditional overhead line, the power cable is greatly used in a distribution network due to the advantages of large transmission capacity, no influence of ground and space buildings and the like. The cable intermediate joint is an important component of the cable accessory, but statistics shows that the cable intermediate joint fault accounts for more than 80% of cable accessory faults. The cable joint is the most common and serious type of the cable joint moisture defect, a large amount of sewage is accumulated in a cable laying calandria or an underground tunnel, once the cable joint is potentially damp and cannot be timely removed, and serious cable accidents such as unplanned power failure and the like can be caused.
In the prior art, a frequency domain reflection method and a partial discharge method are often adopted to locate the defects of the power cable. However, most of researches in the prior art are positioning researches on defects of single-phase cable joints, three-core cables are generally adopted for laying of an actual distribution cable system, and due to a complex laying environment, the three-phase moisture degrees at the cable joints of the immersed distribution cables are different, and different moisture states are generated due to different water pressure effects. The research on the damp state of the three-phase cable is beneficial to timely eliminating potential damp, and the damp difference of the three-phase cable can be determined for targeted processing.
However, the prior art does not research on the moisture state and the evolution law of the three-phase cable.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the three-phase cable intermediate joint moisture state analysis method which can analyze the moisture characteristics of the three-phase moisture cable and provide a foundation for field detection and treatment.
The embodiment of the invention provides a method for analyzing the damp state of a three-phase cable intermediate joint, which comprises the following steps:
measuring an initial state positioning spectrogram of each phase cable in the initial state of the three-phase cable to be measured through frequency domain reflection measurement equipment;
loading a simulation working environment on the three-phase cable to be tested;
repeatedly measuring the loaded three-phase cable to be measured after a preset time interval, and obtaining an intermediate state positioning spectrogram of each phase cable;
analyzing the moisture state of the three-phase cable to be tested according to the initial state positioning spectrogram and the obtained intermediate state positioning spectrograms of the phases, and obtaining the most severe connector which is affected with moisture;
and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time.
Preferably, the loading of the simulated working environment on the three-phase cable to be tested specifically includes:
sleeving a hose on the outer side of the three-phase cable to be tested, and adding water with a preset height;
and applying load circulation to two ends of the three-phase cable to be tested.
As a preferred mode, comparing the initial state positioning spectrogram with the newly obtained intermediate state positioning spectrograms of the phases, analyzing the moisture state of the three-phase cable to be tested, and obtaining the most severe connector which is affected with moisture specifically comprises:
acquiring initial state reflection peak data of each phase cable of the three-phase cable to be tested before loading through the initial state positioning spectrogram, wherein the initial state reflection peak data comprises initial state reflection peak values of each joint of each phase cable;
acquiring middle state reflection peak data of each loaded phase cable of the three-phase cable to be detected through a newly acquired middle state positioning spectrogram of each phase, wherein the middle state reflection peak data comprises initial state reflection peaks of each joint of each loaded phase cable;
when the difference between the intermediate state reflection peak value of any joint of the first-phase cable and the initial state reflection peak value of the joint is not smaller than a preset first threshold value, judging that the first-phase cable is in a damp state;
and judging that one connector of one phase cable with the maximum normalized difference value of the intermediate state reflection peak value and the initial state reflection peak value in the three-phase cable to be tested is the most severely affected by damp.
Preferably, the specific moisture states of the most heavily wetted joints include: the damping starting time, the damping saturation time and the damping rate;
the analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint in the preset time specifically comprises the following steps:
acquiring a positioning spectrogram of the joint with the most severe damp within preset time, acquiring a middle state reflection peak of the joint with the most severe damp within the preset time, and drawing the change condition of the middle state reflection peak on a time scale;
when the difference between the middle state reflection peak value of the joint with the most severe tide and the initial state reflection peak value of the joint with the most severe tide is not smaller than a preset second threshold value, recording the time at the moment as the tide starting time, and recording the starting peak value at the moment;
when the change value of the middle state reflection peak value of the joint with the most severe damp does not exceed the preset stable value range and keeps the preset stable time, recording the time as damp saturation time, and recording the saturation peak value at the time;
recording the difference between the initial peak value and the saturation peak value as a peak value difference, and recording the difference between the damping initial time and the damping saturation time as a time difference; the tidal rate is the absolute value of the ratio of the peak difference to the time.
