AU2020203291A1 - Method and system for detecting insulation aging degree of PPLP of superconducting cable - Google Patents
Method and system for detecting insulation aging degree of PPLP of superconducting cable Download PDFInfo
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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
- G01R27/08—Measuring resistance by measuring both voltage and current
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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
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
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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
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2688—Measuring quality factor or dielectric loss, e.g. loss angle, or power factor
- G01R27/2694—Measuring dielectric loss, e.g. loss angle, loss factor or power factor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
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- Measurement Of Resistance Or Impedance (AREA)
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Abstract
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(54) Title: DETECTION METHOD AND SYSTEM FOR PPLP INSULATION AGING DEGREE OF SUPERCONDUCTING CA
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S1 Apply excitation voltages of different frequencies on a sample, and calculate a
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S2 Acquire a detection result of the insulation aging degree of the sample according
to the dielectric loss angle tangent corresponding to the sample at different
frequencies
(57) Abstract: A detection method and system for insulation aging degree of superconducting cable. The detection method comprises:
applying excitation voltages of different frequencies on a sample, and calculating a dielectric loss angle tangent corresponding to the
sample at different frequencies by measuringthe voltage and current of the sample (S 1); and acquiring a detection result of the insulation
aging degree of the sample according to the dielectric loss angle tangent corresponding to the sample at different frequencies (S2).
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MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL,
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Description
The present application claims priority to a Chinese patent application No. 201910549193.9 filed with CNIPA on June 24, 2019, content of which is incorporated herein by reference in its entirety.
The present application relates to the technical field of power device insulation detection, for example, to a method and system for detecting insulation of a superconducting cable polypropylene laminated paper (PPLP) based on a dielectric spectrum.
o BACKGROUND
As the cutting-edge technology, high-temperature superconducting (HTS) cables have characteristics of high current, low loss and small volume. The transmission capacity of a HTS cable is 3 to 5 times that of a conventional cable, which can better meet the needs of power energy transmission and urban grid construction. However, little experience of test and operation related to the HTS cables has been obtained in domestic and foreign. This technology is overall in a stage of demonstration project and few commercial applications worldwide. There is no international standard for the test and operation related to the HTS cables. In 2013, a work report "recommended test for superconducting cables" of the CIGRE is completed by nine countries. However, there is no unified test standard released for HTS cables.
An insulation structure is an integral part of the HTS cables. At present, a mainstream insulation structure of the HTS cables is liquid nitrogen-impregnated polypropylene laminate paper (PPLP). PPLP is made by pressing a porous pulp material and a polypropylene film. The performance of PPLP is critical to the safe operation of the superconducting cables. PPLP works under operating voltage for a long time, and the insulation performance will gradually age and deteriorate. HTS cables are costly. Once insulation breakdown occurs due to aging of PPLP, the entire section of HTS cable will be damaged, resulting in huge economic losses, so the insulation aging degree of PPLP of the HTS cables needs to be detected and evaluated. Internationally, in existing HTS cable projects, the HTS cable insulation test is basically performed according to the test items of conventional cables, such as capacitance test and dielectric loss test. There is no relevant test for an insulation aging degree of PPLP.
The present application provides a method and system for detecting an insulation aging degree of PPLP of a superconducting cable.
The application may be implemented through a following technical solution: a method for detecting the insulation aging degree of the superconducting cable PPLP. The method includes following steps.
In Si, excitation voltages at different frequencies are applied to a test sample, and a complex capacitance of the test sample at different frequencies and a dielectric loss factor corresponding to the test sample at the different frequencies is calculated by measuring a voltage and a current of the test sample.
In S2, a result of detecting the insulation aging degree of the test sample is obtained according to a real part of the complex capacitance corresponding to the test sample at different frequencies and the dielectric loss factor corresponding to the test sample at the different frequencies.
