CN111965446A - Experimental method for evaluating different water inflow and damp states of power cable - Google Patents
Experimental method for evaluating different water inflow and damp states of power cable Download PDFInfo
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- CN111965446A CN111965446A CN202010668068.2A CN202010668068A CN111965446A CN 111965446 A CN111965446 A CN 111965446A CN 202010668068 A CN202010668068 A CN 202010668068A CN 111965446 A CN111965446 A CN 111965446A
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Abstract
The invention discloses an experimental method for evaluating different water-inlet and damp states of a power cable. The temperature rise characteristic of the material of the filling layer of the cable reflects the change of the thermal parameter of the filling layer of the cable, and the temperature rise characteristic can be used for detecting the water inlet condition of the cable. The experimental method provided by the invention is used for carrying out transient control experiment and steady state control experiment on the cable, so that the change characteristics of the temperature and thermal parameters of the cable in different operating environments can be effectively obtained, the water inflow characteristic quantity of the cable can be verified, an important basis is provided for the water inflow research of the cable, and theoretical guidance is provided for the water inflow prevention characteristic quantity of the cable.
Description
Technical Field
The invention relates to an experimental method, in particular to an experimental method for evaluating different water inflow and damp states of a power cable.
Background
The development and construction of cities are accompanied by the popularization of power cables, and according to statistics, most of power cable safety accidents are caused by water inflow of the cables. The cable is rapidly aged after water enters, and if the cable is not treated in time, insulation breakdown is finally developed, so that the cable has great influence on the electricity consumption of residents. Usually, the outer layer of the power cable structure has a buffer layer which absorbs water to swell when water invades, and the water is prevented from diffusing along the axial direction of the cable, but the mode cannot prevent the water inlet problem.
The biggest problem of the current water inflow prevention development is the uncertainty of water inflow characteristic quantity, and the traditional humidity measurement is difficult to accurately reflect the water inflow condition. Therefore, an experimental method for evaluating different water inflow and moisture states of the power cable is urgently needed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides an experimental method for evaluating different water inflow and moisture states of a power cable. The experimental method for evaluating the different water-inlet damp states of the power cable is simple and convenient to operate, and provides theoretical guidance for cable water-inlet prevention.
The purpose of the invention is realized by the following technical scheme: the experimental method for evaluating different water inflow and damp states of the power cable comprises the following steps:
s1, preparation of experimental materials:
s1-1, selecting a cable with a proper length;
s1-2, fixing the cable, and then drilling holes on the cable by using a drilling machine to complete the operation of the damaged point and the temperature detection point;
s1-3, laying a thermocouple at the temperature detection point, and sealing by using epoxy cement;
s2, performing transient control experiments:
s2-1, loading current I on the cable under the dry conditionMAXThe temperature T is recorded during the period from the start of the current application to the time when the operation is stable1Change and plot the temperature T1Then the power is cut off to enable the cable to recover the initial state;
s2-2, loading current I on the cable under the dry conditionMAXSimultaneously, the cable is soaked into water to simulate the actual water inlet condition, and the temperature T in the process from the loading of current to the stable operation is recorded2Change and plot this temperature T2Then the power is cut off to enable the cable to recover the initial state;
s3, performing steady state control experiments:
reference group: applying a current I to the cable under dry conditionsMAXRecording the temperature T after the cable enters a stable operation state3(ii) a Injecting water at the damaged point, wherein the water injection amount is W, and recording the temperature T after the cable enters a stable operation state4Calculating the temperature T3And temperature T4The difference between them, then power off to restore the cable to the initial state;
load control group: applying a current I to the cable under dry conditionsrandomWherein, 0 is less than or equal to Irandom≤IMAXRecording the temperature T after the temperature has stabilized5(ii) a Injecting water at the damaged point, wherein the water injection amount is W, and recording the temperature T after the cable enters a stable operation state6Calculating the temperature T5And temperature T6The difference between them, then power off to restore the cable to the initial state;
water inlet control group: applying a current I to the cable under dry conditionsMAXRecording the temperature T after the cable enters a stable operation state7(ii) a Injecting water at the damaged point with the water injection amount of WrandomWherein, 0 is less than or equal to IrandomLess than or equal to W, and recording the temperature T after the cable enters a stable operation state8Calculating the temperature T7And temperature T8The difference between them, and then power is cut off to restore the cable to its original state.
The following steps are also included between steps S1-3 and S2: s1-4, cleaning the experimental cable by using absolute ethyl alcohol.