The invention provides a three-phase cable intermediate joint damp state analysis method, which comprises the steps of positioning a spectrogram through an initial state of each phase of a to-be-detected three-phase cable, loading a simulated working environment on the three-phase cable, repeatedly measuring the to-be-detected three-phase cable at preset time intervals to obtain middle state positioning spectrogram data of each phase, analyzing the damp state of the to-be-detected three-phase cable according to the initial state positioning spectrogram and the obtained middle state positioning spectrogram data of each phase, and obtaining a most damp joint; and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time. This embodiment passes through many times of measurement on the time scale, can obtain every looks location spectrogram situation of change, and then can detect the cable joint state of weing, and it is more accurate to detect data, can characterize the joint rule of weing.
Drawings
Fig. 1 is a schematic flow chart of a method for analyzing a moisture state of a three-phase cable intermediate joint according to an embodiment of the present invention;
fig. 2 is a structural diagram of a three-phase cable to be tested according to a method for analyzing a moisture state of a middle joint of the three-phase cable provided by another embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a schematic flow chart of a method for analyzing a moisture state of a three-phase cable intermediate joint provided by an embodiment of the present invention is shown, where the method includes: s101 to S105:
s101, measuring an initial state positioning spectrogram of each phase cable in the initial state of the three-phase cable to be measured through frequency domain reflection measurement equipment;
s102, loading a simulation working environment on the three-phase cable to be tested;
s103, repeatedly measuring the loaded three-phase cable to be measured after a preset time interval, and obtaining intermediate state positioning spectrogram data of each phase cable;
s104, analyzing the moisture state of the three-phase cable to be tested according to the initial state positioning spectrogram and the obtained intermediate state positioning spectrogram data of each phase, and obtaining the most severe moisture joint;
and S105, analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within the preset time.
In the specific implementation of the embodiment, at least two three-phase cables to be measured are connected through an intermediate joint to form a three-phase cable to be measured; when the number of the three-phase cables is two, the number of the intermediate joints of the formed to-be-tested three-phase cables is one, and when the number of the three-phase cables exceeds two, the formed to-be-tested three-phase cables comprise a plurality of intermediate joints.
Measuring an initial state positioning spectrogram of the three-phase cable to be measured in the initial state through frequency domain reflection measurement equipment, wherein the specific process comprises the following steps of:
and determining that the head end of the three-phase cable to be tested is a test end and the tail end of the three-phase cable to be tested is an open circuit. Respectively fixing a test fixture on a cable core and a copper shielding layer, wherein the shielding layer is grounded;
setting test conditions: testing a frequency range f and a point number N; and (4) setting a test frequency range f, wherein the upper limit and the lower limit of the sweep frequency range are required to be set according to the length of the cable to be tested.
And injecting a sweep frequency signal from the cable testing end by using a broadband impedance spectrometer, and collecting a reflected signal at the cable testing end.
Measuring the three phases one by one to finally obtain an input impedance frequency spectrum initial result;
and processing the input impedance spectrum of the head end of the tested cable by using a discrete Fourier transform algorithm, and mapping the processed data into an original distance positioning spectrogram by using a mapping method to obtain the positioning spectrogram of each phase of cable corresponding to the three-phase cable.