In an embodiment, the step of calculating the dielectric loss factor corresponding to the test sample at different frequencies by measuring the voltage and current of the test sample includes: calculating a complex capacitance corresponding to the test sample at the different frequencies by measuring the voltage and the current of the test sample; and calculating the dielectric loss factor corresponding to the test sample at the different frequencies according to the complex capacitance corresponding to the test sample at the different frequencies.
In an embodiment, I(CO)= iC*(CO)U(CO), where o is an angular frequency, U(o) is a voltage of
the test sample at the frequency o, I(o) is a current of the test sample at the frequency o, and C*(o) is a complex capacitance.
tg 3= In an embodiment, C*(co) C'(co)- C'(w);where ;C(CO). C(o) is a real part of the complex capacitance and reflects an actual capacitance of a dielectric; C"(o) is an imaginary
part of the complex capacitance and reflects a loss of the dielectric; tgo is the dielectric loss
factor.
In an embodiment, the step of obtaining a result of detecting the insulation aging degree of the test sample according to the dielectric loss factor corresponding to the test sample at the different frequencies includes following steps.
A frequency characteristic curve of the dielectric loss factor and corresponding frequency values is drew.
The frequency characteristic curve is fitted and compared with multiple corresponding preset curves to obtain the result of detecting the insulation aging degree of the test sample.
In an embodiment, the result of detecting the insulation aging degree of the test sample is obtained by a following manner: traversing residuals of the frequency characteristic curve and the plurality of the preset curves, finding a smallest residual value and a second smallest residual value in the residuals, and determining a first preset curve corresponding to the smallest residual value and a second preset curve corresponding to the second smallest residual value; and performing an interpolation calculation on an aging degree corresponding to the first preset curve and an aging degree corresponding to the second preset curve by using a linear interpolation method to obtain the insulation aging degree of the test sample.
A system for detecting an insulation aging degree of a superconducting cable PPLP includes a controllable voltage source, a voltmeter, an ammeter, an industrial control computer and a test sample. An output end of the industrial control computer is connected to an input end of the controllable voltage source, and the industrial control computer is configured to control the controllable voltage source to output alternating voltages of different frequencies; the industrial control computer is configured to calculate a dielectric loss factor of the test sample based on a measured current and voltage of the test sample, and analyze an insulation aging degree of the test sample according to the dielectric loss factor. A first output end of the controllable voltage source is connected to a first end of the test sample to apply the alternating voltages of the different frequencies to the test sample, and a second output end of the controllable voltage source is grounded. A second end of the test sample is grounded through a first measurement end and a second measurement end of the ammeter in turn. An output end of the ammeter is connected to the industrial control computer, and the ammeter is configured to measure a current of the test sample and transmit the current of the test sample to the industrial computer. A first measurement end of the voltmeter is connected to a first output end of the controllable voltage source and the test sample, a second measurement end of the voltmeter is grounded, an output end of the voltmeter is connected to the industrial control computer, and the voltmeter is configured to measure a voltage of the test sample and transmit the voltage of the test sample to the industrial control computer.
In an embodiment, the industrial control computer includes a first calculation module, and the first calculation module is configured to calculate the dielectric loss factor.
In an embodiment, the industrial control computer includes a curve drawing module and a second calculation module. The curve drawing module is configured to draw a frequency characteristic curve of the dielectric loss factor and corresponding frequency values. The second calculation module is configured to fit and compare the frequency characteristic curve with multiple corresponding preset curves to obtain the result of detecting the insulation aging degree of the test sample.
In an embodiment, an output frequency range of the controllable voltage source is 0.0001 to 1000 Hz.
FIG. 1 is a schematic flowchart of an insulation detection method for PPLP of a superconducting cable according to the present application;
FIG. 2 is a schematic structural diagram of an insulation detection system for PPLP of a superconducting cable according to the present application.
Reference numbers in the drawings: 1. Controllable voltage source; 2. Voltmeter, 3. Ammeter; 4. Industrial control computer; 5. Test sample.
