CN116087717A - Submarine cable insulation aging evaluation method, submarine cable insulation aging evaluation device, submarine cable insulation aging evaluation equipment and storage medium - Google Patents
Submarine cable insulation aging evaluation method, submarine cable insulation aging evaluation device, submarine cable insulation aging evaluation equipment and storage medium Download PDFInfo
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Abstract
The invention provides a submarine cable insulation aging evaluation method, a submarine cable insulation aging evaluation device, submarine cable insulation aging evaluation equipment and a storage medium, wherein the submarine cable insulation aging evaluation method comprises the following steps: respectively obtaining polarization current of a polarization process and depolarization current of a depolarization process of the submarine cable to be tested under the first polarization voltage and the second polarization voltage; calculating the corresponding low-frequency dielectric loss factors under the first polarization voltage and the second polarization voltage applied to the submarine cable to be tested; acquiring low-frequency dielectric loss factor variation corresponding to the first polarization voltage and the second polarization voltage; and determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation. The invention can realize the high-efficiency diagnosis of the insulation aging state of the submarine cable, can more accurately reflect the insulation aging state of the submarine cable, and has higher sensitivity.
Description
Technical Field
The invention relates to the technical field of electric technology, in particular to a submarine cable insulation aging evaluation method, a submarine cable insulation aging evaluation device, submarine cable insulation aging evaluation equipment and a submarine cable storage medium.
Background
Under the combined action of many factors such as mechanical stress, moisture, temperature and electric field, the XLPE power cable leads to the gradual degradation of the insulation performance of the insulation body and accessories, which can lead to the reduction of the cable insulation margin, and under the action of impact voltage, the cable insulation breakdown can be caused, so that the power accident is caused. In order to monitor the insulation state of a cable, it is necessary to perform periodic insulation diagnosis on the cable.
The submarine power cable has thicker insulation thickness, higher rated voltage level and different structure from the medium-voltage cable, so that the traditional medium-voltage cable insulation diagnosis technology (such as insulation resistance and absorption ratio measurement, power frequency dielectric loss factor measurement, leakage current measurement and the like) has poor effect when applied to the submarine cable. Currently, there is no generally accepted method for insulation diagnosis of submarine cables. Various attempts have been made by students at home and abroad. Isothermal relaxation current methods have been used for insulation diagnosis of submarine cables, but require fitting analysis of isothermal relaxation current curves, and are complex and unreliable in practical operation. In addition, the learner proves that the low-frequency factor of the submarine cable has positive correlation with the insulation aging state of the submarine cable, but the research is tested by a broadband dielectric impedance spectrum tester, the test time is long, and the diagnosis efficiency is problematic.
Disclosure of Invention
The invention aims to provide a submarine cable insulation aging evaluation method, device, equipment and storage medium, so as to solve the technical problems, and effectively diagnose the insulation aging condition of a submarine cable in a short power cable off-line time without damaging the insulation property of the cable.
In order to solve the technical problems, the invention provides a submarine cable insulation aging evaluation method, which comprises the following steps:
acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of a submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process;
calculating a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested based on the first polarization current and the first depolarization current, and calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current;
acquiring low-frequency dielectric loss factor variation amounts corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor;
and determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation.
Further, the calculating, based on the first polarization current and the first depolarization current, a corresponding first low frequency dielectric loss factor at the first polarization voltage applied to the submarine cable to be tested, and based on the second polarization current and the second depolarization current, a corresponding second low frequency dielectric loss factor at the second polarization voltage applied to the submarine cable to be tested, includes:
calculating a first conductivity of cable insulation corresponding to the submarine cable to be tested under the first polarization voltage based on the first polarization current and the first depolarization current, and then calculating a first low-frequency dielectric loss factor corresponding to the submarine cable to be tested under the first polarization voltage based on the first conductivity;
and calculating a second conductivity of cable insulation corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current, and then calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second conductivity.