Loading simulated working environments including an external working environment and a voltage and current environment actually borne by a three-phase cable on the three phases to be tested;
re-measuring the loaded three-phase cable at preset time intervals to obtain intermediate state positioning spectrograms of the phases, and recording the intermediate state positioning spectrograms obtained each time to obtain intermediate state positioning spectrogram data containing time data;
the preset time interval is generally specifically set according to the detection precision and the damp risk of the three-phase cable, and in this embodiment, as an optimal mode, the preset time interval may be set to be one week;
after the positioning spectrogram is obtained every time, comparing the initial state positioning spectrogram with the newly obtained intermediate state positioning spectrograms of all phases, analyzing the moisture state of the three-phase cable to be tested, and judging the most severe connector which is affected with moisture, wherein the most severe connector is a certain connector of a certain phase cable in the three-phase cable to be tested;
and acquiring a positioning spectrogram of the joint with the most severe damp within a preset time, and analyzing the specific damp state of the joint with the most severe damp.
The embodiment of the invention provides a three-phase cable intermediate joint damp state analysis method, which comprises the steps of obtaining an initial state positioning spectrogram of each phase of a to-be-detected three-phase cable, loading a simulated working environment on the three-phase cable, repeatedly measuring the to-be-detected three-phase cable at preset time intervals, obtaining intermediate state positioning spectrogram data of each phase, analyzing the damp state of the to-be-detected three-phase cable according to the initial state positioning spectrogram and the obtained intermediate state positioning spectrogram data of each phase, and obtaining a most damp joint; and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time. This embodiment passes through many times of measurement on the time scale, can obtain every looks location spectrogram situation of change, and then can detect the cable joint state of weing, and it is more accurate to detect data, can characterize the joint rule of weing.
In another embodiment provided by the present invention, the loading a simulated working environment on the three-phase cable to be tested specifically includes:
sleeving a hose on the outer side of the three-phase cable to be tested, and adding water with a preset height;
and applying load circulation to two ends of the three-phase cable to be tested.
When this embodiment is implemented specifically, after having constructed the three-phase cable that awaits measuring, the whole bending of three-phase cable that awaits measuring is the U type, sheathes the hose in the outside of three-phase cable, adds the water of predetermineeing the height in the hose and, the accessible control overcoat hose in the water layer height realize bearing the simulation of different water pressure environment to the joint. And then designing a long-term damp aging loop according to the specification and length of the sample cable and the actual equipment condition of a laboratory, wherein the long-term damp aging loop mainly comprises the selection and verification of the types of the boosting and current rising equipment. Applying a cyclic load to the system to simulate a real running condition;
the actual working environment of the real three-phase cable is simulated, and the damp state of the real working environment of the three-phase cable can be detected.
In another embodiment provided by the present invention, the comparing the initial state positioning spectrogram with the latest obtained intermediate state positioning spectrogram data of each phase, analyzing the moisture state of the three-phase cable to be tested, and obtaining the most severe moisture-affected joint specifically includes:
acquiring initial state reflection peak data of each phase cable of the three-phase cable to be tested before loading through the initial state positioning spectrogram, wherein the initial state reflection peak data comprises initial state reflection peak values of each joint of each phase cable;
acquiring middle state reflection peak data of each loaded phase cable of the three-phase cable to be detected through a newly acquired middle state positioning spectrogram of each phase, wherein the middle state reflection peak data comprises initial state reflection peaks of each joint of each loaded phase cable;
when the difference between the intermediate state reflection peak value of any joint of the first-phase cable and the initial state reflection peak value of the joint is not smaller than a preset first threshold value, judging that the first-phase cable is in a damp state;
and judging that one connector of one phase cable with the maximum normalized interpolation of the intermediate state reflection peak value and the initial state reflection peak value in the three-phase cable to be tested is the connector with the most severe damp.
In specific implementation of this embodiment, the initial state reflection peak data of each phase cable of the three-phase cable to be tested before loading is acquired through the initial state positioning spectrogram, where the initial state reflection peak data includes an initial state reflection peak of each joint of each phase cable, and the initial state reflection peak data of each joint corresponds to the joint position one to one;
acquiring middle state reflection peak data of each loaded phase cable of the three-phase cable to be detected through a newly acquired middle state positioning spectrogram of each phase, wherein the middle state reflection peak data comprises initial state reflection peaks of each joint of each loaded phase cable;
the method comprises the steps of drawing an image of middle state reflection peak data of each joint of each phase cable of a three-phase cable to be detected according to a time scale, judging that the joint is in a damp state when the interpolation value of the middle state reflection peak data of one joint of one phase cable and the initial state reflection peak value of the joint is larger than a preset first threshold value, and selecting 5% of the middle state reflection peak data according to the setting of cable characteristics to prevent misjudgment during specific implementation.