Hereinafter the present application will be described in detail in conjunction with the drawings and specific embodiments.
As shown in FIG. 1, a method for detecting PPLP insulation of a superconducting cable based on a dielectric spectrum includes steps Si and S2.
In Si, excitation voltages at different frequencies are applied to a test sample, and a dielectric loss factor of the test sample at the different frequencies is calculated by measuring a voltage and a current of the test sample.
In S2, a result of the insulation aging degree of the test sample is obtained according to the dielectric loss factor corresponding to the test sample at the different frequencies.
The step of calculating the dielectric loss factor corresponding to the test sample at different frequencies by measuring the voltage and current of the test sample includes: calculating a complex capacitance corresponding to the test sample at the different frequencies by measuring the voltage and the current of the test sample; and calculating the dielectric loss factor corresponding to the test sample at the different frequencies according to the complex capacitance corresponding to the test sample at the different frequencies.
The current, voltage, and complex capacitance in the above steps satisfy a following formula:
I(Co) = i C*(O) U(W), where o is an angular frequency, U(o) is a voltage of the test sample
at the frequency o, I(o) is a current of the test sample at the frequency o, and C*(o) is a complex capacitance.
C"(O) i (wtgd In the above step, C(w)= -' ; where C'(o) is a real part of the complex capacitance, which reflects an actual capacitance of a dielectric; C"(o) is an imaginary
part of the complex capacitance, which reflects dielectric loss; tgd is the dielectric loss factor.
After the dielectric loss factor data of the test sample is obtained by calculation, an insulation aging degree of the test sample is obtained by calculation according to drawing a frequency characteristic curve of the dielectric loss factor and corresponding frequency values and fitting and comparing the frequency characteristic curve with multiple corresponding preset curves.
In an embodiment, the result of detecting the insulation aging degree of the test sample is obtained by a following manner: traversing residuals of the frequency characteristic curve and the plurality of the preset curves, finding a smallest residual value and a second smallest residual value in the residuals, and determining a first preset curve corresponding to the smallest !5 residual value and a second preset curve corresponding to the second smallest residual value; and performing an interpolation calculation on an aging degree corresponding to the first preset curve and an aging degree corresponding to the second preset curve by using a linear interpolation method to obtain the insulation aging degree of the test sample.
Generally, the real part of the complex capacitance does not change much with frequency change, so an insulation aging degree is mainly determined based on the frequency characteristic curve of the dielectric loss factor.
A system for detecting an insulation aging degree of a superconducting cable, which uses the above method, has a structure as shown in FIG. 2. The system includes a controllable voltage source 1, a voltmeter 2, an ammeter 3, an industrial control computer 4 and a test sample 5. An output end of the industrial control computer 4 is connected to an input end of the controllable voltage source 1, and the industrial control computer 4 is configured to control the controllable voltage source 1 to output alternating voltages of different frequencies.
A first output end of the controllable voltage source 1 is connected to a first end of the test sample 5 to apply the alternating voltages of the different frequencies to the test sample 5, and a second output end of the controllable voltage source 1 is grounded.
A second end of the test sample 5 is grounded through a first measurement end and a second measurement end of the ammeter 3 in turn. An output end of the ammeter 3 is connected to the industrial control computer 4 and is configured to measure a current of the test sample 5 and transmit current data to the industrial control computer 4.
A first measurement end of the voltmeter 2 is connected to a first output end of the controllable voltage source 1 and a first end of the test sample 5, a second measurement end of the voltmeter 2 is grounded, an output end of the voltmeter 2 is connected to the industrial control computer 4, and the voltmeter 2 is configured to measure a voltage of the test sample 5 and transmit voltage data of the test sample 5 to the industrial control computer 4.
The industrial control computer 4 calculates the dielectric loss factor of the test sample 5 based on the measured current and voltage data, and analyzes the insulation aging degree of the test sample 5 according to the dielectric loss factor.