Further, the electrical conductivity of the cable insulation is calculated by the following formula:
in U 0 Epsilon for applying a polarization voltage to the cable core 0 Is vacuum dielectric constant, i pol (t final ) Representing a polarization current after a set time of applying a polarization voltage to the cable core; i.e depol (t final ) Represents the depolarization current of the cable after a set time in the depolarization process, C 0 Geometric capacitance for cable insulation, r s Is the inner radius of the cable shielding layer, r c Is the radius of the cable core.
Further, the corresponding low frequency dielectric loss factor at the applied polarization voltage to the submarine cable is calculated by the following formula:
in sigma 0 For cable insulation conductivity, epsilon 0 For vacuum dielectric constant, ε ∞ Is optical frequency dielectric constant, epsilon' (omega) is polarThe chemical strength, ε '(ω) is dielectric loss, χ' (ω) is the real part of the dielectric complex polarization χ (ω), χ "(ω) is the imaginary part of the dielectric complex polarization χ (ω).
Further, the repolarization rate χ (ω) of the insulating medium is calculated by the following formula:
wherein ω is an angular frequency; χ' is the real part of the complex polarization of the insulating medium, χ "is the imaginary part of the complex polarization of the insulating medium, f (t) is the medium response function, i pol To apply a polarization current to the cable core measured during polarization of the polarization voltage.
Further, the value range of the first polarization voltage is 1-4 kV, and the value range of the second polarization voltage is 3-6 kV.
Further, the difference between the second polarization voltage and the first polarization voltage is 2kV.
The invention also provides a submarine cable insulation aging evaluation device, which comprises:
the current acquisition module is used for acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of the submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process;
the factor calculation module is used for calculating a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested based on the first polarization current and the first depolarization current, and calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current;
a variation amount calculation module, configured to obtain a low-frequency dielectric loss factor variation amount corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor;
and the insulation aging evaluation module is used for determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation.
The invention also provides a terminal device comprising a processor and a memory storing a computer program, the processor implementing any one of the submarine cable insulation ageing assessment methods when executing the computer program.
The invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the submarine cable insulation degradation assessment method of any one of the above.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a submarine cable insulation aging evaluation method, a submarine cable insulation aging evaluation device, submarine cable insulation aging evaluation equipment and a storage medium, wherein the submarine cable insulation aging evaluation method comprises the following steps: acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of a submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process; calculating a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested based on the first polarization current and the first depolarization current, and calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current; acquiring low-frequency dielectric loss factor variation amounts corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor; and determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation. The invention can realize the high-efficiency diagnosis of the insulation aging state of the submarine cable, can more accurately reflect the insulation aging state of the submarine cable, and has higher sensitivity.
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FIG. 1 is a schematic flow chart of a submarine cable insulation aging assessment method provided by the invention;
FIG. 2 is a schematic diagram of the polarization-depolarization current test principle of the submarine cable provided by the invention;
FIG. 3 is a graph showing the low frequency dielectric loss factor tan delta of the new XLPE submarine cable and the sample XLPE submarine cable after heat aging according to the change curve of polarization voltage;
FIG. 4 is a graph showing the low frequency dielectric loss tangent tan delta and the low frequency dielectric loss tangent delta change delta tan delta of XLPE cable samples according to the invention along with aging time;
fig. 5 is a schematic structural view of the submarine cable insulation aging evaluation device provided by the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, an embodiment of the present invention provides a submarine cable insulation aging evaluation method, which may include the steps of:
s1, acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of a submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process;
s2, calculating a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested based on the first polarization current and the first depolarization current, and calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current;
s3, acquiring low-frequency dielectric loss factor variation corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor;
and S4, determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation.
Further, the calculating, based on the first polarization current and the first depolarization current, a corresponding first low frequency dielectric loss factor at the first polarization voltage applied to the submarine cable to be tested, and based on the second polarization current and the second depolarization current, a corresponding second low frequency dielectric loss factor at the second polarization voltage applied to the submarine cable to be tested, includes:
calculating a first conductivity of cable insulation corresponding to the submarine cable to be tested under the first polarization voltage based on the first polarization current and the first depolarization current, and then calculating a first low-frequency dielectric loss factor corresponding to the submarine cable to be tested under the first polarization voltage based on the first conductivity;
and calculating a second conductivity of cable insulation corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current, and then calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second conductivity.