When it is determined that one connector of one phase cable is affected with tide, the second connector of the second phase cable with the largest normalized interpolation is determined to be the connector with the most severe affected with tide by calculating the normalized difference value of the intermediate state reflection peak value and the initial state reflection peak value of each connector of each phase cable.
And obtaining an initial state reflection peak value of each joint of each phase cable through the initial state positioning spectrogram, obtaining a middle state reflection peak value of each joint of each phase cable through the newly obtained middle state positioning spectrogram, analyzing the moisture state of the three-phase cable to be tested through the initial state reflection peak value and the middle state reflection peak value, and obtaining the most severe moisture joint.
In another embodiment of the present invention, the specific wetting state of the joint with the most severe wetting in the above embodiments includes: the damping starting time, the damping saturation time and the damping rate;
the analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint in the preset time specifically comprises the following steps:
acquiring a positioning spectrogram of the joint with the most severe damp within preset time, acquiring a middle state reflection peak of the joint with the most severe damp within the preset time, and drawing the change condition of the middle state reflection peak on a time scale;
when the difference between the middle state reflection peak value of the joint with the most severe tide and the initial state reflection peak value of the joint with the most severe tide is not less than a preset first threshold value, recording the time at the moment as the tide starting time, and recording the starting peak value at the moment;
when the change value of the middle state reflection peak value of the joint with the most severe damp does not exceed the preset stable value range and keeps the preset stable time, recording the time as damp saturation time, and recording the saturation peak value at the time;
recording the difference between the initial peak value and the saturation peak value as a peak value difference, and recording the difference between the damping initial time and the damping saturation time as a time difference; the tidal rate is the absolute value of the ratio of the peak difference to the time.
In this embodiment, the specific moisture state includes: the damping starting time, the damping saturation time and the damping rate; the specific damp state analysis process comprises the following steps:
acquiring an intermediate state reflection peak value of the most severe joint of the most severe affected phase, and drawing the change condition of the intermediate state reflection peak value on a time scale;
when the difference between the intermediate state reflection peak value and the initial state reflection peak value of the joint with the most severe moisture is not less than a preset first threshold value, recording the time as the moisture initial time TsRecord the initial peak value P at this timex' wherein, the second threshold value can be set according to the cable characteristics, 5% of the reflection peak value data of the intermediate state is selected to prevent misjudgment;
when the change value of the intermediate state reflection peak value of the joint with the most severe damp does not exceed the preset stable value range and keeps the preset stable time, recording the time as the damp saturation time TdRecording the saturation peak P at that timex", where the stable value range can be set to 5% of the initial emission peak and the preset stable time can be set to 12 weeks;
in this embodiment, the second threshold, the stable value range, and the stable time may be specifically determined according to the characteristics of the three-phase cable, the load, and the like;
recording the difference between the initial peak value and the saturation peak value as a peak value difference, and recording the difference between the damping initial time and the damping saturation time as a time difference; the moisture rate is the absolute value of the ratio of the peak difference to the time, i.e. the moisture rate v | (P)x’-Px”)/(Ts-Td)|。
And drawing a curve of the positioning peak value at the joint along with the change of time by acquiring the positioning map of the joint with the most severe damping, and analyzing the damping specific characteristics of the joint under the normal operation condition of the cable, including damping starting time, damping saturation time and damping rate.