In an embodiment, the industrial control computer includes a first calculation module, and the first calculation module is configured to calculate the dielectric loss factor.
In an embodiment, the industrial control computer includes a curve drawing module and a second calculation module. The curve drawing module is configured to draw a frequency characteristic curve of the dielectric loss factor and corresponding frequency values. The second calculation module is configured to fit and compare the frequency characteristic curve with multiple corresponding preset curves to obtain the result of detecting the insulation aging degree of the test sample.
In an embodiment, an IDAX series automatic dielectric loss frequency characteristic tester IDAX-206 produced by a Swedish company Pax Diagnostics is used to perform the dielectric spectrum test of PPLP. The IDAX-206 can integrate the functions of the above-mentioned controllable voltage source, voltmeter and ammeter. The IDAX-206 has the characteristics of high degree of automation, simple test wiring and easy field implementation. A measuring o frequency range of IDAX-206 is 0.0001 to 1000 Hz.
The industrial control computer of the embodiment uses a software to calculate the complex capacitance and the dielectric loss factor of the test sample, and draws a frequency characteristic curve based on the calculated complex capacitance and the dielectric loss factor and the corresponding frequency values, and then performs comparative analysis according to an experience curve preset in the industrial control computer, or use a MODS analysis software supporting IDAX-206 to perform curve fitting, and the aging degree of the test sample may be calculated.
In practical applications, the method and system proposed in the application are used to perform PPLP insulation detection on a single-core HTS cable, a three-core HTS cable, and a three-phase coaxial HTS cables The wiring method is as follows.
I. Wiring of test on the single-core HTS cable
The high-voltage electrode of the dielectric spectrum tester is connected to a conductor of the HTS cable, and the low-voltage electrode and ground electrode are connected to a shielding layer of the HTS cable; the shielding layer at an opposite end of the cable is grounded, the conductor is suspended, and a dielectric spectrum of insulation between the conductor and the shielding layer is measured.
II. Wiring of test on the three-core HTS cable
A dielectric spectrum of the 3-phase cable may be measured separately, or a total dielectric spectrum may be measured for three phases at a same time.
1. Measurement of the dielectric spectrum of 3-phase cable separately
The method is the same as the method for measuring the dielectric spectrum of a single-core HTS cable. The dielectric spectrum of three single-core HTS cables is measured in turn. When one-phase cable is measured, the conductors and shielding layers of the other two non-test phases are grounded.
2. Measurement of the total dielectric spectrum of the three-phase cable
The three-phase conductor of the cable on the test side is short-circuited and connected to the high-voltage electrode of the dielectric spectrum tester; the three-phase shielding layer of the cable on the test side is short-circuited and connected to the low-voltage electrode and ground electrode of the dielectric spectrum tester; the three-phase cable conductor at an opposite end of the cable is suspended, and the three-phase cable shielding layer at an opposite end of the cable is grounded.
III. Wiring of test on the three-phase coaxial HTS cable
The three-phase coaxial structure is not used in conventional cables and only used in the HTS cables. The three-phase coaxial is designed in such a way that electrical parameters of the phases are different from each other. Therefore, the dielectric spectrum measurement should be performed separately for each phase. For the HTS three-phase coaxial cable, a first phase conductor, a second phase conductor, a third phase conductor, and the shielding layer are arranged in order from the inside to the outside. Therefore, the test may be performed in turn from inside to outside (the testing order may be reversed).
The first-phase conductor is connected to the high-voltage electrode of the dielectric spectrum tester, and the second-phase conductor, the third-phase conductor, and the shielding layer are short-circuited and connected to the low-voltage electrode and the ground electrode of the dielectric spectrum tester to measure the dielectric spectrum of insulation between the first-phase conductor and the second phase conductor.