Further, the electrical conductivity of the cable insulation is calculated by the following formula:
in U 0 Epsilon for applying a polarization voltage to the cable core 0 Is vacuum dielectric constant, i pol (t final ) Representing a polarization current after a set time of applying a polarization voltage to the cable core; i.e depol (t final ) Represents the depolarization current of the cable after a set time in the depolarization process, C 0 Geometric capacitance for cable insulation, r s Is the inner radius of the cable shielding layer, r c Is the radius of the cable core.
Further, the corresponding low frequency dielectric loss factor at the applied polarization voltage to the submarine cable is calculated by the following formula:
in sigma 0 For cable insulation conductivity, epsilon 0 For vacuum dielectric constant, ε ∞ The dielectric constant of the optical frequency is epsilon '(omega) the polarization intensity, epsilon' (omega) the dielectric loss, chi '(omega) the real part of the complex polarization rate chi (omega) of the insulating medium, and chi' (omega) the imaginary part of the complex polarization rate chi (omega) of the insulating medium.
Further, the repolarization rate χ (ω) of the insulating medium is calculated by the following formula:
wherein ω is an angular frequency; χ' is the real part of the complex polarization of the insulating medium, χ "is the imaginary part of the complex polarization of the insulating medium, f (t) is the medium response function, i pol To apply a polarization current to the cable core measured during polarization of the polarization voltage.
Further, the value range of the first polarization voltage is 1-4 kV, and the value range of the second polarization voltage is 3-6 kV.
Further, the difference between the second polarization voltage and the first polarization voltage is 2kV.
Based on the above scheme, in order to better understand the submarine cable insulation aging evaluation method provided by the embodiment of the invention, the following detailed description is provided:
it should be noted that, the idea of the embodiment of the invention is as follows: because the rated voltage level of the submarine cable is high, the capacitance is large, and the AC dielectric loss detection of the submarine cable is very difficult. The low frequency dielectric loss characteristics of the cable can also be obtained using polarization-depolarization amperometry at dc voltage. The research shows that the dielectric loss of the power cable may not be in positive correlation with the insulation aging degree, and the insulation aging condition of the cable is diagnosed simply according to the dielectric loss, so that the diagnosis effect is not ideal. However, the dielectric loss factors calculated by the aged power cable under different polarization voltages are different, and the variation of the dielectric loss factors and the aging time show positive correlation. Therefore, the dielectric loss factor variation obtained by PDC test under different polarization voltages can help to judge the insulation aging condition of the power cable.
Based on the inventive thought, the embodiment of the invention provides a 220kV XLPE submarine cable insulation aging evaluation method, which can be realized by the following steps:
s1, respectively measuring polarization current of a polarization process and depolarization current of a depolarization process of a submarine cable to be measured under a first polarization voltage and a second polarization voltage;
s2, calculating the corresponding low-frequency dielectric loss factors under the conditions of respectively applying a first polarization voltage and a second polarization voltage to the submarine cable according to the following formula:
in sigma 0 For cable insulation conductivity, epsilon 0 For vacuum dielectric constant, ε ∞ Is the optical frequency dielectric constant, epsilon' (omega) is the polarization intensity, epsilon "(omega) is the dielectric loss, χ' omega ' is the real part of the repolarization rate χ (omega) of the insulating medium, and χ ' (omega) is the imaginary part of the repolarization rate χ (omega) of the insulating medium;
s3, acquiring a low-frequency dielectric loss factor change delta tan delta corresponding to the first polarization voltage and the second polarization voltage, and taking the low-frequency dielectric loss factor change delta tan delta as a characteristic quantity delta tan delta for representing insulation aging of the submarine cable, wherein delta tan delta=tan delta 2 -tanδ 1 ，tanδ 1 、tanδ 2 Low frequency dielectric loss factors corresponding to the first polarization voltage and the second polarization voltage respectively;
and S4, evaluating the insulation aging degree of the submarine cable based on the characteristic quantity delta tan delta.
