CN110261679B - Power cable water inflow detection method, system, storage medium and device - Google Patents
Power cable water inflow detection method, system, storage medium and device Download PDFInfo
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- CN110261679B CN110261679B CN201910444376.4A CN201910444376A CN110261679B CN 110261679 B CN110261679 B CN 110261679B CN 201910444376 A CN201910444376 A CN 201910444376A CN 110261679 B CN110261679 B CN 110261679B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/04—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
- G01R27/06—Measuring reflection coefficients; Measuring standing-wave ratio
Abstract
The invention relates to a method, a system, a storage medium and a device for detecting water inflow of a power cable, wherein the method comprises the steps of detecting the insulation resistance of an outer sheath layer of the power cable to be detected, and judging that the insulation of the outer sheath layer of the power cable to be detected is abnormal when the insulation resistance is smaller than a preset insulation resistance threshold value; the method comprises the steps that an alternating current excitation signal is adopted to act on a power cable core to be detected, and whether the power cable core to be detected generates an echo reflection signal or not is detected; when the power cable core to be detected generates an echo reflection signal, the standing-wave ratio is calculated according to the echo reflection signal, and when the standing-wave ratio is larger than a first preset standing-wave ratio threshold value, the water inflow of the power cable to be detected is determined. According to the invention, through detecting the insulation resistance of the outer sheath layer of the power cable, whether water inflow is possible can be preliminarily judged, the excitation information is loaded on the power cable, whether the water inflow of the power cable is judged according to whether the echo signal is generated or not and the standing-wave ratio of the echo signal, the detection result is accurate, the road surface does not need to be excavated, the detection efficiency is greatly improved, and the maintenance cost is greatly reduced.
Description
Technical Field
The invention relates to the technical field of power cable detection, in particular to a method, a system, a storage medium and a device for detecting water inflow of a power cable.
Background
Currently, in the power industry, most power cables are buried underground through pipelines. Because the drawback of ponding exists underground, lead to power cable often to soak in the water, especially in rainy season, or when underground pipe blockage, power cable usually soaks in the water for a long time, this has brought very big hidden danger for power cable's normal work, in case power cable intakes, under the effect of electric field, can sound production water tree ageing phenomenon, lead to power cable to puncture at last, still can bring negative effects for power cable's electrical transmission characteristic, characteristics such as electric capacity, decay, crosstalk and balance. In the long term, the water entering the power cable causes corrosion of the shielding layer, armor layer and the like of the power cable and various insulation problems. In the prior art, a lower field excavation mode is usually adopted for detection, so that on one hand, the efficiency is low, the construction amount is large, on the other hand, the higher maintenance cost is generated, and the method becomes a serious difficulty in work for an electric power department.
Disclosure of Invention
The present invention provides a method, a system, a storage medium and a device for detecting water inflow of a power cable, which are used for solving the technical problems of the prior art.
The technical scheme for solving the technical problems is as follows: a power cable water inlet detection method comprises the following steps:
step 1: detecting the insulation resistance of the outer sheath layer of the power cable to be detected, judging that the insulation of the outer sheath layer of the power cable to be detected is abnormal when the insulation resistance is smaller than a preset insulation resistance threshold value, and entering the step 2;
step 2: the method comprises the steps that an alternating current excitation signal is adopted to act on a power cable core to be detected, and whether the power cable core to be detected generates an echo reflection signal or not is detected;
and step 3: when the power cable core to be detected generates an echo reflection signal, a standing wave ratio is calculated according to the echo reflection signal, and when the standing wave ratio is larger than a first preset standing wave ratio threshold value, water inflow of the power cable to be detected is determined.
The invention has the beneficial effects that: according to the method for detecting the water inflow of the power cable, disclosed by the invention, through detecting the insulation resistance of the outer sheath layer of the power cable, whether the possibility of water inflow exists can be preliminarily judged, the excitation information is further loaded on the power cable, whether the power cable is subjected to water inflow or not is judged according to whether the echo signal is generated or not and the standing-wave ratio of the echo signal, the detection result is accurate, the road surface does not need to be excavated, the detection efficiency is greatly improved, and the maintenance cost is greatly reduced.