Then, the first-phase conductor and the second-phase conductor are short-circuited and connected to the high-voltage electrode of the dielectric spectrum tester, the third phase and the shielding layer are short-circuited and connected to the low-voltage electrode and the ground electrode of the dielectric spectrum tester to measure the dielectric spectrum of insulation between the second-phase conductor and the third-phase conductor.
Finally, all three-phase conductors are short-circuited and connected to the high-voltage electrode of the dielectric spectrum tester, and the shielding layer is connected to the low-voltage electrode and the ground electrode of the dielectric spectrum tester to measure the dielectric spectrum of insulation between the third-phase conductor and the shielding layer.
The method for detecting PPLP insulation of a superconducting cable proposed in the application is to measure a dielectric complex capacitance, a dielectric loss factor and other characteristic parameters under excitation voltages of different frequencies, and then diagnose the whole insulation state by analyzing the change condition of the characteristic parameters in respective frequency bands. No matter the research on aging and dielectric spectrums of a PPLP insulation test piece and a short-section HTS cable is carried out in a laboratory, or the dielectric spectrum test of HTS cable systems with different running times is carried out on site, various mathematical tools may be used for analyzing data, and characteristic quantities may be extracted from measured curves. The following lists some of the dielectric spectrum curve characteristics parameters and analysis methods.
1. The parameters that may be analyzed include: variation curves of a dielectric loss factor, a real part of a complex capacitance and the like with frequency.
2. The changes of the parameter values before and after aging are observed in different frequency bands (low frequency, intermediate frequency and high frequency): values changes in the low and intermediate frequency are often sensitive to aging.
3. The shift in peak frequency of the curve before and after aging is observed: generally, the lower the peak frequency of the dielectric loss factor is, the more severe the aging is.
4. The slope of the curve is observed: the slope of the entire curve will change with aging. For the dielectric loss factor-frequency characteristic curve, the dielectric loss factor is large in the low frequency band and small in the high frequency band. At the same time, the curve shows an upward trend near the lowest frequency and the highest frequency.
5. An area enclosed by a measurement curve of a frequency domain dielectric spectrum in a specific frequency range (usually 0.01 to 1 Hz) is integrated, and a characteristic value that reflects an aging degree of an insulation material may be obtained.
6. Typical curve fitting method
6.1 An aging curve library is established, which includes: making a typical simplified model of PPLP insulation in a laboratory, performing electrical aging, performing a dielectric spectrum test on PPLP models in different aging states to obtain frequency domain characteristic curves in different aging states, and sorting the frequency domain characteristic curves into a database.
6.2 The dielectric spectrum of the HTS cable is tested on site to obtain the curve to be analyzed.
6.3 The database is searched for a curve closest to the curve to be analyzed, and the aging degree corresponding to this curve is taken as an aging degree of the curve to be analyzed. In an implementation process, residuals of the curve to be analyzed and curves in the database are o traversed and compared to obtain a minimum value, and then a linear interpolation method is used to calculate an aging degree of the corresponding curve to obtain the aging degree of the HTS cable on site.
In an embodiment, it is determined that a residual value of a curve Al in the database closest to a curve X to be analyzed is M, and the residual value of a second closest curve A2 is N. The
aging degree corresponding to the curve Al is al years, and the aging degree corresponding
to the curve A2 is a2 years, where al is less than a2. The linear interpolation method is
used to calculate the aging degree of the curve to be tested, which may be performed as follows:
M calculating an interpolation coefficient M +N between an aging period al and the aging
year a2 , and determining the aging degree corresponding to the curve to be tested
al+ M_(a2 - al) is M+N , that is, the aging period of the on-site HTS cable is
M al+ (a2 - al) M+N years.
With the method and system for detecting PPLP insulation of the superconducting cable proposed in the application, the embodiment uses PPLP to make a coaxial cylindrical sample, immerse the sample in liquid nitrogen, and apply a power frequency alternating voltage of 21kV. In 13 days, the total withstand voltage aging time was 46 hours, and the dielectric spectrum test is performed before and after the aging.