According to the 220kV XLPE submarine cable insulation aging evaluation method, the purpose of the step S1 is to measure the polarized current i in the polarization process of applying polarized voltage to the submarine cable to be tested and in the short-circuit grounding depolarization process after polarization is finished pol And depolarization current i depol 。
In order not to affect the insulativity of the submarine cable, the value range of the first polarization voltage applied to the submarine cable is 1-4 kV, and the value range of the second polarization voltage is 3-6 kV. Particularly, when the difference value between the second polarization voltage and the first polarization voltage is 2kV, the dielectric loss variation stability of the power cable under different voltages is better.
According to the 220kV XLPE submarine cable insulation aging evaluation method, the purpose of the step S2 is to obtain the low-frequency dielectric loss factors corresponding to the submarine cables when different voltages are applied.
Conductivity sigma due to submarine cable insulation 0 ：
In U 0 Epsilon for applying a polarization voltage to a submarine cable 0 Is trueDielectric constant of space, i pol (t final ) Representing the polarization current, i, after a set time of applying a polarization voltage to the submarine cable depol (t final ) Representing depolarization current of submarine cable after set time in depolarization process, C 0 Geometric capacitance of cable, r s Is the inner radius of the cable shielding layer, r c Is the radius of the cable core. The polarization and depolarization times are long enough to enable cable insulation diagnostics. The research shows that when the polarization taking time and the depolarization time are about 100s, the insulation diagnosis of the cable can be effectively completed, and in order to improve the diagnosis efficiency, the polarization time and the depolarization time are set to be 100s.
Then, the dielectric response function f (t) of the submarine cable insulation can be calculated through the conductivity of the submarine cable insulation:
i in pol To apply a polarization current measured during polarization of the polarization voltage to the submarine cable.
The invention assumes that the analyzed submarine cable insulating medium is linear, uniform and isotropic, and the complex polarization rate χ of the medium can be obtained after Fourier transformation is carried out by a medium response function f (t):
wherein: omega is the angular frequency; χ' is the real part of the repolarization rate of the insulating medium, which reflects the ability of the medium to bind charge; χ "is the imaginary part of the dielectric complex polarization, which reflects the polarization loss.
The frequency domain expression of the polarization current is:
wherein ε is the relative dielectric constant and U (ω) is the relative dielectric constant in the frequency domainThe applied sinusoidal excitation voltage, ε=ε '(ω) -jε "(ω), ε' (ω) =ε ∞ +χ' (ω) is the polarization intensity,
epsilon is the dielectric loss (including conductivity loss and polarization loss) ∞ Is the optical frequency dielectric constant.
Thus, by definition
The corresponding low-frequency dielectric loss factors when different polarization voltages are applied to the submarine cable can be calculated.
In the above 220kV XLPE submarine cable insulation aging evaluation method, in step S4, for a new unused cable, the low-frequency dielectric loss factor variation Δtan δ corresponding to the first polarization voltage and the second polarization voltage (i.e. the characteristic quantity characterizing cable insulation aging) is close to 0, and the characteristic quantity Δtan δ increases linearly with cable thermal aging. Therefore, the cable to be tested is subjected to the steps S1-S3 at regular time to obtain the characteristic quantity delta tan delta, and the insulation aging degree of the submarine cable to be tested can be evaluated according to the obtained characteristic quantity.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
1. according to the embodiment of the invention, firstly, the polarization current and the depolarization current of the submarine cable in the polarization process and the depolarization process are tested through the polarization-depolarization current (PDC), then, the low-frequency dielectric loss factor under the corresponding polarization voltage is obtained according to the obtained polarization current and depolarization current, and then, the variation quantity of the low-frequency dielectric loss factor under different polarization voltages is used as the characteristic quantity for representing the insulation aging of the cable, so that the insulation performance of the submarine cable is evaluated.
2. The low-frequency dielectric loss factor variable quantity under different polarization voltages has good test stability, can more accurately reflect the insulation aging state of the submarine cable, has high sensitivity, and has wide application prospect in the field of insulation aging diagnosis.