On the basis of the technical scheme, the invention can be further improved as follows:
further: in the step 1, the preset insulation resistance threshold value is K × standard insulation resistance threshold value;
wherein, the threshold value of the insulation resistance of the standard sample is the insulation resistance of the outer sheath layer when the standard sample power cable is not watered, and the value range of K is [0.4-0.8 ].
The beneficial effects of the further scheme are as follows: through setting up and presetting the insulation resistance threshold value, be convenient for as the reference of the insulation resistance of the power cable that awaits measuring to confirm whether the insulation resistance of the power cable that awaits measuring exists unusually, be convenient for confirm whether the power cable that awaits measuring exists into water probably.
Further: in the process of detecting the insulation resistance of the outer sheath layer of the power cable to be detected, the temperature change of the detection environment is kept to be less than 1 ℃.
The beneficial effects of the further scheme are as follows: by controlling the stability of the detection environment, the influence of the temperature on the insulation resistance detection result can be reduced as much as possible, the accuracy of the detection result is ensured, and the reliability of the final judgment result is greatly improved.
Further: in the step 3, when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to the second preset standing-wave ratio threshold, detecting the humidity of the environment where the cable to be tested is located, inquiring whether the standing-wave ratio is matched with the environment temperature in a preset inquiry table, and determining that the power cable to be tested enters water when the standing-wave ratio is not matched with the environment temperature;
and pre-establishing a one-to-one mapping relation between the humidity range of the environment when no water is fed and the corresponding standing wave ratio in the lookup table, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
The beneficial effects of the further scheme are as follows: when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold value and larger than or equal to the second preset standing-wave ratio threshold value, whether the power cable to be detected enters water or not can not be directly judged through the standing-wave ratio, at the moment, the humidity of the environment where the cable is located is further detected, and whether the standing-wave ratio is matched with the environment humidity or not is determined according to a preset query table, so that whether water enters to be detected or not can be further determined, and the detection accuracy is improved.
The invention also provides a power cable water inlet detection system, which comprises:
the detection module is used for detecting the insulation resistance of the outer sheath layer of the power cable to be detected; the device is also used for adopting an alternating current excitation signal to act on a power cable core to be detected when the insulation resistance is smaller than a preset insulation resistance threshold value, and detecting whether the power cable core to be detected generates an echo reflection signal or not;
and the processing module is used for calculating the standing-wave ratio according to the echo reflection signal when the to-be-detected power cable core generates the echo reflection signal, and determining that the to-be-detected power cable enters water when the standing-wave ratio is greater than a first preset standing-wave ratio threshold value.
The invention has the beneficial effects that: according to the water inlet detection system for the power cable, disclosed by the invention, whether water is likely to enter can be preliminarily judged by detecting the insulation resistance of the outer sheath layer of the power cable, the excitation information is further loaded on the power cable, whether the water enters the power cable is judged according to whether the echo signal is generated and the standing-wave ratio of the echo signal, the detection result is accurate, the road surface does not need to be excavated, the detection efficiency is greatly improved, and the maintenance cost is greatly reduced.
On the basis of the technical scheme, the invention can be further improved as follows:
further: the preset insulation resistance threshold value is K times of the standard insulation resistance threshold value;
wherein, the threshold value of the insulation resistance of the standard sample is the insulation resistance of the outer sheath layer when the standard sample power cable is not watered, and the value range of K is [0.4-0.8 ].
The beneficial effects of the further scheme are as follows: through setting up and presetting the insulation resistance threshold value, be convenient for as the reference of the insulation resistance of the power cable that awaits measuring to confirm whether the insulation resistance of the power cable that awaits measuring exists unusually, be convenient for confirm whether the power cable that awaits measuring exists into water probably.
Further: and in the process of detecting the insulation resistance of the outer sheath layer of the power cable to be detected by the detection module, keeping the temperature change to be less than 1 ℃.
The beneficial effects of the further scheme are as follows: by controlling the stability of the detection environment, the influence of the temperature on the insulation resistance detection result can be reduced as much as possible, the accuracy of the detection result is ensured, and the reliability of the final judgment result is greatly improved.