Table 1 shows data of the dielectric loss factor before and after aging. In general, the dielectric loss factor of PPLP insulation increases after aging, which is more obvious in the low frequency band. That is, after aging, the dielectric loss factor increases significantly at low and intermediate frequencies.
Table 1 Data of dielectric loss factor before and after aging
Frequency (Hz) tgc before aging tgc after aging
1000 0.0010844 0.001277 470 0.00098881 0.001386 220 0.0010046 0.001551 110 0.0013145 0.0018497 70 0.0012698 0.0019465 40 0.001274 0.0021195 20 0.001342 0.0023901 10 0.0016337 0.0027928 4.6416 0.0016419 0.0033028 2.1544 0.0015851 0.0041918 1 0.0016848 0.0058128 0.46416 0.0015133 0.0084952 0.21544 0.0014738 0.012435 0.1 0.0018195 0.015495 0.046416 0.0016663 0.013066 0.021544 0.0018875 0.016574 0.01 0.0028981 0.0195 0.004642 0.0049366 0.02575 0.002154 0.0091021 0.033464 0.001 0.024675 0.045641 Table 2 shows data of real and imaginary parts of the complex capacitance before and after aging. After aging, the real part of the complex capacitance of PPLP insulation is reduced to a certain extent in the entire frequency range. The imaginary part of the complex capacitance does o not change much in the high frequency band, and in the low and intermediate frequency band, it increases significantly after aging.
Table 2 Complex capacitance data before and after aging
Frequency Real part of Imaginary part Real part of Imaginary part complex of complex complex of complex capacitance C' capacitance C" capacitance C' capacitance C" before aging before aging after aging after aging 1000 4.3176E-10 4.6822E-13 2.8726E-10 3.6683E-13 470 4.3195E-10 4.2712E-13 2.8747E-10 3.9843E-13 220 4.3214E-10 4.3412E-13 2.8767E-10 4.4619E-13 110 4.3266E-10 5.6873E-13 2.8809E-10 5.329E-13 70 4.328E-10 5.4956E-13 2.8825E-10 5.6108E-13 40 4.3298E-10 5.5161E-13 2.8844E-10 6.1135E-13 20 4.3321E-10 5.8135E-13 2.8871E-10 6.9005E-13 10 4.3313E-10 7.0761E-13 2.888E-10 8.0656E-13 4.6416 4.3348E-10 7.1175E-13 2.8917E-10 9.5507E-13 2.1544 4.3385E-10 6.877E-13 2.8959E-10 1.2139E-12 1 4.3441E-10 7.3189E-13 2.903E-10 1.6875E-12 0.46416 4.347E-10 6.5785E-13 2.9104E-10 2.4724E-12 0.21544 4.3499E-10 6.4108E-13 2.9245E-10 3.6365E-12 0.1 4.3568E-10 7.927E-13 2.9484E-10 4.5686E-12 0.046416 4.3591E-10 7.2633E-13 2.9666E-10 3.8763E-12 0.021544 4.3629E-10 8.2349E-13 2.9911E-10 4.9576E-12 0.01 4.3466E-10 1.2597E-12 3.0032E-10 5.8565E-12 0.004642 4.3539E-10 2.1493E-12 3.0388E-10 7.8249E-12 0.002154 4.3599E-10 3.9684E-12 3.0862E-10 1.0328E-11 0.001 4.391E-10 1.0835E-11 3.1843E-10 1.4533E-11
Compared with related art, the application measures and calculates the complex capacitance and the dielectric loss factor of PPLP at different frequency points. By drawing the frequency curve and performing fitting comparison, the aging degree of the test sample can be evaluated, and the PPLP insulation performance can be tested comprehensively and effectively.