3. The voltage for testing the polarization-depolarization current (PDC) is lower, and the damage to cable insulation is smaller compared with partial discharge testing, voltage withstanding testing and the like.
The following examples are given to illustrate:
in the embodiment, 7 220kV XLPE 50cm submarine cable samples are selected for accelerated heat aging experiments, wherein 1 220kV XLPE 50cm short cable sample is used as a control, and the other cables are respectively subjected to accelerated heat aging for 10 days, 20 days, 30 days, 40 days, 50 days and 60 days. In addition, 1 220kV XLPE submarine cable which runs for 12 years is selected for verification experiments.
The accelerated thermal aging test of the short cable sample was performed using a constant temperature and humidity aging oven. The method comprises the following specific steps: and (3) placing the short cable sample into a constant temperature and humidity aging box, setting the temperature and humidity to be 130 ℃ and 0% respectively, and taking out the cable after continuously performing heat aging for corresponding aging days.
Subsequently, 1 new cable, 6 heat aged cables and 1 haul cable were subjected to polarization-depolarization current (PDC) test. The test schematic diagram is shown in fig. 2, the test device comprises a high-voltage direct-current power supply 1, a single-pole double-throw relay 2, a current limiting resistor 3, a picoammeter 4 and an upper computer 9, wherein one end of the high-voltage direct-current power supply 1 is connected with a contact a of the single-pole double-throw relay 2 through a wire, and the other end of the high-voltage direct-current power supply is grounded through the wire; the knife switch of the single-pole double-throw relay 2 is connected with one end of a current-limiting resistor 3 through a wire, the other end of the current-limiting resistor 3 is connected with a Pian meter 4, the other end of the Pian meter is connected with a cable core of a cable sample 7 through a wire, and a contact b of the single-pole double-throw relay 2 and a copper foil 6 of the cable sample 7 are grounded through wires; the high-voltage direct-current power supply 1 and the single-pole double-throw relay 2 are connected with the upper computer 9 through transmission lines, and the upper computer 9 controls the high-voltage direct-current power supply and the single-pole double-throw relay; the upper computer 9 is connected with the Pi-an meter 4 through Bluetooth, and collects the Pi-an meter data in real time.
The polarization-depolarization current testing process for the cable sample by adopting the testing device comprises the following steps: when the upper computer controls the single-pole double-throw relay to connect the knife switch to the contact a, the high voltage is used for straighteningThe power supply applies polarization voltages (1 kV, 2kV, 3kV, 4kV, 5kV and 6 kV) to the submarine cable sample for polarization, and the polarization time t is passed 1 After taking 100s in the embodiment, the single-pole double-throw relay is controlled to switch the knife to the contact b, the two ends of the insulating medium are grounded, the depolarization process is carried out through the discharge of the current-limiting resistor, and the depolarization duration time is t 2 (100 s is taken in this example). The peaches measure polarization and depolarization currents during polarization and depolarization, respectively.
According to the nyquist sampling theorem, the range of values of ω is related to the current signal sampling rate. In this embodiment, the sampling rate is 1Hz, so ω is up to 0.5Hz. Therefore, the present embodiment calculates the dielectric loss tangent at 0.1 Hz. The electrical conductivity sigma of the submarine cable insulation of the cable sample can be calculated by using the formulas (2) - (4) given above 0 The real part χ '(0.1 Hz) and the imaginary part χ' (0.1 Hz) of the complex polarization rate of the insulating medium, and then the dielectric loss factor tan delta at the frequency of 0.1Hz is calculated according to the formula (1) 0.1Hz 。
New cable at different polarization voltage and tan delta of cable after 5 days of thermal aging 0.1Hz The variation is shown in fig. 3. It is evident that the tan delta of the new cable 0.1Hz Is not changed with the change of polarization voltage. And the cable after heat aging has tan delta along with the rise of polarization voltage 0.1Hz And correspondingly increases. This is the theoretical basis of the invention with deltatan delta as the diagnostic criterion for ageing.
Then using the formula Δtan δ=tan δ 2 -tanδ 1 The dielectric loss tangent delta tan delta of the cable sample at different polarization voltages is calculated to evaluate the insulation aging state.