Further: when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to a second preset standing-wave ratio threshold, the detection module is further used for detecting the humidity of the environment where the cable to be detected is located;
the processing module is also used for inquiring whether the standing-wave ratio is matched with the corresponding environment humidity range in a preset inquiry table and determining that the power cable to be detected enters water when the standing-wave ratio is not matched with the corresponding environment humidity range;
and establishing a one-to-one mapping relation between the humidity of the environment and the corresponding standing wave ratio when no water enters the lookup table in advance, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
The beneficial effects of the further scheme are as follows: in the step 3, when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to the second preset standing-wave ratio threshold, detecting the humidity of the environment where the cable to be tested is located, inquiring whether the standing-wave ratio is matched with the environment humidity in a preset inquiry table, and determining that the power cable to be tested enters water when the standing-wave ratio is not matched with the environment humidity;
and pre-establishing a one-to-one mapping relation between the humidity range of the environment when no water is fed and the corresponding standing wave ratio in the lookup table, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
The invention also provides a computer readable storage medium, on which a computer program is stored, wherein the computer program, when executed by a processor, implements the power cable water inflow detection method.
The invention also provides a power cable water inflow detection device, which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor realizes the steps of the power cable water inflow detection method when executing the computer program.
Drawings
FIG. 1 is a schematic flow chart of a method for detecting water inflow of a power cable according to the present invention;
fig. 2 is a block diagram of a power cable water inlet detection system according to the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, a method for detecting water inflow of a power cable includes the following steps:
step 1: detecting the insulation resistance of the outer sheath layer of the power cable to be detected, judging that the insulation of the outer sheath layer of the power cable to be detected is abnormal when the insulation resistance is smaller than a preset insulation resistance threshold value, and entering the step 2;
step 2: the method comprises the steps that an alternating current excitation signal is adopted to act on a power cable core to be detected, and whether the power cable core to be detected generates an echo reflection signal or not is detected;
and step 3: when the power cable core to be detected generates an echo reflection signal, a standing wave ratio is calculated according to the echo reflection signal, and when the standing wave ratio is larger than a first preset standing wave ratio threshold value, water inflow of the power cable to be detected is determined.
In fact, the characteristic impedance of the power cable under test defines the voltage versus current at any point on the power cable under test. The high or low characteristic impedance is not a good factor in its own right. However, when the power cable to be tested is connected with other components in a matching manner, the characteristic impedance becomes an important factor. If the characteristic impedance of the power cable pair does not match the characteristic impedance of its connecting components, echo reflections of the signal may occur. The characteristic impedance can be reduced to steam in the power cable to cause the mismatch between power cable and the connecting piece to be measured, lead to echo reflection signal's production, promptly after power cable intakes, its characteristic impedance can change, mismatch between characteristic impedance and rather than the part of being connected, the concrete embodiment is in forming echo reflection signal. Therefore, in the present invention, whether the power cable to be tested generates water is determined by detecting whether the power cable core to be tested generates an echo reflection signal (referred to as a voltage echo reflection signal in the present invention), and by detecting the standing wave ratio of the echo reflection signal when the echo reflection signal is generated.
According to the method for detecting the water inflow of the power cable, disclosed by the invention, through detecting the insulation resistance of the outer sheath layer of the power cable, whether the possibility of water inflow exists can be preliminarily judged, the excitation information is further loaded on the power cable, whether the power cable is subjected to water inflow or not is judged according to whether the echo signal is generated or not and the standing-wave ratio of the echo signal, the detection result is accurate, the road surface does not need to be excavated, the detection efficiency is greatly improved, and the maintenance cost is greatly reduced.
When the power cable that awaits measuring was intake, the insulation resistance of its outer sheath layer can reduce, however, when detecting the insulation resistance reduction of outer sheath layer, can not directly confirm that it arrives by its intaking because when power cable ageing, its insulation resistance also can reduce. In other cases, such as an abnormal situation of a power cable breakage, a loose joint, or a cable breakage, the insulation resistance thereof increases. Therefore, the insulation resistance indicates the presence of aging or the possibility of water ingress of the power cable to be tested when the insulation resistance of the power cable to be tested decreases.
In one or more embodiments of the present invention, in step 1, the preset insulation resistance threshold is K × a standard insulation resistance threshold;
wherein the threshold value of the insulation resistance of the standard sample is the insulation resistance of the outer sheath layer when the water does not enter the standard sample power cable, and the value range of K is [0.4-0.8 ].