In step S2 and step S3, the current IMAXThe size determination step is as follows: setting the core temperature of the cable at normal temperature as initial temperature and the core maximum temperature of the cable at 90 deg.c during full-load operation of the cable, and determining I with heat path calculation formulaMAXThe size of (2).
In step S3, the water injection amount W is equal to the single maximum water inflow of the cable known from the local cable water inflow fault statistics.
Compared with the prior art, the invention has the following advantages:
the experimental method for evaluating different water inflow and moisture states of the power cable carries out transient state comparison experiment and steady state comparison experiment on the cable, wherein the transient state comparison experiment depicts a temperature change curve of a process from a dry state to a fully wet state of a filling layer of the cable, the steady state comparison experiment focuses on the temperature difference between the dry state and the fully wet state of the filling layer of the cable, two changes of the whole process from water seepage to moisture permeation of the cable are fully considered, the water inflow and moisture state is evaluated in all aspects, the method has the characteristics of simplicity and convenience in measurement, strong applicability and the like, and theoretical guidance can be provided for water inflow prevention characteristic quantity of the cable.
Drawings
Fig. 1 is a front view of materials of the experimental method for evaluating the different water-entering damp states of a power cable according to the present invention.
Fig. 2 is a side view of the materials of the experimental method for evaluating the different water-entering damp states of the power cable according to the present invention.
Wherein, 1 is a cable, 2 is a breakage point, and 3 is a temperature detection point.
Detailed Description
The invention is further illustrated by the following figures and examples.
The experimental method for evaluating different water inflow and moisture states of the power cable as shown in fig. 1 and fig. 2 comprises the following steps:
s1, preparation of experimental materials:
s1-1, selecting a cable with a proper length;
s1-2, fixing the cable, and then drilling holes on the cable by using a drilling machine to complete the operation of the damaged point and the temperature detection point;
s1-3, laying a thermocouple at the temperature detection point, and sealing by using epoxy cement;
s1-4, cleaning the experimental cable by using absolute ethyl alcohol;
s2, performing transient control experiments:
s2-1, loading current I on the cable under the dry conditionMAXThe temperature T is recorded during the period from the start of the current application to the time when the operation is stable1Change and plot the temperature T1Then the power is cut off to enable the cable to recover the initial state;
s2-2, loading current I on the cable under the dry conditionMAXSimultaneously, the cable is soaked into water to simulate the actual water inlet condition, and the temperature T in the process from the loading of current to the stable operation is recorded2Change and plot this temperature T2Then the power is cut off to enable the cable to recover the initial state;
s3, performing steady state control experiments:
reference group: applying a current I to the cable under dry conditionsMAXRecording the temperature T after the cable enters a stable operation state3(ii) a Injecting water at the damaged point, wherein the water injection amount is W, and recording the temperature T after the cable enters a stable operation state4Calculating the temperature T3And temperature T4The difference between them, then power off to restore the cable to the initial state;
load control group: applying a current I to the cable under dry conditionsrandomWherein, 0 is less than or equal to Irandom≤IMAXRecording the temperature T after the temperature has stabilized5(ii) a Injecting water at the damaged point, wherein the water injection amount is W, and recording the temperature T after the cable enters a stable operation state6Calculating the temperature T5And temperature T6The difference between them, then power off to restore the cable to the initial state;
water inlet control group: applying a current I to the cable under dry conditionsMAXRecording the temperature T after the cable enters a stable operation state7(ii) a Injecting water at the damaged point with the water injection amount of WrandomWherein, 0 is less than or equal to IrandomLess than or equal to W, and recording the temperature T after the cable enters a stable operation state8Calculating the temperature T7And temperature T8The difference between them, and then power is cut off to restore the cable to its original state.
Wherein, the initial state is: current I to the cable at a core temperature of 90 deg.C, i.e. under full-load operation of the cableMAXAnd after the weight of the cable is maintained to be unchanged, the power is cut off, the residual charge of the cable is subjected to discharge treatment, and the wire core is cooled to room temperature, wherein the state at the moment is called as the initial state of the cable. The stable operation state means that the temperature measured by the thermocouple is kept unchanged within 30 minutes.
The temperature detection point comprises a buffer layer temperature detection point and a wire core temperature detection point, wherein the buffer layer temperature detection point is used for detecting the temperature T during transient control experiment and steady control experiment1～T8And the core temperature detection point is used for determining the running state of the cable. In the preparation of the test material in step S1, the temperature measuring end of the thermocouple laid at the buffer temperature detecting point extends to the buffer layer of the cable, and the temperature measuring end of the thermocouple laid at the core temperature detecting point extends to the core of the cable.