Acquiring initial state positioning spectrograms of all phases of a three-phase cable to be tested through building, loading a simulated working environment on the three-phase cable, repeatedly measuring the three-phase cable to be tested within a preset time interval to obtain intermediate state positioning spectrogram data of all phases, analyzing the moisture state of the three-phase cable to be tested according to the initial state positioning spectrograms and the obtained intermediate state positioning spectrogram data of all phases, and obtaining a connector with the most severe moisture; and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time. This embodiment passes through many times of measurement on the time scale, can obtain every looks location spectrogram situation of change, and then can detect the cable joint state of weing, and it is more accurate to detect data, can characterize the joint rule of weing.
In another embodiment provided by the present invention, referring to fig. 2, a structure diagram of a three-phase cable to be tested in a method for analyzing a moisture state of a three-phase cable intermediate joint according to another embodiment of the present invention is shown.
This embodiment adopts 3 cables to constitute the three-phase cable that awaits measuring, the cable model: YJV 8.7/153X 240, cable length 10m, 5m with a middle joint.
A U-shaped PVC hose is sleeved outside the water tank, water is added into the hose until the height of tap water reaches 1.5m, and the structural schematic diagram is shown in figure 2;
applying loads at two ends of the cable, wherein the specific parameters are as follows: the capacitance of each phase of the YJV 8.7/153 multiplied by 240 type cable is 0.34nF/m, and the total capacitance of a loop is 30.6 nF. The total loop power is 727.63Var, and after margin is considered, the minimum value of the transformer capacity is 1.46 kVA; the secondary side current I2 is 83.64mA, the transformation ratio n is 1:88, and the primary side current I1 is k n I2 is 7.36A.
Therefore, the transformer with the capacity of 70kVA, the rated voltage of 35kV (secondary) and the rated current of 2A (secondary) in a laboratory is adopted to meet the requirements of experiments and safety. After the samples are connected end to form a loop, a single set of current applying unit can apply 400A of current to the cable loop in practical tests, and the current carrying capacity of the cable is 495A.
And performing initial FDR measurement on each sample before the actual load is applied, and recording and storing initial peak data of the initial state positioning spectrogram.
And applying cyclic load according to the requirements, and periodically measuring once per week to obtain actual peak data of the corresponding intermediate state positioning spectrogram.
Selecting test data when the cable is affected with damp for 2 weeks, comparing the sizes of the peak values at the three-phase joints in the positioning spectrogram, calculating the descending value of the peak value of the three-phase joint, performing normalization calculation, wherein the phase with the descending amplitude exceeding 5% is the damped cable, and judging the phase with the largest descending amplitude as the most severe damped phase, wherein the joint is the most severe damped joint.
Recording the initial time T of the most severely affected jointsRecord the initial peak value P at this timex’；
Recording the saturation time T of the joint with the most severe moisturedRecording the saturation peak P at that timex”；
Calculating the moisture rate v | (P)x’-Px”)/(Ts-Td)|。
The embodiment of the invention provides a three-phase cable intermediate joint damp state analysis method, which comprises the steps of obtaining an initial state positioning spectrogram of each phase of a to-be-detected three-phase cable, loading a simulated working environment on the three-phase cable, repeatedly measuring the to-be-detected three-phase cable within a preset time interval to obtain an intermediate state positioning spectrogram of each phase, analyzing the damp state of the to-be-detected three-phase cable according to the initial state positioning spectrogram and the obtained intermediate state positioning spectrogram of each phase, and obtaining a most-damp joint; and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time. This embodiment passes through many times of measurement on the time scale, can obtain every looks location spectrogram situation of change, and then can detect cable joint state of weing, detects the initial time that wets, the saturation time that wets and the rate of weing that connects, and it is more accurate to detect data, can characterize the joint rule of weing, can be used for getting rid of potential weing to according to the difference of weing of three-phase cable, carry out the pertinence and handle.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (4)
1. A three-phase cable intermediate joint moisture state analysis method is characterized by comprising the following steps:
measuring an initial state positioning spectrogram of each phase cable of the initial state of the three-phase cable to be measured through frequency domain reflection measurement equipment;
loading a simulation working environment on the three-phase cable to be tested;
repeatedly measuring the loaded three-phase cable to be measured after a preset time interval, and obtaining an intermediate state positioning spectrogram of each phase cable;
analyzing the moisture state of the three-phase cable to be tested according to the initial state positioning spectrogram and the obtained intermediate state positioning spectrograms of the phases, and obtaining the most severe connector which is affected with moisture;
and analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint within preset time.