Through setting up and presetting the insulation resistance threshold value, be convenient for as the reference of the insulation resistance of the power cable that awaits measuring to confirm whether the insulation resistance of the power cable that awaits measuring exists unusually, be convenient for confirm whether the power cable that awaits measuring exists into water probably.
The method comprises the steps of firstly, determining that the insulation resistance of the power cable to be detected is smaller than the insulation resistance of the standard sample power cable outer sheath layer when water does not enter, and determining whether water enters the surface of the power cable to be detected, so that whether water enters the surface of the power cable to be detected is determined according to the standing wave ratio of echo reflection signals, and the echo reflection signals of the core of the power cable to be detected are not directly detected.
It should be noted that, in the present invention, after the power cable enters water, the insulation resistance of the outer sheath layer of the power cable is significantly reduced, and usually is significantly less than 0.5M Ω, so in step 1, when it is detected that the insulation resistance of the outer sheath layer of the power cable to be detected is not less than the preset insulation resistance threshold, it indicates that the power cable does not have the possibility of entering water.
In one or more embodiments provided by the present invention, in the process of detecting the insulation resistance of the outer sheath layer of the power cable to be detected, the temperature change of the detection environment is kept less than 1 ℃.
By controlling the stability of the detection environment, the influence of the temperature on the insulation resistance detection result can be reduced as much as possible, the accuracy of the detection result is ensured, and the reliability of the final judgment result is greatly improved.
In order to ensure the accuracy of the detection result, the invention adopts a variable control method, firstly detects the temperature of the environment where the power cable to be detected is located, starts detection when the temperature of the environment where the power cable to be detected is kept stable (namely the temperature change is less than 1 ℃), synchronously and quickly finishes the detection of the insulation resistance of the standard sample power cable and the power cable to be detected in the environment where the cable to be detected is located, and removes the average value after multiple measurements, thus ensuring the accuracy of the detection result and avoiding the influence of environmental factors on the detection result.
In one or more embodiments provided by the present invention, in step 3, when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to a second preset standing-wave ratio threshold, detecting the humidity of the environment where the cable to be measured is located, querying in a preset lookup table whether the standing-wave ratio is matched with the environment humidity, and determining that the power cable to be measured is flooded when the standing-wave ratio is not matched with the environment humidity;
and pre-establishing a one-to-one mapping relation between the humidity range of the environment when no water is fed and the corresponding standing wave ratio in the lookup table, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
When the standing-wave ratio is smaller than the first preset standing-wave ratio threshold value and larger than or equal to the second preset standing-wave ratio threshold value, whether the power cable to be detected enters water or not can not be directly judged through the standing-wave ratio, at the moment, the humidity of the environment where the cable is located is further detected, and whether the standing-wave ratio is matched with the environment humidity or not is determined according to a preset query table, so that whether water enters to be detected or not can be further determined, and the detection accuracy is improved.
Here, when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold, it cannot be determined whether the power cable to be tested is flooded according to the aforementioned method, because the criterion at this time is that the insulation resistance of the power cable to be tested is decreased, after the alternating current excitation signal is loaded on the wire core of the power cable to be tested, an echo reflection signal is generated, but the standing wave ratio of the echo reflection signal is smaller than a first preset standing wave ratio threshold value, at the moment, because the echo reflection signal is generated, the characteristic impedance of the power cable line pair to be tested is not matched with the characteristic impedance of the connecting part, and the standing wave ratio of the echo reflection signal is small, water is possibly filled in, the environment is possibly wet, the water molecules in the air enter the power cable to be tested, for example, the water molecules in the air easily enter the power cable when the power cable is damaged. Even if a small amount of water is distributed on the wire core of the power cable to be tested, the wire core of the power cable to be tested can generate echo reflection signals under the action of the excitation signals, and only standing wave ratios of the echo reflection signals are different at the moment.
Therefore, in order to further determine whether the standing-wave ratio of the echo reflection signal is smaller than the first preset standing-wave ratio threshold value due to the fact that the power cable to be detected is flooded or a small amount of water vapor enters due to the fact that the humidity in the air is relatively high.
In the embodiment of the present invention, a value of the first preset standing wave ratio threshold is greater than 2.5, and a value of the second preset standing wave ratio threshold is between 1.5 and 2.5, so as to more clearly reflect an influence of humidity in an environment on a standing wave ratio of an echo reflected signal, the present invention provides a lookup table for reference, as shown in table 1 below.