Table 1 shows the change in Deltatan delta for cable samples heat aged for 5 days at different polarization voltage differences. As can be seen from Table 1, when the polarization voltage difference is 2kV, the variance of the delta tan delta value is obviously smaller than that when the polarization voltage difference is 1kV and 3kV, namely the test result is stable. In addition, the polarization degree of the submarine cable insulation medium is possibly too low when the polarization voltage is too low, so that the test result is influenced; when the polarization voltage is too high, a small amount of space charge injection can be generated, and the effect is also influencedAnd (5) testing results. Therefore, the invention selects tan delta obtained by testing under 4kV and 2kV polarization voltage 0.1Hz The difference Δtan delta was further studied as a function of the aging time of the insulation.
TABLE 1 Low frequency (0.1 Hz) dielectric loss factor variation of 5 day aged cable samples at different polarization voltages
0.1Hz dielectric loss factor tan delta of cable sample at 2kV polarization voltage 0.1Hz And dielectric loss factor tan delta of 0.1Hz for cable samples at 4kV and 2kV polarization voltages 0.1Hz The difference Δtan delta as a function of cable insulation aging time is shown in fig. 4. The dielectric loss tangent tan delta and the variation delta tan delta of 0.1Hz of the new cable which is not subjected to aging treatment are close to 0. The 0.1Hz dielectric loss tangent tan delta of the cable sample does not have a positive correlation with the degree of insulation aging as the heat aging time increases. Whereas the 0.1Hz dielectric loss tangent delta tan delta of the cable samples showed a linear increase with increasing heat aging time. Therefore, the dielectric loss factor change delta tan delta of the submarine cable sample at the frequency of 0.1Hz can represent the characteristic quantity of cable insulation aging for judging the aging state of the cable insulation aging, and the diagnosis accuracy and the diagnosis efficiency are greatly improved.
Taking 1 220kV XLPE submarine cable which runs for 12 years as an example, the insulation aging state of the 220kV XLPE submarine cable is diagnosed by combining the insulation aging evaluation method for the 220kV XLPE submarine cable provided by the embodiment of the invention, and the method specifically comprises the following steps:
s1, respectively measuring polarization current of a submarine cable to be measured in a polarization process and depolarization current of the submarine cable to be measured in a depolarization process under 2kV and 4 kV; the polarization time and the depolarization time are respectively 100s;
s2, calculating the corresponding low-frequency dielectric loss factors under the conditions of applying a first polarization voltage and a second polarization voltage to the submarine cable according to the following formula:
in sigma 0 For cable insulation conductivity, epsilon 0 For vacuum dielectric constant, ε ∞ The dielectric constant of the optical frequency is epsilon '(omega) the polarization intensity, epsilon' (omega) the dielectric loss, chi '(omega) the real part of the complex polarization rate chi (omega) of the insulating medium, and chi' (omega) the imaginary part of the complex polarization rate chi (omega) of the insulating medium.
The electrical conductivity sigma of the submarine cable insulation can be calculated by using the formulas (2) - (4) given above 0 The real part χ '(0.1 Hz) and the imaginary part χ' (0.1 Hz) of the complex polarization rate of the insulating medium, and then the dielectric loss factor tan delta of 0.1Hz of the submarine cable is calculated according to the formula (1) 0.1Hz 。
Finally calculating to obtain tan delta 1 ＝tanδ 0.1Hz (2kV)＝3.9％，tanδ 2 ＝tanδ 0.1Hz (4kV)＝5.5％。
S3, obtaining a low-frequency dielectric loss factor change delta tan delta corresponding to the 2kV polarization voltage and the 4kV polarization voltage, and taking the low-frequency dielectric loss factor change delta tan delta as a characteristic quantity delta tan delta for representing the insulation aging of the submarine cable.
Δtanδ＝tanδ 2 –tanδ 1 ＝1.6％。
And S4, evaluating the insulation aging degree of the submarine cable based on the characteristic quantity delta tan delta.