The application is based on the principle of dielectric spectrum, and adopts a detection method of applying alternating voltages of different frequencies to the dielectric PPLP, which can effectively obtain test data. By calculating and analyzing the relationship between the complex capacitance and corresponding frequency and the relationship between the dielectric loss factor and corresponding frequency, the application may obtain richer information than a traditional power frequency dielectric loss factor test, which helps to comprehensively and effectively test the PPLP insulation performance.
The application calculates the complex capacitance and the dielectric loss factor of the dielectric material at different frequencies. The calculation process is simple and reliable, and the analysis method of drawing the frequency curve and fitting and comparing the frequency curve may be used to obtain the aging degree of the test sample. Therefore, reliable data for the analysis of PPLP insulation detection of superconducting cables is provided.
Claims (10)
1. A method for detecting an insulation aging degree of polypropylene laminated paper (PPLP) of a superconducting cable, comprising:
applying excitation voltages at different frequencies to a test sample, and calculating a dielectric loss factor corresponding to the test sample at the different frequencies by measuring a voltage and a current of the test sample; and
obtaining a result of detecting the insulation aging degree of the test sample according to the dielectric loss factor corresponding to the test sample at the different frequencies.
2. The method of claim 1, wherein calculating the dielectric loss factor corresponding to the test sample at the different frequencies by measuring the voltage and current of the test sample comprises:
calculating a complex capacitance corresponding to the test sample at the different frequencies by measuring the voltage and the current of the test sample; and
calculating the dielectric loss factor corresponding to the test sample at the different frequencies according to the complex capacitance corresponding to the test sample at the different frequencies.
3. The method of claim 2, wherein the voltage, the current, and the complex capacitance satisfy a following formula:
I(CO) = iC*()U(o)
wherein, o is an angular frequency, U(o) is a voltage of the test sample at the frequency o, I(o) is a current of the test sample at the frequency o, and C*(o) is a complex capacitance.
4. The method of claim 3, wherein
C*(CO) = C'(CO) - iC"().
tg tg5=C"(C) 1 wherein C(o) is a real part of the complex capacitance and reflects an actual capacitance of a dielectric; C"(o) is an imaginary part of the complex capacitance and reflects a loss of the dielectric; tgo is the dielectric loss factor.
5. The method of claim 1, wherein obtaining the result of detecting the insulation aging degree of the test sample according to the dielectric loss factor corresponding to the test sample at the different frequencies comprises:
drawing a frequency characteristic curve of the dielectric loss factor and corresponding frequency values; and
fitting and comparing the frequency characteristic curve with a plurality of corresponding preset curves to obtain the result of detecting the insulation aging degree of the test sample.
6. The method of claim 5, wherein the result of detecting the insulation aging degree of the test sample is obtained in a following manner:
traversing residuals of the frequency characteristic curve and the plurality of the preset curves, finding a smallest residual value and a second smallest residual value in the residuals, and determining a first preset curve corresponding to the smallest residual value and a second preset curve corresponding to the second smallest residual value; and
performing an interpolation calculation on an aging degree corresponding to the first preset curve and an aging degree corresponding to the second preset curve by using a linear interpolation method to obtain the insulation aging degree of the test sample.
7. A system for detecting an insulation aging degree of polypropylene laminated paper (PPLP) of a superconducting cable, comprising: a controllable voltage source, a voltmeter, an ammeter, an industrial control computer and a test sample;
wherein an output end of the industrial control computer is connected to an input end of the controllable voltage source, and the industrial control computer is configured to control the controllable voltage source to output alternating voltages of different frequencies; the industrial control computer is configured to calculate a dielectric loss factor of the test sample based on a measured current and voltage of the test sample, and analyze an insulation aging degree of the test sample according to the dielectric loss factor;
a first output end of the controllable voltage source is connected to a first end of the test sample to apply the alternating voltages of the different frequencies to the test sample, and a second output end of the controllable voltage source is grounded; a second end of the test sample is grounded through a first measurement end and a second measurement end of the ammeter in turn; an output end of the ammeter is connected to the industrial control computer, and the ammeter is configured to measure a current of the test sample and transmit the current of the test sample to the industrial computer; and a first measurement end of the voltmeter is connected to a first output end of the controllable voltage source and the test sample, a second measurement end of the voltmeter is grounded, an output end of the voltmeter is connected to the industrial control computer, and the voltmeter is configured to measure a voltage of the test sample and transmit the voltage of the test sample to the industrial control computer.