TABLE 1
As can be seen from table 1, as the humidity in the environment increases, the standing-wave ratio of the echo reflected signal also increases, and when the humidity in the environment exceeds 50%, the amplitude of the increase of the standing-wave ratio of the corresponding echo reflected signal is larger, which indicates that the loss of the power cable is obviously increased after the humidity in the environment exceeds a certain degree, and the standing-wave ratio also increases. Therefore, when it is detected that the standing-wave ratio of the echo reflection signal does not match the corresponding humidity in table 1, it indicates that the humidity in the environment does not increase the standing-wave ratio of the echo reflection signal of the power cable to a large value (for example, over 2.5), and the standing-wave ratio of the echo reflection signal of the power cable increases with the increase of the humidity in the environment, it may be preliminarily determined that the power cable is in the water-inlet state at this time.
As shown in fig. 2, the present invention also provides a water inlet detection system for a power cable, comprising:
the detection module is used for detecting the insulation resistance of the outer sheath layer of the power cable to be detected; the device is also used for adopting an alternating current excitation signal to act on a power cable core to be detected when the insulation resistance is smaller than a preset insulation resistance threshold value, and detecting whether the power cable core to be detected generates an echo reflection signal or not;
and the processing module is used for calculating the standing-wave ratio according to the echo reflection signal when the to-be-detected power cable core generates the echo reflection signal, and determining that the to-be-detected power cable enters water when the standing-wave ratio is greater than a first preset standing-wave ratio threshold value.
The invention has the beneficial effects that: according to the water inlet detection system for the power cable, disclosed by the invention, whether water is likely to enter can be preliminarily judged by detecting the insulation resistance of the outer sheath layer of the power cable, the excitation information is further loaded on the power cable, whether the water enters the power cable is judged according to whether the echo signal is generated and the standing-wave ratio of the echo signal, the detection result is accurate, the road surface does not need to be excavated, the detection efficiency is greatly improved, and the maintenance cost is greatly reduced.
In one or more embodiments provided herein, the preset insulation resistance threshold is K × a standard insulation resistance threshold;
wherein, the threshold value of the insulation resistance of the standard sample is the insulation resistance of the outer sheath layer when the standard sample power cable is not watered, and the value range of K is [0.4-0.8 ].
Through setting up and presetting the insulation resistance threshold value, be convenient for as the reference of the insulation resistance of the power cable that awaits measuring to confirm whether the insulation resistance of the power cable that awaits measuring exists unusually, be convenient for confirm whether the power cable that awaits measuring exists into water probably.
In one or more embodiments provided by the present invention, in the process of detecting the insulation resistance of the outer sheath layer of the power cable to be detected by the detection module, the temperature variation is kept less than 1 ℃.
By controlling the stability of the detection environment, the influence of the temperature on the insulation resistance detection result can be reduced as much as possible, the accuracy of the detection result is ensured, and the reliability of the final judgment result is greatly improved.
In one or more embodiments provided by the present invention, when the standing-wave ratio is less than the first preset standing-wave ratio threshold and greater than or equal to a second preset standing-wave ratio threshold, the detecting module is further configured to detect the humidity of the environment where the cable to be detected is located;
the processing module is also used for inquiring whether the standing-wave ratio is matched with the corresponding environment humidity range in a preset inquiry table and determining that the power cable to be detected enters water when the standing-wave ratio is not matched with the corresponding environment humidity range;
and establishing a one-to-one mapping relation between the humidity of the environment and the corresponding standing wave ratio when no water enters the lookup table in advance, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
In the step 3, when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to the second preset standing-wave ratio threshold, detecting the humidity of the environment where the cable to be tested is located, inquiring whether the standing-wave ratio is matched with the environment humidity in a preset inquiry table, and determining that the power cable to be tested enters water when the standing-wave ratio is not matched with the environment humidity;
and pre-establishing a one-to-one mapping relation between the humidity range of the environment when no water is fed and the corresponding standing wave ratio in the lookup table, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
The invention also provides a computer readable storage medium, on which a computer program is stored, wherein the computer program, when executed by a processor, implements the power cable water inflow detection method.