From the previous analysis, it can be seen that the characteristic quantity Δtan δ increases linearly with thermal aging of the submarine power cable. Therefore, the cable to be tested is timed according to the steps S1-S3, the variation trend of the characteristic quantity delta tan delta can be obtained, and then the insulation aging degree of the submarine cable to be tested can be evaluated according to the obtained characteristic quantity.
For the 220kV XLPE submarine cable which runs for 12 years, the calculated characteristic quantity delta tan delta is only 1.6%, and the characteristic quantity delta tan delta is smaller, so that the problem of insulation ageing of the submarine cable is not great.
It should be noted that, for simplicity of description, the above method or flow embodiments are all described as a series of combinations of acts, but it should be understood by those skilled in the art that the embodiments of the present invention are not limited by the order of acts described, as some steps may occur in other orders or concurrently in accordance with the embodiments of the present invention. Further, those skilled in the art will appreciate that the embodiments described in the specification are all alternative embodiments and that the actions involved are not necessarily required for the embodiments of the present invention.
Referring to fig. 5, an embodiment of the present invention further provides a submarine cable insulation aging evaluation device, including:
the current acquisition module 1 is used for acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of the submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process;
a factor calculation module 2, configured to calculate, based on the first polarization current and the first depolarization current, a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested, and calculate, based on the second polarization current and the second depolarization current, a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested;
a variation calculation module 3, configured to obtain low-frequency dielectric loss factor variation amounts corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor;
and the insulation aging evaluation module 4 is used for determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation.
It can be understood that the embodiment of the device corresponds to the embodiment of the method of the invention, and the submarine cable insulation aging evaluation device provided by the embodiment of the invention can realize the submarine cable insulation aging evaluation method provided by any one of the embodiments of the method of the invention.
The invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the submarine cable insulation degradation assessment method of any one of the above.
It should be noted that the above-described apparatus embodiments are merely illustrative, and the units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the drawings of the embodiment of the device provided by the invention, the connection relation between the modules represents that the modules have communication connection, and can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
It will be clear to those skilled in the art that, for convenience and brevity, the specific working process of the apparatus described above may refer to the corresponding process in the foregoing method embodiment, which is not described herein again.
The terminal device may be a computing device such as a desktop computer, a notebook computer, a palm computer, a cloud server, etc. The terminal device may include, but is not limited to, a processor, a memory.
The processor may be a central processing unit (Central Processing Unit, CPU), other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like, which is a control center of the terminal device, and which connects various parts of the entire terminal device using various interfaces and lines.
The memory may be used to store the computer program, and the processor may implement various functions of the terminal device by running or executing the computer program stored in the memory and invoking data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function, and the like; the storage data area may store data created according to the use of the cellular phone, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, memory, plug-in hard disk, smart Media Card (SMC), secure Digital (SD) Card, flash Card (Flash Card), at least one disk storage device, flash memory device, or other volatile solid-state storage device.
The storage medium is a computer readable storage medium, and the computer program is stored in the computer readable storage medium, and when executed by a processor, the computer program can implement the steps of the above-mentioned method embodiments. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), an electrical carrier signal, a telecommunications signal, a software distribution medium, and so forth. It should be noted that the computer readable medium contains content that can be appropriately scaled according to the requirements of jurisdictions in which such content is subject to legislation and patent practice, such as in certain jurisdictions in which such content is subject to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.
Claims (10)
1. A submarine cable insulation degradation assessment method, comprising:
acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of a submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process;
calculating a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested based on the first polarization current and the first depolarization current, and calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current;
acquiring low-frequency dielectric loss factor variation amounts corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor;
and determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation.
2. The submarine cable insulation degradation assessment method according to claim 1, wherein the calculating, based on the first polarization current and the first depolarization current, a corresponding first low-frequency dielectric loss tangent at the first polarization voltage to the submarine cable under test, and the calculating, based on the second polarization current and the second depolarization current, a corresponding second low-frequency dielectric loss tangent at the second polarization voltage to the submarine cable under test, comprises:
calculating a first conductivity of cable insulation corresponding to the submarine cable to be tested under the first polarization voltage based on the first polarization current and the first depolarization current, and then calculating a first low-frequency dielectric loss factor corresponding to the submarine cable to be tested under the first polarization voltage based on the first conductivity;
and calculating a second conductivity of cable insulation corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current, and then calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second conductivity.