2. The method for analyzing the damp state of the intermediate joint of the three-phase cable according to claim 1, wherein the step of loading a simulated working environment on the three-phase cable to be tested specifically comprises the steps of:
sleeving a hose on the outer side of the three-phase cable to be tested, and adding water with a preset height;
and applying load circulation to two ends of the three-phase cable to be tested.
3. The method for analyzing the damped state of the intermediate joint of the three-phase cable according to claim 1, wherein the step of analyzing the damped state of the three-phase cable to be tested by comparing the initial state positioning spectrogram with the latest obtained intermediate state positioning spectrogram and obtaining the joint with the most severe damping specifically comprises the steps of:
acquiring initial state reflection peak data of each phase cable of the three-phase cable to be tested before loading through the initial state positioning spectrogram, wherein the initial state reflection peak data comprises initial state reflection peak values of each joint of each phase cable;
acquiring middle state reflection peak data of each loaded phase cable of the three-phase cable to be detected through a newly acquired middle state positioning spectrogram of each phase, wherein the middle state reflection peak data comprises initial state reflection peaks of each joint of each loaded phase cable;
when the difference between the intermediate state reflection peak value of any joint of the first-phase cable and the initial state reflection peak value of the joint is not smaller than a preset first threshold value, judging that the first-phase cable is in a damp state;
and judging that one connector of one phase cable with the maximum normalized difference value of the intermediate state reflection peak value and the initial state reflection peak value in the three-phase cable to be tested is the most severely affected by damp.
4. The method for analyzing the moisture state of the middle joint of the three-phase cable as claimed in claim 1, wherein the specific moisture state of the joint with the most severe moisture includes: the damping starting time, the damping saturation time and the damping rate;
the analyzing the specific wetting state of the most wetting joint according to the positioning spectrogram of the most wetting joint in the preset time specifically comprises the following steps:
acquiring a positioning spectrogram of the joint with the most severe damp within preset time, acquiring a middle state reflection peak of the joint with the most severe damp within the preset time, and drawing the change condition of the middle state reflection peak on a time scale;
when the difference between the middle state reflection peak value of the joint with the most severe tide and the initial state reflection peak value of the joint with the most severe tide is not smaller than a preset second threshold value, recording the time at the moment as the tide starting time, and recording the starting peak value at the moment;
when the change value of the middle state reflection peak value of the joint with the most severe damp does not exceed the preset stable value range and keeps the preset stable time, recording the time as damp saturation time, and recording the saturation peak value at the time;
recording the difference between the initial peak value and the saturation peak value as a peak value difference, and recording the difference between the damping initial time and the damping saturation time as a time difference; the tidal rate is the absolute value of the ratio of the peak difference to the time.
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| CN114019319A (en) * | 2021-10-20 | 2022-02-08 | 四川大学 | Distribution cable line-based moisture defect positioning and diagnosis method |
| CN114062866A (en) * | 2021-11-12 | 2022-02-18 | 广东电网有限责任公司广州供电局 | Method and device for evaluating cable insulation performance |
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| CN114019319A (en) * | 2021-10-20 | 2022-02-08 | 四川大学 | Distribution cable line-based moisture defect positioning and diagnosis method |
| CN114062866A (en) * | 2021-11-12 | 2022-02-18 | 广东电网有限责任公司广州供电局 | Method and device for evaluating cable insulation performance |
| CN114062866B (en) * | 2021-11-12 | 2023-10-20 | 广东电网有限责任公司广州供电局 | Method and device for evaluating insulation performance of cable |
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| CN113466607B (en) | 2023-06-06 |
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