It should be noted that, here, it is necessary to use the insulation resistance detection device in the prior art to detect the insulation resistance of the outer sheath layer of the power cable to be detected, and use the existing ac excitation source to act on the power cable core to be detected, and use the existing signal detection device to detect whether the power cable core to be detected generates the echo reflection signal and the size of the echo reflection signal, and the other software execution steps such as calculation, processing, comparison, and judgment are completed when the processor executes the computer program on the storage medium.
The invention also provides a power cable water inflow detection device, which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor realizes the steps of the power cable water inflow detection method when executing the computer program.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A power cable water inlet detection method is characterized by comprising the following steps:
step 1: detecting the insulation resistance of the outer sheath layer of the power cable to be detected, judging that the insulation of the outer sheath layer of the power cable to be detected is abnormal when the insulation resistance is smaller than a preset insulation resistance threshold value, and entering the step 2;
step 2: the method comprises the steps that an alternating current excitation signal is adopted to act on a power cable core to be detected, and whether the power cable core to be detected generates an echo reflection signal or not is detected;
and step 3: when the power cable core to be detected generates an echo reflection signal, calculating a standing-wave ratio according to the echo reflection signal, and when the standing-wave ratio is larger than a first preset standing-wave ratio threshold value, determining that the power cable to be detected is water-feeding;
in the step 3, when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to the second preset standing-wave ratio threshold, detecting the humidity of the environment where the cable to be tested is located, inquiring whether the standing-wave ratio is matched with the corresponding environment humidity range in a preset inquiry table, and determining that the power cable to be tested enters water when the standing-wave ratio is not matched with the corresponding environment humidity range;
and establishing a one-to-one mapping relation between the humidity of the environment and the corresponding standing wave ratio when no water enters the lookup table in advance, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
2. A method for detecting water ingress into an electric power cable according to claim 1, wherein in step 1, the preset insulation resistance threshold = K × standard insulation resistance threshold;
wherein, the threshold value of the insulation resistance of the standard sample is the insulation resistance of the outer sheath layer when the standard sample power cable is not watered, and the value range of K is [0.4-0.8 ].
3. The power cable water inflow detection method according to claim 2, wherein in the process of detecting the insulation resistance of the outer sheath layer of the power cable to be detected, the temperature change of the detection environment is kept less than 1 ℃.
4. A power cable water ingress detection system, comprising:
the detection module is used for detecting the insulation resistance of the outer sheath layer of the power cable to be detected; the device is also used for adopting an alternating current excitation signal to act on a power cable core to be detected when the insulation resistance is smaller than a preset insulation resistance threshold value, and detecting whether the power cable core to be detected generates an echo reflection signal or not;
the processing module is used for calculating a standing-wave ratio according to an echo reflection signal when the to-be-detected power cable core generates the echo reflection signal, and determining that the to-be-detected power cable enters water when the standing-wave ratio is larger than a first preset standing-wave ratio threshold value;
when the standing-wave ratio is smaller than the first preset standing-wave ratio threshold and is greater than or equal to a second preset standing-wave ratio threshold, the detection module is further used for detecting the humidity of the environment where the cable to be detected is located;
the processing module is also used for inquiring whether the standing-wave ratio is matched with the environmental humidity range in a preset inquiry table and determining that the power cable to be tested enters water when the standing-wave ratio is not matched with the environmental humidity range;
and pre-establishing a one-to-one mapping relation between the humidity range of the environment when no water is fed and the corresponding standing wave ratio in the lookup table, wherein the second preset standing wave ratio is smaller than the first preset standing wave ratio.
5. A power cable water ingress detection system according to claim 4, wherein the preset insulation resistance threshold = K + standard insulation resistance threshold;
wherein, the threshold value of the insulation resistance of the standard sample is the insulation resistance of the outer sheath layer when the standard sample power cable is not watered, and the value range of K is [0.4-0.8 ].
6. The power cable water inflow detection system according to claim 5, wherein the temperature change of the detection environment is kept less than 1 ℃ in the process of detecting the insulation resistance of the outer sheath layer of the power cable to be detected by the detection module.
7. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out a power cable water ingress detection method according to any one of claims 1 to 3.
8. A power cable water ingress detection apparatus comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor when executing the computer program implementing the steps of the power cable water ingress detection method as claimed in any one of claims 1 to 3.
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