3. The submarine cable insulation degradation assessment method according to claim 2, wherein the electrical conductivity of the cable insulation is calculated by the following formula:
in U 0 Epsilon for applying a polarization voltage to the cable core 0 Is vacuum dielectric constant, i pol (t final ) Representing a polarization current after a set time of applying a polarization voltage to the cable core; i.e depol (t final ) Represents the depolarization current of the cable after a set time in the depolarization process, C 0 Geometric capacitance for cable insulation, r s Is the inner radius of the cable shielding layer, r c Is the radius of the cable core.
4. A submarine cable insulation degradation assessment method according to claim 3, wherein the corresponding low frequency dielectric loss factor for the submarine cable under application of the polarization voltage is calculated by the following formula:
in sigma 0 For cable insulation conductivity, epsilon 0 For vacuum dielectric constant, ε ∞ Is the dielectric constant of the optical frequency,ε '(ω) is the polarization, ε' (ω) is the dielectric loss, χ '(ω) is the real part of the dielectric repolarization ratio χ (ω), χ' (ω) is the imaginary part of the dielectric repolarization ratio χ (ω).
5. The submarine cable insulation degradation assessment method according to claim 4, wherein the insulation medium repolarization rate χ (ω) is calculated by the following formula:
wherein ω is an angular frequency; χ' is the real part of the complex polarization of the insulating medium, χ "is the imaginary part of the complex polarization of the insulating medium, f (t) is the medium response function, i pol To apply a polarization current to the cable core measured during polarization of the polarization voltage.
6. The submarine cable insulation aging assessment method according to claim 1, wherein the value range of the first polarization voltage is 1-4 kV, and the value range of the second polarization voltage is 3-6 kV.
7. The submarine cable insulation degradation assessment method according to claim 1, wherein the difference between the second polarization voltage and the first polarization voltage is 2kV.
8. A submarine cable insulation degradation evaluation device, characterized by comprising:
the current acquisition module is used for acquiring a first polarization current of a polarization process and a first depolarization current of a depolarization process of the submarine cable to be tested under a first polarization voltage, and acquiring a second polarization current of the submarine cable to be tested under a second polarization voltage and a second depolarization current of the depolarization process;
the factor calculation module is used for calculating a first low-frequency dielectric loss factor corresponding to the first polarization voltage applied to the submarine cable to be tested based on the first polarization current and the first depolarization current, and calculating a second low-frequency dielectric loss factor corresponding to the second polarization voltage applied to the submarine cable to be tested based on the second polarization current and the second depolarization current;
a variation amount calculation module, configured to obtain a low-frequency dielectric loss factor variation amount corresponding to the first polarization voltage and the second polarization voltage based on the first low-frequency dielectric loss factor and the second low-frequency dielectric loss factor;
and the insulation aging evaluation module is used for determining an insulation aging degree evaluation result of the submarine cable to be tested based on the low-frequency dielectric loss factor variation.
9. A terminal device comprising a processor and a memory storing a computer program, characterized in that the processor implements the submarine cable insulation degradation assessment method according to any one of claims 1 to 7 when executing the computer program.
10. A non-transitory computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when executed by a processor, implements the submarine cable insulation degradation assessment method according to any one of claims 1 to 7.
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| CN117554761A (en) * | 2023-11-20 | 2024-02-13 | 西南交通大学 | Evaluation method for XLPE cable insulation performance in severe cold environment |
| CN117825879A (en) * | 2023-11-20 | 2024-04-05 | 西南交通大学 | Evaluation method for insulation performance of power cable in acid-base environment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117554761A (en) * | 2023-11-20 | 2024-02-13 | 西南交通大学 | Evaluation method for XLPE cable insulation performance in severe cold environment |
| CN117825879A (en) * | 2023-11-20 | 2024-04-05 | 西南交通大学 | Evaluation method for insulation performance of power cable in acid-base environment |
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