8. The system of claim 7, wherein the industrial control computer comprises a first calculation module configured to calculate the dielectric loss factor.
9. The system of claim 7, wherein the industrial control computer comprises a curve drawing module and a second calculation module;
the curve drawing module is configured to draw a frequency characteristic curve of the dielectric loss factor and corresponding frequency values;
the second calculation module is configured to fit and compare the frequency characteristic curve with a plurality of corresponding preset curves to obtain the result of detecting the insulation aging degree of the test sample.
10. The system of claim 7, wherein an output frequency range of the controllable voltage source is 0.0001 to 1000 Hz.
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| PCT/CN2020/071086 WO2020258835A1 (en) | 2019-06-24 | 2020-01-09 | Detection method and system for pplp insulation aging degree of superconducting cable |
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| CN110618364A (en) * | 2019-11-03 | 2019-12-27 | 西南交通大学 | Method for evaluating insulation reliability of XLPE cable terminal of power distribution network |
| CN110658432B (en) * | 2019-11-03 | 2020-09-29 | 西南交通大学 | Method for evaluating moisture degree of cable terminal of power distribution network |
| GB2591439B (en) * | 2019-11-19 | 2023-11-01 | Viper Innovations Ltd | Cable insulation testing method |
| CN111239655B (en) * | 2020-01-17 | 2022-05-20 | 扬州大学 | Resonant frequency circuit structure for measuring superconducting characteristics of material |
| CN111736043A (en) * | 2020-06-19 | 2020-10-02 | 西安交通大学 | XLPE cable degassing state evaluation method based on low-frequency dielectric spectrum |
| CN112100809B (en) * | 2020-08-10 | 2022-06-14 | 华南理工大学 | Method for designing three-phase coaxial superconducting cable based on multi-physical field coupling simulation |
| CN113189443B (en) * | 2021-04-08 | 2022-03-22 | 广东工业大学 | Method for evaluating health state of high-voltage cable of motor train unit based on frequency domain complex dielectric constant |
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| CN113447537B (en) * | 2021-06-25 | 2023-05-05 | 海南电网有限责任公司电力科学研究院 | Method and device for measuring dielectric spectrum of oilpaper insulating frequency domain, storage medium and terminal |
| CN113391134B (en) * | 2021-07-07 | 2023-04-07 | 国家电网有限公司 | Cable defect judgment method |
| CN113671237A (en) * | 2021-08-17 | 2021-11-19 | 国网上海市电力公司 | Method for testing and evaluating handover of high-temperature superconducting cable |
| CN114184904B (en) * | 2021-11-05 | 2022-07-08 | 西南交通大学 | Method for evaluating insulation damage degree of ethylene propylene rubber cable of motor train unit |
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| CN114895151A (en) * | 2022-03-28 | 2022-08-12 | 国网上海市电力公司 | Superconducting cable temperature return process monitoring method based on dielectric mass spectrometry |
| CN114814376A (en) * | 2022-03-28 | 2022-07-29 | 国网上海市电力公司 | Dielectric loss and capacitance monitoring method for superconducting cable in temperature return process |
| CN114910703A (en) * | 2022-03-28 | 2022-08-16 | 国网上海市电力公司 | Dielectric spectrum-based monitoring method for precooling process of superconducting cable |
| CN114814375A (en) * | 2022-03-28 | 2022-07-29 | 国网上海市电力公司 | Dielectric loss and capacitance monitoring method in precooling process of superconducting cable |
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