In step S2 and step S3, the current IMAXThe size determination step is as follows: the core temperature of the cable at normal temperature is set as the initial temperature, the core maximum temperature of the cable under the full-load operation of the cable is set as 90 ℃, and a hot circuit is adopted according to the specification and the size of the cableDetermination of I by computer formulaMAXThe size of (2).
In step S3, the water injection amount W is equal to the single maximum water inflow of the cable known from the local cable water inflow fault statistics.
The above-mentioned embodiments are preferred embodiments of the present invention, and the present invention is not limited thereto, and any other modifications or equivalent substitutions that do not depart from the technical spirit of the present invention are included in the scope of the present invention.
Claims (4)
1. An experimental method for evaluating different water inflow and moisture states of a power cable is characterized by comprising the following steps:
s1, preparation of experimental materials:
s1-1, selecting a cable with a proper length;
s1-2, fixing the cable, and then drilling holes on the cable by using a drilling machine to complete the operation of the damaged point and the temperature detection point;
s1-3, laying a thermocouple at the temperature detection point, and sealing by using epoxy cement;
s2, performing transient control experiments:
s2-1, loading current I on the cable under the dry conditionMAXThe temperature T is recorded during the period from the start of the current application to the time when the operation is stable1Change and plot the temperature T1Then the power is cut off to enable the cable to recover the initial state;
s2-2, loading current I on the cable under the dry conditionMAXSimultaneously, the cable is soaked into water to simulate the actual water inlet condition, and the temperature T in the process from the loading of current to the stable operation is recorded2Change and plot this temperature T2Then the power is cut off to enable the cable to recover the initial state;
s3, performing steady state control experiments:
reference group: applying a current I to the cable under dry conditionsMAXRecording the temperature T after the cable enters a stable operation state3(ii) a Injecting water at the damaged point, wherein the water injection amount is W, and the cable is fedRecording the temperature T after entering a stable operating state4Calculating the temperature T3And temperature T4The difference between them, then power off to restore the cable to the initial state;
load control group: applying a current I to the cable under dry conditionsrandomWherein, 0 is less than or equal to Irandom≤IMAXRecording the temperature T after the temperature has stabilized5(ii) a Injecting water at the damaged point, wherein the water injection amount is W, and recording the temperature T after the cable enters a stable operation state6Calculating the temperature T5And temperature T6The difference between them, then power off to restore the cable to the initial state;
water inlet control group: applying a current I to the cable under dry conditionsMAXRecording the temperature T after the cable enters a stable operation state7(ii) a Injecting water at the damaged point with the water injection amount of WrandomWherein, 0 is less than or equal to IrandomLess than or equal to W, and recording the temperature T after the cable enters a stable operation state8Calculating the temperature T7And temperature T8The difference between them, and then power is cut off to restore the cable to its original state.
2. The experimental method for evaluating the different water-entering and damp states of the power cable according to claim 1, wherein: the following steps are also included between steps S1-3 and S2: s1-4, cleaning the experimental cable by using absolute ethyl alcohol.
3. The experimental method for evaluating the different water-entering and damp states of the power cable according to claim 1, wherein: in step S2 and step S3, the current IMAXThe size determination step is as follows: setting the core temperature of the cable at normal temperature as initial temperature and the core maximum temperature of the cable at 90 deg.c during full-load operation of the cable, and determining I with heat path calculation formulaMAXThe size of (2).
4. The experimental method for evaluating the different water-entering and damp states of the power cable according to claim 1, wherein: in step S3, the water injection amount W is equal to the single maximum water inflow of the cable known from the local cable water inflow fault statistics.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113466607A (en) * | 2021-05-20 | 2021-10-01 | 深圳供电局有限公司 | Three-phase cable intermediate joint moisture state analysis method |
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Address after: 510640 No. five, 381 mountain road, Guangzhou, Guangdong, Tianhe District Applicant after: SOUTH CHINA University OF TECHNOLOGY Applicant after: Guangzhou Nanyang cable group Co.,Ltd. Address before: 510640 No. five, 381 mountain road, Guangzhou, Guangdong, Tianhe District Applicant before: SOUTH CHINA University OF TECHNOLOGY Applicant before: GUANGZHOU NANYANG CABLE Co.,Ltd. |
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